WorldWideScience

Sample records for flip chip solder

  1. Development of gold based solder candidates for flip chip assembly

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Hattel, Jesper Henri

    2009-01-01

    Flip chip technology is now rapidly replacing the traditional wire bonding interconnection technology in the first level packaging applications due to the miniaturization drive in the microelectronics industry. Flip chip assembly currently involves the use of high lead containing solders...

  2. A flip chip process based on electroplated solder bumps

    Science.gov (United States)

    Salonen, J.; Salmi, J.

    1994-01-01

    Compared to wire bonding and TAB, flip chip technology using solder joints offers the highest pin count and packaging density and superior electrical performance. The chips are mounted upside down on the substrate, which can be made of silicon, ceramic, glass or - in some cases - even PCB. The extra processing steps required for chips are the deposition of a suitable thin film metal layer(s) on the standard Al pad and the formation of bumps. Also, the development of new fine line substrate technologies is required to utilize the full potential of the technology. In our bumping process, bump deposition is done by electroplating, which was chosen for its simplicity and economy. Sputter deposited molybdenum and copper are used as thin film layers between the aluminum pads and the solder bumps. A reason for this choice is that the metals can be selectively etched after bumping using the bumps as a mask, thus circumventing the need for a separate mask for etching the thin film metals. The bumps are electroplated from a binary Pb-Sn bath using a thick liquid photoresist. An extensively modified commercial flip chip bonder is used for alignment and bonding. Heat assisted tack bonding is used to attach the chips to the substrate, and final reflow joining is done without flux in a vacuum furnace.

  3. A review on solder reflow and flux application for flip chip

    Science.gov (United States)

    Suppiah, Sarveshvaran; Ong, Nestor Rubio; Sauli, Zaliman; Sarukunaselan, Karunavani; Alcain, Jesselyn Barro; Visvanathan, Susthitha Menon; Retnasamy, Vithyacharan

    2017-09-01

    This paper encompassed of the evolution and key findings, critical technical challenges, solutions and bonding equipment of solder reflow in flip chip bonding. Upon scrutinizing researches done by others, it can be deduced that peak temperature, time above liquidus, soak temperature, soak time, cooling rate and reflow environment played a vital role in achieving the desired bonding profile. In addition, flux is also needed with the purpose of removing oxides/contaminations on bump surface as well as to promote wetting of solder balls. Electromigration and warpage are the two main challenges faced by solder reflow process which can be overcome by the advancement in under bump metallization (UBM) and substrate technology. The review is ended with a brief description of the current equipment used in solder reflow process.

  4. Fluxless flip-chip bonding using a lead-free solder bumping technique

    Science.gov (United States)

    Hansen, K.; Kousar, S.; Pitzl, D.; Arab, S.

    2017-09-01

    With the LHC exceeding the nominal instantaneous luminosity, the current barrel pixel detector (BPIX) of the CMS experiment at CERN will reach its performance limits and undergo significant radiation damage. In order to improve detector performance in high luminosity conditions, the entire BPIX is replaced with an upgraded version containing an additional detection layer. Half of the modules comprising this additional layer are produced at DESY using fluxless and lead-free bumping and bonding techniques. Sequential solder-jetting technique is utilized to wet 40-μm SAC305 solder spheres on the silicon-sensor pads with electroless Ni, Pd and immersion Au (ENEPIG) under-bump metallization (UBM). The bumped sensors are flip-chip assembled with readout chips (ROCs) and then reflowed using a flux-less bonding facility. The challenges for jetting low solder volume have been analyzed and will be presented in this paper. An average speed of 3.4 balls per second is obtained to jet about 67 thousand solder balls on a single chip. On average, 7 modules have been produced per week. The bump-bond quality is evaluated in terms of electrical and mechanical properties. The peak-bump resistance is about 17.5 mΩ. The cross-section study revealed different types of intermetallic compounds (IMC) as a result of interfacial reactions between UBM and solder material. The effect of crystalline phases on the mechanical properties of the joint is discussed. The mean shear strength per bump after the final module reflow is about 16 cN. The results and sources of yield loss of module production are reported. The achieved yield is 95%.

  5. Advanced flip chip packaging

    CERN Document Server

    Lai, Yi-Shao; Wong, CP

    2013-01-01

    Advanced Flip Chip Packaging presents past, present and future advances and trends in areas such as substrate technology, material development, and assembly processes. Flip chip packaging is now in widespread use in computing, communications, consumer and automotive electronics, and the demand for flip chip technology is continuing to grow in order to meet the need for products that offer better performance, are smaller, and are environmentally sustainable. This book also: Offers broad-ranging chapters with a focus on IC-package-system integration Provides viewpoints from leading industry executives and experts Details state-of-the-art achievements in process technologies and scientific research Presents a clear development history and touches on trends in the industry while also discussing up-to-date technology information Advanced Flip Chip Packaging is an ideal book for engineers, researchers, and graduate students interested in the field of flip chip packaging.

  6. Soldering-induced Cu diffusion and intermetallic compound formation between Ni/Cu under bump metallization and SnPb flip-chip solder bumps

    Science.gov (United States)

    Huang, Chien-Sheng; Jang, Guh-Yaw; Duh, Jenq-Gong

    2004-04-01

    Nickel-based under bump metallization (UBM) has been widely used as a diffusion barrier to prevent the rapid reaction between the Cu conductor and Sn-based solders. In this study, joints with and without solder after heat treatments were employed to evaluate the diffusion behavior of Cu in the 63Sn-37Pb/Ni/Cu/Ti/Si3N4/Si multilayer structure. The atomic flux of Cu diffused through Ni was evaluated from the concentration profiles of Cu in solder joints. During reflow, the atomic flux of Cu was on the order of 1015-1016 atoms/cm2s. However, in the assembly without solder, no Cu was detected on the surface of Ni even after ten cycles of reflow. The diffusion behavior of Cu during heat treatments was studied, and the soldering-process-induced Cu diffusion through Ni metallization was characterized. In addition, the effect of Cu content in the solder near the solder/intermetallic compound (IMC) interface on interfacial reactions between the solder and the Ni/Cu UBM was also discussed. It is evident that the (Cu,Ni)6Sn5 IMC might form as the concentration of Cu in the Sn-Cu-Ni alloy exceeds 0.6 wt.%.

  7. Decapsulation Method for Flip Chips with Ceramics in Microelectronic Packaging

    Science.gov (United States)

    Shih, T. I.; Duh, J. G.

    2008-06-01

    The decapsulation of flip chips bonded to ceramic substrates is a challenging task in the packaging industry owing to the vulnerability of the chip surface during the process. In conventional methods, such as manual grinding and polishing, the solder bumps are easily damaged during the removal of underfill, and the thin chip may even be crushed due to mechanical stress. An efficient and reliable decapsulation method consisting of thermal and chemical processes was developed in this study. The surface quality of chips after solder removal is satisfactory for the existing solder rework procedure as well as for die-level failure analysis. The innovative processes included heat-sink and ceramic substrate removal, solder bump separation, and solder residue cleaning from the chip surface. In the last stage, particular temperatures were selected for the removal of eutectic Pb-Sn, high-lead, and lead-free solders considering their respective melting points.

  8. Estimate the thermomechanical fatigue life of two flip chip packages

    International Nuclear Information System (INIS)

    Pash, R.A.; Ullah, H.S.; Khan, M.Z.

    2005-01-01

    The continuing demand towards high density and low profile integrated circuit packaging has accelerated the development of flip chip structures as used in direct chip attach (DCA) technology, ball grid array (BOA) and chip scale package (CSP). In such structures the most widely used flip chip interconnects are solder joints. The reliability of flip chip structures largely depends on the reliability of solder joints. In this work solder joint fatigue life prediction for two chip scale packages is carried out. Elasto-plastic deformation behavior of the solder was simulated using ANSYS. Two dimensional plain strain finite element models were developed for each package to numerically compute the stress and total strain of the solder joints under temperature cycling. These stress and strain values are then used to predict the solder joint lifetime through modified Coffin Manson equation. The effect of solder joint's distance from edge of silicon die on life of the package is explored. The solder joint fatigue response is modeled for a typical temperature cycling of -60 to 140 degree C. (author)

  9. Tin-Silver Alloys for Flip-Chip Bonding Studied with a Rotating Cylinder Electrode

    DEFF Research Database (Denmark)

    Tang, Peter Torben; Pedersen, E.H.; Bech-Nielsen, G.

    1999-01-01

    Electrodeposition of solder for flip-chip bonding is studied in the form of a pyrophosphate/iodide tin-silver alloy bath. The objective is to obtain a uniform alloy composition, with 3.8 At.% silver, over a larger area. This specific alloy will provide an eutectic solder melting at 221°C (or 10°C...... photoresist, have shown a stable and promising alternative to pure tin and tin-lead alloys for flip-chip bonding applications....

  10. Application of electronic speckle-pattern interferometry to measure in-plane thermal displacement in flip-chip packages

    International Nuclear Information System (INIS)

    Lee, Baik-Woo; Jang, Woosoon; Kim, Dong-Won; Jeong, Jeung-hyun; Nah, Jae-Woong; Paik, Kyung-Wook; Kwon, Dongil

    2004-01-01

    Electronic speckle-pattern interferometry (ESPI) was applied for noncontact, real-time evaluation of thermal deformation in a flip-chip package. The spatial resolution of ESPI was increased to submicron scale by magnifying the areas studied in order to measure the deformation of such small-scale components as the solder in the flip-chip package. Thermal deformation in the horizontal and vertical directions around the solder joints was measured as two-dimensional mappings during heating from 25 to 125 deg. C. ESPI was successful in obtaining information on the complicated deformation field around the solder joints. Furthermore, the shear strain could also be calculated using the measured thermal deformation around each solder joint. The applicability of ESPI to flip-chip packages was verified by comparing the ESPI results with those of finite-element analysis (FEA)

  11. Characterization of Ni/SnPb-TiW/Pt Flip Chip Interconnections in Silicon Pixel Detector Modules

    CERN Document Server

    Karadzhinova, Aneliya; Härkönen, Jaakko; Luukka, Panja-riina; Mäenpää, Teppo; Tuominen, Eija; Haeggstrom, Edward; Kalliopuska, Juha; Vahanen, Sami; Kassamakov, Ivan

    2014-01-01

    In contemporary high energy physics experiments, silicon detectors are essential for recording the trajectory of new particles generated by multiple simultaneous collisions. Modern particle tracking systems may feature 100 million channels, or pixels, which need to be individually connected to read-out chains. Silicon pixel detectors are typically connected to readout chips by flip-chip bonding using solder bumps. High-quality electro-mechanical flip-chip interconnects minimizes the number of dead read-out channels in the particle tracking system. Furthermore, the detector modules must endure handling during installation and withstand heat generation and cooling during operation. Silicon pixel detector modules were constructed by flip-chip bonding 16 readout chips to a single sensor. Eutectic SnPb solder bumps were deposited on the readout chips and the sensor chips were coated with TiW/Pt thin film UBM (under bump metallization). The modules were assembled at Advacam Ltd, Finland. We studied the uniformity o...

  12. An analysis of the pull strength behaviors of fine-pitch, flip chip solder interconnections using a Au-Pt-Pd thick film conductor on Low-Temperature, Co-fired Ceramic (LTCC) substrates

    International Nuclear Information System (INIS)

    Uribe, Fernando R.; Kilgo, Alice C.; Grazier, John Mark; Vianco, Paul Thomas; Zender, Gary L.; Hlava, Paul Frank; Rejent, Jerome Andrew

    2008-01-01

    The assembly of the BDYE detector requires the attachment of sixteen silicon (Si) processor dice (eight on the top side; eight on the bottom side) onto a low-temperature, co-fired ceramic (LTCC) substrate using 63Sn-37Pb (wt.%, Sn-Pb) in a double-reflow soldering process (nitrogen). There are 132 solder joints per die. The bond pads were gold-platinum-palladium (71Au-26Pt-3Pd, wt.%) thick film layers fired onto the LTCC in a post-process sequence. The pull strength and failure modes provided the quality metrics for the Sn-Pb solder joints. Pull strengths were measured in both the as-fabricated condition and after exposure to thermal cycling (-55/125 C; 15 min hold times; 20 cycles). Extremely low pull strengths--referred to as the low pull strength phenomenon--were observed intermittently throughout the product build, resulting in added program costs, schedule delays, and a long-term reliability concern for the detector. There was no statistically significant correlation between the low pull strength phenomenon and (1) the LTCC 'sub-floor' lot; (2) grit blasting the LTCC surfaces prior to the post-process steps; (3) the post-process parameters; (4) the conductor pad height (thickness); (5) the dice soldering assembly sequence; or (5) the dice pull test sequence. Formation of an intermetallic compound (IMC)/LTCC interface caused by thick film consumption during either the soldering process or by solid-state IMC formation was not directly responsible for the low-strength phenomenon. Metallographic cross sections of solder joints from dice that exhibited the low pull strength behavior, revealed the presence of a reaction layer resulting from an interaction between Sn from the molten Sn-Pb and the glassy phase at the TKN/LTCC interface. The thick film porosity did not contribute, explicitly, to the occurrence of reaction layer. Rather, the process of printing the very thin conductor pads was too sensitive to minor thixotropic changes to ink, which resulted in

  13. An analysis of the pull strength behaviors of fine-pitch, flip chip solder interconnections using a Au-Pt-Pd thick film conductor on Low-Temperature, Co-fired Ceramic (LTCC) substrates.

    Energy Technology Data Exchange (ETDEWEB)

    Uribe, Fernando R.; Kilgo, Alice C.; Grazier, John Mark; Vianco, Paul Thomas; Zender, Gary L.; Hlava, Paul Frank; Rejent, Jerome Andrew

    2008-09-01

    The assembly of the BDYE detector requires the attachment of sixteen silicon (Si) processor dice (eight on the top side; eight on the bottom side) onto a low-temperature, co-fired ceramic (LTCC) substrate using 63Sn-37Pb (wt.%, Sn-Pb) in a double-reflow soldering process (nitrogen). There are 132 solder joints per die. The bond pads were gold-platinum-palladium (71Au-26Pt-3Pd, wt.%) thick film layers fired onto the LTCC in a post-process sequence. The pull strength and failure modes provided the quality metrics for the Sn-Pb solder joints. Pull strengths were measured in both the as-fabricated condition and after exposure to thermal cycling (-55/125 C; 15 min hold times; 20 cycles). Extremely low pull strengths--referred to as the low pull strength phenomenon--were observed intermittently throughout the product build, resulting in added program costs, schedule delays, and a long-term reliability concern for the detector. There was no statistically significant correlation between the low pull strength phenomenon and (1) the LTCC 'sub-floor' lot; (2) grit blasting the LTCC surfaces prior to the post-process steps; (3) the post-process parameters; (4) the conductor pad height (thickness); (5) the dice soldering assembly sequence; or (5) the dice pull test sequence. Formation of an intermetallic compound (IMC)/LTCC interface caused by thick film consumption during either the soldering process or by solid-state IMC formation was not directly responsible for the low-strength phenomenon. Metallographic cross sections of solder joints from dice that exhibited the low pull strength behavior, revealed the presence of a reaction layer resulting from an interaction between Sn from the molten Sn-Pb and the glassy phase at the TKN/LTCC interface. The thick film porosity did not contribute, explicitly, to the occurrence of reaction layer. Rather, the process of printing the very thin conductor pads was too sensitive to minor thixotropic changes to ink, which resulted in

  14. A two-dimensional simulation model for the molded underfill process in flip chip packaging

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xue Ru; Young, Wen Bin [National Cheng Kung University, Tainan (China)

    2015-07-15

    The flip chip process involves the deposition of solder bumps on the chip surface and their subsequent direct attachment and connection to a substrate. Underfilling traditional flip chip packaging is typically performed following a two-step approach. The first step uses capillary force to fill the gap between the chip and the substrate, and the second step uses epoxy molding compound (EMC) to overmold the package. Unlike traditional flip chip packaging, the molded underfill (MUF) concept uses a single-step approach to simultaneously achieve both underfill and overmold. MUF is a simpler and faster process. In this study, a 2D numerical model is developed to simulate the front movement of EMC flow and the void formation for different geometric parameters. The 2D model simplifies the procedures of geometric modeling and reduces the modeling time for the MUF simulation. Experiments are conducted to verify the prediction results of the model. The effect on void formation for different geometric parameters is investigated using a 2D model.

  15. Rework of flip chip bonded radiation pixel detectors

    International Nuclear Information System (INIS)

    Vaehaenen, S.; Heikkinen, H.; Pohjonen, H.; Salonen, J.; Savolainen-Pulli, S.

    2008-01-01

    In this paper, some practical aspects of reworking flip chip hybridized pixel detectors are discussed. As flip chip technology has been advancing in terms of placement accuracy and reliability, large-area hybrid pixel detectors have been developed. The area requirements are usually fulfilled by placing several readout chips (ROCs) on single sensor chip. However, as the number of ROCs increases, the probability of failure in the hybridization process and the ROC operation also increases. Because high accuracy flip chip bonding takes time, a significant part of the price of a pixel detector comes from the flip chip assembly process itself. As large-area detector substrates are expensive, and many flip chip placements are required, the price of an assembled detector can become very high. In a typical case, there is just one bad ROC (out of several) on a faulty detector to be replaced. Considering the high price of pixel detectors and the fact that reworking faulty ROCs does not take much longer than the original placement, it is worthwhile to investigate the feasibility of a rework process

  16. Rework of flip chip bonded radiation pixel detectors

    Energy Technology Data Exchange (ETDEWEB)

    Vaehaenen, S. [VTT MEMS and Micropackaging, Espoo 02150 (Finland)], E-mail: sami.vahanen@vtt.fi; Heikkinen, H.; Pohjonen, H.; Salonen, J.; Savolainen-Pulli, S. [VTT MEMS and Micropackaging, Espoo 02150 (Finland)

    2008-06-11

    In this paper, some practical aspects of reworking flip chip hybridized pixel detectors are discussed. As flip chip technology has been advancing in terms of placement accuracy and reliability, large-area hybrid pixel detectors have been developed. The area requirements are usually fulfilled by placing several readout chips (ROCs) on single sensor chip. However, as the number of ROCs increases, the probability of failure in the hybridization process and the ROC operation also increases. Because high accuracy flip chip bonding takes time, a significant part of the price of a pixel detector comes from the flip chip assembly process itself. As large-area detector substrates are expensive, and many flip chip placements are required, the price of an assembled detector can become very high. In a typical case, there is just one bad ROC (out of several) on a faulty detector to be replaced. Considering the high price of pixel detectors and the fact that reworking faulty ROCs does not take much longer than the original placement, it is worthwhile to investigate the feasibility of a rework process.

  17. Flip chip assembly of thinned chips for hybrid pixel detector applications

    International Nuclear Information System (INIS)

    Fritzsch, T; Zoschke, K; Rothermund, M; Oppermann, H; Woehrmann, M; Ehrmann, O; Lang, K D; Huegging, F

    2014-01-01

    There is a steady trend to ultra-thin microelectronic devices. Especially for future particle detector systems a reduced readout chip thickness is required to limit the loss of tracking precision due to scattering. The reduction of silicon thickness is performed at wafer level in a two-step thinning process. To minimize the risk of wafer breakage the thinned wafer needs to be handled by a carrier during the whole process chain of wafer bumping. Another key process is the flip chip assembly of thinned readout chips onto thin sensor tiles. Besides the prevention of silicon breakage the minimization of chip warpage is one additional task for a high yield and reliable flip chip process. A new technology using glass carrier wafer will be described in detail. The main advantage of this technology is the combination of a carrier support during wafer processing and the chip support during flip chip assembly. For that a glass wafer is glue-bonded onto the backside of the thinned readout chip wafer. After the bump deposition process the glass-readout chip stack is diced in one step. Finally the glass carrier chip is released by laser illumination after flip chip assembly of the readout chip onto sensor tile. The results of the flip chip assembly process development for the ATLAS IBL upgrade are described more in detail. The new ATLAS FEI4B chip with a size of 20 × 19 mm 2 is flip chip bonded with a thickness of only 150 μm, but the capability of this technology has been demonstrated on hybrid modules with a reduced readout chip thickness of down to 50 μm which is a major step for ultra-thin electronic systems

  18. Physics-based process modeling, reliability prediction, and design guidelines for flip-chip devices

    Science.gov (United States)

    Michaelides, Stylianos

    Flip Chip on Board (FCOB) and Chip-Scale Packages (CSPs) are relatively new technologies that are being increasingly used in the electronic packaging industry. Compared to the more widely used face-up wirebonding and TAB technologies, flip-chips and most CSPs provide the shortest possible leads, lower inductance, higher frequency, better noise control, higher density, greater input/output (I/O), smaller device footprint and lower profile. However, due to the short history and due to the introduction of several new electronic materials, designs, and processing conditions, very limited work has been done to understand the role of material, geometry, and processing parameters on the reliability of flip-chip devices. Also, with the ever-increasing complexity of semiconductor packages and with the continued reduction in time to market, it is too costly to wait until the later stages of design and testing to discover that the reliability is not satisfactory. The objective of the research is to develop integrated process-reliability models that will take into consideration the mechanics of assembly processes to be able to determine the reliability of face-down devices under thermal cycling and long-term temperature dwelling. The models incorporate the time and temperature-dependent constitutive behavior of various materials in the assembly to be able to predict failure modes such as die cracking and solder cracking. In addition, the models account for process-induced defects and macro-micro features of the assembly. Creep-fatigue and continuum-damage mechanics models for the solder interconnects and fracture-mechanics models for the die have been used to determine the reliability of the devices. The results predicted by the models have been successfully validated against experimental data. The validated models have been used to develop qualification and test procedures for implantable medical devices. In addition, the research has helped develop innovative face

  19. Identifying Professional Competencies of the Flip-Chip Packaging Engineer in Taiwan

    Science.gov (United States)

    Guu, Y. H.; Lin, Kuen-Yi; Lee, Lung-Sheng

    2014-01-01

    This study employed a literature review, expert interviews, and a questionnaire survey to construct a set of two-tier competencies for a flip-chip packaging engineer. The fuzzy Delphi questionnaire was sent to 12 flip-chip engineering experts to identify professional competencies that a flip-chip packaging engineer must have. Four competencies,…

  20. Development of n+-in-p planar pixel quadsensor flip-chipped with FE-I4 readout ASICs

    International Nuclear Information System (INIS)

    Unno, Y.; Hanagaki, K.; Hori, R.; Ikegami, Y.; Nakamura, K.; Takubo, Y.; Kamada, S.; Yamamura, K.; Yamamoto, H.; Takashima, R.; Tojo, J.; Kono, T.; Nagai, R.; Saito, S.; Sugibayashi, K.; Hirose, M.; Jinnouchi, O.; Sato, S.; Sawai, H.; Hara, K.

    2017-01-01

    We have developed flip-chip modules applicable to the pixel detector for the HL-LHC. New radiation-tolerant n + -in-p planar pixel sensors of a size of four FE-I4 application-specific integrated circuits (ASICs) are laid out in a 6-in wafer. Variation in readout connection for the pixels at the boundary of ASICs is implemented in the design of quadsensors. Bump bonding technology is developed for four ASICs onto one quadsensor. Both sensors and ASICs are thinned to 150 μm before bump bonding, and are held flat with vacuum chucks. Using lead-free SnAg solder bumps, we encounter deficiency with large areas of disconnected bumps after thermal stress treatment, including irradiation. Surface oxidation of the solder bumps is identified as a critical source of this deficiency after bump bonding trials, using SnAg bumps with solder flux, indium bumps, and SnAg bumps with a newly-introduced hydrogen-reflow process. With hydrogen-reflow, we establish flux-less bump bonding technology with SnAg bumps, appropriate for mass production of the flip-chip modules with thin sensors and thin ASICs.

  1. Numerical Analysis of Warpage Induced by Thermo-Compression Bonding Process of Cu Pillar Bump Flip Chip Package

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Oh Young; Jung, Hoon Sun; Lee, Jung Hoon; Choa, Sung-Hoon [Seoul Nat’l Univ. of Science and Technology, Seoul (Korea, Republic of)

    2017-06-15

    In flip chip technology, the conventional solder bump has been replaced with a copper (Cu) pillar bump owing to its higher input/output (I/O) density, finer pitch, and higher reliability. However, Cu pillar bump technology faces several issues, such as interconnect shorting and higher low-k stress due to stiffer Cu pillar structure when the conventional reflow process is used. Therefore, the thermal compression bonding (TCB) process has been adopted in the flip chip attachment process in order to reduce the package warpage and stress. In this study, we investigated the package warpage induced during the TCB process using a numerical analysis. The warpage of the TCB process was compared with that of the reflow process.

  2. High-sensitivity low-noise miniature fluxgate magnetometers using a flip chip conceptual design.

    Science.gov (United States)

    Lu, Chih-Cheng; Huang, Jeff; Chiu, Po-Kai; Chiu, Shih-Liang; Jeng, Jen-Tzong

    2014-07-30

    This paper presents a novel class of miniature fluxgate magnetometers fabricated on a print circuit board (PCB) substrate and electrically connected to each other similar to the current "flip chip" concept in semiconductor package. This sensor is soldered together by reversely flipping a 5 cm × 3 cm PCB substrate to the other identical one which includes dual magnetic cores, planar pick-up coils, and 3-D excitation coils constructed by planar Cu interconnections patterned on PCB substrates. Principles and analysis of the fluxgate sensor are introduced first, and followed by FEA electromagnetic modeling and simulation for the proposed sensor. Comprehensive characteristic experiments of the miniature fluxgate device exhibit favorable results in terms of sensitivity (or "responsivity" for magnetometers) and field noise spectrum. The sensor is driven and characterized by employing the improved second-harmonic detection technique that enables linear V-B correlation and responsivity verification. In addition, the double magnitude of responsivity measured under very low frequency (1 Hz) magnetic fields is experimentally demonstrated. As a result, the maximum responsivity of 593 V/T occurs at 50 kHz of excitation frequency with the second harmonic wave of excitation; however, the minimum magnetic field noise is found to be 0.05 nT/Hz(1/2) at 1 Hz under the same excitation. In comparison with other miniature planar fluxgates published to date, the fluxgate magnetic sensor with flip chip configuration offers advances in both device functionality and fabrication simplicity. More importantly, the novel design can be further extended to a silicon-based micro-fluxgate chip manufactured by emerging CMOS-MEMS technologies, thus enriching its potential range of applications in modern engineering and the consumer electronics market.

  3. Study of silicon chip soldering in high-power transistor housing

    Directory of Open Access Journals (Sweden)

    Vasily S. Anosov

    2017-09-01

    We experimentally assessed the effect of outer housing layer materials and back side chip metallization. For lead-silver soldering of silicon chips, the best housing is that with a nickel outer layer rather than with a gold-plated one, because the resultant thermal resistance is lower and the absence of gold makes the technology cheaper. We obtained a 0.6 K/W thermal resistance for a 24 mm2 chip area.

  4. Flip chip assembly of thinned chips for hybrid pixel detector applications

    CERN Document Server

    Fritzsch, T; Woehrmann, M; Rothermund, M; Huegging, F; Ehrmann, O; Oppermann, H; Lang, K.D

    2014-01-01

    There is a steady trend to ultra-thin microelectronic devices. Especially for future particle detector systems a reduced readout chip thickness is required to limit the loss of tracking precision due to scattering. The reduction of silicon thickness is performed at wafer level in a two-step thinning process. To minimize the risk of wafer breakage the thinned wafer needs to be handled by a carrier during the whole process chain of wafer bumping. Another key process is the flip chip assembly of thinned readout chips onto thin sensor tiles. Besides the prevention of silicon breakage the minimization of chip warpage is one additional task for a high yield and reliable flip chip process. A new technology using glass carrier wafer will be described in detail. The main advantage of this technology is the combination of a carrier support during wafer processing and the chip support during flip chip assembly. For that a glass wafer is glue-bonded onto the backside of the thinned readout chip wafer. After the bump depo...

  5. High-Sensitivity Low-Noise Miniature Fluxgate Magnetometers Using a Flip Chip Conceptual Design

    Directory of Open Access Journals (Sweden)

    Chih-Cheng Lu

    2014-07-01

    Full Text Available This paper presents a novel class of miniature fluxgate magnetometers fabricated on a print circuit board (PCB substrate and electrically connected to each other similar to the current “flip chip” concept in semiconductor package. This sensor is soldered together by reversely flipping a 5 cm × 3 cm PCB substrate to the other identical one which includes dual magnetic cores, planar pick-up coils, and 3-D excitation coils constructed by planar Cu interconnections patterned on PCB substrates. Principles and analysis of the fluxgate sensor are introduced first, and followed by FEA electromagnetic modeling and simulation for the proposed sensor. Comprehensive characteristic experiments of the miniature fluxgate device exhibit favorable results in terms of sensitivity (or “responsivity” for magnetometers and field noise spectrum. The sensor is driven and characterized by employing the improved second-harmonic detection technique that enables linear V-B correlation and responsivity verification. In addition, the double magnitude of responsivity measured under very low frequency (1 Hz magnetic fields is experimentally demonstrated. As a result, the maximum responsivity of 593 V/T occurs at 50 kHz of excitation frequency with the second harmonic wave of excitation; however, the minimum magnetic field noise is found to be 0.05 nT/Hz1/2 at 1 Hz under the same excitation. In comparison with other miniature planar fluxgates published to date, the fluxgate magnetic sensor with flip chip configuration offers advances in both device functionality and fabrication simplicity. More importantly, the novel design can be further extended to a silicon-based micro-fluxgate chip manufactured by emerging CMOS-MEMS technologies, thus enriching its potential range of applications in modern engineering and the consumer electronics market.

  6. High-Sensitivity Low-Noise Miniature Fluxgate Magnetometers Using a Flip Chip Conceptual Design

    Science.gov (United States)

    Lu, Chih-Cheng; Huang, Jeff; Chiu, Po-Kai; Chiu, Shih-Liang; Jeng, Jen-Tzong

    2014-01-01

    This paper presents a novel class of miniature fluxgate magnetometers fabricated on a print circuit board (PCB) substrate and electrically connected to each other similar to the current “flip chip” concept in semiconductor package. This sensor is soldered together by reversely flipping a 5 cm × 3 cm PCB substrate to the other identical one which includes dual magnetic cores, planar pick-up coils, and 3-D excitation coils constructed by planar Cu interconnections patterned on PCB substrates. Principles and analysis of the fluxgate sensor are introduced first, and followed by FEA electromagnetic modeling and simulation for the proposed sensor. Comprehensive characteristic experiments of the miniature fluxgate device exhibit favorable results in terms of sensitivity (or “responsivity” for magnetometers) and field noise spectrum. The sensor is driven and characterized by employing the improved second-harmonic detection technique that enables linear V-B correlation and responsivity verification. In addition, the double magnitude of responsivity measured under very low frequency (1 Hz) magnetic fields is experimentally demonstrated. As a result, the maximum responsivity of 593 V/T occurs at 50 kHz of excitation frequency with the second harmonic wave of excitation; however, the minimum magnetic field noise is found to be 0.05 nT/Hz1/2 at 1 Hz under the same excitation. In comparison with other miniature planar fluxgates published to date, the fluxgate magnetic sensor with flip chip configuration offers advances in both device functionality and fabrication simplicity. More importantly, the novel design can be further extended to a silicon-based micro-fluxgate chip manufactured by emerging CMOS-MEMS technologies, thus enriching its potential range of applications in modern engineering and the consumer electronics market. PMID:25196107

  7. High-Sensitivity Low-Noise Miniature Fluxgate Magnetometers Using a Flip Chip Conceptual Design

    OpenAIRE

    Lu, Chih-Cheng; Huang, Jeff; Chiu, Po-Kai; Chiu, Shih-Liang; Jeng, Jen-Tzong

    2014-01-01

    This paper presents a novel class of miniature fluxgate magnetometers fabricated on a print circuit board (PCB) substrate and electrically connected to each other similar to the current “flip chip” concept in semiconductor package. This sensor is soldered together by reversely flipping a 5 cm × 3 cm PCB substrate to the other identical one which includes dual magnetic cores, planar pick-up coils, and 3-D excitation coils constructed by planar Cu interconnections patterned on PCB substrates. P...

  8. Laser Soldering and Thermal Cycling Tests of Monolithic Silicon Pixel Chips

    CERN Document Server

    Strand, Frode Sneve

    2015-01-01

    An ALPIDE-1 monolithic silicon pixel sensor prototype has been laser soldered to a flex printed circuit using a novel interconnection technique using lasers. This technique is to be optimised to ensure stable, good quality connections between the sensor chips and the FPCs. To test the long-term stability of the connections, as well as study the effects on hit thresholds and noise in the sensor, it was thermally cycled in a climate chamber 1200 times. The soldered connections showed good qualities like even melting and good adhesion on pad/flex surfaces, and the chip remained in working condition for 1080 cycles. After this, a few connections failed, having cracks in the soldering tin, rendering the chip unusable. Threshold and noise characteristics seemed stable, except for the noise levels of sector 2 in the chip, for 1000 cycles in a temperature interval of "10^{\\circ}" and "50^{\\circ}" C. Still, further testing with wider temperature ranges and more cycles is needed to test the limitations of the chi...

  9. Oxidation and reduction kinetics of eutectic SnPb, InSn, and AuSn: a knowledge base for fluxless solder bonding applications

    DEFF Research Database (Denmark)

    Kuhmann, Jochen Friedrich; Preuss, A.; Adolphi, B.

    1998-01-01

    : (1) SnPb; (2) InSn; (3) AuSn. The studies of the oxidation kinetics show that the growth of the native oxide, which covers the solder surfaces from the start of all soldering operations is self-limiting. The rate of oxidation on the molten, metallic solder surfaces is significantly reduced...... and reduction kinetics, are applied to flip-chip (FC) bonding experiments in vacuum with and without the injection of H2. Wetting in vacuum is excellent but the self-alignment during flip-chip soldering is restricted. The desired, perfectly self-aligned FC-bonds have been only achieved, using evaporated...

  10. Polymer Flip Chips with Extreme Temperature Stability in Space, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the proposed SBIR Phase I program is to develop highly thermally and electrically conductive nanocomposites for space-based flip chips for...

  11. Flip-chip bonded optoelectronic integration based on ultrathin silicon (UTSi) CMOS

    Science.gov (United States)

    Hong, Sunkwang; Ho, Tawei; Zhang, Liping; Sawchuk, Alexander A.

    2003-06-01

    We describe the design and test of flip-chip bonded optoelectronic CMOS devices based on Peregrine Semiconductor's 0.5 micron Ultra-Thin Silicon on sapphire (UTSi) technology. The UTSi process eliminates the substrate leakage that typically results in crosstalk and reduces parasitic capacitance to the substrate, providing many benefits compared to bulk silicon CMOS. The low-loss synthetic sapphire substrate is optically transparent and has a coefficient of thermal expansion suitable for flip-chip bonding of vertical cavity surface emitting lasers (VCSELs) and detectors. We have designed two different UTSi CMOS chips. One contains a flip-chip bonded 1 x 4 photodiode array, a receiver array, a double edge triggered D-flip flop-based 2047-pattern pseudo random bit stream (PRBS) generator and a quadrature-phase LC-voltage controlled oscillator (VCO). The other chip contains a flip-chip bonded 1 x 4 VCSEL array, a driver array based on high-speed low-voltage differential signals (LVDS) and a full-balanced differential LC-VCO. Each VCSEL driver and receiver has individual input and bias voltage adjustments. Each UTSi chip is mounted on different printed circuit boards (PCBs) which have holes with about 1 mm radius for optical output and input paths through the sapphire substrate. We discuss preliminary testing of these chips.

  12. Interface thermal characteristics of flip chip packages - A numerical study

    International Nuclear Information System (INIS)

    Kandasamy, Ravi; Mujumdar, A.S.

    2009-01-01

    Flip chip ball grid array (FC-BGA) packages are commonly used for high inputs/outputs (I/O) ICs; they have been proven to provide good solutions for a variety of applications to maximize thermal and electrical performance. A fundamental limitation to such devices is the thermal resistance at the top of the package, which is characterized θ JC parameter. The die-to-lid interface thermal resistance is identified as a critical issue for the thermal management of electronic packages. This paper focuses on the effect of the interface material property changes on the interface thermal resistance. The effect of package's junction to case (Theta-JC or θ JC ) thermal performance is investigated for bare die, flat lid and cup lid packages using a validated thermal model. Thermal performance of a cup or flat lid attached and bare die packages were investigated for different interface materials. Improved Theta-JC performance was observed for the large die as compared to the smaller die. Several parametric studies were carried out to understand the effects of interface bond line thickness (BLT), different die sizes, the average void size during assembly and thermal conductivity of interface materials on package thermal resistance

  13. Molded underfill (MUF) encapsulation for flip-chip package: A numerical investigation

    Science.gov (United States)

    Azmi, M. A.; Abdullah, M. K.; Abdullah, M. Z.; Ariff, Z. M.; Saad, Abdullah Aziz; Hamid, M. F.; Ismail, M. A.

    2017-07-01

    This paper presents the numerical simulation of epoxy molding compound (EMC) filling in multi flip-chip packages during encapsulation process. The empty and a group flip chip packages were considered in the mold cavity in order to study the flow profile of the EMC. SOLIDWORKS software was used for three-dimensional modeling and it was incorporated into fluid analysis software namely as ANSYS FLUENT. The volume of fluid (VOF) technique was used for capturing the flow front profiles and Power Law model was applied for its rheology model. The numerical result are compared and discussed with previous experimental and it was shown a good conformity for model validation. The prediction of flow front was observed and analyzed at different filling time. The possibility and visual of void formation in the package is captured and the number of flip-chip is one factor that contributed to the void formation.

  14. A novel conductive-polymer-based integration process for high-performance flip-chip packages

    Science.gov (United States)

    Lohokare, Saurabh

    Conductive polymers have recently attracted considerable attention for low-temperature fabrication of lead-free, reworkable, and flexible flip-chip interconnects. Using these materials, I demonstrate in this thesis a process that enables low-cost and high-resolution flip-chip interconnects using conventional micro-fabrication techniques. This fabrication process offers improved performance as compared to conventional flip-chip techniques, such as screen-printing, and allows for definition of interconnects with excellent surface uniformity and control over the bump profile. In order to demonstrate the utility and wide applicability of this process, several test implementations that serve as case studies were investigated. Specifically, novel InGaAsSb avalanche photodiodes (APDs), operating around lambda = 2m and targeted for free-space communication and biomedical spectroscopy applications, were fabricated and flip-chip-integrated to test the static electrical characteristics of the polymer bumps. Additionally, the dynamic electrical performance characteristics of the polymer bumps were studied by using AlGaAsSb/AlGaSb p-i-n photodetectors as a case study. The fabrication of these photodetectors, operating around lambda = 1.55mum and targeted for optical communication applications, was accomplished using a customized inductively coupled plasma (ICP) etch process that resulted in a low dark current and excellent speed (3dB bandwidth of 10GHz) and, responsivity (60% external quantum efficiency) characteristics. Furthermore, flip-chip integration was used to demonstrate a three-dimensional, point-to-point micro-optical interconnect, which was 2.33mm-long in a system 15.27mm3 in volume. Lastly, high-speed parallel optical interconnects were demonstrated using polymer-flip-chip-integrated 10GHz vertical-cavity surface-emitting laser (VCSEL) and DOEs. Such interconnects offer the ability to alleviate the communication bottleneck that is projected to occur in future, high

  15. Robust design and thermal fatigue life prediction of anisotropic conductive film flip chip package

    International Nuclear Information System (INIS)

    Nam, Hyun Wook

    2004-01-01

    The use of flip-chip technology has many advantages over other approaches for high-density electronic packaging. ACF(Anisotropic Conductive Film) is one of the major flip-chip technologies, which has short chip-to-chip interconnection length, high productivity, and miniaturization of package. In this study, thermal fatigue life of ACF bonding flip-chip package has been predicted. Elastic and thermal properties of ACF were measured by using DMA and TMA. Temperature dependent nonlinear bi-thermal analysis was conducted and the result was compared with Moire interferometer experiment. Calculated displacement field was well matched with experimental result. Thermal fatigue analysis was also conducted. The maximum shear strain occurs at the outmost located bump. Shear stress-strain curve was obtained to calculate fatigue life. Fatigue model for electronic adhesives was used to predict thermal fatigue life of ACF bonding flip-chip packaging. DOE (Design Of Experiment) technique was used to find important design factors. The results show that PCB CTE (Coefficient of Thermal Expansion) and elastic modulus of ACF material are important material parameters. And as important design parameters, chip width, bump pitch and bump width were chose. 2 nd DOE was conducted to obtain RSM equation for the choose 3 design parameter. The coefficient of determination (R 2 ) for the calculated RSM equation is 0.99934. Optimum design is conducted using the RSM equation. MMFD (Modified Method for Feasible Direction) algorithm is used to optimum design. The optimum value for chip width, bump pitch and bump width were 7.87mm, 430μm, and 78μm, respectively. Approximately, 1400 cycles have been expected under optimum conditions. Reliability analysis was conducted to find out guideline for control range of design parameter. Sigma value was calculated with changing standard deviation of design variable. To acquire 6 sigma level thermal fatigue reliability, the Std. Deviation of design parameter

  16. Impact of Isothermal Aging and Testing Temperature on Large Flip-Chip BGA Interconnect Mechanical Shock Performance

    Science.gov (United States)

    Lee, Tae-Kyu; Chen, Zhiqiang; Guirguis, Cherif; Akinade, Kola

    2017-10-01

    The stability of solder interconnects in a mechanical shock environment is crucial for large body size flip-chip ball grid array (FCBGA) electronic packages. Additionally, the junction temperature increases with higher electric power condition, which brings the component into an elevated temperature environment, thus introducing another consideration factor for mechanical stability of interconnection joints. Since most of the shock performance data available were produced at room temperature, the effect of elevated temperature is of interest to ensure the reliability of the device in a mechanical shock environment. To achieve a stable␣interconnect in a dynamic shock environment, the interconnections must tolerate mechanical strain, which is induced by the shock wave input and reaches the particular component interconnect joint. In this study, large body size (52.5 × 52.5 mm2) FCBGA components assembled on 2.4-mm-thick boards were tested with various isothermal pre-conditions and testing conditions. With a heating element embedded in the test board, a test temperature range from room temperature to 100°C was established. The effects of elevated temperature on mechanical shock performance were investigated. Failure and degradation mechanisms are identified and discussed based on the microstructure evolution and grain structure transformations.

  17. Effect of solder bump size on interfacial reactions during soldering between Pb-free solder and Cu and Ni/ Pd/ Au surface finishes

    International Nuclear Information System (INIS)

    NorAkmal, F.; Ourdjini, A.; Azmah Hanim, M.A.; Siti Aisha, I.; Chin, Y.T.

    2007-01-01

    Flip chip technology provides the ultimate in high I/ O-density and count with superior electrical performance for interconnecting electronic components. Therefore, the study of the intermetallic compounds was conducted to investigate the effect of solder bumps sizes on several surface finishes which are copper and Electroless Nickel/ Electroless Palladium/ Immersion Gold (ENEPIG) which is widely used in electronics packaging as surface finish for flip-chip application nowadays. In this research, field emission scanning electron microscopy (FESEM) analysis was conducted to analyze the morphology and composition of intermetallic compounds (IMCs) formed at the interface between the solder and UBM. The IMCs between the SAC lead-free solder with Cu surface finish after reflow were mainly (Cu, Ni) 6 Sn 5 and Cu 6 Sn 5 . While the main IMCs formed between lead-free solder on ENEPIG surface finish are (Ni, Cu) 3 Sn 4 and Ni 3 Sn 4 . The results from FESEM with energy dispersive x-ray (EDX) have revealed that isothermal aging at 150 degree Celsius has caused the thickening and coarsening of IMCs as well as changing them into more spherical shape. The thickness of the intermetallic compounds in both finishes investigated was found to be higher in solders with smaller bump size. From the experimental results, it also appears that the growth rate of IMCs is higher when soldering on copper compared to ENEPIG finish. Besides that, the results also showed that the thickness of intermetallic compounds was found to be proportional to isothermal aging duration. (author)

  18. Fluxless Bonding Processes Using Silver-Indium System for High Temperature Electronics and Silver Flip-Chip Interconnect Technology

    Science.gov (United States)

    Wu, Yuan-Yun

    In this dissertation, fluxless silver (Ag)-indium (In) binary system bonding and Ag solid-state bonding are used between different bonded pairs which have large thermal expansion coefficient (CTE) mismatch and flip-chip interconnect bonding application. In contrast to the conventional soldering process, fluxless bonding technique eliminates contamination and reliability problems caused by flux to fabricate high quality joints. There are two section are reported. In the first section, the reactions of Ag-In binary system are presented. In the second section, the high melting temperature, thermal and electrical conductivity joint materials bonding by either Ag-In binary system bonding or solid-state bonding processes for different bonded pairs and flip-chip application are designed, developed, and reported. Our group have studied Ag-In system for several years and developed the bonding processes successfully. However, the detailed reactions of Ag and In were seldom studied. To design a proper bonding structure, it is necessary to understand the reaction between Ag and In. The systematic experiments were performed to investigate these reactions. A 40 um Ag layer was electroplated on copper (Cu) substrates, followed by indium layers of 1, 3, 5, 10, and 15 um, respectively. The samples were annealed at 180 °C in 0.1 torr vacuum. For samples with In thickness less than 5 mum, the joint compositions are Ag2In only (1 um) or AgIn2, Ag2In, and Ag solid solution (Ag) after annealing. No indium is identified. For 10 and 15 um thick In samples, In covers almost over the entire sample surface after annealing. Later, an Ag layer was annealed at 450 °C for 3 hours to grow Ag grains, followed by plating 10 um In and annealing at 180 °C. By annealing Ag before plating In, more In is kept in the structure during annealing at 180 °C. Based on above results, for those designs with In thinner than 5 um, the Ag layer needs to be annealed, prior to In plating in order to make a

  19. Influence of Difference Solders Volume on Intermetallic Growth of Sn-4.0Ag-0.5Cu/ENEPIG

    Directory of Open Access Journals (Sweden)

    Saliza Azlina O.

    2016-01-01

    Full Text Available In recent years, portable electronic packaging products such as smart phones, tablets, notebooks and other gadgets have been developed with reduced size of component packaging, light weight, high speed and with enhanced performance. Thus, flip chip technology with smaller solder sphere sizes that would produce fine solder joint interconnections have become essential in order to fulfill these miniaturization requirements. This study investigates the interfacial reactions and intermetallics formation during reflow soldering and isothermal aging between Sn-4.0Ag-0.5Cu (SAC405 and electroless nickel/immersion palladium/immersion gold (EN(PEPIG. Solder diameters of 300 μm and 700 μm were used to compare the effect of solder volume on the solder joint microstructure. The solid state isothermal aging was performed at 125°C starting from 250 hours until 2000 hours. The results revealed that only (Cu,Ni6Sn5 IMC was found at the interface during reflow soldering while both (Cu,Ni6Sn5 and (Ni,Cu3Sn4 IMC have been observed after aging process. Smaller solder sizes produced thinner IMC than larger solder joints investigated after reflow soldering, whereas the larger solders produced thinner IMC than the smaller solders after isothermal aging. Aging duration of solder joints has been found to be increase the IMC’s thickness and changed the IMC morphologies to spherical-shaped, compacted and larger grain size.

  20. Optimization of high frequency flip-chip interconnects for digital superconducting circuits

    International Nuclear Information System (INIS)

    Rafique, M R; Engseth, H; Kidiyarova-Shevchenko, A

    2006-01-01

    This paper presents the results of theoretical optimization of the multi-chip-module (MCM) contact and driver circuitries for gigabit chip-to-chip communication. Optimization has been done using 3D electromagnetic (EM) simulations of MCM contacts and time domain simulations of drivers and receivers. A single optimized MCM contact has a signal reflection of less than -20 dB for more than 400 GHz bandwidth. The MCM data link with the optimized SFQ driver, receiver and two MCM contacts has operational margins on the global bias current of ± 30% at 30 Gbit s -1 speedand can operate above 100 Gbit s -1 speed. Wide bandwidth transmission requires the realization of an advanced flip-chip process with a small dimension of the MCM contact (less than 30 μm diameter of the contact pad) and small height of the flip-chip contact bumps of the order of 2 μm. Current processes with about 7 μm height of the bumps require the application of a double-flux-quantum (DFQ) driver. The data link with the DFQ driver was also simulated. It has operational margins on the global bias current of ± 30% at 30 Gbit s -1 ; however, the maximum speed of operation is 61 Gbit s -1 . Several test structures have been designed for measurements of signal reflection, bit error rate and operational margins of the data link

  1. High-Tc dc-SQUID gradiometers in flip-chip configuration

    International Nuclear Information System (INIS)

    Peiselt, K; Schmidl, F; Linzen, S; Anton, A S; Huebner, U; Seidel, P

    2003-01-01

    We describe a new design of a gradiometric flip-chip antenna, which is inductively coupled to a dc-SQUID gradiometer. Both components are patterned out of thin films of the high-T c superconductor YBa 2 Cu 3 O 7-x (YBCO). For the flip-chip antenna, a 40 mm x 10 mm SrTiO 3 single crystalline substrate is used, while the gradiometer sensors are prepared on 10 mm x 10 mm SrTiO 3 bicrystal substrates. Special attention is paid to the inductive coupling between the flip-chip antenna and the read-out gradiometer antenna. We investigate different designs of coupling loops in order to optimize the coupling inductance between both components of the sensor. With optimized coupling the sensor achieves a field-gradient resolution of 12 fT cm -1 Hz -1/2 in the white noise region and of 310 fT cm -1 Hz -1/2 at 1 Hz in the unshielded laboratory environment

  2. High-Tc dc-SQUID gradiometers in flip-chip configuration

    Science.gov (United States)

    Peiselt, K.; Schmidl, F.; Linzen, S.; Anton, A. S.; Hübner, U.; Seidel, P.

    2003-12-01

    We describe a new design of a gradiometric flip-chip antenna, which is inductively coupled to a dc-SQUID gradiometer. Both components are patterned out of thin films of the high-Tc superconductor YBa2Cu3O7-x (YBCO). For the flip-chip antenna, a 40 mm × 10 mm SrTiO3 single crystalline substrate is used, while the gradiometer sensors are prepared on 10 mm × 10 mm SrTiO3 bicrystal substrates. Special attention is paid to the inductive coupling between the flip-chip antenna and the read-out gradiometer antenna. We investigate different designs of coupling loops in order to optimize the coupling inductance between both components of the sensor. With optimized coupling the sensor achieves a field-gradient resolution of 12 fT cm-1 Hz-1/2 in the white noise region and of 310 fT cm-1 Hz-1/2 at 1 Hz in the unshielded laboratory environment.

  3. Chip-scale white flip-chip light-emitting diode containing indium phosphide/zinc selenide quantum dots

    Science.gov (United States)

    Fan, Bingfeng; Yan, Linchao; Lao, Yuqin; Ma, Yanfei; Chen, Zimin; Ma, Xuejin; Zhuo, Yi; Pei, Yanli; Wang, Gang

    2017-08-01

    A method for preparing a quantum dot (QD)-white light-emitting diode (WLED) is reported. Holes were etched in the SiO2 layer deposited on the sapphire substrate of the flip-chip LED by inductively coupled plasma, and these holes were then filled with QDs. An ultraviolet-curable resin was then spin-coated on top of the QD-containing SiO2 layer, and the resin was cured to act as a protecting layer. The reflective sidewall structure minimized sidelight leakage. The fabrication of the QD-WLED is simple in preparation and compatible with traditional LED processes, which was the minimum size of the WLED chip-scale integrated package. InP/ZnS core-shell QDs were used as the converter in the WLED. A blue light-emitting diode with a flip-chip structure was used as the excitation source. The QD-WLED exhibited color temperatures from 5900 to 6400 K and Commission Internationale De L'Elcairage color coordinates from (0.315, 0.325) to (0.325, 0.317), under drive currents from 100 to 400 mA. The QD-WLED exhibited stable optoelectronic properties.

  4. Research on Defects Inspection of Solder Balls Based on Eddy Current Pulsed Thermography

    Directory of Open Access Journals (Sweden)

    Xiuyun Zhou

    2015-10-01

    Full Text Available In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT. Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique.

  5. Thermal fatigue life evaluation of SnAgCu solder joints in a multi-chip power module

    Science.gov (United States)

    Barbagallo, C.; Malgioglio, G. L.; Petrone, G.; Cammarata, G.

    2017-05-01

    For power devices, the reliability of thermal fatigue induced by thermal cycling has been prioritized as an important concern. The main target of this work is to apply a numerical procedure to assess the fatigue life for lead-free solder joints, that represent, in general, the weakest part of the electronic modules. Starting from a real multi-chip power module, FE-based models were built-up by considering different conditions in model implementation in order to simulate, from one hand, the worst working condition for the module and, from another one, the module standing into a climatic test room performing thermal cycles. Simulations were carried-out both in steady and transient conditions in order to estimate the module thermal maps, the stress-strain distributions, the effective plastic strain distributions and finally to assess the number of cycles to failure of the constitutive solder layers.

  6. Thermal fatigue life evaluation of SnAgCu solder joints in a multi-chip power module

    International Nuclear Information System (INIS)

    Barbagallo, C; Petrone, G; Cammarata, G; Malgioglio, G L

    2017-01-01

    For power devices, the reliability of thermal fatigue induced by thermal cycling has been prioritized as an important concern. The main target of this work is to apply a numerical procedure to assess the fatigue life for lead-free solder joints, that represent, in general, the weakest part of the electronic modules. Starting from a real multi-chip power module, FE-based models were built-up by considering different conditions in model implementation in order to simulate, from one hand, the worst working condition for the module and, from another one, the module standing into a climatic test room performing thermal cycles. Simulations were carried-out both in steady and transient conditions in order to estimate the module thermal maps, the stress-strain distributions, the effective plastic strain distributions and finally to assess the number of cycles to failure of the constitutive solder layers. (paper)

  7. Instantaneous fluxless bonding of Au with Pb-Sn solder in ambient atmosphere

    International Nuclear Information System (INIS)

    Lee, T.K.; Zhang, Sam; Wong, C.C.; Tan, A.C.

    2005-01-01

    A fluxless bonding technique has been developed as a method of flip-chip bonding for microelectronic packaging. The fluxless bonding technique can be achieved instantaneously in an ambient environment between metallic stud bumps and predefined molten solder. This paper describes the mechanics of the bonding action and verifies the effectiveness of this bonding method through wetting balance tests and scanning electron microscope and energy dispersive x-ray analysis. This technique has been demonstrated by using a gold stud bump to break the tin oxide layer over molten solder. This allows for a fast, solid liquid interdiffusion between gold (Au) and the fresh molten eutectic lead-tin (Pb-Sn) solder for joint formation during solidification. This bonding method has been successfully tested with 130-μm-pitch flip-chip bond pads on a joint-in-via flex substrate architecture

  8. Effect of Preconditioning and Soldering on Failures of Chip Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander A.

    2014-01-01

    Soldering of molded case tantalum capacitors can result in damage to Ta205 dielectric and first turn-on failures due to thermo-mechanical stresses caused by CTE mismatch between materials used in the capacitors. It is also known that presence of moisture might cause damage to plastic cases due to the pop-corning effect. However, there are only scarce literature data on the effect of moisture content on the probability of post-soldering electrical failures. In this work, that is based on a case history, different groups of similar types of CWR tantalum capacitors from two lots were prepared for soldering by bake, moisture saturation, and longterm storage at room conditions. Results of the testing showed that both factors: initial quality of the lot, and preconditioning affect the probability of failures. Baking before soldering was shown to be effective to prevent failures even in lots susceptible to pop-corning damage. Mechanism of failures is discussed and recommendations for pre-soldering bake are suggested based on analysis of moisture characteristics of materials used in the capacitors' design.

  9. Analysis of a flip-chip bonded tunable high-temperature superconducting coplanar waveguide resonator using the conformal mapping technique

    CERN Document Server

    Misra, M; Murakami, H; Tonouchi, M

    2003-01-01

    We have studied the tuning properties of a high-temperature superconducting (HTS) half-wavelength coplanar waveguide (CPW) resonator operating at 5 GHz. The tuning schemes are based on flip-chip bonding of an electrically tunable ferroelectric (FE) thin film and a mechanically movable low-loss single crystal on top of the resonator. Using the conformal mapping method, closed-form analytical expressions have been derived for a flip-chip bonded conductor-backed and top-shielded CPW transmission line. The obtained expressions are used to analyse the volume effect of the FE thin film and the gap between the flip-chip and the CPW resonator on the tuning properties of the device. It has been found that large frequency modulation of the resonator produces impedance mismatch, which can considerably enhance the insertion loss of high-performance HTS microwave devices. Analysis also suggests that, for electrically tunable devices, flip-chip bonded FE thin films on HTS CPW devices provide a relatively higher performance...

  10. Development of new assembly techniques for a silicon micro-vertex detector unit using the flip-chip bonding method

    International Nuclear Information System (INIS)

    Saitoh, Y.; Takeuchi, H.; Mandai, M.; Kanazawa, H.; Yamanaka, J.; Miyahara, S.; Kamiya, M.; Fujita, Y.; Higashi, Y.; Ikeda, H.; Ikeda, M.; Koike, S.; Matsuda, T.; Ozaki, H.; Tanaka, M.; Tsuboyama, T.; Avrillon, S.; Okuno, S.; Haba, J.; Hanai, H.; Mori, S.; Yusa, K.; Fukunaga, C.

    1994-01-01

    Full-size models of a detector unit for a silicon micro-vertex detector were built for the KEK B factory. The Flip-Chip Bonding (FCB) method using a new type anisotropic conductive film was examined. The structure using the FCB method successfully provides a new architecture for the silicon micro-vertex detector unit. (orig.)

  11. In-situ study of electromigration-induced grain rotation in Pb-free solder joint by synchrotron microdiffraction

    International Nuclear Information System (INIS)

    Chen, Kai; Tamura, Nobumichi; Tu, King-Ning

    2008-01-01

    The rotation of Sn grains in Pb-free flip chip solder joints hasn't been reported in literature so far although it has been observed in Sn strips. In this letter, we report the detailed study of the grain orientation evolution induced by electromigration by synchrotron based white beam X-ray microdiffraction. It is found that the grains in solder joint rotate more slowly than in Sn strip even under higher current density. On the other hand, based on our estimation, the reorientation of the grains in solder joints also results in the reduction of electric resistivity, similar to the case of Sn strip. We will also discuss the reason why the electric resistance decreases much more in strips than in the Sn-based solders, and the different driving force for the grain growth in solder joint and in thin film interconnect lines

  12. In-situ study of electromigration-induced grain rotation in Pb-free solder joint by synchrotron microdiffraction

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Kai; Tamura, Nobumichi; Tu, King-Ning

    2008-10-31

    The rotation of Sn grains in Pb-free flip chip solder joints hasn't been reported in literature so far although it has been observed in Sn strips. In this letter, we report the detailed study of the grain orientation evolution induced by electromigration by synchrotron based white beam X-ray microdiffraction. It is found that the grains in solder joint rotate more slowly than in Sn strip even under higher current density. On the other hand, based on our estimation, the reorientation of the grains in solder joints also results in the reduction of electric resistivity, similar to the case of Sn strip. We will also discuss the reason why the electric resistance decreases much more in strips than in the Sn-based solders, and the different driving force for the grain growth in solder joint and in thin film interconnect lines.

  13. Mechanism of Void Prediction in Flip Chip Packages with Molded Underfill

    Science.gov (United States)

    Wu, Kuo-Tsai; Hwang, Sheng-Jye; Lee, Huei-Huang

    2017-08-01

    Voids have always been present using the molded underfill (MUF) package process, which is a problem that needs further investigation. In this study, the process was studied using the Moldex3D numerical analysis software. The effects of gas (air vent effect) on the overall melt front were also considered. In this isothermal process containing two fluids, the gas and melt colloid interact in the mold cavity. Simulation enabled an appropriate understanding of the actual situation to be gained, and, through analysis, the void region and exact location of voids were predicted. First, the global flow end area was observed to predict the void movement trend, and then the local flow ends were observed to predict the location and size of voids. In the MUF 518 case study, simulations predicted the void region as well as the location and size of the voids. The void phenomenon in a flip chip ball grid array underfill is discussed as part of the study.

  14. Spatial redistribution of radiation in flip-chip photodiodes based on InAsSbP/InAs double heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zakgeim, A. L. [Russian Academy of Sciences, Scientific and Technological Center for Microelectronics (Russian Federation); Il’inskaya, N. D.; Karandashev, S. A.; Lavrov, A. A., E-mail: ioffeled@mail.ru; Matveev, B. A.; Remennyy, M. A.; Stus’, N. M.; Usikova, A. A. [Russian Academy of Sciences, Ioffe Institute (Russian Federation); Cherniakov, A. E. [Russian Academy of Sciences, Scientific and Technological Center for Microelectronics (Russian Federation)

    2017-02-15

    The spatial distribution of equilibrium and nonequilibrium (including luminescent) IR (infrared) radiation in flip-chip photodiodes based on InAsSbP/InAs double heterostructures (λ{sub max} = 3.4 μm) is measured and analyzed; the structural features of the photodiodes, including the reflective properties of the ohmic contacts, are taken into account. Optical area enhancement due to multiple internal reflection in photodiodes with different geometric characteristics is estimated.

  15. Damage behavior of SnAgCu/Cu solder joints subjected to thermomechanical cycling

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, H., E-mail: xiaohui2013@yahoo.com.cn; Li, X.Y.; Hu, Y.; Guo, F.; Shi, Y.W.

    2013-11-25

    Highlights: •A creep–fatigue damage model based on CDM was proposed. •Designed system includes load frame, strain measure device and damage test device. •Damage evolution of solder joints was a function of accumulated inelastic strain. •Damage of solder joints is an interaction between creep and low-cycle fatigue. -- Abstract: Thermomechanical fatigue damage is a progressive process of material degradation. The objective of this study was to investigate the damage behavior of SnAgCu/Cu solder joints under thermomechanical cycling. A damage model was proposed based on continuum damage mechanics (CDM). Based upon an analysis of displacements for flip-chip solder joints subjected to thermal cycling, a special bimetallic loading frame with single-solder joint samples was designed to simulate the service conditions of actual joints in electronic packages. The assembly, which allowed for strain measurements of an individual solder joint during temperature cycling, was used to investigate the impact of stress–strain cycling on the damage behavior of SnAgCu/Cu solder joints. The characteristic parameters of the damage model were determined through thermomechanical cycling and strain measurement tests. The damage variable D = 1 − R{sub 0}/R was selected, and values for it were obtained using a four-probe method for the single-solder joint samples every dozen cycles during thermomechanical cycling tests to verify the model. The results showed that the predicted damage was in good agreement with the experimental results. The damage evolution law proposed here is a function of inelastic strain, and the results showed that the damage rate of SnAgCu/Cu solder joints increased as the range of the applied strain increased. In addition, the microstructure evolution of the solder joints was analyzed using scanning electron microscopy, which provided the microscopic explanation for the damage evolution law of SnAgCu/Cu solder joints.

  16. Damage behavior of SnAgCu/Cu solder joints subjected to thermomechanical cycling

    International Nuclear Information System (INIS)

    Xiao, H.; Li, X.Y.; Hu, Y.; Guo, F.; Shi, Y.W.

    2013-01-01

    Highlights: •A creep–fatigue damage model based on CDM was proposed. •Designed system includes load frame, strain measure device and damage test device. •Damage evolution of solder joints was a function of accumulated inelastic strain. •Damage of solder joints is an interaction between creep and low-cycle fatigue. -- Abstract: Thermomechanical fatigue damage is a progressive process of material degradation. The objective of this study was to investigate the damage behavior of SnAgCu/Cu solder joints under thermomechanical cycling. A damage model was proposed based on continuum damage mechanics (CDM). Based upon an analysis of displacements for flip-chip solder joints subjected to thermal cycling, a special bimetallic loading frame with single-solder joint samples was designed to simulate the service conditions of actual joints in electronic packages. The assembly, which allowed for strain measurements of an individual solder joint during temperature cycling, was used to investigate the impact of stress–strain cycling on the damage behavior of SnAgCu/Cu solder joints. The characteristic parameters of the damage model were determined through thermomechanical cycling and strain measurement tests. The damage variable D = 1 − R 0 /R was selected, and values for it were obtained using a four-probe method for the single-solder joint samples every dozen cycles during thermomechanical cycling tests to verify the model. The results showed that the predicted damage was in good agreement with the experimental results. The damage evolution law proposed here is a function of inelastic strain, and the results showed that the damage rate of SnAgCu/Cu solder joints increased as the range of the applied strain increased. In addition, the microstructure evolution of the solder joints was analyzed using scanning electron microscopy, which provided the microscopic explanation for the damage evolution law of SnAgCu/Cu solder joints

  17. A novel model for simulating the racing effect in capillary-driven underfill process in flip chip

    Science.gov (United States)

    Zhu, Wenhui; Wang, Kanglun; Wang, Yan

    2018-04-01

    Underfill is typically applied in flip chips to increase the reliability of the electronic packagings. In this paper, the evolution of the melt-front shape of the capillary-driven underfill flow is studied through 3D numerical analysis. Two different models, the prevailing surface force model and the capillary model based on the wetted wall boundary condition, are introduced to test their applicability, where level set method is used to track the interface of the two phase flow. The comparison between the simulation results and experimental data indicates that, the surface force model produces better prediction on the melt-front shape, especially in the central area of the flip chip. Nevertheless, the two above models cannot simulate properly the racing effect phenomenon that appears during underfill encapsulation. A novel ‘dynamic pressure boundary condition’ method is proposed based on the validated surface force model. Utilizing this approach, the racing effect phenomenon is simulated with high precision. In addition, a linear relationship is derived from this model between the flow front location at the edge of the flip chip and the filling time. Using the proposed approach, the impact of the underfill-dispensing length on the melt-front shape is also studied.

  18. Soldering handbook

    CERN Document Server

    Vianco, Paul T

    1999-01-01

    Contains information related to soldering processes, and solder joint performance and reliability. Covers soldering fundamentals, technology, materials, substrate materials, fluxes, pastes, assembly processes, inspection, and environment. Covers today's advanced joining applications and emphasizes new materials, including higher strength alloys; predictive performance; computer modeling; advanced inspection techniques; new processing concepts, including laser heating; and the resurgence in ultrasonic soldering.

  19. Electromigration-induced back stress in critical solder length for three-dimensional integrated circuits

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Y. T.; Hsu, H. H.; Wu, Albert T., E-mail: atwu@ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Jhongli City 320, Taiwan (China)

    2014-01-21

    Because of the miniaturization of electronic devices, the reliability of electromigration has become a major concern when shrinking the solder dimensions in flip-chip joints. Fast reaction between solders and electrodes causes intermetallic compounds (IMCs) to form, which grow rapidly and occupy entire joints when solder volumes decrease. In this study, U-grooves were fabricated on Si chips as test vehicles. An electrode-solder-electrode sandwich structure was fabricated by using lithography and electroplating. Gaps exhibiting well-defined dimensions were filled with Sn3.5Ag solders. The gaps between the copper electrodes in the test sample were limited to less than 15 μm to simulate microbumps. The samples were stressed at various current densities at 100 °C, 125 °C, and 150 °C. The morphological changes of the IMCs were observed, and the dimensions of the IMCs were measured to determine the kinetic growth of IMCs. Therefore, this study focused on the influence of back stress caused by microstructural evolution in microbumps.

  20. Thermomechanical Behavior of Monolithic SN-AG-CU Solder and Copper Fiber Reinforced Solders

    National Research Council Canada - National Science Library

    Reuse, Rolando

    2005-01-01

    .... The thermomechanical cycling in the solder causes numerous reliability challenges, mostly because of the mismatch of the coefficient of thermal expansion between the silicon chip and the substrate...

  1. Investigation Of The Effects Of Reflow Profile Parameters On Lead-free Solder Bump Volumes And Joint Integrity

    Science.gov (United States)

    Amalu, E. H.; Lui, Y. T.; Ekere, N. N.; Bhatti, R. S.; Takyi, G.

    2011-01-01

    The electronics manufacturing industry was quick to adopt and use the Surface Mount Technology (SMT) assembly technique on realization of its huge potentials in achieving smaller, lighter and low cost product implementations. Increasing global customer demand for miniaturized electronic products is a key driver in the design, development and wide application of high-density area array package format. Electronic components and their associated solder joints have reduced in size as the miniaturization trend in packaging continues to be challenged by printing through very small stencil apertures required for fine pitch flip-chip applications. At very narrow aperture sizes, solder paste rheology becomes crucial for consistent paste withdrawal. The deposition of consistent volume of solder from pad-to-pad is fundamental to minimizing surface mount assembly defects. This study investigates the relationship between volume of solder paste deposit (VSPD) and the volume of solder bump formed (VSBF) after reflow, and the effect of reflow profile parameters on lead-free solder bump formation and the associated solder joint integrity. The study uses a fractional factorial design (FFD) of 24-1 Ramp-Soak-Spike reflow profile, with all main effects and two-way interactions estimable to determine the optimal factorial combination. The results from the study show that the percentage change in the VSPD depends on the combination of the process parameters and reliability issues could become critical as the size of solder joints soldered on the same board assembly vary greatly. Mathematical models describe the relationships among VSPD, VSBF and theoretical volume of solder paste. Some factors have main effects across the volumes and a number of interactions exist among them. These results would be useful for R&D personnel in designing and implementing newer applications with finer-pitch interconnect.

  2. Thermal cycling reliability of Cu/SnAg double-bump flip chip assemblies for 100 μm pitch applications

    Science.gov (United States)

    Son, Ho-Young; Kim, Ilho; Lee, Soon-Bok; Jung, Gi-Jo; Park, Byung-Jin; Paik, Kyung-Wook

    2009-01-01

    A thick Cu column based double-bump flip chip structure is one of the promising alternatives for fine pitch flip chip applications. In this study, the thermal cycling (T/C) reliability of Cu/SnAg double-bump flip chip assemblies was investigated, and the failure mechanism was analyzed through the correlation of T/C test and the finite element analysis (FEA) results. After 1000 thermal cycles, T/C failures occurred at some Cu/SnAg bumps located at the edge and corner of chips. Scanning acoustic microscope analysis and scanning electron microscope observations indicated that the failure site was the Cu column/Si chip interface. It was identified by a FEA where the maximum stress concentration was located during T/C. During T/C, the Al pad between the Si chip and a Cu column bump was displaced due to thermomechanical stress. Based on the low cycle fatigue model, the accumulation of equivalent plastic strain resulted in thermal fatigue deformation of the Cu column bumps and ultimately reduced the thermal cycling lifetime. The maximum equivalent plastic strains of some bumps at the chip edge increased with an increased number of thermal cycles. However, equivalent plastic strains of the inner bumps did not increase regardless of the number of thermal cycles. In addition, the z-directional normal plastic strain ɛ22 was determined to be compressive and was a dominant component causing the plastic deformation of Cu/SnAg double bumps. As the number of thermal cycles increased, normal plastic strains in the perpendicular direction to the Si chip and shear strains were accumulated on the Cu column bumps at the chip edge at low temperature region. Thus it was found that the Al pad at the Si chip/Cu column interface underwent thermal fatigue deformation by compressive normal strain and the contact loss by displacement failure of the Al pad, the main T/C failure mode of the Cu/SnAg flip chip assembly, then occurred at the Si chip/Cu column interface shear strain deformation

  3. Improvement of surface light extraction from flip-chip GaN-based LED by embossing of thermosetting polymers

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Kui; Zhang, Bei; Wang, ZhiMin; Dai, Tao; Kang, XiangNing; Chen, ZhiZhong; Xu, Ke; Ji, Hang; Chen, Yong; Gan, ZiZhao [School of Physics and State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Peking University, Beijing 100871 (China)

    2007-07-01

    In this report, a further improvement of surface light extraction from flip-chip GaN-based LED was obtained by the micro patterning of encapsulation on the sapphire. The two dimensional taper arrays with period from 6 to 10 micron were successfully realized on polymer encapsulation by a simple and low cost technique so called embossing of thermosetting polymers. As a preliminary demonstration, at least 1.74 enhancement of the surface output intensity was achieved in the 1 mm x 1 mm GaN-based LED device under the injection current of 350 mA. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Laser soldering of Sn-Ag-Cu and Sn-Zn-Bi lead-free solder pastes

    Science.gov (United States)

    Takahashi, Junichi; Nakahara, Sumio; Hisada, Shigeyoshi; Fujita, Takeyoshi

    2004-10-01

    It has reported that a waste of an electronics substrate including lead and its compound such as 63Sn-37Pb has polluted the environment with acid rain. For that environment problem the development of lead-free solder alloys has been promoted in order to find out the substitute for Sn-Pb solders in the United States, Europe, and Japan. In a present electronics industry, typical alloys have narrowed down to Sn-Ag-Cu and Sn-Zn lead-free solder. In this study, solderability of Pb-free solder that are Sn-Ag-Cu and Sn-Zn-Bi alloy was studied on soldering using YAG (yttrium aluminum garnet) laser and diode laser. Experiments were peformed in order to determine the range of soldering parameters for obtaining an appropriate wettability based on a visual inspection. Joining strength of surface mounting chip components soldered on PCB (printed circuit board) was tested on application thickness of solder paste (0.2, 0.3, and 0.4 mm). In addition, joining strength characteristics of eutectic Sn-Pb alloy and under different power density were examined. As a result, solderability of Sn-Ag-Cu (Pb-free) solder paste are equivalent to that of coventional Sn-Pb solder paste, and are superior to that of Sn-Zn-Bi solder paste in the laser soldering method.

  5. Lead free solder mechanics and reliability

    CERN Document Server

    Pang, John Hock Lye

    2012-01-01

    Lead-free solders are used extensively as interconnection materials in electronic assemblies and play a critical role in the global semiconductor packaging and electronics manufacturing industry. Electronic products such as smart phones, notebooks and high performance computers rely on lead-free solder joints to connect IC chip components to printed circuit boards. Lead Free Solder: Mechanics and Reliability provides in-depth design knowledge on lead-free solder elastic-plastic-creep and strain-rate dependent deformation behavior and its application in failure assessment of solder joint reliability. It includes coverage of advanced mechanics of materials theory and experiments, mechanical properties of solder and solder joint specimens, constitutive models for solder deformation behavior; numerical modeling and simulation of solder joint failure subject to thermal cycling, mechanical bending fatigue, vibration fatigue and board-level drop impact tests. This book also: Discusses the mechanical prope...

  6. Spontaneous soldering

    International Nuclear Information System (INIS)

    Percacci, R.

    1984-01-01

    It is proposed that the soldering form of general relativity be treated as a dynamical variable. This gives rise to the possibility of treating the linear connection on (n-dimensional) spacetime and an internal O(k)-Yang-Mills field as different components of the same O(N) gauge field (N= n+k). The distinction between gravitational and Yang-Mills interactions is due to a kind of Higgs mechanism driven by the vacuum expectation value of the soldering form. (orig.)

  7. Electrical characteristics for Sn-Ag-Cu solder bump with Ti/Ni/Cu under-bump metallization after temperature cycling tests

    Science.gov (United States)

    Shih, T. I.; Lin, Y. C.; Duh, J. G.; Hsu, Tom

    2006-10-01

    Lead-free solder bumps have been widely used in current flip-chip technology (FCT) due to environmental issues. Solder joints after temperature cycling tests were employed to investigate the interfacial reaction between the Ti/Ni/Cu under-bump metallization and Sn-Ag-Cu solders. The interfacial morphology and quantitative analysis of the intermetallic compounds (IMCs) were obtained by electron probe microanalysis (EPMA) and field emission electron probe microanalysis (FE-EPMA). Various types of IMCs such as (Cu1-x,Agx)6Sn5, (Cu1-y,Agy)3Sn, and (Ag1-z,Cuz)3Sn were observed. In addition to conventional I-V measurements by a special sample preparation technique, a scanning electron microscope (SEM) internal probing system was introduced to evaluate the electrical characteristics in the IMCs after various test conditions. The electrical data would be correlated to microstructural evolution due to the interfacial reaction between the solder and under-bump metallurgy (UBM). This study demonstrated the successful employment of an internal nanoprobing approach, which would help further understanding of the electrical behavior within an IMC layer in the solder/UBM assembly.

  8. Fundamental study of microelectronic chip response under laser ultrasonic-interferometric inspection using C-scan method

    Science.gov (United States)

    Yang, Lei; Gong, Jie; Ume, I. Charles

    2014-02-01

    In modern surface mount packaging technologies, such as flip chips, chip scale packages, and ball grid arrays(BGA), chips are attached to the substrates/printed wiring board (PWB) using solder bump interconnections. The quality of solder bumps between the chips and the substrate/board is difficult to inspect. Laser ultrasonic-interferometric technique was proved to be a promising approach for solder bump inspection because of its noncontact and nondestructive characteristics. Different indicators extracted from received signals have been used to predict the potential defects, such as correlation coefficient, error ratio, frequency shifting, etc. However, the fundamental understanding of the chip behavior under laser ultrasonic inspection is still missing. Specifically, it is not sure whether the laser interferometer detected out-of-plane displacements were due to wave propagation or structural vibration when the chip was excited by pulsed laser. Plus, it is found that the received signals are chip dependent. Both challenges impede the interpretation of acquired signals. In this paper, a C-scan method was proposed to study the underlying phenomenon during laser ultrasonic inspection. The full chip was inspected. The response of the chip under laser excitation was visualized in a movie resulted from acquired signals. Specifically, a BGA chip was investigated to demonstrate the effectiveness of this method. By characterizing signals using discrete wavelet transform(DWT), both ultrasonic wave propagation and vibration were observed. Separation of them was successfully achieved using ideal band-pass filter and visualized in resultant movies, too. The observed ultrasonic waves were characterized and their respective speeds were measured by applying 2-D FFT. The C-scan method, combined with different digital signal processing techniques, was proved to be an very effective methodology to learn the behavior of chips under laser excitation. This general procedure can be

  9. Soldering in electronics assembly

    CERN Document Server

    Judd, Mike

    2013-01-01

    Soldering in Electronics Assembly discusses several concerns in soldering of electronic assemblies. The book is comprised of nine chapters that tackle different areas in electronic assembly soldering. Chapter 1 discusses the soldering process itself, while Chapter 2 covers the electronic assemblies. Chapter 3 talks about solders and Chapter 4 deals with flux. The text also tackles the CS and SC soldering process. The cleaning of soldered assemblies, solder quality, and standards and specifications are also discussed. The book will be of great use to professionals who deal with electronic assem

  10. Thermal Characteristics of InGaN/GaN Flip-Chip Light Emitting Diodes with Diamond-Like Carbon Heat-Spreading Layers

    Directory of Open Access Journals (Sweden)

    Pai-Yang Tsai

    2014-01-01

    Full Text Available The temperature-dependent optical, electrical, and thermal properties of flip-chip light emitting diodes (FCLEDs with diamond-like carbon (DLC heat-spreading layers were investigated. On the basis of the measured results in the 20°C to 100°C temperature range, a significant performance improvement can be achieved for FCLEDs with DLC heat-spreading layers (DLC-FCLED compared with FCLEDs without DLC heat-spreading layers (non-DLC-FCLED. The external quantum efficiency (EQE of the DLC-FCLED improves by 9% at an injection current of 1000 mA and a temperature of 100°C. The forward voltage and spectra variations are smaller than those of non-DLC-FCLEDs. The DLC-FCLED provides high efficiency and high stability performance for high-power and high-temperature applications.

  11. An integrated circuit with transmit beamforming flip-chip bonded to a 2-D CMUT array for 3-D ultrasound imaging.

    Science.gov (United States)

    Wygant, Ira O; Jamal, Nafis S; Lee, Hyunjoo J; Nikoozadeh, Amin; Oralkan, Omer; Karaman, Mustafa; Khuri-Yakub, Butrus T

    2009-10-01

    State-of-the-art 3-D medical ultrasound imaging requires transmitting and receiving ultrasound using a 2-D array of ultrasound transducers with hundreds or thousands of elements. A tight combination of the transducer array with integrated circuitry eliminates bulky cables connecting the elements of the transducer array to a separate system of electronics. Furthermore, preamplifiers located close to the array can lead to improved receive sensitivity. A combined IC and transducer array can lead to a portable, high-performance, and inexpensive 3-D ultrasound imaging system. This paper presents an IC flip-chip bonded to a 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array for 3-D ultrasound imaging. The IC includes a transmit beamformer that generates 25-V unipolar pulses with programmable focusing delays to 224 of the 256 transducer elements. One-shot circuits allow adjustment of the pulse widths for different ultrasound transducer center frequencies. For receiving reflected ultrasound signals, the IC uses the 32-elements along the array diagonals. The IC provides each receiving element with a low-noise 25-MHz-bandwidth transimpedance amplifier. Using a field-programmable gate array (FPGA) clocked at 100 MHz to operate the IC, the IC generated properly timed transmit pulses with 5-ns accuracy. With the IC flip-chip bonded to a CMUT array, we show that the IC can produce steered and focused ultrasound beams. We present 2-D and 3-D images of a wire phantom and 2-D orthogonal cross-sectional images (Bscans) of a latex heart phantom.

  12. A Corrosion Investigation of Solder Candidates for High-Temperature Applications

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Ambat, Rajan

    2009-01-01

    The step soldering approach is being employed in the Multi-Chip module (MCM) technology. High lead containing alloys is one of the solders currently being used in this approach. Au-Sn and Au-Ge based candidate alloys have been proposed as alternative solders for this application. In this work...

  13. SMT soldering handbook

    National Research Council Canada - National Science Library

    Strauss, Rudolf

    1998-01-01

    ... 3.2.1 Constituents, melting behaviour and mechanical properties 3.2.2 Composition of solders for use in electronics 3.2.3 Lead-free solders 3.2.4 Solder impurities The soldered joint 3.3.1 Solde...

  14. An ultra-small, low-power, all-optical flip-flop memory on a silicon chip

    DEFF Research Database (Denmark)

    Liu, Liu; Kumar, R.; Huybrechts, K.

    2010-01-01

    Ultra-small, low-power, all-optical switching and memory elements, such as all-optical flip-flops, as well as photonic integrated circuits of many such elements, are in great demand for all-optical signal buffering, switching and processing. Silicon-on-insulator is considered to be a promising......-flop working in a continuous-wave regime with an electrical power consumption of a few milliwatts, allowing switching in 60 ps with 1.8 fJ optical energy. The total power consumption and the device size are, to the best of our knowledge, the smallest reported to date at telecom wavelengths. This is also...

  15. Flip-chip integration of Si bare dies on polymeric substrates at low temperature using ICA vias made in dry film photoresist

    Science.gov (United States)

    Vásquez Quintero, Andrés; Briand, Danick; de Rooij, Nico F.

    2015-04-01

    In this paper, a low temperature flip-chip integration technique for Si bare dies is demonstrated on flexible PET substrates with screen-printed circuits. The proposed technique is based on patterned blind vias in dry film photoresist (DP) filled with isotropic conductive adhesive (ICA). The DP material serves to define the vias, to confine the ICA paste (80 µm-wide and potentially 25 µm-wide vias), as an adhesion layer to improve the mechanical robustness of the assembly, and to protect additional circuitry on the substrate. The technique is demonstrated using gold-bumped daisy chain chips (DCCs), with electrical vias resistances in the order to hundreds of milliohms, and peel/shear adhesion strengths of 0.7 N mm-1 and 3.2 MPa, respectively, (i.e. at 1.2 MPa of bonding pressure). Finally, the mechanical robustness to bending forces was optimized through flexural mechanics models by placing the neutral plane at the DCC/DP adhesive interface. The optimization was performed by reducing the Si thickness from 400 to 37 µm, and resulted in highly robust integrated assemblies withstanding 10 000 cycles of dynamic bending at 40 mm of radius, with relative changes in vias resistance lower than 20%. In addition, the electrical vias resistance and adhesion strengths were compared to samples integrated with anisotropic conductive adhesives (ACAs). Besides the low temperature and high integration resolution, the proposed method is compatible with large area fabrication and multilayer architectures on foil.

  16. Numerical analysis of light extraction enhancement of GaN-based thin-film flip-chip light-emitting diodes with high-refractive-index buckling nanostructures

    Science.gov (United States)

    Yue, Qing-Yang; Yang, Yang; Cheng, Zhen-Jia; Guo, Cheng-Shan

    2018-06-01

    In this work, the light extraction efficiency enhancement of GaN-based thin-film flip-chip (TFFC) light-emitting diodes (LEDs) with high-refractive-index (TiO2) buckling nanostructures was studied using the three-dimensional finite difference time domain method. Compared with 2-D photonic crystals, the buckling structures have the advantages of a random directionality and a broad distribution in periodicity, which can effectively extract the guided light propagating in all azimuthal directions over a wide spectrum. Numerical studies revealed that the light extraction efficiency of buckling-structured LEDs reaches 1.1 times that of triangular lattice photonic crystals. The effects of the buckling structure feature sizes and the thickness of the N-GaN layer on the light extraction efficiency for TFFC LEDs were also investigated systematically. With optimized structural parameters, a significant light extraction enhancement of about 2.6 times was achieved for TiO2 buckling-structured TFFC LEDs compared with planar LEDs.

  17. Performance Improvement of GaN-Based Flip-Chip White Light-Emitting Diodes with Diffused Nanorod Reflector and with ZnO Nanorod Antireflection Layer

    Directory of Open Access Journals (Sweden)

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The GaN-based flip-chip white light-emitting diodes (FCWLEDs with diffused ZnO nanorod reflector and with ZnO nanorod antireflection layer were fabricated. The ZnO nanorod array grown using an aqueous solution method was combined with Al metal to form the diffused ZnO nanorod reflector. It could avoid the blue light emitted out from the Mg-doped GaN layer of the FCWLEDs, which caused more blue light emitted out from the sapphire substrate to pump the phosphor. Moreover, the ZnO nanorod array was utilized as the antireflection layer of the FCWLEDs to reduce the total reflection loss. The light output power and the phosphor conversion efficiency of the FCWLEDs with diffused nanorod reflector and 250 nm long ZnO nanorod antireflection layer were improved from 21.15 mW to 23.90 mW and from 77.6% to 80.1% in comparison with the FCWLEDs with diffused nanorod reflector and without ZnO nanorod antireflection layer, respectively.

  18. Flipped Learning

    DEFF Research Database (Denmark)

    Holmboe, Peter; Hachmann, Roland

    I FLIPPED LEARNING – FLIP MED VIDEO kan du læse om, hvordan du som underviser kommer godt i gang med at implementere video i undervisning, der har afsæt i tankerne omkring flipped learning. Bogen indeholder fire dele: I Del 1 fokuserer vi på det metarefleksive i at tænke video ind i undervisningen...

  19. Light-extraction enhancement of GaN-based 395  nm flip-chip light-emitting diodes by an Al-doped ITO transparent conductive electrode.

    Science.gov (United States)

    Xu, Jin; Zhang, Wei; Peng, Meng; Dai, Jiangnan; Chen, Changqing

    2018-06-01

    The distinct ultraviolet (UV) light absorption of indium tin oxide (ITO) limits the performance of GaN-based near-UV light-emitting diodes (LEDs). Herein, we report an Al-doped ITO with enhanced UV transmittance and low sheet resistance as the transparent conductive electrode for GaN-based 395 nm flip-chip near-UV LEDs. The thickness dependence of optical and electrical properties of Al-doped ITO films is investigated. The optimal Al-doped ITO film exhibited a transmittance of 93.2% at 395 nm and an average sheet resistance of 30.1  Ω/sq. Meanwhile, at an injection current of 300 mA, the forward voltage decreased from 3.14 to 3.11 V, and the light output power increased by 13% for the 395 nm near-UV flip-chip LEDs with the optimal Al-doped ITO over those with pure ITO. This Letter provides a simple and repeatable approach to further improve the light extraction efficiency of GaN-based near-UV LEDs.

  20. Embeded photonic crystal at the interface of p-GaN and Ag reflector to improve light extraction of GaN-based flip-chip light-emitting diode

    International Nuclear Information System (INIS)

    Zhen, Aigong; Ma, Ping; Zhang, Yonghui; Guo, Enqing; Tian, Yingdong; Liu, Boting; Guo, Shikuan; Shan, Liang; Wang, Junxi; Li, Jinmin

    2014-01-01

    In this experiment, a flip-chip light-emitting diode with photonic crystal was fabricated at the interface of p-GaN and Ag reflector via nanospheres lithography technique. In this structure, photonic crystal could couple with the guide-light efficiently by reason of the little distance between photonic crystal and active region. The light output power of light emitting diode with embedded photonic crystal was 1.42 times larger than that of planar flip-chip light-emitting diode. Moreover, the embedded photonic crystal structure makes the far-field divergence angle decreased by 18° without spectra shift. The three-dimensional finite difference time domain simulation results show that photonic crystal could improve the light extraction, and enhance the light absorption caused by Ag reflector simultaneously, because of the roughed surface. The depth of photonic crystal is the key parameter affecting the light extraction and absorption. Light extraction efficiency increases with the depth photonic crystal structure rapidly, and reaches the maximum at the depth 80 nm, beyond which light extraction decrease drastically

  1. Flipping Excel

    Science.gov (United States)

    Frydenberg, Mark

    2013-01-01

    The "flipped classroom" model has become increasingly popular in recent years as faculty try new ways to engage students in the classroom. In a flipped classroom setting, students review the lecture online prior to the class session and spend time in class working on problems or exercises that would have been traditionally assigned as…

  2. Flipped Learning

    DEFF Research Database (Denmark)

    Hachmann, Roland; Holmboe, Peter

    arbejde med faglige problemstillinger gennem problembaserede og undersøgende didaktiske designs. Flipped Learning er dermed andet og mere end at distribuere digitale materialer til eleverne forud for undervisning. Flipped Learning er i lige så høj grad et syn på, hvordan undervisning med digitale medier...

  3. Flipped classroom

    DEFF Research Database (Denmark)

    Skov, Tobias Kidde; Jørgensen, Søren

    2016-01-01

    Artiklen beskriver Flipped Classroom som et didaktisk princip, der kan være med til at organisere og tilrettelægge en undervisning, med fokus på forskellige læringsformer. Det handler om at forstå Flipped Classroom som en opdeling i 2 faser og 3 led, som samlet set skaber en didaktisk organisering....

  4. Current density redistribution from no current crowding to current crowding in Pb-free solder joints with an extremely thick Cu layer

    International Nuclear Information System (INIS)

    Han, Jung Kyu; Choi, Daechul; Fujiyoshi, Masaru; Chiwata, Nobuhiko; Tu, King-Ning

    2012-01-01

    In order to remove the effect of current crowding on electromigration, thick Cu under-bump metallization has been widely adopted in the electronics industry. Three-dimensional (3-D) integrated circuits, using through Si via Cu column interconnects, is being developed, and it seems that current crowding may not be a reliability issue. However, statistical experiments and 3-D finite element simulation indicate that there is a transition from no current crowding to current crowding, caused by void growth at the cathode. An analysis of the electromigration-induced failure mechanism in solder joints having a very thick Cu layer is presented. It is a unique failure mechanism, different from that in flip chip technology. Moreover, the study of marker displacement shows two different stages of drift velocity, which clearly demonstrates the back-stress effect and the development of compressive stress.

  5. Flipped Physics

    Science.gov (United States)

    Kettle, Maria

    2013-01-01

    This paper defines flipped learning and then examines its practical implementation in AS and A2 level physics classes, that is, classes for 16-18 year olds. The effect of this teaching style on student learning behaviour and its impact on test results are evaluated. The paper recounts the difficulties of implementing it and evaluates student…

  6. Flipping qubits

    International Nuclear Information System (INIS)

    Martini De, F.; Sciarrino, F.; Sias, C.; Buzek, V.

    2003-01-01

    On a classical level the information can be represented by bits, each of which can be either 0 or 1. Quantum information, on the other hand, consists of qubits which can be represented as two-level quantum systems with one level labeled |0> and the other |1>. Unlike bits, qubits cannot only be in one of the two levels, but in any superposition of them as well. This superposition principle makes quantum information fundamentally different from its classical counterpart. One of the most striking difference between the classical and quantum information is as follows: it is not a problem to flip a classical bit, i.e., to change the value of a bit, a 0 to a 1 and vice versa. This is accomplished by a NOT gate. Flipping a qubit, however, is another matter: there exists the fundamental bound which prohibits to flip a qubit prepared in an arbitrary state |Ψ>=α|0> and to obtain the state |Ψ T >=β*|0>-α*|1> which is orthogonal to it, i.e., T |Ψ>=0. We experimentally realize the best possible approximation of the qubit flipping that achieves bounds imposed by complete positivity of quantum mechanics

  7. Flipped physics

    International Nuclear Information System (INIS)

    Nanopoulos, D.V.

    1991-01-01

    This paper is a revamp of a flipped SU(5) x U(1) model derived from the heterotic superstring. The author assumes that the reader is familiar with the general structure of the flipped SU(5) x U(1) model, either in its (pointlike) field theory form, or its stringy derivation. Ideally, one would like to derive directly from the superstring the standard model SU(3) x SU(2) x U(1), without possibly any extra structure (gauge or particle content). Well, this has been proven to be very difficult. Until now, always the standard model is accompanied with extra structure and usually one needs the ordinary Higgs mechanism to get rid of unwanted forms. This may happen at a superhigh energy scale (close to M Planck ) or at intermediate seals (10 13 --10 15 GeV). But if so, our original motivation of deriving directly the standard model from the superstring has been dispersed

  8. Fiscal 1998 achievement report on regional consortium research and development project. Venture business raising type regional consortium - Small business creation base type (Preparation of monodispersed spherical particles for solder materials for application to high density semiconductor packaging - 2nd year); 1998 nendo komitsudo handotai jisso no tame no tanbunsan kyukei handa ryushi no sakusei ni kansuru kenkyu seika hokokusho (dai 2 nendo)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Fine solder grains have been developed, spherical in shape, uniform in diameter, high in dimensional precision, and high in surface cleanliness, which are necessary for the establishment of next-generation technologies of flip chip bonding and ball grid array which are indispensable for high-density high-reliability packaging of electronic devices such as LSI (large scale integration). Results attained in fiscal 1998 are described. A pulse pressure aided orifice injection method was used. Monodispersed grains are prepared for the Pb-63Sn solder and Sn-3.5Ag lead-free solder. In the case of a 200{mu}m-large orifice, the grain diameter was controlled to fall in the range of 190-210{mu}m and the accuracy was not lower than {+-}6{mu}m. The main goal of this project has been accomplished now that these figures were attained without a sorting process and satisfy the most rigorous conditions currently proposed by the industrial circle involved. The flow of hot liquid out of the orifice and the splitting process of grains were clarified by thermal hydraulic analysis. It was found that grains split and fly not because of instability due to Rayleigh surface waves but because of their liberation from surface tension when equipped with critical kinetic energy. (NEDO)

  9. Scalable Manufacturing of Solderable and Stretchable Physiologic Sensing Systems.

    Science.gov (United States)

    Kim, Yun-Soung; Lu, Jesse; Shih, Benjamin; Gharibans, Armen; Zou, Zhanan; Matsuno, Kristen; Aguilera, Roman; Han, Yoonjae; Meek, Ann; Xiao, Jianliang; Tolley, Michael T; Coleman, Todd P

    2017-10-01

    Methods for microfabrication of solderable and stretchable sensing systems (S4s) and a scaled production of adhesive-integrated active S4s for health monitoring are presented. S4s' excellent solderability is achieved by the sputter-deposited nickel-vanadium and gold pad metal layers and copper interconnection. The donor substrate, which is modified with "PI islands" to become selectively adhesive for the S4s, allows the heterogeneous devices to be integrated with large-area adhesives for packaging. The feasibility for S4-based health monitoring is demonstrated by developing an S4 integrated with a strain gauge and an onboard optical indication circuit. Owing to S4s' compatibility with the standard printed circuit board assembly processes, a variety of commercially available surface mount chip components, such as the wafer level chip scale packages, chip resistors, and light-emitting diodes, can be reflow-soldered onto S4s without modifications, demonstrating the versatile and modular nature of S4s. Tegaderm-integrated S4 respiration sensors are tested for robustness for cyclic deformation, maximum stretchability, durability, and biocompatibility for multiday wear time. The results of the tests and demonstration of the respiration sensing indicate that the adhesive-integrated S4s can provide end users a way for unobtrusive health monitoring. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Soldering of Nanotubes onto Microelectrodes

    DEFF Research Database (Denmark)

    Madsen, Dorte Nørgaard; Mølhave, Kristian; Mateiu, Ramona Valentina

    2003-01-01

    Suspended bridges of individual multiwalled carbon nanotubes were fabricated inside a scanning electron microscope by soldering the nanotube onto microelectrodes with highly conducting gold-carbon material. By the decomposition of organometallic vapor with the electron beam, metal-containing sold...... bonds were consistently found to be mechanically stronger than the carbon nanotubes.......Suspended bridges of individual multiwalled carbon nanotubes were fabricated inside a scanning electron microscope by soldering the nanotube onto microelectrodes with highly conducting gold-carbon material. By the decomposition of organometallic vapor with the electron beam, metal-containing solder...... bonds were formed at the intersection of the nanotube and the electrodes. Current-voltage curves indicated metallic conduction of the nanotubes, with resistances in the range of 9-29 kOmega. Bridges made entirely of the soldering material exhibited resistances on the order of 100 Omega, and the solder...

  11. Flipping HCI

    Directory of Open Access Journals (Sweden)

    C. Evans

    2016-08-01

    Full Text Available This paper presents the results of two studies involving “flipping the classroom”. Teaching material was delivered via interactive “e-lectures”, allowing face-to-face sessions to focus instead on practice. The e-lectures were designed according to standard usability principles coupled with recent research into the effect of interactivity on learning. The effectiveness of the use of e-lectures was then evaluated using an online survey. The results suggest that students prefer the flexibility offered by e-lectures compared to conventional lectures. The results contribute to our understanding of how this technology fits with face-to-face teaching in the digital age.

  12. Numerical and experimental investigation of GaN-based flip-chip light-emitting diodes with highly reflective Ag/TiW and ITO/DBR Ohmic contacts.

    Science.gov (United States)

    Zhou, Shengjun; Liu, Xingtong; Gao, Yilin; Liu, Yingce; Liu, Mengling; Liu, Zongyuan; Gui, Chengqun; Liu, Sheng

    2017-10-30

    We demonstrate two types of GaN-based flip-chip light-emitting diodes (FCLEDs) with highly reflective Ag/TiW and indium-tin oxide (ITO)/distributed Bragg reflector (DBR) p-type Ohmic contacts. We show that a direct Ohmic contact to p-GaN layer using pure Ag is obtained when annealed at 600°C in N 2 ambient. A TiW diffusion barrier layer covered onto Ag is used to suppress the agglomeration of Ag and thus maintain high reflectance of Ag during high temperature annealing process. We develop a strip-shaped SiO 2 current blocking layer beneath the ITO/DBR to alleviate current crowding occurring in FCLED with ITO/DBR. Owing to negligibly small spreading resistance of Ag, however, our combined numerical and experimental results show that the FCLED with Ag/TiW has a more favorable current spreading uniformity in comparison to the FCLED with ITO/DBR. As a result, the light output power of FCLED with Ag/TiW is 7.5% higher than that of FCLED with ITO/DBR at 350 mA. The maximum output power of the FCLED with Ag/TiW obtained at 305.6 A/cm 2 is 29.3% larger than that of the FCLED with ITO/DBR obtained at 278.9 A/cm 2 . The improvement appears to be due to the enhanced current spreading and higher optical reflectance provided by the Ag/TiW.

  13. On the problem of soldering refractory metals with silver-containing solders

    International Nuclear Information System (INIS)

    Anikeev, E.F.; Andryushchenko, V.I.; Chepelenko, V.N.; Batov, V.M.

    1981-01-01

    The processes of wetting, spreading and interphase interactions of copper-silver liquid alloys alloyed with Ni and Si, with niobium, tantalum, molybdenum, tungsten, 12Kh18N10T steel and nickel are studied. It has been determined that Ni or Si additions into the copper-silver solder improve the wetting and adhesion. When soldering with the alloy containing Ni additions, the strength of a soldered Joint grows with the increase of soldering duration while soldering with the alloy containing Si additions, the strength decreases. That is why Ni-containing solders are preferable for soldering thick-walled structures, and Si-containing solders - for thin-walled structures [ru

  14. Solder joint technology materials, properties, and reliability

    CERN Document Server

    Tu, King-Ning

    2007-01-01

    Solder joints are ubiquitous in electronic consumer products. The European Union has a directive to ban the use of Pb-based solders in these products on July 1st, 2006. There is an urgent need for an increase in the research and development of Pb-free solders in electronic manufacturing. For example, spontaneous Sn whisker growth and electromigration induced failure in solder joints are serious issues. These reliability issues are quite complicated due to the combined effect of electrical, mechanical, chemical, and thermal forces on solder joints. To improve solder joint reliability, the science of solder joint behavior under various driving forces must be understood. In this book, the advanced materials reliability issues related to copper-tin reaction and electromigration in solder joints are emphasized and methods to prevent these reliability problems are discussed.

  15. DomFLIP++

    International Nuclear Information System (INIS)

    Hendrysiak, W.; Raggl, A.; Slany, W.

    1996-01-01

    DomFLIP++ is the knowledge engineering module of the *FLIP++ project. *FLIP++ is a tool for optimizing multiple criteria problems. It uses fuzzy constraints to model optimizing criteria and applies algorithms such as Tabu search or genetic algorithms to the problems. DomFLIP++ is a C++ library. It allows the definition of new optimization problems. It helps a domain engineer to design the structure of a new problem. However, there is a domain independent interface to other *FLIP++ modules such as OptiFLIP++, DynaFLIP++, and InterFLIP++. After each iteration in the optimization process, the considered instantiations of the problem are evaluated. Each evaluation produces a list of violated constraints. For each constraint in further iterations of the optimization. A domain can be fine-tuned through modifications of constraints, through editing their repair lists, and through change in the optimizing parameters. A well-tuned domain can be successfully applied for optimization. Object-oriented design and implementation makes this module easy to modify and to reuse. Definition of new domains, system extensions with new optimizing algorithms, and definition of specific domain-dependent repair steps can be done efficiently. DomFLIP++ is tested on real-world example, namely scheduling the steel plant LD3 in Linz, Austria

  16. The flipped classroom

    DEFF Research Database (Denmark)

    Triantafyllou, Evangelia

    2015-01-01

    One of the novel ideas in teaching that heavily relies on current technology is the “flipped classroom” approach. In a flipped classroom the traditional lecture and homework sessions are inverted. Students are provided with online material in order to gain necessary knowledge before class, while...... class time is devoted to clarifications and application of this knowledge. The hypothesis is that there could be deep and creative discussions when teacher and students physically meet. This paper presents design considerations for flipped classrooms, and discusses how Moodle can facilitate...... with a discussion of the opportunities and challenges when implementing the flipped model in a virtual learning environment (VLE) like Moodle....

  17. Flipped Classroom Approach

    Directory of Open Access Journals (Sweden)

    Fezile Ozdamli

    2016-07-01

    Full Text Available Flipped classroom is an active, student-centered approach that was formed to increase the quality of period within class. Generally this approach whose applications are done mostly in Physical Sciences, also attracts the attention of educators and researchers in different disciplines recently. Flipped classroom learning which wide-spreads rapidly in the world, is not well recognized in our country. That is why the aim of study is to attract attention to its potential in education field and provide to make it recognize more by educators and researchers. With this aim, in the study what flipped classroom approach is, flipped classroom technology models, its advantages and limitations were explained.

  18. Handbook of machine soldering SMT and TH

    CERN Document Server

    Woodgate, Ralph W

    1996-01-01

    A shop-floor guide to the machine soldering of electronics Sound electrical connections are the operational backbone of every piece of electronic equipment-and the key to success in electronics manufacturing. The Handbook of Machine Soldering is dedicated to excellence in the machine soldering of electrical connections. Self-contained, comprehensive, and down-to-earth, it cuts through jargon, peels away outdated notions, and presents all the information needed to select, install, and operate machine soldering equipment. This fully updated and revised volume covers all of the new technologies and processes that have emerged in recent years, most notably the use of surface mount technology (SMT). Supplemented with 200 illustrations, this thoroughly accessible text Describes reflow and wave soldering in detail, including reflow soldering of SMT boards and the use of nitrogen blankets * Explains the setup, operation, and maintenance of a variety of soldering machines * Discusses theory, selection, and control met...

  19. Flipped Classroom, active Learning?

    DEFF Research Database (Denmark)

    Andersen, Thomas Dyreborg; Levinsen, Henrik; Philipps, Morten

    2015-01-01

    Action research is conducted in three physics classes over a period of eighteen weeks with the aim of studying the effect of flipped classroom on the pupils agency and learning processes. The hypothesis is that flipped classroom teaching will potentially allocate more time to work actively...

  20. Flipped Classroom Approach

    Science.gov (United States)

    Ozdamli, Fezile; Asiksoy, Gulsum

    2016-01-01

    Flipped classroom is an active, student-centered approach that was formed to increase the quality of period within class. Generally this approach whose applications are done mostly in Physical Sciences, also attracts the attention of educators and researchers in different disciplines recently. Flipped classroom learning which wide-spreads rapidly…

  1. Flipping Freshman Mathematics

    Science.gov (United States)

    Zack, Laurie; Fuselier, Jenny; Graham-Squire, Adam; Lamb, Ron; O'Hara, Karen

    2015-01-01

    Our study compared a flipped class with a standard lecture class in four introductory courses: finite mathematics, precalculus, business calculus, and calculus 1. The flipped sections watched video lectures outside of class and spent time in class actively working on problems. The traditional sections had lectures in class and did homework outside…

  2. Flipped Learning in the Workplace

    Science.gov (United States)

    Nederveld, Allison; Berge, Zane L.

    2015-01-01

    Purpose: The purpose of this paper is to serve as a summary of resources on flipped learning for workplace learning professionals. A recent buzzword in the training world is "flipped". Flipped learning and the flipped classroom are hot topics that have emerged in K-12 education, made their way to the university and are now being noticed…

  3. Spectroscopic investigation of oxidized solder surfaces

    International Nuclear Information System (INIS)

    Song, Jenn-Ming; Chang-Chien, Yu-Chien; Huang, Bo-Chang; Chen, Wei-Ting; Shie, Chi-Rung; Hsu, Chuang-Yao

    2011-01-01

    Highlights: → UV-visible spectroscopy is successfully used to evaluate the degree of discoloring of solders. → The surface oxides of solders can also be identified by UV-visible absorption spectra. → The discoloration of solder surface can be correlated with optical characterization of oxides. → A strategy against discoloring by alloying was also suggested. - Abstract: For further understanding of the discoloration of solder surfaces due to oxidation during the assembly and operation of electronic devices, UV-vis and X-ray photoelectron spectroscopic analyses were applied to evaluate the degree of discoloring and identify the surface oxides. The decrease in reflectance of the oxidized solder surface is related to SnO whose absorption band is located within the visible region. A trace of P can effectively depress the discoloration of solders under both solid and semi-solid states through the suppression of SnO.

  4. Soldering of Mg Joints Using Zn-Al Solders

    Science.gov (United States)

    Gancarz, Tomasz; Berent, Katarzyna; Skuza, Wojciech; Janik, Katarzyna

    2018-04-01

    Magnesium has applications in the automotive and aerospace industries that can significantly contribute to greater fuel economy and environmental conservation. The Mg alloys used in the automotive industry could reduce mass by up to 70 pct, providing energy savings. However, alongside the advantages there are limitations and technological barriers to use Mg alloys. One of the advantages concerns phenomena occurring at the interface when joining materials investigated in this study, in regard to the effect of temperature and soldering time for pure Mg joints. Eutectic Zn-Al and Zn-Al alloys with 0.05 (wt pct) Li and 0.2 (wt pct) Na were used in the soldering process. The process was performed for 3, 5, and 8 minutes of contact, at temperatures of 425 °C, 450 °C, 475 °C, and 500 °C. Selected, solidified solder-substrate couples were cross-sectioned, and their interfacial microstructures were investigated by scanning electron microscopy. The experiment was designed to demonstrate the effect of time, temperature, and the addition of Li and Na on the kinetics of the dissolving Mg substrate. The addition of Li and Na to eutectic Zn-Al caused to improve mechanical properties. Higher temperatures led to reduced joint strength, which is caused by increased interfacial reaction.

  5. Flip Video for Dummies

    CERN Document Server

    Hutsko, Joe

    2010-01-01

    The full-color guide to shooting great video with the Flip Video camera. The inexpensive Flip Video camera is currently one of the hottest must-have gadgets. It's portable and connects easily to any computer to transfer video you shoot onto your PC or Mac. Although the Flip Video camera comes with a quick-start guide, it lacks a how-to manual, and this full-color book fills that void! Packed with full-color screen shots throughout, Flip Video For Dummies shows you how to shoot the best possible footage in a variety of situations. You'll learn how to transfer video to your computer and then edi

  6. Flipped Classroom Approach

    OpenAIRE

    Fezile Ozdamli; Gulsum Asiksoy

    2016-01-01

    Flipped classroom is an active, student-centered approach that was formed to increase the quality of period within class. Generally this approach whose applications are done mostly in Physical Sciences, also attracts the attention of educators and researchers in different disciplines recently. Flipped classroom learning which wide-spreads rapidly in the world, is not well recognized in our country. That is why the aim of study is to attract attention to its potential in education field and pr...

  7. Effects of PCB Pad Metal Finishes on the Cu-Pillar/Sn-Ag Micro Bump Joint Reliability of Chip-on-Board (COB) Assembly

    Science.gov (United States)

    Kim, Youngsoon; Lee, Seyong; Shin, Ji-won; Paik, Kyung-Wook

    2016-06-01

    While solder bumps have been used as the bump structure to form the interconnection during the last few decades, the continuing scaling down of devices has led to a change in the bump structure to Cu-pillar/Sn-Ag micro-bumps. Cu-pillar/Sn-Ag micro-bump interconnections differ from conventional solder bump interconnections in terms of their assembly processing and reliability. A thermo-compression bonding method with pre-applied b-stage non-conductive films has been adopted to form solder joints between Cu pillar/Sn-Ag micro bumps and printed circuit board vehicles, using various pad metal finishes. As a result, various interfacial inter-metallic compounds (IMCs) reactions and stress concentrations occur at the Cu pillar/Sn-Ag micro bumps joints. Therefore, it is necessary to investigate the influence of pad metal finishes on the structural reliability of fine pitch Cu pillar/Sn-Ag micro bumps flip chip packaging. In this study, four different pad surface finishes (Thin Ni ENEPIG, OSP, ENEPIG, ENIG) were evaluated in terms of their interconnection reliability by thermal cycle (T/C) test up to 2000 cycles at temperatures ranging from -55°C to 125°C and high-temperature storage test up to 1000 h at 150°C. The contact resistances of the Cu pillar/Sn-Ag micro bump showed significant differences after the T/C reliability test in the following order: thin Ni ENEPIG > OSP > ENEPIG where the thin Ni ENEPIG pad metal finish provided the best Cu pillar/Sn-Ag micro bump interconnection in terms of bump joint reliability. Various IMCs formed between the bump joint areas can account for the main failure mechanism.

  8. Nano-soldering to single atomic layer

    Science.gov (United States)

    Girit, Caglar O [Berkeley, CA; Zettl, Alexander K [Kensington, CA

    2011-10-11

    A simple technique to solder submicron sized, ohmic contacts to nanostructures has been disclosed. The technique has several advantages over standard electron beam lithography methods, which are complex, costly, and can contaminate samples. To demonstrate the soldering technique graphene, a single atomic layer of carbon, has been contacted, and low- and high-field electronic transport properties have been measured.

  9. Safer Soldering Guidelines and Instructional Resources

    Science.gov (United States)

    Love, Tyler S.; Tomlinson, Joel

    2018-01-01

    Soldering is a useful and necessary process for many classroom, makerspace, Fab Lab, technology and engineering lab, and science lab activities. As described in this article, soldering can pose many safety risks without proper engineering controls, standard operating procedures, and direct instructor supervision. There are many safety hazards…

  10. Features of soldering of molybdenum a lols

    International Nuclear Information System (INIS)

    Grishin, V.L.; Rybkin, B.V.; Cherkasov, A.F.

    1980-01-01

    Soldering features of complex-alloy molybdenum alloys were investigated in comparison with alloys based on solid solutions. Soldering features of heterogeneous molybdenum base alloys were investigated using samples of 0.5-1.O mm sheets with the strain of about 95% made of ingots which had been smelted in arc vacuum furnaces. The soldering of samples was carried out in 5x1O -5 mm Hg vacuum using different sources of heating: radiation, electron-ray and contact. It was shown that heat-resisting soldered joints of heterogeneous molybdenum alloys could be produced using zirconium and niobium base solders containing the most effective hardeners of the parent material (titanum, vanadium, tantalum, molybdenum, tungsten). To preserve high mechanical properties of heterogeneous alloys it was expedient to use for welding local heating sources which permitted to decrease considerably temperature- time conditions of the process

  11. SU(5): to flip or not to flip

    International Nuclear Information System (INIS)

    Nanopoulos, D.V.; Wisconsin Univ., Madison,

    1988-01-01

    Flipped SU(5) possesses some unique features as a grand unified theory: elegant missing partner mechanism, see-saw neutrino masses, no Higgs adjoints. This last property makes flipped SU(5) the only known grand unified theory derivable from 4-dimensional superstrings. When derived from the superstrings, flipped SU(5) possesses, in addition a hierarchical fermion mass spectrum. All these recent developments involving flipped SU(5) are discussed in a detailed but simple way, including phenomenological consequences at low energies

  12. FLIPPED LEARNING: PRACTICAL ASPECTS

    Directory of Open Access Journals (Sweden)

    Olena Kuzminska

    2016-03-01

    Full Text Available The article is devoted to issues of implementation of the flipped learning technology in the practice of higher education institutions. The article defines the principles of technology and a model of the educational process, it notes the need to establish an information support system. The article defines online platforms and resources; it describes recommendations for the design of electronic training courses and organization of the students in the process of implementing the proposed model, as well as tools for assessing its effectiveness. The article provides a description of flipped learning implementation scenario and formulates suggestions regarding the use of this model as a mechanism to improve the efficiency of the learning process in the ICT-rich environment of high school: use of learning management systems (LMS and personal learning environments (PLE of participants in a learning process. The article provides an example of implementation of the flipped learning model as a part of the Information Technologies course in the National University of Life and Environmental Sciences of Ukraine (NULES. The article gives examples of tasks, resources and services, results of students’ research activity, as well as an example of the personal learning network, established in the course of implementation of the flipped learning model and elements of digital student portfolios. It presents the results of the monitoring of learning activities and students’ feedback. The author describes cautions against the mass introduction of the flipped learning model without monitoring of readiness of the participants of the educational process for its implementation

  13. Photothermal effects of laser tissue soldering

    International Nuclear Information System (INIS)

    McNally, K.M.; Sorg, B.S.; Welch, A.J.; Dawes, J.M.; Owen, E.R.

    1999-01-01

    Low-strength anastomoses and thermal damage of tissue are major concerns in laser tissue welding techniques where laser energy is used to induce thermal changes in the molecular structure of the tissues being joined, hence allowing them to bond together. Laser tissue soldering, on the other hand, is a bonding technique in which a protein solder is applied to the tissue surfaces to be joined, and laser energy is used to bond the solder to the tissue surfaces. The addition of protein solders to augment tissue repair procedures significantly reduces the problems of low strength and thermal damage associated with laser tissue welding techniques. Investigations were conducted to determine optimal solder and laser parameters for tissue repair in terms of tensile strength, temperature rise and damage and the microscopic nature of the bonds formed. An in vitro study was performed using an 808 nm diode laser in conjunction with indocyanine green (ICG)-doped albumin protein solders to repair bovine aorta specimens. Liquid and solid protein solders prepared from 25% and 60% bovine serum albumin (BSA), respectively, were compared. The efficacy of temperature feedback control in enhancing the soldering process was also investigated. Increasing the BSA concentration from 25% to 60% greatly increased the tensile strength of the repairs. A reduction in dye concentration from 2.5mgml -1 to 0.25mgml -1 was also found to result in an increase in tensile strength. Increasing the laser irradiance and thus surface temperature resulted in an increased severity of histological injury. Thermal denaturation of tissue collagen and necrosis of the intimal layer smooth muscle cells increased laterally and in depth with higher temperatures. The strongest repairs were produced with an irradiance of 6.4Wcm -2 using a solid protein solder composed of 60% BSA and 0.25mgml -1 ICG. Using this combination of laser and solder parameters, surface temperatures were observed to reach 85±5 deg. C with a

  14. Solderability study of RABiTS-based YBCO coated conductors

    International Nuclear Information System (INIS)

    Zhang Yifei; Duckworth, Robert C.; Ha, Tam T.; Gouge, Michael J.

    2011-01-01

    Study examines the implication of solder and flux selection in YBCO splice joints. Focus is on commercially available RABiTS-based YBCO coated conductors. Solderability varied with solder and flux for three different stabilizations tested. Resistivity of stabilizer was dominant factor in splice joint resistance. Solder materials affected splice joint resistance when solderability was poor. The solderability of commercially available YBa 2 Cu 3 O 7-x (YBCO) coated conductors that were made from Rolling Assisted Biaxially Textured Substrates (RABiTS)-based templates was studied. The coated conductors, also known as second-generation (2G) high temperature superconductor (HTS) wires (in the geometry of flat tapes about 4 mm wide), were laminated with copper, brass, or stainless steel strips as stabilizers. To understand the factors that influence their solderability, surface profilometry and scanning electron microscopy were used to characterize the wire surfaces. The solderability of three solders, 52In48Sn, 67Bi33In, and 100In (wt.%), was evaluated using a standard test (IPC/ECA J-STD-002) and with two different commercial fluxes. It was found that the solderability varied with the solder and flux but the three different wires showed similar solderability for a fixed combination of solder and flux. Solder joints of the 2G wires were fabricated using the tools and the procedures recommended by the HTS wire manufacturer. The solder joints were made in a lap-joint geometry and with the superconducting sides of the two wires face-to-face. The electrical resistances of the solder joints were measured at 77 K, and the results were analyzed to qualify the soldering materials and evaluate the soldering process. It was concluded that although the selection of soldering materials affected the resistance of a solder joint, the resistivity of the stabilizer was the dominant factor.

  15. The constitutive response of three solder materials

    International Nuclear Information System (INIS)

    Perez-Bergquist, Alejandro G.; Cao Fang; Perez-Bergquist, Sara J.; Lopez, Mike F.; Trujillo, Carl P.; Cerreta, Ellen K.; Gray, George T.

    2012-01-01

    Highlights: ► The full constitutive response of three solder materials. ► Test temperatures from −196 °C to 60 °C and strain rates from 10 −3 to >10 3 s −1 . ► Substitutes for leaded solders from a mechanical/microstructural properties view. - Abstract: As increasing worldwide demand for portable consumer electronics drives development of smaller, faster, more powerful electronic devices, components in these devices must become smaller, more precise, and more robust. Often, failure of these devices comes as a result of failure of the package (i.e. when a mobile phone is dropped) and specifically comes as a result of failure of solder interconnects. As a result, stronger more reliable solder materials are needed. In this paper, the constitutive responses of three solder materials (Sn63Pb37, Sn62Pb36Ag2, and Sn96.5Ag3Cu0.5) are analyzed as a function of temperature (−196 °C to 60 °C) and strain rate (10 −3 to >10 3 s −1 ). The lead-free Sn96.5Ag3Cu0.5 possessed the highest yield stress of the three solders at all tested strain rates and temperatures, and all solder microstructures which displayed a mechanical response that was sensitive to temperature exhibited grain coarsening with increasing plastic strain, even at room temperature.

  16. The constitutive response of three solder materials

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Bergquist, Alejandro G., E-mail: alexpb@lanl.gov [Materials Science and Technology Division, Los Alamos National Laboratory, Mail Stop G755, Los Alamos, NM 87545 (United States); Cao Fang [Exxon Mobil Research and Engineering Company, Annadale, NJ 08801 (United States); Perez-Bergquist, Sara J.; Lopez, Mike F.; Trujillo, Carl P.; Cerreta, Ellen K.; Gray, George T. [Materials Science and Technology Division, Los Alamos National Laboratory, Mail Stop G755, Los Alamos, NM 87545 (United States)

    2012-05-25

    Highlights: Black-Right-Pointing-Pointer The full constitutive response of three solder materials. Black-Right-Pointing-Pointer Test temperatures from -196 Degree-Sign C to 60 Degree-Sign C and strain rates from 10{sup -3} to >10{sup 3} s{sup -1}. Black-Right-Pointing-Pointer Substitutes for leaded solders from a mechanical/microstructural properties view. - Abstract: As increasing worldwide demand for portable consumer electronics drives development of smaller, faster, more powerful electronic devices, components in these devices must become smaller, more precise, and more robust. Often, failure of these devices comes as a result of failure of the package (i.e. when a mobile phone is dropped) and specifically comes as a result of failure of solder interconnects. As a result, stronger more reliable solder materials are needed. In this paper, the constitutive responses of three solder materials (Sn63Pb37, Sn62Pb36Ag2, and Sn96.5Ag3Cu0.5) are analyzed as a function of temperature (-196 Degree-Sign C to 60 Degree-Sign C) and strain rate (10{sup -3} to >10{sup 3} s{sup -1}). The lead-free Sn96.5Ag3Cu0.5 possessed the highest yield stress of the three solders at all tested strain rates and temperatures, and all solder microstructures which displayed a mechanical response that was sensitive to temperature exhibited grain coarsening with increasing plastic strain, even at room temperature.

  17. The Flipped Journal Club.

    Science.gov (United States)

    Bounds, Richard; Boone, Stephen

    2018-01-01

    Educators struggle to develop a journal club format that promotes active participation from all levels of trainees. The explosion of social media compels residencies to incorporate the evaluation and application of these resources into evidence-based practice. We sought to design an innovative "flipped journal club" to achieve greater effectiveness in meeting goals and objectives among residents and faculty. Each journal club is focused on a specific clinical question based on a landmark article, a background article, and a podcast or blog post. With the "flipped" model, residents are assigned to prepare an in-depth discussion of one of these works based on their level of training. At journal club, trainees break into small groups and discuss their assigned readings with faculty facilitation. Following the small-group discussions, all participants convene to summarize key points. In redesigning our journal club, we sought to achieve specific educational outcomes, and improve participant engagement and overall impressions. Sixty-one residents at our emergency medicine program participated in the flipped journal club during the 2015-2016 academic year, with supervision by core faculty. Program evaluation for the flipped journal club was performed using an anonymous survey, with response rates of 70% and 56% for residents and faculty, respectively. Overall, 95% of resident respondents and 100% of faculty respondents preferred the flipped format. The "flipped journal club" hinges upon well-selected articles, incorporation of social media, and small-group discussions. This format engages all residents, holds learners accountable, and encourages greater participation among residents and faculty.

  18. Optimal parameters for laser tissue soldering

    Science.gov (United States)

    McNally-Heintzelman, Karen M.; Sorg, Brian S.; Chan, Eric K.; Welch, Ashley J.; Dawes, Judith M.; Owen, Earl R.

    1998-07-01

    Variations in laser irradiance, exposure time, solder composition, chromophore type and concentration have led to inconsistencies in published results of laser-solder repair of tissue. To determine optimal parameters for laser tissue soldering, an in vitro study was performed using an 808-nm diode laser in conjunction with an indocyanine green (ICG)- doped albumin protein solder to weld bovine aorta specimens. Liquid and solid protein solders prepared from 25% and 60% bovine serum albumin (BSA), respectively, were compared. The effects of laser irradiance and exposure time on tensile strength of the weld and temperature rise as well as the effect of hydration on bond stability were investigated. Optimum irradiance and exposure times were identified for each solder type. Increasing the BSA concentration from 25% to 60% greatly increased the tensile strength of the weld. A reduction in dye concentration from 2.5 mg/ml to 0.25 mg/ml was also found to result in an increase in tensile strength. The strongest welds were produced with an irradiance of 6.4 W/cm2 for 50 s using a solid protein solder composed of 60% BSA and 0.25 mg/ml ICG. Steady-state solder surface temperatures were observed to reach 85 plus or minus 5 degrees Celsius with a temperature gradient across the solid protein solder strips of between 15 and 20 degrees Celsius. Finally, tensile strength was observed to decrease significantly (20 to 25%) after the first hour of hydration in phosphate-buffered saline. No appreciable change was observed in the strength of the tissue bonds with further hydration.

  19. Flipped SO(10) model

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Nobuhiro; Yamashita, Toshifumi

    2003-08-14

    This Letter demonstrates that, as in flipped SU(5) models, doublet-triplet splitting is accomplished by a missing partner mechanism in flipped SO(10) models. The gauge group SO(10){sub F}xU(1){sub V'{sub F}} includes SU(2){sub E} gauge symmetry, which plays an important role in solving the supersymmetric (SUSY) flavor problem by introducing non-abelian horizontal gauge symmetry and anomalous U(1){sub A} gauge symmetry. The gauge group can be broken into the standard model gauge group by VEVs of only spinor fields; such models may be easier to derive than E{sub 6} models from superstring theory.

  20. Evaluation of flipped teaching

    OpenAIRE

    Henderson, K.; Hobbs, C.; Last, K.

    2017-01-01

    We report on our evaluation of flipping the classroom for two modules: a compulsory first year calculus module and an optional second year coding theory module taken by Mathe-matics students at the University of the West of England, Bristol (UWE). Flipped teaching is a change to the traditional lecture model used in universities for hundreds of years. In the traditional model the lecturer is in charge of the class and largely dictates the content and pace at which this is delivered. The idea ...

  1. Flipped SO(10)

    Energy Technology Data Exchange (ETDEWEB)

    Tamvakis, K.

    1988-01-28

    We construct an N=1 supersymmetric SO(10) GUT broken down to SU(3)c x SU(2)/sub L/ x U(1)/sub ..gamma../ with an intermediate flipped SU(5) x U(1)/sub chi/ gauge symmetry. A solution to the triplet-doublet mass-splitting problem is proposed in terms of a non-minimal missing-partner mechanism.

  2. Flipping the Classroom Revisited

    Science.gov (United States)

    Riendeau, Diane

    2013-02-01

    I received many emails following the first column on flipping the classroom. Many of my local colleagues also approached me at our physics alliance, Physics Northwest. Teachers are very interested in this new pedagogy. As I result, I wanted to share some more videos to inspire you.

  3. Investigation of Sn-Pb solder bumps of prototype photo detectors for the LHCb experiment

    CERN Document Server

    Delsante, M L; Arnau-Izquierdo, G

    2004-01-01

    The Large Hadron Collider (LHC) is now under construction at the European Organization for Nuclear Research (CERN). LHCb is one of the dedicated LHC experiments, allowing high energy proton-proton collisions to be exploited. This paper presents the results of the metallurgic studies carried out on Sn-Pb solder bumps of prototype vacuum photo detectors under development for LHCb, and in particular for the ring imaging Cherenkov-hybrid photo diode (RICH-HPD) project. These detectors encapsulate, in a vacuum tube, an assembly made of two silicon chips bonded together by a matrix of solder bumps. Each bump lies on a suitable system of under-bump metallic layers ensuring mechanical and electrical transition between the chip pad and the solder alloy. During manufacturing of the detector, bump-bonded (BB) assemblies are exposed to severe heat cycles up to 400 degree C inducing, in the present fabrication process, a clear degradation of electrical connectivity. Several investigations such as microstructural observati...

  4. The Flipped Journal Club

    Directory of Open Access Journals (Sweden)

    Richard Bounds

    2017-12-01

    Full Text Available Introduction Educators struggle to develop a journal club format that promotes active participation from all levels of trainees. The explosion of social media compels residencies to incorporate the evaluation and application of these resources into evidence-based practice. We sought to design an innovative “flipped journal club” to achieve greater effectiveness in meeting goals and objectives among residents and faculty. Methods Each journal club is focused on a specific clinical question based on a landmark article, a background article, and a podcast or blog post. With the “flipped” model, residents are assigned to prepare an in-depth discussion of one of these works based on their level of training. At journal club, trainees break into small groups and discuss their assigned readings with faculty facilitation. Following the small-group discussions, all participants convene to summarize key points. In redesigning our journal club, we sought to achieve specific educational outcomes, and improve participant engagement and overall impressions. Results Sixty-one residents at our emergency medicine program participated in the flipped journal club during the 2015–2016 academic year, with supervision by core faculty. Program evaluation for the flipped journal club was performed using an anonymous survey, with response rates of 70% and 56% for residents and faculty, respectively. Overall, 95% of resident respondents and 100% of faculty respondents preferred the flipped format. Conclusion The “flipped journal club” hinges upon well-selected articles, incorporation of social media, and small-group discussions. This format engages all residents, holds learners accountable, and encourages greater participation among residents and faculty.

  5. Thermomechanical fatigue life prediction for several solders

    Science.gov (United States)

    Wen, Shengmin

    Since solder connections operate at high homologous temperature, solders are high temperature materials. This feature makes their mechanical behavior and fatigue phenomena unique. Based on experimental findings, a physical damage mechanism is introduced for solders. The mechanism views the damage process as a series of independent local damage events characterized by the failure of individual grains, while the structural damage is the eventual percolation result of such local events. Fine's dislocation energy density concept and Mura's microcrack initiation theory are adopted to derive the fatigue formula for an individual grain. A physical damage metric is introduced to describe the material with damage. A unified creep and plasticity constitutive model is adopted to simulate the mechanical behavior of solders. The model is cast into a continuum damage mechanics framework to simulate material with damage. The model gives good agreement with the experimental results of 96.5Pb-3.5Sn and 96.5Sn-3.5Ag solders under uniaxial strain-controlled cyclic loading. The model is convenient for implementation into commercial computational packages. Also presented is a fatigue theory with its failure criterion for solders based on physical damage mechanism. By introducing grain orientation into the fatigue formula, an m-N curve (m is Schmid factor) at constant loading condition is suggested for fatigue of grains with different orientations. A solder structure is defined as fatigued when the damage metric reaches a critical threshold, since at this threshold the failed grains may form a cluster and percolate through the structure according to percolation theory. Fatigue data of 96.5Pb-3.5Sn solder bulk specimens under various uniaxial tension tests were analyzed. Results show that the theory gives consistent predictions under broad conditions, while inelastic strain theory does not. The theory is anisotropic with no size limitation to its application, which could be suitable for

  6. FLIPPED LEARNING: PRACTICAL ASPECTS

    OpenAIRE

    Olena Kuzminska

    2016-01-01

    The article is devoted to issues of implementation of the flipped learning technology in the practice of higher education institutions. The article defines the principles of technology and a model of the educational process, it notes the need to establish an information support system. The article defines online platforms and resources; it describes recommendations for the design of electronic training courses and organization of the students in the process of implementing the proposed model,...

  7. The Flipped Journal Club

    OpenAIRE

    Bounds, Richard; Boone, Stephen

    2018-01-01

    Introduction: Educators struggle to develop a journal club format that promotes active participation from all levels of trainees. The explosion of social media compels residencies to incorporate the evaluation and application of these resources into evidence-based practice. We sought to design an innovative “flipped journal club” to achieve greater effectiveness in meeting goals and objectives among residents and faculty. Methods: Each journal club is focused o...

  8. High temperature soldering of graphite

    International Nuclear Information System (INIS)

    Anikin, L.T.; Kravetskij, G.A.; Dergunova, V.S.

    1977-01-01

    The effect is studied of the brazing temperature on the strength of the brazed joint of graphite materials. In one case, iron and nickel are used as solder, and in another, molybdenum. The contact heating of the iron and nickel with the graphite has been studied in the temperature range of 1400-2400 ged C, and molybdenum, 2200-2600 deg C. The quality of the joints has been judged by the tensile strength at temperatures of 2500-2800 deg C and by the microstructure. An investigation into the kinetics of carbon dissolution in molten iron has shown that the failure of the graphite in contact with the iron melt is due to the incorporation of iron atoms in the interbase planes. The strength of a joint formed with the participation of the vapour-gas phase is 2.5 times higher than that of a joint obtained by graphite recrystallization through the carbon-containing metal melt. The critical temperatures are determined of graphite brazing with nickel, iron, and molybdenum interlayers, which sharply increase the strength of the brazed joint as a result of the formation of a vapour-gas phase and deposition of fine-crystal carbon

  9. Microstructure evolution and thermomechanical fatigue of solder materials

    NARCIS (Netherlands)

    Matin, M.A.

    2005-01-01

    The microelectronics industry is confronted with the new challenge to produce joints with lead-free solder materials replacing classical tin-lead solders in devices used in many fields (e.g. consumer electronics, road transport, aviation, space-crafts, telecommunication). In service, solder

  10. Efforts to Develop a 300°C Solder

    Energy Technology Data Exchange (ETDEWEB)

    Norann, Randy A [Perma Works LLC

    2015-01-25

    This paper covers the efforts made to find a 300°C electrical solder solution for geothermal well monitoring and logging tools by Perma Works LLC. This paper covers: why a high temperature solder is needed, what makes for a good solder, testing flux, testing conductive epoxy and testing intermetallic bonds. Future areas of research are suggested.

  11. Flipped Learning, Flipped Satisfaction, Getting the Balance Right

    Science.gov (United States)

    Swinburne, Rosemary Fisher; Ross, Bella; LaFerriere, Richard; Maritz, Alex

    2017-01-01

    This paper explores students' perceptions of their learning outcomes, engagement, and satisfaction with a technology-facilitated flipped approach in a third-year core subject at an Australian university during 2014. In this pilot study, findings reveal that students preferred the flipped approach to the traditional face-to-face delivery and…

  12. A novel method for direct solder bump pull testing using lead-free solders

    Science.gov (United States)

    Turner, Gregory Alan

    This thesis focuses on the design, fabrication, and evaluation of a new method for testing the adhesion strength of lead-free solders, named the Isotraction Bump Pull method (IBP). In order to develop a direct solder joint-strength testing method that did not require customization for different solder types, bump sizes, specific equipment, or trial-and-error, a combination of two widely used and accepted standards was created. First, solder bumps were made from three types of lead free solder were generated on untreated copper PCB substrates using an in-house fabricated solder bump-on-demand generator, Following this, the newly developed method made use of a polymer epoxy to encapsulate the solder bumps that could then be tested under tension using a high precision universal vertical load machine. The tests produced repeatable and predictable results for each of the three alloys tested that were in agreement with the relative behavior of the same alloys using other testing methods in the literature. The median peak stress at failure for the three solders tested were 2020.52 psi, 940.57 psi, and 2781.0 psi, and were within one standard deviation of the of all data collected for each solder. The assumptions in this work that brittle fracture occurred through the Intermetallic Compound layer (IMC) were validated with the use of Energy-Dispersive X-Ray Spectrometry and high magnification of the fractured surface of both newly exposed sides of the test specimens. Following this, an examination of the process to apply the results from the tensile tests into standard material science equations for the fracture of the systems was performed..

  13. Adventures in Flipping College Algebra

    Science.gov (United States)

    Van Sickle, Jenna

    2015-01-01

    This paper outlines the experience of a university professor who implemented flipped learning in two sections of college algebra courses for two semesters. It details how the courses were flipped, what technology was used, advantages, challenges, and results. It explains what students do outside of class, what they do inside class, and discusses…

  14. Relationships in the Flipped Classroom

    Science.gov (United States)

    McCollum, Brett M.; Fleming, Cassidy L.; Plotnikoff, Kara M.; Skagen, Darlene N.

    2017-01-01

    This study examines the effectiveness of flipped classrooms in chemistry, and identifies relationships as a major factor impacting the success of flipped instruction methods. Examination of student interview data reveals factors that affect the development of peer-peer, peer-peer leader, and peer-expert relationships in firstyear general chemistry…

  15. Interface between Sn-Sb-Cu solder and copper substrate

    Energy Technology Data Exchange (ETDEWEB)

    Sebo, P., E-mail: Pavel.Sebo@savba.sk [Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Racianska 75, 831 02 Bratislava 3 (Slovakia); Svec, P. [Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava 45 (Slovakia); Faculty of Materials Science and Technology, Slovak University of Technology, J. Bottu 25, 917 24 Trnava (Slovakia); Janickovic, D.; Illekova, E. [Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava 45 (Slovakia); Plevachuk, Yu. [Ivan Franko National University, Department of Metal Physics, 79005 Lviv (Ukraine)

    2011-07-15

    Highlights: {yields} New lead-free solder materials based on Sn-Sb-Cu were designed and prepared. {yields} Melting and solidification temperatures of the solders have been determined. {yields} Cu-substrate/solder interaction has been analyzed and quantified. {yields} Phases formed at the solder-substrate interface have been identified. {yields} Composition and soldering atmospheres were correlated with joint strength. - Abstract: Influence of antimony and copper in Sn-Sb-Cu solder on the melting and solidification temperatures and on the microstructure of the interface between the solder and copper substrate after wetting the substrate at 623 K for 1800 s were studied. Microstructure of the interface between the solder and copper substrates in Cu-solder-Cu joints prepared at the same temperature for 1800 s was observed and shear strength of the joints was measured. Influence of the atmosphere - air with the flux and deoxidising N{sub 2} + 10H{sub 2} gas - was taken into account. Thermal stability and microstructure were studied by differential scanning calorimetry (DSC), light microscopy, scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD). Melting and solidification temperatures of the solders were determined. An interfacial transition zone was formed by diffusion reaction between solid copper and liquid solder. At the interface Cu{sub 3}Sn and Cu{sub 6}Sn{sub 5} phases arise. Cu{sub 3}Sn is adjacent to the Cu substrate and its thickness decreases with increasing the amount of copper in solder. Scallop Cu{sub 6}Sn{sub 5} phase is formed also inside the solder drop. The solid solution Sn(Sb) and SbSn phase compose the interior of the solder drop. Shear strength of the joints measured by push-off method decreases with increasing Sb concentration. Copper in the solder shows even bigger negative effect on the strength.

  16. A Hodge dual for soldered bundles

    International Nuclear Information System (INIS)

    Lucas, Tiago Gribl; Pereira, J G

    2009-01-01

    In order to account for all possible contractions allowed by the presence of the solder form, a generalized Hodge dual is defined for the case of soldered bundles. Although for curvature the generalized dual coincides with the usual one, for torsion it gives a completely new dual definition. Starting from the standard form of a gauge Lagrangian for the translation group, the generalized Hodge dual yields precisely the Lagrangian of the teleparallel equivalent of general relativity, and consequently also the Einstein-Hilbert Lagrangian of general relativity

  17. Visual detection of defects in solder joints

    Science.gov (United States)

    Blaignan, V. B.; Bourbakis, Nikolaos G.; Moghaddamzadeh, Ali; Yfantis, Evangelos A.

    1995-03-01

    The automatic, real-time visual acquisition and inspection of VLSI boards requires the use of machine vision and artificial intelligence methodologies in a new `frame' for the achievement of better results regarding efficiency, products quality and automated service. In this paper the visual detection and classification of different types of defects on solder joints in PC boards is presented by combining several image processing methods, such as smoothing, segmentation, edge detection, contour extraction and shape analysis. The results of this paper are based on simulated solder defects and a real one.

  18. Flipped GUT inflation

    OpenAIRE

    Ellis, John; Gonzalo, Tomás E.; Harz, Julia; Huang, Wei-Chih

    2015-01-01

    We analyse the prospects for constructing hybrid models of inflation that provide a dynamical realisation of the apparent closeness between the supersymmetric GUT scale and the possible scale of cosmological inflation. In the first place, we consider models based on the flipped SU(5)×U(1) gauge group, which has no magnetic monopoles. In one model, the inflaton is identified with a sneutrino field, and in the other model it is a gauge singlet. In both cases we find regions of the model paramet...

  19. Laser assisted soldering: microdroplet accumulation with a microjet device.

    Science.gov (United States)

    Chan, E K; Lu, Q; Bell, B; Motamedi, M; Frederickson, C; Brown, D T; Kovach, I S; Welch, A J

    1998-01-01

    We investigated the feasibility of a microjet to dispense protein solder for laser assisted soldering. Successive micro solder droplets were deposited on rat dermis and bovine intima specimens. Fixed laser exposure was synchronized with the jetting of each droplet. After photocoagulation, each specimen was cut into two halves at the center of solder coagulum. One half was fixed immediately, while the other half was soaked in phosphate-buffered saline for a designated hydration period before fixation (1 hour, 1, 2, and 7 days). After each hydration period, all tissue specimens were prepared for scanning electron microscopy (SEM). Stable solder coagulum was created by successive photocoagulation of microdroplets even after the soldered tissue exposed to 1 week of hydration. This preliminary study suggested that tissue soldering with successive microdroplets is feasible even with fixed laser parameters without active feedback control.

  20. Flipped GUT inflation

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, John [Theoretical Particle Physics and Cosmology Group, Department of Physics, King’s College London, Strand, London WC2R 2LS (United Kingdom); Theory Division, CERN, Route de Meyrin 385, 1217 Meyrin (Switzerland); Gonzalo, Tomás E.; Harz, Julia; Huang, Wei-Chih [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2015-03-23

    We analyse the prospects for constructing hybrid models of inflation that provide a dynamical realisation of the apparent closeness between the supersymmetric GUT scale and the possible scale of cosmological inflation. In the first place, we consider models based on the flipped SU(5)×U(1) gauge group, which has no magnetic monopoles. In one model, the inflaton is identified with a sneutrino field, and in the other model it is a gauge singlet. In both cases we find regions of the model parameter spaces that are compatible with the experimental magnitudes of the scalar perturbations, A{sub s}, and the tilt in the scalar perturbation spectrum, n{sub s}, as well as with an indicative upper limit on the tensor-to-scalar perturbation ratio, r. We also discuss embeddings of these models into SO(10), which is broken at a higher scale so that its monopoles are inflated away.

  1. Flipped dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, J.; Hagelin, J.S.; Kelley, S.; Nanopoulos, D.V.; Olive, K.A.

    1988-08-04

    We study candidates for dark matter in a minimal flipped SU(5) x U(1) supersymmetric GUT. Since the model has no R-parity, spin-1/2 supersymmetric partners of conventional particles mix with other neutral fermions including neutrinos, and can decay into them. The lighest particle which is predominantly a gaugino/higgsino mixture decays with a lifetime tau/sub chi/ approx. = 1-10/sup 9/ s. The model contains a scalar 'flaton' field whose coherent oscillations decay before cosmological nucleosynthesis, and whose pseudoscalar partner contributes negligibly to ..cap omega.. if it is light enough to survive to the present epoch. The fermionic 'flatino' partner of the flaton has a lifetime tau/sub PHI/ approx. = 10/sup 28/-10/sup 34/ yr and is a viable candiate for metastable dark matter with ..cap omega.. < or approx. 1.

  2. Flipped GUT inflation

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, John [Theoretical Particle Physics and Cosmology Group, Department of Physics, King' s College London, Strand, London WC2R 2LS (United Kingdom); Gonzalo, Tomás E.; Harz, Julia; Huang, Wei-Chih, E-mail: john.ellis@cern.ch, E-mail: tomas.gonzalo.11@ucl.ac.uk, E-mail: j.harz@ucl.ac.uk, E-mail: wei-chih.huang@ucl.ac.uk [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2015-03-01

    We analyse the prospects for constructing hybrid models of inflation that provide a dynamical realisation of the apparent closeness between the supersymmetric GUT scale and the possible scale of cosmological inflation. In the first place, we consider models based on the flipped SU(5)×U(1) gauge group, which has no magnetic monopoles. In one model, the inflaton is identified with a sneutrino field, and in the other model it is a gauge singlet. In both cases we find regions of the model parameter spaces that are compatible with the experimental magnitudes of the scalar perturbations, A{sub s}, and the tilt in the scalar perturbation spectrum, n{sub s}, as well as with an indicative upper limit on the tensor-to-scalar perturbation ratio, r. We also discuss embeddings of these models into SO(10), which is broken at a higher scale so that its monopoles are inflated away.

  3. A flipped 331 model

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca, Renato M.; Hirsch, Martin [AHEP Group, Instituto de Física Corpuscular, C.S.I.C./Universitat de València,Parc Científic de Paterna. Calle Catedrático José Beltrán,2 E-46980 Paterna (Valencia) (Spain)

    2016-08-01

    Models based on the extended SU(3){sub C}×SU(3){sub L}×U(1){sub X} (331) gauge group usually follow a common pattern: two families of left-handed quarks are placed in anti-triplet representations of the SU(3){sub L} group; the remaining quark family, as well as the left-handed leptons, are assigned to triplets (or vice-versa). In this work we present a flipped 331 model where this scheme is reversed: all three quark families are in the same representation and it is the lepton families which are discriminated by the gauge symmetry. We discuss fermion masses and mixing, as well as Z{sup ′} interactions, in a minimal model implementing this idea.

  4. Practical quantum coin flipping

    International Nuclear Information System (INIS)

    Pappa, Anna; Diamanti, Eleni; Chailloux, Andre; Kerenidis, Iordanis

    2011-01-01

    We show that in the unconditional security model, a single quantum strong coin flip with security guarantees that are strictly better than in any classical protocol is possible to implement with current technology. Our protocol takes into account all aspects of an experimental implementation, including losses, multiphoton pulses emitted by practical photon sources, channel noise, detector dark counts, and finite quantum efficiency. We calculate the abort probability when both players are honest, as well as the probability of one player forcing his desired outcome. For a channel length up to 21 km and commonly used parameter values, we can achieve honest abort and cheating probabilities that are better than in any classical protocol. Our protocol is, in principle, implementable using attenuated laser pulses, with no need for entangled photons or any other specific resources.

  5. Flipped GUT Inflation

    CERN Document Server

    Ellis, John; Harz, Julia; Huang, Wei-Chih

    2015-01-01

    We analyse the prospects for constructing hybrid models of inflation that provide a dynamical realisation of the apparent closeness between the supersymmetric GUT scale and the possible scale of cosmological inflation. In the first place, we consider models based on the flipped SU(5)$\\times$U(1) gauge group, which has no magnetic monopoles. In one model, the inflaton is identified with a sneutrino field, and in the other model it is a gauge singlet. In both cases we find regions of the model parameter spaces that are compatible with the experimental magnitudes of the scalar perturbations, $A_s$, and the tilt in the scalar perturbation spectrum, $n_s$, as well as with an indicative upper limit on the tensor-to-scalar perturbation ratio, $r$. We also discuss embeddings of these models into SO(10), which is broken at a higher scale so that its monopoles are inflated away.

  6. FLIP for FLAG model visualization

    Energy Technology Data Exchange (ETDEWEB)

    Wooten, Hasani Omar [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-11-15

    A graphical user interface has been developed for FLAG users. FLIP (FLAG Input deck Parser) provides users with an organized view of FLAG models and a means for efficiently and easily navigating and editing nodes, parameters, and variables.

  7. Processing and Characterization of NiTi Shape Memory Alloy Particle Reinforced Sn-In Solders

    National Research Council Canada - National Science Library

    Chung, Kohn C

    2006-01-01

    .... In previous work, it was proposed that reinforcement of solder by NiTi shape memory alloy particles to form smart composite solder reduces the inelastic strain of the solder and hence, may enhance...

  8. Spin flipping a stored polarized proton beam

    International Nuclear Information System (INIS)

    Caussyn, D.D.; Derbenev, Y.S.; Ellison, T.J.P.; Lee, S.Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Stephenson, E.J.; von Przewoski, B.; Blinov, B.B.; Chu, C.M.; Courant, E.D.; Crandell, D.A.; Kaufman, W.A.; Krisch, A.D.; Nurushev, T.S.; Phelps, R.A.; Ratner, L.G.; Wong, V.K.; Ohmori, C.

    1994-01-01

    We recently studied the spin flipping of a vertically polarized, stored 139-MeV proton beam. To flip the spin, we induced an rf depolarizing resonance by sweeping our rf solenoid magnet's frequency through the resonance frequency. With multiple spin flips, we found a polarization loss of 0.0000±0.0005 per spin flip under the best conditions; this loss increased significantly for small changes in the conditions. Minimizing the depolarization during each spin flip is especially important because frequent spin flipping could significantly reduce the systematic errors in stored polarized-beam experiments

  9. Effect of Solder Flux Residues on Corrosion of Electronics

    DEFF Research Database (Denmark)

    Hansen, Kirsten Stentoft; Jellesen, Morten Stendahl; Møller, Per

    2009-01-01

    Flux from ‘No Clean’ solder processes can cause reliability problems in the field due to aggressive residues, which may be electrical conducting or corrosive in humid environments. The solder temperature during a wave solder process is of great importance to the amount of residues left on a PCBA...... testing and use in the field, consequences and recommendations are given. Failures, caused by harsh[1] customer environments, are not covered in this paper....

  10. Mechanical properties of soldered joints of niobium base alloys

    International Nuclear Information System (INIS)

    Grishin, V.L.

    1980-01-01

    Mechanical properties of soldered joints of niobium alloys widely distributed in industry: VN3, VN4, VN5A, VN5AE, VN5AEP etc., 0.6-1.2 mm thick are investigated. It is found out that the usage of zirconium-vanadium, titanium-tantalum solders for welding niobium base alloys permits to obtain soldered joints with satisfactory mechanical properties at elevated temperatures

  11. Evaluation on the characteristics of tin-silver-bismuth solder

    Science.gov (United States)

    Xia, Z.; Shi, Y.; Chen, Z.

    2002-02-01

    Tin-silver-bismuth solder is characterized by its lower melting point, good wetting behavior, and good mechanical property for which it is expected to be a new lead-free solder to replace tin-lead solder. In this article, Sn-3.33Ag-4.83Bi solder was investigated concerning its physical, spreading, and mechanical properties under specific conditions. Cooling curves and DSC results showed that it was close to eutectic composition (m.p. 210° 212 °C). Coefficiency of thermal expansion (CTE) of this solder, between that of PCBs and copper substrates, was beneficial to alleviate the thermal mismatch of the substrates. It was also a good electrical and thermal conductor. Using a rosin-based, mildly activated (RMA) flux, a spreading test indicated that SnAgBi solder paste had good solderability. Meanwhile, the solder had high tensile strength and fracture energy. Its fracture mechanism was a mixture of ductile and brittle fracture morphology. The metallographic and EDAX analyses indicated that it was composed of a tin-based solid solution and some intermetallic compound (IMC) that could strengthen the substrate. However, these large needle-like IMCs would cut the substrate and this resulted in the decreasing of the toughness of the solder.

  12. To Flip or Not to Flip? An Exploratory Study Comparing Student Performance in Calculus I

    Science.gov (United States)

    Schroeder, Larissa B.; McGivney-Burelle, Jean; Xue, Fei

    2015-01-01

    The purpose of this exploratory, mixed-methods study was to compare student performance in flipped and non-flipped sections of Calculus I. The study also examined students' perceptions of the flipping pedagogy. Students in the flipped courses reported spending, on average, an additional 1-2 hours per week outside of class on course content.…

  13. Reliability Study of Solder Paste Alloy for the Improvement of Solder Joint at Surface Mount Fine-Pitch Components

    Directory of Open Access Journals (Sweden)

    Mohd Nizam Ab. Rahman

    2014-12-01

    Full Text Available The significant increase in metal costs has forced the electronics industry to provide new materials and methods to reduce costs, while maintaining customers’ high-quality expectations. This paper considers the problem of most electronic industries in reducing costly materials, by introducing a solder paste with alloy composition tin 98.3%, silver 0.3%, and copper 0.7%, used for the construction of the surface mount fine-pitch component on a Printing Wiring Board (PWB. The reliability of the solder joint between electronic components and PWB is evaluated through the dynamic characteristic test, thermal shock test, and Taguchi method after the printing process. After experimenting with the dynamic characteristic test and thermal shock test with 20 boards, the solder paste was still able to provide a high-quality solder joint. In particular, the Taguchi method is used to determine the optimal control parameters and noise factors of the Solder Printer (SP machine, that affects solder volume and solder height. The control parameters include table separation distance, squeegee speed, squeegee pressure, and table speed of the SP machine. The result shows that the most significant parameter for the solder volume is squeegee pressure (2.0 mm, and the solder height is the table speed of the SP machine (2.5 mm/s.

  14. The Flipped Classroom in Counselor Education

    Science.gov (United States)

    Moran, Kristen; Milsom, Amy

    2015-01-01

    The flipped classroom is proposed as an effective instructional approach in counselor education. An overview of the flipped-classroom approach, including advantages and disadvantages, is provided. A case example illustrates how the flipped classroom can be applied in counselor education. Recommendations for implementing or researching flipped…

  15. The Marriage of Constructivism and Flipped Learning

    Science.gov (United States)

    Chang, Sau Hou

    2016-01-01

    This report talks about how a constructivist teacher used flipped learning in a college class. To illustrate how to use flipped learning in a constructivist classroom, examples were given with the four pillars of F-L-I-P: Flexible environment, learning culture, intentional content, and professional educator.

  16. A Flipped Classroom Redesign in General Chemistry

    Science.gov (United States)

    Reid, Scott A.

    2016-01-01

    The flipped classroom continues to attract significant attention in higher education. Building upon our recent parallel controlled study of the flipped classroom in a second-term general chemistry course ("J. Chem. Educ.," 2016, 93, 13-23), here we report on a redesign of the flipped course aimed at scaling up total enrollment while…

  17. Flipping a Calculus Class: One Instructor's Experience

    Science.gov (United States)

    Palmer, Katrina

    2015-01-01

    This paper describes one instructor's experiences during a year of flipping four calculus classes. The first exploration attempts to understand student expectations of a math class and their preference towards a flipped classroom. The second examines success of students from a flipped classroom, and the last investigates relationships with student…

  18. Laser-activated protein solder for peripheral nerve repair

    Science.gov (United States)

    Trickett, Rodney I.; Lauto, Antonio; Dawes, Judith M.; Owen, Earl R.

    1995-05-01

    A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.

  19. Soldering of copper-clad niobium--titanium superconductor composite

    International Nuclear Information System (INIS)

    Moorhead, A.J.; Woodhouse, J.J.; Easton, D.S.

    1977-04-01

    When superconductivity is applied to various electrical devices, the joining of the superconducting material and the performance of the joints are generally crucial to the successful operation of the system. Although many techniques are being considered for joining composite superconductors, soldering is the most common. We determined the wetting and flow behavior of various solder and flux combinations on a copper-clad Nb-Ti composite, developed equipment and techniques for soldering and inspection of lap joints, and determined the shear strength of joints at temperatures down to -269 0 C (4 0 K). We studied 15 solders and 17 commercial and experimental fluxes in the wettability and flow tests. A resistance unit was built for soldering test specimens. A series of samples soldered with 80 Pb-20 Sn, 83 Pb-15 Sn-2 Sb, 97.5 Pb-1.5 Ag-1 Sn, 80 In-15 Pb-5 Ag, or 25 In-37.5 Pb-37.5 Sn (wt percent) was inspected by three nondestructive techniques. Through-transmission ultrasound gave the best correlation with nonbond areas revealed in peel tests. Single-lap shear specimens soldered with 97.5 Pb-1.5 Ag-1 Sn had the highest strength (10.44 ksi, 72 MPa) and total elongation (0.074 in., 1.88 mm) at -269 0 C (4 0 K) of four solders tested

  20. Intersecting Branes Flip SU(5)

    CERN Document Server

    Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John

    2002-01-01

    Within a toroidal orbifold framework, we exhibit intersecting brane-world constructions of flipped SU(5) \\times U(1) GUT models with various numbers of generations, other chiral matter representations and Higgs representations. We exhibit orientifold constructions with integer winding numbers that yield 8 or more conventional SU(5) generations, and orbifold constructions with fractional winding numbers that yield flipped SU(5) \\times U(1) models with just 3 conventional generations. Some of these models have candidates for the 5 and {\\bar 5} Higgs representations needed for electroweak symmetry breaking, but not for the 10 and {\\bar 10} representations needed for GUT symmetry breaking, or vice-versa.

  1. Flipped Learning fra et elevperspektiv

    DEFF Research Database (Denmark)

    Holmboe, Peter; Hachmann, Roland

    2016-01-01

    Antologi er et resultat af et toårigt udviklingsprojekt om Flipped Learning baseret på et samarbejde mellem IT-Center Fyn og Region Syddanmark. Bidraget her præsenterer en række overvejelser, vi har gjort os på baggrund af observationer af undervisning og interviews med elever i projektet. Vores...... overordnede undersøgelsesspørgsmål var: "Hvilke forhold i undervisning og læringsmiljø fremme hhv. begrænser elevens opfattelse af mening og fagligt udbytte i et Flipped Learning design?"....

  2. Integration of environmentally compatible soldering technologies for waste minimization

    International Nuclear Information System (INIS)

    Hosking, F.M.

    1992-01-01

    There has been a concentrated effort throughout the international microelectronics industry to phase out chlorofluorocarbon (CFC) materials and alleviate the serious problem of ozone depletion created by the release of CFCS. The development of more environmentally compatible manufacturing technologies is the cornerstone of this effort. Alternative materials and processes for cleaning and soldering have received special attention. Electronic. soldering typically utilizes rosin-based fluxes to promote solder wettability. Flux residues must be removed from the soldered parts when high product reliability is essential. Halogenated or CFC solvents have been the principle chemicals used to clean the residues. With the accelerated push to eliminate CFCs in the US by 1995, CFC-free solvents, aqueous-based cleaning, water soluble or ''no clean'' fluxes, and fluxless soldering technologies are being developed and quickly integrated into manufacturing practice. Sandia's Center for Solder Science and Technology has been ch g a variety of fluxless and alternative soldering technologies for DOE's waste minimization program. The work has focused on controlled atmosphere, laser, and ultrasonic fluxless soldering, protective metallic and organic coatings, and fluxes which have water soluble or low solids-based chemistries. With the increasing concern that Pb will also be banned from electronic soldering, Sandia has been characterizing the wetting, aging, and mechanical properties of Pb-fire solder alloys. The progress of these integrated studies will be discussed. Their impact on environmentally compatible manufacturing will be emphasized. Since there is no universal solution to the various environmental, safety, and health issues which currently face industry, the proposed technologies offer several complementary materials and processing options from which one can choose

  3. Microstructurally Adaptive Constitutive Relations and Reliability Assessment Protocols for Lead Free Solder

    Science.gov (United States)

    2015-05-05

    under bump metallurgy and solder joint geometry on Sn grain morphology in Pb free solder joints were examined. SnAgCu solder joints were examined for...free solder interconnects”, Sci. Technol. Weld . Join. 13, 732 (2008). [3.25] Terashima, S., Takahama, K., Nozaki, M., and Tanaka, M. Recrystallization

  4. Characterization of lead-free solders for electronic packaging

    Science.gov (United States)

    Ma, Hongtao

    The characterization of lead-free solders, especially after isothermal aging, is very important in order to accurately predict the reliability of solder joints. However, due to lack of experimental testing standards and the high homologous temperature of solder alloys (Th > 0.5T m even at room temperature), there are very large discrepancies in both the tensile and creep properties provided in current databases for both lead-free and Sn-Pb solder alloys. In this research, mechanical measurements of isothermal aging effects and the resulting changes in the materials behavior of lead-free solders were performed. A novel specimen preparation procedure was developed where the solder uniaxial test specimens are formed in high precision rectangular cross-section glass tubes using a vacuum suction process. Using specimens fabricated with the developed procedure, isothermal aging effects and viscoplastic material behavior evolution have been characterized for 95.5Sn-4.0Ag-0.5Cu (SAC405) and 96.5Sn-3.0Ag-0.5Cu (SAC305) lead-free solders, which are commonly used as the solder ball alloy in lead-free BGAs and other components. Analogous tests were performed with 63Sn-37Pb eutectic solder samples for comparison purposes. Up to 40% reduction in tensile strength was observed for water quenched specimens after two months of aging at room temperature. Creep deformation also increased dramatically with increasing aging durations. Microstructural changes during room temperature aging were also observed and recorded for the solder alloys and correlated with the observed mechanical behavior changes. Aging effects at elevated temperatures for up to 6 months were also investigated. Thermal aging caused significant tensile strength loss and deterioration of creep deformation. The thermal aging results also showed that after an initial tensile strength drop, the Sn-Pb eutectic solder reached a relatively stable stage after 200 hours of aging. However, for SAC alloy, both the tensile and

  5. Some comments on flipped SU(5) times U(1) and flipped unification in general

    Energy Technology Data Exchange (ETDEWEB)

    Barr, S.M. (Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (US))

    1989-10-01

    A general group-theoretical discussion of flipped embeddings is given. In addition to the well-known flipped SU(5) and flipped SO(10), the existence of flipped E{sub 6} and E{sub 7} is shown, as well as several families and special cases of flipped embeddings. A possible physical reason, essentially based on the group theory of flipped embeddings, why nature prefers the low-energy group SU(3){times}SU(2){times}U(1) to alternatives such as SU(4){times}U(1) and SU(5) is pointed out.

  6. Some comments on flipped SU(5)xU(1) and flipped unification in general

    International Nuclear Information System (INIS)

    Barr, S.M.

    1989-01-01

    A general group-theoretical discussion of flipped embeddings is given. In addition to the well-known flipped SU(5) and flipped SO(10), the existence of flipped E 6 and E 7 is shown, as well as several families and special cases of flipped embeddings. A possible physical reason, essentially based on the group theory of flipped embeddings, why nature prefers the low-energy group SU(3)xSU(2)xU(1) to alternatives such as SU(4)xU(1) and SU(5) is pointed out

  7. Soldering formalism in noncommutative field theory: a brief note

    International Nuclear Information System (INIS)

    Ghosh, Subir

    2004-01-01

    In this Letter, I develop the soldering formalism in a new domain--the noncommutative planar field theories. The soldering mechanism fuses two distinct theories showing opposite or complimentary properties of some symmetry, taking into account the interference effects. The above mentioned symmetry is hidden in the composite (or soldered) theory. In the present work it is shown that a pair of noncommutative Maxwell-Chern-Simons theories, having opposite signs in their respective topological terms, can be consistently soldered to yield the Proca model (Maxwell theory with a mass term) with corrections that are at least quadratic in the noncommutativity parameter. We further argue that this model can be thought of as the noncommutative generalization of the Proca theory of ordinary spacetime. It is well known that abelian noncommutative gauge theory bears a close structural similarity with non-abelian gauge theory. This fact is manifested in a non-trivial way if the present Letter is compared with existing literature, where soldering of non-abelian models are discussed. Thus the present work further establishes the robustness of the soldering programme. The subtle role played by gauge invariance (or the lack of it), in the above soldering process, is revealed in an interesting way

  8. Utilization of Pb-free solders in MEMS packaging

    Science.gov (United States)

    Selvaduray, Guna S.

    2003-01-01

    Soldering of components within a package plays an important role in providing electrical interconnection, mechanical integrity and thermal dissipation. MEMS packages present challenges that are more complex than microelectronic packages because they are far more sensitive to shock and vibration and also require precision alignment. Soldering is used at two major levels within a MEMS package: at the die attach level and at the component attach level. Emerging environmental regulations worldwide, notably in Europe and Japan, have targeted the elimination of Pb usage in electronic assemblies, due to the inherent toxicity of Pb. This has provided the driving force for development and deployment of Pb-free solder alloys. A relatively large number of Pb-free solder alloys have been proposed by various researchers and companies. Some of these alloys have also been patented. After several years of research, the solder alloy system that has emerged is based on Sn as a major component. The electronics industry has identified different compositions for different specific uses, such as wave soldering, surface mount reflow, etc. The factors that affect choice of an appropriate Pb-free solder can be divided into two major categories, those related to manufacturing, and those related to long term reliability and performance.

  9. Fatigue and thermal fatigue of Pb-Sn solder joints

    International Nuclear Information System (INIS)

    Frear, D.; Grivas, D.; McCormack, M.; Tribula, D.; Morris, J.W. Jr.

    1987-01-01

    This paper presents a fundamental investigation of the fatigue and thermal fatigue characteristics, with an emphasis on the microstructural development during fatigue, of Sn-Pb solder joints. Fatigue tests were performed in simple shear on both 60Sn-40Pb and 5Sn-95Pb solder joints. Isothermal fatigue tests show increasing fatigue life of 60Sn-40Pb solder joints with decreasing strain and temperature. In contrast, such behavior was not observed in the isothermal fatigue of 5Sn-95Pb solder joints. Thermal fatigue results on 60Sn-40Pb solder cycled between -55 0 C and 125 0 C show that a coarsened region develops in the center of the joint. Both Pb-rich and Sn-rich phases coarsen, and cracks form within these coarsened regions. The failure mode 60Sn-40Pb solder joints in thermal and isothermal fatigue is similar: cracks form intergranularly through the Sn-rich phase or along Sn/Pb interphase boundaries. Extensive cracking is found throughout the 5Sn-95Pb joint for both thermal and isothermal fatigue. In thermal fatigue the 5Sn-95Pb solder joints failed after fewer cycles than 60Sn-40Pb

  10. Assessment of potential solder candidates for high temperature applications

    DEFF Research Database (Denmark)

    pressure to eliminate lead containing materials despite the fact that materials for high Pb containing alloys are currently not affected by any legislations. A tentative assessment was carried out to determine the potential solder candidates for high temperature applications based on the solidification...... criterion, phases predicted in the bulk solder and the thermodynamic stability of chlorides. These promising solder candidates were precisely produced using the hot stage microscope and its respective anodic and cathodic polarization curves were investigated using a micro-electrochemical set up...

  11. Manipulation and soldering of carbon nanotubes using atomic force microscope

    International Nuclear Information System (INIS)

    Kashiwase, Yuta; Ikeda, Takayuki; Oya, Takahide; Ogino, Toshio

    2008-01-01

    Manipulation of carbon nanotubes (CNTs) by an atomic force microscope (AFM) and soldering of CNTs using Fe oxide nanoparticles are described. We succeeded to separate a CNT bundle into two CNTs or CNT bundles, to move the separated CNT to a desirable position, and to bind it to another bundle. For the accurate manipulation, load of the AFM cantilever and frequency of the scan were carefully selected. We soldered two CNTs using an Fe oxide nanoparticle prepared from a ferritin molecule. The adhesion forces between the soldered CNTs were examined by an AFM and it was found that the CNTs were bound, though the binding force was not strong

  12. Effect of soldering techniques and gap distance on tensile strength of soldered Ni-Cr alloy joint.

    Science.gov (United States)

    Lee, Sang-Yeob; Lee, Jong-Hyuk

    2010-12-01

    The present study was intended to evaluate the effect of soldering techniques with infrared ray and gas torch under different gap distances (0.3 mm and 0.5 mm) on the tensile strength and surface porosity formation in Ni-Cr base metal alloy. Thirty five dumbbell shaped Ni-Cr alloy specimens were prepared and assigned to 5 groups according to the soldering method and the gap distance. For the soldering methods, gas torch (G group) and infrared ray (IR group) were compared and each group was subdivided by corresponding gap distance (0.3 mm: G3 and IR3, 0.5 mm: G5, IR5). Specimens of the experimental groups were sectioned in the middle with a diamond disk and embedded in solder blocks according to the predetermined distance. As a control group, 7 specimens were prepared without sectioning or soldering. After the soldering procedure, a tensile strength test was performed using universal testing machine at a crosshead speed 1 mm/min. The proportions of porosity on the fractured surface were calculated on the images acquired through the scanning electronic microscope. Every specimen of G3, G5, IR3 and IR5 was fractured on the solder joint area. However, there was no significant difference between the test groups (P > .05). There was a negative correlation between porosity formation and tensile strength in all the specimens in the test groups (P tensile strength of joints and porosity formations between the gas-oxygen torch soldering and infrared ray soldering technique or between the gap distance of 0.3 mm and 0.5 mm.

  13. Interfacial Reaction of Sn-Ag-Cu Lead-Free Solder Alloy on Cu: A Review

    Directory of Open Access Journals (Sweden)

    Liu Mei Lee

    2013-01-01

    Full Text Available This paper reviews the function and importance of Sn-Ag-Cu solder alloys in electronics industry and the interfacial reaction of Sn-Ag-Cu/Cu solder joint at various solder forms and solder reflow conditions. The Sn-Ag-Cu solder alloys are examined in bulk and in thin film. It then examines the effect of soldering conditions to the formation of intermetallic compounds such as Cu substrate selection, structural phases, morphology evolution, the growth kinetics, temperature and time is also discussed. Sn-Ag-Cu lead-free solder alloys are the most promising candidate for the replacement of Sn-Pb solders in modern microelectronic technology. Sn-Ag-Cu solders could possibly be considered and adapted in miniaturization technologies. Therefore, this paper should be of great interest to a large selection of electronics interconnect materials, reliability, processes, and assembly community.

  14. Flipped Classroom Experiences: Student Preferences and Flip Strategy in a Higher Education Context

    Science.gov (United States)

    McNally, Brenton; Chipperfield, Janine; Dorsett, Pat; Del Fabbro, Letitia; Frommolt, Valda; Goetz, Sandra; Lewohl, Joanne; Molineux, Matthew; Pearson, Andrew; Reddan, Gregory; Roiko, Anne; Rung, Andrea

    2017-01-01

    Despite the popularity of the flipped classroom, its effectiveness in achieving greater engagement and learning outcomes is currently lacking substantial empirical evidence. This study surveyed 563 undergraduate and postgraduate students (61% female) participating in flipped teaching environments and ten convenors of the flipped courses in which…

  15. Flip-J: Development of the System for Flipped Jigsaw Supported Language Learning

    Science.gov (United States)

    Yamada, Masanori; Goda, Yoshiko; Hata, Kojiro; Matsukawa, Hideya; Yasunami, Seisuke

    2016-01-01

    This study aims to develop and evaluate a language learning system supported by the "flipped jigsaw" technique, called "Flip-J". This system mainly consists of three functions: (1) the creation of a learning material database, (2) allocation of learning materials, and (3) formation of an expert and jigsaw group. Flip-J was…

  16. Flipping the Graduate Qualitative Research Methods Classroom: Did It Lead to Flipped Learning?

    Science.gov (United States)

    Earley, Mark

    2016-01-01

    The flipped, or inverted, classroom has gained popularity in a variety of fields and at a variety of educational levels, from K-12 through higher education. This paper describes the author's positive experience flipping a graduate qualitative research methods classroom. After a review of the current literature on flipped classrooms in higher…

  17. How to Flip the Classroom--"Productive Failure or Traditional Flipped Classroom" Pedagogical Design?

    Science.gov (United States)

    Song, Yanjie; Kapur, Manu

    2017-01-01

    The paper reports a quasi-experimental study comparing the "traditional flipped classroom" pedagogical design with the "productive failure" (Kapur, 2016) pedagogical design in the flipped classroom for a 2-week curricular unit on polynomials in a Hong Kong Secondary school. Different from the flipped classroom where students…

  18. Development of a soft-soldering system for aluminum

    Science.gov (United States)

    Falke, W. L.; Lee, A. Y.; Neumeier, L. A.

    1983-03-01

    The method employs application of a thin nickel copper alloy coating to the substrate, which enables the tin lead solders to wet readily and spread over the areas to be joined. The aluminum substrate is mechanically or chemically cleaned to facilitate bonding to a minute layer of zinc that is subsequently applied, with an electroless zincate solution. The nickel copper alloy (30 to 70 pct Ni) coating is then applied electrolytically over the zinc, using immersion cell or brush coating techniques. Development of acetate electrolytes has permitted deposition of the proper alloys coatings. The coated areas can then be readily joined with conventional tin lead solders and fluxs. The joints so formed are ductile, strong, and relatively corrosion resistant, and exhibit strengths equivalent to those formed on copper and brass when the same solders and fluxes are used. The method has also been employed to soft solder magnesium alloys.

  19. Strength of joints brazed with two-phase solders

    International Nuclear Information System (INIS)

    Shnyakin, N.S.; Parfenova, L.V.; Ekatova, A.S.; Prilepskaya, I.V.

    1976-01-01

    Dependence of the structure and strength of soldered joints upon a gap size in case of 1Kh18N10T stainless steel soldering with a double-phase solder of Ni-Zn-Cu system is described. Butt and lap joints have been subjected to soldering with gas-flame and induction heating. The optimum conditions of the solder crystallization are determined with wedge-gap samples. The studies show that the character of distribution of a fusible β-phase in metal depends upon a gap size. With gaps up to 0.1 mm the β-phase enriched with a fusible component (zinc) runs as a continuous thin interlayer in the middle of the seam. As a result of zinc evaporation from the β-phase this interlayer becomes internally oxidized. After the sample is broken an oxidized fracture gives one the impression of a poor fusion in the middle part of the joint. The ultimate strength of butt joints is 15-20 kgf/sq.mm. A value of thermal expansion of 1Kh18N10T steel samples, 1-5 mm thick, has been experimentally determined for butt soldering. The elongation of two halves of the sample is measured by an indicator and proved to be 0.89 mm for a 50x50x2 mm sample at a soldering temperature of 1.100 deg C. The paper presents methods for the calculation of an optimal gap value for butt soldering with a local gas-flame and induction heating

  20. Chips 2020

    CERN Document Server

    2016-01-01

    The release of this second volume of CHIPS 2020 coincides with the 50th anniversary of Moore’s Law, a critical year marked by the end of the nanometer roadmap and by a significantly reduced annual rise in chip performance. At the same time, we are witnessing a data explosion in the Internet, which is consuming 40% more electrical power every year, leading to fears of a major blackout of the Internet by 2020. The messages of the first CHIPS 2020, published in 2012, concerned the realization of quantum steps for improving the energy efficiency of all chip functions. With this second volume, we review these messages and amplify upon the most promising directions: ultra-low-voltage electronics, nanoscale monolithic 3D integration, relevant-data, brain- and human-vision-inspired processing, and energy harvesting for chip autonomy. The team of authors, enlarged by more world leaders in low-power, monolithic 3D, video, and Silicon brains, presents new vistas in nanoelectronics, promising  Moore-like exponential g...

  1. Characteristics of solder joints under fatigue loads using piezomechanical actuation

    Science.gov (United States)

    Shim, Dong-Jin; Spearing, S. Mark

    2003-07-01

    Crack initiation and growth characteristics of solder joints under fatigue loads are investigated using piezomechanical actuation. Cracks in solder joints, which can cause failure in microelectronics components, are induced via piezoelectricity in piezo-ceramic bonded joints. Lead-zirconate-titanate ceramic plates and eutectic Sn-Pb solder bonded in a double-lap shear configuration are used in the investigation. Electric field across each piezo-ceramic plate is applied such that shear stresses/strains are induced in the solder joints. The experiments show that cracks initiate in the solder joints around defects such as voids and grow in length until they coalesce with other cracks from adjacent voids. These observations are compared with the similar thermal cycling tests from the literature to show feasibility and validity of the current method in investigating the fatigue characteristics of solder joints. In some specimens, cracks in the piezo-ceramic plates are observed, and failure in the specimens generally occurred due to piezo-ceramic plate fracture. The issues encountered in implementing this methodology such as low actuation and high processing temperatures are further discussed.

  2. Laser Soldering of Rat Skin Using a Controlled Feedback System

    Directory of Open Access Journals (Sweden)

    Mohammad Sadegh Nourbakhsh

    2009-03-01

    Full Text Available Introduction: Laser tissue soldering using albumin and indocyanine green dye (ICG is an effective technique utilized in various surgical procedures. The purpose of this study was to perform laser soldering of rat skin under a feedback control system and compare the results with those obtained using standard sutures. Material and Methods: Skin incisions were made over eight rats’ dorsa, which were subsequently closed using different wound closure interventions in two groups: (a using a temperature controlled infrared detector or (b by suture. Tensile strengths were measured at 2, 5, 7 and 10 days post-incision. Histological examination was performed at the time of sacrifice. Results: Tensile strength results showed that during the initial days following the incisions, the tensile strengths of the sutured samples were greater than the laser samples. However, 10 days after the incisions, the tensile strengths of the laser soldered incisions were higher than the sutured cuts. Histopathological examination showed a preferred wound healing response in the soldered skin compared with the control samples. The healing indices of the laser soldered repairs (426 were significantly better than the control samples (340.5. Conclusion: Tissue feedback control of temperature and optical changes in laser soldering of skin leads to a higher tensile strength and better histological results and hence this method may be considered as an alternative to standard suturing.

  3. Tensile strength of two soldered alloys (Minalux and Verabond2

    Directory of Open Access Journals (Sweden)

    Mir Mohammad Rezaee S

    2002-07-01

    Full Text Available Recently. Minalux alloy, a base metal free from Be, has been presented on the market while no special soldering has been recommended for it. On the other hand, based on the manufacturer's claim, this alloy is similar to Verabond2. The aim of this study was to investigate the tensile strength of Minalux and Verabond2, soldered by Verasolder. Twelve standard dambble shape samples, with the length of 18 mm and the diameter of 3mm, were prepared from each alloy. Six samples of each alloy were divided into two pieces with carboradom disk. Soldering gap distance was 0.3mm, measured by a special jig and they were soldered by Verasolder alloy. Six other samples, of both Iranian and foreign unsoldered alloys were considered as control group. Then samples were examined under tensile force and their tensile strength was recorded. Two- way variance analysis showed that the tensile strength of Minalux alloy and Verabond2 were not statistically significant (Verasoler 686, Minalux 723, but after soldering, such difference became significant (Minalux 308, Verabond2 432. Verabond2 showed higher tensile strength after soldering.

  4. Features of Pd-Ni-Fe solder system for vacuum brazing of low alloy steels

    International Nuclear Information System (INIS)

    Radzievskij, V.N.; Kurochko, R.S.; Lotsmanov, S.N.; Rymar', V.I.

    1975-01-01

    The brazing solder of the Pd-Ni-Fe alloyed with copper and lithium, in order to decrease the melting point and provide for a better spreading, when soldered in vacuum ensures a uniform strength of soldered joints with the base metal of low-alloyed steels of 34KHNIM-type. The properties of low-alloyed steel joints brazed with the Pd-Ni-Fe-system solder little depend on the changes in the soldering parameters. The soldered joint keeps a homogeneous structure after all the stages of heat treatment (annealing, quenching and tempering)

  5. Lead-free solder technology transfer from ASE Americas

    Energy Technology Data Exchange (ETDEWEB)

    FTHENAKIS,V.

    1999-10-19

    To safeguard the environmental friendliness of photovoltaics, the PV industry follows a proactive, long-term environmental strategy involving a life-of-cycle approach to prevent environmental damage by its processes and products from cradle to grave. Part of this strategy is to examine substituting lead-based solder on PV modules with other solder alloys. Lead is a toxic metal that, if ingested, can damage the brain, nervous system, liver and kidneys. Lead from solder in electronic products has been found to leach out from municipal waste landfills and municipal incinerator ash was found to be high in lead also because of disposed consumer electronics and batteries. Consequently, there is a movement in Europe and Japan to ban lead altogether from use in electronic products and to restrict the movement across geographical boundaries of waste containing lead. Photovoltaic modules may contain small amounts of regulated materials, which vary from one technology to another. Environmental regulations impact the cost and complexity of dealing with end-of-life PV modules. If they were classified as hazardous according to Federal or State criteria, then special requirements for material handling, disposal, record-keeping and reporting would escalate the cost of decommissioning the modules. Fthenakis showed that several of today's x-Si modules failed the US-EPA Toxicity Characteristic Leaching Procedure (TCLP) for potential leaching of Pb in landfills and also California's standard on Total Threshold Limit Concentration (TTLC) for Pb. Consequently, such modules may be classified as hazardous waste. He highlighted potential legislation in Europe and Japan which could ban or restrict the use of lead and the efforts of the printed-circuit industries in developing Pb-free solder technologies in response to such expected legislation. Japanese firms already have introduced electronic products with Pb-free solder, and one PV manufacturer in the US, ASE Americas has used a

  6. To Flip or Not to Flip? Analysis of a Flipped Classroom Pedagogy in a General Biology Course

    Science.gov (United States)

    Heyborne, William H.; Perrett, Jamis J.

    2016-01-01

    In an attempt to better understand the flipped technique and evaluate its purported superiority in terms of student learning gains, the authors conducted an experiment comparing a flipped classroom to a traditional lecture classroom. Although the outcomes were mixed, regarding the superiority of either pedagogical approach, there does seem to be a…

  7. Characterizing the Soldering Alloy Type In–Ag–Ti and the Study of Direct Soldering of SiC Ceramics and Copper

    Directory of Open Access Journals (Sweden)

    Roman Koleňák

    2018-04-01

    Full Text Available The aim of the research was to characterize the soldering alloy In–Ag–Ti type, and to study the direct soldering of SiC ceramics and copper. The In10Ag4Ti solder has a broad melting interval, which mainly depends on its silver content. The liquid point of the solder is 256.5 °C. The solder microstructure is composed of a matrix with solid solution (In, in which the phases of titanium (Ti3In4 and silver (AgIn2 are mainly segregated. The tensile strength of the solder is approximately 13 MPa. The strength of the solder increased with the addition of Ag and Ti. The solder bonds with SiC ceramics, owing to the interaction between active In metal and silicon infiltrated in the ceramics. XRD analysis has proven the interaction of titanium with ceramic material during the formation of the new minority phases of titanium silicide—SiTi and titanium carbide—C5Ti8. In and Ag also affect bond formation with the copper substrate. Two new phases were also observed in the bond interphase—(CuAg6In5 and (AgCuIn2. The average shear strength of a combined joint of SiC–Cu, fabricated with In10Ag4Ti solder, was 14.5 MPa. The In–Ag–Ti solder type studied possesses excellent solderability with several metallic and ceramic materials.

  8. Interaction-flip identities in spin glasses

    NARCIS (Netherlands)

    Contucci, P.; Giardinà, C.; Giberti, C.

    2009-01-01

    We study the properties of fluctuation for the free energies and internal energies of two spin glass systems that differ for having some set of interactions flipped. We show that their difference has a variance that grows like the volume of the flipped region. Using a new interpolation method, which

  9. Just in Time to Flip Your Classroom

    Science.gov (United States)

    Lasry, Nathaniel; Dugdale, Michael; Charles, Elizabeth

    2014-01-01

    With advocates like Sal Khan and Bill Gates, flipped classrooms are attracting an increasing amount of media and research attention. We had heard Khan's TED talk and were aware of the concept of inverted pedagogies in general. Yet it really hit home when we accidentally flipped our classroom. Our objective was to better prepare our students…

  10. Conceptualizing "Homework" in Flipped Mathematics Classes

    Science.gov (United States)

    de Araujo, Zandra; Otten, Samuel; Birisci, Salih

    2017-01-01

    Flipped instruction is becoming more common in the United States, particularly in mathematics classes. One of the defining characteristics of this increasingly popular instructional format is the homework teachers assign. In contrast to traditional mathematics classes in which homework consists of problem sets, homework in flipped classes often…

  11. Diverse Perspectives on a Flipped Biostatistics Classroom

    Science.gov (United States)

    Schwartz, Todd A.; Andridge, Rebecca R.; Sainani, Kirstin L.; Stangle, Dalene K.; Neely, Megan L.

    2016-01-01

    "Flipping" the classroom refers to a pedagogical approach in which students are first exposed to didactic content outside the classroom and then actively use class time to apply their newly attained knowledge. The idea of the flipped classroom is not new, but has grown in popularity in recent years as the necessary technology has…

  12. Best Practices for Launching a Flipped Classroom

    Science.gov (United States)

    Hall, Ashley A.; DuFrene, Debbie D.

    2016-01-01

    Popularity is growing for flipped classroom instruction, which replaces lectures with out-of-class delivery of streaming video, reading materials, online chats, and other modalities. Face-to-face class time is spent on instructor-student and student-student interaction, including small group problem solving and discussion. Classroom flipping has…

  13. STEM Teacher Efficacy in Flipped Classrooms

    Science.gov (United States)

    Kelly, Daniel; Denson, Cameron

    2017-01-01

    The flipped classroom instructional model continues to grow in adoption and use in K-12 classrooms. Although there are an increasing number of studies into the implementation of the flipped classroom, there is limited empirical research into its effectiveness and even fewer into the educational, psychological, and theoretical constructs underlying…

  14. The Flipped Classroom: A Twist on Teaching

    Science.gov (United States)

    Schmidt, Stacy M. P.; Ralph, David L.

    2016-01-01

    The traditional classroom has utilized the "I Do", "We Do", "You Do" as a strategy for teaching for years. The flipped classroom truly flips that strategy. The teacher uses "You Do", "We Do", "I Do" instead. Homework, inquiry, and investigation happen in the classroom. At home students…

  15. Examining the Flipped Classroom through Action Research

    Science.gov (United States)

    Lo, Chung Kwan

    2017-01-01

    There is a growing interest in using a flipped classroom format in day-to-day teaching. Direct computer-based individual instruction outside the classroom and interactive group learning activities inside the classroom are the two essential components of the flipped classroom model. By watching instructional videos, students can work through some…

  16. Flipped Classroom Instruction for Inclusive Learning

    Science.gov (United States)

    Altemueller, Lisa; Lindquist, Cynthia

    2017-01-01

    The flipped classroom is a teaching methodology that has gained recognition in primary, secondary and higher education settings. The flipped classroom inverts traditional teaching methods, delivering lecture instruction outside class, and devoting class time to problem solving, with the teacher's role becoming that of a learning coach and…

  17. Just in Time to Flip Your Classroom

    Science.gov (United States)

    Lasry, Nathaniel; Dugdale, Michael; Charles, Elizabeth

    2014-01-01

    With advocates like Sal Khan and Bill Gates, flipped classrooms are attracting an increasing amount of media and research attention.2 We had heard Khan's TED talk and were aware of the concept of inverted pedagogies in general. Yet it really hit home when we accidentally flipped our classroom. Our objective was to better prepare our students for class. We set out to effectively move some of our course content outside of class and decided to tweak the Just-in-Time Teaching approach (JiTT).3 To our surprise, this tweak—which we like to call the flip-JiTT—ended up completely flipping our classroom. What follows is narrative of our experience and a procedure that any teacher can use to extend JiTT to a flipped classroom.

  18. Relationships in the Flipped Classroom

    Directory of Open Access Journals (Sweden)

    Brett M. McCollum

    2017-12-01

    Full Text Available This study examines the effectiveness of flipped classrooms in chemistry, and identifies relationships as a major factor impacting the success of flipped instruction methods. Examination of student interview data reveals factors that affect the development of peer-peer, peer-peer leader, and peer-expert relationships in first-year general chemistry and second-year organic chemistry flipped classrooms. Success was measured in terms of student perceptions of the effectiveness of the instruction, as well as student academic development. Furthermore, analysis of research participant interviews reveals that academic reading circles, open-response multiple-attempt group quizzes, and peer leaders are important elements of a text-centric flipped approach at a small-classroom, commuter-campus university. Student reflections and classroom observations provide further support for these conclusions. Cet étude examine l’efficacité des salles de classe inversées en chimie et identifie la création de liens en tant que facteur important qui affecte la réussite des méthodes d’instruction inversée. L’examen des données provenant d’entrevues avec les étudiants révèle les facteurs qui affectent le développement des rapports d’étudiant à étudiant, d’étudiant à leader et d’étudiant à expert dans un cours inversé de chimie générale de première année et dans un cours de chimie organique de deuxième année. La réussite a été mesurée en termes de perceptions des étudiants de l’efficacité de l’instruction, ainsi que du développement académique des étudiants. De plus, l’analyse des entrevues des participants à la recherche révèle que les cercles de lecture universitaires, les tests de groupes à essais multiples et à réponses ouvertes, ainsi que les leaders de groupes sont des éléments importants d’une approche inversée centrée sur un texte en petite salle de classe, dans une université de banlieusards. Les

  19. Thermal decomposition of solder flux activators under simulated wave soldering conditions

    DEFF Research Database (Denmark)

    Piotrowska, Kamila; Jellesen, Morten Stendahl; Ambat, Rajan

    2017-01-01

    /methodology/approach: Changes in the chemical structure of the activators were studied using Fourier transform infrared spectroscopy technique and were correlated to the exposure temperatures within the range of wave soldering process. The amount of residue left on the surface was estimated using standardized acid-base...... titration method as a function of temperature, time of exposure and the substrate material used. Findings: The study shows that there is a possibility of anhydride-like species formation during the thermal treatment of fluxes containing weak organic acids (WOAs) as activators (succinic and DL...

  20. Flipping Radiology Education Right Side Up.

    Science.gov (United States)

    O'Connor, Erin E; Fried, Jessica; McNulty, Nancy; Shah, Pallav; Hogg, Jeffery P; Lewis, Petra; Zeffiro, Thomas; Agarwal, Vikas; Reddy, Sravanthi

    2016-07-01

    In flipped learning, medical students independently learn facts and concepts outside the classroom, and then participate in interactive classes to learn to apply these facts. Although there are recent calls for medical education reform using flipped learning, little has been published on its effectiveness. Our study compares the effects of flipped learning to traditional didactic instruction on students' academic achievement, task value, and achievement emotions. At three institutions, we alternated flipped learning with traditional didactic lectures during radiology clerkships, with 175 medical students completing a pretest on general diagnostic imaging knowledge to assess baseline cohort comparability. Following instruction, posttests and survey examinations of task value and achievement emotions were administered. Linear mixed effects analysis was used to examine the relationship between test scores and instruction type. Survey responses were modeled using ordinal category logistic regression. Instructor surveys were also collected. There were no baseline differences in test scores. Mean posttest minus pretest scores were 10.5% higher in the flipped learning group than in the didactic instruction group (P = 0.013). Assessment of task value and achievement emotions showed greater task value, increased enjoyment, and decreased boredom with flipped learning (all P flipped learning condition. Flipped learning was associated with increased academic achievement, greater task value, and more positive achievement emotions when compared to traditional didactic instruction. Further investigation of flipped learning methods in radiology education is needed to determine whether flipped learning improves long-term retention of knowledge, academic success, and patient care. Copyright © 2016 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

  1. Mechanical properties of Bi-In-Zn/ Cu solder joint system

    International Nuclear Information System (INIS)

    Ervina Efzan Mohd Noor; Mohammed Noori Ridha; Ahmad Badri Ismail; Nurulakmal Mohd Sharif; Kuan Yew Cheong; Tadashi Ariga; Zuhailawati Hussain

    2009-01-01

    Full text: In recent years, the pollution of environment from lead (Pb) and Pb-containing compounds in microelectronic devices attracts more and more attentions in academia and industry; the lead-free solder alloys begin to replace the lead-based solders in packaging process of some devices and components. In this works, microstructure and mechanical properties of different reflow temperature (80, 100, 120 and 140 degree Celsius) for solder joints on shear strength of Bi-In-Zn lead free solder with low melting temperature of 60 degree Celsius on Cu solder joint has been investigated. This paper will compared the mechanical properties of the Bi-In-Zn lead-free solder alloys with current lead-free solder, Sn-Ag-Cu solder alloy. The fracture surface analyses have been observed by Optical Microscope and were investigated by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) and proved it by X-ray diffraction (XRD). (author)

  2. Correlation Between Pin Misalignment and Crack Length in THT Solder Joints

    Directory of Open Access Journals (Sweden)

    Molnar A.

    2017-06-01

    Full Text Available In this manuscript, correlations were searched for between pin misalignments relative to PCB bores and crack propagation after cyclic thermal shock tests in THT solder joints produced from lead-free solder alloys. In total, 7 compositions were examined including SAC solders with varying Ag, Cu and Ni contents. The crack propagation was initiated by cyclic thermal shock tests with 40°C / +125°C temperature profiles. Pin misalignments relative to the bores were characterized with three attributes obtained from one section of the examined solder joints. Cracks typically originated at the solder/pin or solder/bore interfaces and propagated within the solder. It was shown that pin misalignments did not have an effect on crack propagation, thus, the solder joints’ lifetime.

  3. Flipping the Electromagnetic Theory classroom

    Science.gov (United States)

    Berger, Andrew J.

    2017-08-01

    Electromagnetic Theory is a required junior-year course for Optics majors at the University of Rochester. This foundational course gives students their first rigorous exposure to electromagnetic vector fields, dipole radiation patterns, Fresnel reflection/transmission coefficients, waveguided modes, Jones vectors, waveplates, birefringence, and the Lorentz model of refractive index. To increase the percentage of class time devoted to student-centered conceptual reasoning and instructor feedback, this course was recently "flipped". Nearly all of the mathematically-intensive derivations were converted to narrated screencasts ("Khan Academy" style) and made available to students through the course's learning management system. On average, the students were assigned two 10-15 minute videos to watch in advance of each lecture. An electronic survey after each tutorial encouraged reflection and counted towards the student's participation grade. Over the past three years, students have consistently rated the videos as being highly valuable. This presentation will discuss the technical aspects of creating tutorial videos and the educational tradeoffs of flipping a mathematically-intensive upper-level course. The most important advantage is the instructor's increased ability to identify and respond to student confusion, via activities that would consume too much time in a lecture-centered course. Several examples of such activities will be given. Two pitfalls to avoid are the temptation for the instructor not to update the videos from year to year and the tendency of students not to take lecture notes while watching the videos.

  4. Commentary: Photothermal effects of laser tissue soldering

    International Nuclear Information System (INIS)

    Menovsky, T.; Beek, J.F.; Gemert, M.J.C. van

    1999-01-01

    Full text: Laser tissue welding is the process of using laser energy to join tissues without sutures or with a reduced number of sutures. Recently, diode lasers have been added to the list of fusion lasers (Lewis and Uribe 1993, Reali et al 1993). Typically, for tissue welding, deep penetrating diode lasers emitting at 800-810 nm are used, in combination with a strong absorbing protein solder containing the dye indocyanine green. Indocyanine green has a maximum absorption coefficient at 805 nm and binds preferentially with proteins (Sauda et al 1986). The greatest advantage of diode lasers is their compact size, easy use and low cost. In this issue of Physics in Medicine and Biology (pp 983-1002, 'Photothermal effects of laser tissue soldering'), in an in vitro study, McNally et al investigate the optimal laser settings and welding temperatures in relation to the tensile strength and thermal damage of bovine aorta specimens. An interesting statement in their introduction is that the low strength of laser produced anastomoses can lead to aneurysm formation. The increased chance of aneurysm formation may merely be due to the thermal effect of the laser on the vascular wall, especially on the adventitia and media layers, which become necrotic after thermal injury. Subsequent haemodynamic stress exerted on a damaged vascular wall is a significant contributing factor for aneurysmal initiation. Also interesting is the remark that 'by the application of wavelength-specific chromophores in tissue welding ... the requirement for precise focusing and aiming of the laser beam may be removed'. Though perhaps not yet fully justified, this statement, if true, would facilitate surgical procedures. While the experiments are conducted in a proper manner, the use of bovine aorta specimens, which were stored at -70 deg. C and subsequently thawed for the tissue welding experiments, may not be the most appropriate for studying tissue effects or tensile strength measurements, as the

  5. 30 CFR 77.1112 - Welding, cutting, or soldering with arc or flame; safeguards.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Welding, cutting, or soldering with arc or... WORK AREAS OF UNDERGROUND COAL MINES Fire Protection § 77.1112 Welding, cutting, or soldering with arc or flame; safeguards. (a) When welding, cutting, or soldering with arc or flame near combustible...

  6. 30 CFR 75.1106 - Welding, cutting, or soldering with arc or flame underground.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Welding, cutting, or soldering with arc or... Protection § 75.1106 Welding, cutting, or soldering with arc or flame underground. [Statutory Provisions] All welding, cutting, or soldering with arc or flame in all underground areas of a coal mine shall, whenever...

  7. 30 CFR 77.1916 - Welding, cutting, and soldering; fire protection.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Welding, cutting, and soldering; fire... OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1916 Welding, cutting, and soldering; fire protection. (a) One portable fire extinguisher shall be provided where welding, cutting, or soldering with...

  8. Comparing the Effectiveness of Blended, Semi-Flipped, and Flipped Formats in an Engineering Numerical Methods Course

    Science.gov (United States)

    Clark, Renee M.; Kaw, Autar; Besterfield-Sacre, Mary

    2016-01-01

    Blended, flipped, and semi-flipped instructional approaches were used in various sections of a numerical methods course for undergraduate mechanical engineers. During the spring of 2014, a blended approach was used; in the summer of 2014, a combination of blended and flipped instruction was used to deliver a semi-flipped course; and in the fall of…

  9. The Partially Flipped Classroom: The Effects of Flipping a Module on "Junk Science" in a Large Methods Course

    Science.gov (United States)

    Burgoyne, Stephanie; Eaton, Judy

    2018-01-01

    Flipped classrooms are gaining popularity, especially in psychology statistics courses. However, not all courses lend themselves to a fully flipped design, and some instructors might not want to commit to flipping every class. We tested the effectiveness of flipping just one component (a module on junk science) of a large methods course. We…

  10. Flipped classroom: a review of recent literature

    Directory of Open Access Journals (Sweden)

    Huseyin Uzunboylu

    2015-07-01

    Full Text Available The use of learning technologies, especially multimedia provide varied facilities for students’ learning that are not possible with other media. Pedagogical literature has proved that individuals have different learning styles. Flipped classroom is a pedagogical approach which means that activities that have traditionally taken place inside the classroom take place outside the classroom and vice versa. Flipped classroom environment ensures that students become more active participants compared with the traditional classroom. The purpose of this paper is to fulfil the needs regarding the review of recent literature on the use of flipped classroom approach in education. The contribution of flipped classroom to education is discussed in relation to the change of students' and instructors' role. Subsequently, flipped classroom applications in various disciplines of education are illustrated. The recommendations made in the literature for design specifications that integrate flipped classrooms with technology are discussed. The paper concludes that a careful consideration of the warnings and recommendations made in the literature can help to produce effective flipped classroom environments and also this paper attempts to inform those who are thinking of using new technologies and approaches to deliver courses.

  11. Influence of Co and W powders on viscosity of composite solders during soldering of specially shaped diamond-abrasive tools

    Science.gov (United States)

    Sokolov, E. G.; Aref’eva, S. A.; Svistun, L. I.

    2018-03-01

    The influence of Co and W powders on the structure and the viscosity of composite solders Sn-Cu-Co-W used for the manufacture of the specially shaped diamond tools has been studied. The solders were obtained by mixing the metallic powders with an organic binder. The mixtures with and without diamonds were applied to steel rollers and shaped substrates. The sintering was carried out in a vacuum at 820 ° C with time-exposure of 40 minutes. The influence of Co and W powders on the viscosity solders was evaluated on the basis of the study of structures and according to the results of sintering specially shaped diamond tools. It was found that to provide the necessary viscosity and to obtain the uniform diamond-containing layers on the complex shaped surfaces, Sn-Cu-Co-W solder should contain 27–35 vol % of solid phase. This is achieved with a total solder content of 24–32 wt % of cobalt powder and 7 wt % of tungsten powder.

  12. An Overview of Surface Finishes and Their Role in Printed Circuit Board Solderability and Solder Joint Performance

    Energy Technology Data Exchange (ETDEWEB)

    Vianco, P.T.

    1998-10-15

    A overview has been presented on the topic of alternative surface finishes for package I/Os and circuit board features. Aspects of processability and solder joint reliability were described for the following coatings: baseline hot-dipped, plated, and plated-and-fused 100Sn and Sn-Pb coatings; Ni/Au; Pd, Ni/Pd, and Ni/Pd/Au finishes; and the recently marketed immersion Ag coatings. The Ni/Au coatings appear to provide the all-around best option in terms of solderability protection and wire bondability. Nickel/Pal ftishes offer a slightly reduced level of performance in these areas that is most likely due to variable Pd surface conditions. It is necessmy to minimize dissolved Au or Pd contents in the solder material to prevent solder joint embrittlement. Ancillary aspects that included thickness measurement techniques; the importance of finish compatibility with conformal coatings and conductive adhesives; and the need for alternative finishes for the processing of non-Pb bearing solders were discussed.

  13. Automation of experimental research of waveguide paths induction soldering

    Science.gov (United States)

    Tynchenko, V. S.; Petrenko, V. E.; Kukartsev, V. V.; Tynchenko, V. V.; Antamoshkin, O. A.

    2018-05-01

    The article presents an automated system of experimental studies of the waveguide paths induction soldering process. The system is a part of additional software for a complex of automated control of the technological process of induction soldering of thin-walled waveguide paths from aluminum alloys, expanding its capabilities. The structure of the software product, the general appearance of the controls and the potential application possibilities are presented. The utility of the developed application by approbation in a series of field experiments was considered and justified. The application of the experimental research system makes it possible to improve the process under consideration, providing the possibility of fine-tuning the control regulators, as well as keeping the statistics of the soldering process in a convenient form for analysis.

  14. Optimization of the soldering process by the DMAIC methodology

    Directory of Open Access Journals (Sweden)

    Michał Zasadzień

    2016-06-01

    Full Text Available The chapter presents the use of the DMAIC method for the analysis and improvement of the process of soldering pins in a plug connecting a bundle of wires to the board of a controller; a part of the steering system of a car. The main problem in the soldering process, that is an unsatisfactory share of bad soldered connections between the board and the plug and the instability of that number, was identified by means of a five-phase improvement process. Key points and main causes of the defect were pointed out, and process improvement measures were suggested. Due to the analysis conducted and the correct implementation of improvement measures the share of defective connections has been decreased twofold.

  15. Using lightboard to flip the course

    DEFF Research Database (Denmark)

    Timcenko, Olga; Triantafyllou, Evangelia; Nilsson, Niels Chr.

    , and exercises for in-class work. However, the quality of videos that students have to watch before coming to the class is also important. In this paper, we will describe videos prepared for flipped classroom using light board, an invention from 2014. That allows natural flow of presentation, as it combines......Authors of the paper have several years of experience with flipping parts of the courses, and the whole courses. Crucial for successful flipping the class are well-chosen exercises that students need to do before the class, as a confirmation that they come prepared for in-class exercises...

  16. Twelve tips for "flipping" the classroom.

    Science.gov (United States)

    Moffett, Jennifer

    2015-04-01

    The flipped classroom is a pedagogical model in which the typical lecture and homework elements of a course are reversed. The following tips outline the steps involved in making a successful transition to a flipped classroom approach. The tips are based on the available literature alongside the author's experience of using the approach in a medical education setting. Flipping a classroom has a number of potential benefits, for example increased educator-student interaction, but must be planned and implemented carefully to support effective learning.

  17. Enhancing student engagement using the flipped classroom.

    Science.gov (United States)

    Gilboy, Mary Beth; Heinerichs, Scott; Pazzaglia, Gina

    2015-01-01

    The flipped classroom is an innovative pedagogical approach that focuses on learner-centered instruction. The purposes of this report were to illustrate how to implement the flipped classroom and to describe students' perceptions of this approach within 2 undergraduate nutrition courses. The template provided enables faculty to design before, during, and after class activities and assessments based on objectives using all levels of Bloom's taxonomy. The majority of the 142 students completing the evaluation preferred the flipped method compared with traditional pedagogical strategies. The process described in the report was successful for both faculty and students. Copyright © 2015 Society for Nutrition Education and Behavior. Published by Elsevier Inc. All rights reserved.

  18. Teaching & Learning Tips 6: The flipped classroom.

    Science.gov (United States)

    Shi, Connie R; Rana, Jasmine; Burgin, Susan

    2018-04-01

    Challenge: The "flipped classroom" is a pedagogical model in which instructional materials are delivered to learners outside of class, reserving class time for application of new principles with peers and instructors. Active learning has forever been an elusive ideal in medical education, but the flipped class model is relatively new to medical education. What is the evidence for the "flipped classroom," and how can these techniques be applied to the teaching of dermatology to trainees at all stages of their medical careers? © 2018 The International Society of Dermatology.

  19. Drinking Water Contamination Due To Lead-based Solder

    Science.gov (United States)

    Garcia, N.; Bartelt, E.; Cuff, K. E.

    2004-12-01

    The presence of lead in drinking water creates many health hazards. Exposure to lead-contaminated water can affect the brain, the central nervous system, blood cells, and kidneys, causing such problems as mental retardation, kidney disease, heart disease, stroke, and death. One way in which lead can contaminate our water supply is through the use of lead solder to join pipes. Lead solder was widely used in the past because of its ease of application as well as its low cost. Lead contamination in residential areas has previously been found to be a particularly serious problem in first-draw samples, of water that has sat stagnant in pipes overnight. To investigate the time-dependence of drinking water lead contamination, we analyzed samples taken hourly of water exposed to lead solder. While our preliminary data was insufficient to show more than a rough correlation between time of exposure and lead concentration over short periods (1-3 hours), we were able to confirm that overnight exposure of water to lead-based solder results in the presence high levels of lead. We also investigated other, external factors that previous research has indicated contribute to increased concentrations of lead. Our analysis of samples of lead-exposed water at various pH and temperatures suggests that these factors can be equally significant in terms of their contribution to elevated lead concentration levels. In particular, water that is slightly corrosive appears to severely impact the solubility of lead. As this type of water is common in much of the Northeast United States, the presence of lead-based solder in residential areas there is especially problematic. Although lead-based solder has been banned since the 1980s, it remains a serious concern, and a practical solution still requires further research.

  20. Bottom-up nanoarchitecture of semiconductor nano-building blocks by controllable in situ SEM-FIB thermal soldering method

    KAUST Repository

    Zhang, Xuan

    2017-08-10

    Here we demonstrate that the building blocks of semiconductor WO3 nanowires can be controllably soldered together by a novel nano-soldering technique of in situ SEM-FIB thermal soldering, in which the soldering temperature can precisely remain in an optimal range to avoid a strong thermal diffusion.

  1. Bottom-up nanoarchitecture of semiconductor nano-building blocks by controllable in situ SEM-FIB thermal soldering method

    KAUST Repository

    Zhang, Xuan; Zheng, Xiujun; Zhang, Hong; Zhang, Junli; Fu, Jiecai; Zhang, Qiang; Peng, Chaoyi; Bai, Feiming; Zhang, Xixiang; Peng, Yong

    2017-01-01

    Here we demonstrate that the building blocks of semiconductor WO3 nanowires can be controllably soldered together by a novel nano-soldering technique of in situ SEM-FIB thermal soldering, in which the soldering temperature can precisely remain in an optimal range to avoid a strong thermal diffusion.

  2. Uncertainty in T1 mapping using the variable flip angle method with two flip angles

    International Nuclear Information System (INIS)

    Schabel, Matthias C; Morrell, Glen R

    2009-01-01

    Propagation of errors, in conjunction with the theoretical signal equation for spoiled gradient echo pulse sequences, is used to derive a theoretical expression for uncertainty in quantitative variable flip angle T 1 mapping using two flip angles. This expression is then minimized to derive a rigorous expression for optimal flip angles that elucidates a commonly used empirical result. The theoretical expressions for uncertainty and optimal flip angles are combined to derive a lower bound on the achievable uncertainty for a given set of pulse sequence parameters and signal-to-noise ratio (SNR). These results provide a means of quantitatively determining the effect of changing acquisition parameters on T 1 uncertainty. (note)

  3. FLIP the Switch: Regulation of Apoptosis and Necroptosis by cFLIP

    Directory of Open Access Journals (Sweden)

    Yuichi Tsuchiya

    2015-12-01

    Full Text Available cFLIP (cellular FLICE-like inhibitory protein is structurally related to caspase-8 but lacks proteolytic activity due to multiple amino acid substitutions of catalytically important residues. cFLIP protein is evolutionarily conserved and expressed as three functionally different isoforms in humans (cFLIPL, cFLIPS, and cFLIPR. cFLIP controls not only the classical death receptor-mediated extrinsic apoptosis pathway, but also the non-conventional pattern recognition receptor-dependent apoptotic pathway. In addition, cFLIP regulates the formation of the death receptor-independent apoptotic platform named the ripoptosome. Moreover, recent studies have revealed that cFLIP is also involved in a non-apoptotic cell death pathway known as programmed necrosis or necroptosis. These functions of cFLIP are strictly controlled in an isoform-, concentration- and tissue-specific manner, and the ubiquitin-proteasome system plays an important role in regulating the stability of cFLIP. In this review, we summarize the current scientific findings from biochemical analyses, cell biological studies, mathematical modeling, and gene-manipulated mice models to illustrate the critical role of cFLIP as a switch to determine the destiny of cells among survival, apoptosis, and necroptosis.

  4. Thermomechanical behavior of tin-rich (lead-free) solders

    Science.gov (United States)

    Sidhu, Rajen Singh

    In order to adequately characterize the behavior of ball-grid-array (BGA) Pb-free solder spheres in electronic devices, the microstructure and thermomechanical behavior need to be studied. Microstructure characterization of pure Sn, Sn-0.7Cu, Sn-3.5Ag, and Sn-3.9Ag-0.7Cu alloys was conducted using optical microscopy, scanning electron microscopy, transmission electron microscopy, image analysis, and a novel serial sectioning 3D reconstruction process. Microstructure-based finite-element method (FEM) modeling of deformation in Sn-3.5Ag alloy was conducted, and it will be shown that this technique is more accurate when compared to traditional unit cell models for simulating and understanding material behavior. The effect of cooling rate on microstructure and creep behavior of bulk Sn-rich solders was studied. The creep behavior was evaluated at 25, 95, and 120°C. Faster cooling rates were found to increase the creep strength of the solders due to refinement of the solder microstructure. The creep behavior of Sn-rich single solder spheres reflowed on Cu substrates was studied at 25, 60, 95, and 130°C. Testing was conducted using a microforce testing system, with lap-shear geometry samples. The solder joints displayed two distinct creep behaviors: (a) precipitation-strengthening (Sn-3.5Ag and Sn-3.9Ag-0.7Cu) and (b) power law creep accommodated by grain boundary sliding (GBS) (Sn and Sn-0.7Cu). The relationship between microstructural features (i.e. intermetallic particle size and spacing), stress exponents, threshold stress, and activation energies are discussed. The relationship between small-length scale creep behavior and bulk behavior is also addressed. To better understand the damage evolution in Sn-rich solder joints during thermal fatigue, the local damage will be correlated to the cyclic hysteresis behavior and crystal orientations present in the Sn phase of solder joints. FEM modeling will also be utilized to better understand the macroscopic and local

  5. Flipped Cryptons and the UHECRs

    CERN Document Server

    Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John

    2004-01-01

    Cryptons are metastable bound states of fractionally-charged particles that arise generically in the hidden sectors of models derived from heterotic string. We study their properties and decay modes in a specific flipped SU(5) model with long-lived four-particle spin-zero bound states called {\\it tetrons}. We show that the neutral tetrons are metastable, and exhibit the ninth- and tenth-order non-renormalizable superpotential operators responsible for their dominant decays. By analogy with QCD, we expect charged tetrons to be somewhat heavier, and to decay relatively rapidly via lower-order interactions that we also exhibit. The expected masses and lifetimes of the neutral tetrons make them good candidates for cold dark matter (CDM), and a potential source of the ultra-high energy cosmic rays (UHECRs) which have been observed, whereas the charged tetrons would have decayed in the early Universe.

  6. Signatures of flipped SU(5)

    Energy Technology Data Exchange (ETDEWEB)

    Abel, S.A. (Bristol Univ. (UK). H.H. Wills Physics Lab.); Whittingham, I. (James Cook Univ. of North Queensland, Townsville (Australia). Dept. of Physics)

    1990-02-22

    We examine the electric dipole moment of the neutron and flavour changing Z decays in the flipped SU(5) grand unification scheme. We find that the new couplings at energy scales above M{sub GUT} can lead to neutron electric dipole moments vertical strokedvertical stroke{approx equal} 10{sup -25} e cm and decays of the form Z{yields}banti s, santi b with a branching ratio Bsub(Z{yields}banti s,santi b) {approx equal} 10{sup -6}, of which a large proportion ({epsilon}{le}1/4) may be CP violating. The first two effects are found to be slightly suppressed in the currently popular no-scale theories, but the CP violation parameter, {epsilon}, is relatively theory independent. (orig.).

  7. Flipped learning in science education

    DEFF Research Database (Denmark)

    Andersen, Thomas Dyreborg; Foss, Kristian Kildemoes; Nissen, Stine Karen

    2017-01-01

    During the last decade, massive investment in ICT has been made in Danish schools. There seems, however, to be a need to rethink how to better integrate ICT in education (Bundgaard et al. 2014 p. 216) Flipped learning might be a didactical approach that could contribute to finding a method to use...... research questions are “To what extent can teachers using the FL-teaching method improve Danish pupils' learning outcomes in science subject’s physics / chemistry, biology and geography in terms of the results of national tests?” And “What factors influence on whether FL-teaching improves pupils' learning...... will be addressed. Hereafter an array of different scaffolding activities will be conducted, among these are individual supervision, sharing of materials used in lessons and involving local school leaders in the program. During this 3-year period we will follow the progress of the students involved in the program...

  8. Front propagation in flipping processes

    International Nuclear Information System (INIS)

    Antal, T; Ben-Avraham, D; Ben-Naim, E; Krapivsky, P L

    2008-01-01

    We study a directed flipping process that underlies the performance of the random edge simplex algorithm. In this stochastic process, which takes place on a one-dimensional lattice whose sites may be either occupied or vacant, occupied sites become vacant at a constant rate and simultaneously cause all sites to the right to change their state. This random process exhibits rich phenomenology. First, there is a front, defined by the position of the leftmost occupied site, that propagates at a nontrivial velocity. Second, the front involves a depletion zone with an excess of vacant sites. The total excess Δ k increases logarithmically, Δ k ≅ ln k, with the distance k from the front. Third, the front exhibits ageing-young fronts are vigorous but old fronts are sluggish. We investigate these phenomena using a quasi-static approximation, direct solutions of small systems and numerical simulations

  9. Unifying flipped SU(5) in five dimensions

    International Nuclear Information System (INIS)

    Barr, S.M.; Dorsner, Ilja

    2002-01-01

    It is shown that embedding a four-dimensional flipped SU(5) model in a five-dimensional SO(10) model preserves the best features of both flipped SU(5) and SO(10). The missing partner mechanism, which naturally achieves both doublet-triplet splitting and suppression of d=5 proton decay operators, is realized as in flipped SU(5), while the gauge couplings are unified as in SO(10). The masses of down quarks and charged leptons, which are independent in flipped SU(5), are related by the SO(10). Distinctive patterns of quark and lepton masses can result. The gaugino mass M 1 is independent of M 3 and M 2 , which are predicted to be equal

  10. Equine First Aid Information Flip Booklet

    OpenAIRE

    Nay, Karah; Hoopes, Karl

    2017-01-01

    This is a flip chart type booklet with first aid information for horses, including checking vitals, pulse rate, respiration, mucus membrane color and capillary refill, signs of colic, deworming, vaccinations recommended for Utah, hoof care, and dental care.

  11. Flipped Science Inquiry@Crescent Girls' School

    Directory of Open Access Journals (Sweden)

    Peishi Goh

    2017-06-01

    Full Text Available This study shares the findings of a school-based Action Research project to explore how inquiry-based science practical lessons designed using the Flipped Science Inquiry@CGS classroom pedagogical model influence the way students learn scientific knowledge and also students' development of 21st century competencies, in particular, in the area of Knowledge Construction. Taking on a broader definition of the flipped classroom pedagogical model, the Flipped Science Inquiry@CGS framework adopts a structure that inverted the traditional science learning experience. Scientific knowledge is constructed through discussions with their peers, making use of their prior knowledge and their experiences while engaging in hands-on activities. Through the study, it is found that with the use of the Flipped Science Inquiry@CGS framework, learning experiences that are better aligned to the epistemology of science while developing 21st century competencies in students are created.

  12. How we flipped the medical classroom.

    Science.gov (United States)

    Sharma, Neel; Lau, C S; Doherty, Iain; Harbutt, Darren

    2015-04-01

    Flipping the classroom centres on the delivery of print, audio or video based material prior to a lecture or class session. The class session is then dedicated to more active learning processes with application of knowledge through problem solving or case based scenarios. The rationale behind this approach is that teachers can spend their face-to-face time supporting students in deeper learning processes. In this paper we provide a background literature review on the flipped classroom along with a three step approach to flipping the classroom comprising implementing, enacting and evaluating this form of pedagogy. Our three step approach is based on actual experience of delivering a flipped classroom at the University of Hong Kong. This initiative was evaluated with positive results. We hope our experience will be transferable to other medical institutions.

  13. En didaktisk model for Flipped Classroom

    DEFF Research Database (Denmark)

    Levinsen, Henrik; Foss, Kristian Kildemoes; Andersen, Thomas Dyreborg

    2016-01-01

    I artiklen præsenterer vi en model over flipped classroom som didaktisk metode udviklet med henblik på at stilladsere både de lærere, som gerne vil prøve kræfter med en flipped classroom-baseret praksis, og dem som allerede har erfaring, men kan have glæde af at bruge modellen til at kvalificere...... deres flipped classroom-undervisning. Modellen kan bidrage til erkendelsen af, at flipped classroom er noget nær et paradigmeskifte i forståelsen af god undervisning. Her tænkes på det skift i fokus metoden indebærer fra, at læreren er mest aktiv, til at eleverne er de mest aktive. Særligt for den...

  14. Creep deformation behavior in eutectic Sn-Ag solder joints using a novel mapping technique

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, J.P.; Guo, F.; McDougall, J.; Bieler, T.R.; Subramanian, K.N.; Park, J.K.

    1999-11-01

    Creep deformation behavior was measured for 60--100 {micro}m thick solder joints. The solder joints investigated consisted of: (1) non-composite solder joints made with eutectic Sn-Ag solder, and (2) composite solder joints with eutectic Sn-Ag solder containing 20 vol.%, 5 {micro}m diameter in-situ Cu{sub 6}Sn{sub 5} intermetallic reinforcements. All creep testing in this study was carried out at room temperature. Qualitative and quantitative assessment of creep deformation was characterized on the solder joints. Creep deformation was analyzed using a novel mapping technique where a geometrical-regular line pattern was etched over the entire solder joint using excimer laser ablation. During creep, the laser-ablation (LA) pattern becomes distorted due to deformation in the solder joint. By imaging the distortion of laser-ablation patterns using the SEM, actual deformation mapping for the entire solder joint is revealed. The technique involves sequential optical/digital imaging of the deformation versus time history during creep. By tracing and recording the deformation of the LA patterns on the solder over intervals of time, local creep data are obtained in many locations in the joint. This analysis enables global and localized creep shear strains and strain rate to be determined.

  15. Influence of solder joint length to the mechanical aspect during the thermal stress analysis

    Science.gov (United States)

    Tan, J. S.; Khor, C. Y.; Rahim, Wan Mohd Faizal Wan Abd; Ishak, Muhammad Ikman; Rosli, M. U.; Jamalludin, Mohd Riduan; Zakaria, M. S.; Nawi, M. A. M.; Aziz, M. S. Abdul; Ani, F. Che

    2017-09-01

    Solder joint is an important interconnector in surface mount technology (SMT) assembly process. The real time stress, strain and displacement of the solder joint is difficult to observe and assess the experiment. To tackle these problems, simulation analysis was employed to study the von Mises stress, strain and displacement in the thermal stress analysis by using Finite element based software. In this study, a model of leadless electronic package was considered. The thermal stress analysis was performed to investigate the effect of the solder length to those mechanical aspects. The simulation results revealed that solder length gives significant effect to the maximum von Mises stress to the solder joint. Besides, changes in solder length also influence the displacement of the solder joint in the thermal environment. The increment of the solder length significantly reduces the von Mises stress and strain on the solder joint. Thus, the understanding of the physical parameter for solder joint is important for engineer prior to designing the solder joint of the electronic component.

  16. High-Temperature Lead-Free Solder Alternatives: Possibilities and Properties

    DEFF Research Database (Denmark)

    High-temperature solders have been widely used as joining materials to provide stable interconnections that resist a severe thermal environment and also to facilitate the drive for miniaturization. High-lead containing solders have been commonly used as high-temperature solders. The development...... of high-temperature lead-free solders has become an important issue for both the electronics and automobile industries because of the health and environmental concerns associated with lead usage. Unfortunately, limited choices are available as high-temperature lead-free solders. This work outlines...... the criteria for the evaluation of a new high-temperature lead-free solder material. A list of potential ternary high-temperature lead-free solder alternatives based on the Au-Sn and Au-Ge systems is proposed. Furthermore, a comprehensive comparison of the high-temperature stability of microstructures...

  17. Reliability of lead-free solder joints with different PCB surface finishes under thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Xia Yanghua [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)], E-mail: xia_yanghua@hotmail.com; Xie Xiaoming [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2008-04-24

    The reliability of lead-free electronic assemblies under thermal cycling was investigated. Thin small outline package (TSOP) devices with FeNi leads were reflow soldered on FR4 PCB (printed circuit board) with Sn3.0Ag0.5Cu (wt%) solder. The effects of different PCB finishes (organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG)) were studied. The results show that OSP finish reveals better performance than its ENIG counterparts. The crack originates at the fringe of heel fillet in both cases. The propagation of crack in the ENIG case is along the device/solder interface, while in the case of OSP, the crack extends parallel to the solder/PCB interface. When the OSP finishes are employed, many Cu6Sn5 precipitates form inside the bulk solder and have a strengthening effect on the solder joint, resulting in better reliability performance as compared to those with ENIG finishes.

  18. Flips for 3-folds and 4-folds

    CERN Document Server

    Corti, Alessio

    2007-01-01

    This edited collection of chapters, authored by leading experts, provides a complete and essentially self-contained construction of 3-fold and 4-fold klt flips. A large part of the text is a digest of Shokurov's work in the field and a concise, complete and pedagogical proof of the existence of 3-fold flips is presented. The text includes a ten page glossary and is accessible to students and researchers in algebraic geometry.

  19. Resonant Homoclinic Flips Bifurcation in Principal Eigendirections

    Directory of Open Access Journals (Sweden)

    Tiansi Zhang

    2013-01-01

    Full Text Available A codimension-4 homoclinic bifurcation with one orbit flip and one inclination flip at principal eigenvalue direction resonance is considered. By introducing a local active coordinate system in some small neighborhood of homoclinic orbit, we get the Poincaré return map and the bifurcation equation. A detailed investigation produces the number and the existence of 1-homoclinic orbit, 1-periodic orbit, and double 1-periodic orbits. We also locate their bifurcation surfaces in certain regions.

  20. EFFECTIVENESS OF FLIPPED CLASSROOM IN MATHEMATICS TEACHING

    OpenAIRE

    Dr. N. Ramakrishnan; Mrs. J. Johnsi Priya

    2016-01-01

    Flipped Classroom is an instructional strategy and a type of blended learning that reverses the traditional learning environment by delivering instructional content, often online, outside of the classroom. It moves activities, including those that may have traditionally been considered homework, into the classroom. In a flipped classroom, students watch online lectures, collaborate in online discussions, or carry out research at home and engage in concepts in the classroom with the guidance o...

  1. Soldering and brazing safety guide: A handbook on space practice for those involved in soldering and brazing

    Science.gov (United States)

    This manual provides those involved in welding and brazing with effective safety procedures for use in performance of their jobs. Hazards exist in four types of general soldering and brazing processes: (1) cleaning; (2) application of flux; (3) application of heat and filler metal; and (4) residue cleaning. Most hazards during those operations can be avoided by using care, proper ventilation, protective clothing and equipment. Specific process hazards for various methods of brazing and soldering are treated. Methods to check ventilation are presented as well as a check of personal hygiene and good maintenance practices are stressed. Several emergency first aid treatments are described.

  2. Neutrino helicity flips via electroweak interactions

    International Nuclear Information System (INIS)

    Gaemers, K.J.F.; Gandhi, R.; Lattimer, J.M.; Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11794)

    1989-01-01

    Electroweak mechanisms via which neutrinos may flip helicity are examined in detail. Exact and approximate expressions for a variety of flip processes relevant in astrophysics and cosmology, mediated by W, Z, and γ exchange, including their interference, are derived for both Dirac and Majorana neutrinos (with emphasis on the former). It is shown that in general flip and nonflip cross sections differ by more than just a multiplicative factor of m/sub ν/ 2 /4E/sub ν/ 2 contrary to what might be expected and that this additional dependence on helicities can be significant. It is also shown that within the context of the standard model with massive neutrinos, for νe yields νe scattering, σ/sub Z//sup flip//σ/sub γ//sup flip/ ∼ 10 4 , independent of particle masses and energies to a good approximation. As an application, using some general considerations and the fact that the observed bar nu/sub e/ burst from SN 1987A lasted several seconds, these weak-interaction flip cross sections are used to rule out μ and tau neutrino masses above 30 keV. Finally, some other consequences for astrophysics in general and supernovae in particular are briefly discussed

  3. Ultra-thin silicon (UTSi) on insulator CMOS transceiver and time-division multiplexed switch chips for smart pixel integration

    Science.gov (United States)

    Zhang, Liping; Sawchuk, Alexander A.

    2001-12-01

    We describe the design, fabrication and functionality of two different 0.5 micron CMOS optoelectronic integrated circuit (OEIC) chips based on the Peregrine Semiconductor Ultra-Thin Silicon on insulator technology. The Peregrine UTSi silicon- on-sapphire (SOS) technology is a member of the silicon-on- insulator (SOI) family. The low-loss synthetic sapphire substrate is optically transparent and has good thermal conductivity and coefficient of thermal expansion properties, which meet the requirements for flip-chip bonding of VCSELs and other optoelectronic input-output components. One chip contains transceiver and network components, including four channel high-speed CMOS transceiver modules, pseudo-random bit stream (PRBS) generators, a voltage controlled oscillator (VCO) and other test circuits. The transceiver chips can operate in both self-testing mode and networking mode. An on- chip clock and true-single-phase-clock (TSPC) D-flip-flop have been designed to generate a PRBS at over 2.5 Gb/s for the high-speed transceiver arrays to operate in self-testing mode. In the networking mode, an even number of transceiver chips forms a ring network through free-space or fiber ribbon interconnections. The second chip contains four channel optical time-division multiplex (TDM) switches, optical transceiver arrays, an active pixel detector and additional test devices. The eventual applications of these chips will require monolithic OEICs with integrated optical input and output. After fabrication and testing, the CMOS transceiver array dies will be packaged with 850 nm vertical cavity surface emitting lasers (VCSELs), and metal-semiconductor- metal (MSM) or GaAs p-i-n detector die arrays to achieve high- speed optical interconnections. The hybrid technique could be either wire bonding or flip-chip bonding of the CMOS SOS smart-pixel arrays with arrays of VCSELs and photodetectors onto an optoelectronic chip carrier as a multi-chip module (MCM).

  4. Horizon shells and BMS-like soldering transformations

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Matthias [Albert Einstein Center for Fundamental Physics,Institute for Theoretical Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland); O’Loughlin, Martin [University of Nova Gorica,Vipavska 13, 5000 Nova Gorica (Slovenia)

    2016-03-07

    We revisit the theory of null shells in general relativity, with a particular emphasis on null shells placed at horizons of black holes. We study in detail the considerable freedom that is available in the case that one solders two metrics together across null hypersurfaces (such as Killing horizons) for which the induced metric is invariant under translations along the null generators. In this case the group of soldering transformations turns out to be infinite dimensional, and these solderings create non-trivial horizon shells containing both massless matter and impulsive gravitational wave components. We also rephrase this result in the language of Carrollian symmetry groups. To illustrate this phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild black hole (with equal interior and exterior mass), uncovering a rich classical structure at the horizon and deriving an explicit expression for the general horizon shell energy-momentum tensor. In the special case of BMS-like soldering supertranslations we find a conserved shell-energy that is strikingly similar to the standard expression for asymptotic BMS supertranslation charges, suggesting a direct relation between the physical properties of these horizon shells and the recently proposed BMS supertranslation hair of a black hole.

  5. Thermomechanical fatigue of Sn-37 wt.% Pb model solder joints

    International Nuclear Information System (INIS)

    Liu, X.W.; Plumbridge, W.J.

    2003-01-01

    The fatigue of Sn-37 wt.% Pb model solder joints has been investigated under thermomechanical and thermal cycling. Based upon an analysis of displacements during thermomechancial cycling, a model solder joint has been designed to simulate actual joints in electronic packages. The strain-stress relationship, characterised by hysteresis loops, was determined during cycling from 30 to 125 deg. C, and the stress-range monitored throughout. The number of cycles to failure, as defined by the fall in stress range, was correlated to strain range and strain energy. The strain hardening exponent, k, varied with the definition of failure and, when a stress-range drop of 50% was used, it was 0.46. Cracks were produced during pure thermal cycling without external strains applied. These arose due to the local strains caused by thermal expansion mismatches between the solder and Cu 6 Sn 5 intermetallic layer, between the phases of solder, and due to the anisotropy of the materials. The fatigue life under thermomechanical cycling was significantly inferior to that obtained in isothermal mechanical cycling. A factor contributing to this inferiority is the internal damage produced during temperature cycling

  6. Soluble Lead and Bismuth Chalcogenidometallates: Versatile Solders for Thermoelectric Materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hao [Department; Son, Jae Sung [Department; School; Dolzhnikov, Dmitriy S. [Department; Filatov, Alexander S. [Department; Hazarika, Abhijit [Department; Wang, Yuanyuan [Department; Hudson, Margaret H. [Department; Sun, Cheng-Jun [Advanced; Chattopadhyay, Soma [Physical; Talapin, Dmitri V. [Department; Center

    2017-07-27

    Here we report the syntheses of largely unexplored lead and bismuth chalcogenidometallates in the solution phase. Using N2H4 as the solvent, new compounds such as K6Pb3Te6·7N2H4 were obtained. These soluble molecular compounds underwent cation exchange processes using resin chemistry, replacing Na+ or K+ by decomposable N2H5+ or tetraethylammonium cations. They also transformed into stoichiometric lead and bismuth chalcogenide nanomaterials with the addition of metal salts. Such a versatile chemistry led to a variety of composition-matched solders to join lead and bismuth chalcogenides and tune their charge transport properties at the grain boundaries. Solution-processed thin films composed of Bi0.5Sb1.5Te3 microparticles soldered by (N2H5)6Bi0.5Sb1.5Te6 exhibited thermoelectric power factors (~28 μW/cm K2) comparable to those in vacuum-deposited Bi0.5Sb1.5Te3 films. The soldering effect can also be integrated with attractive fabrication techniques for thermoelectric modules, such as screen printing, suggesting the potential of these solders in the rational design of printable and moldable thermoelectrics.

  7. Effects of PCB thickness on adjustable fountain wave soldering

    Indian Academy of Sciences (India)

    hybrid circuit assembly, component lead tinning, and wire tinning. .... The mesh model was built and optimized with 599920 hybrid nodes as shown in figure 9. ... conducted to track the fluid motions of the two phases (i.e., molten solder and air).

  8. Detection of trans-cis flips and peptide-plane flips in protein structures

    NARCIS (Netherlands)

    Touw, W.G.; Joosten, R.P.; Vriend, G.

    2015-01-01

    A coordinate-based method is presented to detect peptide bonds that need correction either by a peptide-plane flip or by a trans-cis inversion of the peptide bond. When applied to the whole Protein Data Bank, the method predicts 4617 trans-cis flips and many thousands of hitherto unknown

  9. Confchem Conference on Flipped Classroom: Student Engagement with Flipped Chemistry Lectures

    Science.gov (United States)

    Seery, Michael K.

    2015-01-01

    This project introduces the idea of "flipped lecturing" to a group of second-year undergraduate students. The aim of flipped lecturing is to provide much of the "content delivery" of the lecture in advance, so that the lecture hour can be devoted to more in-depth discussion, problem solving, and so on. As well as development of…

  10. Does "Flipping" Promote Engagement?: A Comparison of a Traditional, Online, and Flipped Class

    Science.gov (United States)

    Burke, Alison S.; Fedorek, Brian

    2017-01-01

    "Flipped" or inverted classrooms are designed to utilize class time for application and knowledge building, while course content is delivered through the use of online lectures and watched at home on the students' time. It is believed that flipped classrooms promote student engagement and a deeper understanding of the class material. The…

  11. Detection of trans–cis flips and peptide-plane flips in protein structures

    International Nuclear Information System (INIS)

    Touw, Wouter G.; Joosten, Robbie P.; Vriend, Gert

    2015-01-01

    A method is presented to detect peptide bonds that need either a trans–cis flip or a peptide-plane flip. A coordinate-based method is presented to detect peptide bonds that need correction either by a peptide-plane flip or by a trans–cis inversion of the peptide bond. When applied to the whole Protein Data Bank, the method predicts 4617 trans–cis flips and many thousands of hitherto unknown peptide-plane flips. A few examples are highlighted for which a correction of the peptide-plane geometry leads to a correction of the understanding of the structure–function relation. All data, including 1088 manually validated cases, are freely available and the method is available from a web server, a web-service interface and through WHAT-CHECK

  12. Detection of trans–cis flips and peptide-plane flips in protein structures

    Energy Technology Data Exchange (ETDEWEB)

    Touw, Wouter G., E-mail: wouter.touw@radboudumc.nl [Radboud University Medical Center, Geert Grooteplein-Zuid 26-28, 6525 GA Nijmegen (Netherlands); Joosten, Robbie P. [Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands); Vriend, Gert, E-mail: wouter.touw@radboudumc.nl [Radboud University Medical Center, Geert Grooteplein-Zuid 26-28, 6525 GA Nijmegen (Netherlands)

    2015-07-28

    A method is presented to detect peptide bonds that need either a trans–cis flip or a peptide-plane flip. A coordinate-based method is presented to detect peptide bonds that need correction either by a peptide-plane flip or by a trans–cis inversion of the peptide bond. When applied to the whole Protein Data Bank, the method predicts 4617 trans–cis flips and many thousands of hitherto unknown peptide-plane flips. A few examples are highlighted for which a correction of the peptide-plane geometry leads to a correction of the understanding of the structure–function relation. All data, including 1088 manually validated cases, are freely available and the method is available from a web server, a web-service interface and through WHAT-CHECK.

  13. Soldering Characteristics and Mechanical Properties of Sn-1.0Ag-0.5Cu Solder with Minor Aluminum Addition

    Directory of Open Access Journals (Sweden)

    Yee Mei Leong

    2016-06-01

    Full Text Available Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag content solder SAC105 (Sn-1.0Ag-0.5Cu because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al addition (0.1–0.5 wt.% to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu3Al2. Cu3Al2 resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu6Sn5 intermetallic compound (IMC after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu6Sn5 IMC but has no significant effect on the thickness of Cu3Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface.

  14. Soldering Characteristics and Mechanical Properties of Sn-1.0Ag-0.5Cu Solder with Minor Aluminum Addition

    Science.gov (United States)

    Leong, Yee Mei; Haseeb, A.S.M.A.

    2016-01-01

    Driven by the trends towards miniaturization in lead free electronic products, researchers are putting immense efforts to improve the properties and reliabilities of Sn based solders. Recently, much interest has been shown on low silver (Ag) content solder SAC105 (Sn-1.0Ag-0.5Cu) because of economic reasons and improvement of impact resistance as compared to SAC305 (Sn-3.0Ag-0.5Cu. The present work investigates the effect of minor aluminum (Al) addition (0.1–0.5 wt.%) to SAC105 on the interfacial structure between solder and copper substrate during reflow. The addition of minor Al promoted formation of small, equiaxed Cu-Al particle, which are identified as Cu3Al2. Cu3Al2 resided at the near surface/edges of the solder and exhibited higher hardness and modulus. Results show that the minor addition of Al does not alter the morphology of the interfacial intermetallic compounds, but they substantially suppress the growth of the interfacial Cu6Sn5 intermetallic compound (IMC) after reflow. During isothermal aging, minor alloying Al has reduced the thickness of interfacial Cu6Sn5 IMC but has no significant effect on the thickness of Cu3Sn. It is suggested that of atoms of Al exert their influence by hindering the flow of reacting species at the interface. PMID:28773645

  15. Solder wetting behavior enhancement via laser-textured surface microcosmic topography

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Haiyan [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Shaanxi Key Laboratory of Friction Welding Technologies, Xi’an 710072 (China); Peng, Jianke [Shaanxi Key Laboratory of Friction Welding Technologies, Xi’an 710072 (China); Fu, Li, E-mail: fuli@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Shaanxi Key Laboratory of Friction Welding Technologies, Xi’an 710072 (China); Wang, Xincheng [Shaanxi Key Laboratory of Friction Welding Technologies, Xi’an 710072 (China); Xie, Yan [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China)

    2016-04-15

    Graphical abstract: - Highlights: • The wetting angle of lead free solder on Cu was reduced by surface microstructure. • The wetting form of Sn-Ag-Cu solder on Cu was “non-composite surface”. • The experimental results had a sound fit with the theoretical calculation. - Abstract: In order to reduce or even replace the use of Sn-Pb solder in electronics industry, the laser-textured surface microstructures were used to enhance the wetting behavior of lead free solder during soldering. According to wetting theory and Sn-Ag-Cu lead free solder performance, we calculated and designed four microcosmic structures with the similar shape and different sizes to control the wetting behavior of lead free solder. The micro-structured surfaces with different dimensions were processed on copper plates by fiber femtosecond laser, and the effect of microstructures on wetting behavior was verified experimentally. The results showed that the wetting angle of Sn-Ag-Cu solder on the copper plate with microstructures decreased effectively compared with that on the smooth copper plate. The wetting angles had a sound fit with the theoretical values calculated by wetting model. The novel method provided a feasible route for adjusting the wetting behavior of solders and optimizing solders system.

  16. Effects of soldering methods on tensile strength of a gold-palladium metal ceramic alloy.

    Science.gov (United States)

    Ghadhanfari, Husain A; Khajah, Hasan M; Monaco, Edward A; Kim, Hyeongil

    2014-10-01

    The tensile strength obtained by conventional postceramic application soldering and laser postceramic welding may require more energy than microwave postceramic soldering, which could provide similar tensile strength values. The purpose of the study was to compare the tensile strength obtained by microwave postceramic soldering, conventional postceramic soldering, and laser postceramic welding. A gold-palladium metal ceramic alloy and gold-based solder were used in this study. Twenty-seven wax specimens were cast in gold-palladium noble metal and divided into 4 groups: laser welding with a specific postfiller noble metal, microwave soldering with a postceramic solder, conventional soldering with the same postceramic solder used in the microwave soldering group, and a nonsectioned control group. All the specimens were heat treated to simulate a normal porcelain sintering sequence. An Instron Universal Testing Machine was used to measure the tensile strength for the 4 groups. The means were analyzed statistically with 1-way ANOVA. The surface and fracture sites of the specimens were subjectively evaluated for fracture type and porosities by using a scanning electron microscope. The mean (standard deviation) ultimate tensile strength values were as follows: nonsectioned control 818 ±30 MPa, microwave 516 ±34 MPa, conventional 454 ±37 MPa, and laser weld 191 ±39 MPa. A 1-way ANOVA showed a significant difference in ultimate tensile strength among the groups (F3,23=334.5; Ptensile strength for gold and palladium noble metals than either conventional soldering or laser welding. Conventional soldering resulted in a higher tensile strength than laser welding. Under the experimental conditions described, either microwave or conventional postceramic soldering would appear to satisfy clinical requirements related to tensile strength. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  17. Effects of Metallic Nanoparticles on Interfacial Intermetallic Compounds in Tin-Based Solders for Microelectronic Packaging

    Science.gov (United States)

    Haseeb, A. S. M. A.; Arafat, M. M.; Tay, S. L.; Leong, Y. M.

    2017-10-01

    Tin (Sn)-based solders have established themselves as the main alternative to the traditional lead (Pb)-based solders in many applications. However, the reliability of the Sn-based solders continues to be a concern. In order to make Sn-based solders microstructurally more stable and hence more reliable, researchers are showing great interest in investigating the effects of the incorporation of different nanoparticles into them. This paper gives an overview of the influence of metallic nanoparticles on the characteristics of interfacial intermetallic compounds (IMCs) in Sn-based solder joints on copper substrates during reflow and thermal aging. Nanocomposite solders were prepared by mechanically blending nanoparticles of nickel (Ni), cobalt (Co), zinc (Zn), molybdenum (Mo), manganese (Mn) and titanium (Ti) with Sn-3.8Ag-0.7Cu and Sn-3.5Ag solder pastes. The composite solders were then reflowed and their wetting characteristics and interfacial microstructural evolution were investigated. Through the paste mixing route, Ni, Co, Zn and Mo nanoparticles alter the morphology and thickness of the IMCs in beneficial ways for the performance of solder joints. The thickness of Cu3Sn IMC is decreased with the addition of Ni, Co and Zn nanoparticles. The thickness of total IMC layer is decreased with the addition of Zn and Mo nanoparticles in the solder. The metallic nanoparticles can be divided into two groups. Ni, Co, and Zn nanoparticles undergo reactive dissolution during solder reflow, causing in situ alloying and therefore offering an alternative route of alloy additions to solders. Mo nanoparticles remain intact during reflow and impart their influence as discrete particles. Mechanisms of interactions between different types of metallic nanoparticles and solder are discussed.

  18. Use of Flipped Classroom Technology in Language Learning

    OpenAIRE

    Evseeva, Arina Mikhailovna; Solozhenko, Anton

    2015-01-01

    The flipped classroom as a key component of blended learning arouses great interest among researchers and educators nowadays. The technology of flipped classroom implies such organization of the educational process in which classroom activities and homework assignments are reversed. The present paper gives the overview of the flipped classroom technology and explores its potential for both teachers and students. The authors present the results obtained from the experience of the flipped class...

  19. A wireless intraocular pressure monitoring device with a solder-filled microchannel antenna

    International Nuclear Information System (INIS)

    Varel, Çağdaş; Shih, Yi-Chun; Otis, Brian P; Böhringer, Karl F; Shen, Tueng S

    2014-01-01

    This paper presents the prototype of an intraocular pressure sensor as a major step toward building a device that can be permanently implanted during cataract surgery. The implantation will proceed through an incision of 2–3 mm using an injector, during which the complete device must be folded into a cross-section of 2 mm × 1 mm. The device uses radio frequency (RF) for wireless power and data transfer. The prototype includes an antenna, an RF chip and a pressure sensor assembled on a printed circuit board with several circuit components used for testing and calibration. The antenna is fabricated and integrated with the circuit using a fabrication method employing solder-filled microchannels embedded in an elastomer. The monitoring device is powered at 2.716 GHz from a distance of 1–2 cm. The prototype has undergone electrical and mechanical tests for antenna and sensor performance. The flexible antenna can withstand a stress of 33.4 kPa without any electrical disconnection. It did not show a significant increase in electrical resistance after 50 bending cycles with a maximum applied stress of 116 kPa. Transmitted pressure data shows an averaged sensitivity of 16.66 Hz (mm-Hg) –1 . (paper)

  20. The evidence for 'flipping out': A systematic review of the flipped classroom in nursing education.

    Science.gov (United States)

    Betihavas, Vasiliki; Bridgman, Heather; Kornhaber, Rachel; Cross, Merylin

    2016-03-01

    The flipped classroom has generated interest in higher education providing a student-centred approach to learning. This has the potential to engage nursing students in ways that address the needs of today's students and the complexity of contemporary healthcare. Calls for educational reform, particularly in healthcare programs such as nursing, highlight the need for students to problem-solve, reason and apply theory into practice. The drivers towards student-based learning have manifested in team, problem and case-based learning models. Though there has been a shift towards the flipped classroom, comparatively little is known about how it is used in nursing curricula. The aims of this systematic review were to examine how the flipped classroom has been applied in nursing education and outcomes associated with this style of teaching. Five databases were searched and resulted in the retrieval of 21 papers: PubMed, CINAHL, EMBASE, Scopus and ERIC. After screening for inclusion/exclusion criteria, each paper was evaluated using a critical appraisal tool. Data extraction and analysis were completed on all included studies. This systematic review screened 21 titles and abstracts resulting in nine included studies. All authors critically appraised the quality of the included studies. Five studies were identified and themes identified were: academic performance outcomes, and student satisfaction implementing the flipped classroom. Use of the flipped classroom in higher education nursing programmes yielded neutral or positive academic outcomes and mixed results for satisfaction. Engagement of students in the flipped classroom model was achieved when academics informed and rationalised the purpose of the flipped classroom model to students. However, no studies in this review identified the evaluation of the process of implementing the flipped classroom. Studies examining the process and ongoing evaluation and refinement of the flipped classroom in higher education nursing

  1. The metallurgical approach on the solder voids behaviour in surface mount devices

    International Nuclear Information System (INIS)

    Mohabattul Zaman Bukhari

    1996-01-01

    Solder voids are believed to cause poor heat dissiption in the Surface Mount devices and reduce the reliability of the devices at higher operating services. There are a lot of factors involved in creating voids such as gas/flux entrapment, wettability, outgasseous, air bubbles in the solder paste, inconsistency of solder coverage and improper metal scheme selection. This study was done to observe the behaviour of the solder voids in term of flux entrapmentt and wettability. It is believed that flux entrapment and wettability are verify this hypothesis. Two types of metal scheme were chosen which are Nickel (Ni) plated and Tin (Sn) plated heatsink. X-ray techniques such as Radiographic Inspection Analysis and EDAX were used to detect the minute solder voids. The solder voids observed on the heatsinks and Copper shims after the reflow process are believed to be a non contact voids that resulted from some portion of the surface not wetting properly

  2. Corrosive microenvironments at lead solder surfaces arising from galvanic corrosion with copper pipe.

    Science.gov (United States)

    Nguyen, Caroline K; Stone, Kendall R; Dudi, Abhijeet; Edwards, Marc A

    2010-09-15

    As stagnant water contacts copper pipe and lead solder (simulated soldered joints), a corrosion cell is formed between the metals in solder (Pb, Sn) and the copper. If the resulting galvanic current exceeds about 2 μA/cm(2), a highly corrosive microenvironment can form at the solder surface, with pH chloride concentrations at least 11 times higher than bulk water levels. Waters with relatively high chloride tend to sustain high galvanic currents, preventing passivation of the solder surface, and contributing to lead contamination of potable water supplies. The total mass of lead corroded was consistent with predictions based on the galvanic current, and lead leaching to water was correlated with galvanic current. If the concentration of sulfate in the water increased relative to chloride, galvanic currents and associated lead contamination could be greatly reduced, and solder surfaces were readily passivated.

  3. Impacts of Flipped Classroom in High School Health Education

    Science.gov (United States)

    Chen, Li-Ling

    2016-01-01

    As advanced technology increasingly infiltrated into classroom, the flipped classroom has come to light in secondary educational settings. The flipped classroom is a new instructional approach that intends to flip the traditional teacher-centered classroom into student centered. The purpose of this research is to investigate the impact of the…

  4. Dynamics of spin-flip photon-assisted tunneling

    NARCIS (Netherlands)

    Braakman, F.R.; Danon, J.; Schreiber, L.R.; Wegscheider, W.; Vandersypen, L.M.K.

    2014-01-01

    We present time-resolved measurements of spin-flip photon-assisted tunneling and spin-flip relaxation in a doubly occupied double quantum dot. The photon-assisted excitation rate as a function of magnetic field indicates that spin-orbit coupling is the dominant mechanism behind the spin-flip under

  5. Performance and Motivation in a Middle School Flipped Learning Course

    Science.gov (United States)

    Winter, Joshua W.

    2018-01-01

    Flipped learning is a teaching approach that promotes collaboration by using technology to 'flip' traditional instruction. Content is delivered outside of class in the individual space (online) and the group space (classroom) is used to engage in collaborative activities. Flipped learning shifts the teacher's role toward facilitation. Research on…

  6. Deep Exploration of the Flipped Classroom before Implementing

    Science.gov (United States)

    Logan, Brenda

    2015-01-01

    This paper is a review of the literature that attempts to explain and document the literature on the flipped classroom. It examines 49 studies that explain the flipped approach in the classroom. This paper, particularly, delineates the history, the theory, benefits, criticisms, recommended practices, and what the research on flipping reveals.…

  7. Applying the Flipped Classroom Model to English Language Arts Education

    Science.gov (United States)

    Young, Carl A., Ed.; Moran, Clarice M., Ed.

    2017-01-01

    The flipped classroom method, particularly when used with digital video, has recently attracted many supporters within the education field. Now more than ever, language arts educators can benefit tremendously from incorporating flipped classroom techniques into their curriculum. "Applying the Flipped Classroom Model to English Language Arts…

  8. High energy hadron spin-flip amplitude

    International Nuclear Information System (INIS)

    Selyugin, O.V.

    2016-01-01

    The high-energy part of the hadron spin-flip amplitude is examined in the framework of the new high-energy general structure (HEGS) model of the elastic hadron scattering at high energies. The different forms of the hadron spin-flip amplitude are compared in the impact parameter representation. It is shown that the existing experimental data of the proton-proton and proton-antiproton elastic scattering at high energy in the region of the diffraction minimum and at large momentum transfer give support in the presence of the energy-independent part of the hadron spin-flip amplitude with the momentum dependence proposed in the works by Galynskii-Kuraev. [ru

  9. Experimental plug and play quantum coin flipping

    Science.gov (United States)

    Pappa, Anna; Jouguet, Paul; Lawson, Thomas; Chailloux, André; Legré, Matthieu; Trinkler, Patrick; Kerenidis, Iordanis; Diamanti, Eleni

    2014-04-01

    Performing complex cryptographic tasks will be an essential element in future quantum communication networks. These tasks are based on a handful of fundamental primitives, such as coin flipping, where two distrustful parties wish to agree on a randomly generated bit. Although it is known that quantum versions of these primitives can offer information-theoretic security advantages with respect to classical protocols, a demonstration of such an advantage in a practical communication scenario has remained elusive. Here we experimentally implement a quantum coin flipping protocol that performs strictly better than classically possible over a distance suitable for communication over metropolitan area optical networks. The implementation is based on a practical plug and play system, developed by significantly enhancing a commercial quantum key distribution device. Moreover, we provide combined quantum coin flipping protocols that are almost perfectly secure against bounded adversaries. Our results offer a useful toolbox for future secure quantum communications.

  10. Interfacial reaction of Sn-based solder joint in the package system

    Science.gov (United States)

    Gu, Huandi

    In this thesis, I report a study on the effect of the solder size on intermetallic layer formation by comparing the morphology change and growth rate of two different size solder joint aged at a same temperature for different aging time. The layer thickness and microstructure were analyzed using scanning electron microscopy (SEM). Photoshop was used to measure the thickness of intermetallic compound. Two different size of solder joints with composition of Sn-Ag-Cu (305) were used.

  11. A new method for soldering particle-reinforced aluminum metal matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Jinbin; Mu, Yunchao [Zhongyuan University of Technology, Zhengzhou 450007 (China); Luo, Xiangwei [Zhengzhou University, Zhengzhou 450002 (China); Niu, Jitai, E-mail: niujitai@163.com [Zhongyuan University of Technology, Zhengzhou 450007 (China)

    2012-12-01

    Highlights: Black-Right-Pointing-Pointer Soldering of 55% SiCp/Al composite and Kovar is first achieved in the world. Black-Right-Pointing-Pointer The nickel plating is required on the surface of the composites before soldering. Black-Right-Pointing-Pointer Low welding temperature is set to avoid overheating of the matrix. Black-Right-Pointing-Pointer Chemical and metallurgical bonding of composites and Kovar is carried out. Black-Right-Pointing-Pointer High tension strength of 225 MPa in soldering seam has been obtained. - Abstract: Soldering of aluminum metal matrix composites (Al-SiC) to other structural materials, or even to themselves, has proved unsuccessful mainly due to the poor wetting of these composites by conventional soldering alloys. This paper reports a new approach, which improves the wetting properties of these composites by molting solder alloys to promote stronger bonds. The new approach relies on nickel-plating of the composite's faying surface prior to application of a solder alloy. Based on this approach, an aluminum metal matrix composite containing 55 vol.% SiC particles is successfully soldered to a Fe-Ni-Co alloy (commercially known as Kovar 4J29). The solder material is a zinc-based alloy (Zn-Cd-Ag-Cu) with a melting point of about 400 Degree-Sign C. Microscopic examinations of the aluminum metal matrix composites (Al-MMCs)-Kovar interfaces show that the nickel-plating, prior to soldering, could noticeably enhance the reaction between the molten solder and composites. The fractography of the shear-tested samples revealed that fracture occurs within the composite (i.e. cohesive failure), indicating a good adhesion between the solder alloy and the Al-SiC composite.

  12. A new method for soldering particle-reinforced aluminum metal matrix composites

    International Nuclear Information System (INIS)

    Lu, Jinbin; Mu, Yunchao; Luo, Xiangwei; Niu, Jitai

    2012-01-01

    Highlights: ► Soldering of 55% SiCp/Al composite and Kovar is first achieved in the world. ► The nickel plating is required on the surface of the composites before soldering. ► Low welding temperature is set to avoid overheating of the matrix. ► Chemical and metallurgical bonding of composites and Kovar is carried out. ► High tension strength of 225 MPa in soldering seam has been obtained. - Abstract: Soldering of aluminum metal matrix composites (Al–SiC) to other structural materials, or even to themselves, has proved unsuccessful mainly due to the poor wetting of these composites by conventional soldering alloys. This paper reports a new approach, which improves the wetting properties of these composites by molting solder alloys to promote stronger bonds. The new approach relies on nickel-plating of the composite's faying surface prior to application of a solder alloy. Based on this approach, an aluminum metal matrix composite containing 55 vol.% SiC particles is successfully soldered to a Fe–Ni–Co alloy (commercially known as Kovar 4J29). The solder material is a zinc-based alloy (Zn–Cd–Ag–Cu) with a melting point of about 400 °C. Microscopic examinations of the aluminum metal matrix composites (Al-MMCs)–Kovar interfaces show that the nickel-plating, prior to soldering, could noticeably enhance the reaction between the molten solder and composites. The fractography of the shear-tested samples revealed that fracture occurs within the composite (i.e. cohesive failure), indicating a good adhesion between the solder alloy and the Al–SiC composite.

  13. Higgs Mass Textures in Flipped SU(5)

    CERN Document Server

    Ellis, Jonathan Richard; Rizos, J; Ellis, John

    1999-01-01

    We analyze the Higgs doublet-triplet mass splitting problem in the version of flipped SU(5) derived from string theory. Analyzing non-renormalizable terms up to tenth order in the superpotential, we identify a pattern of field vev's that keeps one pair of electroweak Higgs doublets light, while all other Higgs doublets and all Higgs triplets are kept heavy, with the aid of the economical missing-doublet mechanism found in the field-theoretical version of flipped SU(5). The solution predicts that second-generation charge -1/3 quarks and charged leptons are much lighter than those in the third generation.

  14. Calculability and stability in the flipped string

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, J.L.; Nanopoulos, D.V. (Texas A and M Univ., College Station, TX (USA). Center for Theoretical Physics Houston Advanced Research Center (HARC), The Woodlands, TX (USA). Astroparticle Physics Group)

    1991-03-07

    We show that the highly successful structure of the recently proposed superstring flipped SU(5) model remains intact after the inclusion in the superpotential of the low-energy effective theory of all relevant string-induced nonrenormalizable terms. This structure provides for only two light Higgs doublets, hierarchical fermion mass matrices, and an adequate proton lifetime. We reach this conclusion explicit calculations using a recently derived set of rules to evaluate nonrenormalizable terms in the four-dimensional free fermionic formulation of superstrings. This remarkable stability of the infrared limit of the flipped string makes its experimental predictions trustworthy and hence its physical existence falsifiable. (orig.).

  15. Flipped neutrino emissivity from strange matter

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, A.; Dutta, S. (Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India))

    1994-04-15

    Energy loss due to wrong helicity sterile neutrinos through spin flip processes leads to rapid cooling of nascent neutron stars. The observed cooling of neutron stars associated with SN 1987A seems to preclude the existence of Dirac neutrinos with a mass in excess of 20 keV. Assuming that nuclear matter in the core of the neutron star undergoes a phase transition to quark matter leading to a strange star or a neutron star with a strange matter core, we examine the emission of flipped Dirac neutrinos for two dominant processes: quark-neutrino scattering [[ital q]+[nu][sub [minus

  16. Quenching of spin-flip quadrupole transitions

    International Nuclear Information System (INIS)

    Castel, B.; Blunden, P.; Okuhara, Y.

    1985-01-01

    An increasing amount of experimental data indicates that spin-flip quadrupole transitions exhibit quenching effects similar to those reported earlier in (p,n) reactions involving l = 0 and l = 1 transitions. We present here two model calculations suggesting that the E2 spin-flip transitions are more affected than their M1 and M3 counterparts by the tensor and spin-orbit components of the nuclear force and should exhibit the largest quenching. We also review the experimental evidence corroborating our observations

  17. Blended Course with Flipped Classroom Approach

    DEFF Research Database (Denmark)

    Timcenko, Olga; Purwins, Hendrik; Triantafyllou, Evangelia

    2015-01-01

    This paper presents and analyses design decisions and development process of producing teaching materials for a blended course with flipped classroom approach at bachelor level at Aalborg University in Copenhagen, Denmark. Our experiences, as well as students’ reactions and opinions will be descr......This paper presents and analyses design decisions and development process of producing teaching materials for a blended course with flipped classroom approach at bachelor level at Aalborg University in Copenhagen, Denmark. Our experiences, as well as students’ reactions and opinions...

  18. Just in Time to Flip Your Classroom

    OpenAIRE

    Lasry, Nathaniel; Dugdale, Michael; Charles, Elizabeth

    2013-01-01

    With advocates like Sal Khan and Bill Gates, flipped classrooms are attracting an increasing amount of media and research attention. We had heard Khan's TED talk and were aware of the concept of inverted pedagogies in general. Yet, it really hit home when we accidentally flipped our classroom. Our objective was to better prepare our students for class. We set out to effectively move some of our course content outside of class and decided to tweak the Just-in-Time-Teaching approach (JiTT). To ...

  19. Flipped Classrooms for Advanced Science Courses

    Science.gov (United States)

    Tomory, Annette; Watson, Sunnie Lee

    2015-12-01

    This article explains how issues regarding dual credit and Advanced Placement high school science courses could be mitigated via a flipped classroom instructional model. The need for advanced high school courses will be examined initially, followed by an analysis of advanced science courses and the reform they are experiencing. Finally, it will conclude with an explanation of flipped classes as well as how they may be a solution to the reform challenges teachers are experiencing as they seek to incorporate more inquiry-based activities.

  20. Laser tissue welding mediated with a protein solder

    Science.gov (United States)

    Small, Ward, IV; Heredia, Nicholas J.; Celliers, Peter M.; Da Silva, Luiz B.; Eder, David C.; Glinsky, Michael E.; London, Richard A.; Maitland, Duncan J.; Matthews, Dennis L.; Soltz, Barbara A.

    1996-05-01

    A study of laser tissue welding mediated with an indocyanine green dye-enhanced protein solder was performed. Freshly obtained sections of porcine artery were used for the experiments. Sample arterial wall thickness ranged from two to three millimeters. Incisions approximately four millimeters in length were treated using an 805 nanometer continuous- wave diode laser coupled to a one millimeter diameter fiber. Controlled parameters included the power delivered by the laser, the duration of the welding process, and the concentration of dye in the solder. A two-color infrared detection system was constructed to monitor the surface temperatures achieved at the weld site. Burst pressure measurements were made to quantify the strengths of the welds immediately following completion of the welding procedure.

  1. Quality Analysis of Welded and Soldered Joints of Cu-Nb Microcomposite Wires

    Directory of Open Access Journals (Sweden)

    Nikolaj VIŠNIAKOV

    2011-03-01

    Full Text Available Quality analysis of welded and soldered joints of Cu-Nb microcomposite wires has been performed. Quality and mechanical characteristics of joints as ultimate tensile stress limit and elongation at break were measured with an universal testing machine and controlled visually using an optical microscope. Two wires joints were soldered with silver and copper solders and put into steel and copper sleeve respectively. Another two wires joints were soldered with silver solder and welded without any reinforcement. Joints soldered with the silver solder and steel sleeve have demonstrated the best mechanical characteristics: ultimate tensile stress limit of 650 MPa and elongation at break of 0.85 %. Joints soldered with the copper sleeve have no advantages comparing with the soldered butt joint. Ultimate tensile stress limit and elongation at break were in 300 MPa - 350 MPa and in 0.35 % - 0.45 % ranges respectively. Two welded joints had ultimate tensile stress limit of 470 MPa and elongation at break of 0.71 %. In all joints the microstructure of Nb filaments was destroyed and mechanical properties have been specified by mechanical strength of copper and sleeve materials only.http://dx.doi.org/10.5755/j01.ms.17.1.242

  2. Reliability of soldered joints for automotive electronic devices; Denso buhin ni okeru handa setsugo no shinraisei

    Energy Technology Data Exchange (ETDEWEB)

    Kita, T; Mukaibo, N; Ando, K; Moriyama, M [Honda R and D Co. Ltd., Tokyo (Japan)

    1997-10-01

    Concerning the tin and lead eutectic solder, we have evaluated the reliability of three factors of intermetallic compound layer, creep and vibration which cause solder degradation. First, the stress factor was extracted from investigating the mechanism of degradation, and the best acceleration test method was fixed. Next, the acceleration test was executed to find the stress dependency and the tendency of solder degradation was modeled numerically. While the environmental stress frequency was obtained and they were put together by using a minor method, which enabled us to predict the life span of solder on the market with precision. 5 refs., 13 figs.

  3. The effect of graphene on the intermetallic and joint strength of Sn-3.5Ag lead-free solder

    Science.gov (United States)

    Mayappan, R.; Salleh, A.; Andas, J.

    2017-09-01

    Solder has been widely used in electronic industry as interconnection for electronic packaging. European Union and Japan have restricted the use of Sn-Pb solder as it contains lead which can harmful to human health and environment. Due to this, many researches have been done in order to find a suitable replacement for the lead solder. Although many lead-free solders are available, the Sn-3.5Ag solder with the addition of graphene seem to be a suitable candidate. In this study, a 0.07 wt% graphene nanosheet was added into the Sn-3.5Ag solder and this composite solder was prepared under powder metallurgy method. The solder was reacted with copper substrate at 250 °C for one minute. For joint strength analysis, two copper strips were soldered together. The solder joint was aged at temperature 100 °C for 500 hours. Scanning Electron Microscope (SEM) was used to observe the interfacial reaction and Instron machine was used to determine the joint strength. Cu6Sn5 intermetallic layer was formed at the interface between the Cu substrate and the solders. Composite solder showed the retardation of the intermetallic growth compared to the plain solder. The thickness value of the intermetallic was used to calculate the growth rate the IMC. The graphene nanosheets added solder has lower growth rate which is 3.86 × 10-15 cm2/s compared to the plain solder 7.15 × 10-15 cm2/s. Shear strength analysis show that the composite solder has higher joint compared to the plain solder.

  4. All-optical SR flip-flop based on SOA-MZI switches monolithically integrated on a generic InP platform

    Science.gov (United States)

    Pitris, St.; Vagionas, Ch.; Kanellos, G. T.; Kisacik, R.; Tekin, T.; Broeke, R.; Pleros, N.

    2016-03-01

    At the dawning of the exaflop era, High Performance Computers are foreseen to exploit integrated all-optical elements, to overcome the speed limitations imposed by electronic counterparts. Drawing from the well-known Memory Wall limitation, imposing a performance gap between processor and memory speeds, research has focused on developing ultra-fast latching devices and all-optical memory elements capable of delivering buffering and switching functionalities at unprecedented bit-rates. Following the master-slave configuration of electronic Flip-Flops, coupled SOA-MZI based switches have been theoretically investigated to exceed 40 Gb/s operation, provided a short coupling waveguide. However, this flip-flop architecture has been only hybridly integrated with silica-on-silicon integration technology exhibiting a total footprint of 45x12 mm2 and intra-Flip-Flop coupling waveguide of 2.5cm, limited at 5 Gb/s operation. Monolithic integration offers the possibility to fabricate multiple active and passive photonic components on a single chip at a close proximity towards, bearing promises for fast all-optical memories. Here, we present for the first time a monolithically integrated all-optical SR Flip-Flop with coupled master-slave SOA-MZI switches. The photonic chip is integrated on a 6x2 mm2 die as a part of a multi-project wafer run using library based components of a generic InP platform, fiber-pigtailed and fully packaged on a temperature controlled ceramic submount module with electrical contacts. The intra Flip-Flop coupling waveguide is 5 mm long, reducing the total footprint by two orders of magnitude. Successful flip flop functionality is evaluated at 10 Gb/s with clear open eye diagram, achieving error free operation with a power penalty of 4dB.

  5. Laser beam soldering of micro-optical components

    Science.gov (United States)

    Eberhardt, R.

    2003-05-01

    MOTIVATION Ongoing miniaturisation and higher requirements within optical assemblies and the processing of temperature sensitive components demands for innovative selective joining techniques. So far adhesive bonding has primarily been used to assemble and adjust hybrid micro optical systems. However, the properties of the organic polymers used for the adhesives limit the application of these systems. In fields of telecommunication and lithography, an enhancement of existing joining techniques is necessary to improve properties like humidity resistance, laserstability, UV-stability, thermal cycle reliability and life time reliability. Against this background laser beam soldering of optical components is a reasonable joining technology alternative. Properties like: - time and area restricted energy input - energy input can be controlled by the process temperature - direct and indirect heating of the components is possible - no mechanical contact between joining tool and components give good conditions to meet the requirements on a joining technology for sensitive optical components. Additionally to the laser soldering head, for the assembly of optical components it is necessary to include positioning units to adjust the position of the components with high accuracy before joining. Furthermore, suitable measurement methods to characterize the soldered assemblies (for instance in terms of position tolerances) need to be developed.

  6. uFlip: Understanding Flash IO Patterns

    DEFF Research Database (Denmark)

    Bouganim, Luc; Jonsson, Bjørn; Bonnet, Philippe

    2009-01-01

    want to establish what kind of IOs should be favored (or avoided) when designing algorithms and architectures for flash-based systems. In this paper, we focus on flash IO patterns, that capture relevant distribution of IOs in time and space, and our goal is to quantify their performance. We define uFLIP...

  7. Flipped Instruction: Breakthroughs in Research and Practice

    Science.gov (United States)

    IGI Global, 2017

    2017-01-01

    The integration of technology into modern classrooms has enhanced learning opportunities for students. With increased access to educational content, students gain a better understanding of the concepts being taught. "Flipped Instruction: Breakthroughs in Research and Practice" is a comprehensive reference source for the latest scholarly…

  8. Intertwiner dynamics in the flipped vertex

    Energy Technology Data Exchange (ETDEWEB)

    Alesci, Emanuele; Bianchi, Eugenio; Magliaro, Elena; Perini, Claudio, E-mail: alesci@fis.uniroma3.i, E-mail: e.bianchi@sns.i, E-mail: elena.magliaro@gmail.co, E-mail: claude.perin@libero.i [Centre de Physique Theorique de Luminy, Case 907, F-13288 Marseille (France)

    2009-09-21

    We continue the semiclassical analysis, started in a previous paper, of the intertwiner sector of the flipped vertex spinfoam model. We use independently both a semi-analytical and a purely numerical approach, finding the correct behavior of wavepacket propagation and physical expectation values. In the end, we show preliminary results about correlation functions.

  9. Natural strong CP conservation in flipped physics

    Energy Technology Data Exchange (ETDEWEB)

    Frampton, P.H. (Institute of Field Physics, Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC (USA)); Kephart, T.W. (Department of Physics and Astronomy, Vanderbilt University, Nashville, TN (USA))

    1990-08-13

    A natural axion-free solution of the strong {ital CP} problem {ital at} {ital tree} {ital level} is noted within an E(6) grand unified theory. Using this as a springboard, it is shown that several flipped SU(5) theories which occur in superstring phenomenology contain within them a mechanism which enforces {bar {theta}}=0 at high accuracy.

  10. Flipping an Agricultural Education Teaching Methods Course

    Science.gov (United States)

    Conner, Nathan W.; Stripling, Christopher T.; Blythe, Jessica M.; Roberts, T. Grady; Stedman, Nicole L. P.

    2014-01-01

    Flipping or inverting a course is a relatively new approach to structuring a course. Using this method, the lectures traditionally delivered during regularly scheduled class time are converted to a media for delivery online, often in the form of videos. Learners are expected to view the online lectures prior to class. Then in turn, in-class time…

  11. The Flipped Classroom in World History

    Science.gov (United States)

    Gaughan, Judy E.

    2014-01-01

    The flipped Classroom is one in which lectures are presented as homework outside of class in online videos so that class time is reserved for engaging directly with the materials. This technique offers more personalized guidance and interaction with students, instead of lecturing. In this article, Judy Gaughan details her journey through choosing…

  12. Exploring Flipped Classroom Instruction in Calculus III

    Science.gov (United States)

    Wasserman, Nicholas H.; Quint, Christa; Norris, Scott A.; Carr, Thomas

    2017-01-01

    In an undergraduate Calculus III class, we explore the effect of "flipping" the instructional delivery of content on both student performance and student perceptions. Two instructors collaborated to determine daily lecture notes, assigned the same homework problems, and gave identical exams; however, compared to a more traditional…

  13. Flip-flopping binary black holes.

    Science.gov (United States)

    Lousto, Carlos O; Healy, James

    2015-04-10

    We study binary spinning black holes to display the long term individual spin dynamics. We perform a full numerical simulation starting at an initial proper separation of d≈25M between equal mass holes and evolve them down to merger for nearly 48 orbits, 3 precession cycles, and half of a flip-flop cycle. The simulation lasts for t=20 000M and displays a total change in the orientation of the spin of one of the black holes from an initial alignment with the orbital angular momentum to a complete antialignment after half of a flip-flop cycle. We compare this evolution with an integration of the 3.5 post-Newtonian equations of motion and spin evolution to show that this process continuously flip flops the spin during the lifetime of the binary until merger. We also provide lower order analytic expressions for the maximum flip-flop angle and frequency. We discuss the effects this dynamics may have on spin growth in accreting binaries and on the observational consequences for galactic and supermassive binary black holes.

  14. The Pedagogy of Flipped Instruction in Oman

    Science.gov (United States)

    Lane-Kelso, Mary

    2015-01-01

    "Flipping the classroom", or reverse instruction has been hailed the new pedagogical approach for preparing students for the 21st century. The idea behind this method is relatively simple. Instead of structuring class work to deliver direct instruction from the teacher in class and giving homework to students to practice outside of…

  15. Flipping Undergraduate Finite Mathematics: Findings and Implications

    Science.gov (United States)

    Guerrero, Shannon; Beal, Melissa; Lamb, Chris; Sonderegger, Derek; Baumgartel, Drew

    2015-01-01

    This paper reports on a research project that investigated the effects of a flipped instructional approach on student attitudes and achievement in a lower division university-level Finite Mathematics course. The project employed a mixed-methods design that included content exams, an attitude survey, open-ended student responses, observations, and…

  16. Pixel detector readout chip

    CERN Multimedia

    1991-01-01

    Close-up of a pixel detector readout chip. The photograph shows an aera of 1 mm x 2 mm containing 12 separate readout channels. The entire chip contains 1000 readout channels (around 80 000 transistors) covering a sensitive area of 8 mm x 5 mm. The chip has been mounted on a silicon detector to detect high energy particles.

  17. 30 CFR 77.1111 - Welding, cutting, soldering; use of fire extinguisher.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Welding, cutting, soldering; use of fire... OF UNDERGROUND COAL MINES Fire Protection § 77.1111 Welding, cutting, soldering; use of fire extinguisher. One portable fire extinguisher shall be provided at each location where welding, cutting, or...

  18. Tissue soldering with biodegradable polymer films: in-vitro investigation of hydration effects on weld strength

    Science.gov (United States)

    Sorg, Brian S.; Welch, Ashley J.

    2001-05-01

    Previous work demonstrated increased breaking strengths of tissue repaired with liquid albumin solder reinforced with a biodegradable polymer film compared to unreinforced control specimens. It was hypothesized that the breaking strength increase was due to reinforcement of the liquid solder cohesive strength. Immersion in a moist environment can decrease the adhesion of solder to tissue and negate any strength benefits gained from reinforcement. The purpose of this study was to determine if hydrated specimens repaired with reinforced solder would still be stronger than unreinforced controls. A 50%(w/v) bovine serum albumin solder with 0.5 mg/mL Indocyanine Green dye was used to repair an incision in bovine aorta. The solder was coagulated with 806-nm diode laser light. A poly(DL-lactic- co-glycolic acid) film was used to reinforce the solder (the controls had no reinforcement). The repaired tissues were immersed in phosphate buffered saline for time periods of 1 and 2 days. The breaking strengths of all of the hydrated specimens decreased compared to the acute breaking strengths. However, the reinforced specimens still had larger breaking strengths than the unreinforced controls. These results indicate that reinforcement of a liquid albumin solder may have the potential to improve the breaking strength in a clinical setting.

  19. Current Problems and Possible Solutions in High-Temperature Lead-Free Soldering

    Czech Academy of Sciences Publication Activity Database

    Kroupa, Aleš; Andersson, D.; Hoo, N.; Pearce, J.; Watson, A.; Dinsdale, A.; Mucklejohn, S.

    2012-01-01

    Roč. 21, č. 5 (2012), s. 629-637 ISSN 1059-9495 Institutional support: RVO:68081723 Keywords : lead-free soldering, * materials for high-temperature LF * new technologies for HT lead-free soldering Subject RIV: BJ - Thermodynamics Impact factor: 0.915, year: 2012

  20. Effect of Strain Rate on Joint Strength and Failure Mode of Lead-Free Solder Joints

    Science.gov (United States)

    Lin, Jian; Lei, Yongping; Fu, Hanguang; Guo, Fu

    2018-03-01

    In surface mount technology, the Sn-3.0Ag-0.5Cu solder joint has a shorter impact lifetime than a traditional lead-tin solder joint. In order to improve the impact property of SnAgCu lead-free solder joints and identify the effect of silver content on tensile strength and impact property, impact experiments were conducted at various strain rates on three selected SnAgCu based solder joints. It was found that joint failure mainly occurred in the solder material with large plastic deformation under low strain rate, while joint failure occurred at the brittle intermetallic compound layer without any plastic deformation at a high strain rate. Joint strength increased with the silver content in SnAgCu alloys in static tensile tests, while the impact property of the solder joint decreased with increasing silver content. When the strain rate was low, plastic deformation occurred with failure and the tensile strength of the Sn-3.0Ag-0.5Cu solder joint was higher than that of Sn-0.3Ag-0.7Cu; when the strain rate was high, joint failure mainly occurred at the brittle interface layer and the Sn-0.3Ag-0.7Cu solder joint had a better impact resistance with a thinner intermetallic compound layer.

  1. Development of technique for laser welding of biological tissues using laser welding device and nanocomposite solder.

    Science.gov (United States)

    Gerasimenko, A; Ichcitidze, L; Podgaetsky, V; Ryabkin, D; Pyankov, E; Saveliev, M; Selishchev, S

    2015-08-01

    The laser device for welding of biological tissues has been developed involving quality control and temperature stabilization of weld seam. Laser nanocomposite solder applied onto a wound to be weld has been used. Physicochemical properties of the nanocomposite solder have been elucidated. The nature of the tissue-organizing nanoscaffold has been analyzed at the site of biotissue welding.

  2. Failure Mechanisms of SAC/Fe-Ni Solder Joints During Thermal Cycling

    Science.gov (United States)

    Gao, Li-Yin; Liu, Zhi-Quan; Li, Cai-Fu

    2017-08-01

    Thermal cycling tests have been conducted on Sn-Ag-Cu/Fe- xNi ( x = 73 wt.% or 45 wt.%) and Sn-Ag-Cu/Cu solder joints according to the Joint Electron Device Engineering Council industrial standard to study their interfacial reliability under thermal stress. The interfacial intermetallic compounds formed for solder joints on Cu, Fe-73Ni, and Fe-45Ni were 4.5 μm, 1.7 μm, and 1.4 μm thick, respectively, after 3000 cycles, demonstrating excellent diffusion barrier effect of Fe-Ni under bump metallization (UBM). Also, two deformation modes, viz. solder extrusion and fatigue crack formation, were observed by scanning electron microscopy and three-dimensional x-ray microscopy. Solder extrusion dominated for solder joints on Cu, while fatigue cracks dominated for solder joints on Fe-45Ni and both modes were detected for those on Fe-73Ni. Solder joints on Fe-Ni presented inferior reliability during thermal cycling compared with those on Cu, with characteristic lifetime of 3441 h, 3190 h, and 1247 h for Cu, Fe-73Ni, and Fe-45Ni UBM, respectively. This degradation of the interfacial reliability for solder joints on Fe-Ni is attributed to the mismatch in coefficient of thermal expansion (CTE) at interconnection level. The CTE mismatch at microstructure level was also analyzed by electron backscatter diffraction for clearer identification of recrystallization-related deformation mechanisms.

  3. Corrosion Reliability of Lead-free Solder Systems Used in Electronics

    DEFF Research Database (Denmark)

    Li, Feng; Verdingovas, Vadimas; Medgyes, Balint

    2017-01-01

    humidity/temperature cycling tests on soldered surface insulation resistance (SIR) comb pattern. Complimentary microstructural and phase analysis of solder alloys has been carried out using the scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) methods...

  4. Reliability and microstructure of lead-free solder joints in industrial electronics after accelerated thermal aging

    NARCIS (Netherlands)

    Scaltro, F.; Biglari, M.H.; Kodentsov, A.; Yakovleva, O.; Brom, E.

    2009-01-01

    The reliability of lead-free (LF) solder joints in surface-mounted device components (SMD) has been investigated after thermo-cycle testing. Kirkendall voids have been observed at the interface component/solder together with the formation of fractures. The evolution, the morphology and the elemental

  5. Investigation of moisture uptake into printed circuit board laminate and solder mask materials

    DEFF Research Database (Denmark)

    Conseil, Helene; Gudla, Visweswara Chakravarthy; Borgaonkar, Shruti

    2017-01-01

    with different solder mask materials and exposed to saturated water vapour and liquid water. The solder masks are characterised for their microstructure and constituent phases using scanning electron microscopy and X-ray diffraction. The observations are correlated with themoisture absorption characteristic...

  6. Properties and Microstructures of Sn-Bi-X Lead-Free Solders

    Directory of Open Access Journals (Sweden)

    Fan Yang

    2016-01-01

    Full Text Available The Sn-Bi base lead-free solders are proposed as one of the most popular alloys due to the low melting temperature (eutectic point: 139°C and low cost. However, they are not widely used because of the lower wettability, fatigue resistance, and elongation compared to traditional Sn-Pb solders. So the alloying is considered as an effective way to improve the properties of Sn-Bi solders with the addition of elements (Al, Cu, Zn, Ga, Ag, In, Sb, and rare earth and nanoparticles. In this paper, the development of Sn-Bi lead-free solders bearing elements and nanoparticles was reviewed. The variation of wettability, melting characteristic, electromigration, mechanical properties, microstructures, intermetallic compounds reaction, and creep behaviors was analyzed systematically, which can provide a reference for investigation of Sn-Bi base solders.

  7. Effect of phosphorus element on the comprehensive properties of Sn-Cu lead-free solder

    International Nuclear Information System (INIS)

    Li Guangdong; Shi Yaowu; Hao Hu; Xia Zhidong; Lei Yongping; Guo Fu

    2010-01-01

    In the present work, the effect of phosphorus on the creep fatigue properties of Sn-Cu eutectic lead-free solder was carried out. The experimental results show that the melting temperature was almost not changed with adding small amount of P element. However, the addition of trace P element led to the decrease in the property of creep fatigue. The fractography analysis by a scanning electron microscopy (SEM) shows that ductile fracture was the dominant failure behavior in the process of creep fatigue test of Sn0.7Cu and Sn0.7Cu0.005P specimens. It should be pointed out that there is significant difference in the fractographs between the joints of Sn0.7Cu solder and Sn0.7Cu0.005P solder. In the fractograph of Sn0.7Cu solder joint, the microstructure is prolonged along testing direction, and the dimples were more than the fractograph of Sn0.7Cu0.005P solder joint. In addition, the voids could be found on the Sn0.7Cu0.005P solder joint, and trace P addition may increase the rate of forming void of Sn0.7Cu solder joint. The voids can potentially lead to crack initiation or propagation sites in the solder joint. As a result, the creep fatigue of solder joint containing P such as Sn0.7Cu0.005P offers worse property compared to Sn0.7Cu solder joint.

  8. Physical properties of lead free solders in liquid and solid state

    Energy Technology Data Exchange (ETDEWEB)

    Mhiaoui, Souad

    2007-04-17

    The European legislation prohibits the use of lead containing solders in Europe. However, lead free solders have a higher melting point (typical 20%) and their mechanical characteristics are worse. Additional problems are aging and adhesion of the solder on the electronic circuits. Thus, research activities must focus on the optimization of the properties of Sn-Ag-Cu based lead free solders chosen by the industry. Two main objectives are treated in this work. In the center of the first one is the study of curious hysteresis effects of metallic cadmium-antimony alloys after thermal cycles by measuring electronic transport phenomena (thermoelectric power and electrical resistivity). The second objective, within the framework of ''cotutelle'' between the universities of Metz and of Chemnitz and supported by COST531, is to study more specifically lead free solders. A welding must well conduct electricity and well conduct and dissipate heat. In Metz, we determined the electrical conductivity, the thermoelectric power and the thermal conductivity of various lead free solders (Sn-Ag-Cu, Sn-Cu, Sn-Ag, Sn-Sb) as well in the liquid as well in the solid state. The results have been compared to classical lead-tin (Pb-Sn) solders. In Chemnitz we measured the surface tension, the interfacial tension and the density of lead free solders. We also measured the viscosity of these solders without and with additives, in particular nickel. These properties were related to the industrial problems of wettability and spreadability. Lastly, we solidified alloys under various conditions. We observed undercooling. We developed a technique of mixture of nanocrystalline powder with lead free solders ''to sow'' the liquid bath in order to obtain ''different'' solids which were examined using optical and electron microscopy. (orig.)

  9. Effect of phosphorus element on the comprehensive properties of Sn-Cu lead-free solder

    Energy Technology Data Exchange (ETDEWEB)

    Li Guangdong, E-mail: liguangdong@emails.bjut.edu.c [College of Materials Science and Engineering, Beijing University of Technology, 100 Ping Le Yuan, Chaoyang District, Beijing 100124 (China); Shi Yaowu; Hao Hu; Xia Zhidong; Lei Yongping; Guo Fu [College of Materials Science and Engineering, Beijing University of Technology, 100 Ping Le Yuan, Chaoyang District, Beijing 100124 (China)

    2010-02-18

    In the present work, the effect of phosphorus on the creep fatigue properties of Sn-Cu eutectic lead-free solder was carried out. The experimental results show that the melting temperature was almost not changed with adding small amount of P element. However, the addition of trace P element led to the decrease in the property of creep fatigue. The fractography analysis by a scanning electron microscopy (SEM) shows that ductile fracture was the dominant failure behavior in the process of creep fatigue test of Sn0.7Cu and Sn0.7Cu0.005P specimens. It should be pointed out that there is significant difference in the fractographs between the joints of Sn0.7Cu solder and Sn0.7Cu0.005P solder. In the fractograph of Sn0.7Cu solder joint, the microstructure is prolonged along testing direction, and the dimples were more than the fractograph of Sn0.7Cu0.005P solder joint. In addition, the voids could be found on the Sn0.7Cu0.005P solder joint, and trace P addition may increase the rate of forming void of Sn0.7Cu solder joint. The voids can potentially lead to crack initiation or propagation sites in the solder joint. As a result, the creep fatigue of solder joint containing P such as Sn0.7Cu0.005P offers worse property compared to Sn0.7Cu solder joint.

  10. An Approach for Impression Creep of Lead Free Microelectronic Solders

    Science.gov (United States)

    Anastasio, Onofrio A.

    2002-06-01

    Currently, the microelectronics industry is transitioning from lead-containing to lead-free solders in response to legislation in the EU and Japan. Before an alternative alloy can be designated as a replacement for current Pb-Sn extensive testing must be accomplished. One major characteristic of the alloy that must be considered is creep. Traditionally, creep testing requires numerous samples and a long tin, which thwarts the generation of comprehensive creep databases for difficult to prepare samples such as microelectronic solder joints. However, a relatively new technique, impression creep enables us to rapidly generate creep data. This test uses a cylindrical punch with a flat end to make an impression on the surface of a specimen under constant load. The steady state velocity of the indenter is found to have the same stress and temperature dependence as the conventional unidirectional creep test using bulk specimens. This thesis examines impression creep tests of eutectic Sn-Ag. A testing program and apparatus was developed constructed based on a servo hydraulic test frame. The apparatus is capable of a load resolution of 0.01N with a stability of plus/minus 0.1N, and a displacement resolution of 0.05 microns with a stability of plus/minus 0.1 microns. Samples of eutectic Sn-Ag solder were reflowed to develop the microstructure used in microelectronic packaging. Creep tests were conducted at various stresses and temperatures and showed that coarse microstructures creep more rapidly than the microstructures in the tested regime.

  11. Transected sciatic nerve repair by diode laser protein soldering.

    Science.gov (United States)

    Fekrazad, Reza; Mortezai, Omid; Pedram, MirSepehr; Kalhori, Katayoun Am; Joharchi, Khojasteh; Mansoori, Korosh; Ebrahimi, Roja; Mashhadiabbas, Fatemeh

    2017-08-01

    Despite advances in microsurgical techniques, repair of peripheral nerve injuries (PNI) is still a major challenge in regenerative medicine. The standard treatment for PNI includes suturing and anasthomosis of the transected nerve. The objective of this study was to compare neurorraphy (nerve repair) using standard suturingto diode laser protein soldering on the functional recovery of transected sciatic nerves. Thirty adult male Fischer-344 Wistar rats were randomly assigned to 3 groups: 1. The control group, no repair, 2. the standard of care suture group, and 3. The laser/protein solder group. For all three groups, the sciatic nerve was transected and the repair was done immediately. For the suture repair group, 10.0 prolene suture was used and for the laser/protein solder group a diode laser (500mW output power) in combination with bovine serum albumen and indocyanine green dye was used. Behavioral assessment by sciatic functional index was done on all rats biweekly. At 12weeks post-surgery, EMG recordings were done on all the rats and the rats were euthanized for histological evaluation of the sciatic nerves. The one-way ANOVA test was used for statistical analysis. The average time required to perform the surgery was significantly shorter for the laser-assisted nerve repair group compared to the suture group. The EMG evaluation revealed no difference between the two groups. Based on the sciatic function index the laser group was significantly better than the suture group after 12weeks (pneurorraphy using standard suturing methods. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Vibration characteristics of an inclined flip-flow screen panel in banana flip-flow screens

    Science.gov (United States)

    Xiong, Xiaoyan; Niu, Linkai; Gu, Chengxiang; Wang, Yinhua

    2017-12-01

    A banana flip-flow screen is an effective solution for the screening of high-viscosity, high-water and fine materials. As one of the key components, the vibration characteristics of the inclined flip-flow screen panel largely affects the screen performance and the processing capacity. In this paper, a mathematical model for the vibration characteristic of the inclined flip-flow screen panel is proposed based on Catenary theory. The reasonability of Catenary theory in analyzing the vibration characteristic of flip-flow screen panels is verified by a published experiment. Moreover, the effects of the rotation speed of exciters, the incline angle, the slack length and the characteristics of the screen on the vertical deflection, the vertical velocity and the vertical acceleration of the screen panel are investigated parametrically. The results show that the rotation speed of exciters, the incline angle, the slack length and the characteristics of the screen have significant effects on the vibrations of an inclined flip-flow screen panel, and these parameters should be optimized.

  13. Reliability of Wind Turbine Components-Solder Elements Fatigue Failure

    DEFF Research Database (Denmark)

    Kostandyan, Erik; Sørensen, John Dalsgaard

    2012-01-01

    on the temperature mean and temperature range. Constant terms and model errors are estimated. The proposed methods are useful to predict damage values for solder joint in power electrical components. Based on the proposed methods it is described how to find the damage level for a given temperature loading profile....... The proposed methods are discussed for application in reliability assessment of Wind Turbine’s electrical components considering physical, model and measurement uncertainties. For further research it is proposed to evaluate damage criteria for electrical components due to the operational temperature...

  14. Pressure brazing of ceramics to metals with copper solder

    International Nuclear Information System (INIS)

    Pavlova, M.A.; Metelkin, I.I.

    1986-01-01

    The effect on the quality of joints brazed with copper of different non metallized aluminooxide dielectrics with metals and alloys of a series of technological parameters (temperature, pressure, holding, and medium) in the course of pressure brazing is investigated. It is shown that in case of brazing with kovar and nickel the character of dependences is identical, however in all cases the joints with nickel are more durable. For the ceramics - molybdenum system characterized by weak interaction with copper solder kinetic dependences have no maximum and only under holding of more than 20 min the constant strength of 150-190 MPa is attained

  15. Variable-flip-angle spin-echo imaging (VFSE)

    International Nuclear Information System (INIS)

    Kasai, Toshifumi; Sugimura, Kazuro; Kawamitsu, Hideaki; Yasui, Kiyoshi; Ishida, Tetsuya; Tsukamoto, Tetsuji.

    1990-01-01

    T 2 weighted imaging provides images with high object contrast for pathologic conditions in which the water content of tissues is increased. The authors predicted theoretical analysis of the effects of changing flip angle, and analyzed the effects in MR imaging of both phantoms and humans. Variable flip angle spin echo MR imaging (VFSE) with a 1,000/80 (repetition time msec/echo time msec) can obtain T 2 weighted image when flip angle is smaller than 80 degrees. VFSE with 40 to 60 degrees flip angle have higher contrast than other flip angle images. Signal to noise ratio (S/N) of VFSE are 55% at a 30 degree, 76% at a 45 degree, 92% at a 60 degree respectively as compared with conventional spin echo image (2000/80, flip angle 90 degree). VFSE is applicable to obtain T 2 weighted image reduced imaging time. (author)

  16. Flipped Learning With Simulation in Undergraduate Nursing Education.

    Science.gov (United States)

    Kim, HeaRan; Jang, YounKyoung

    2017-06-01

    Flipped learning has proliferated in various educational environments. This study aimed to verify the effects of flipped learning on the academic achievement, teamwork skills, and satisfaction levels of undergraduate nursing students. For the flipped learning group, simulation-based education via the flipped learning method was provided, whereas traditional, simulation-based education was provided for the control group. After completion of the program, academic achievement, teamwork skills, and satisfaction levels were assessed and analyzed. The flipped learning group received higher scores on academic achievement, teamwork skills, and satisfaction levels than the control group, including the areas of content knowledge and clinical nursing practice competency. In addition, this difference gradually increased between the two groups throughout the trial. The results of this study demonstrated the positive, statistically significant effects of the flipped learning method on simulation-based nursing education. [J Nurs Educ. 2017;56(6):329-336.]. Copyright 2017, SLACK Incorporated.

  17. The Flipped Learning Approach in Nursing Education: A Literature Review.

    Science.gov (United States)

    Presti, Carmen Rosa

    2016-05-01

    This integrative review examines the application of the pedagogical methodology-the flipped classroom-in nursing education. A literature search of the CINAHL, ERIC, and the National Library of Medicine (PubMed and MEDLINE) databases was conducted, using the following key words: flipped classroom, inverted classroom, and nursing education. Results of a literature search yielded 94 articles, with 13 meeting the criteria of the flipped classroom approach in nursing education. Themes identified include the theoretical underpinning, strategies for implementation of a flipped classroom, and student satisfaction with and outcomes of the flipped classroom approach. Syntheses of the findings indicate that the flipped classroom approach can yield positive outcomes, but further study of this methodology is needed to guide future implementation. [J Nurs Educ. 2016;55(5):252-257.]. Copyright 2016, SLACK Incorporated.

  18. Report on damaged FLIP TRIGA fuel

    International Nuclear Information System (INIS)

    Feltz, Donald E.; Randall, John D.; Schumacher, Robert F.

    1977-01-01

    Damaged FLIP elements were discovered, positioned adjacent to the transient rod. It then became apparent that this was not the failure of a defective, element but a heretofore unknown operating or design problem. The damaged elements are described as having bulges in the cladding and unevenly spaced dark rings along the fuelled portion of the element. Possible causes are investigated, including: defective fuel elements, incorrectly calculated power distributions in the core and in the elements, water leakage into the void follower of the transient rod, and improper safety limit for FLIP fuel. Based on measurements and calculations that have been experimentally verified it is concluded that the safety limit was not exceeded or even closely approached. It is also concluded that the problem is due entirely due to some phenomena occurring during pulsing, and that the steady state history of the fuel is not a factor

  19. Flip-flops of FK Comae Berenices

    DEFF Research Database (Denmark)

    Hackman, T.; Pelt, J.; Mantere, M. J.

    2013-01-01

    Context.FK Comae Berenices is a rapidly rotating magnetically active star, the light curve of which is modulated by cool spots on its surface. It was the first star where the "flip-flop" phenomenon was discovered. Since then, flip-flops in the spot activity have been reported in many other stars....... Follow-up studies with increasing length have shown, however, that the phenomenon is more complex than was thought right after its discovery. Aims. Therefore, it is of interest to perform a more thorough study of the evolution of the spot activity in FK Com. In this study, we analyse 15 years......-flop cannot be interpreted as a single phenomenon, where the main activity jumps from one active longitude to another. In some of our cases the phase shifts can be explained by differential rotation: two spot regions move with different angular velocity and even pass each other. Comparison between the methods...

  20. Scariest thing about climate change: climate flips

    International Nuclear Information System (INIS)

    Beaulieu, P.

    1997-01-01

    The idea that an increase in greenhouse gases will cause the global average temperature to rise slowly over the next decades was discussed. Studies of ice core from Greenland have shown that in the past climate shifts seem to have happened quickly. Some scientists fear that increasingly frequent extreme weather events could be a sign that the climate system is nearing its threshold and a rapid climate flip may be just ahead. In the case of global climatic system, the danger is that stresses from greenhouse gas effects are pushing the present system over the threshold where it must flip into a new warmer system that will be stable, but different from the climate on which our agriculture, economy, settlements and lives depend. 4 refs

  1. Flipped learning: should it replace didactic learning?

    Directory of Open Access Journals (Sweden)

    Osman A

    2017-10-01

    Full Text Available Abdirahman Osman, Seyed Ramin Jalal, Saeed Azizi Faculty of Medicine, St George’s Hospital Medical School, London, UKWe read with great interest the article by Pettit et al1 on the implementation of flipped learning. We wish to offer our perspective as medical students. The study concluded that a combination of lecture-based teaching accompanied with flipped learning activities appealed to most students. We find this response unsurprising. Pettit et al’s1 article documents the reason – the need for a variation in teaching styles for different themes by millennial learners of the modern student community.View the original paper by Pettit and colleagues.  

  2. Flipped neutrino emissivity from strange matter

    International Nuclear Information System (INIS)

    Goyal, A.; Dutta, S.

    1994-01-01

    Energy loss due to wrong helicity sterile neutrinos through spin flip processes leads to rapid cooling of nascent neutron stars. The observed cooling of neutron stars associated with SN 1987A seems to preclude the existence of Dirac neutrinos with a mass in excess of 20 keV. Assuming that nuclear matter in the core of the neutron star undergoes a phase transition to quark matter leading to a strange star or a neutron star with a strange matter core, we examine the emission of flipped Dirac neutrinos for two dominant processes: quark-neutrino scattering [q+ν - (bar ν + )→q+ν + (bar ν - )] and the quark neutrino pair bremsstrahlung process [q+q→q+q+ν - bar ν - (ν+bar ν + )]. We determine the composition of quark matter just after core bounce and examine the effect of neutrino degeneracy on the emission rate and mean free path of the wrong helicity neutrinos

  3. Student Perceptions of a Flipped Pharmacotherapy Course

    Science.gov (United States)

    Khanova, Julia; McLaughlin, Jacqueline E.; Rhoney, Denise H.; Roth, Mary T.

    2015-01-01

    Objective. To evaluate student perception of the flipped classroom redesign of a required pharmacotherapy course. Design. Key foundational content was packaged into interactive, text-based online modules for self-paced learning prior to class. Class time was used for active and applied—but primarily case-based—learning. Assessment. For students with a strong preference for traditional lecture learning, the perception of the learning experience was negatively affected by the flipped course design. Module length and time required to complete preclass preparation were the most frequently cited impediments to learning. Students desired instructor-directed reinforcement of independently acquired knowledge to connect foundational knowledge and its application. Conclusion. This study illustrates the challenges and highlights the importance of designing courses to effectively balance time requirements and connect preclass and in-class learning activities. It underscores the crucial role of the instructor in bridging the gap between material learned as independent study and its application. PMID:26839429

  4. Flipped-Adversarial AutoEncoders

    OpenAIRE

    Zhang, Jiyi; Dang, Hung; Lee, Hwee Kuan; Chang, Ee-Chien

    2018-01-01

    We propose a flipped-Adversarial AutoEncoder (FAAE) that simultaneously trains a generative model G that maps an arbitrary latent code distribution to a data distribution and an encoder E that embodies an "inverse mapping" that encodes a data sample into a latent code vector. Unlike previous hybrid approaches that leverage adversarial training criterion in constructing autoencoders, FAAE minimizes re-encoding errors in the latent space and exploits adversarial criterion in the data space. Exp...

  5. The flipped classroom for medical students.

    Science.gov (United States)

    Morgan, Helen; McLean, Karen; Chapman, Chris; Fitzgerald, James; Yousuf, Aisha; Hammoud, Maya

    2015-06-01

    The objectives of this curricular innovation project were to implement a flipped classroom curriculum for the gynaecologic oncology topics of the obstetrics and gynaecology medical student clerkship, and to evaluate student satisfaction with the change. Four short online videos on the topics of endometrial hyperplasia, cervical dysplasia, evaluation of an adnexal mass, and ovarian cancer were created, and students were instructed to view them prior to a class-time active learning session. The Learning Activity Management System (lams) open-source online platform was used to create an active learning class-time activity that consisted of a coached discussion of cases. Student satisfaction with the two aspects of the flipped curriculum was obtained. In addition, lecture assessment for the gynaecologic oncology topics and aggregate student performance on the gynaecological oncology questions of the US National Board of Medical Examiners (NBME) Subject Examination were compared before and after implementation of the curriculum. Eighty-nine students rotated on the clerkship during the pilot period of analysis. Seventy-one students (80%) viewed the videos prior to the class session, and 84 (94%) attended the session. Student satisfaction was very high for both parts of the curriculum. There was no significant difference in aggregate student performance on the gynaecological oncology questions of the NBME Subject Examination. The flipped classroom curriculum demonstrates a promising platform for using technology to make better use of students' time Our implementation of the flipped classroom curriculum for the gynaecologic oncology topics successfully demonstrates a promising platform for using technology to make better use of our students' time, and for increasing their satisfaction with the necessary didactic learning of the clerkship. © 2015 John Wiley & Sons Ltd.

  6. The Implementation of A Flipped Classroom in Foreign Language Teaching

    OpenAIRE

    Ahmet BASAL

    2015-01-01

    Alongside the rise of educational technology, many teachers have been taking gradual but innovative steps to redesign their teaching methods. For example, in flipped learning or a flipped classroom, students watch instructional videos outside the classroom and do assignments or engage in activities inside the classroom. Language teachers are one group of educators exploring the flipped classroom. In foreign language classes, such an approach may offer great benefits for both the teachers and ...

  7. Flipped Classroom as an Alternative Strategy for Teaching Stoichiometry

    OpenAIRE

    Norrie E. Gayeta

    2017-01-01

    This study aimed to compare the effectiveness of flipped classroom and traditional classroom instruction in measuring conceptual change and to determine if flipped classroom instruction would be an alternative method of teaching to traditional lecture method. This study covered the level of conceptual understanding of students on stoichiometry and the type of conceptual change before and after exposure to flipped and traditional classroom environment. Qualitative and quantitative ...

  8. Assessment of learning gains in a flipped biochemistry classroom.

    Science.gov (United States)

    Ojennus, Deanna Dahlke

    2016-01-01

    The flipped classroom has become an increasingly popular pedagogical approach to teaching and learning. In this study, learning gains were assessed in a flipped biochemistry course and compared to gains in a traditional lecture. Although measured learning gains were not significantly different between the two courses, student perception of learning gains did differ and indicates a higher level of satisfaction with the flipped lecture format. © 2015 The International Union of Biochemistry and Molecular Biology.

  9. Nonlinear stability of spin-flip excitations

    International Nuclear Information System (INIS)

    Arunasalam, V.

    1975-01-01

    A rather complete discussion of the nonlinear electrodynamic behavior of a negative-temperature spin system is presented. The method presented here is based on a coupled set of master equations, one describing the time evolution of the photon (i.e., the spin-flip excitation) distribution function and the other describing the time evolution of the particle distribution function. It is found that the initially unstable (i.e., growing) spin-flip excitations grow to such a large amplitude that their nonlinear reaction on the particle distribution function becomes important. It is then shown that the initially totally inverted two-level spin system evolves rapidly (through this nonlinear photon-particle coupling) towards a quasilinear steady state where the populations of the spin-up and the spin-down states are equal to each other. Explicit expressions for the time taken to reach this quasilinear steady state and the energy in the spin-flip excitations at this state are also presented

  10. Mapping of low flip angles in magnetic resonance

    International Nuclear Information System (INIS)

    Balezeau, Fabien; Saint-Jalmes, Herve; Eliat, Pierre-Antoine; Cayamo, Alejandro Bordelois

    2011-01-01

    Errors in the flip angle have to be corrected in many magnetic resonance imaging applications, especially for T1 quantification. However, the existing methods of B1 mapping fail to measure lower values of the flip angle despite the fact that these are extensively used in dynamic acquisition and 3D imaging. In this study, the nonlinearity of the radiofrequency (RF) transmit chain, especially for very low flip angles, is investigated and a simple method is proposed to accurately determine both the gain of the RF transmitter and the B1 field map for low flip angles. The method makes use of the spoiled gradient echo sequence with long repetition time (TR), such as applied in the double-angle method. It uses an image acquired with a flip angle of 90 0 as a reference image that is robust to B1 inhomogeneity. The ratio of the image at flip angle alpha to the image at a flip angle of 90 0 enables us to calculate the actual value of alpha. This study was carried out at 1.5 and 4.7 T, showing that the linearity of the RF supply system is highly dependent on the hardware. The method proposed here allows us to measure the flip angle from 1 0 to 60 0 with a maximal uncertainty of 10% and to correct T1 maps based on the variable flip angle method.

  11. Retention of Content Utilizing a Flipped Classroom Approach.

    Science.gov (United States)

    Shatto, Bobbi; LʼEcuyer, Kristine; Quinn, Jerod

    The flipped classroom experience promotes retention and accountability for learning. The authors report their evaluation of a flipped classroom for accelerated second-degree nursing students during their primary medical-surgical nursing course. Standardized HESI® scores were compared between a group of students who experienced the flipped classroom and a previous group who had traditional teaching methods. Short- and long-term retention was measured using standardized exams 3 months and 12 months following the course. Results indicated that short-term retention was greater and long- term retention was significantly great in the students who were taught using flipped classroom methodology.

  12. The flipped classroom: practices and opportunities for health sciences librarians.

    Science.gov (United States)

    Youngkin, C Andrew

    2014-01-01

    The "flipped classroom" instructional model is being introduced into medical and health sciences curricula to provide greater efficiency in curriculum delivery and produce greater opportunity for in-depth class discussion and problem solving among participants. As educators employ the flipped classroom to invert curriculum delivery and enhance learning, health sciences librarians are also starting to explore the flipped classroom model for library instruction. This article discusses how academic and health sciences librarians are using the flipped classroom and suggests opportunities for this model to be further explored for library services.

  13. Albumin solder covalently bound to a polymer membrane: New approach to improve binding strength in laser tissue soldering in-vitro.

    Science.gov (United States)

    Hiebl, B; Ascher, L; Luetzow, K; Kratz, K; Gruber, C; Mrowietz, C; Nehring, M E; Lendlein, A; Franke, R-P; Jung, F

    2018-01-01

    Laser tissue soldering (LTS) based on indocyanine green (ICG)-mediated heat-denaturation of proteins might be a promising alternative technique for micro-suturing, but up to now the problem of too weak shear strength of the solder welds in comparison to sutures is not solved. Earlier reports gave promising results showing that solder supported by carrier materials can enhance the cohesive strength of the liquid solder. In these studies, the solder was applied to the carriers by dip coating. Higher reliability of the connection between the solder and the carrier material is expected when the solder is bound covalently to the carrier material. In the present study a poly(ether imide) (PEI) membrane served as carrier material and ICG-supplemented albumin as solder substrate. The latter was covalently coupled to the carrier membrane under physiological conditions to prevent structural protein changes. As laser source a diode continuous-wave laser emitting at 808 nm with intensities between 250 mW and 1500 mW was utilized. The albumin functionalized carrier membrane was placed onto the tunica media of explanted pig thoracic aortae forming an overlapping area of approximately 0.5×0.5 cm2. All tests were performed in a dry state to prevent laser light absorption by water. Infrared spectroscopy, spectro-photometrical determination of the secondary and primary amine groups after acid orange II staining, contact angle measurements, and atomic force microscopy proved the successful functionalization of the PEI membrane with albumin. A laser power of 450 mW LTS could generate a membrane-blood vessel connection which was characterized by a shear strength of 0.08±0.002 MPa, corresponding to 15% of the tensile strength of the native blood vessel. Theoretically, an overlapping zone of 4.1 mm around the entire circumference of the blood vessel could have provided shear strength of the PEI membrane-blood vessel compound identical to the tensile strength of the native

  14. Development of Pb-Free Nanocomposite Solder Alloys

    Directory of Open Access Journals (Sweden)

    Animesh K. Basak

    2018-04-01

    Full Text Available As an alternative to conventional Pb-containing solder material, Sn–Ag–Cu (SAC based alloys are at the forefront despite limitations associated with relatively poor strength and coarsening of grains/intermetallic compounds (IMCs during aging/reflow. Accordingly, this study examines the improvement of properties of SAC alloys by incorporating nanoparticles in it. Two different types of nanoparticles were added in monolithic SAC alloy: (1 Al2O3 or (2 Fe and their effect on microstructure and thermal properties were investigated. Addition of Fe nanoparticles leads to the formation of FeSn2 IMCs alongside Ag3Sn and Cu6Sn5 from monolithic SAC alloy. Addition of Al2O3 nano-particles do not contribute to phase formation, however, remains dispersed along primary β-Sn grain boundaries and act as a grain refiner. As the addition of either Fe or Al2O3 nano-particles do not make any significant effect on thermal behavior, these reinforced nanocomposites are foreseen to provide better mechanical characteristics with respect to conventional monolithic SAC solder alloys.

  15. Impurity Effects in Electroplated-Copper Solder Joints

    Directory of Open Access Journals (Sweden)

    Hsuan Lee

    2018-05-01

    Full Text Available Copper (Cu electroplating is a mature technology, and has been extensively applied in microelectronic industry. With the development of advanced microelectronic packaging, Cu electroplating encounters new challenges for atomic deposition on a non-planar substrate and to deliver good throwing power and uniform deposit properties in a high-aspect-ratio trench. The use of organic additives plays an important role in modulating the atomic deposition to achieve successful metallic coverage and filling, which strongly relies on the adsorptive and chemical interactions among additives on the surface of growing film. However, the adsorptive characteristic of organic additives inevitably results in an incorporation of additive-derived impurities in the electroplated Cu film. The incorporation of high-level impurities originating from the use of polyethylene glycol (PEG and chlorine ions significantly affects the microstructural evolution of the electroplated Cu film, and the electroplated-Cu solder joints, leading to the formation of undesired voids at the joint interface. However, the addition of bis(3-sulfopropyl disulfide (SPS with a critical concentration suppresses the impurity incorporation and the void formation. In this article, relevant studies were reviewed, and the focus was placed on the effects of additive formula and plating parameters on the impurity incorporation in the electroplated Cu film, and the void formation in the solder joints.

  16. Temperature-controlled laser-soldering system and its clinical application for bonding skin incisions

    Science.gov (United States)

    Simhon, David; Gabay, Ilan; Shpolyansky, Gregory; Vasilyev, Tamar; Nur, Israel; Meidler, Roberto; Hatoum, Ossama Abu; Katzir, Abraham; Hashmonai, Moshe; Kopelman, Doron

    2015-12-01

    Laser tissue soldering is a method of repairing incisions. It involves the application of a biological solder to the approximated edges of the incision and heating it with a laser beam. A pilot clinical study was carried out on 10 patients who underwent laparoscopic cholecystectomy. Of the four abdominal incisions in each patient, two were sutured and two were laser soldered. Cicatrization, esthetical appearance, degree of pain, and pruritus in the incisions were examined on postoperative days 1, 7, and 30. The soldered wounds were watertight and healed well, with no discharge from these wounds or infection. The total closure time was equal in both methods, but the net soldering time was much shorter than suturing. There was no difference between the two types of wound closure with respect to the pain and pruritus on a follow-up of one month. Esthetically, the soldered incisions were estimated as good as the sutured ones. The present study confirmed that temperature-controlled laser soldering of human skin incisions is clinically feasible, and the results obtained were at least equivalent to those of standard suturing.

  17. Laser-tissue soldering with biodegradable polymer films in vitro: film surface morphology and hydration effects.

    Science.gov (United States)

    Sorg, B S; Welch, A J

    2001-01-01

    Previous research introduced the concept of using biodegradable polymer film reinforcement of a liquid albumin solder for improvement of the tensile strength of repaired incisions in vitro. In this study, the effect of creating small pores in the PLGA films on the weld breaking strength is studied. Additionally, the effect of hydration on the strength of the reinforced welds is investigated. A 50%(w/v) bovine serum albumin solder with 0.5 mg/mL Indocyanine Green dye was used to repair an incision in bovine aorta. The solder was coagulated with an 806-nm CW diode laser. A poly(DL-lactic-co-glycolic acid) (PLGA) film was used to reinforce the solder (the controls had solder but no reinforcement). Breaking strengths were measured acutely and after hydration in saline for 1 and 2 days. The data were analyzed by ANOVA (P < 0.05) and multiple comparisons of means were performed using the Newman-Keuls test. The creation of pores in the PLGA films qualitatively improved the film flexibility without having an apparent adverse effect on the breaking strength, while the actual technique of applying the film and solder had more of an effect. The acute maximum average breaking strengths of some of the film reinforced specimens (114.7 g-134.4 g) were significantly higher (P < 0.05) than the acute maximum average breaking strength of the unreinforced control specimens (68.3 g). Film reinforced specimens were shown to have a statistically significantly higher breaking strength than unreinforced controls after 1- and 2-day hydration. Reinforcement of liquid albumin solders in laser-assisted incision repair appears to have advantages over conventional methods that do not reinforce the cohesive strength of the solder in terms of acute breaking strength and after immersion in moist environments for short periods of time. Using a film with the solder applied to one surface only may be advantageous over other techniques.

  18. UW VLSI chip tester

    Science.gov (United States)

    McKenzie, Neil

    1989-12-01

    We present a design for a low-cost, functional VLSI chip tester. It is based on the Apple MacIntosh II personal computer. It tests chips that have up to 128 pins. All pin drivers of the tester are bidirectional; each pin is programmed independently as an input or an output. The tester can test both static and dynamic chips. Rudimentary speed testing is provided. Chips are tested by executing C programs written by the user. A software library is provided for program development. Tests run under both the Mac Operating System and A/UX. The design is implemented using Xilinx Logic Cell Arrays. Price/performance tradeoffs are discussed.

  19. The influence of silver content on structure and properties of Sn–Bi–Ag solder and Cu/solder/Cu joints

    Energy Technology Data Exchange (ETDEWEB)

    Šebo, P. [Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Račianska 75, 831 02 Bratislava 3 (Slovakia); Švec, P. Sr., E-mail: Peter.Svec@savba.sk [Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 845 11 Bratislava 45 (Slovakia); Faculty of Materials Science and Technology, Slovak University of Technology, J. Bottu 25, 917 24 Trnava (Slovakia); Janičkovič, D.; Illeková, E. [Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 845 11 Bratislava 45 (Slovakia); Zemánková, M. [Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Račianska 75, 831 02 Bratislava 3 (Slovakia); Plevachuk, Yu. [Ivan Franko National University, Department of Metal Physics, 79005 Lviv (Ukraine); Sidorov, V. [Ural State Pedagogical University, Cosmonavtov 26, 620017 Ekaterinburg (Russian Federation); Švec, P. [Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 845 11 Bratislava 45 (Slovakia)

    2013-06-01

    The effect of silver content on structure and properties of Sn{sub 100−x}Bi{sub 10}Ag{sub x} (x=3–10 at%) lead-free solder and Cu–solder–Cu joints was investigated. The microstructure of the solder in both bulk and rapidly solidified ribbon forms was analyzed by scanning electron microscopy (SEM) and X-ray diffraction. The peculiarities in melting kinetic, studied by differential scanning calorimetry (DSC), and silver influence on it are described and discussed. The wetting of a copper substrate was examined by the sessile drop method in the temperature range of 553–673 K in air and deoxidizing gas (N{sub 2}+10%H{sub 2}) at atmospheric pressure. Cu–solder–Cu joints were also prepared in both atmospheres, and their shear strength was measured by the push-off method. The produced solders consisted of tin, bismuth and Ag{sub 3}Sn phases. The product of the interaction between the solder and the copper substrate consists of two phases: Cu{sub 3}Sn, which is adjacent to the substrate, and a Cu{sub 6}Sn{sub 5} phase. The wetting angle in air increased slightly as the silver concentration in the solder increased. Wetting of the copper substrate in N{sub 2}+10H{sub 2} gas shows the opposite tendency: the wetting angle slightly decreased as the silver content in the solder increased. The shear strength of the joints prepared in air (using flux) tends to decrease with increasing production temperature and increasing silver content in the solder. The equivalent decrease in the shear strength of the joints prepared in N{sub 2}+10H{sub 2} is more apparent.

  20. Contamination profile on typical printed circuit board assemblies vs soldering process

    DEFF Research Database (Denmark)

    Conseil, Helene; Jellesen, Morten Stendahl; Ambat, Rajan

    2014-01-01

    Purpose – The purpose of this paper was to analyse typical printed circuit board assemblies (PCBAs) processed by reflow, wave or selective wave soldering for typical levels of process-related residues, resulting from a specific or combination of soldering processes. Typical solder flux residue...... structure was identified by Fourier transform infrared spectroscopy, while the concentration was measured using ion chromatography, and the electrical properties of the extracts were determined by measuring the leak current using a twin platinum electrode set-up. Localized extraction of residue was carried...

  1. Contamination profile of Printed Circuit Board Assemblies in relation to soldering types and conformal coating

    DEFF Research Database (Denmark)

    Conseil, Helene; Jellesen, Morten Stendahl; Ambat, Rajan

    2014-01-01

    Typical printed circuit board assemblies (PCBAs) processed by reflow, wave, or selective wave soldering were analysed for typical levels of process related residues, resulting from a specific or combination of soldering process. Typical solder flux residue distribution pattern, composition......, and concentration are profiled and reported. Presence of localized flux residues were visualized using a commercial Residue RAT gel test and chemical structure was identified by FT-IR, while the concentration was measured using ion chromatography, and the electrical properties of the extracts were determined...

  2. Modeling of high temperature- and diffusion-controlled die soldering in aluminum high pressure die casting

    DEFF Research Database (Denmark)

    Domkin, Konstantin; Hattel, Jesper Henri; Thorborg, Jesper

    2009-01-01

    of the die lifetime based on a quantitative analysis of die soldering in the framework of the numerical simulations of the die-casting process. Full 3D simulations of the process, including the filling. solidification, and the die cooling, are carried out using the casting simulation software MAGMAsoft....... The resulting transient temperature fields on the die surface and in the casting are then post-processed to estimate the die soldering. The present work deals only with the metallurgical/chemical kind of soldering which occurs at high temperatures and involves formation and growth of intermetallic layers...

  3. Eddy current quality control of soldered current-carrying busbar splices of superconducting magnets

    CERN Document Server

    Kogan, L; Savary, F; Principe, R; Datskov, V; Rozenfel'd, E; Khudjakov, B

    2015-01-01

    The eddy current technique associated with a U-shaped transducer is studied for the quality control of soldered joints between superconducting busbars ('splices'). Two other quality control techniques, based on X-rays and direct measurement of the electrical resistance, are also studied for comparison. A comparative analysis of the advantages and disadvantages of these three methods in relation to the quality control of soldered superconducting busbar cables enclosed in copper shells is used for benchmarking. The results of inspections with the U-shaped eddy current transducer carried out on several sample joints presenting different types of soldering defects show the potential of this type of nondestructive (ND) quality control technique.

  4. ConfChem Conference on Flipped Classroom: Using a Blog to Flip a Classroom

    Science.gov (United States)

    Haile, January D.

    2015-01-01

    This communication summarizes one of the invited papers to the Flipped Classroom ACS Division of Chemical Education Committee on Computers in Chemical Education online ConfChem held from May 18 to June 24, 2014. Just in Time Teaching is a technique in which students read the material before class and respond to a few questions. In a first-year…

  5. Flipping Every Student? A Case Study of Content-Based Flipped Language Classrooms

    Science.gov (United States)

    Sun, Yu-Chih

    2017-01-01

    The study aims to explore university-level foreign language learners' perceptions of the content-based flipped classroom approach and factors influencing their perceptions. The research questions guiding the study are three-fold. (a) What attitudes and perceptions do students have about language and knowledge acquisition in the content-based…

  6. Using the Flipped Classroom to Enhance EFL Learning

    Science.gov (United States)

    Chen Hsieh, Jun Scott; Wu, Wen-Chi Vivian; Marek, Michael W.

    2017-01-01

    Instruction in English is a priority around the globe, but instructional methodologies have not always kept pace with the changing needs of students. To explore the benefits of the flipped classroom model for learners of English as a Foreign Language, the researchers used flipped learning and Wen's Output-driven/Input-enabled model to design a…

  7. Case Study: Guidelines for Producing Videos to Accompany Flipped Cases

    Science.gov (United States)

    Prud'homme-Généreux, Annie; Schiller, Nancy A.; Wild, John H.; Herreid, Clyde Freeman

    2017-01-01

    Three years ago, the "National Center for Case Study Teaching in Science" (NCCSTS) was inspired to merge the case study and flipped classroom approaches. The resulting project aimed to create the materials required to teach a flipped course in introductory biology by assigning videos as homework and case studies in the classroom. Three…

  8. Flipped Learning in TESOL: Definitions, Approaches, and Implementation

    Science.gov (United States)

    Bauer-Ramazani, Christine; Graney, John M.; Marshall, Helaine W.; Sabieh, Christine

    2016-01-01

    As the use of flipped learning spreads throughout educational disciplines, TESOL educators need to consider its potential for our field. This article, based on a computer-aided language learning (CALL) interest session at TESOL 2015, first looks at how best to describe and define flipped learning and examines the factors needed to make it…

  9. An Inquiry into Flipped Learning in Fourth Grade Math Instruction

    Science.gov (United States)

    D'addato, Teresa; Miller, Libbi R.

    2016-01-01

    The objective of this action research project was to better understand the impact of flipped learning on fourth grade math students in a socioeconomically disadvantaged setting. A flipped instructional model was implemented with the group of students enrolled in the researcher's class. Data was collected in the form of classroom observations,…

  10. Flipped SU(5) times U(1) in superconformal models

    Energy Technology Data Exchange (ETDEWEB)

    Bailin, D.; Katechou, E.K. (Sussex Univ., Brighton (United Kingdom). School of Mathematical and Physical Sciences); Love, A. (London Univ. (United Kingdom))

    1992-01-10

    This paper reports that flipped SU(5) {times} U(1) models are constructed in the framework of tensoring of N = 2 superconformal minimal models quotiented by discrete symmetries. Spontaneous breaking of flipped SU(5) {times} U(1) and extra U(1) factors in the gauge group along F-flat directions of the effective potential is studied.

  11. Partially Flipped Linear Algebra: A Team-Based Approach

    Science.gov (United States)

    Carney, Debra; Ormes, Nicholas; Swanson, Rebecca

    2015-01-01

    In this article we describe a partially flipped Introductory Linear Algebra course developed by three faculty members at two different universities. We give motivation for our partially flipped design and describe our implementation in detail. Two main features of our course design are team-developed preview videos and related in-class activities.…

  12. Examining Student Perceptions of Flipping an Agricultural Teaching Methods Course

    Science.gov (United States)

    Conner, Nathan W.; Rubenstein, Eric D.; DiBenedetto, Cathy A.; Stripling, Christopher T.; Roberts, T. Grady; Stedman, Nicole L. P.

    2014-01-01

    To meet the needs of the 21st century student, college instructors have been challenged to transform their classrooms from passive to active, "minds-on" learning environments. This qualitative study examined an active learning approach known as a flipped classroom and sought to explore student perceptions of flipping a teaching methods…

  13. Evaluation of a "Flipped Classroom" Approach in Management Education

    Science.gov (United States)

    Bergfjord, Ole Jakob; Heggernes, Tarjei

    2016-01-01

    In this paper, a "flipped classroom" approach is evaluated using three different datasets. We use student evaluations of the "flipped classroom" in particular, in addition to regular course evaluations and exam results for the past three years in order to allow for statistical comparisons. Overall, the results are quite…

  14. The Flipped Class: Experience in a University Business Communication Course

    Science.gov (United States)

    Sherrow, Tammy; Lang, Brenda; Corbett, Rod

    2016-01-01

    Business, like many other programs in higher education, continues to rely largely on traditional classroom environments. In this article, another approach to teaching and learning, the flipped classroom, is explored. After a review of relevant literature, the authors present their experience with the flipped classroom approach to teaching and…

  15. Assisted crack tip flipping under Mode I thin sheet tearing

    DEFF Research Database (Denmark)

    Felter, Christian Lotz; Nielsen, Kim Lau

    2017-01-01

    Crack tip flipping, where the fracture surface alternates from side to side in roughly 45° shear bands, seems to be an overlooked propagation mode in Mode I thin sheet tearing. In fact, observations of crack tip flipping is rarely found in the literature. Unlike the already established modes...

  16. Assessment of Learning Gains in a Flipped Biochemistry Classroom

    Science.gov (United States)

    Ojennus, Deanna Dahlke

    2016-01-01

    The flipped classroom has become an increasingly popular pedagogical approach to teaching and learning. In this study, learning gains were assessed in a flipped biochemistry course and compared to gains in a traditional lecture. Although measured learning gains were not significantly different between the two courses, student perception of…

  17. On Flipping First-Semester Calculus: A Case Study

    Science.gov (United States)

    Petrillo, Joseph

    2016-01-01

    High failure rates in calculus have plagued students, teachers, and administrators for decades, while science, technology, engineering, and mathematics programmes continue to suffer from low enrollments and high attrition. In an effort to affect this reality, some educators are "flipping" (or inverting) their classrooms. By flipping, we…

  18. Flipping College Algebra: Effects on Student Engagement and Achievement

    Science.gov (United States)

    Ichinose, Cherie; Clinkenbeard, Jennifer

    2016-01-01

    This study compared student engagement and achievement levels between students enrolled in a traditional college algebra lecture course and students enrolled in a "flipped" course. Results showed that students in the flipped class had consistently higher levels of achievement throughout the course than did students in the traditional…

  19. Assessing the Flipped Classroom in Operations Management: A Pilot Study

    Science.gov (United States)

    Prashar, Anupama

    2015-01-01

    The author delved into the results of a flipped classroom pilot conducted for an operations management course module. It assessed students' perception of a flipped learning environment after making them experience it in real time. The classroom environment was construed using a case research approach and students' perceptions were studied using…

  20. Flipping the Calculus Classroom: A Cost-Effective Approach

    Science.gov (United States)

    Young, Andrea

    2015-01-01

    This article discusses a cost-effective approach to flipping the calculus classroom. In particular, the emphasis is on low-cost choices, both monetarily and with regards to faculty time, that make the daunting task of flipping a course manageable for a single instructor. Student feedback and overall impressions are also presented.

  1. Flipped @ SBU: Student Satisfaction and the College Classroom

    Science.gov (United States)

    Gross, Benjamin; Marinari, Maddalena; Hoffman, Mike; DeSimone, Kimberly; Burke, Peggy

    2015-01-01

    In this paper, the authors find empirical support for the effectiveness of the flipped classroom model. Using a quasi-experimental method, the authors compared students enrolled in flipped courses to their counterparts in more traditional lecture-based ones. A survey instrument was constructed to study how these two different groups of students…

  2. Enhancing the Design and Analysis of Flipped Learning Strategies

    Science.gov (United States)

    Jenkins, Martin; Bokosmaty, Rena; Brown, Melanie; Browne, Chris; Gao, Qi; Hanson, Julie; Kupatadze, Ketevan

    2017-01-01

    There are numerous calls in the literature for research into the flipped learning approach to match the flood of popular media articles praising its impact on student learning and educational outcomes. This paper addresses those calls by proposing pedagogical strategies that promote active learning in "flipped" approaches and improved…

  3. Flipping to Teach the Conceptual Foundations of Successful Workplace Writing

    Science.gov (United States)

    Campbell, Kim Sydow

    2016-01-01

    Flipping originated in science, technology, engineering, and mathematics fields, where didactic transmission of conceptual knowledge has been the standard pedagogy. Flipping has resulted in additional focus on procedural knowledge within class meetings. This article argues that business and professional writing pedagogy, which already focuses…

  4. Characterization of hybrid integrated all-optical flip-flop

    NARCIS (Netherlands)

    Liu, Y.; McDougall, R.; Seoane, J.; Kehayas, E.; Hill, M.T.; Maxwell, G.D.; Zhang, S.; Harmon, R.; Huijskens, Frans; Rivers, L.; Van Holm-Nielsen, P.; Martinez, J.M.; Herrera Llorente, J.; Ramos, F.; Marti, J.; Avramopoulos, H.; Jeppesen, P.; Koonen, A.M.J.; Poustie, A.; Dorren, H.J.S.

    2006-01-01

    We present a fully-packaged, hybrid-integrated all-optical flip-flop with separate optical set and reset operation. The flip-flop can control a wavelength converter to route 40 Gb/s data packets all-optically. The experimental results are given

  5. Flipping a College Calculus Course: A Case Study

    Science.gov (United States)

    Sahin, Alpaslan; Cavlazoglu, Baki; Zeytuncu, Yunus E.

    2015-01-01

    As online videos have become more easily available and more attractive to the new generation of students, and as new student-learning approaches tend to have more technology integration, the flipped classroom model has become very popular. The purpose of this study was to understand college students' views on flipped courses and investigate how…

  6. Flipped Instruction in a High School Science Classroom

    Science.gov (United States)

    Leo, Jonathan; Puzio, Kelly

    2016-01-01

    This paper reports on a quasi-experimental study examining the effectiveness of flipped instruction in a 9th grade biology classroom. This study included four sections of freshmen-level biology taught by the first author at a private secondary school in the Pacific Northwest. Using a block randomized design, two sections were flipped and two…

  7. Does the Flipped Classroom Improve Learning in Graduate Medical Education?

    Science.gov (United States)

    Riddell, Jeff; Jhun, Paul; Fung, Cha-Chi; Comes, James; Sawtelle, Stacy; Tabatabai, Ramin; Joseph, Daniel; Shoenberger, Jan; Chen, Esther; Fee, Christopher; Swadron, Stuart P

    2017-08-01

    The flipped classroom model for didactic education has recently gained popularity in medical education; however, there is a paucity of performance data showing its effectiveness for knowledge gain in graduate medical education. We assessed whether a flipped classroom module improves knowledge gain compared with a standard lecture. We conducted a randomized crossover study in 3 emergency medicine residency programs. Participants were randomized to receive a 50-minute lecture from an expert educator on one subject and a flipped classroom module on the other. The flipped classroom included a 20-minute at-home video and 30 minutes of in-class case discussion. The 2 subjects addressed were headache and acute low back pain. A pretest, immediate posttest, and 90-day retention test were given for each subject. Of 82 eligible residents, 73 completed both modules. For the low back pain module, mean test scores were not significantly different between the lecture and flipped classroom formats. For the headache module, there were significant differences in performance for a given test date between the flipped classroom and the lecture format. However, differences between groups were less than 1 of 10 examination items, making it difficult to assign educational importance to the differences. In this crossover study comparing a single flipped classroom module with a standard lecture, we found mixed statistical results for performance measured by multiple-choice questions. As the differences were small, the flipped classroom and lecture were essentially equivalent.

  8. The Perceived Effects of Flipped Teaching on Knowledge Acquisition

    Science.gov (United States)

    Newman, Galen; Kim, Jun-Hyun; Lee, Ryun Jung; Brown, Brandy A.; Huston, Sharon

    2016-01-01

    Increased demands for technological integration in higher education have resulted in new forms of course instruction. Under a flipped approach, students learn course materials outside the classroom while active learning methods are employed inside. This study focuses on the perceived effects of flipped instruction on knowledge acquisition in…

  9. Flipped Classroom: Effects on Education for the Case of Economics

    Science.gov (United States)

    Kurihara, Yutaka

    2016-01-01

    The notion of the flipped classroom has been received much attention in the literature as it may increase learning outcomes and learning effectiveness elementary and secondary education as well as university learning. In the author's class on international finance (economics) features a blended flipped classroom and lecture; questionnaires were…

  10. Evaluating the Flipped Classroom: A Randomized Controlled Trial

    Science.gov (United States)

    Wozny, Nathan; Balser, Cary; Ives, Drew

    2018-01-01

    Despite recent interest in flipped classrooms, rigorous research evaluating their effectiveness is sparse. In this study, the authors implement a randomized controlled trial to evaluate the effect of a flipped classroom technique relative to a traditional lecture in an introductory undergraduate econometrics course. Random assignment enables the…

  11. Flipping Preservice Elementary Teachers' Mathematics Anxieties

    Science.gov (United States)

    Dove, Anthony; Dove, Emily

    2017-01-01

    In preparing future elementary educators in mathematics, helping them overcome their anxieties of mathematics and teaching mathematics is paramount. This study examined how different instructional practices (in-class lecture, flipped learning with teacher-created videos, flipped classroom with Khan Academy videos) compared in improving students'…

  12. Teachers’ development in a flipped classroom for applied mathematics

    DEFF Research Database (Denmark)

    Triantafyllou, Evangelia; Timcenko, Olga; Kofoed, Lise

    2016-01-01

    In this paper, we discuss how the flipped classroom approach promoted teacher reflection and development. We look at the teaching cycle from a flipped instruction model perspective and we adjust it to cater for the reflection loops teachers are involved when designing, implementing and re-designi...

  13. Malaysian Students' Perceptions of Flipped Classroom: A Case Study

    Science.gov (United States)

    Zainuddin, Zamzami; Attaran, Mohammad

    2016-01-01

    The purpose of this study was to evaluate a class in University of Malaya where flipped learning was applied, and to examine students' perceptions and feedback towards flipped classroom. Data were collected using both quantitative and qualitative methods, i.e. survey, focus group and individual interviews. The results indicated that most students…

  14. The Implementation of a Flipped Classroom in Foreign Language Teaching

    Science.gov (United States)

    Basal, Ahmet

    2015-01-01

    Alongside the rise of educational technology, many teachers have been taking gradual but innovative steps to redesign their teaching methods. For example, in flipped learning or a flipped classroom, students watch instructional videos outside the classroom and do assignments or engage in activities inside the classroom. Language teachers are one…

  15. Implementing the Flipped Classroom in Teacher Education: Evidence from Turkey

    Science.gov (United States)

    Kurt, Gökçe

    2017-01-01

    The flipped classroom, a form of blended learning, is an emerging instructional strategy reversing a traditional lecture-based teaching model to improve the quality and efficiency of the teaching and learning process. The present article reports a study that focused on the implementation of the flipped approach in a higher education institution in…

  16. Re-Visiting the Flipped Classroom in a Design Context

    Science.gov (United States)

    Coyne, Richard David; Lee, John; Denitsa, Petrova

    2017-01-01

    After explaining our experience with a flipped classroom model of learning, we argue that the approach brings to light the dramaturgical and mediatized aspects of learning experiences that favour a closer connection between recorded content and "live" presentation by the lecturer. We adopted the flipped classroom approach to learning and…

  17. Flipped Classroom Research and Trends from Different Fields of Study

    Science.gov (United States)

    Zainuddin, Zamzami; Halili, Siti Hajar

    2016-01-01

    This paper aims to analyse the trends and contents of flipped classroom research based on 20 articles that report on flipped learning classroom initiatives from 2013-2015. The content analysis was used as a methodology to investigate methodologies, area of studies, technology tools or online platforms, the most frequently used keywords and works…

  18. Flipped Classrooms and Student Learning: Not Just Surface Gains

    Science.gov (United States)

    McLean, Sarah; Attardi, Stefanie M.; Faden, Lisa; Goldszmidt, Mark

    2016-01-01

    The flipped classroom is a relatively new approach to undergraduate teaching in science. This approach repurposes class time to focus on application and discussion; the acquisition of basic concepts and principles is done on the students' own time before class. While current flipped classroom research has focused on student preferences and…

  19. Exploring Flipped Classroom Effects on Second Language Learners' Cognitive Processing

    Science.gov (United States)

    Kim, Jeong-eun; Park, Hyunjin; Jang, Mijung; Nam, Hosung

    2017-01-01

    This study investigated the cognitive effects of the flipped classroom approach in a content-based instructional context by comparing second language learners' discourse in flipped vs. traditional classrooms in terms of (1) participation rate, (2) content of comments, (3) reasoning skills, and (4) interactional patterns. Learners in two intact…

  20. Curriculum Design of a Flipped Classroom to Enhance Haematology Learning

    Science.gov (United States)

    Porcaro, Pauline A.; Jackson, Denise E.; McLaughlin, Patricia M.; O'Malley, Cindy J.

    2016-01-01

    A common trend in higher education is the "flipped" classroom, which facilitates active learning during class. The flipped approach to teaching was instituted in a haematology "major" class and the students' attitudes and preferences for the teaching materials were surveyed. The curriculum design was explicit and involved four…

  1. Out of Classroom Instruction in the Flipped Classroom

    DEFF Research Database (Denmark)

    Triantafyllou, Evangelia; Timcenko, Olga

    2015-01-01

    This article presents experiences and student perceptions on the introduction of the flipped classroom model in two consecutive semesters at Media Technology department of Aalborg University, Copenhagen, Denmark. We introduced the flipped instruction model to a statistics course and a mathematics...

  2. Characterisation of hybrid integrated all-optical flip-flop

    DEFF Research Database (Denmark)

    Liu, Y.; McDougall, R.; Seoane, Jorge

    2006-01-01

    We present a fully-packaged, hybrid-integrated all-optical flip-flop with separate optical set and reset operation. The flip-flop can control a wavelength converter to route 40 Gb/s data packets all-optically. The experimental results are given....

  3. ALICE chip processor

    CERN Multimedia

    Maximilien Brice

    2003-01-01

    This tiny chip provides data processing for the time projection chamber on ALICE. Known as the ALICE TPC Read Out (ALTRO), this device was designed to minimize the size and power consumption of the TPC front end electronics. This single chip contains 16 low-power analogue-to-digital converters with six million transistors of digital processing and 8 kbits of data storage.

  4. Neutrino helicity flips via electroweak interactions and SN1987a

    International Nuclear Information System (INIS)

    Gaemers, K.J.F.; Gandhi, R.; Lattimer, J.M.

    1988-10-01

    Electroweak mechanisms via which neutrinos may flip helicity and become sterile are examined in detail. Exact and approximate expressions for a variety of flip processes relevant in astrophysics and cosmology, mediated by W,Z, and γ exchange, including their interference, are derived. It is shown that within the context of the Standard Model with massive neutrinos, for νe→νe scattering, σ Z flip /σ γ flip ∼ 6 X 10 3 , independent of particle masses and energies to a good approximation. It is also shown that using some general considerations and the fact that the observed anti ν e burst from SN1987a lasted several seconds, these weak interaction flip cross-sections can be used to derive an upper limit on μ and τ neutrino masses of ∼ 40 keV. Finally, some other consequences for astrophysics in general and supernovae in particular are briefly discussed. 29 refs.; 47 schemes

  5. Flipping SU(5) out of Trouble

    CERN Document Server

    Ellis, Jonathan Richard; Walker, J; Ellis, John

    2002-01-01

    Minimal supersymmetric SU(5) GUTs are being squeezed by the recent values of alpha_s, sin^2 theta_W, the lower limit on the lifetime for p to nubar K decay, and other experimental data. We show how the minimal flipped SU(5) GUT survives these perils, accommodating the experimental values of alpha_s and sin^2 theta_W and other constraints, while yielding a p to e/mu+ pi0 lifetime beyond the present experimental limit but potentially accessible to a further round of experiments. We exemplify our analysis using a set of benchmark supersymmetric scenarios proposed recently in a constrained MSSM framework.

  6. Effect of Solder-Joint Geometry on the Low-Cycle Fatigue Behavior of Sn- xAg-0.7Cu

    Science.gov (United States)

    Lee, Hwa-Teng; Huang, Kuo-Chen

    2016-12-01

    Low-cycle fatigue tests of Sn-Ag-Cu (SAC) Pb-free solder joints under fixed displacement were performed to evaluate the influence of Ag content (0-3 wt.%) and solder-joint geometry (barrel and hourglass types) on solder-joint fatigue behavior and reliability. The solder joints were composed of fine particles of Ag3Sn and Cu6Sn5, which aggregated as an eutectic constituent at grain boundaries of the primary β-Sn phase and formed a dense network structure. A decrease in the Ag content resulted in coarsening of the β-Sn and eutectic phases, which, in turn, decreased the strength of the joint and caused earlier failure. Solder joints in the hourglass form exhibited better fatigue performance with longer life than barrel-type joints. The sharp contact angle formed between the solder and the Cu substrate by the barrel-type joints concentrated stress, which compromised fatigue reliability. The addition of Ag to the solder, however, enhanced fatigue performance because of strengthening caused by Ag3Sn formation. The cracks of the barrel-type SAC solder joints originated mostly at the contact corner and propagated along the interfacial layer between the interfacial intermetallic compound (IMC) and solder matrix. Hourglass-type solder joints, however, demonstrated both crack initiation and propagation in the solder matrix (solder mode). The addition of 1.5-2.0 wt.% Ag to SAC solder appears to enhance the fatigue performance of solder joints while maintaining sufficient strength.

  7. Long-Term Effects of Soldering By-Products on Nickel-Coated Copper Wire

    Science.gov (United States)

    Rolin, T. D.; Hodge, R. E.

    2008-01-01

    An analysis of thirty-year-old, down graded flight cables was conducted to determine the makeup of a green material on the surface of the shielded wire near soldered areas and to ascertain if the green material had corroded the nickel-coated copper wire. Two likely candidates were possible due to the handling and environments to which these cables were exposed. The flux used to solder the cables is known to contain abietic acid, a carboxylic acid found in many pine rosins used for the soldering process. The resulting material copper abietate is green in color and is formed during the application of heat during soldering operations. Copper (II) chloride, which is also green in color is known to contaminate flight parts and is corrosive. Data is presented that shows the material is copper abietate, not copper (II) chloride, and more importantly that the abietate does not aggressively attack nickel-plated copper wire.

  8. Laser welding of vas deferens in rodents: initial experience with fluid solders.

    Science.gov (United States)

    Trickett, R I; Wang, D; Maitz, P; Lanzetta, M; Owen, E R

    1998-01-01

    This study evaluates the use of sutureless laser welding for vasovasostomy. In 14 rodents, the left vas deferens underwent vasovasostomy using an albumin-based solder applied to the adventitia of the vas deferens. The solder contained the dye, indocyanine green, to allow selective absorption and denaturation by a fiber-coupled 800-nm diode laser. The right vas deferens served as a control, receiving conventional layered microsurgical repair. We used a removable 4/0 nylon stent and microclamps to appose the vas deferens during repair, with no need for stay sutures. The mean time to perform laser solder repair (23.5 min) and conventional repair (23.3 min) were not significantly different (P=0.91). However, examination after 8 weeks showed that granuloma formation (G) and patency (P) rates for the conventional suture technique (G, 14%; P, 93%) were significantly better than observed for the laser solder technique (G, 57%; P, 50%).

  9. Effects of rework on adhesion of Pb-In soldered gold thick films

    International Nuclear Information System (INIS)

    Gehman, R.W.; Becka, G.A.; Losure, J.A.

    1982-02-01

    The feasibility of repeatedly reworking Pb-In soldered joints on gold thick films was evaluated. Nailhead adhesion tests on soldered thick films typically resulted in failure within the bulk solder (50 In-50 Pb). Average strengths increased with each rework, and the failure mode changed. An increase in metalization lift-off occurred with successive reworks. An investigation was initiated to determine why these changes occurred. Based on this work, the thick film adhesion to the substrate appeared to be lowered by indium reduction of cadmium oxide and by formation of a weak, brittle intermetallic compound, Au 9 In 4 . It was concluded that two solder reworks could be conducted without significant amounts of metallization lift-off during nailhead testing

  10. Nanoscale Soldering of Positioned Carbon Nanotubes using Highly Conductive Electron Beam Induced Gold Deposition

    DEFF Research Database (Denmark)

    Madsen, Dorte Nørgaard; Mølhave, Kristian; Mateiu, Ramona Valentina

    2003-01-01

    We have developed an in-situ method for controlled positioning of carbon nanotubes followed by highly conductive contacting of the nanotubes, using electron beam assisted deposition of gold. The positioning and soldering process takes place inside an Environmental Scanning Electron Microscope (E...... in a carbon matrix. Nanoscale soldering of multi-walled carbon nanotubes (MWNT) onto microelectrodes was achieved by deposition of a conducting gold line across a contact point between nanotube and electrode. The solderings were found to be mechanically stronger than the carbon nanotubes. We have positioned...... MWNTs to bridge the gap between two electrodes, and formed soldering bonds between the tube and each of the electrodes. All nanotube bridges showed ohmic resistances in the range 10-30 kΩ. We observed no increase in resistance after exposing the MWNT bridge to air for days....

  11. Microstructural Evolution and Mechanical Behavior of High Temperature Solders: Effects of High Temperature Aging

    Science.gov (United States)

    Hasnine, M.; Tolla, B.; Vahora, N.

    2018-04-01

    This paper explores the effects of aging on the mechanical behavior, microstructure evolution and IMC formation on different surface finishes of two high temperature solders, Sn-5 wt.% Ag and Sn-5 wt.% Sb. High temperature aging showed significant degradation of Sn-5 wt.% Ag solder hardness (34%) while aging has little effect on Sn-5 wt.% Sb solder. Sn-5 wt.% Ag experienced rapid grain growth as well as the coarsening of particles during aging. Sn-5 wt.% Sb showed a stable microstructure due to solid solution strengthening and the stable nature of SnSb precipitates. The increase of intermetallic compound (IMC) thickness during aging follows a parabolic relationship with time. Regression analysis (time exponent, n) indicated that IMC growth kinetics is controlled by a diffusion mechanism. The results have important implications in the selection of high temperature solders used in high temperature applications.

  12. Assessing Behavioral Engagement in Flipped and Non-Flipped Mathematics Classrooms: Teacher Abilities and Other Potential Factors

    Science.gov (United States)

    Hodgson, Theodore R.; Cunningham, Abby; McGee, Daniel; Kinne, Lenore J.; Murphy, Teri J.

    2017-01-01

    There is a growing evidence that flipped classrooms are associated with increased levels of student engagement, as compared to engagement in "traditional" settings. Much of this research, however, occurs in post-secondary classrooms and is based upon self-reported engagement data. This study seeks to extend existing flipped classroom…

  13. Do Students Learn More from a Flip? An Exploration of the Efficacy of Flipped and Traditional Lessons

    Science.gov (United States)

    DeSantis, Joshua; Van Curen, Rebecca; Putsch, Jake; Metzger, Justin

    2015-01-01

    Flipped lesson planning, as popularized by Bergman & Sams (2012a), has been viewed by many as a revolutionary pedagogy, tailor-made for the twenty-first century classroom. Enthusiasm for flipped lesson planning has out-paced the collection of data that might determine its effectiveness. This paper presents the results of a study that compared…

  14. Flipping and Still Learning: Experiences of a Flipped Classroom Approach for a Third-Year Undergraduate Human Geography Course

    Science.gov (United States)

    Graham, Marnie; McLean, Jessica; Read, Alexander; Suchet-Pearson, Sandie; Viner, Venessa

    2017-01-01

    The flipped classroom approach, a form of blended learning, is currently popular in education praxis. Initial reports on the flipped classroom include that it offers opportunities to increase student engagement and build meaningful learning and teaching experiences. In this article, we analyse teacher and student experiences of a trial flipped…

  15. The creep behavior of In-Ag eutectic solder joints

    International Nuclear Information System (INIS)

    Reynolds, H.L.; Kang, S.H.; Morris, J.W. Jr.; Univ. of California, Berkeley, CA

    1999-01-01

    The addition of 3 wt.% Ag to In results in a eutectic composition with improved mechanical properties while only slightly lowering the melting temperature. Steady-state creep properties of In-Ag eutectic solder joints have been measured using constant load tests at 0, 30, 60, and 90 C. Constitutive equations are derived to describe the creep behavior. The data are well represented by an equation of the form proposed by Dorn: a power-law equation applies to each independent creep mechanism. Two parallel mechanisms were observed for the In-Ag eutectic joints. The high-stress mechanism is a bulk mechanism with a thermal dependence dominated by the thermal dependence of creep in the In-rich matrix. The low-stress mechanism is a grain boundary mechanism. Results of this work are discussed with regard to creep behavior of typical eutectic systems

  16. Nanoconstruction by welding individual metallic nanowires together using nanoscale solder

    International Nuclear Information System (INIS)

    Peng, Y; Inkson, B J; Cullis, A G

    2010-01-01

    This work presents a new bottom-up nanowelding technique enabling building blocks to be assembled and welded together into complex 3D nanostructures using nanovolumes of metal solder. The building blocks of gold nanowires, (Co 72 Pt 28 /Pt) n multilayer nanowires, and nanosolder Sn 99 Au 1 alloy nanowires were successfully fabricated by a template technique. Individual metallic nanowires were picked up and assembled together. Conductive nanocircuits were then welded together using similar or dissimilar nanosolder material. At the weld sites, nanoscale volumes of a chosen metal are deposited using nanosolder of a sacrificial nanowire, which ensures that the nanoobjects to be bonded retain their structural integrity. The whole nanowelding process is clean, controllable and reliable, and ensures both mechanically strong and electrically conductive contacts.

  17. Soldered Contact and Current Risetime Effects on Negative Polarity Wire Array Z-pinches

    International Nuclear Information System (INIS)

    Chalenski, D. A.; Kusse, B. R.; Greenly, J. B.; Blesener, I. C.; McBride, R. D.; Hammer, D. A.; Knapp, P. F.

    2009-01-01

    The Cornell University COBRA pulser is a nominal 1 MA machine, capable of driving up to 32 wire cylindrical Z-pinch arrays. COBRA can operate with variable current risetimes ranging from 100 ns to 200 ns (short and long pulse, respectively). Wires are typically strung with a ''press'' contact to the electrode hardware, where the wire is loosely pulled against the hardware and held there to establish electrical contact. The machine is normally negative, but a bolt-on convolute can be used to modify the current path and effectively produce positive polarity operation at the load.Previous research with single wires on a 1-5 kA pulser has shown that soldering the wire, thereby improving the wire/electrode contact, and operating in positive polarity can improve the energy deposition into the wire and enhance wire core expansion. Negative polarity showed no difference. Previous experiments on the negative polarity, 20 MA, 100 ns Z accelerator have shown that improving the contact improved the x-ray yield.Cornell data were collected on 16-wire Aluminum Z-pinch arrays in negative polarity. Experiments were conducted with both short and long current pulses with soldered and no-soldered wire/electrode contacts. The initiation, ablation, implosion and stagnation phases were compared for these four conditions. Time dependent x-ray signals were measured using diodes and diamond detectors. An inductive voltage monitor was used to infer minimum current radius achieved, as defined by a uniform shell of current moving radially inward, producing a time dependent inductance. Total energy data were collected with a metal-strip bolometer. Self-emission data were collected by an XUV 4-frame camera and an optical streak camera.In negative polarity and with short pulses, soldering appeared to produce a smaller radius pinch and decrease variations in the x-ray pulse shape. The bolometer, laser backlighter, 4-frame and streak cameras showed negligible differences in the initiation ablation

  18. Effects of voids on thermal-mechanical reliability of lead-free solder joints

    Directory of Open Access Journals (Sweden)

    Benabou Lahouari

    2014-06-01

    Full Text Available Reliability of electronic packages has become a major issue, particularly in systems used in electrical or hybrid cars where severe operating conditions must be met. Many studies have shown that solder interconnects are critical elements since many failure mechanisms originate from their typical response under thermal cycles. In this study, effects of voids in solder interconnects on the electronic assembly lifetime are estimated based on finite element simulations.

  19. Investigation into mechanical properties of joints of heterogeneous materials brazed with high-temperature solders

    International Nuclear Information System (INIS)

    Lomenko, V.I.; Merkushev, V.P.; Borodina, L.M.; Sycheva, T.S.; Tokhtina, O.A.; Frolov, N.N.

    1988-01-01

    Mechanical properties of copper joints with copper, 12Kh18M10T steel and KhD50 composite obtained by vacuum brazing by copper-titanium solder as compared with properties of joints brazed by PSr 72 and PMFOTsr 6-4-0.03 solders in hydrogen are studied. Dependences of joints strength on temperature of contact - reactive vacuum brazing are obtained. Possible applications of joints of dissimilar materials in electrovacuum devices subjected to the effect of dynamic loadings are established

  20. Dye-enhanced protein solders and patches in laser-assisted tissue welding.

    Science.gov (United States)

    Small, W; Heredia, N J; Maitland, D J; Da Silva, L B; Matthews, D L

    1997-01-01

    This study examines the use of dye-enhanced protein bonding agents in 805 nm diode laser-assisted tissue welding. A comparison of an albumin liquid solder and collagen solid-matrix patches used to repair arteriotomies in an in vitro porcine model is presented. Extrinsic bonding media in the form of solders and patches have been used to enhance the practice of laser tissue welding. Preferential absorption of the laser wavelength has been achieved by the incorporation of chromophores. Both the solder and the patch included indocyanine green dye (ICG) to absorb the 805 nm continuous-wave diode laser light used to perform the welds. Solder-mediated welds were divided into two groups (high power/short exposure and low power/long exposure), and the patches were divided into three thickness groups ranging from 0.1 to 1.3 mm. The power used to activate the patches was constant, but the exposure time was increased with patch thickness. Burst pressure results indicated that solder-mediated and patched welds yielded similar average burst strengths in most cases, but the patches provided a higher success rate (i.e., more often exceeded 150 mmHg) and were more consistent (i.e., smaller standard deviation) than the solder. The strongest welds were obtained using 1.0-1.3 mm thick patches, while the high power/short exposure solder group was the weakest. Though the solder and patches yielded similar acute weld strengths, the solid-matrix patches facilitated the welding process and provided consistently strong welds. The material properties of the extrinsic agents influenced their performance.

  1. Evaluation of low-residue soldering for military and commercial applications: A report from the Low-Residue Soldering Task Force

    Energy Technology Data Exchange (ETDEWEB)

    Iman, R.L.; Anderson, D.J. [Sandia National Labs., Albuquerque, NM (United States); Burress, R.V. [SEHO (United States)] [and others

    1995-06-01

    The LRSTF combined the efforts of industry, military, and government to evaluate low-residue soldering processes for military and commercial applications. These processes were selected for evaluation because they provide a means for the military to support the presidential mandate while producing reliable hardware at a lower cost. This report presents the complete details and results of a testing program conducted by the LRSTF to evaluate low-residue soldering for printed wiring assemblies. A previous informal document provided details of the test plan used in this evaluation. Many of the details of that test plan are contained in this report. The test data are too massive to include in this report, however, these data are available on disk as Excel spreadsheets upon request. The main purpose of low-residue soldering is to eliminate waste streams during the manufacturing process.

  2. Re-Envisioning the Archaic Higher Education Learning Environment: Implementation Processes for Flipped Classrooms

    Science.gov (United States)

    Rabidoux, Salena; Rottmann, Amy

    2018-01-01

    Flipped classrooms are often utilized in PK-12 classrooms; however, there is also a growing trend of flipped classrooms in higher education. This paper presents the benefits and limitations of implementing flipped classrooms in higher education as well as resources for integrating a flipped classroom design to instruction. The various technology…

  3. Effect of gamma radiation on micromechanical hardness of lead-free solder joint

    Energy Technology Data Exchange (ETDEWEB)

    Paulus, Wilfred [Universiti Kebangsaan Malaysia, Bangi, 43600 Kajang, Selangor (Malaysia); Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Rahman, Irman Abdul; Jalar, Azman; Kamil, Insan; Bakar, Maria Abu [Universiti Kebangsaan Malaysia, Bangi, 43600 Kajang, Selangor (Malaysia); Yusoff, Wan Yusmawati Wan [Universiti Pertahanan Nasional Malaysia, Kem Sg. Besi, 57000 Kuala Lumpur (Malaysia)

    2015-09-25

    Lead-free solders are important material in nano and microelectronic surface mounting technology for various applications in bio medicine, environmental monitoring, spacecraft and satellite instrumentation. Nevertheless solder joint in radiation environment needs higher reliability and resistance to any damage caused by ionizing radiations. In this study a lead-free 99.0Sn0.3Ag0.7Cu wt.% (SAC) solder joint was developed and subjected to various doses of gamma radiation to investigate the effects of the ionizing radiation to micromechanical hardness of the solder. Averaged hardness of the SAC joint was obtained from nanoindentation test. The results show a relationship between hardness values of indentations and the increment of radiation dose. Highest mean hardness, 0.2290 ± 0.0270 GPa was calculated on solder joint which was exposed to 5 Gray dose of gamma radiation. This value indicates possible radiation hardening effect on irradiated solder. The hardness gradually decreased to 0.1933 ± 0.0210 GPa and 0.1631 ± 0.0173 GPa when exposed to doses 50 and 500 gray respectively. These values are also lower than the hardness of non irradiated sample which was calculated as 0.2084 ± 0.0.3633 GPa indicating possible radiation damage and needs further related atomic dislocation study.

  4. Characterization of the microstructure of tin-silver lead free solder

    Energy Technology Data Exchange (ETDEWEB)

    Hurtony, Tamás, E-mail: hurtony@ett.bme.hu [Department of Electronics Technology, Budapest University of Technology and Economics, Egry József utca 18, Budapest, H-1111 (Hungary); Szakál, Alex; Almásy, László [Neutron Spectroscopy Department, Wigner Research Centre for Physics, Budapest (Hungary); Len, Adél [Neutron Spectroscopy Department, Wigner Research Centre for Physics, Budapest (Hungary); Faculty of Engineering and Information Technology, University of Pécs (Hungary); Kugler, Sándor [Department of Theoretical Physics, Budapest University of Technology and Economics (Hungary); Bonyár, Attila; Gordon, Péter [Department of Electronics Technology, Budapest University of Technology and Economics, Egry József utca 18, Budapest, H-1111 (Hungary)

    2016-07-05

    Reliability and lifetime are the two most relevant design considerations in the production of safety critical assemblies. For example in a modern automobile dozens of electronic assemblies are integrated in which thousands of solder joints are mounting the electronic components to the printed circuit boards. There exists no standardised and universal observation method for characterising the fine microstructure of such solder joints. Previously we have developed a new method for the quantitative characterization of lead-free solder alloys and in present study the validity of the proposed method is demonstrated. Microstructure of Sn-3.5Ag lead free solder alloy was investigated by electrochemical impedance spectroscopy. Solder samples were solidified with different cooling rates in order to induce differences in the microstructure. Microstructure of the ingots was revealed by selective electrochemical etching. Electrochemical impedance spectra (EIS) were measured before and after the selective etching process. The complex impedance spectra contain information about microstructure of the solder alloys. Comparison and modelling of two EIS spectra allowed obtaining a characteristic parameter of surface structure of the etched specimens. The EIS measurements were complemented with small angle neutron scattering measurements and scanning electron microscopy, in order to correlate the EIS parameter with the magnitude of the interface of the β-Sn and Ag{sub 3}Sn phases.

  5. A Probabilistic Approach to Predict Thermal Fatigue Life for Ball Grid Array Solder Joints

    Science.gov (United States)

    Wei, Helin; Wang, Kuisheng

    2011-11-01

    Numerous studies of the reliability of solder joints have been performed. Most life prediction models are limited to a deterministic approach. However, manufacturing induces uncertainty in the geometry parameters of solder joints, and the environmental temperature varies widely due to end-user diversity, creating uncertainties in the reliability of solder joints. In this study, a methodology for accounting for variation in the lifetime prediction for lead-free solder joints of ball grid array packages (PBGA) is demonstrated. The key aspects of the solder joint parameters and the cyclic temperature range related to reliability are involved. Probabilistic solutions of the inelastic strain range and thermal fatigue life based on the Engelmaier model are developed to determine the probability of solder joint failure. The results indicate that the standard deviation increases significantly when more random variations are involved. Using the probabilistic method, the influence of each variable on the thermal fatigue life is quantified. This information can be used to optimize product design and process validation acceptance criteria. The probabilistic approach creates the opportunity to identify the root causes of failed samples from product fatigue tests and field returns. The method can be applied to better understand how variation affects parameters of interest in an electronic package design with area array interconnections.

  6. A Novel Technique for the Connection of Ceramic and Titanium Implant Components Using Glass Solder Bonding

    Directory of Open Access Journals (Sweden)

    Enrico Mick

    2015-07-01

    Full Text Available Both titanium and ceramic materials provide specific advantages in dental implant technology. However, some problems, like hypersensitivity reactions, corrosion and mechanical failure, have been reported. Therefore, the combining of both materials to take advantage of their pros, while eliminating their respective cons, would be desirable. Hence, we introduced a new technique to bond titanium and ceramic materials by means of a silica-based glass ceramic solder. Cylindrical compound samples (Ø10 mm × 56 mm made of alumina toughened zirconia (ATZ, as well as titanium grade 5, were bonded by glass solder on their end faces. As a control, a two-component adhesive glue was utilized. The samples were investigated without further treatment, after 30 and 90 days of storage in distilled water at room temperature, and after aging. All samples were subjected to quasi-static four-point-bending tests. We found that the glass solder bonding provided significantly higher bending strength than adhesive glue bonding. In contrast to the glued samples, the bending strength of the soldered samples remained unaltered by the storage and aging treatments. Scanning electron microscopy (SEM and energy-dispersive X-ray (EDX analyses confirmed the presence of a stable solder-ceramic interface. Therefore, the glass solder technique represents a promising method for optimizing dental and orthopedic implant bondings.

  7. Wall-slip effects in SnAgCu solder pastes used in electronics assembly applications

    International Nuclear Information System (INIS)

    Mallik, S.; Ekere, N.N.; Durairaj, R.; Marks, A.E.; Seman, A.

    2009-01-01

    Solder paste is the most important strategic bonding material used in the assembly of surface mount components in electronics manufacturing. As the trend towards miniaturisation of electronic products continues, there is an increasing demand for better understanding of the flow and deformation that is, the rheological behaviour of solder paste formulations. Wall slip plays an important role in characterising the flow behaviour of solder paste materials. The problem of wall slip arises due to the various attractive and repulsive forces acting between the solder particles and the walls of the measuring geometry. These interactions could lead to the presence of a thin solvent layer adjacent to the wall, which gives rise to slippage. In rheological measurements, slip effects can generally be avoided by using roughened surfaces for measuring geometries. In this paper, a novel technique is developed to study the effect of wall slip in the rheological measurements of lead-free solder paste. The viscosity and oscillatory data obtained for three different solder paste samples (from measuring geometries of different surface roughness) have been analysed and compared. In viscosity measurements, slip effects were dominant at low shear rates and the use of serrated surfaces was found to be quite effective in minimizing slip effects. Oscillatory measurements were also affected by roughening the surfaces of measuring geometries.

  8. The Effect of Gap Angle on Tensile Strength of Preceramic Base Metal Solder Joints.

    Science.gov (United States)

    Fattahi, Farnaz; Hashemi Ardakani, Zahra; Hashemi Ardakani, Maryam

    2015-12-01

    Soldering is a process commonly used in fabricating dental prosthesis. Since most soldered prosthesis fail at the solder joints; the joint strength is of utmost importance. The purpose of this study was to evaluate the effect of gap angle on the tensile strength of base metal solder joints. A total number of 40 Ni-Cr samples were fabricated according to ADA/ISO 9693 specifications for tensile test. Samples were cut at the midpoint of the bar, and were placed at the considered angles by employing an explicitly designed device. They were divided into 4 groups regarding the gap angle; Group C (control group) with parallel gap on steady distance of 0.2mm, Group 1: 10°, Group 2: 20°, and Group3: 30° gap angles. When soldered, the specimens were all tested for tensile strength using a universal testing machine at a cross-head speed of 0.5 mm/min with a preload of 10N. Kruskal-Wallis H test was used to compare tensile strength among the groups (ptensile strength values obtained from the study groups were respectively 307.84, 391.50, 365.18, and 368.86 MPa. The tensile strength was not statistically different among the four groups in general (p≤ 0.490). Making the gap angular at the solder joints and the subsequent unsteady increase of the gap distance would not change the tensile strength of the joint.

  9. Rheological characterisation and printing performance of Sn/Ag/Cu solder pastes

    International Nuclear Information System (INIS)

    Durairaj, R.; Ramesh, S.; Mallik, S.; Seman, A.; Ekere, N.

    2009-01-01

    Lead-free solder paste printing process accounts for majority of the assembly defects in the electronic manufacturing industry. The study investigates rheological behaviour and stencil printing performance of the lead-free solder pastes (Sn/Ag/Cu). Oscillatory stress sweep test was carried out to study the visco-elastic behaviour of the lead-free solder pastes. The visco-elastic behaviour of the paste encompasses solid and liquid characteristic of the paste, which could be used to study the flow behaviour experienced by the pastes during the stencil printing process. From this study, it was found that the solid characteristics (G') is higher than the liquid characteristic (G'') for the pastes material. In addition, the results from the study showed that the solder paste with a large G' = G'' has a higher cohesiveness resulting in poor withdrawal of the paste during the stencil printing process. The phase angles (δ) was used to correlate the quality of the dense suspensions to the formulation of solder paste materials. This study has revealed the value of having a rheological measurement for explaining and characterising solder pastes for stencil printing. As the demand for lead free pastes increases rheological measurements can assist with the formulation or development of new pastes.

  10. Study on interfacial reaction between lead-free solders and alternative surface finishes

    International Nuclear Information System (INIS)

    Siti Rabiatul Aisha; Ourdjini, A.; Saliza Osman

    2007-01-01

    This study investigates the interfacial reactions occurring during reflow soldering between Sn-Ag-Cu lead-free solder and two surface finishes: electroless nickel/ immersion gold (ENIG) and immersion silver (IAg). The study focuses on interfacial reactions evolution and growth kinetics of intermetallic compounds (IMC) formed during soldering and isothermal ageing at 150 degree Celsius for up to 2000 hours. Optical and scanning electron microscopy were used to measure IMC thickness and examine the morphology of IMC respectively, whereas the IMC phases were identified by energy dispersive X-ray analysis (EDX). The results showed that the IMC formed on ENIG finish is thinner compared to that formed on IAg finish. For IAg surface finish, Cu 6 Sn 5 IMCs with scallop morphology are formed at the solder/ surface finish interface after reflow while a second IMC, Cu 3 Sn was formed between the copper and Cu 6 Sn 5 IMC after the isothermal ageing treatment. For ENIG surface finish both (Cu,Ni) 6 Sn 5 and (Ni,Cu) 3 Sn 4 are formed after soldering. Isothermal aging of the solder joints formed on ENIG finish was found to have a significant effect on the morphology of the intermetallics by transforming to more spherical and denser morphology in addition to increase i their thickness with increased ageing time. (author)

  11. Comparative shear tests of some low temperature lead-free solder pastes

    Science.gov (United States)

    Branzei, Mihai; Plotog, Ioan; Varzaru, Gaudentiu; Cucu, Traian C.

    2016-12-01

    The range of electronic components and as a consequence, all parts of automotive electronic equipment operating temperatures in a vehicle is given by the location of that equipment, so the maximum temperature can vary between 358K and 478K1. The solder joints could be defined as passive parts of the interconnection structure of automotive electronic equipment, at a different level, from boards of electronic modules to systems. The manufacturing costs reduction necessity and the RoHS EU Directive3, 7 consequences generate the trend to create new Low-Temperature Lead-Free (LTLF) solder pastes family9. In the paper, the mechanical strength of solder joints and samples having the same transversal section as resistor 1206 case type made using the same LTLF alloys into Vapour Phase Soldering (VPS) process characterized by different cooling rates (slow and rapid) and two types of test PCBs pads finish, were benchmarked at room temperature. The presented work extends the theoretical studies and experiments upon heat transfer in VPSP in order to optimize the technology for soldering process (SP) of automotive electronic modules and could be extended for home and modern agriculture appliances industry. The shear forces (SF) values of the LTLF alloy samples having the same transversal section as resistor 1206 case type will be considered as references values of a database useful in the new solder alloy creation processes and their qualification for automotive electronics domain.

  12. Investigation on solder joint strength of nickel tin-plated and CRS tabs with PCB

    International Nuclear Information System (INIS)

    Luay Hussain

    2002-01-01

    Failure analysis on easily peels off Nickel and CRS steel tabs from PCB was carried out. Nickel Tin plated tabs, CRS steel tabs and tube were joined to the PCB using reflow/ convection soldering, in an oven. The solder paste composition is Sn36/Pb35/Ag2. Peel test was conducted and it was found that many tabs could be easily peeled off with low force. Porosities which varies from 0.4 mm to < 0.01mm in diameter, developed during soldering process and solidification was noted. It was found, the number, size and position of these porosities inside the solder layer on both parts of the tabs affect the peel strength. Scanning Electron Microscopy study and EDX analysis were carried out. It was found that the low peel strength values were due to the combination of generation and development of porosities during soldering process which act as stress concentrators and the evolution (growth) of eutectic Sn/Pb and Sn/Ni/Cu brittle grainy phase. Large eutectic microstructure with brittle Sn-Ni-Cu grainy phase enhances the failure with low peeling forces. Sample showing no feature of Sn/Ni/Cu grain gave high peeling strength value. Solder reflow, an important process, can result in strength enhancement (if it was controlled for example in a furnace). (Author)

  13. Properties and Microstructures of Sn-Ag-Cu-X Lead-Free Solder Joints in Electronic Packaging

    Directory of Open Access Journals (Sweden)

    Lei Sun

    2015-01-01

    Full Text Available SnAgCu solder alloys were considered as one of the most popular lead-free solders because of its good reliability and mechanical properties. However, there are also many problems that need to be solved for the SnAgCu solders, such as high melting point and poor wettability. In order to overcome these shortcomings, and further enhance the properties of SnAgCu solders, many researchers choose to add a series of alloying elements (In, Ti, Fe, Zn, Bi, Ni, Sb, Ga, Al, and rare earth and nanoparticles to the SnAgCu solders. In this paper, the work of SnAgCu lead-free solders containing alloying elements and nanoparticles was reviewed, and the effects of alloying elements and nanoparticles on the melting temperature, wettability, mechanical properties, hardness properties, microstructures, intermetallic compounds, and whiskers were discussed.

  14. Fair loss-tolerant quantum coin flipping

    International Nuclear Information System (INIS)

    Berlin, Guido; Brassard, Gilles; Bussieres, Felix; Godbout, Nicolas

    2009-01-01

    Coin flipping is a cryptographic primitive in which two spatially separated players, who do not trust each other, wish to establish a common random bit. If we limit ourselves to classical communication, this task requires either assumptions on the computational power of the players or it requires them to send messages to each other with sufficient simultaneity to force their complete independence. Without such assumptions, all classical protocols are so that one dishonest player has complete control over the outcome. If we use quantum communication, on the other hand, protocols have been introduced that limit the maximal bias that dishonest players can produce. However, those protocols would be very difficult to implement in practice because they are susceptible to realistic losses on the quantum channel between the players or in their quantum memory and measurement apparatus. In this paper, we introduce a quantum protocol and we prove that it is completely impervious to loss. The protocol is fair in the sense that either player has the same probability of success in cheating attempts at biasing the outcome of the coin flip. We also give explicit and optimal cheating strategies for both players.

  15. Development of a Flipped Medical School Dermatology Module.

    Science.gov (United States)

    Fox, Joshua; Faber, David; Pikarsky, Solomon; Zhang, Chi; Riley, Richard; Mechaber, Alex; O'Connell, Mark; Kirsner, Robert S

    2017-05-01

    The flipped classroom module incorporates independent study in advance of in-class instructional sessions. It is unproven whether this methodology is effective within a medical school second-year organ system module. We report the development, implementation, and effectiveness of the flipped classroom methodology in a second-year medical student dermatology module at the University of Miami Leonard M. Miller School of Medicine. In a retrospective cohort analysis, we compared attitudinal survey data and mean scores for a 50-item multiple-choice final examination of the second-year medical students who participated in this 1-week flipped course with those of the previous year's traditional, lecture-based course. Each group comprised nearly 200 students. Students' age, sex, Medical College Admission Test scores, and undergraduate grade point averages were comparable between the flipped and traditional classroom students. The flipped module students' mean final examination score of 92.71% ± 5.03% was greater than that of the traditional module students' 90.92% ± 5.51% ( P flipped methodology to attending live lectures or watching previously recorded lectures. The flipped classroom can be an effective instructional methodology for a medical school second-year organ system module.

  16. Results of a Flipped Classroom Teaching Approach in Anesthesiology Residents.

    Science.gov (United States)

    Martinelli, Susan M; Chen, Fei; DiLorenzo, Amy N; Mayer, David C; Fairbanks, Stacy; Moran, Kenneth; Ku, Cindy; Mitchell, John D; Bowe, Edwin A; Royal, Kenneth D; Hendrickse, Adrian; VanDyke, Kenneth; Trawicki, Michael C; Rankin, Demicha; Guldan, George J; Hand, Will; Gallagher, Christopher; Jacob, Zvi; Zvara, David A; McEvoy, Matthew D; Schell, Randall M

    2017-08-01

    In a flipped classroom approach, learners view educational content prior to class and engage in active learning during didactic sessions. We hypothesized that a flipped classroom improves knowledge acquisition and retention for residents compared to traditional lecture, and that residents prefer this approach. We completed 2 iterations of a study in 2014 and 2015. Institutions were assigned to either flipped classroom or traditional lecture for 4 weekly sessions. The flipped classroom consisted of reviewing a 15-minute video, followed by 45-minute in-class interactive sessions with audience response questions, think-pair-share questions, and case discussions. The traditional lecture approach consisted of a 55-minute lecture given by faculty with 5 minutes for questions. Residents completed 3 knowledge tests (pretest, posttest, and 4-month retention) and surveys of their perceptions of the didactic sessions. A linear mixed model was used to compare the effect of both formats on knowledge acquisition and retention. Of 182 eligible postgraduate year 2 anesthesiology residents, 155 (85%) participated in the entire intervention, and 142 (78%) completed all tests. The flipped classroom approach improved knowledge retention after 4 months (adjusted mean = 6%; P  = .014; d  = 0.56), and residents preferred the flipped classroom (pre = 46%; post = 82%; P  flipped classroom approach to didactic education resulted in a small improvement in knowledge retention and was preferred by anesthesiology residents.

  17. Studenters erfaringer med Flipped Classroom i en helsefagutdanning

    Directory of Open Access Journals (Sweden)

    Christine Tørris

    2015-12-01

    Full Text Available Background: The flipped classroom approach has gained increased attention in educational research literature. The purpose of this study was to investigate how students experience a flipped classroom approach in health education, compared to ordinary lectures. Method: Bachelor students (n=25 who watched the video-based material in the flipped classrooms pre-session, answered a questionnaire to evaluate their flipped classroom experience. The questionnaire consisted of both closed and open questions. Results: Ninety six per cent (24/25 of respondents found the video-based material in the pre-session useful. Seventy six per cent (19/25 of respondents found that the flipped classroom approach resulted in the highest learning outcome, over the traditional approach (16%, 4/25. Barriers to the flipped classroom approach was technical problems with the video-based material, such as screen view. Conclusion: The flipped classroom approach is promising as an acceptable approach for teaching in health science curricular in higher education.

  18. An evaluation of the lap-shear test for Sn-rich solder/Cu couples: Experiments and simulation

    Science.gov (United States)

    Chawla, N.; Shen, Y.-L.; Deng, X.; Ege, E. S.

    2004-12-01

    The lap-shear technique is commonly used to evaluate the shear, creep, and thermal fatigue behavior of solder joints. We have conducted a parametric experimental and modeling study, on the effect of testing and geometrical parameters on solder/copper joint response in lap-shear. It was shown that the farfield applied strain is quite different from the actual solder strain (measured optically). Subtraction of the deformation of the Cu substrate provides a reasonable approximation of the solder strain in the elastic regime, but not in the plastic regime. Solder joint thickness has a profound effect on joint response. The solder response moves progressively closer to “true” shear response with increasing joint thickness. Numerical modeling using finite-element analyses were performed to rationalize the experimental findings. The same lap-shear configuration was used in the simulation. The input response for solder was based on the experimental tensile test result on bulk specimens. The calculated shear response, using both the commonly adopted far-field measure and the actual shear strain in solder, was found to be consistent with the trends observed in the lap-shear experiments. The geometric features were further explored to provide physical insight into the problem. Deformation of the substrate was found to greatly influence the shear behavior of the solder.

  19. Properties and Microstructures of Sn-Ag-Cu-X Lead-Free Solder Joints in Electronic Packaging

    OpenAIRE

    Sun, Lei; Zhang, Liang

    2015-01-01

    SnAgCu solder alloys were considered as one of the most popular lead-free solders because of its good reliability and mechanical properties. However, there are also many problems that need to be solved for the SnAgCu solders, such as high melting point and poor wettability. In order to overcome these shortcomings, and further enhance the properties of SnAgCu solders, many researchers choose to add a series of alloying elements (In, Ti, Fe, Zn, Bi, Ni, Sb, Ga, Al, and rare earth) and nanoparti...

  20. Evaluation of a flipped classroom approach to learning introductory epidemiology.

    Science.gov (United States)

    Shiau, Stephanie; Kahn, Linda G; Platt, Jonathan; Li, Chihua; Guzman, Jason T; Kornhauser, Zachary G; Keyes, Katherine M; Martins, Silvia S

    2018-04-02

    Although the flipped classroom model has been widely adopted in medical education, reports on its use in graduate-level public health programs are limited. This study describes the design, implementation, and evaluation of a flipped classroom redesign of an introductory epidemiology course and compares it to a traditional model. One hundred fifty Masters-level students enrolled in an introductory epidemiology course with a traditional format (in-person lecture and discussion section, at-home assignment; 2015, N = 72) and a flipped classroom format (at-home lecture, in-person discussion section and assignment; 2016, N = 78). Using mixed methods, we compared student characteristics, examination scores, and end-of-course evaluations of the 2016 flipped classroom format and the 2015 traditional format. Data on the flipped classroom format, including pre- and post-course surveys, open-ended questions, self-reports of section leader teaching practices, and classroom observations, were evaluated. There were no statistically significant differences in examination scores or students' assessment of the course between 2015 (traditional) and 2016 (flipped). In 2016, 57.1% (36) of respondents to the end-of-course evaluation found watching video lectures at home to have a positive impact on their time management. Open-ended survey responses indicated a number of strengths of the flipped classroom approach, including the freedom to watch pre-recorded lectures at any time and the ability of section leaders to clarify targeted concepts. Suggestions for improvement focused on ways to increase regular interaction with lecturers. There was no significant difference in students' performance on quantitative assessments comparing the traditional format to the flipped classroom format. The flipped format did allow for greater flexibility and applied learning opportunities at home and during discussion sections.

  1. Effect of Multiple Reflow Cycles and Al2O3 Nanoparticles Reinforcement on Performance of SAC305 Lead-Free Solder Alloy

    Science.gov (United States)

    Tikale, Sanjay; Prabhu, K. Narayan

    2018-05-01

    The effect of Al2O3 nanoparticles reinforcement on melting behavior, microstructure evolution at the interface and joint shear strength of 96.5Sn3Ag0.5Cu (SAC305) lead-free solder alloy subjected to multiple reflow cycles was investigated. The reinforced SAC305 solder alloy compositions were prepared by adding Al2O3 nanoparticles in different weight fractions (0.05, 0.1, 0.3 and 0.5 wt.%) through mechanical dispersion. Cu/solder/Cu micro-lap-shear solder joint specimens were used to assess the shear strength of the solder joint. Differential scanning calorimetry was used to investigate the melting behavior of SAC305 solder nanocomposites. The solder joint interfacial microstructure was studied using scanning electron microscopy. The results showed that the increase in melting temperature (T L) and melting temperature range of the SAC305 solder alloy by addition of Al2O3 nanoparticles were not significant. In comparison with unreinforced SAC305 solder alloy, the reinforcement of 0.05-0.5 wt.% of Al2O3 nanoparticles improved the solder wettability. The addition of nanoparticles in minor quantity effectively suppressed the Cu6Sn5 IMC growth, improved the solder joint shear strength and ductility under multiple reflow cycles. However, the improvement in solder properties was less pronounced on increasing the nanoparticle content above 0.1 wt.% of the solder alloy.

  2. Model studies of lipid flip-flop in membranes

    DEFF Research Database (Denmark)

    Parisio, Giulia; Ferrarini, Alberta; Sperotto, Maria Maddalena

    2016-01-01

    , and growth heavily depend. Such transverse motion—commonly called flip-flop—has been studied both experimentally and computationally. Experimental investigations face difficulties related to time-scales and probe-induced membrane perturbation issues. Molecular dynamics simulations play an important role...... for the molecular-level understanding of flip-flop. In this review we present a summary of the state of the art of computational studies of spontaneous flip-flop of phospholipids, sterols and fatty acids. Also, we highlight critical issues and strategies that have been developed to solve them, and what remains...

  3. Physical and transportation requirements for a FLIP fueled TRIGA

    International Nuclear Information System (INIS)

    Johnson, A.G.; Ringle, J.C.; Anderson, T.V.

    1977-01-01

    Several major changes to the OSTR Physical Security Plan were required by the NRC prior to the August 1976 receipt and installation of a new core consisting entirely of FLIP fuel. The general nature of these changes will be reviewed along with several decisions we faced during their implementation. At the previous TRIGA Owners' Conference in Salt Lake City, Utah, we reported on Oregon's regulatory program for research reactor emergency response planning and physical security. The latter program was of particular interest to us in light of the projected FLIP fuel shipments. The impact of the State's program for physical security of FLIP fuel during transportation will be presented. (author)

  4. Fitness Probability Distribution of Bit-Flip Mutation.

    Science.gov (United States)

    Chicano, Francisco; Sutton, Andrew M; Whitley, L Darrell; Alba, Enrique

    2015-01-01

    Bit-flip mutation is a common mutation operator for evolutionary algorithms applied to optimize functions over binary strings. In this paper, we develop results from the theory of landscapes and Krawtchouk polynomials to exactly compute the probability distribution of fitness values of a binary string undergoing uniform bit-flip mutation. We prove that this probability distribution can be expressed as a polynomial in p, the probability of flipping each bit. We analyze these polynomials and provide closed-form expressions for an easy linear problem (Onemax), and an NP-hard problem, MAX-SAT. We also discuss a connection of the results with runtime analysis.

  5. Integral Optimization of Systematic Parameters of Flip-Flow Screens

    Institute of Scientific and Technical Information of China (English)

    翟宏新

    2004-01-01

    The synthetic index Ks for evaluating flip-flow screens is proposed and systematically optimized in view of the whole system. A series of optimized values of relevant parameters are found and then compared with those of the current industrial specifications. The results show that the optimized value Ks approaches the one of those famous flip-flow screens in the world. Some new findings on geometric and kinematics parameters are useful for improving the flip-flow screens with a low Ks value, which is helpful in developing clean coal technology.

  6. Polarizing a stored proton beam by spin flip?

    International Nuclear Information System (INIS)

    Oellers, D.; Barion, L.; Barsov, S.; Bechstedt, U.; Benati, P.; Bertelli, S.; Chiladze, D.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P.F.; Dietrich, J.; Dolfus, N.; Dymov, S.; Engels, R.; Erven, W.; Garishvili, A.; Gebel, R.; Goslawski, P.

    2009-01-01

    We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin-flip cross section in low-energy electron-proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. The measured cross sections are too small for making spin flip a viable tool in polarizing a stored beam. This invalidates a recent proposal to use co-moving polarized positrons to polarize a stored antiproton beam.

  7. Research, Perspectives, and Recommendations on Implementing the Flipped Classroom.

    Science.gov (United States)

    Rotellar, Cristina; Cain, Jeff

    2016-03-25

    Flipped or inverted classrooms have become increasingly popular, and sometimes controversial, within higher education. Many educators have touted the potential benefits of this model and initial research regarding implementation has been primarily positive. The rationale behind the flipped classroom methodology is to increase student engagement with content, increase and improve faculty contact time with students, and enhance learning. This paper presents a summary of primary literature regarding flipped classrooms, discusses concerns and unanswered questions from both a student and faculty member perspective, and offers recommendations regarding implementation.

  8. Medicaid CHIP ESPC Database

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Environmental Scanning and Program Characteristic (ESPC) Database is in a Microsoft (MS) Access format and contains Medicaid and CHIP data, for the 50 states and...

  9. How Many Peripheral Solder Joints in a Surface Mounted Design Experience Inelastic Strains?

    Science.gov (United States)

    Suhir, E.; Yi, S.; Ghaffarian, R.

    2017-03-01

    It has been established that it is the peripheral solder joints that are the most vulnerable in the ball-grid-array (BGA) and column-grid-array (CGA) designs and most often fail. As far as the long-term reliability of a soldered microelectronics assembly as a whole is concerned, it makes a difference, if just one or more peripheral joints experience inelastic strains. It is clear that the low cycle fatigue lifetime of the solder system is inversely proportional to the number of joints that simultaneously experience inelastic strains. A simple and physically meaningful analytical expression (formula) is obtained for the prediction, at the design stage, of the number of such joints, if any, for the given effective thermal expansion (contraction) mismatch of the package and PCB; materials and geometrical characteristics of the package/PCB assembly; package size; and, of course, the level of the yield stress in the solder material. The suggested formula can be used to determine if the inelastic strains in the solder material could be avoided by the proper selection of the above characteristics and, if not, how many peripheral joints are expected to simultaneously experience inelastic strains. The general concept is illustrated by a numerical example carried out for a typical BGA package. The suggested analytical model (formula) is applicable to any soldered microelectronics assembly. The roles of other important factors, such as, e.g., solder material anisotropy, grain size, and their random orientation within a joint, are viewed in this analysis as less important factors than the level of the interfacial stress. The roles of these factors will be accounted for in future work and considered, in addition to the location of the joint, in a more complicated, more sophisticated, and more comprehensive reliability/fatigue model.

  10. Effect of gap distance on tensile strength of preceramic base metal solder joints.

    Science.gov (United States)

    Fattahi, Farnaz; Motamedi, Milad

    2011-01-01

    In order to fabricate prostheses with high accuracy and durability, soldering techniques have been introduced to clinical dentistry. However, these prostheses always fail at their solder joints. The purpose of this study was to evaluate the effect of gap distance on the tensile strength of base metal solder joints. Based on ADA/ISO 9693 specifications for tensile test, 40 specimens were fabricated from a Ni-Cr alloy and cut at the midpoint of 3-mm diameter bar and placed at desired positions by a specially designed device. The specimens were divided into four groups of 10 samples according to the desired solder gap distance: Group1: 0.1mm; Group2: 0.25mm; Group3: 0.5mm; and Group4: 0.75mm. After soldering, specimens were tested for tensile strength by a universal testing machine at a cross-head speed of 0.5mm/min with a preload of 10N. The mean tensile strength values of the groups were 162, 307.8, 206.1 and 336.7 MPa, respectively. The group with 0.75-mm gap had the highest and the group with 0.1-mm gap had the lowest tensile strength. Bonferroni test showed that Group1 and Group4 had statistically different values (P=0.023), but the differences between other groups were not sig-nificant at a significance level of 0.05. There was no direct relationship between increasing soldering gap distance and tensile strength of the solder joints.

  11. The critical oxide thickness for Pb-free reflow soldering on Cu substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chung, C. Key [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan (China); Assembly Test Global Materials, Intel Microelectronics Asia Ltd, B1, No. 205, Tun-Hwa North Road, 10595 Taipei, Taiwan (China); Chen, Y.J.; Li, C.C. [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan (China); Kao, C.R., E-mail: crkao@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan (China)

    2012-06-01

    Oxidation is an undesirable effect of reflow soldering. Non-wetting occurs when the oxide layer grows above the critical thickness. Characterizing the critical oxide thickness for soldering is challenging due to oxide's nano-scale thickness and irregular topographic surface. In this paper, the critical copper oxide thickness was characterized by Time-of-Flight Secondary Ion Mass Spectrometry, Scanning Electron Microscopy, Energy-Dispersive X-ray spectroscopy, and Transmission Electron Microscopy. Copper substrates were coated with an Organic-Solderable-Preservative (OSP) layer and baked at 150 Degree-Sign C and 85% Relative Humidity for different amounts of time. The onset of the non-wetting phenomenon occurred when the oxide thickness reached 18 {+-} 5 nm. As the oxide grew beyond this critical thickness, the percentage of non-wetting solder joint increased exponentially. The growth of the oxide thickness followed a parabolic rate law. The rate constant of oxidation was 0.6 Multiplication-Sign 10{sup -15} cm{sup 2} min{sup -1}. Oxidation resulted from interdiffusion of copper and oxygen atoms through the OSP and oxide layers. The oxidation mechanism will be presented and discussed. - Highlights: Black-Right-Pointing-Pointer Critical oxide thickness for Pb free solder on Cu substrate is 18 {+-} 5 nm. Black-Right-Pointing-Pointer Above the critical oxide, non-wet solder joint increases exponentially. Black-Right-Pointing-Pointer A maximum 13-nm oxide thickness is suggested for good solder joint. Black-Right-Pointing-Pointer Initial growth of oxide thickness is logarithmic and then parabolic after 12 nm. Black-Right-Pointing-Pointer Thick oxide (360-560 nm) is formed as pores shorten the oxidation path.

  12. Flipped cryptons and ultrahigh energy cosmic rays

    CERN Document Server

    Ellis, Jonathan Richard; Nanopoulos, D V

    2004-01-01

    Cryptons are metastable bound states of fractionally-charged particles that arise generically in the hidden sectors of models derived from heterotic string. We study their properties and decay modes in a specific flipped SU(5) model with long-lived four-particle spin-zero bound states called tetrons. We show that the neutral tetrons are metastable, and exhibit the tenth order nonrenormalizable superpotential operators responsible for their dominant decays. By analogy with QCD, we expect charged tetrons to be somewhat heavier, and to decay relatively rapidly via lower-order interactions that we also exhibit. The expected masses and lifetimes of the neutral tetrons make them good candidates for cold dark matter, and a potential source of the ultrahigh energy cosmic rays which have been observed, whereas the charged tetrons would have decayed in the early Universe.

  13. Bridging the gap with flipped classroom

    DEFF Research Database (Denmark)

    Selberg, Hanne; Topperzer, Martha

    the theoretical knowledge acquired during the course to their participation in the simulations. It is of pivotal importance that all students obtain hands-on experience during the sessions to reduce the theory-practice gap. The ongoing study has been pilot tested during three courses with participation of 90......Bridging the gap with flipped classroom Hanne Selberg, Metropolitan University College, Copenhagen, Martha Topperzer, University Hospital Rigshospitalet, Copenhagen, Denmark Background and aims Consistent with the strategy of increasing digitization and learner-centred teaching models....... The debriefing allows for students to reflect on how they applied their knowledge in the concrete patient situation which in turn promotes a positive learning experience. The learning objectives encompass both hands-on technical skills and non-technical communication skills enabling students to apply...

  14. Bit-commitment-based quantum coin flipping

    International Nuclear Information System (INIS)

    Nayak, Ashwin; Shor, Peter

    2003-01-01

    In this paper we focus on a special framework for quantum coin-flipping protocols, bit-commitment-based protocols, within which almost all known protocols fit. We show a lower bound of 1/16 for the bias in any such protocol. We also analyze a sequence of multiround protocols that tries to overcome the drawbacks of the previously proposed protocols in order to lower the bias. We show an intricate cheating strategy for this sequence, which leads to a bias of 1/4. This indicates that a bias of 1/4 might be optimal in such protocols, and also demonstrates that a more clever proof technique may be required to show this optimality

  15. Al and Si Alloying Effect on Solder Joint Reliability in Sn-0.5Cu for Automotive Electronics

    Science.gov (United States)

    Hong, Won Sik; Oh, Chulmin; Kim, Mi-Song; Lee, Young Woo; Kim, Hui Joong; Hong, Sung Jae; Moon, Jeong Tak

    2016-12-01

    To suppress the bonding strength degradation of solder joints in automotive electronics, we proposed a mid-temperature quaternary Pb-free Sn-0.5Cu solder alloy with minor Pd, Al, Si and Ge alloying elements. We manufactured powders and solder pastes of Sn-0.5Cu-(0.01,0.03)Al-0.005Si-(0.006-0.007)Ge alloys ( T m = 230°C), and vehicle electronic control units used for a flame-retardant-4 printed circuit board with an organic solderability preservative finish were assembled by a reflow soldering process. To investigate the degradation properties of solder joints used in engine compartments, thermal cycling tests were conducted from -40°C to 125°C (10 min dwell) for 1500 cycles. We also measured the shear strength of the solder joints in various components and observed the microstructural evolution of the solder joints. Based on these results, intermetallic compound (IMC) growth at the solder joints was suppressed by minor Pd, Al and Si additions to the Sn-0.5Cu alloy. After 1500 thermal cycles, IMC layers thicknesses for 100 parts per million (ppm) and 300 ppm Al alloy additions were 6.7 μm and 10 μm, compared to the as-reflowed bonding thicknesses of 6 μm and 7 μm, respectively. Furthermore, shear strength degradation rates for 100 ppm and 300 ppm Al(Si) alloy additions were at least 19.5%-26.2%. The cause of the improvement in thermal cycling reliability was analyzed using the (Al,Cu)-Sn, Si-Sn and Al-Sn phases dispersed around the Cu6Sn5 intermetallic at the solder matrix and bonding interfaces. From these results, we propose the possibility of a mid-temperature Sn-0.5Cu(Pd)-Al(Si)-Ge Pb-free solder for automotive engine compartment electronics.

  16. Spin Flipping in the Presence of a Full Siberian Snake

    International Nuclear Information System (INIS)

    Blinov, B.B.; Anferov, V.A.; Derbenev, Y.S.; Kageya, T.; Krisch, A.D.; Lorenzon, W.; Ratner, L.G.; Sivers, D.W.; Sourkont, K.V.; Wong, V.K.; Chu, C.M.; Lee, S.Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Przewoski, B. von; Sato, H.

    1998-01-01

    We have demonstrated for the first time spin flipping of a polarized proton beam stored in a ring containing a nearly 100% Siberian snake; we did this using a 'snake' depolarizing resonance induced by an rf solenoid magnet. By varying the rf solenoid close-quote s ramp time, frequency range, and voltage, we reached a spin-flip efficiency of about 91% . This spin-flip efficiency was probably reduced because the horizontal stable spin direction was not perpendicular to the longitudinal field of the rf solenoid, and was possibly reduced by nearby synchrotron sideband resonances. The planned use of a vertical rf dipole may improve the spin-flip efficiency. copyright 1998 The American Physical Society

  17. PENGARUH FLIPPED MASTERY CLASSROM TERHADAP PEROLEHAN HASIL BELAJAR KOGNITIF MAHASISWA

    Directory of Open Access Journals (Sweden)

    Muhammad Ridha

    2016-04-01

    Tujuan dari penelitian ini adalah untuk mengetahui pengaruh penerapan strategi flipped mastery classroom terhadap perolehan hasil belajar kognitif mahasiswa pada matakuliah psikologi pendidikan. Subjek dalam penelitian ini adalah mahasiswa Jurusan Teknologi Pendidikan Universitas Negeri Malang semester genap tahun ajaran 2015/2016 pada kelas utuh. Kelas eksperimen dibelajarkan dengan strategi flipped-mastery classroom dan kelas kontrol dibelajarkan dengan strategi tradisional.  Penelitian ini menggunakan rancangan kuasi eksperimen Non Equivalent Control Group Design. Hasil penelitian menunjukkan bahwa penerapan strategi flipped mastery classroom memberikan pengaruh positif terhadap perolehan hasil belajar kognitif mahasiswa. Perolehan hasil belajar kognitif mahasiswa yang dibelajarkan dengan strategi flipped-mastery lebih tinggi secara signifikan dari pada perolehan hasil belajar mahasiswa yang dibelajarkan dengan strategi tradisional.

  18. What millennial medical students say about flipped learning

    Science.gov (United States)

    Pettit, Robin K; McCoy, Lise; Kinney, Marjorie

    2017-01-01

    Flipped instruction is gaining popularity in medical schools, but there are unanswered questions such as the optimum amount of the curriculum to flip and whether flipped sessions should be mandatory. We were in a unique position to evaluate feedback from first-year medical students who had experienced both flipped and lecture-based courses during their first semester of medical school. A key finding was that the students preferred a variety of different learning formats over an “all or nothing” learning format. Learning format preferences did not necessarily align with perceptions of which format led to better course exam performance. Nearly 70% of respondents wanted to make their own decisions regarding attendance. Candid responses to open-ended survey prompts reflected millennial preferences for choice, flexibility, efficiency, and the ability to control the pace of their learning, providing insight to guide curricular improvements. PMID:28769600

  19. What millennial medical students say about flipped learning.

    Science.gov (United States)

    Pettit, Robin K; McCoy, Lise; Kinney, Marjorie

    2017-01-01

    Flipped instruction is gaining popularity in medical schools, but there are unanswered questions such as the optimum amount of the curriculum to flip and whether flipped sessions should be mandatory. We were in a unique position to evaluate feedback from first-year medical students who had experienced both flipped and lecture-based courses during their first semester of medical school. A key finding was that the students preferred a variety of different learning formats over an "all or nothing" learning format. Learning format preferences did not necessarily align with perceptions of which format led to better course exam performance. Nearly 70% of respondents wanted to make their own decisions regarding attendance. Candid responses to open-ended survey prompts reflected millennial preferences for choice, flexibility, efficiency, and the ability to control the pace of their learning, providing insight to guide curricular improvements.

  20. How the flip target behaves in four-dimensional space

    International Nuclear Information System (INIS)

    Antillon, A.; Kats, J.

    1985-01-01

    We use available coupling theory for understanding how a flip target in a 4-dimensional phase space reduces a gaussian beam of particles. Experimental evidence at the AGS can be qualitatively explained by this theory

  1. Step to improve neural cryptography against flipping attacks.

    Science.gov (United States)

    Zhou, Jiantao; Xu, Qinzhen; Pei, Wenjiang; He, Zhenya; Szu, Harold

    2004-12-01

    Synchronization of neural networks by mutual learning has been demonstrated to be possible for constructing key exchange protocol over public channel. However, the neural cryptography schemes presented so far are not the securest under regular flipping attack (RFA) and are completely insecure under majority flipping attack (MFA). We propose a scheme by splitting the mutual information and the training process to improve the security of neural cryptosystem against flipping attacks. Both analytical and simulation results show that the success probability of RFA on the proposed scheme can be decreased to the level of brute force attack (BFA) and the success probability of MFA still decays exponentially with the weights' level L. The synchronization time of the parties also remains polynomial with L. Moreover, we analyze the security under an advanced flipping attack.

  2. Flipped classroom model for learning evidence-based medicine.

    Science.gov (United States)

    Rucker, Sydney Y; Ozdogan, Zulfukar; Al Achkar, Morhaf

    2017-01-01

    Journal club (JC), as a pedagogical strategy, has long been used in graduate medical education (GME). As evidence-based medicine (EBM) becomes a mainstay in GME, traditional models of JC present a number of insufficiencies and call for novel models of instruction. A flipped classroom model appears to be an ideal strategy to meet the demands to connect evidence to practice while creating engaged, culturally competent, and technologically literate physicians. In this article, we describe a novel model of flipped classroom in JC. We present the flow of learning activities during the online and face-to-face instruction, and then we highlight specific considerations for implementing a flipped classroom model. We show that implementing a flipped classroom model to teach EBM in a residency program not only is possible but also may constitute improved learning opportunity for residents. Follow-up work is needed to evaluate the effectiveness of this model on both learning and clinical practice.

  3. Online Learning Room for ”Flipped Classroom”

    DEFF Research Database (Denmark)

    Bugge, Ellen Margrethe; Nielsen, Linda Susanna Hauschildt

    2014-01-01

    working actively and innovatively to create a didactic design in our online learning rooms in our LMS that satisfy the demands for flipped learning and at the same time adapted to the special needs of each learning module at the nursing education programme. Keywords: Online learning, flipped classroom......Abstract The “flipped classroom” learning concept is an alternative way of teaching & learning. The fundamental idea of the "flipped classroom" is to change the way students prepare for classes and the work that takes place when the students are together in the classroom. This integrates online...... learning with learning in the classroom. The learning room must support the students’ unassisted learning, their preparation for class and their preparation for supervision in both a motivating and clear way. At the Nursing Education Programme at University College Lillebaelt in Denmark, we have been...

  4. An evaluation of flipped e-learning experiences.

    Science.gov (United States)

    Jones-Bonofiglio, Kristen Dawn; Willett, Timothy; Ng, Stella

    2017-12-22

    The "flipped" classroom is an educational strategy gaining popularity for its growing evidence base that suggests it may successfully improve learning outcomes. Also known as reverse instruction, this approach has been typically implemented and studied in in-person post-secondary settings. The utilization of a flipped approach in the healthcare education literature has been examined in a wide range of contexts, but little has been written regarding continuing professional development (CPD). Therefore, with success in other contexts there is potential for the flipped classroom approach to enhance student satisfaction, learner engagement, and learning outcomes in the context of online education for CPD. In this paper, we describe the structure and format of such a course using a qualitative case study framework. This study contributes to a more comprehensive understanding of effective ways of overcoming distributed learning challenges in online CPD using a flipped approach.

  5. Teachers' development and reflection in the flipped classroom

    DEFF Research Database (Denmark)

    Triantafyllou, Evangelia; Timcenko, Olga; Kofoed, Lise

    2017-01-01

    The flipped classroom is an instruction method that has gained momentum during the last years due to technological advances allowing the online sharing of teaching material and learning activities. Bishop and Verleger defined the flipped classroom as “...an educational technique that consists...... of two parts: interactive group learning activities inside the classroom, and direct computer-based individual instruction outside the classroom” (Bishop & Verleger, 2013). So far, research on flipped classroom has mostly concentrated on student perceptions, engagement and achievement level, e...... course in order to adjust it to the flipped classroom model. We have also seen that these considerations have forced teachers to also reconsider the learning objectives of specific activities. Another aspect that promoted reflection was the production of video lectures. Finally, teachers reflected...

  6. Thermally excited proton spin-flip laser emission in tokamaks

    International Nuclear Information System (INIS)

    Arunasalam, V.; Greene, G.J.

    1993-07-01

    Based on statistical thermodynamic fluctuation arguments, it is shown here for the first time that thermally excited spin-flip laser emission from the fusion product protons can occur in large tokamak devices that are entering the reactor regime of operation. Existing experimental data from TFTR supports this conjecture, in the sense that these measurements are in complete agreement with the predictions of the quasilinear theory of the spin-flip laser

  7. Quantum protocol for cheat-sensitive weak coin flipping.

    Science.gov (United States)

    Spekkens, R W; Rudolph, Terry

    2002-11-25

    We present a quantum protocol for the task of weak coin flipping. We find that, for one choice of parameters in the protocol, the maximum probability of a dishonest party winning the coin flip if the other party is honest is 1/sqrt[2]. We also show that if parties restrict themselves to strategies wherein they cannot be caught cheating, their maximum probability of winning can be even smaller. As such, the protocol offers additional security in the form of cheat sensitivity.

  8. The Implementation of A Flipped Classroom in Foreign Language Teaching

    Directory of Open Access Journals (Sweden)

    Ahmet BASAL

    2015-10-01

    Full Text Available Alongside the rise of educational technology, many teachers have been taking gradual but innovative steps to redesign their teaching methods. For example, in flipped learning or a flipped classroom, students watch instructional videos outside the classroom and do assignments or engage in activities inside the classroom. Language teachers are one group of educators exploring the flipped classroom. In foreign language classes, such an approach may offer great benefits for both the teachers and students since classroom time can be applied to more interactive tasks. By extending classroom hours in this way, language teachers can focus on successfully addressing all subjects in the curriculum. The aim of this study is (a to gain insights into the perceptions of prospective English language teachers at a state university in Turkey on flipped classrooms and (b to introduce the implementation of a flipped classroom into an English language class. A total of 47 prospective English teachers participated in the study. Qualitative research design was used and data were collected via an open-ended question. Findings of the study indicated that pre-service English teachers had positive perceptions towards the use of the flipped classroom as an integral part of face-to-face courses. It can be concluded that flipped classroom was beneficial in terms of 4 categories based on the content analysis of the responses: learning at one’s own pace, advance student preparation, overcoming the limitations of class time, increasing the participation in the classroom. The study also provides recommendations towards LMS integration into courses in other English language teaching departments and for implementing flipped classrooms in language teaching.

  9. Chemical wiring and soldering toward all-molecule electronic circuitry.

    Science.gov (United States)

    Okawa, Yuji; Mandal, Swapan K; Hu, Chunping; Tateyama, Yoshitaka; Goedecker, Stefan; Tsukamoto, Shigeru; Hasegawa, Tsuyoshi; Gimzewski, James K; Aono, Masakazu

    2011-06-01

    Key to single-molecule electronics is connecting functional molecules to each other using conductive nanowires. This involves two issues: how to create conductive nanowires at designated positions, and how to ensure chemical bonding between the nanowires and functional molecules. Here, we present a novel method that solves both issues. Relevant functional molecules are placed on a self-assembled monolayer of diacetylene compound. A probe tip of a scanning tunneling microscope is then positioned on the molecular row of the diacetylene compound to which the functional molecule is adsorbed, and a conductive polydiacetylene nanowire is fabricated by initiating chain polymerization by stimulation with the tip. Since the front edge of chain polymerization necessarily has a reactive chemical species, the created polymer nanowire forms chemical bonding with an encountered molecular element. We name this spontaneous reaction "chemical soldering". First-principles theoretical calculations are used to investigate the structures and electronic properties of the connection. We demonstrate that two conductive polymer nanowires are connected to a single phthalocyanine molecule. A resonant tunneling diode formed by this method is discussed. © 2011 American Chemical Society

  10. Control of phospholipid flip-flop by transmembrane peptides

    International Nuclear Information System (INIS)

    Kaihara, Masanori; Nakao, Hiroyuki; Yokoyama, Hirokazu; Endo, Hitoshi; Ishihama, Yasushi; Handa, Tetsurou; Nakano, Minoru

    2013-01-01

    Highlights: ► Phospholipid flip-flop in transmembrane peptide-containing vesicles was investigated. ► Peptides that contained polar residues in the center of the transmembrane region promoted phospholipid flip-flop. ► A bioinformatics approach revealed the presence of polar residues in the transmembrane region of ER membrane proteins. ► Polar residues in ER membrane proteins possibly provide flippase-like activity. - Abstract: We designed three types of transmembrane model peptides whose sequence originates from a frequently used model peptide KALP23, and we investigated their effects on phospholipid flip-flop. Time-resolved small-angle neutron scattering and a dithionite fluorescent quenching assay demonstrated that TMP-L, which has a fully hydrophobic transmembrane region, did not enhance phospholipid flip-flop, whereas TMP-K and TMP-E, which have Lys and Glu, respectively, in the center of their transmembrane regions, enhanced phospholipid flip-flop. Introduction of polar residues in the membrane-spanning helices is considered to produce a locally polar region and enable the lipid head group to interact with the polar side-chain inside the bilayers, thereby reducing the activation energy for the flip-flop. A bioinformatics approach revealed that acidic and basic residues account for 4.5% of the central region of the transmembrane domain in human ER membrane proteins. Therefore, polar residues in ER membrane proteins are considered to provide flippase-like activity

  11. Study and practice of flipped classroom in optoelectronic technology curriculum

    Science.gov (United States)

    Shi, Jianhua; Lei, Bing; Liu, Wei; Yao, Tianfu; Jiang, Wenjie

    2017-08-01

    "Flipped Classroom" is one of the most popular teaching models, and has been applied in more and more curriculums. It is totally different from the traditional teaching model. In the "Flipped Classroom" model, the students should watch the teaching video afterschool, and in the classroom only the discussion is proceeded to improve the students' comprehension. In this presentation, "Flipped Classroom" was studied and practiced in opto-electronic technology curriculum; its effect was analyzed by comparing it with the traditional teaching model. Based on extensive and deep investigation, the phylogeny, the characters and the important processes of "Flipped Classroom" are studied. The differences between the "Flipped Classroom" and the traditional teaching model are demonstrated. Then "Flipped Classroom" was practiced in opto-electronic technology curriculum. In order to obtain high effectiveness, a lot of teaching resources were prepared, such as the high-quality teaching video, the animations and the virtual experiments, the questions that the students should finish before and discussed in the class, etc. At last, the teaching effect was evaluated through analyzing the result of the examination and the students' surveys.

  12. Flipped Classroom as an Alternative Strategy for Teaching Stoichiometry

    Directory of Open Access Journals (Sweden)

    Norrie E. Gayeta

    2017-11-01

    Full Text Available This study aimed to compare the effectiveness of flipped classroom and traditional classroom instruction in measuring conceptual change and to determine if flipped classroom instruction would be an alternative method of teaching to traditional lecture method. This study covered the level of conceptual understanding of students on stoichiometry and the type of conceptual change before and after exposure to flipped and traditional classroom environment. Qualitative and quantitative research methods were used in the study. Respondents were two sections of third year Bachelor of Secondary Education, Biological Science. Frequency, percentage, ranking, mean, standard deviation, Hake factor test, and t-test were the statistical tools applied to answer specific questions. Results showed profound increase towards conceptual change representing a shift from intuitive understanding to correct incomplete understanding level. Thus, change for the better, in theoretical type was determined from pretest to posttest of students exposed to flipped and traditional classroom. Results also indicated that there is no significant difference on students’ conceptual change on stoichiometry exposed to flipped and traditional classroom environment thus, flipped classroom instruction can be used as an alternative teaching method to traditional lecture method in teaching stoichiometry

  13. Improvement of the auto wire feeder machine in a de-soldering process

    Directory of Open Access Journals (Sweden)

    Niramon Nonkhukhetkhong

    2016-10-01

    Full Text Available This paper presents the methodology of the de-soldering process for rework of disk drive Head Stack Assembly (HSA units. The auto wire feeder is a machine that generates Tin (Sn on the product. This machine was determined to be one of the major sources of excess Sn on the HSA. The defect rate due to excess Sn is more than 30%, which leads to increased processing time and cost to perform additional cleaning steps. From process analysis, the major causes of excess Sn are as follows: 1 The machine cannot cut the wire all the way into the flux core area; 2 The sizes and types of soldering irons are not appropriate for the unit parts; and, 3 There are variations introduced into the de-soldering process by the workforce. This paper proposes a methodology to address all three of these causes. First, the auto wire feeder machine in the de-solder process will be adjusted in order to cut wires into flux core. Second, the types of equipment and material used in de-soldering will be optimized. Finally, a new standard method for operators, which can be controlled more easily, will be developed in order to reduce defects due to workforce related variation. After these process controls and machine adjustments were implemented, the overall Sn related problems were significantly improved. Sn contamination was reduced by 41% and cycle time was reduced by an average of 15 seconds.

  14. In vitro conjunctival incision repair by temperature-controlled laser soldering.

    Science.gov (United States)

    Norman, Galia; Rabi, Yaron; Assia, Ehud; Katzir, Abraham

    2009-01-01

    The common method of closing conjunctival incisions is by suturing, which is associated with several disadvantages. It requires skill to apply and does not always provide a watertight closure, which is required in some operations (e.g., glaucoma filtration). The purpose of the present study was to evaluate laser soldering as an alternative method for closing conjunctival incisions. Conjunctival incisions of 20 ex vivo porcine eyes were laser soldered using a temperature-controlled fiberoptic laser system and an albumin mixed with indocyanine green as a solder. The control group consisted of five repaired incisions by a 10-0 nylon running suture. The leak pressure of the repaired incisions was measured. The mean leak pressure in the laser-soldered group was 132 mm Hg compared to 4 mm Hg in the sutured group. There was no statistically significant difference in both the incision's length and distance from the limbus between the groups, before and after the procedure, indicating that there was no severe thermal damage. These preliminary results clearly demonstrate that laser soldering may be a useful method for achieving an immediate watertight conjunctival wound closure. This procedure is faster and easier to apply than suturing.

  15. Fundamentals of lead-free solder interconnect technology from microstructures to reliability

    CERN Document Server

    Lee, Tae-Kyu; Kim, Choong-Un; Ma, Hongtao

    2015-01-01

    This unique book provides an up-to-date overview of the fundamental concepts behind lead-free solder and interconnection technology. Readers will find a description of the rapidly increasing presence of electronic systems in all aspects of modern life as well as the increasing need for predictable reliability in electronic systems. The physical and mechanical properties of lead-free solders are examined in detail, and building on fundamental science, the mechanisms responsible for damage and failure evolution, which affect reliability of lead-free solder joints are identified based on microstructure evolution.  The continuing miniaturization of electronic systems will increase the demand on the performance of solder joints, which will require new alloy and processing strategies as well as interconnection design strategies. This book provides a foundation on which improved performance and new design approaches can be based.  In summary, this book:  Provides an up-to-date overview on lead-free soldering tech...

  16. Effect of temperature and flux concentration on soldering of base metal.

    Science.gov (United States)

    Lee, S Y; Lin, C T; Wang, M H; Tseng, H; Huang, H M; Dong, D R; Pan, L C; Shih, Y H

    2000-12-01

    The present study used the acoustic emission (AE) technique to evaluate interactions among soldering temperature, flux treatment, and the resultant ultimate tensile strength (UTS). Scanning electron microscopy (SEM) was used to examine fracture surfaces of the solder joints. Specimens were cast from removable partial denture alloy and then placed in a jig with a gap distance of 1.0 mm. A high-frequency soldering machine with an optical pyrometer was used for soldering at 1150 degrees C and 1200 degrees C, respectively. The flux concentrations were 67% and 75%. The soldered specimens were subjected to tensile test at a crosshead speed of 0.05 mm/min. During testing, acoustic emissions in the frequency range of 100--1200 kHz were collected, filtered, recorded, and processed by a sensing device. The results were analysed by ANOVA and Tukey LSD test. UTS at different temperatures showed no significant difference according to either mechanical or acoustic results. But in the 1200 degrees C group, the UTSs and AE counts showed significant differences (Pacoustic signals within the elastic deformation zone, while the 67% flux subgroup produced similar signals within the plastic deformation zone, either beyond the 0.2% yield point or before fracture.

  17. Nano-soldering of magnetically aligned three-dimensional nanowire networks

    International Nuclear Information System (INIS)

    Gao Fan; Gu Zhiyong

    2010-01-01

    It is extremely challenging to fabricate 3D integrated nanostructures and hybrid nanoelectronic devices. In this paper, we report a simple and efficient method to simultaneously assemble and solder nanowires into ordered 3D and electrically conductive nanowire networks. Nano-solders such as tin were fabricated onto both ends of multi-segmented nanowires by a template-assisted electrodeposition method. These nanowires were then self-assembled and soldered into large-scale 3D network structures by magnetic field assisted assembly in a liquid medium with a high boiling point. The formation of junctions/interconnects between the nanowires and the scale of the assembly were dependent on the solder reflow temperature and the strength of the magnetic field. The size of the assembled nanowire networks ranged from tens of microns to millimeters. The electrical characteristics of the 3D nanowire networks were measured by regular current-voltage (I-V) measurements using a probe station with micropositioners. Nano-solders, when combined with assembling techniques, can be used to efficiently connect and join nanowires with low contact resistance, which are very well suited for sensor integration as well as nanoelectronic device fabrication.

  18. Effects of Fe2NiO4 nanoparticles addition into lead free Sn–3.0Ag–0.5Cu solder pastes on microstructure and mechanical properties after reflow soldering process

    International Nuclear Information System (INIS)

    Chellvarajoo, Srivalli; Abdullah, M.Z.; Samsudin, Z.

    2015-01-01

    Highlights: • Fe 2 NiO 4 nanoparticles added into SAC 305 by mechanical mixing to form nanocomposite solder paste. • Nanoparticles in the composite solder travels with flux to the outermost surface after reflow. • The intermetallics compound reduced with the addition of nanoparticles into solder paste. • The hardness increased with the addition of limited percentage of nanoparticles into SAC 305. - Abstract: This study investigates the effects of the addition of Fe 2 NiO 4 nanoparticles into a SAC-305 lead-free solder paste. Iron, nickel, and oxide nano-elements were mixed with Pb-free solder alloying elements to produce a new form of nanocomposite solder paste, which can be a promising material in electronic packaging. The SAC-305 was mechanically added with 0.5, 1.5, and 2.5 wt.% of Fe 2 NiO 4 nanoparticles. The migration of nanoparticles in the nanocomposite solder paste to the outermost surface was clarified using the copper ‘sandwich’ method, which was performed after the reflow soldering process. Varying amounts of nanoparticles in the SAC-305 affected the IMC thickness and mechanical properties of the nanocomposite solder paste. The IMC thickness was reduced by 29.15%, 42.37%, and 59.00% after adding 0.5, 1.5, and 2.5 wt.% of Fe 2 NiO 4 nanoparticles in the SAC-305, respectively. However, via nanoindentation method, the hardness of the nanocomposite solder was improved by 44.07% and 56.82% after adding 0.5 and 1.5 wt.% of Fe 2 NiO 4 nanoparticles, respectively. If the addition of Fe 2 NiO 4 nanoparticle exceeded 1.5 wt.%, the hardness increased infinitely

  19. High performance low cost interconnections for flip chip attachment with electrically conductive adhesive. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-05-01

    This final report is a compilation of final reports from each of the groups participating in the program. The main three groups involved in this effort are the Thomas J. Watson Research Center of IBM Corporation in Yorktown Heights, New York, Assembly Process Design of IBM Corporation in Endicott, New York, and SMT Laboratory of Universal Instruments Corporation in Binghamton, New York. The group at the research center focused on the conductive adhesive materials development and characterization. The group in process development focused on processing of the Polymer-Metal-Solvent Paste (PMSP) to form conductive adhesive bumps, formation of the Polymer-Metal Composite (PMC) on semiconductor devices and study of the bonding process to circuitized organic carriers, and the long term durability and reliability of joints formed using the process. The group at Universal Instruments focused on development of an equipment set and bonding parameters for the equipment to produce bond assembly tooling. Reports of each of these individual groups are presented here reviewing their technical efforts and achievements.

  20. A new functional and structural generation of JK edge-triggered flip-flops

    International Nuclear Information System (INIS)

    Stefanescu, I.

    1977-01-01

    A new type of logical structure for a JK edge-triggered flip-flop is proposed by the author. The structure facilitates flip-flop realizations, named ''jk-JK edge-triggered flip-flops'', satisfying more functional requirements, and offering an increased flexibility in logical design, with respect to the conventional JK edge-triggered flip-flops. The function of new flip-flops covers the function of JK edge-triggered flip-flops, known as integrated circuits. (author)

  1. Reliability of Pb free solder alloys. Physical and mechanical properties; Pb free handa no shinraisei. Butsuri kikaiteki shinraisei

    Energy Technology Data Exchange (ETDEWEB)

    Sanji, M; Yoshino, M; Ishikawa, J; Takenaka, O [Denso Corp., Aichi (Japan)

    1997-10-01

    Properties of 19 different Pb free solders have been evaluated in comparison with Sn-37Pb eutectic solder. Pb free solders without Bi were on the same level as Sn-37Pb in tensile strength and elongation, and those with Bi had higher strength and lower elongation than Sn-37Pb. As the Bi content increased, strength was higher, and elongation was lower. In torsion fatigue tests, fatigue life of Pb free solders without Bi was longer than Sn-37Pb. The relationships of Coffin-Manson rule and Basquin rule with fatigue life was applicable to Pb free solder. Fatigue life of those is inferred from their tensile strength. 7 refs., 13 figs., 1 tab.

  2. Price of forest chips decreasing

    International Nuclear Information System (INIS)

    Hakkila, P.

    2001-01-01

    Use of forest chips was studied in 1999 in the national Puuenergia (Wood Energy) research program. Wood combusting heating plants were questioned about are the main reasons restricting the increment of the use of forest chips. Heating plants, which did not use forest chips at all or which used less than 250 m 3 (625 bulk- m 3 ) in 1999 were excluded. The main restrictions for additional use of forest chips were: too high price of forest chips; lack of suppliers and/or uncertainty of deliveries; technical problems of reception and processing of forest chips; insufficiency of boiler output especially in winter; and unsatisfactory quality of chips. The price of forest chips becomes relatively high because wood biomass used for production of forest chips has to be collected from wide area. Heavy equipment has to be used even though small fragments of wood are processed, which increases the price of chips. It is essential for forest chips that the costs can be pressed down because competition with fossil fuels, peat and industrial wood residues is hard. Low market price leads to the situation in which forest owner gets no price of the raw material, the entrepreneurs operate at the limit of profitability and renovation of machinery is difficult, and forest chips suppliers have to sell the chips at prime costs. Price of forest chips has decreased significantly during the past decade. Nominal price of forest chips is now lower than two decades ago. The real price of chips has decreased even more than the nominal price, 35% during the past decade and 20% during the last five years. Chips, made of small diameter wood, are expensive because the price includes the felling costs and harvesting is carried out at thinning lots. Price is especially high if chips are made of delimbed small diameter wood due to increased the work and reduced amount of chips. The price of logging residue chips is most profitable because cutting does not cause additional costs. Recovery of chips is

  3. Optimal selection of TLD chips

    International Nuclear Information System (INIS)

    Phung, P.; Nicoll, J.J.; Edmonds, P.; Paris, M.; Thompson, C.

    1996-01-01

    Large sets of TLD chips are often used to measure beam dose characteristics in radiotherapy. A sorting method is presented to allow optimal selection of chips from a chosen set. This method considers the variation

  4. Design of Experiments to Determine Causes of Flex Cable Solder Wicking, Discoloration and Hole Location Defects

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, Larry

    2009-04-22

    Design of Experiments (DoE) were developed and performed in an effort to discover and resolve the causes of three different manufacturing issues; large panel voids after Hot Air Solder Leveling (HASL), cable hole locations out of tolerance after lamination and delamination/solder wicking around flat flex cable circuit lands after HASL. Results from a first DoE indicated large panel voids could be eliminated by removing the pre-HASL cleaning. It also revealed eliminating the pre-HASL bake would not be detrimental when using a hard press pad lamination stackup. A second DoE indicated a reduction in hard press pad stackup lamination pressure reduced panel stretch in the y axis approximately 70%. A third DoE illustrated increasing the pre-HASL bake temperature could reduce delamination/solder wicking when using a soft press pad lamination stackup.

  5. Corrosion Behaviour of Sn-based Lead-Free Solders in Acidic Solution

    Science.gov (United States)

    Nordarina, J.; Mohd, H. Z.; Ahmad, A. M.; Muhammad, F. M. N.

    2018-03-01

    The corrosion properties of Sn-9(5Al-Zn), Sn-Cu and SAC305 were studied via potentiodynamic polarization method in an acidic solution of 1 M hydrochloric acid (HCl). Sn-9(5Al-Zn) produced different polarization profile compared with Sn-Cu and SAC305. The morphological analysis showed that small, deep grooves shaped of corrosion product formed on top of Sn-9(5Al-Zn) solder while two distinctive structures of closely packed and loosely packed corrosion product formed on top of Sn-Cu and SAC305 solder alloys. Phase analysis revealed the formations of various corrosion products such as SnO and SnO2 mainly dominant on surface of solder alloys after potentiodynamic polarization in 1 M hydrochloric acid (HCl).

  6. Au-Ge based Candidate Alloys for High-Temperature Lead-Free Solder Alternatives

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Hattel, Jesper Henri

    2009-01-01

    Au-Ge based candidate alloys have been proposed as an alternative to high-lead content solders that are currently being used for high-temperature applications. The influence of the low melting point metals namely In, Sb and Sn to the Au-Ge eutectic with respect to the microstructure and microhard......Au-Ge based candidate alloys have been proposed as an alternative to high-lead content solders that are currently being used for high-temperature applications. The influence of the low melting point metals namely In, Sb and Sn to the Au-Ge eutectic with respect to the microstructure...... was primarily strengthened by the refined (Ge) dispersed phase. The distribution of phases played a relatively more crucial role in determining the ductility of the bulk solder alloy. In the present work it was found that among the low melting point metals, the addition of Sb to the Au-Ge eutectic would...

  7. Dissolution ad uptake of cadmium from dental gold solder alloy implants

    International Nuclear Information System (INIS)

    Bergman, B.; Bergman, M.; Soeremark, R.

    1977-01-01

    Pure metallic cadmium was irradiated by means of thermal neutrons. The irradiated cadmium ( 115 Cd) was placed in bags of gold foil and the bags were implanted subcutaneously in the neck region of mice. Two and 3 d respectively after implantation the mice were killed, the bags removed and the animals subjected to whole-body autoradiography. The autoradiograms revealed an uptake of 115 Cd in liver and kidney. In another experiment specimens of a cadmium-containing dental gold solder alloy, a cadmium-free dental casting gold alloy and soldered assemblies made of these two alloys were implanted subcutaneously in the neck region of mice. The animals were killed after 6 months; cadmium analysis showed significant increases in the cadmium concentration in liver and kidney of those mice which had been given implants of gold solder alloy. The study clearly shows that due to electrochemical corrosion cadmium can be released from implants and accumulated in the kidneys and the liver. (author)

  8. SINGLE IMAGE CAMERA CALIBRATION IN CLOSE RANGE PHOTOGRAMMETRY FOR SOLDER JOINT ANALYSIS

    Directory of Open Access Journals (Sweden)

    D. Heinemann

    2016-06-01

    Full Text Available Printed Circuit Boards (PCB play an important role in the manufacturing of electronic devices. To ensure a correct function of the PCBs a certain amount of solder paste is needed during the placement of components. The aim of the current research is to develop an real-time, closed-loop solution for the analysis of the printing process where solder is printed onto PCBs. Close range photogrammetry allows for determination of the solder volume and a subsequent correction if necessary. Photogrammetry is an image based method for three dimensional reconstruction from two dimensional image data of an object. A precise camera calibration is indispensable for an accurate reconstruction. In our certain application it is not possible to use calibration methods with two dimensional calibration targets. Therefore a special calibration target was developed and manufactured, which allows for single image camera calibration.

  9. Comparison of implant-abutment interface misfits after casting and soldering procedures.

    Science.gov (United States)

    Neves, Flávio Domingues das; Elias, Gisele Araújo; da Silva-Neto, João Paulo; de Medeiros Dantas, Lucas Costa; da Mota, Adérito Soares; Neto, Alfredo Júlio Fernandes

    2014-04-01

    The aim of this study was to compare vertical and horizontal adjustments of castable abutments after conducting casting and soldering procedures. Twelve external hexagonal implants (3.75 × 10 mm) and their UCLA abutments were divided according their manufacturer and abutment type: PUN (plastic UCLA, Neodent), PUC (plastic UCLA, Conexão), PU3i (plastic UCLA, Biomet 3i), and PUTN (plastic UCLA with Tilite milled base, Neodent). Three infrastructures of a fixed partial implant-supported bridge with 3 elements were produced for each group. The measurements of vertical (VM) and horizontal (HM) misfits were obtained via scanning electron microscopy after completion of casting and soldering. The corresponding values were determined to be biomechanically acceptable to the system, and the results were rated as a percentage. Statistical analysis establishes differences between groups by chi-square after procedures, and McNeman's test was applied to analyze the influence of soldering over casting (α ≤ .05). For the values of VM and HM, respectively, when the casting process was complete, it was observed that 83.25% and 100% (PUTN), 33.3% and 27.75% (PUN), 33.3% and 88.8% (PUC), 33.3% and 94.35% (PU3i) represented acceptable values. After completing the requisite soldering, acceptable values were 50% and 94.35% (PUTN), 16.6% and 77.7% (PUN), 38.55% and 77.7% (PUC), and 27.75% and 94.35% (PU3i). Within the limitations of this study, it can be concluded that the premachined abutments presented more acceptable VM values. The HM values were within acceptable limits before and after the soldering procedure for most groups. Further, the soldering procedure resulted in an increase of VM in all groups.

  10. In-vitro Investigations of Skin Closure using Diode Laser and Protein Solder Containing Gold Nanoshells

    Directory of Open Access Journals (Sweden)

    Mohammad Sadegh Nourbakhsh

    2010-12-01

    Full Text Available Introduction: Laser tissue soldering is a new technique for repair of various tissues including the skin, liver, articular cartilage and nerves and is a promising alternative to suture. To overcome the problems of thermal damage to surrounding tissues and low laser penetration depth, some exogenous chromophores such as gold nanoshells, a new class of nanoparticles consisting of a dielectric core surrounded by a thin metal shell, are used. The aims of this study were to use two different concentrations of gold nanoshells as the exogenous material for skin tissue soldering and also to examine the effects of laser soldering parameters on the properties of the repaired skin. Material and Methods: Two mixtures of albumin solder and different concentrations of gold nanoshells were prepared. A full thickness incision of 2×20 mm2 was made on the surface and after placing 50 μl of the solder mixture on the incision, an 810 nm diode laser was used to irradiate it at different power densities. The changes of tensile strength, σt, due to temperature rise, number of scan (Ns, and scan velocity (Vs were investigated. Results: The results showed that the tensile strength of the repaired skin increased with increasing irradiance for both gold nanoshell concentrations. In addition, at constant laser irradiance (I, the tensile strength of the repaired incision increased with increasing Ns and decreasing Vs. In our case, this corresponded to st = 1610 g/cm2 at I ~ 60 Wcm-2, T ~ 65ºC, Ns = 10 and Vs = 0.2 mms-1. Discussion and Conclusion: Gold nanoshells can be used as an indocyanine green dye (ICG alterative for laser tissue soldering.  Although by increasing the laser power density, the tensile strength of the repaired skin increases, an optimum power density must be considered due to the resulting increase in tissue temperature.

  11. Flipping the Continuing Medical Education Classroom: Validating a Measure of Attendees' Perceptions.

    Science.gov (United States)

    Stephenson, Christopher R; Wang, Amy T; Szostek, Jason H; Bonnes, Sara L; Ratelle, John T; Mahapatra, Saswati; Mandrekar, Jayawant N; Beckman, Thomas J; Wittich, Christopher M

    2016-01-01

    New teaching approaches for CME are needed. In flipped classrooms, coursework is completed beforehand and applied during class time. Studies of flipped classrooms and their potential benefits in CME have not been published. We sought to develop and validate an instrument measuring flipped classroom perceptions, identify whether participation changed perceptions, and determine which flipped classroom components were perceived as most effective. In this cross-sectional validation study, 167 participants in the Mayo Clinic's 2015 Internal Medicine Board Review course received surveys. Online modules were developed to deliver content before flipped classroom courses on acid-base disorders and electrolyte disorders. A flipped classroom perception instrument (FCPI) was developed and validated. The FCPI, with eight items structured on 5-point Likert scales, was given to participants before and after their flipped classroom experiences. Of the 167 participants, 111 returned surveys. Flipped classroom perceptions improved, with mean (SD) FCPI scores increasing from 3.74 (0.75) to 3.94 (0.76) (P flipped classrooms increased from 38% before the course to 53% after (P = .002). Positive changes in FCPI scores were unrelated to module completion. Most participants thought knowledge was enhanced by in-class sessions and online modules equally. The FCPI, the first validated measure of participants' perceptions of a CME flipped classroom, has strong validity evidence. Participants' perceptions of and preference for the flipped classroom improved after experiencing the flipped CME classroom. These findings support the need to further explore flipped classroom models in CME.

  12. Smart vision chips: An overview

    Science.gov (United States)

    Koch, Christof

    1994-01-01

    This viewgraph presentation presents four working analog VLSI vision chips: (1) time-derivative retina, (2) zero-crossing chip, (3) resistive fuse, and (4) figure-ground chip; work in progress on computing motion and neuromorphic systems; and conceptual and practical lessons learned.

  13. Flipped classrooms and student learning: not just surface gains.

    Science.gov (United States)

    McLean, Sarah; Attardi, Stefanie M; Faden, Lisa; Goldszmidt, Mark

    2016-03-01

    The flipped classroom is a relatively new approach to undergraduate teaching in science. This approach repurposes class time to focus on application and discussion; the acquisition of basic concepts and principles is done on the students' own time before class. While current flipped classroom research has focused on student preferences and comparative learning outcomes, there remains a lack of understanding regarding its impact on students' approaches to learning. Focusing on a new flipped classroom-based course for basic medical sciences students, the purpose of the present study was to evaluate students' adjustments to the flipped classroom, their time on task compared with traditional lectures, and their deep and active learning strategies. Students in this course worked through interactive online learning modules before in-class sessions. Class time focused on knowledge application of online learning module content through active learning methods. Students completed surveys and optional prequiz questions throughout the term to provide data regarding their learning approaches. Our results showed that the majority of students completed their prework in one sitting just before class. Students reported performing less multitasking behavior in the flipped classroom compared with lecture-based courses. Students valued opportunities for peer-peer and peer-instructor interactions and also valued having multiple modes of assessment. Overall, this work suggests that there is the potential for greater educational gains from the flipped classroom than the modest improvements in grades previously demonstrated in the literature; in this implementation of the flipped classroom, students reported that they developed independent learning strategies, spent more time on task, and engaged in deep and active learning. Copyright © 2016 The American Physiological Society.

  14. Mechanical performances of lead-free solder joint connections with applications in the aerospace domain

    Directory of Open Access Journals (Sweden)

    Georgiana PADURARU

    2016-03-01

    Full Text Available The paper presents some theoretical and experimental aspects regarding the tribological performances of lead-free solder joint connections, with application in the aerospace domain. In order to highlight the mechanical and tribological properties of solder joint in correlation with different pad finishes, there were made some mechanical determinations using a dedicated Share Test System. The theoretical model highlights the link between the experimental results and the influence of gravitational acceleration on the mechanical and functional integrity of the electronic assemblies that works in vibration environment. The paper novelty is provided by the interdisciplinary experiment that offers results that can be used in the mechanical, tribological, electronical and aerospace domains.

  15. A Feasibility Study of Lead Free Solders for Level 1 Packaging Applications

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Hattel, Jesper Henri

    2009-01-01

    An attempt has been made to determine the lead free ternary combinations that satisfied the solidification requirement for a solder used in level 1 packaging applications, using the CALPHAD approach. The segregation profiles of the promising candidates were analyzed after scrutinizing the equilib......An attempt has been made to determine the lead free ternary combinations that satisfied the solidification requirement for a solder used in level 1 packaging applications, using the CALPHAD approach. The segregation profiles of the promising candidates were analyzed after scrutinizing...

  16. A review of typical thermal fatigue failure models for solder joints of electronic components

    Science.gov (United States)

    Li, Xiaoyan; Sun, Ruifeng; Wang, Yongdong

    2017-09-01

    For electronic components, cyclic plastic strain makes it easier to accumulate fatigue damage than elastic strain. When the solder joints undertake thermal expansion or cold contraction, different thermal strain of the electronic component and its corresponding substrate is caused by the different coefficient of thermal expansion of the electronic component and its corresponding substrate, leading to the phenomenon of stress concentration. So repeatedly, cracks began to sprout and gradually extend [1]. In this paper, the typical thermal fatigue failure models of solder joints of electronic components are classified and the methods of obtaining the parameters in the model are summarized based on domestic and foreign literature research.

  17. Physics of Failure as a Basis for Solder Elements Reliability Assessment in Wind Turbines

    DEFF Research Database (Denmark)

    Kostandyan, Erik; Sørensen, John Dalsgaard

    2012-01-01

    description of the reliability. A physics of failure approach is applied. A SnAg solder component used in power electronics is used as an example. Crack propagation in the SnAg solder is modeled and a model to assess the accumulated plastic strain is proposed based on a physics of failure approach. Based...... on the proposed model it is described how to find the accumulated linear damage and reliability levels for a given temperature loading profile. Using structural reliability methods the reliability levels of the electrical components are assessed by introducing scale factors for stresses....

  18. Aging treatment characteristics of solder bump joint for high reliability optical module

    International Nuclear Information System (INIS)

    Kim, Kyung-Seob; Yu, Chung-Hee; Yang, Jun-Mo

    2004-01-01

    The joint strength and fracture surfaces of Sn-37 mass% Pb and Au stud bumps for photo diode packages after isothermal aging testing were studied experimentally. Al/Au stud bumps and Cu/Sn-37 mass% Pb solders were adopted, and aged for up to 900 h to analyze the effect of intermetallic compound (IMC). The joint strength decreased with aging time. The diffraction patterns of Cu 6 Sn 5 , scallop-shaped IMCs, and planar-shaped Cu 3 Sn were characterized using transmission electron microscopy (TEM). The formation of Kirkendall voids and the growth of IMCs at the solder were found to be a possible mechanism for joint strength reduction

  19. Constrained Sypersymmetric Flipped SU (5) GUT Phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, John; /CERN /King' s Coll. London; Mustafayev, Azar; /Minnesota U., Theor. Phys. Inst.; Olive, Keith A.; /Minnesota U., Theor. Phys. Inst. /Minnesota U. /Stanford U., Phys. Dept. /SLAC

    2011-08-12

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, Min, above the GUT scale, M{sub GUT}. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino {chi} and the lighter stau {tilde {tau}}{sub 1} is sensitive to M{sub in}, as is the relationship between m{sub {chi}} and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m{sub 1/2}, m{sub 0}) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to Min, as we illustrate for several cases with tan {beta} = 10 and 55. However, these features do not necessarily disappear at large Min, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses.

  20. Constrained supersymmetric flipped SU(5) GUT phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, John [CERN, TH Division, PH Department, Geneva 23 (Switzerland); King' s College London, Theoretical Physics and Cosmology Group, Department of Physics, London (United Kingdom); Mustafayev, Azar [University of Minnesota, William I. Fine Theoretical Physics Institute, Minneapolis, MN (United States); Olive, Keith A. [University of Minnesota, William I. Fine Theoretical Physics Institute, Minneapolis, MN (United States); Stanford University, Department of Physics and SLAC, Palo Alto, CA (United States)

    2011-07-15

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, M{sub in}, above the GUT scale, M{sub GUT}. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino {chi} and the lighter stau {tau}{sub 1} is sensitive to M{sub in}, as is the relationship between m{sub {chi}} and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m{sub 1/2},m{sub 0}) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to M{sub in}, as we illustrate for several cases with tan {beta}=10 and 55. However, these features do not necessarily disappear at large M{sub in}, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses. (orig.)

  1. Flipped spinfoam vertex and loop gravity

    Energy Technology Data Exchange (ETDEWEB)

    Engle, Jonathan; Pereira, Roberto [CPT, CNRS Case 907, Universite de la Mediterranee, F-13288 Marseille (France); Rovelli, Carlo [CPT, CNRS Case 907, Universite de la Mediterranee, F-13288 Marseille (France)], E-mail: rovelli@cpt.univ-mrs.fr

    2008-07-21

    We introduce a vertex amplitude for 4d loop quantum gravity. We derive it from a conventional quantization of a Regge discretization of euclidean general relativity. This yields a spinfoam sum that corrects some difficulties of the Barrett-Crane theory. The second class simplicity constraints are imposed weakly, and not strongly as in Barrett-Crane theory. Thanks to a flip in the quantum algebra, the boundary states turn out to match those of SO(3) loop quantum gravity-the two can be identified as eigenstates of the same physical quantities-providing a solution to the problem of connecting the covariant SO(4) spinfoam formalism with the canonical SO(3) spin-network one. The vertex amplitude is SO(3) and SO(4)-covariant. It rectifies the triviality of the intertwiner dependence of the Barrett-Crane vertex, which is responsible for its failure to yield the correct propagator tensorial structure. The construction provides also an independent derivation of the kinematics of loop quantum gravity and of the result that geometry is quantized.

  2. String threshold corrections and flipped SU(5)

    Energy Technology Data Exchange (ETDEWEB)

    Antoniadis, I. (Ecole Polytechnique, Centre de Physique Theorique, 91 - Palaiseau (France) Theory Div., CERN, Geneva (Switzerland)); Ellis, J. (Theory Div., CERN, Geneva (Switzerland)); Lacaze, R. (Service de Physique Theorique, CEN-Saclay, 91 - Gif-sur-Yvette (France)); Nanopoulos, D.V. (Center for Theoretical Physics, Dept. of Physics, Texas A and M Univ., College Station, TX (United States) Astroparticle Physics Group, HARC, The Woodlands, TX (United States) Theory Div., CERN, Geneva (Switzerland))

    1991-10-10

    We revise previous calculations of the effective unification scale m{sub SU} at which the extrapolated low-energy gauge couplings should appear to become equal, and we show explicitly how to calculate m{sub SU} in the fermionic construction of four-dimensional strings. In the case of the flipped SU(5) GUT derived from the string, the SU(5) and U(1) couplings defined in the anti Danti R scheme become equal to g{sub SU} at m{sub SU} {approx equal} 1.76 x g{sub SU} x 10{sup 18} GeV. This scale is significantly larger than m{sub GUT}, the scale at which the low-energy SU(3) and SU(2) couplings become equal if extrapolated using the renormalization group equations of the minimal supersymmetric extension of the standard model. The existence of an intermediate SU(5) x U(1) phase could have an observable effect on the calculated value of sin{sup 2}{theta}{sub w}. (orig.).

  3. Sharpening the flipped SU(5) string model

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, J.L. (Center for Theoretical Physics, Dept. of Physics, Texas A and M Univ., College Station, TX (United States) Astroparticle Physics Group, Houston Advanced Research Center (HARC), The Woodlands, TX (United States)); Nanopoulos, D.V. (Center for Theoretical Physics, Dept. of Physics, Texas A and M Univ., College Station, TX (United States) Astroparticle Physics Group, Houston Advanced Research Center (HARC), The Woodlands, TX (United States) Theoretical Physics Div., CERN, Geneva (Switzerland))

    1991-10-17

    We present an improved version of the flipped SU(5) string model which accommodates numerous existing and expected features of the low-energy physics world, such as (i) two Higgs doublets with adequate mixing between them; (ii) hierarchy of quark and lepton masses, including relations such as m{sub s}/m{sub b}{proportional to}m{sub {mu}}/m{sub {tau}}, and m{sub c}/m{sub t}{sup 1/2.}, (iii) sufficiently suppressed proton decay operators, with gauge-boson mediated decays favoring p{yields}anti {nu}{sub {tau}}{pi}{sup +} and n{yields}anti {nu}{sub {tau}}, {pi}{sup 0}, (iv) nearly massless {nu}{sub {mu}} and {nu}{sub {tau}}, and {nu}{sub e} in the eV range; (v) heavy top quark (m{sub t} < or approx. 170 GeV) and large ratio of vacuum expectation values (tan {beta} < or approx. 33). (orig.).

  4. Flipped classroom or an active lecture?

    Science.gov (United States)

    Pickering, James D; Roberts, David J H

    2018-01-01

    Recent changes in anatomy education have seen the introduction of flipped classrooms as a replacement to the traditional didactic lecture. This approach utilizes the increasing availability of digital technology to create learning resources that can be accessed prior to attending class, with face-to-face sessions then becoming more student-centered via discussion, collaborative learning, and problem-solving activities. Although this approach may appear intuitive, this viewpoint commentary presents a counter opinion and highlights a simple alternative that utilizes evidence-based active learning approaches as part of the traditional lecture. The active lecture takes the traditional lecture, and (1) ensures the lecture content is relevant and has clear objectives, (2) contains lecture material that is designed according to the latest evidence-base, (3) complements it with additional supplementary material, (4) creates space to check prior understanding and knowledge levels, and (5) utilizes suitable technology to facilitate continual engagement and interaction. Clin. Anat. 31:118-121, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  5. Constrained Supersymmetric Flipped SU(5) GUT Phenomenology

    CERN Document Server

    Ellis, John; Olive, Keith A

    2011-01-01

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, $M_{in}$, above the GUT scale, $M_{GUT}$. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino and the lighter stau is sensitive to $M_{in}$, as is the relationship between the neutralino mass and the masses of the heavier Higgs bosons. For these reasons, prominent features in generic $(m_{1/2}, m_0)$ planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to $M_{in}$, as we illustrate for several cases with tan(beta)...

  6. Spin-flip tunneling in quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Schreiber, Lars; Braakman, Floris; Meunier, Tristan; Calado, Victor; Vandersypen, Lieven [Kavli Institute of NanoScience, Delft (Netherlands); Wegscheider, Werner [Institute for Experimental and Applied Physics, University of Regensburg (Germany)

    2010-07-01

    Electron spins in a gate-defined double quantum dot formed in a GaAs/(Al,Ga)As 2DEG are promising candidates for quantum information processing as coherent single spin rotation and spin swap has been demonstrated recently. In this system we investigate the two-electron spin dynamics in the presence of microwaves (5.20 GHz) applied to one side gate. During microwave excitation we observe characteristic photon assisted tunneling (PAT) peaks at the (1,1) to (0,2) charge transition. Some of the PAT peaks are attributed to photon tunneling events between the singlet S(0,2) and the singlet S(1,1) states, a spin-conserving transition. Surprisingly, other PAT peaks stand out by their different external magnetic field dependence. They correspond to tunneling involving a spin-flip, from the (0,2) singlet to a (1,1) triplet. The full spectrum of the observed PAT lines is captured by simulations. This process offers novel possibilities for 2-electron spin manipulation and read-out.

  7. Constrained supersymmetric flipped SU(5) GUT phenomenology

    International Nuclear Information System (INIS)

    Ellis, John; Mustafayev, Azar; Olive, Keith A.

    2011-01-01

    We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, M in , above the GUT scale, M GUT . We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino χ and the lighter stau τ 1 is sensitive to M in , as is the relationship between m χ and the masses of the heavier Higgs bosons A,H. For these reasons, prominent features in generic (m 1/2 ,m 0 ) planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to M in , as we illustrate for several cases with tan β=10 and 55. However, these features do not necessarily disappear at large M in , unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses. (orig.)

  8. The flipped classroom: now or never?

    Science.gov (United States)

    Hawks, Sharon J

    2014-08-01

    Pedagogical changes and new models of delivering educational content should be considered in the effort to address the recommendations of the 2007 Institute of Medicine report and Benner's recommendations on the radical transformation of nursing. Transition to the nurse anesthesia practice doctorate addresses the importance of these recommendations, but educational models and specific strategies on how to implement changes in educational models and systems are still emerging. The flipped classroom (FC) is generating a considerable amount of buzz in academic circles. The FC is a pedagogical model that employs asynchronous video lectures, reading assignments, practice problems, and other digital, technology-based resources outside the classroom, and interactive, group-based, problem-solving activities in the classroom. This FC represents a unique combination of constructivist ideology and behaviorist principles, which can be used to address the gap between didactic education and clinical practice performance. This article reviews recent evidence supporting use of the FC in health profession education and suggests ways to implement the FC in nurse anesthesia educational programs.

  9. Spin flipping a stored polarized proton beam with an rf magnetic field

    International Nuclear Information System (INIS)

    Hu, S.Q.; Blinov, B.B.; Caussyn, D.D.

    1995-01-01

    The authors studied the spin flipping of a vertically polarized, stored 139 MeV proton beam with an rf solenoid magnetic field. By sweeping the rf frequency through an rf depolarizing resonance, they made the spin flip. The spin flipping was more efficient for slower ramp times, and the spin flip efficiency peaked at some optimum ramp time that is not yet fully understood. Since frequent spin flipping could significantly reduce the systematic errors in scattering experiments using a stored polarized beam, it is very important to minimize the depolarization after each spin flip. In this experiment, with multiple spin flips, the authors found a polarization loss of 0.0000 ± 0.0005 per spin flip under the best conditions; this loss increased significantly for small changes in the conditions

  10. Influence of nanoparticle addition on the formation and growth of intermetallic compounds (IMCs) in Cu/Sn–Ag–Cu/Cu solder joint during different thermal conditions

    Science.gov (United States)

    Ting Tan, Ai; Wen Tan, Ai; Yusof, Farazila

    2015-01-01

    Nanocomposite lead-free solders are gaining prominence as replacements for conventional lead-free solders such as Sn–Ag–Cu solder in the electronic packaging industry. They are fabricated by adding nanoparticles such as metallic and ceramic particles into conventional lead-free solder. It is reported that the addition of such nanoparticles could strengthen the solder matrix, refine the intermetallic compounds (IMCs) formed and suppress the growth of IMCs when the joint is subjected to different thermal conditions such as thermal aging and thermal cycling. In this paper, we first review the fundamental studies on the formation and growth of IMCs in lead-free solder joints. Subsequently, we discuss the effect of the addition of nanoparticles on IMC formation and their growth under several thermal conditions. Finally, an outlook on the future growth of research in the fabrication of nanocomposite solder is provided. PMID:27877786

  11. Influence of nanoparticle addition on the formation and growth of intermetallic compounds (IMCs) in Cu/Sn–Ag–Cu/Cu solder joint during different thermal conditions

    International Nuclear Information System (INIS)

    Ting Tan, Ai; Wen Tan, Ai; Yusof, Farazila

    2015-01-01

    Nanocomposite lead-free solders are gaining prominence as replacements for conventional lead-free solders such as Sn–Ag–Cu solder in the electronic packaging industry. They are fabricated by adding nanoparticles such as metallic and ceramic particles into conventional lead-free solder. It is reported that the addition of such nanoparticles could strengthen the solder matrix, refine the intermetallic compounds (IMCs) formed and suppress the growth of IMCs when the joint is subjected to different thermal conditions such as thermal aging and thermal cycling. In this paper, we first review the fundamental studies on the formation and growth of IMCs in lead-free solder joints. Subsequently, we discuss the effect of the addition of nanoparticles on IMC formation and their growth under several thermal conditions. Finally, an outlook on the future growth of research in the fabrication of nanocomposite solder is provided. (review)

  12. [Flipped classroom as a strategy to enhance active learning].

    Science.gov (United States)

    Wakabayashi, Noriyuki

    2015-03-01

    This paper reviews the introduction of a flipped class for fourth grade dentistry students, and analyzes the characteristics of the learning method. In fiscal 2013 and 2014, a series of ten three-hour units for removable partial prosthodontics were completed with the flipped class method; a lecture video of approximately 60 minutes was made by the teacher (author) and uploaded to the university's e-learning website one week before each class. Students were instructed to prepare for the class by watching the streaming video on their PC, tablet, or smartphone. In the flipped class, students were not given a lecture, but were asked to solve short questions displayed on screen, to make a short presentation about a part of the video lecture, and to discuss a critical question related to the main subject of the day. An additional team-based learning (TBL) session with individual and group answers was implemented. The average individual scores were considerably higher in the last two years, when the flipped method was implemented, than in the three previous years when conventional lectures were used. The following learning concepts were discussed: the role of the flipped method as an active learning strategy, the efficacy of lecture videos and short questions, students' participation in the class discussion, present-day value of the method, cooperation with TBL, the significance of active learning in relation with the students' learning ability, and the potential increase in the preparation time and workload for students.

  13. The influence of flip angle on the magic angle effect

    International Nuclear Information System (INIS)

    Zurlo, J.V.; Blacksin, M.F.; Karimi, S.

    2000-01-01

    Objective. To assess the impact of flip angle with gradient sequences on the ''magic angle effect''. We characterized the magic angle effect in various gradient echo sequences and compared the signal- to-noise ratios present on these sequences with the signal-to-noise ratios of spin echo sequences.Design. Ten normal healthy volunteers were positioned such that the flexor hallucis longus tendon remained at approximately at 55 to the main magnetic field (the magic angle). The tendon was imaged by a conventional spin echo T1- and T2-weighted techniques and by a series of gradient techniques. Gradient sequences were altered by both TE and flip angle. Signal-to-noise measurements were obtained at segments of the flexor hallucis longus tendon demonstrating the magic angle effect to quantify the artifact. Signal-to-noise measurements were compared and statistical analysis performed. Similar measurements were taken of the anterior tibialis tendon as an internal control.Results and conclusions. We demonstrated the magic angle effect on all the gradient sequences. The intensity of the artifact was affected by both the TE and flip angle. Low TE values and a high flip angle demonstrated the greatest magic angle effect. At TE values less than 30 ms, a high flip angle will markedly increase the magic angle effect. (orig.)

  14. Flipped classroom model for learning evidence-based medicine

    Directory of Open Access Journals (Sweden)

    Rucker SY

    2017-08-01

    Full Text Available Sydney Y Rucker,1 Zulfukar Ozdogan,1 Morhaf Al Achkar2 1School of Education, Indiana University, Bloomington, IN, 2Department of Family Medicine, School of Medicine, University of Washington, Seattle, WA, USA Abstract: Journal club (JC, as a pedagogical strategy, has long been used in graduate medical education (GME. As evidence-based medicine (EBM becomes a mainstay in GME, traditional models of JC present a number of insufficiencies and call for novel models of instruction. A flipped classroom model appears to be an ideal strategy to meet the demands to connect evidence to practice while creating engaged, culturally competent, and technologically literate physicians. In this article, we describe a novel model of flipped classroom in JC. We present the flow of learning activities during the online and face-to-face instruction, and then we highlight specific considerations for implementing a flipped classroom model. We show that implementing a flipped classroom model to teach EBM in a residency program not only is possible but also may constitute improved learning opportunity for residents. Follow-up work is needed to evaluate the effectiveness of this model on both learning and clinical practice. Keywords: evidence-based medicine, flipped classroom, residency education

  15. Student performance in a flipped classroom dental anatomy course.

    Science.gov (United States)

    Chutinan, S; Riedy, C A; Park, S E

    2017-11-09

    The purpose of this study was to assess dental student learning in a dental anatomy module between traditional lecture and flipped classroom cohorts. Two cohorts of predoctoral dental students (N = 70 within each cohort) participated in a dental anatomy module within an Introduction to the Dental Patient (IDP) course ([traditional/lecture cohort: academic year (AY) 2012, 2013] and [flipped classroom cohort: AY 2014, 2015]). For the dental anatomy module, both cohorts were evaluated on pre-clinical tooth waxing exercises immediately after each of five lectures and tooth identification after all lectures were given. Additionally, the cohorts' performance on the overall IDP course examination was compared. The flipped classroom cohort had statistically significant higher waxing scores (dental anatomy module) than students in the traditional classroom. There was no statistically significant difference for tooth identification scores and the overall IDP course examination between the traditional vs flipped approach cohorts. This is due to the latter two assessments conducted at the end of the course gave all students enough time to review the lecture content prior to the assessment resulting in similar scores for both cohorts. The flipped classroom cohort promoted students' individual learning and resulted in improved students' performance on immediate evaluation but not on the end of the course evaluation. Redesign of courses to include a new pedagogical approach should be carefully implemented and evaluated for student's educational success. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  16. What millennial medical students say about flipped learning

    Directory of Open Access Journals (Sweden)

    Pettit RK

    2017-07-01

    Full Text Available Robin K Pettit, Lise McCoy, Marjorie Kinney School of Osteopathic Medicine in Arizona, A. T. Still University, Mesa, AZ, USA Abstract: Flipped instruction is gaining popularity in medical schools, but there are unanswered questions such as the optimum amount of the curriculum to flip and whether flipped sessions should be mandatory. We were in a unique position to evaluate feedback from first-year medical students who had experienced both flipped and lecture-based courses during their first semester of medical school. A key finding was that the students preferred a variety of different learning formats over an “all or nothing” learning format. Learning format preferences did not necessarily align with perceptions of which format led to better course exam performance. Nearly 70% of respondents wanted to make their own decisions regarding attendance. Candid responses to open-ended survey prompts reflected millennial preferences for choice, flexibility, efficiency, and the ability to control the pace of their learning, providing insight to guide ­curricular improvements. Keywords: flipped classroom, mandatory attendance, medical education, lecture-based, variety

  17. On flipping first-semester calculus: a case study

    Science.gov (United States)

    Petrillo, Joseph

    2016-05-01

    High failure rates in calculus have plagued students, teachers, and administrators for decades, while science, technology, engineering, and mathematics programmes continue to suffer from low enrollments and high attrition. In an effort to affect this reality, some educators are 'flipping' (or inverting) their classrooms. By flipping, we mean administering course content outside of the classroom and replacing the traditional in-class lectures with discussion, practice, group work, and other elements of active learning. This paper presents the major results from a three-year study of a flipped, first-semester calculus course at a small, comprehensive, American university with a well-known engineering programme. The data we have collected help quantify the positive and substantial effects of our flipped calculus course on failure rates, scores on the common final exam, student opinion of calculus, teacher impact on measurable outcomes, and success in second-semester calculus. While flipping may not be suitable for every teacher, every student, and in every situation, this report provides some evidence that it may be a viable option for those seeking an alternative to the traditional lecture model.

  18. Microstructural evolution and tensile properties of Sn-Ag-Cu mixed with Sn-Pb solder alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang Fengjiang [Department of Materials Science and Engineering and Materials Research Center, Missouri University of Science and Technology, Rolla, MO 65401 (United States); O' Keefe, Matthew [Department of Materials Science and Engineering and Materials Research Center, Missouri University of Science and Technology, Rolla, MO 65401 (United States)], E-mail: mjokeefe@mst.edu; Brinkmeyer, Brandon [Department of Materials Science and Engineering and Materials Research Center, Missouri University of Science and Technology, Rolla, MO 65401 (United States)

    2009-05-27

    The effect of incorporating eutectic Sn-Pb solder with Sn-3.0Ag-0.5Cu (SAC) Pb-free solder on the microstructure and tensile properties of the mixed alloys was investigated. Alloys containing 100, 75, 50, 25, 20, 15, 10, 5 and 0 wt% SAC, with the balance being Sn-37Pb eutectic solder alloy, were prepared and characterized. Optical and scanning electron microscopy were used to analyze the microstructures while 'mini-tensile' test specimens were fabricated and tested to determine mechanical properties at the mm length scale, more closely matching that of the solder joints. Microstructural analysis indicated that a Pb-rich phase formed and was uniformly distributed at the boundary between the Sn-rich grains or between the Sn-rich and the intermetallic compounds in the solder. Tensile results showed that mixing of the alloys resulted in an increase in both the yield and the ultimate tensile strength compared to the original solders, with the 50% SAC-50% Sn-Pb mixture having the highest measured strength. Initial investigations indicate the formation and distribution of a Pb-rich phase in the mixed solder alloys as the source of the strengthening mechanism.

  19. Flipped Instruction with English Language Learners at a Newcomer High School

    Science.gov (United States)

    Graziano, Kevin J.; Hall, John D.

    2017-01-01

    Research on flipped instruction with English Language Learners (ELLs) is sparse. Data-driven flipped research conducted with ELLs primarily involves adult learners attending a college or university. This study examined the academic performance of secondary ELLs who received flipped instruction in an algebra course at a newcomer school compared to…

  20. Correlations between Learners' Initial EFL Proficiency and Variables of Clicker-Aided Flipped EFL Class

    Science.gov (United States)

    Yu, Zhonggen; Yu, Liheng

    2017-01-01

    Although the flipped class has been hotly discussed, the clicker-aided flipped EFL class (CFEC) still remains a mystery for most scholars. This study aims to determine the correlations between the initial EFL proficiency and other variables of the clicker-aided EFL flipped class. The sample was made up of randomly selected 79 participants (Female…