Sample records for warpage

  1. Warpage of rubber pressed composites

    NARCIS (Netherlands)

    Wijskamp, Sebastiaan; Lamers, E.A.D.; Akkerman, Remko; van de Ven, Erik


    The rubber pressing process is applied for the rapid production of thermoplastic composite products. However, rubber pressed products show geometrical distortions, such as warpage, due to process-induced residual stresses. It is believed that these stresses build up as a result of the large thermal

  2. Full-field wafer warpage measurement technique (United States)

    Hsieh, H. L.; Lee, J. Y.; Huang, Y. G.; Liang, A. J.; Sun, B. Y.


    An innovative moiré technique for full-field wafer warpage measurement is proposed in this study. The wafer warpage measurement technique is developed based on moiré method, Talbot effect, scanning profiling method, stroboscopic, instantaneous phase-shift method, as well as four-step phase shift method, high resolution, high stability and full-field measurement capabilities can be easily achieved. According to the proposed full-field optical configuration, a laser beam is expanded into a collimated beam with a 2-inch diameter and projected onto the wafer surface. The beam is reflected by the wafer surface and forms a moiré fringe image after passing two circular gratings, which is then focused and captured on a CCD camera for computation. The corresponding moiré fringes reflected from the wafer surface are obtained by overlapping the images of the measuring grating and the reference grating. The moiré fringes will shift when wafer warpage occurs. The phase of the moiré fringes will change proportionally to the degree of warpage in the wafer, which can be measured by detecting variations in the phase shift of the moiré fringes in each detection points on the surface of the entire wafer. The phase shift variations of each detection points can be calculated via the instantaneous phase-shift method and the four-step phase-shift method. By adding up the phase shift variations of each detection points along the radii of the circular gratings, the warpage value and surface topography of the wafer can be obtained. Experiments show that the proposed method is capable of obtaining test results similar to that of a commercial sensor, as well as performing accurate measurements under high speed rotation of 1500rpm. As compared to current warpage measurement methods such as the beam optical method, confocal microscopy, laser interferometry, shadow moiré method, and structured light method, this proposed technique has the advantage of full-field measurement, high

  3. Corneal Biomechanical Findings in Contact Lens Induced Corneal Warpage (United States)

    Letafatnejad, Mojgan; Beheshtnejad, Amir Hooshang; Ghaffary, Seyed Reza; Hassanpoor, Narges; Yaseri, Mehdi


    Purpose. To evaluate the difference in biomechanical properties between contact lens induced corneal warpage and normal and keratoconic eyes. Method. Prospective observational case control study, where 94 eyes of 47 warpage suspicious and 46 eyes of 23 keratoconic patients were included. Warpage suspected cases were followed until a definite diagnosis was made (warpage, normal, or keratoconus). Results. 44 eyes of 22 patients had contact lens related corneal warpage. 46 eyes of 23 people were diagnosed as nonwarpage normal eyes. 46 eyes of 23 known keratoconus patients were included for comparison. The mean age of the participants was 23.8 ± 3.8 years, and 66.2% of the subjects were female. The demographic and refractive data were not different between warpage and normal groups but were different in the keratoconus group. The biomechanical properties (corneal hysteresis or CH and corneal resistance factor or CRF) were different with the highest value in the warpage group followed by normal and keratoconus groups. CRF was 10.08 ± 1.75, 9.23 ± 1.22, and 7.38 ± 2.14 and CH was 10.21 ± 1.57, 9.59 ± 1.21, and 8.69 ± 2.34 in the warpage, normal, and keratoconus groups, respectively. Conclusion. Corneal biomechanics may be different in people who develop contact lens induced warpage. PMID:27688908

  4. A Recurrent Neural Network for Warpage Prediction in Injection Molding

    Directory of Open Access Journals (Sweden)

    A. Alvarado-Iniesta


    Full Text Available Injection molding is classified as one of the most flexible and economical manufacturing processes with high volumeof plastic molded parts. Causes of variations in the process are related to the vast number of factors acting during aregular production run, which directly impacts the quality of final products. A common quality trouble in finishedproducts is the presence of warpage. Thus, this study aimed to design a system based on recurrent neural networksto predict warpage defects in products manufactured through injection molding. Five process parameters areemployed for being considered to be critical and have a great impact on the warpage of plastic components. Thisstudy used the finite element analysis software Moldflow to simulate the injection molding process to collect data inorder to train and test the recurrent neural network. Recurrent neural networks were used to understand the dynamicsof the process and due to their memorization ability, warpage values might be predicted accurately. Results show thedesigned network works well in prediction tasks, overcoming those predictions generated by feedforward neuralnetworks.

  5. Comprehensive Warpage Analysis of Stacked Die MEMS Package in Accelerometer Application

    Institute of Scientific and Technical Information of China (English)


    Packaging of MEMS ( micro-electro-mechanical system ) devices poses more challenges than conventional IC packaging, since the performance of the MEMS devices is highly dependent on packaging processes. A Land Grid Array (LGA) package is introduced for MEMS technology based linear multi-axis accelerometers. Finite element modeling is conducted to simulate the warpage behavior of the LGA packages. A method to correlate the package warpage to matrix block warpage has been developed. Warpage for both package and sensor substrate are obtained. Warpage predicted by simulation correlates very well with experimental measurements. Based on this validated method, detailed design analysis with different package geometrical variations are carried out to optimize the package design. With the optimized package structure,the packaging effect on accelerometer signal performance is well controlled.

  6. Influence of the Viscoelastic Properties of the Polyimide Dielectric Coating on the Wafer Warpage (United States)

    Zhu, Chunsheng; Ning, Wenguo; Xu, Gaowei; Luo, Le


    Polyimide is widely used as the dielectric material in wafer level packaging. One potential problem with its application is the warpage and stress generated in the curing process. This paper investigated the material properties of polyimide and its influence on the wafer warpage. The viscoelastic properties of polyimide film were measured and a mathematical model of the properties was developed. Finite element analysis of the wafer warpage was performed and this indicates that the viscoelastic material model gave the best prediction. To better understand the causation of the warpage, curvature evolution of the polyimide-coated silicon wafer during its curing process was measured by a multi-beam optical sensor system. It was found that the warpage was mainly induced by the coefficient of thermal expansion mismatch and that the cure shrinkage of polyimide had little effect. Additionally, the effect of the cooling rate on the wafer warpage was also studied. Both simulation and experiment results showed that a slower cooling rate in the temperature range around the glass transition temperature ( T g) of polyimide will help to reduce the final wafer warpage.

  7. Study of Injection Molding Warpage Using Analytic Hierarchy Process and Taguchi Method

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    Dyi-Cheng Chen


    Full Text Available This study integrated Analytic Hierarchy Process and Taguchi method to investigate into injection molding warpage. The warpage important factor will be elected by Analytic Hierarchy Process (AHP, the AHP hierarchy analysis factor from documents collected and aggregate out data, then through the expert questionnaire delete low weight factor. Finally, we used Taguchi quality engineering method to decide injection molding optimized combination factors. Furthermore, the paper used injection pressure, holding pressure, holding time, mold temperature to analyze four factors, three levels Taguchi design data. Moreover, the paper discussed the reaction of each factor on the S / N ratio and analysis of variance to obtain the best combination of minimal warpage.

  8. Warpage Analysis of Electroplated Cu Films on Fiber-Reinforced Polymer Packaging Substrates

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    Cheolgyu Kim


    Full Text Available This paper presents a warpage analysis method that predicts the warpage behavior of electroplated Cu films on glass fiber-reinforced polymer (GFRP packaging substrates. The analysis method is performed using the following sequence: fabricate specimens for scanning 3D contours, transform 3D data into curvatures, compute the built-in stress of the film using a stress-curvature analytic model, and verify it through comparisons of the finite element method (FEM simulations with the measured data. The curvature is used to describe the deflection and warpage modes and orientations of the specimen. Two primary factors that affect the warpage behavior of the electroplated Cu film on FRP substrate specimens are investigated. The first factor is the built-in stress in a Cu film that explains the room temperature warpage of the specimen under no thermal process. The second factor is the misfit of the coefficient of thermal expansion (CTE between the Cu and FRP layer, which is a dominant factor during the temperature change. The calculated residual stress, and predicted curvatures using FEM simulation throughout the reflow process temperature range between 25 and 180 °C are proven to be accurate by the comparison of the FEM simulations and experiment measurements.

  9. Experimental evaluation and simulation of volumetric shrinkage and warpage on polymeric composite reinforced with short natural fibers (United States)

    Santos, Jonnathan D.; Fajardo, Jorge I.; Cuji, Alvaro R.; García, Jaime A.; Garzón, Luis E.; López, Luis M.


    A polymeric natural fiber-reinforced composite is developed by extrusion and injection molding process. The shrinkage and warpage of high-density polyethylene reinforced with short natural fibers of Guadua angustifolia Kunth are analyzed by experimental measurements and computer simulations. Autodesk Moldflow® and Solid Works® are employed to simulate both volumetric shrinkage and warpage of injected parts at different configurations: 0 wt.%, 20 wt.%, 30 wt.% and 40 wt.% reinforcing on shrinkage and warpage behavior of polymer composite. Become evident the restrictive effect of reinforcing on the volumetric shrinkage and warpage of injected parts. The results indicate that volumetric shrinkage of natural composite is reduced up to 58% with fiber increasing, whereas the warpage shows a reduction form 79% to 86% with major fiber content. These results suggest that it is a highly beneficial use of natural fibers to improve the assembly properties of polymeric natural fiber-reinforced composites.

  10. The effect of mandrel configuration on the warpage in pultrusion of rectangular hollow profiles

    DEFF Research Database (Denmark)

    Baran, Ismet; Hattel, Jesper Henri; Akkerman, Remko


    pultrusion company. In addition, the predicted warpage behaviour is further analysed by adjusting the mandrel length as well as including the mandrel heating. Using the proposed process model, the effect of the mandrel configurations on the quality of the pultrusion is investigated in terms of temperature......, degree of cure and distortions.These unwanted residual distortions may lead to not meeting the desired geometrical tolerances e.g. warpage of pultruded window frames and hollow profiles as well as spring-in of L-shaped profiles, etc....

  11. Investigation of process induced warpage for pultrusion of a rectangular hollow profile

    DEFF Research Database (Denmark)

    Baran, Ismet; Hattel, Jesper Henri; Akkerman, Remko


    with a commercial polyester resin mixture (Atlac 382). The reactivity of the resin is obtained from gel tests performed by the pultruder. The cure kinetics parameters are estimated from a fitting procedure against the measured temperature. The cure hardening instantaneous linear elastic (CHILE) model is adopted...... for the evolution of the resin elastic modulus using the temperature-dependent elastic response provided by the resin supplier. The numerical model predictions for the warpage trend at the end of the process are found to agree well with the warpage observed in the real pultruded products. In addition...

  12. Characterizetion of Flexural Strength, Warpage and Shrinkage of Polypropylene-Nanoclay-Nanocomposites Blend with Gigantochloa Scortechinii. (United States)

    Khamis, S. Z.; Othman, M. H.; Hasan, S.; Ibrahim, M. H. I.


    This paper presents the characterization of Flexural Strength, Warpage and Shrinkage of reinforcement gigantochloa scortechinii fibre. The content of fiber were fixed at 0 wt.%, 3 wt.% and 6 wt.% in uniform increased. The selected injection moulding processing conditions were packing pressure, melt temperature, screw speed and filling time. The quality factors that need to be improved upon the characterization were flexural strength, warpage and shrinkage. This research started by drying the Gigantochloa Scortechinii fibres at 120°C. After that, 3 wt.% of the fibres were mixed with 81 wt.% of polypropylene, 15 wt.% of polypropylene grafted maleic anhydride (compatibilizer) and 1 wt. % of nanoclay. Samples with 6 wt.% of fibers were also prepared for comparison purpose. The mixing process was performed by using Brabender Lab-Compounder KETSE 20/40 and the pallets were produced using used Brabender® pelletizer with diameters of 1 to 4 mm. The optimisation process was accomplished by adopting the Taguchi L9 orthogonal array method. According to the results, for 0 wt.% GS, the flexural strength is 30.0082 MPa, the warpage is 0.0030000 mm and the shrinkage is 0.0003830 mm at packing pressure 40%, melt temperature 165°C, filled time 2 seconds and screw speed 35%. For the result 3 wt.% GS, the flexural strength is 32.2477 MPa, the warpage is 0.006670 mm and the shrinkage is 0.0003830 mm at packing pressure is 35%, melt temperature 165°C, filled times is 1 seconds and screw speed is 30%. While for the 6 wt.% GS, the results of the flexural strength is 36.9084 MPa, the warpage is 0.0066700 mm and the shrinkage is 0.0003830 mm at packing pressure is 35%, melt temperature 165°C, filled time is 2 seconds and screw speed is 30%. The existence of Gigantochloa Scortechinii fibre was also proven to effect significantly towards flexural strength with 6% increasing value ordering from 0 wt.% GS to 6 wt.% GS. while, the warpage value increasing from 0.003000 mm to 0.00667 mm and

  13. Analysis of Cavity Pressure and Warpage of Polyoxymethylene Thin Walled Injection Molded Parts: Experiments and Simulations

    DEFF Research Database (Denmark)

    Guerrier, Patrick; Tosello, Guido; Hattel, Jesper Henri


    , melt and mold temperatures, material rheological and pvT characterization. Factors investigated for comparisons were: injection pressure profile, short shots length, flow pattern, and warpage. A reliable molding experimental database was obtained, accurate simulations were conducted and a number......Process analysis and simulations on molding experiments of 3D thin shell parts have been conducted. Moldings were carried out with polyoxymethylene (POM). The moldings were performed with cavity pressure sensors in order to compare experimental process results with simulations. The warpage...... was characterized by measuring distances using a tactile coordinate measuring machine (CMM). Molding simulations have been executed taking into account actual processing conditions. Various aspects have been considered in the simulation: machine barrel geometry, injection speed profiles, cavity injection pressure...

  14. Influence of mold surface temperature on polymer part warpage in rapid heat cycle molding (United States)

    Berger, G. R.; Pacher, G. A.; Pichler, A.; Friesenbichler, W.; Gruber, D. P.


    Dynamic mold surface temperature control was examined for its influence on the warpage. A test mold, featuring two different rapid heat cycle molding (RHCM) technologies was used to manufacture complex plate-shaped parts having different ribs, varying thin-wall regions, and both, circular and rectangular cut-outs. The mold's nozzle side is equipped with the areal heating and cooling technology BFMOLD®, where the heating/cooling channels are replaced by a ball-filled slot near the cavity surface flooded through with hot and cold water sequentially. Two local electrical ceramic heating elements are installed into the mold's ejection side. Based on a 23 full-factorial design of experiments (DoE) plan, varying nozzle temperature (Tnozzle), rapid heat cycle molding temperature (TRHCM) and holding pressure (pn), specimens of POM were manufactured systematically. Five specimens were examined per DoE run. The resulting warpage was measured at 6 surface line scans per part using the non-contact confocal topography system FRT MicroProf®. Two warpage parameters were calculated, the curvature of a 2nd order approximation a, and the vertical deflection at the profile center d. Both, the influence strength and the acting direction of the process parameters and their interactions on a and d were calculated by statistical analysis. Linear mathematical process models were determined for a and d to predict the warpage as a function of the process parameter settings. Finally, an optimum process setting was predicted, based on the process models and Microsoft Excel GRG solver. Clear and significant influences of TRHCM, pn, Tnozzle, and the interaction of TRHCM and pn were determined. While TRHCM was dominant close to the gate, pn became more effective as the flow length increased.

  15. Analysis of cavity pressure and warpage of polyoxymethylene thin walled injection molded parts: Experiments and simulations (United States)

    Guerrier, P.; Tosello, G.; Hattel, J. H.


    Process analysis and simulations on molding experiments of 3D thin shell parts have been conducted. Moldings were carried out with polyoxymethylene (POM). The moldings were performed with cavity pressure sensors in order to compare experimental process results with simulations. The warpage was characterized by measuring distances using a tactile coordinate measuring machine (CMM). Molding simulations have been executed taking into account actual processing conditions. Various aspects have been considered in the simulation: machine barrel geometry, injection speed profiles, cavity injection pressure, melt and mold temperatures, material rheological and pvT characterization. Factors investigated for comparisons were: injection pressure profile, short shots length, flow pattern, and warpage. A reliable molding experimental database was obtained, accurate simulations were conducted and a number of conclusions concerning improvements to simulation accuracy are presented regarding: pvT data, mesh, short shots, cavity pressure for process control validation as well as molding machine geometry modelling. Eventually, a methodology for improved molding simulations of cavity injection pressure, filling pattern and warpage was established.

  16. Application of Soft Computing for the Prediction of Warpage of Plastic Injection

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    Vijaya Kumar Reddy


    Full Text Available This paper deals with the development of accurate warpage prediction model for plastic injection molded parts using softcomputing tools namely, artificial neural networks and support vector machines. For training, validating and testing of thewarpage model, a number of MoldFlow (FE analyses have been carried out using Taguchi’s orthogonal array in the designof experimental technique by considering the process parameters such as mold temperature, melt temperature, packing pressure,packing time and cooling time. The warpage values were found by analyses which were done by MoldFlow PlasticInsight (MPI 5.0 software. The artificial neural network model and support vector machine regression model have beendeveloped using conjugate gradient learning algorithm and ANOVA kernel function respectively. The adequacy of the developedmodels is verified by using coefficient of determination. To judge the ability and efficiency of the models to predictthe warpage values absolute relative error has been used. The finite element results show, artificial neural network modelpredicts with high accuracy compared with support vector machine model.

  17. Development of a wafer warpage measurement technique using Moiré-based method. (United States)

    Hsieh, Hung-Lin; Huang, Yung-Guang; Tsai, Yu-Hsuan; Huang, Yao-Hui


    This paper reports on a novel technique for measuring wafer warpage, using the design concepts of moiré shift, digital moiré, autocollimator, and the scanning profiling method. The measurement system is divided into two parts: an optical moiré system and a phase analysis system. The optical arrangement can be adjusted to control the projection of a linear grating image onto the surface of a wafer to be reflected back into a CCD camera. The grating image acquired by the CCD camera is used for measurement whereas a reference grating image is obtained using the digital moiré method. By overlapping the two images of the measurement and the reference gratings, the corresponding moiré fringes are formed. The phase of the moiré fringes will change proportionally to the degree of warpage in the wafer, which can be measured by detecting variations in the phase shift of the moiré fringes in the scanning profile across the surface of the entire wafer. Measurement resolution can be controlled by adjusting the pitch size of the grating or the focal length of the focusing lens, or by adjusting the angle between the images of the measurement and reference gratings. Experiment results demonstrate that the proposed method is able to achieve an angular resolution of 0.2 μrad. As compared to the current warpage measurement techniques, the proposed method has the ability of high measurement resolution, high stability, and high flexibility.

  18. 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)


    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.

  19. Thermal Warpage Measurement of Electronic Packages by Shadow Moiré with Phase Stepping Technique

    Institute of Scientific and Technical Information of China (English)

    Yinyan Wang


    Phase-stepping technique is applied to the analysis of fringe patterns of shadow moiré of electronic packages.Sensitivity of the fringe pattern analysis is demonstrated to be significantly increased. Thermally induced warpage of electronic packages is successfully measured in real-time as the sample is driven through a simulated reflow process.The paper discusses the technique of phase stepping,noise filtering and its application to the shadow moiré method.Applications of the technology are presented.

  20. Investigation of multilayer printed circuit board (PCB) film warpage using viscoelastic properties measured by a vibration test (United States)

    Joo, Sung-Jun; Park, Buhm; Kim, Do-Hyoung; Kwak, Dong-Ok; Song, In-Sang; Park, Junhong; Kim, Hak-Sung


    Woven glass fabric/BT (bismaleimide triazine) composite laminate (BT core), copper (Cu), and photoimageable solder resist (PSR) are the most widely used materials for semiconductors in electronic devices. Among these materials, BT core and PSR contain polymeric materials that exhibit viscoelastic behavior. For this reason, these materials are considered to have time- and temperature-dependent moduli during warpage analysis. However, the thin geometry of multilayer printed circuit board (PCB) film makes it difficult to identify viscoelastic characteristics. In this work, a vibration test method was proposed for measuring the viscoelastic properties of a multilayer PCB film at different temperatures. The beam-shaped specimens, composed of a BT core, Cu laminated on a BT core, and PSR and Cu laminated on a BT core, were used in the vibration test. The frequency-dependent variation of the complex bending stiffness was determined using a transfer function method. The storage modulus (E‧) of the BT core, Cu, and PSR as a function of temperature and frequency were obtained, and their temperature-dependent variation was identified. The obtained properties were fitted using a viscoelastic model for the BT core and the PSR, and a linear elastic model for the Cu. Warpage of a line pattern specimen due to temperature variation was measured using a shadow Moiré analysis and compared to predictions using a finite element model. The results provide information on the mechanism of warpage, especially warpage due to temperature-dependent variation in viscoelastic properties.

  1. Effect of Quenching Medium on Mechanical Properties of Alloy Al7049-T6 and Lowering of its After-Machining Warpage (United States)

    Sani, Saeed Aliakbari; Feizabadi, Javad; Pourgharibshahi, Mohammad; Hashemi, Seyed Hamidreza


    Aluminum alloy Al 7049 is studied in state T6. Heat treatment of the specimens is performed in different quenching media (cold water, boiling water, aqueous polymer solutions). The mechanical properties and the Brinell hardness of the alloy are determined after different modes of heat treatment. Comparative analysis is used to find the maximum residual stresses responsible for warpage of the alloy after machining. The relation between the warpage and the dimensionless Biot number is obtained. Quenching modes removing the warpage in billets of Al7049 are determined.

  2. Arrayed SU-8 polymer thermal actuators with inherent real-time feedback for actively modifying MEMS’ substrate warpage (United States)

    Wang, Xinghua; Xiao, Dingbang; Chen, Zhihua; Wu, Xuezhong


    This paper describes the design, fabrication and characterization of a batch-fabricated micro-thermal actuators array with inherent real-time self-feedback, which can be used to actively modify micro-electro-mechanical systems’ (MEMS’) substrate warpage. Arrayed polymer thermal actuators utilize SU-8 polymer (a thick negative photoresist) as a functional material with integrated Ti/Al film-heaters as a microscale heat source. The electro-thermo-mechanical response of a micro-fabricated actuator was measured. The resistance of the Al/Ti film resistor varies obviously with ambient temperature, which can be used as inherent feedback for observing real-time displacement of activated SU-8 bumps (0.43 μm Ω-1). Due to the high thermal expansion coefficient, SU-8 bumps tend to have relatively large deflection at low driving voltage and are very easily integrated with MEMS devices. Experimental results indicated that the proposed SU-8 polymer thermal actuators (array) are able to achieve accurate rectification of MEMS’ substrate warpage, which might find potential applications for solving stress-induced problems in MEMS.

  3. Simulation of warpage induced by non-isothermal crystallization of co-polypropylene during the SLS process (United States)

    Amado, Antonio; Schmid, Manfred; Wegener, Konrad


    Polymer processing using Additive Manufacturing Technologies (AM) has experienced a remarkable growth during the last years. The application range has been expanding rapidly, particularly driven by the so-called consumer 3D printing sector. However, for applications demanding higher requirements in terms of thermo-mechanical properties and dimensional accuracy the long established AM technologies such as Selective Laser Sintering (SLS) do not depict a comparable development. The higher process complexity hinders the number of materials that can be currently processed and the interactions between the different physics involved have not been fully investigated. In case of thermoplastic materials the crystallization kinetics coupled to the shrinkage strain development strongly influences the stability of the process. Thus, the current investigation presents a transient Finite Element simulation of the warpage effect during the SLS process of a new developed polyolefin (co-polypropylene) coupling the thermal, mechanical and phase change equations that control the process. A thermal characterization of the material was performed by means of DSC, integrating the Nakamura model with the classical Hoffmann-Lauritzen theory. The viscoelastic behavior was measured using a plate-plate rheometer at different degrees of undercooling and a phase change-temperature superposition principle was implemented. Additionally, for validation porpoises the warpage development of the first sintered layers was captured employing an optical device. The simulation results depict a good agreement with experimental measurements of deformation, describing the high sensitivity of the geometrical accuracy of the sintered parts related to the processing conditions.

  4. Deformidade corneana em usuário de lente de contato portador de ceratocone: relato de caso Corneal warpage in contact lens wearer with keratoconus: a case report

    Directory of Open Access Journals (Sweden)

    César Lipener


    Full Text Available Introdução: Alterações topográficas podem ocorrer secundariamente ao uso de uso de lentes de contato duras ou gelatinosas. O termo "corneal warpage" é utilizado para denominar as deformidades corneanas causadas pelas lentes. O quadro topográfico da fase inicial do ceratocone pode ser muito parecido com o de um paciente com este quadro. Objetivo: Mostrar um paciente portador de ceratocone, usuário de lentes de contato rígida gás-permeável (RGP que desenvolveu quadro de "corneal warpage", diagnosticado e acompanhado por topografias e exames clínicos seriados. Relato de caso: O paciente é um engenheiro de 40 anos com diagnóstico de ceratocone bilateral há 12 anos, usando lentes RGP desde então. No primeiro exame em 5/95, a refração de OD foi impossível de se determinar e a ceratometria era maior que 60,00 D. Foi feita topografia, que se mostrou compatível com ceratocone, tendo sido adaptada uma lente Soper, com visão de 20/70. Após um ano, uma topografia de controle mostrou aumento da curvatura central e aplanamento da periferia inferior. O uso da lente foi suspenso e após 6 meses houve regressão das mudanças, tendo sido adaptadas novas lentes com melhor padrão e visão de 20/40. Discussão: O caso apresentado evidencia a ocorrência de deformidade corneana em um portador de ceratocone usuário de lente RGP. O autor discute a fisiopatologia e o diagnóstico clínico e topográfico do "corneal warpage", lembrando que a exemplo de pacientes normais, os pacientes com ceratocone podem apresentar estas alterações, que devem ser diferenciadas da própria evolução da doença.Introduction: Topographical alterations may occur as a secondary result of the use of hard or soft contact lenses. The expression corneal warpage is used to describe the corneal deformities caused by the lenses. Topographical map of initial keratoconus can be very similar to that of a patient with corneal warpage. Purpose: To describe a contact lens

  5. Differentiation of mild keratoconus from corneal warpage according to topographic inferior steepening based on corneal tomography data

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    Lia Florim Patrão

    Full Text Available ABSTRACT We report two cases of suspicious asymmetric bow tie and inferior steepening on topographic evaluations with reflection (Placido and projection (Scheimpflug. Rotating Scheimpflug corneal and anterior segment tomography (Oculus Pentacam HR, Wetzlar, Germany® was performed in the first case, with a maximal keratometric value (Kmax of 43.2 D and an overall deviation value from the Belin/Ambrósio Enhanced Ectasia Display (BAD-D of 1.76, which was observed in the study eye (OD. BAD-D was 6.59 in the fellow eye, which had clinical findings that were consistent with keratoconus stage 2. The second case presented with a Kmax of 45.3 D and BAD-D of 0.76 in OD and 1.01 in OS. This patient had discontinued wearing soft contact lens less than 1 day prior to examination. Corneal tomographic data enabled us to distinguish mild or forme fruste keratoconus from contact lens-induced corneal warpage, and similar findings were observed on curvature maps.

  6. Warpage controls of thin shell injection parts based on Taguchi method%基于正交法的薄壳类注塑产品翘曲变形控制

    Institute of Scientific and Technical Information of China (English)

    王晓花; 陈文琳; 周香


    文章以某电子产品薄壳类注塑件为研究对象,采用多因素正交试验的方法,对注塑成型过程进行有限元模拟,获得塑件在不同工艺参数下的整体翘曲变形量,并以整体翘曲量为考核指标,通过分析正交试验中的各因素对评价指标的影响,确定了ABS GP22材料塑料件优化的工艺参数组合。通过物理实验验证,效果良好,解决了塑件的翘曲变形缺陷,实现了理想的装配效果。%The injection process of a thin shell part was simulated by finite element method .Numerical experiments were designed according to Taguchi method .Injection quality was evaluated by the over‐all warpage .Optimal parameters for processing the material of ABS GP22 were determined by compa‐ring the influencing degree of different parameters on warpage deformation .The method could be used to optimize the injection molding .The experimental results showed that the warpage had been solved and desired assembly effect had been gotten .

  7. Study of Warpage in Injection MoldingUsing Rubber and Talc-filled Polypropylene— Influence of Molding Conditions on Corner Deformation — (United States)

    Takahara, Tadayoshi; Furuhashi, Hiroshi; Maeda, Hidenori; Inoyama, Tatsuya; Koyama, Kiyohito

    The most popular resin material for automotive plastic parts is polypropylene, which includes talc for stiffness and heat-resistance. The anisotropic thermal expansion coefficient is well documented for talc reinforced polypropylene, but there are almost no technical papers for warpage. Therefore, using this kind of material and molding with an "L" shaped cross section, the influence of molding conditions on corner deformation is discussed in this study. The results of this study are as follows 1) Shrinkage rate in the thickness direction is a few times larger than that in the planar direction (flow direction and transverse direction). By SEM observation, talc orientation for planar direction was confirmed. This talc orientation can hinder shrinkage in the planar direction, so the shrinkage rate in the thickness direction is relatively larger. 2) Three relationships were confirmed; negative correlation between injected weight (i.e. specimen weight) and shrinkage rate in the thickness direction, positive correlation between shrinkage rate in the thickness direction and corner deformation, and injected weight was varied by molding condition. From the results above, corner deformation is examined when; molding condition changes the injected weight, injected weight varies the shrinkage rate in the thickness direction, and when the shrinkage rate in the thickness direction induces corner deformation.

  8. 基于CAE的解决空调器大面罩塑件翘曲变形的设计优化%CAE-based Ameliorative Design for Solving Warpage on Big Plastic Veil of Air-Condition

    Institute of Scientific and Technical Information of China (English)



    以大型复杂的立式空调器出风大面罩塑件注塑模设计为例,分析了注塑成型的塑料制品发生翘曲变形的原因及相应的解决措施,并重点介绍了CAE软件Moldflow中翘曲变形分析模块的原理,通过Moldflow对产品进行注塑仿真模拟,分析浇口的位置和数量的变化等对制品翘曲的影响,从而得到最佳的浇口位置、数量、形状,有效解决该大型复杂塑件注塑模设计过程中容易出现的翘曲变形等问题,对大型复杂注塑模具设计和改善产品质量具有重要的指导意义.%With design of big and complicated plastic veil's injection mould of stand-up Air-condition as an example, this article analyzed the causation and resolving of warpage on plastic made by mould injection. The theory of warping analysis in Moldflow of CAE was emphatically introduced. By injection simulation on plastic using Moldflow and analyzing the effect of gate's location and number on warpage, getting the best location , number and form of gate accordingly. The problem of warpage on big and complicated plastic was effectively solved. It had important guiding significance not only on design of big and complicated injection mould, but also improving the quality of production.

  9. Study on warpage of a strip level power module in packaging assembly process%封装集成工艺中带状功率器件的翘曲研究

    Institute of Scientific and Technical Information of China (English)

    顾江海; 刘勇; 梁利华


    基于子结构法对封装集成工艺中带状功率器件的翘曲问题进行了研究,讨论了子结构法和非子结构法的优劣.采用实验性设计(Design of experiment,DoE),分别研究了嵌入式系统封装中低边芯片和高边芯片厚度、环氧模塑封(Epoxy mold compound,EMC)材料厚度、以及玻璃纤维(Prepreg)材料Z向弹性模量和EMC弹性模量对带状翘曲的影响.结果表明:子结构方法能够高效、简便和准确地模拟带状功率器件的翘曲问题;芯片、EMC厚度的变化对封装工艺中带状功率器件翘曲变形影响较大,Prepreg的Z向弹性模量和EMC的弹性模量E的变化对封装工艺中带状功率器件翘曲变形影响较小.%The warpage of a strip level power module in packaging assembly process is studied based on the substructure method. The comparison between substructure and non-substructure methods is made and discussed. By using design of experiment (DOE) method, the impact of low side (LS) and high side (HS) die thickness, epoxy mold compound (EMC) thickness, as well as the Young's modulus of prepreg and Young's modulus of EMC on the strip level warpage is conducted. It is found that substructure method is able to capture strip level power module warpage characteristics with high efficiency. The simulation results of substructure method agree reasonably well with non-substructure method. The numerical results show that die thickness and EMC thickness have an obvious impact on the warpage of a strip power modules, while the Young's modulus of prepreg and Young's modulus of EMC has less impact on it.

  10. 基于Taguchi方法的汽车后视镜壳体的翘曲分析%Analysis of Warpage of Car Rearview Mirror Shell Based on Taguchi Method

    Institute of Scientific and Technical Information of China (English)



    The car rearview mirror shell (ABS as material) as the research object, so as to reduce the forming process of warping deformation amount. Influence degree of injection conditions of mould temperature, melt temperature,filling time, holding pressure, holding time and cooling time on the warpage of injection-molded part is analyzed by experiment design of the Taguchi, and the injection molding process parameters are optimized to minimize the amount of warpage.%以汽车后视镜壳体[材料为丙烯腈-丁二烯-苯乙烯共聚物(ABS)]为研究对象,以减少成型过程的翘曲变形量为目标,采用Taguchi试验设计方法,在模具温度、熔体温度、注射时间、保压压力、保压时间和冷却时间等不同注射工艺条件下,对ABS后视镜壳体翘曲变形的影响程度进行了分析,并对注射成型工艺参数进行优化,使翘曲变形量达到最小.

  11. Warpage control of thin shell parts of injection-molded using taguchi method%基于正交优化的薄壳类注塑产品的翘曲控制

    Institute of Scientific and Technical Information of China (English)

    贾敬华; 尹红灵


    The injection process of a thin shell part was simulated by finite element method.Numerical experiments were designed according to taguchi method. Injection quality was evaluated by warpage. Optimal process parameters about the material of PC/ABS were determined on the basis of comparison of the influencing degree of the different parameters having on warpage deformation values. The method could be used to optimize the injection molding.%以某电子产品上盖薄壳类注塑件的翘曲变形量为考核指标,采用多因素正交试验法,利用有限元分析软件对注塑成型过程进行数值模拟,比较不同注塑工艺参数对翘曲变形量的影响,最终获得PC/ABS材料塑料件优化的工艺参数组合,该方法可应用于优化注塑工艺.

  12. Effect of Process Parameters on Warpage and Volumetric Shrinkage of Air Conditioning Fixed Circuit Board%工艺参数对空调电路固定板的翘曲变形和体积收缩的影响研究

    Institute of Scientific and Technical Information of China (English)

    周浩文; 李江平


    Taking air conditioning circuit fixed plate as research object, the warpage and volumetric shrinkage were obtained by using Taguchi orthogonal experimental design method with simulation of Moldflow software. Effects of process parameters on warping deformation and volume shrinkage were studied by average analysis and variance analysis, and ideal combination of optimum parameters was obtained.%以空调电路固定板为研究对象,结合Moldflow软件模拟和Taguchi正交试验设计得到对应制品的翘曲变形量和体积收缩率.采用均值分析和方差分析研究各参数对制品翘曲变形量和体积收缩率的影响程度,并获得较为理想的最佳工艺参数组合.

  13. Investigation of process induced warpage for pultrusion of a rectangular hollow profile

    NARCIS (Netherlands)

    Baran, I.; Hattel, Jesper H.; Akkerman, R.


    A novel thermo-chemical–mechanical analysis of the pultrusion process is presented. A process simulation is performed for an industrially pultruded rectangular hollow profile containing both unidirectional (UD) roving and continuous filament mat (CFM) layers. The reinforcements are impregnated with

  14. Homogenization on Multi-Materials’ Elements: Application to Printed Circuit Boards and Warpage Analysis

    Directory of Open Access Journals (Sweden)

    Araújo Manuel


    Full Text Available Multi-material domains are often found in industrial applications. Modelling them can be computationally very expensive due to meshing requirements. The finite element properties comprising different materials are hardly accurate. In this work, a new homogenization method that simplifies the computation of the homogenized Young modulus, Poisson ratio and thermal expansion coefficient is proposed, and applied to composite-like material on a printed circuit board. The results show a good properties correspondence between the homogenized domain and the real geometry simulation.

  15. Precision affecting factorsand warpage analysis of 3D printer%3D打印精度影响因素及翘曲分析

    Institute of Scientific and Technical Information of China (English)

    李金华; 张建李; 姚芳萍; 苏智超



  16. Study on Using Taguchi Methods to Optimize Warpage of Wing Mirror%利用TAGUCHI法优化后视镜翘曲变形的研究

    Institute of Scientific and Technical Information of China (English)

    王戈; 刘泓滨




    Institute of Scientific and Technical Information of China (English)

    陈元芳; 夏华; 刘春; 李六如



  18. Research on Warpage of Molded Plastic Parts with Stiffeners Based on Taguchi Method%基于Taguchi方法的带筋注塑件翘曲变形研究

    Institute of Scientific and Technical Information of China (English)

    徐小青; 孙庆东; 尹晨



  19. Warpage Optimization of Molded Part with Plastics Injection Based on Taguchi Method%基于Taguchi试验设计方法的注塑成型翘曲优化

    Institute of Scientific and Technical Information of China (English)

    吴真繁; 孙宝寿; 张勇



  20. Optimization of warpage for package-on-package (PoP) assembly based on Taguchi method%基于Taguchi 实验设计方法优化PoP的翘曲

    Institute of Scientific and Technical Information of China (English)

    颜学优; 李国元


    通过对PoP的翘曲进行优化分析,采用有限元分析方法分析了PoP中FBGA和PBGA的翘曲形变,并利用Taguchi设计和有限元模拟相结合的方法进行优化设计.分析结果表明:PBGA具有较大的翘曲,增加基板厚度和塑封料热膨胀系数,减小芯片大小和厚度可以改善PBGA的翘曲.对比优化前后的翘曲,在25 ℃时翘曲值从53.3 μm降到39.1 μm,260 ℃时翘曲值从-112 μm降到了-67.7 μm.塑封料热膨胀系数和芯片尺寸在优化翘曲中起着重要作用.

  1. 应用Taguchi实验设计法最小化ABS注塑制品翘曲变形量%Minimization of warpage of plastic injection molded parts of ABS by Taguchi method

    Institute of Scientific and Technical Information of China (English)

    杨风霞; 王天喜; 杨胜凯; 杨新兵


    运用Taguchi DOE技术研究了工艺参数对丙烯腈-丁二烯-苯乙烯共聚物(ABS)注塑制品翘曲变形的影响,并获得优化的工艺参数以使制品的翘曲变形量最小.文中以碱性蓄电池盖为例,利用L9(34)正交矩阵进行实验,并采用标准变量分析法(ANOVA)对熔体温度、注射时间、冷却时间、保压压力等工艺参数对制品翘曲变形的影响程度进行了研究,结果表明,在所选工艺参数中,保压压力和熔体温度对翘曲变形的影响程度最大.

  2. 基于 MOLDEX 3D手机外壳收缩翘曲变形分析及应用%Analysis of warpage deformation of mobile phone shell based on MOLDEX 3D

    Institute of Scientific and Technical Information of China (English)

    窦沙沙; 夏建生


    用MOLDEX 3D r9.0软件对手机外壳进行模流分析研究,发现流动不平衡、结合线的产生,保压效果不良和翘曲问题,提出三种修改方案并进行模拟对照,找出最佳方案,并在模具厂进行相应的验证.

  3. 人脸反求模型的注射成型翘曲变形分析与优化%Analysis and Optimization of Warpage on Injection Molding of Inverse Model of Face

    Institute of Scientific and Technical Information of China (English)

    严庆光; 孙存友; 范金


    A human face was studied and reverse engineering was used to make the measured three-dimensional face point cloud data to NURBS surface models against hope for success. Finite element method was used on human face to simulate the injection molding process simulation. The relevant process parameters affected the warping were optimized by using the orthogonal optimization method to get an optimal combination of the technological parameters. Simulation results revealed that it could obtain a nice face restoration by using the method, and effectively solved the preparation problem of human soft tissue restoration.%以人脸修复体为研究对象,应用逆向工程技术将测量所得的三维人脸点云数据反求成NURBS曲面模型,并用有限元方法对人脸修复体注射成型工艺进行模拟仿真分析.通过正交试验,对影响翘曲的相关工艺参数进行优化,从而获得最优工艺参数组合.结果表明,采用该方法能够获得良好的人脸修复体,有效解决了人体软组织修复体的制备问题.

  4. How to minimize CD variation and overlay degradation induced by film stress (United States)

    Jung, Woo-Yung; Lim, Yong-Hyun; Park, Shin-Ae; Ahn, Sang-Joon; Lee, Ji-Hyun; Yoo, Jung-A.; Pyi, Seung-Ho; Kim, Jin-Woong


    It is getting harder to minimize feature size to satisfy bit growth requirement. 3D NAND flash memory has been developed to meet bit growth requirement without shrinking feature size. To increase the number of memory cells per unit area without shrinking feature size, we should increase the number of stacked film layers which finally become memory cells. Wafer warpage is induced by the stress between film and wafer. Both of film stress and wafer warpage increase in proportion to stacked film layers, and the increase of wafer warpage makes CD uniformity worse. Overlay degradation has no relation with wafer warpage, but has indirect relation with film stress. Wafer deformation in film deposition chamber is the source of overlay degradation. In this paper, we study the reasons why CD uniformity and overlay accuracy are affected by film stress, and suggest the methods which keep CD uniformity and overlay accuracy safe without additional processes.

  5. Single gate optimization for plastic injection mold

    Institute of Scientific and Technical Information of China (English)

    LI Ji-quan; LI De-qun; GUO Zhi-ying; LV Hai-yuan


    This paper deals with a methodology for single gate location optimization for plastic injection mold. The objective of the gate optimization is to minimize the warpage of injection molded parts, because warpage is a crucial quality issue for most injection molded parts while it is influenced greatly by the gate location. Feature warpage is defined as the ratio of maximum displacement on the feature surface to the projected length of the feature surface to describe part warpage. The optimization is combined with the numerical simulation technology to find the optimal gate location, in which the simulated annealing algorithm is used to search for the optimum. Finally, an example is discussed in the paper and it can be concluded that the proposed method is effective.

  6. Numerically design the injection process parameters of parts fabricated with ramie fiber reinforced green composites (United States)

    Chen, L. P.; He, L. P.; Chen, D. C.; Lu, G.; Li, W. J.; Yuan, J. M.


    The warpage deformation plays an important role on the performance of automobile interior components fabricated with natural fiber reinforced composites. The present work investigated the influence of process parameters on the warpage behavior of A pillar trim made of ramie fiber (RF) reinforced polypropylene (PP) composites (RF/PP) via numerical simulation with orthogonal experiment method and range analysis. The results indicated that fiber addition and packing pressure were the most important factors affecting warpage. The A pillar trim can achieved the minimum warpage value as of 2.124 mm under the optimum parameters. The optimal process parameters are: 70% percent of the default value of injection pressure for the packing pressure, 20 wt% for the fiber addition, 185 °C for the melt °C for the mold temperature, 7 s for the filling time and 17 s for the packing time.

  7. Residual stresses in rubber formed thermoplastic composites

    NARCIS (Netherlands)

    Wijskamp, Sebastiaan; Lamers, E.A.D.; Akkerman, Remko; Brucato, V.


    The rubber pressing process is applied for the rapid production of thermoplastic composite products. However, rubber pressed products show geometrical distortions, such as warpage, due to processinduced residual stresses. An experimental study is performed to measure the curvature after rubber

  8. Effect of Stacking Layup on Spring-back Deformation of Symmetrical Flat Laminate Composites Manufactured through Autoclave Processing (United States)

    Nasir, M. N. M.; Seman, M. A.; Mezeix, L.; Aminanda, Y.; Rivai, A.; Ali, K. M.


    The residual stresses that develop within fibre-reinforced laminate composites during autoclave processing lead to dimensional warpage known as spring-back deformation. A number of experiments have been conducted on flat laminate composites with unidirectional fibre orientation to examine the effects of both the intrinsic and extrinsic parameters on the warpage. This paper extends the study on to the symmetrical layup effect on spring-back for flat laminate composites. Plies stacked at various symmetrical sequences were fabricated to observe the severity of the resulting warpage. Essentially, the experimental results demonstrated that the symmetrical layups reduce the laminate stiffness in its principal direction compared to the unidirectional laminate thus, raising the spring-back warpage with the exception of the [45/-45]S layup due to its quasi-isotropic property.

  9. Thermal cycling reliability of indirect hybrid HgCdTe infrared detectors (United States)

    Chen, Xing; He, Kai; Wang, Jian-xin; Zhang, Qin-yao


    Thermal cycling reliability is one of the most important issues whether the HgCdTe infrared focal plane array detectors can be applied to both military and civil fields. In this paper, a 3D finite element model for indirect hybrid HgCdTe infrared detectors is established. The thermal stress distribution and thermally induced warpage of the detector assembly as a function of the distance between the detector chip and Si-ROIC, the thickness and the materials properties of electrical lead board in cryogenic temperature are analyzed. The results show that all these parameters have influences on the thermal stress distribution and warpage of the detector assembly, especially the coefficient of thermal expansion(CTE) of electrical lead board. The thermal stress and warpage in the assembly can be avoided or minimized by choosing the appropriate electrical lead board. Additionally, the warpage of some indirect hybrid detectors assembly samples is measured in experiment. The experimental results are in good agreement with the simulation results, which verifies that the results are calculated by finite element method are reasonable.

  10. Residual thermal stresses in injection molded products

    NARCIS (Netherlands)

    Zoetelief, W.F.; Douven, L.F.A.; Ingen Housz, A.J.


    Nonisothermal flow of a polymer melt in a cold mold cavity introduces stresses that are partly frozen-in during solidification. Flow-induced stresses cause anisotropy of mechanical, thermal, and optical properties, while the residual thermal stresses induce warpage and stress-cracking. In this study

  11. Stabilizing stainless steel components for cryogenic service (United States)

    Holden, C. F.


    Warpage and creep in stainless steel valve components are decreased by a procedure in which components are machined to a semifinish and then cold soaked in a bath of cryogenic liquid. After the treatment they are returned to ambient temperature and machine finished to the final drawing dimensions.

  12. Residual stresses in injection molded products

    NARCIS (Netherlands)

    Jansen, K.M.B.


    During the molding process residual stresses are formed due to thermal contraction during cooling as well as the local pressure history during solidification. In this paper a simple analytical model is reviewed which relates residual stresses, product shrinkage as well as warpage to the temperature

  13. Effect of cure cycle on enthalpy relaxation and post shrinkage in neat epoxy and epoxy composites

    DEFF Research Database (Denmark)

    Jensen, Martin; Jakobsen, Johnny


    The effect of cure cycle on enthalpy relaxation and warpage is studied for both neat epoxy and glass/epoxy composites. An approach for determining the enthalpy relaxation in the matrix of composite materials combining modulated differential scanning calorimetry and thermogravimetry is presented...

  14. Thermally-induced shapes of rigid FR-4 electrical laminates (United States)

    Lyle, Phra Douglas

    In the process of a laminate cooling from the curing temperature to room temperature, a substantial level of thermal residual stresses develop. These residual thermal stresses arise due to the mismatch of the thermal expansion coefficient between lamina and between the reinforcing fibers and the matrix resin, generating warpage, or out of plane deformations, when the laminate is not symmetric about the midplane of the composite. Classical lamination theory has been used to predict the warped shape of an asymmetric laminate; this theory suggests that the cooled room temperature shape to be a stable anticlastic or saddle shape. In the 80s, nonlinear theories were developed in order to explain observations for (0/90) sbT cross-ply laminates that cool to a cylindrical shape and to predict the observed phenomena of an occasional "snap through" between two stable cylindrical shapes. Recently, the nonlinear approach has been successfully modified for the analysis of a square angle-ply laminate, allowing an even greater number of laminates to be evaluated. A rigid FR-4 electrical circuit board is a composite laminate that is designed to be symmetrical; however, after cooling from the press cycle or after cooling from other processing thermal excursions, warpage can occur. One potential cause for this warpage can be inadvertently introduced process or material nonuniformities. This investigation develops an FR-4 electrical laminate model that can transform selected material and process variations into input for the mechanical and thermal matrices required in the formulation of both classical lamination and the nonlinear theories. The output is the predicted warpage, for each theory, for each of the selected material and process variations. These warpage outputs are graphically displayed, quantified and compared for the classical lamination theory and for the four recent nonlinear theories. Also, the predicted warpage deformations are stack ranked in order to provide an

  15. Technical feasibility study on polycarbonate solar panels

    Energy Technology Data Exchange (ETDEWEB)

    Hackmann, M.M.; Meuwissen, M.H.H.; Bots, T.L.; Buijs, J.A.H.M. [TNO Industrial Technology, Eindhoven (Netherlands); Broek, K.M.; Kinderman, R. [Energy Research Center of the Netherlands, Petten (Netherlands); Tanck, O.B.F.; Schuurmans, F.M. [Shell Solar Energy, Helmond (Netherlands)


    This paper describes a technical feasibility study on the application of polycarbonate (PC) plates in a superstrate photovoltaic module design. The lamination process was performed in a conventional laminator apparatus using low temperature curing (100{sup o}C) ethylene-vinyl-acetate (EVA) as the potting material and multi-crystalline silicon-solar cells. Thermo-mechanical calculations via the finite element method were performed to support the experimental results on various layer set-ups. Both experimental and numerical results revealed that PC superstrate laminates display a certain degree of warpage after the lamination process. This warpage can be attributed to stress built up in the modules due to differences in thermal expansion between solar cells and PC. This stress build-up can be diminished by application of thicker layers of PC or EVA leading to less curved laminates. (author)

  16. Moiré fringe method of using warping deformation measurement of electronic components (United States)

    Huang, Yanping; Huang, Biaobing; Xu, Hongji; Yan, Dongmei; Li, Wenpeng


    Computers, mobile phones, cameras and video equipment and other electronic products, Moving in the light, thin, small, high speed, high reliability, multi-functional aspects of development, Namely, 3G technology and the SOC of. Therefore, the various components of the packaging technology have become increasingly demanding, Electronic components of residual stress after encapsulation and the use of temperature changes during, Body will be made electronic packaging warpage, Seriously affect the quality of the product. Therefore, to establish a set of micron, sub-micron-level detection method for testing. In this paper, Moiré fringe method to measure warpage of electronic packages body volume, Was first proposed application of Rayleigh-Sommerfeld diffraction theory, Proof presented in this paper with a small spacing diffraction grating problems arising from the assumption can be overcome, Greatly improved the precision deformation measurement of electronic components.

  17. Spring-back simulation of flat symmetrical laminates with angled plies manufactured through autoclave processing (United States)

    Nasir, M. N. M.; Aminanda, Y.; Mezeix, L.; Seman, M. A.; Rivai, A.; Ali, K. M.


    This paper presents a non-linear finite element analysis (FEA) method to predict the spring-back deformation for composite structures manufactured using autoclave processing. It is a progression from previous accompanying study on flat unidirectional samples and the aim is to observe spring-back warpage on laminates consisting of angled (±45°) plies compared to unidirectional (0°) laminate. Three samples for each of the symmetrical laminates with angled plies [45/0]S and [45/-45]S are manufactured and the warpage form is observed. FEA model that was utilized in the previous study, along with the physical mechanisms of spring-back such as the first ply stretching and tool-part interaction mechanisms, are maintained with only changes in material orientation for the part and the tool-part interface components. Upon comparison, the data shows that the spring-back form for symmetrical laminate becomes more complex to predict.

  18. IGBT Scaling Principle Toward CMOS Compatible Wafer Processes



    A scaling principle for trench gate IGBT is proposed. CMOS technology on large diameter wafer enables to produce various digital circuits with higher performance and lower cost. The transistor cell structure becomes laterally smaller and smaller and vertically shallower and shallower. In contrast, latest IGBTs have rather deeper trench structure to obtain lower on-state voltage drop and turn-off loss. In the aspect of the process uniformity and wafer warpage, manufacturing such structure in t...

  19. A hermetic sealing process for large irregularly shaped hybrid microcircuit enclosures (United States)

    Stahler, M. R.


    A system for sealing vacuum baked hybrids in a dry inert atmosphere using an overlapping spot resistance weld is described. A unique electrode configuration and fixturing that permits sealing of large and irregularly shaped gold plated Kovar packages to the hermeticity requirements of MIL-STD-883 was discussed. Metallurgical considerations and comparisons to laser sealing were made. Problems encountered during the development and optimization of the process were highlighted. Solutions to plating, fixturing, warpage, weld splatter and cracked bead problems are presented.

  20. Comparison of laboratory calibrations of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) at the beginning and end of the first flight season (United States)

    Vane, Gregg; Chrien, Thomas G.; Reimer, John H.; Green, Robert O.; Conel, James E.


    Spectral and radiometric calibrations of AVIRIS are described together with changes in instrument characteristics that occurred during the flight season. These changes include detachment of the optical fibers to two of the four AVIRIS spectrometers, degradation in the optical alignment of the spectrometers due to thermally induced and mechanical warpage, and breakage of a thermal blocking filter in one of the spectrometers. Means of improving the instrument are discussed.

  1. Metamodel-based design optimization of injection molding process variables and gates of an automotive glove box for enhancing its quality

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Gyung Ju [Pusan National University, Busan (Korea, Republic of); Park, Chang Hyun; Choi, Dong Hoon [Hanyang University, Seoul (Korea, Republic of)


    Injection molding process variables and gates of an automotive glove box were optimally determined to enhance its injection molding quality. We minimized warpage with satisfying constraints on clamp force, weldline, and profiles of filling and packing. Design variables concerning the injection molding process are temperatures of the mold and the resin, ram speeds, and packing pressures and durations; design variables concerning the gates are the shape of the center gate and locations of two side gates. To optimally determine the design variables in an efficient way, we adopted metamodel-based design optimization, sequentially using an optimal Latin hypercube design as a design of experiment, Kriging models as metamodels that replace time-consuming injection molding simulations, and a micro genetic algorithm as an optimization algorithm. In the optimization process, a commercial injection molding analysis software, MoldflowTM, was employed to evaluate the injection molding quality at design points specified. Using the proposed design approach, the warpage was found reduced by 20.5% compared to the initial warpage, while all the design constraints were satisfied, which clearly shows the validity of the proposed design approach.

  2. Estudo experimental do processo de rotomoldagem de PELBD: efeitos sobre a morfologia e estabilidade dimensional Experimental study of rotational molding process of LLDPE: effects on morphology and dimensional stability

    Directory of Open Access Journals (Sweden)

    Tiago Boni Comisso


    Full Text Available No presente estudo o empenamento de peças de polietileno linear de baixa densidade (PELBD moldadas por rotomoldagem foi investigado. O efeito de diferentes fatores como espessura da peça, taxa de resfriamento e diâmetro de tubo de ventilação foi avaliado. Além dos experimentos de rotomoldagem, uma técnica alternativa denominada "Hot Press" foi também aplicada para investigar o empenamento de dois diferentes PELBD sob condições típicas da rotomoldagem quanto ao resfriamento assimétrico. Cristalinidade e morfologia esferulítica ao longo da espessura das peças rotomoldadas foram avaliadas por Calorimetria Exploratória Diferencial (DSC e Microscopia Ótica de Luz Polarizada. Verificou-se que o grau de empenamento aumenta com a taxa de resfriamento. O aumento do diâmetro do tubo de ventilação é mais efetivo na redução do empenamento principalmente em menores taxas de resfriamento. Nos experimentos de "Hot Press" o PELBD com menor índice de fluidez e maior módulo de flexão apresentou menor empenamento. Nos experimentos de "Hot Press" a espessura das peças afetou o empenamento somente para maiores taxas de resfriamento. Em geral, a cristalinidade e o tamanho de esferulitos se mostraram menores nas posições ao longo da espessura das peças rotomodadas onde as taxas de resfriamento eram mais rápidas.In the present study the warpage of rotationally molded parts of a linear low density polyethylene (LLDPE was investigated. The effect from different processing factors such as part thickness, cooling condition and diameter of the venting tube was evaluated. In addition to the rotational molding experiments, an alternative experimental technique, referred to as "Hot Press", was also applied to investigate the warpage of two different grades of LLDPE under typical rotational molding conditions, which means slow cooling from only one side. The crystallinity and spherulitic morphology along the thickness of the rotationally molded

  3. Food packing optimization (United States)


    The development of a universal closure lid for the space shuttle food package is reported. The revised lid needs a folded configuration which, when unfolded, fully conforms to the interior surfaces of the food cup. Experimental thermoform molds were fabricated and test lids formed. The lid material not in contact with the food conformed to the cup interior without wrinkles, permitting full nesting of the cups. The final lid design was established and thermoform tooling designed and fabricated. Lids formed on these molds were tested for strength. The heating elements were replaced and repositioned to eliminate any hot spots which may cause warpage.

  4. Silicon epitaxy process recipe and tool configuration optimization (United States)

    Moy, W. H.; Cheong, K. Y.


    Silicon epitaxy is widely used in semiconductor fabrication due to its ability to produce high quality and low cost thin film. Epitaxy optimized process condition with respect to the process recipe and tool for the maximization of n-type epitaxial production has been investigated. For standard recipe of an epitaxy process, there are seven main steps, namely purge, ramp, bake, stab, deposition, post and cooling. This project focuses on the recipe optimization on ramp, bake and stab steps. For the tool configuration, cool-down step has been optimized. Impact on slip, haze, wafers warpage and crystal originated particles have been investigated.

  5. Combined macro-meso scale modeling of sintering. Part I: Continuum approach

    Energy Technology Data Exchange (ETDEWEB)



    An integrated approach, including a continuum theory of sintering and mesostructure evolution analysis, is used for the solution of the problem of bi-layered structure sintering. Two types of bi-layered structures are considered: layers of the same material different by initial porosity, and layers of two different materials. The effective sintering stress and the normalized bulk modulus for the bi-layer powder sintering are derived based on mesoscale simulations. The combined effect of the layers' porosity and differences in sintering rate on shrinkage and warpage is studied for both sintering on a rigid substrate and free sintering.

  6. Residual stresses in angleplied laminates and their effects on laminate behavior (United States)

    Chamis, C. C.


    NASA Lewis Research Center research in the field of composite laminate residual stresses is reviewed and summarized. The origin of lamination residual stresses, evidence of their presence, experimental methods for measuring them, and theoretical methods for predicting them are described. Typical results are presented which show the magnitudes of residual stresses in various laminates including hybrids and superhybrids, and in other complex composite components. Results are also presented which show the effects of lamination residual stresses on laminate warpage and on laminate mechanical properties including fracture stresses. Finally, the major findings and conclusions derived therefrom are summarized.

  7. Development of Integrated Simulation System for Plastic Injection Molding

    Institute of Scientific and Technical Information of China (English)

    CHENGXue-wen; LIDe-qun; ZHOUHua-min


    Numerical simulation of injection molding have had success in predicting the behavior of polymer melt in extremely complicated geometries. Most of the current numerical solutions are based on finite-element/finite-difference/boundary-element/volume-control methods and the surface model. This paper discusses the development of an integrated CAE system for injection molding in detail, and presents the mathematics for numerical simulation of filling, packing,cooling, stress and warpage in injection molding. The developed system named as HsCAE3D is introduced at the end.


    Institute of Scientific and Technical Information of China (English)


    The linear isothermo-viscoelastic constitutive equation is established according to the principle of viscoelastic mechanics. Given the boundary conditions of the temperature field, the linear themo-viscoelastic constitutive equation is established acording to the analysis of the thermorheologically simple. The stress analysis model is constructed on the base of some reasonable hypotheses which consider the restraint conditions of mold and the characteristics of injection molding in the post-filling stage. The mathematical model is calculated by the finite difference method. The results can help to predict the warpage of plastic products.

  9. Surface Waviness in Grinding of Thin Mould Insert Using Chilled Air as Coolant

    Institute of Scientific and Technical Information of China (English)

    Yeo; S; H; K; Ramesh


    On going trend of miniaturization in electronic rel at ed parts, which is an average of two times in every 5~7 years introduce grindin g challenges. In grinding process, the surface waviness control of thin parts is an ardent task due to its warpage, induced by the high specific grinding energy (2~10 J/mm 3). Therefore, coolant is often used to avoid thermal damage, obtai n better surface integrity and to prolong wheel life. However coolant, the incomp ressibility media introduce high forces at the gri...

  10. Combined macro-meso scale modeling of sintering. Part II, Mesoscale simulations

    Energy Technology Data Exchange (ETDEWEB)



    A mesoscale kinetic Monte Carlo model is presented to simulate microstructural evolution during sintering of 2D complex microstructures which evolves by grain growth, pore migration and densification. No assumptions about the geometry of the evolving microstructure are made. The results of these simulations are used to generate sintering stress and normalize viscous bulk modulus for use in continuum level simulation of sintering. The advantage of these simulations is that they can be used to generate more accurate parameters as various assumptions regarding geometry and transport mechanism are made. The previous companion paper used the results from the mesoscale simulations to simulate shrinkage and warpage in sintering of bilayer ceramics.

  11. Disposable micro-fluidic biosensor array for online parallelized cell adhesion kinetics analysis on quartz crystal resonators

    DEFF Research Database (Denmark)

    Cama, G.; Jacobs, T.; Dimaki, Maria


    In this contribution we present a new disposable micro-fluidic biosensor array for the online analysis of adherent Madin Darby canine kidney (MDCK-II) cells on quartz crystal resonators (QCRs). The device was conceived for the parallel cultivation of cells providing the same experimental conditions...... molding process was simulated in order to optimize the mold geometry and minimize the shrinkage and the warpage of the parts. MDCK-II cells were cultivated in the biosensor array. Parallel cultivation of cells on the gold surface of the QCRs led to first observations of the impact of the cell distribution...

  12. Material quality development during the automated tow placement process (United States)

    Tierney, John Joseph

    Automated tow placement (ATP) of thermoplastic composites builds on the existing industrial base for equipment, robotics and kinematic placement of material with the aim of further cost reduction by eliminating the autoclave entirely. During ATP processing, thermoplastic composite tows are deposited on a preconsolidated substrate at rates ranging from 10--100mm/s and consolidated using the localized application of heat and pressure by a tow placement head mounted on a robot. The process is highly non-isothermal subjecting the material to multiple heating and cooling rates approaching 1000°C/sec. The requirement for the ATP process is to achieve the same quality in seconds (low void content, full translation of mechanical properties and degree of bonding and minimal warpage) as the autoclave process achieves in hours. The scientific challenge was to first understand and then model the relationships between processing, material response, microstructure and quality. The important phenomena affecting quality investigated in this study include a steady state heat transfer simulation, consolidation and deconsolidation (void dynamics), intimate contact and polymer interdiffusion (degree of bonding/mechanical properties) and residual stress and warpage (crystallization and viscoelastic response). A fundamental understanding of the role of materials related to these mechanisms and their relationship to final quality is developed and applied towards a method of process control and optimization.

  13. Optimization of Injection Molding Process Parameters of Automotive Interior Parts Based on Taguchi DOE and Moldflow%基于Taguchi DOE和Moldflow的汽车内饰件注射成型工艺参数优化

    Institute of Scientific and Technical Information of China (English)

    孙蒙蒙; 丁武学; 曹春平; 杨成福


    Taking a large-scale automotive plastic part as an example, Taguchi DOE and Moldflow numerical simulation technology were conducted to study the influence of process parameters on volume shrinkage variation and warpage, which were regarded as quality optimal set of the parameters was obtained based on different levels. As formula predicted and numerical simulation proved, the optimal set of the parameters made volume shrinkage variation and warpage minimum during experimental range%以某汽车大型塑料件为例,以体积收缩率变化及翘曲量为质量指标,结合Taguchi DOE及Moldflow数值模拟技术,研究相关工艺参数对质量指标的影响,并得到了各工艺参数水平的最优组合.经公式预测及Moldflow数值模拟验证,工艺参数的优化组合使体积收缩率变化和翘曲量达到试验范围内最小.

  14. Bi-directional homogenization equivalent modeling for the prediction of thermo-mechanical properties of a multi-layered printed circuit board (PCB) (United States)

    Joo, Sung-Jun; Park, Buhm; Kim, Do-Hyoung; Kwak, Dong-Ok; Park, Junhong; Kim, Hak-Sung


    Warpage of multi-layered printed circuit boards (PCB) during the reflow process is a serious problem which affects the reliability of solder ball connections between the PCB and the mounted semi-conductor packages in electronic devices. It is essential to predict the warpage of the PCB accurately; however, the complicated copper patterns in multi-layered PCBs render a full modeling analysis impossible due to the excessive computing time required. To overcome this problem, we have developed analytical equations of three Cu patterns (line, square, and grid) for the application of thermo-mechanical properties simply by equivalent modeling of Cu patterns. In the proposed equations, the effect of thermo-viscoelastic properties as well as the influence of surrounding layers such as woven glass fabric/BT (bismaleimide triazine), composite laminate (BT core), and photoimageable solder resist (PSR) were considered. To verify the developed equations, vibration tests based on the wave propagation approach were performed at various temperatures. Good agreement was observed between the equivalent model and the experimental results.

  15. Effects of process parameters on the molding quality of the micro-needle array (United States)

    Qiu, Z. J.; Ma, Z.; Gao, S.


    Micro-needle array, which is used in medical applications, is a kind of typical injection molded products with microstructures. Due to its tiny micro-features size and high aspect ratios, it is more likely to produce short shots defects, leading to poor molding quality. The injection molding process of the micro-needle array was studied in this paper to find the effects of the process parameters on the molding quality of the micro-needle array and to provide theoretical guidance for practical production of high-quality products. With the shrinkage ratio and warpage of micro needles as the evaluation indices of the molding quality, the orthogonal experiment was conducted and the analysis of variance was carried out. According to the results, the contribution rates were calculated to determine the influence of various process parameters on molding quality. The single parameter method was used to analyse the main process parameter. It was found that the contribution rate of the holding pressure on shrinkage ratio and warpage reached 83.55% and 94.71% respectively, far higher than that of the other parameters. The study revealed that the holding pressure is the main factor which affects the molding quality of micro-needle array so that it should be focused on in order to obtain plastic parts with high quality in the practical production.

  16. Simulation of mechanical behavior and optimization of simulated injection molding process for PLA based antibacterial composite and nanocomposite bone screws using central composite design. (United States)

    Heidari, Behzad Shiroud; Oliaei, Erfan; Shayesteh, Hadi; Davachi, Seyed Mohammad; Hejazi, Iman; Seyfi, Javad; Bahrami, Mozhgan; Rashedi, Hamid


    In this study, injection molding of three poly lactic acid (PLA) based bone screws was simulated and optimized through minimizing the shrinkage and warpage of the bone screws. The optimization was carried out by investigating the process factors such as coolant temperature, mold temperature, melt temperature, packing time, injection time, and packing pressure. A response surface methodology (RSM), based on the central composite design (CCD), was used to determine the effects of the process factors on the PLA based bone screws. Upon applying the method of maximizing the desirability function, optimization of the factors gave the lowest warpage and shrinkage for nanocomposite PLA bone screw (PLA9). Moreover, PLA9 has the greatest desirability among the selected materials for bone screw injection molding. Meanwhile, a finite element analysis (FE analysis) was also performed to determine the force values and concentration points which cause yielding of the screws under certain conditions. The Von-Mises stress distribution showed that PLA9 screw is more resistant against the highest loads as compared to the other ones. Finally, according to the results of injection molding simulations, the design of experiments (DOE) and structural analysis, PLA9 screw is recommended as the best candidate for the production of biomedical materials among all the three types of screws.

  17. 田口方法及其在注塑成型中的应用%Taguchi method and its application in inj ection molding

    Institute of Scientific and Technical Information of China (English)

    茆茂; 朱先琦


    Taguchi method is introduced and the inj ection molding process parameters are optimized by combining the parameter design method with Moldflow(a simulation software)and Hypermesh(a finite element software).This article studies the influence of inj ection molding process parameters on the warp-age by taking the water segregator in an electrical appliance as an example.The optional parameter com-bination gained from the experiment can greatly reduce the warpage.%本文介绍了田口方法,并将参数设计法、CAE模拟仿真软件 Moldflow和有限元前处理软件 Hypermesh相结合,对注塑成型工艺参数进行优化。以某电器内的洗涤分水器为例,研究了注塑工艺参数对翘曲变形的影响,实验得出的最佳参数组合可以极大减少翘曲变形。

  18. Determination of the structural capabilities of thermoformed and blow-molded components (United States)

    Hummel, Scott Randall

    In the thermoforming processes, a polymer membrane is heated well above the glass transition temperature and forced into a mold. This is accomplished by applying a pressure differential where the pressure on the non-mold side of the membrane is higher than that of the mold side. Upon contact with the mold surface, the polymer is rapidly cooled and subsequently removed from the mold. During the process, stresses are induced into the polymer that must be included in the determination of the load bearing capabilities of the component. Moreover, the stresses are the cause of significant undesirable warpage. In this investigation, the residual stress and warpage of a thermoformed component made from ABS (Acrylonitrile Butadiene Styrene) plastic were investigated. The research was both experimental and theoretical in nature in that the viscoelastic material behavior first had to be measured experimentally, followed by correlation to a finite strain constitutive model. A finite element analysis of the thermoforming process was also performed. To facilitate measuring the viscoelastic behavior of the polymer, a heated tensile testing machine was constructed. This machine was equipped with a high speed digital data acquisition and control system to obtain the stress and strain data during rapid stretching. The data obtained from the testing was correlated to a non-linear finite strain viscoelastic material model. The constitutive model used was time-strain separable and was a viscoelastic generalization of rubber elasticity. Results for both the Moony-Rivlin and the five-term polynomial strain energy functions are presented. Stress relaxation experiments were also carried out and the results are given at a variety of temperatures. Once the constitutive behavior of the polymer was determined, a finite element analysis was performed to model the inflation of the polymer into a simple mold. The final thickness distribution of the formed component and the stresses upon contact

  19. Thermoplastics as engineering materials: The mechanics, materials, design, processing link

    Energy Technology Data Exchange (ETDEWEB)

    Stokes, V.K. [GE Corporate Research and Development, Schenectady, NY (United States). Engineering Mechanics Lab.


    While the use of plastics has been growing at a significant pace because of weight reduction, ease of fabrication of complex shapes, and cost reduction resulting from function integration, the engineering applications of plastics have only become important in the past fifteen years. An inadequate understanding of the mechanics issues underlying the close coupling among the design, the processing (fabrication), and the assembly with these materials is a barrier to their use in structural applications. Recent progress on some issues relating to the engineering uses of plastics is surveyed, highlighting the need for a better understanding of plastics and how processing affects the performance of plastic parts. Topics addressed include the large deformation behavior of ductile resins, fiber orientation in chopped-fiber filled materials, structural foams, random glass mat composites, modeling of thickness distributions in blow-molded and thermoformed parts, dimensional stability (shrinkage, warpage, and residual stresses) in injection-molded parts, and welding of thermoplastics.

  20. Study of a Compression-Molding Process for Ultraviolet Light-Emitting Diode Exposure Systems via Finite-Element Analysis. (United States)

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


    Although wafer-level camera lenses are a very promising technology, problems such as warpage with time and non-uniform thickness of products still exist. In this study, finite element simulation was performed to simulate the compression molding process for acquiring the pressure distribution on the product on completion of the process and predicting the deformation with respect to the pressure distribution. Results show that the single-gate compression molding process significantly increases the pressure at the center of the product, whereas the multi-gate compressing molding process can effectively distribute the pressure. This study evaluated the non-uniform thickness of product and changes in the process parameters through computer simulations, which could help to improve the compression molding process.

  1. 基于Moldflow的塑料伞柄注射模设计%Moldflow-based design of injection mould for plastic umbrella handle

    Institute of Scientific and Technical Information of China (English)



    Analysis software Moldflow was used to study the filling time, injection pressure, volume shrinkage of melt plastics, and the weld lines and warpage deformation of the product in the injection molding of a plastic umbrella handle. The mould design scheme was optimized based on the simulation result.%以塑料伞柄注射模设计为例,通过分析软件Moldflow对塑料熔体充模时间、注射压力、体积收缩率以及塑件熔接痕和翘曲变形等进行模拟分析,并根据模拟结果优化模具设计方案,从而提高塑件质量,节约模具开发时间和成本.

  2. Stress-warping relation in thin film coated wafers (United States)

    Schicker, J.; Khan, W. A.; Arnold, T.; Hirschl, C.


    A misfit strain or stress in a thin layer on the surface of a wafer lets the composite disk warp. When the wafer is thin and large, the Stoney estimation of the film stress as function of the curvature yields large errors. We present a nonlinear analytical model that describes the relationship between warpage and film stress on an anisotropic wafer, and give evidence for its suitability for large thin wafers by a comparison to finite element results. Finally, we show the confidence limit of the Stoney estimation and the benefit by the nonlinear model. For thin coatings, it can be succesfully used even without knowledge of the film properties, which was the main advantage of the Stoney estimation.

  3. Springback analysis of thermoplastic composite plates

    Directory of Open Access Journals (Sweden)

    Stavrovský V.


    Full Text Available Residual stresses, which are set in the fiber reinforced composites during the laminate curing in a closed form, lead to dimensional changes of composites after extracting from the form and cooling. One of these dimensional changes is called “springback” of the angle sections. Other dimensional changes are warpage of flat sections of composite or displacement of single layers of composite for example. In our case four different lay-ups were analysed (three symmetrical and one unsymmetrical. An analytical model which covers temperature changes, chemical shrinkage during curing and moisture change was used. Also a FEM analysis was done for predicting the springback, and both calculations were compared with the measured data from manufacturer.

  4. Recursive Heaviside step functions and beginning of the universe (United States)

    Shin, Changsoo; Kim, Seongjai


    This article introduces recursive Heaviside step functions, as a potential of the known universe, for the first time in the history of mathematics, science, and engineering. In modern cosmology, various bouncing models have been suggested based on the postulation that the current universe is the result of the collapse of a previous universe. However, all Big Bounce models leave unanswered the question of what powered inflation. Recursive Heaviside step functions are analyzed to represent the warpage of spacetime during the crunch-bounce transition. In particular, the time shift appeared during the transition is modeled in the form of recursive Heaviside step functions and suggested as a possible answer for the immeasurable energy appeared for the Big Bounce.

  5. A PLL Synthesizer with Learning Repeatable Fluctuation of Input Signal (United States)

    Ono, Hiroyuki

    This paper describes a high frequency PLL (Phase Locked Loop) synthesizer with a function of learning then eliminating repeatable fluctuation of timing intervals on series input pulses. Typical spindle encoder generates digital pulses according to the revolution speed. The intervals of each pulse have repeatable fluctuation every revolution by eccentricity or warpage of the encoder scale disk. This method provides a programmable counter for the loop counter of PLL circuit and an interval counter with memory in order to learn the repeatable fluctuation. After the learning process, the PLL generates very pure tone clock signal based on the real flutter components of the spindle revolution speed without influenced by encoder errors. This method has been applied to a hard disk test system in order to generate 3GHz read/write clock.

  6. Repair weld induced residual stresses in thick-walled steel pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Smith, G.C.; Holz, P.P.


    If a flaw requiring corrective action were to be found in an operating nuclear pressure vessel, there would be considerable safety and economic implications. Should such a flaw be found, one possible corrective action would be an in situ repair weld. A repair of this type would presumably involve grinding away material in a region encompassing the flaw and then filling the resulting cavity with weld metal. Thermal stress relieving under those conditions could lead to serious difficulties associated with thermal expansion and warpage and would therefore most likely be avoided. Such a departure from normal procedure raises questions relating to residual stresses and material toughness levels which would have to be assessed before a repair could be recommended or approved. The residual stress measurements reported are intended to provide baseline information to aid in an assessment should such a repair ever have to be seriously considered.


    Directory of Open Access Journals (Sweden)

    Afshin Kheidari Monfared


    Full Text Available Welding is a crucial manufacturing process and widely used for manufacturing various products including ships, automobiles, trains and bridges. Welding distortions often occur in welded structures of thin plates due to relatively low stiffness and result in their warpage during assembly process and high manufacturing cost. Therefore, prediction and reduction of welding distortions are important in order to improve quality of welded structures. Welding distortion during the assembly process is caused not only by local shrinkage due to rapid heating and cooling. 3-D thermo-elastic-plastic finite element method (FEM has been used to simulate single-bead-on-plate welding with 1 mm thickness. Experiments have been carried out to prove the simulated results. Comparison of the experimental results and FEM simulation results has confirmed that the proposed method efficiently  predicts level of  welding distortions while making single-bead-on-plate welding with 1 mm thickness.

  8. Comparative analysis of different process simulation settings of a micro injection molded part featuring conformal cooling

    DEFF Research Database (Denmark)

    Marhöfer, David Maximilian; Tosello, Guido; Islam, Aminul


    different simulation models are established: a version including the part without the surrounding mold block, an advanced version including the mold block and conventional cooling channels, and a third version alike the second with additional conformal cooling for efficient thermal management...... of the implementation of the actual mold block, conventional cooling, and conformal cooling. In the comparison, characteristic quality criteria for injection molding are studied, such as the filling behavior of the cavity, the injection pressure, the temperature distribution, and the resulting part warpage....... Additionally, the analysis of the cooling channels exploiting computational fluid dynamics is introduced as helpful tool for the mold design process. It is observed that the comprehensive implementation of the actual injection molding system and conditions is highly relevant at sub-mm/micro dimensional scales...

  9. Cellular scanning strategy for selective laser melting: Generating reliable, optimized scanning paths and processing parameters

    DEFF Research Database (Denmark)

    Mohanty, Sankhya; Hattel, Jesper Henri


    Selective laser melting is yet to become a standardized industrial manufacturing technique. The process continues to suffer from defects such as distortions, residual stresses, localized deformations and warpage caused primarily due to the localized heating, rapid cooling and high temperature...... gradients that occur during the process. While process monitoring and control of selective laser melting is an active area of research, establishing the reliability and robustness of the process still remains a challenge.In this paper, a methodology for generating reliable, optimized scanning paths...... and process parameters for selective laser melting of a standard sample is introduced. The processing of the sample is simulated by sequentially coupling a calibrated 3D pseudo-analytical thermal model with a 3D finite element mechanical model.The optimized processing parameters are subjected to a Monte Carlo...

  10. Within-wafer CD variation induced by wafer shape (United States)

    Huang, Chi-hao; Yang, Mars; Yang, Elvis; Yang, T. H.; Chen, K. C.


    In order to meet the increasing storage capacity demand and reduce bit cost of NAND flash memories, 3D stacked vertical flash cell array has been proposed. In constructing 3D NAND flash memories, the bit number per unit area is increased as increasing the number of stacked layers. However, the increased number of stacked layers has made the film stress control extremely important for maintaining good process quality. The residual film stress alters the wafer shape accordingly several process impacts have been readily observed across wafer, such as film deposition non-uniformity, etch rate non-uniformity, wafer chucking error on scanner, materials coating/baking defects, overlay degradation and critical dimension (CD) non-uniformity. The residual tensile and compressive stresses on wafers will result in concave and convex wafer shapes, respectively. This study investigates within-wafer CD uniformity (CDU) associated with wafer shape change induced by the 3D NAND flash memory processes. Within-wafer CDU was correlated with several critical parameters including different wafer bow heights of concave and convex wafer shapes, photo resists with different post exposure baking (PEB) temperature sensitivities, and DoseMapper compensation. The results indicated the trend of within-wafer CDU maintains flat for convex wafer shapes with bow height up to +230um and concave wafer shapes with bow height ranging from 0 ~ -70um, while the within-wafer CDU trends up from -70um to -246um wafer bow heights. To minimize the within-wafer CD distribution induced by wafer warpage, carefully tailoring the film stack and thermal budget in the process flow for maintaining the wafer shape at CDU friendly range is indispensable and using photo-resist materials with lower PEB temperature sensitivity is also suggested. In addition, DoseMapper compensation is also an alternative to greatly suppress the within-wafer CD non-uniformity but the photo-resist profile variation induced by across

  11. Research of High-gloss Injection Molding Technology in Thin Shell Plastic Parts with Holes%薄壳多孔塑料件高光注射成型工艺研究

    Institute of Scientific and Technical Information of China (English)

    赵苗; 黄翔; 辛勇


    对手机壳体塑料件进行了常规注射成型CAE研究,分析存在较为严重的表现质量问题.通过采用高光成型技术,以沉降指数、体积收缩率和翘曲变形为质量指标,利用正交试验和多目标综合平衡法分析研究得出该产品的最佳成型工艺参数组合.分析结果表明,高光注射成型技术在改善薄壳多孔塑料件缺陷方面比常规注射成型有着更大的优越性.%CAE research of conventional injection moulding on a mobile phone shell was carried out and the serious apparent quality problems were analyzed.Then through high-gloss injection molding technology, selecting sink index, volumetric shrinkage and warpage as the main quality indexes, the optimum injection molding parameters combination was obtained by using orthogonal experiment and multi-objective integral balance method.The analysis results showed that high-gloss injection molding had more advantages in improving defects of thin shell injection molding parts with holes compared with conventional injection molding.High-gloss injection molding ; thin shell injection molding parts with holes ; orthogonal experiment design;

  12. Mo-Al{sub 2}O{sub 3} cermet research and development

    Energy Technology Data Exchange (ETDEWEB)

    Glass, S.J.; Monroe, S.L.; Stephens, J.J.; Moore, R.H. [and others


    This report describes the results to date of a program that was initiated to predict and measure residual stresses in Mo-Al{sub 2}O{sub 3} cermet-containing components and to develop new materials and processes that would lead to the reduction or elimination of the thermal mismatch stresses. The period of performance includes work performed CY95-97. Excessive thermal mismatch stresses had produced cracking in some cermet-containing neutron tube components. This cracking could lead to a loss of hermeticity or decreased tube reliability. Stress predictions were conducted using finite element models of the various components, along with the thermal coefficient of expansion (CTE), Young`s modulus, and strength properties. A significant portion of the program focused on the property measurements for the existing cermet materials, processing conditions, and the measurement technique. The effects of differences in the properties on the predicted residual stresses were calculated for existing designs. Several potential approaches were evaluated for reducing the residual stresses and cracking in cermet-containing parts including reducing the Mo content of the cermet, substituting a ternary alloy with a better CTE match with alumina, and substituting Nb for Mo. Processing modifications were also investigated for minimizing warpage that occurs during sintering due to differential sintering. These modifications include changing the pressing of the 94ND2 alumina and changing to a 96% alumina powder from AlSiMag.

  13. Tailoring the heat transfer on the injection moulding cavity by plasma sprayed ceramic coatings (United States)

    Bobzin, K.; Hopmann, Ch; Öte, M.; Knoch, M. A.; Alkhasli, I.; Dornebusch, H.; Schmitz, M.


    Inhomogeneous material shrinkage in injection moulding can cause warpage in thermoplastic components. To minimise the deformations of the injection moulding parts, the heat transfer during the cooling phase can be adjusted according to the local cooling demand on the surface of the mould cavity by means of plasma sprayed coatings with locally variable thermal resistance over the surface of the mould. Thermal resistance is a function of thermal conductivity and thickness of the coatings, where thermal conductivity of thermal barrier coatings can be adjusted by altering the chemical composition and the microstructure, which is depending on the thickness. This work evaluates the application of plasma sprayed coatings with variable thickness as thermal barrier coatings in the mould cavity. The thermal resistance of the coating and thereby the heat transfer from the melt into the mould will be influenced locally by varying the coating thickness over the cavity area according to the local cooling demand. Using the laser flash method, the thermal conduction of coatings with different thicknesses will be determined. On the basis of the experimentally determined thermal conduction, the effect of the coatings on the temperature field of the mould cavity will be numerically calculated and the required thickness distribution of the coating for an optimal temperature gradient will be determined.

  14. Single crystalline silicon solar cells with rib structure (United States)

    Yoshiba, Shuhei; Hirai, Masakazu; Abe, Yusuke; Konagai, Makoto; Ichikawa, Yukimi


    To improve the conversion efficiency of Si solar cells, we have developed a thin Si wafer-based solar cell that uses a rib structure. The open-circuit voltage of a solar cell is known to increase with deceasing wafer thickness if the cell is adequately passivated. However, it is not easy to handle very thin wafers because they are brittle and are subject to warpage. We fabricated a lattice-shaped rib structure on the rear side of a thin Si wafer to improve the wafer's strength. A silicon nitride film was deposited on the Si wafer surface and patterned to form a mask to fabricate the lattice-shaped rib, and the wafer was then etched using KOH to reduce the thickness of the active area, except for the rib region. Using this structure in a Si heterojunction cell, we demonstrated that a high open-circuit voltage (VOC) could be obtained by thinning the wafer without sacrificing its strength. A wafer with thickness of 30 μm was prepared easily using this structure. We then fabricated Si heterojunction solar cells using these rib wafers, and measured their implied VOC as a function of wafer thickness. The measured values were compared with device simulation results, and we found that the measured VOC agrees well with the simulated results. To optimize the rib and cell design, we also performed device simulations using various wafer thicknesses and rib dimensions.

  15. Development of Equivalent Material Properties of Microbump for Simulating Chip Stacking Packaging

    Directory of Open Access Journals (Sweden)

    Chang-Chun Lee


    Full Text Available three-dimensional integrated circuit (3D-IC structure with a significant scale mismatch causes difficulty in analytic model construction. This paper proposes a simulation technique to introduce an equivalent material composed of microbumps and their surrounding wafer level underfill (WLUF. The mechanical properties of this equivalent material, including Young’s modulus (E, Poisson’s ratio, shear modulus, and coefficient of thermal expansion (CTE, are directly obtained by applying either a tensile load or a constant displacement, and by increasing the temperature during simulations, respectively. Analytic results indicate that at least eight microbumps at the outermost region of the chip stacking structure need to be considered as an accurate stress/strain contour in the concerned region. In addition, a factorial experimental design with analysis of variance is proposed to optimize chip stacking structure reliability with four factors: chip thickness, substrate thickness, CTE, and E-value. Analytic results show that the most significant factor is CTE of WLUF. This factor affects microbump reliability and structural warpage under a temperature cycling load and high-temperature bonding process. WLUF with low CTE and high E-value are recommended to enhance the assembly reliability of the 3D-IC architecture.

  16. Study of Thermally Enhanced 2.5D Packages with Multi-chips Molded on Silicon Interposer (United States)

    Zhang, H. Y.; Zhang, X. W.


    The 2.5D package with distributed vias on silicon interposer has received great attention due to its potential for heterogeneous integration. The overmolded 2.5D package protects the silicon die and interposer from environmental damage, which, on the other hand, induces undesirable thermal resistance due to low thermal conductivity of the molding compound. In this paper, a thermally enhanced 2.5D package with exposed die is proposed, fabricated and examined from the thermal enhancement viewpoint. The high power thermal test die was first assembled on a silicon interposer with through silicon vias and connected to the substrate, which was followed by the overmolding and back-grinding processes to form the partially molded (PM) package with exposed die for direct heat sink attachments. Experiments were conducted to examine the thermal performance under different thermal conditions. Under natural convection without thermal enhancement, there was no performance difference between the PM package and the overmolded package. However, when the package top was mounted with a thermally enhanced structure such as a pin fin heat sink, the thermal resistance of PM package was significantly reduced. The advantage was more prominent with the attachment of a high performance liquid cooling heat sink. Thermal simulation models were also constructed to examine the thermal performances under different test conditions, and the realistic thermal interface resistance of 0.5 Kcm2/W was estimated based on the package warpage. The computed thermal resistances agreed with measurement results.

  17. Risk reduction in dimension inspection of the plastic injection-molded parts from mechatronic devices by using optical 3D measuring techniques

    Directory of Open Access Journals (Sweden)

    Braga Ion Cristian


    Full Text Available As of the definition presented by Harashima, Tomizuka, and Fukada in 1996, the mechatronics is the synergistic combination of precision mechanical engineering, electronic control and systems thinking in the design of products and manufacturing processes. The most of the mechatronic devices need the precise dimensions of the plastic parts, as long as the combination of those parts leads to a final haptic characteristic defined within specific limits or when the certain travel way is linked with an electrical contact. The increasing of the risks to produce bad mechatronic devices are directly related to the combination of the plastic injectionmolded parts out of different cavities. The paper’s aim is to present reducing of the risks to have bad final parts assembled with the components out of plastic injection-molded parts by using optical 3D measuring techniques at first validation of the parts out of the tool and setting parameters in the injection machines. The shrinkage and the warpage are more easily detected in that way and this will support first article inspection, but also during the entire production process. A case study presents the analysis of the data coming from the measurements of the plastic parts from each cavity and the combination of those parts, by using the ATOS inspection software. The CAD data are compared with the measured ones and the differences will be visible in the colored plotted areas, also the differences of the parts out of distinct cavities will be also displayed by overlaying of the measurements.

  18. The Effect of Heat Treatment on Residual Stress and Machining Distortions in Advanced Nickel Base Disk Alloys (United States)

    Gayda, John


    This paper describes an extension of NASA's AST and IDPAT Programs which sought to predict the effect of stabilization heat treatments on residual stress and subsequent machining distortions in the advanced disk alloy, ME-209. Simple "pancake" forgings of ME-209 were produced and given four heat treats: 2075F(SUBSOLVUS)/OIL QUENCH/NO AGE; 2075F/OIL QUENCH/1400F@8HR;2075F/OIL QUENCH/1550F@3HR/l400F@8HR; and 2160F(SUPERSOLVUS)/OIL QUENCH/1550F@3HR/ 1400F@8HR. The forgings were then measured to obtain surface profiles in the heat treated condition. A simple machining plan consisting of face cuts from the top surface followed by measurements of the surface profile opposite the cut were made. This data provided warpage maps which were compared with analytical results. The analysis followed the IDPAT methodology and utilized a 2-D axisymmetric, viscoplastic FEA code. The analytical results accurately tracked the experimental data for each of the four heat treatments. The 1550F stabilization heat treatment was found to significantly reduce residual stresses and subsequent machining distortions for fine grain (subsolvus) ME209, while coarse grain (supersolvus) ME209 would require additional time or higher stabilization temperatures to attain the same degree of stress relief.

  19. Improving focus performance at litho using diffraction-based focus metrology, novel calibration methods, interface, and control loop (United States)

    Hu, Jiarui; Chen, Y. L.; Chen, K. H.; Lee, Brian; Tsai, Frankie; Ke, C. M.; Liao, C. H.; Ngo, Desmond; Gosali, Benny; Tijssen, Robin; Huang, Vincent; Tu, Ward; Noot, Marc; Escalante Marun, Maryana; Leewis, Christian; Luijten, Carlo; Staals, Frank; Van Veen, Martijn; Furthner, Francois; Young, Stuart; Bhattacharyya, Kaustuve


    In advanced optical lithography the requirements of focus control continues to tighten. Usable depth of focus (DoF) is already quite low due to typical sources of focus errors, such as topography, wafer warpage and the thickness of photoresist. And now the usable DoF is further decreased by hotspots (design and imaging hotspots). All these have put extra challenges to improve focus metrology, scanner focus stability calibrations and on-product correction mechanisms. Asymmetric focus targets are developed to address robustness in focus measurements using diffraction-based focus (DBF and μDBF) metrology. A new layout specific calibration methodology is introduced for baseline focus setup and control in order to improve scanner focus uniformity and stability using the measurements of the above mentioned asymmetric targets. A similar metrology is also used for on product focus measurements. Moreover, a few novel alternative methods are also investigated for on-product focus measurements. Data shows good correlation between DBF and process on record (POR) method using traditional FEM. The new focus calibration demonstrated robustness, stability and speed. This technical publication will report the data from all the above activities including results from various product layers.

  20. Compensation Method for Die Shift Caused by Flow Drag Force in Wafer-Level Molding Process

    Directory of Open Access Journals (Sweden)

    Simo Yeon


    Full Text Available Wafer-level packaging (WLP is a next-generation semiconductor packaging technology that is important for realizing high-performance and ultra-thin semiconductor devices. However, the molding process, which is a part of the WLP process, has various problems such as a high defect rate and low predictability. Among the various defect factors, the die shift primarily determines the quality of the final product; therefore, predicting the die shift is necessary to achieve high-yield production in WLP. In this study, the die shift caused by the flow drag force of the epoxy molding compound (EMC is evaluated from the die shift of a debonded molding wafer. Experimental and analytical methods were employed to evaluate the die shift occurring during each stage of the molding process and that resulting from the geometrical changes after the debonding process. The die shift caused by the EMC flow drag force is evaluated from the data on die movements due to thermal contraction/expansion and warpage. The relationship between the die shift and variation in the die gap is determined through regression analysis in order to predict the die shift due to the flow drag force. The results can be used for die realignment by predicting and compensating for the die shift.

  1. Thermal behavior in the LENS process

    Energy Technology Data Exchange (ETDEWEB)

    Griffith, M.L.; Schlienger, M.E.; Harwell, L.D. [and others


    Direct laser metal deposition processing is a promising manufacturing technology which could significantly impact the length of time between initial concept and finished part. For adoption of this technology in the manufacturing environment, further understanding is required to ensure robust components with appropriate properties are routinely fabricated. This requires a complete understanding of the thermal history during part fabrication and control of this behavior. This paper will describe research to understand the thermal behavior for the Laser Engineered Net Shaping (LENS) process, where a component is fabricated by focusing a laser beam onto a substrate to create a molten pool in which powder particles are simultaneously injected to build each layer. The substrate is moved beneath the laser beam to deposit a thin cross section, thereby creating the desired geometry for each layer. After deposition of each layer, the powder delivery nozzle and focusing lens assembly is incremented in the positive Z-direction, thereby building a three dimensional component layer additively. It is important to control the thermal behavior to reproducibly fabricate parts. The ultimate intent is to monitor the thermal signatures and to incorporate sensors and feedback algorithms to control part fabrication. With appropriate control, the geometric properties (accuracy, surface finish, low warpage) as well as the materials` properties (e.g., strength, ductility) of a component can be dialed into the part through the fabrication parameters. Thermal monitoring techniques will be described, and their particular benefits highlighted. Preliminary details in correlating thermal behavior with processing results will be discussed.

  2. Reduction of image-based ADI-to-AEI overlay inconsistency with improved algorithm (United States)

    Chen, Yen-Liang; Lin, Shu-Hong; Chen, Kai-Hsiung; Ke, Chih-Ming; Gau, Tsai-Sheng


    In image-based overlay (IBO) measurement, the measurement quality of various measurement spectra can be judged by quality indicators and also the ADI-to-AEI similarity to determine the optimum light spectrum. However we found some IBO measured results showing erroneous indication of wafer expansion from the difference between the ADI and the AEI maps, even after their measurement spectra were optimized. To reduce this inconsistency, an improved image calculation algorithm is proposed in this paper. Different gray levels composed of inner- and outer-box contours are extracted to calculate their ADI overlay errors. The symmetry of intensity distribution at the thresholds dictated by a range of gray levels is used to determine the particular gray level that can minimize the ADI-to-AEI overlay inconsistency. After this improvement, the ADI is more similar to AEI with less expansion difference. The same wafer was also checked by the diffraction-based overlay (DBO) tool to verify that there is no physical wafer expansion. When there is actual wafer expansion induced by large internal stress, both the IBO and the DBO measurements indicate similar expansion results. The scanning white-light interference microscope was used to check the variation of wafer warpage during the ADI and AEI stages. It predicts a similar trend with the overlay difference map, confirming the internal stress.

  3. New method and uncertainty estimation for plate dimensions and surface measurements (United States)

    Ali, Salah H. R.; Buajarern, Jariya


    Dimensional and surface quality for tile plate manufacturing control is facing difficult engineering challenges. One of these challenges being that plates in large-scale mass production contain geometrically uneven surfaces. There is a traditional measurement method used to assess the tile plate dimensions and surface quality based on standard specifications: ISO-10545-2: 1995, EOS-3168-2: 2007 and TIS 2398-2:2008. A new measurement method of the dimensions and surface quality for ceramic oblong large-scale tile plate has been developed compared to the traditional method. The strategy of the proposed method is based on CMM straightness measurement strategy instead of the centre point in the traditional method. Expanded uncertainties budgets in the measurements of each method have been estimated in detail. The capability of accurate estimations of real actual results of centre of curvature (CC), centre of edge (CE), warpage (W) and edge crack defects parameters has been achieved according to standards. Moreover, the obtained results showed not only a more accurate method but also improved the quality of tile plate products significantly.

  4. New Measurement Method and Uncertainty Estimation for Plate Dimensions and Surface Quality

    Directory of Open Access Journals (Sweden)

    Salah H. R. Ali


    Full Text Available Dimensional and surface quality for plate production control is facing difficult engineering challenges. One of these challenges is that plates in large-scale mass production contain geometric uneven surfaces. There is a traditional measurement method used to assess the tile plate dimensions and surface quality based on standard specifications: ISO-10545-2: 1995, EOS-3168-2: 2007, and TIS 2398-2: 2008. A proposed measurement method of the dimensions and surface quality for ceramic oblong large-scale tile plate has been developed compared to the traditional method. The strategy of new method is based on CMM straightness measurement strategy instead of the centre point in the traditional method. Expanded uncertainties budgets in the measurements of each method have been estimated in detail. The capability of accurate estimations of real actual results for centre of curvature (CC, centre of edge (CE, warpage (W, and edge crack defects parameters has been achieved according to standards. Moreover, the obtained results not only showed better accurate new method but also improved the quality of plate products significantly.

  5. Carbon fiber-reinforced cyanate ester/nano-ZrW2O8 composites with tailored thermal expansion. (United States)

    Badrinarayanan, Prashanth; Rogalski, Mark K; Kessler, Michael R


    Fiber-reinforced composites are widely used in the design and fabrication of a variety of high performance aerospace components. The mismatch in coefficient of thermal expansion (CTE) between the high CTE polymer matrix and low CTE fiber reinforcements in such composite systems can lead to dimensional instability and deterioration of material lifetimes due to development of residual thermal stresses. The magnitude of thermally induced residual stresses in fiber-reinforced composite systems can be minimized by replacement of conventional polymer matrices with a low CTE, polymer nanocomposite matrix. Zirconium tungstate (ZrW(2)O(8)) is a unique ceramic material that exhibits isotropic negative thermal expansion and has excellent potential as a filler for development of low CTE polymer nanocomposites. In this paper, we report the fabrication and thermal characterization of novel, multiscale, macro-nano hybrid composite laminates comprising bisphenol E cyanate ester (BECy)/ZrW(2)O(8) nanocomposite matrices reinforced with unidirectional carbon fibers. The results reveal that incorporation of nanoparticles facilitates a reduction in CTE of the composite systems, which in turn results in a reduction in panel warpage and curvature after the cure because of mitigation of thermally induced residual stresses.

  6. Gastroresistant capsular device prepared by injection molding. (United States)

    Zema, Lucia; Loreti, Giulia; Melocchi, Alice; Maroni, Alessandra; Palugan, Luca; Gazzaniga, Andrea


    In the present work, the possibility of manufacturing by injection molding (IM) a gastro-resistant capsular device based on hydroxypropyl methyl cellulose acetate succinate (HPMCAS) was investigated. By performing as an enteric soluble container, such a device may provide a basis for the development of advantageous alternatives to coated dosage forms. Preliminarily, the processability of the selected thermoplastic polymer was evaluated, and the need for a plasticizer (polyethylene glycol 1500) in order to counterbalance the glassy nature of the molded items was assessed. However, some critical issues related to the physical/mechanical stability (shrinkage and warpage) and opening time of the device after the pH change were highlighted. Accordingly, an in-depth formulation study was carried out taking into account differing release modifiers potentially useful for enhancing the dissolution/disintegration rate of the capsular device at intestinal pH values. Capsule prototypes with thickness of 600 and 900 μm containing Kollicoat(®) IR and/or Explotab(®) CLV could be manufactured, and a promising performance was achieved with appropriate gastric resistance in pH 1.2 medium and break-up in pH 6.8 within 1h. These results would support the design of a dedicated mold for the development of a scalable manufacturing process.

  7. Investigation of the effect of rapidly solidified braze ribbons on the microstructure of brazed joints (United States)

    Bobzin, K.; Öte, M.; Wiesner, S.; Rochala, P.; Mayer, J.; Aretz, A.; Iskandar, R.; Schwedt, A.


    Shrinkage and warpage due to melting and solidification are crucial for the geometric precision of related components. In order to assure a high geometric precision, the formation of the microstructure in the joint during brazing must be taken into consideration. An extensive interaction can occur between liquid melt and base material, resulting in the formation of distinctive phases. This interaction depends on the parameters of the brazing process. However, the consequences of the interaction between phase formation and process parameters in terms of geometric precision cannot be estimated yet. Insufficient quality of the joint can be a result. In this study, investigations focus on the process of solidification in terms of time dependent diffusion behavior of elements. Therefore, microcrystalline and amorphous braze ribbons based on Ti are produced by rapid solidification and are used for joining. The microstructure of the braze ribbons as well as the melting behavior and phase formation during brazing are considered to be of particular importance for the mechanical properties of the brazed components.

  8. Thickness-Independent Ultrasonic Imaging Applied to Abrasive Cut-Off Wheels: An Advanced Aerospace Materials Characterization Method for the Abrasives Industry. A NASA Lewis Research Center Technology Transfer Case History (United States)

    Roth, Don J.; Farmer, Donald A.


    Abrasive cut-off wheels are at times unintentionally manufactured with nonuniformity that is difficult to identify and sufficiently characterize without time-consuming, destructive examination. One particular nonuniformity is a density variation condition occurring around the wheel circumference or along the radius, or both. This density variation, depending on its severity, can cause wheel warpage and wheel vibration resulting in unacceptable performance and perhaps premature failure of the wheel. Conventional nondestructive evaluation methods such as ultrasonic c-scan imaging and film radiography are inaccurate in their attempts at characterizing the density variation because a superimposing thickness variation exists as well in the wheel. In this article, the single transducer thickness-independent ultrasonic imaging method, developed specifically to allow more accurate characterization of aerospace components, is shown to precisely characterize the extent of the density variation in a cut-off wheel having a superimposing thickness variation. The method thereby has potential as an effective quality control tool in the abrasives industry for the wheel manufacturer.

  9. Influence of Rubber Concentration on Angular deformation in Injection Molded Parts of Talc and Rubber Filled Polypropylene (United States)

    Takahara, Tadayoshi; Koyama, Kiyohito

    The most popular resin material for automotive plastic parts is polypropylene, which includes talc for stiffness and heat-resistance and rubber for impact-resistance. The anisotropic thermal expansion coefficient is well documented for talc reinforced polypropylene, but there are very few technical papers for warpage. Therefore, using this kind of material and molding with an L-shaped cross section, the influence of rubber concentration on corner deformation was discussed in this study. The results of this study are as follows 1) L-shaped cross section specimens show that the corner deformation increases linearly in proportion to the increase of rubber concentration. 2) Plane shape specimens show that the shrinkage rates in the planar direction decrease linearly and the shrinkage rates in the thickness direction increase linearly. 3) The strains in each rubber concentration are calculated using Hooke's Law. This force that induces corner deformation is assumed as the shrinkage difference between the planar and thickness directions. The tendencies of calculated strains are qualitatively consistent with measured corner deformations. 4) The reason why corner deformation decreases linearly to rubber concentration is due to the fact that the shrinkage difference between the planar and thickness directions increases and the fact that the flexural modulus decreases linearly.

  10. Effect of organic additives on mechanical properties of SiC ceramics prepared by a modified gelcasting method

    Directory of Open Access Journals (Sweden)

    Feng Wang


    Full Text Available A novel and simple gel system of isobutylene and maleic anhydride (PIBM was used to prepare SiC ceramics. The rheological behaviour of the SiC slurries was investigated as function of organic additives. The SiC slurries with 0.2 wt.% PIBM and 0.2 wt.% tetramethylammonium hydroxide (TMAH showed low viscosity, which was favourable for casting SiC green bodies. In order to obtain homogeneous green bodies, polyvinyl alcohol (PVA was used to assist the dispersion of carbon black in the slurries, and polyethylene glycol (PEG was added to inhibit the surface exfoliation of green bodies. The content of PVA was controlled carefully to avoid the warpage of green bodies during the drying process. Finally, homogeneous defect-free SiC green bodies were successfully fabricated via aqueous gelcasting. The SiC ceramics sintered at 2100 °C (prepared from slurries with solid content of 60 wt.% showed an average flexural strength of 305.7 MPa with porosity of 19.92%.

  11. Processing of Syndiotactic Polystyrene to Microspheres for Part Manufacturing through Selective Laser Sintering

    Directory of Open Access Journals (Sweden)

    Nicolas Mys


    Full Text Available Syndiotactic polystyrene pellets were processed into powder form using mechanical (ball milling, rotor milling and physicochemical (spray drying techniques with the intention of using it as feed material for selective laser sintering. New materials are an important component in broadening the application window for selective laser sintering but must meet strict requirements to be used. Particles obtained were characterized in size and shape using SEM imaging, analyzed by software, and compared to the product obtained by conventional ball milling. Rotor milling and spray drying proved capable of making spherical powders, yet only rotor milling achieved particles with a mean diameter within the desired range of 45–97 µm. Subsequently, the obtained powders were examined for the effect each processing technique imparts on the intrinsic properties of the material. Differential scanning calorimetry analysis revealed amorphization for all methods and a reduction in crystallinity after processing, however, the reduction in crystallinity was acceptably low for the spray-dried and rotor-milled powders. Ball milling displayed an exceptional reduction in crystallinity, suggesting severe degradation. As a final test, the rotor-milled powder was subjected to single-layer test and displayed good coalescence and smooth morphology, albeit with a large amount of warpage.

  12. Durability of Poly(Methyl Methacrylate) Lenses Used in Concentrating Photovoltaic Modules: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Miller, D. C.; Gedvilas, L. M.; To, B.; Kennedy, C. E.; Kurtz, S. R.


    Concentrating photovoltaic (CPV) technology has recently gained interest based on their expected low levelized cost of electricity, high efficiency, and scalability. Many CPV systems use Fresnel lenses made of poly(methyl methacrylate)(PMMA) to obtain a high optical flux density. The optical and mechanical durability of such components, however, are not well established relative to the desired service life of 30 years. Specific reliability issues may include: reduced optical transmittance, discoloration, hazing, surface erosion, embrittlement, crack growth, physical aging, shape setting (warpage), and soiling. The initial results for contemporary lens- and material-specimens aged cumulatively to 6 months are presented. The study here uses an environmental chamber equipped with a xenon-arc lamp to age specimens at least 8x the nominal field rate. A broad range in the affected characteristics (including optical transmittance, yellowness index, mass loss, and contact angle) has been observed to date, depending on the formulation of PMMA used. The most affected specimens are further examined in terms of their visual appearance, surface roughness (examined via atomic force microscopy), and molecular structure (via Fourier transform infrared spectroscopy).

  13. Experimental analysis of artificial dragonfly wings using black graphite and fiberglass for use in Biomimetic Micro Air Vehicles (BMAVs

    Directory of Open Access Journals (Sweden)

    Nair Praveena


    Full Text Available This article examines the suitability of two different materials which are black graphite carbon fiber and red pre-impregnated fiberglass from which to fabricate artificial dragonfly wing frames. These wings could be of use in Biomimetic Micro Aerial Vehicles (BMAV. BMAV are a new class of unmanned micro-sized air vehicles that mimic flying biological organisms. Insects, such as dragonflies, possess corrugated and complex vein structures that are difficult to mimic. Simplified dragonfly wing frames were fabricated from these materials and then a nano-composite film was adhered to them, which mimics the membrane of an actual dragonfly. Experimental analysis of these results showed that although black graphite carbon fiber and red pre-impregnated fiberglass offer some structural advantages, red pre-impregnated fiberglass was a less preferred option due to its warpage and shrinking effects. Black graphite carbon fiber with its high load bearing capability is a more suitable choice for consideration in future BMAV applications.

  14. 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


    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...

  15. Reliability evaluation of CIF (chip-in-flex) and COF (chip-on-flex) packages (United States)

    Jang, Jae-Won; Suk, Kyoung-Lim; Paik, Kyung-Wook; Lee, Soon-Bok


    CIF (chip-in-flex) and COF (chip-on-flex) packages have the advantages of fine pitch capability, and flexibility. Anisotropic conductive films (ACFs) are used for the interconnection between chip and substrate. Display, mobile device, and semiconductor industry require for smaller and more integrated packages. Both CIF and COF packages are an alternative for the demands. However, there are some reliability problems of interconnection between the chip and substrate because the packages are subjected to various loading conditions. These may degrade the functionality of the packages. Therefore, reliability assessment of both packages is necessary. In this study, experimental tests were performed to evaluate the reliability of interconnection between the chip and substrate of CIF and COF packages. Thermal cycling tests were performed to evaluate the resistance against thermal fatigue. The shape and warpage of the chip of CIF and COF packages were observed using optical methods (e.g., shadow Moiré and Twyman/Green interferometry). These optical Moiré techniques are widely used for measuring small deformations in microelectronic packages. The stress distribution around the chip was evaluated through FEA (finite element analysis). In addition, we suggested modifying design parameter of CIF packages for the reliability enhancement.

  16. Single crystalline silicon solar cells with rib structure

    Directory of Open Access Journals (Sweden)

    Shuhei Yoshiba


    Full Text Available To improve the conversion efficiency of Si solar cells, we have developed a thin Si wafer-based solar cell that uses a rib structure. The open-circuit voltage of a solar cell is known to increase with deceasing wafer thickness if the cell is adequately passivated. However, it is not easy to handle very thin wafers because they are brittle and are subject to warpage. We fabricated a lattice-shaped rib structure on the rear side of a thin Si wafer to improve the wafer’s strength. A silicon nitride film was deposited on the Si wafer surface and patterned to form a mask to fabricate the lattice-shaped rib, and the wafer was then etched using KOH to reduce the thickness of the active area, except for the rib region. Using this structure in a Si heterojunction cell, we demonstrated that a high open-circuit voltage (VOC could be obtained by thinning the wafer without sacrificing its strength. A wafer with thickness of 30 μm was prepared easily using this structure. We then fabricated Si heterojunction solar cells using these rib wafers, and measured their implied VOC as a function of wafer thickness. The measured values were compared with device simulation results, and we found that the measured VOC agrees well with the simulated results. To optimize the rib and cell design, we also performed device simulations using various wafer thicknesses and rib dimensions.

  17. Optimal Design of POM Spin Coating Pallets%POM匀胶托盘的优化设计

    Institute of Scientific and Technical Information of China (English)

    魏存露; 花国然; 王强


    Polyformaldehyde (POM) spin coating pallet was taken as research object,which widely applied in spin coating film process. For the defects of existing POM spin coating pallet,the numerical simulation and experimental studies were carried out,the results indicate that substrate warpage deformation makes photoresist penetrate into spin coater during the use of the spiral spin coating pallet,and the cavity spin coating pallet substrate deformation is too large. Based on the analysis result,the shower cav-ity spin coating pallet is put forward and it is constituted by cavity spin pallet and shower cavity spin coating pallet end cover through interference fit,the numerical simulation resules show that shower cavity spin coating pallet could maintain cavity spin coating pal-let resist photoresist effect and substrate maximum deformation is about 2.7μm,compared with the spiral spin coating pallet,it decreases by about 3.9μm,and the warpage deformation at the substrate edge is small,about 0.17μm. The shower cavity spin coating pallet is mamufactured based on 3D printing technology,experiments analysis were carried out,the results show that the substrate deformation is good agreement with the change rule of the simulation value,and the maximum error of the same position deformation value is about 9.8%,which indicates that the simulation results are reliable.%以广泛应用于旋涂功能薄膜工艺中的聚甲醛(POM)匀胶托盘为研究对象,基于数值仿真及实验研究,对现有POM托盘工作中的缺陷进行了分析,结果表明,螺旋托盘基片因发生翘曲形变而易使胶体渗入匀胶机,腔式托盘基片形变量过大.基于分析结果,对现有匀胶托盘进行了优化,提出一种腔式花洒型托盘,其通过过盈配合,在腔式托盘上装配花洒型端盖,数值模拟结果表明,腔式花洒型托盘在保持腔式托盘阻胶结构的基础上,基片最大形变量为2.7μm,与螺旋托盘相比降低了3.9μm左右,且基片边

  18. Finite Element Analysis on Thermo-Mechanical Reliability of LQFP and eLQFP%LQFP和eLQFP热机械可靠性的有限元分析

    Institute of Scientific and Technical Information of China (English)

    夏国峰; 秦飞; 朱文辉; 马晓波; 高察


    The reliability of microelectronic packages is closely related with package type. Based on the finite element method, warpage, stress on chip and die attach as well as interfacial stresses of low-profile quad flat package (LQFP) and exposed-pad low-profile quad flat package (eLQFP) at room temperature and reflowing temperature were comparatively investigated. The results show that the warpage of LQFP is larger than that of eLQFP, and the package difference has little influence on the stress of chip and die attach. The interfacial stresses along epoxy moding compound (EMC) /chip interface for eLQFP are higher than that for LQFP. And the interfacial shear stresses for eLQFP along chip/die attach interface and die attach/chip pad interface are higher than that for LQFP. However, the interfacial peeling stresses present opposite situation. The interfacial stresses along EMC/silver plated chip pad interface for eLQFP are higher than that for LQFP, due to the intrinsic weak adhesion between EMC and silver plated chip pad. The interfacial delamination is more prone to occur for eLQFP compared with LQFP.%封装形式的差异性对产品可靠性具有重要影响.基于有限元法,对比分析了薄型四方扁平封装(LQFP)和载体外露薄型四方扁平封装(eLQFP)在室温和回流焊温度下的翘曲、芯片和粘片胶的应力水平以及各材料界面应力分布.研究表明,LQFP的翘曲比eLQFP的大,但芯片和粘片胶上的最大应力无明显差别;eLQFP在塑封材料与芯片有源面界面的应力水平比LQFP的大;eLQFP在芯片与粘片胶界面、粘片胶与芯片载体界面的剪切应力比LQFP的大,但eLQFP在芯片与粘片胶界面、粘片胶与芯片载体界面的剥离应力比LQFP的小;eLQFP在塑封材料与芯片载体镀银区界面的应力水平高于LQFP的应力水平,由于塑封材料与镀银芯片载体的结合强度弱,eLQFP更易发生界面分层.

  19. Novel in situ mechanical testers to enable integrated metal surface micro-machines.

    Energy Technology Data Exchange (ETDEWEB)

    Follstaedt, David Martin; de Boer, Maarten Pieter; Kotula, Paul Gabriel; Hearne, Sean Joseph; Foiles, Stephen Martin; Buchheit, Thomas Edward; Dyck, Christopher William


    The ability to integrate metal and semiconductor micro-systems to perform highly complex functions, such as RF-MEMS, will depend on developing freestanding metal structures that offer improved conductivity, reflectivity, and mechanical properties. Three issues have prevented the proliferation of these systems: (1) warpage of active components due to through-thickness stress gradients, (2) limited component lifetimes due to fatigue, and (3) low yield strength. To address these issues, we focus on developing and implementing techniques to enable the direct study of the stress and microstructural evolution during electrodeposition and mechanical loading. The study of stress during electrodeposition of metal thin films is being accomplished by integrating a multi-beam optical stress sensor into an electrodeposition chamber. By coupling the in-situ stress information with ex-situ microstructural analysis, a scientific understanding of the sources of stress during electrodeposition will be obtained. These results are providing a foundation upon which to develop a stress-gradient-free thin film directly applicable to the production of freestanding metal structures. The issues of fatigue and yield strength are being addressed by developing novel surface micromachined tensile and bend testers, by interferometry, and by TEM analysis. The MEMS tensile tester has a ''Bosch'' etched hole to allow for direct viewing of the microstructure in a TEM before, during, and after loading. This approach allows for the quantitative measurements of stress-strain relations while imaging dislocation motion, and determination of fracture nucleation in samples with well-known fatigue/strain histories. This technique facilitates the determination of the limits for classical deformation mechanisms and helps to formulate a new understanding of the mechanical response as the grain sizes are refined to a nanometer scale. Together, these studies will result in a science

  20. Heterogeneous 2.5D integration on through silicon interposer (United States)

    Zhang, Xiaowu; Lin, Jong Kai; Wickramanayaka, Sunil; Zhang, Songbai; Weerasekera, Roshan; Dutta, Rahul; Chang, Ka Fai; Chui, King-Jien; Li, Hong Yu; Wee Ho, David Soon; Ding, Liang; Katti, Guruprasad; Bhattacharya, Suryanarayana; Kwong, Dim-Lee


    Driven by the need to reduce the power consumption of mobile devices, and servers/data centers, and yet continue to deliver improved performance and experience by the end consumer of digital data, the semiconductor industry is looking for new technologies for manufacturing integrated circuits (ICs). In this quest, power consumed in transferring data over copper interconnects is a sizeable portion that needs to be addressed now and continuing over the next few decades. 2.5D Through-Si-Interposer (TSI) is a strong candidate to deliver improved performance while consuming lower power than in previous generations of servers/data centers and mobile devices. These low-power/high-performance advantages are realized through achievement of high interconnect densities on the TSI (higher than ever seen on Printed Circuit Boards (PCBs) or organic substrates), and enabling heterogeneous integration on the TSI platform where individual ICs are assembled at close proximity (packaging factories. While the systems and devices that power the mobile society benefit from exploiting advantages of 2.5D integration on TSI, there do exist surmountable challenges that need to be addressed for this relatively new technology to be used in high volume production of next generation semiconductor devices. The key areas of focus and challenges include: Technology planning and design-execution that are necessary for harnessing 2.5D TSI for building systems, processing flow for the fabrication of 100 μm thick TSI at acceptable costs, manufacturing flow for assembling multiple ICs on a 100 μm thick TSI in a repeatable, and reliable manner, thermo-mechanical analysis and optimization for addressing warpage issues, and thermal management for addressing heat dissipation. We have outlined design, manufacturing methodologies, and challenges, along with solutions to the challenges associated with taking 2.5D TSI technology to high volume production within the next few years.

  1. Experiments for practical education in process parameter optimization for selective laser sintering to increase workpiece quality (United States)

    Reutterer, Bernd; Traxler, Lukas; Bayer, Natascha; Drauschke, Andreas


    Selective Laser Sintering (SLS) is considered as one of the most important additive manufacturing processes due to component stability and its broad range of usable materials. However the influence of the different process parameters on mechanical workpiece properties is still poorly studied, leading to the fact that further optimization is necessary to increase workpiece quality. In order to investigate the impact of various process parameters, laboratory experiments are implemented to improve the understanding of the SLS limitations and advantages on an educational level. Experiments are based on two different workstations, used to teach students the fundamentals of SLS. First of all a 50 W CO2 laser workstation is used to investigate the interaction of the laser beam with the used material in accordance with varied process parameters to analyze a single-layered test piece. Second of all the FORMIGA P110 laser sintering system from EOS is used to print different 3D test pieces in dependence on various process parameters. Finally quality attributes are tested including warpage, dimension accuracy or tensile strength. For dimension measurements and evaluation of the surface structure a telecentric lens in combination with a camera is used. A tensile test machine allows testing of the tensile strength and the interpreting of stress-strain curves. The developed laboratory experiments are suitable to teach students the influence of processing parameters. In this context they will be able to optimize the input parameters depending on the component which has to be manufactured and to increase the overall quality of the final workpiece.

  2. PCB bending causes and improving methods%印制板翘曲成因及改善方法

    Institute of Scientific and Technical Information of China (English)

    潘秋平; 胡吉峰; 舒旋; 郭蓉


      伴随着PCB行业与表面贴装工艺的快速发展,未来PCB线路与PAD间的间距会越来越小,表面所帖装的零件会更加密集,与此同时,PCB本身的变形弯曲对贴装工艺的影响也越来越大,为长期来阻碍贴装工艺发展的一大难题,如何解决这一难题,目前业界还没有一个有效的改善方法,故文章将重点对生产作业,压合制程参数优化以及设计等三大方面对板弯板曲产生的原因进行分析,以供同行业做参考改善。%Along with the PCB industry and surface mount technology rapid development, the future PCB line and PAD interval will be smaller and smaller, surface mount components will be more intensive, at the same time, the own deformation and warpage of the PCB and their impact is also growing. It is a long-term problem for the surface mount technology development. How to solve this problem ?The industry has no effective improvement method. This paper will focus on the production, pressing process parameters optimization and design in three aspects of the plate bending. Analysis on the causes and method to improve are also made.

  3. Cure shrinkage effects in epoxy and polycyanate matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Spellman, G.P.


    A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type, Fiberite 3501-6, was used as a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLA RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to the same thermal cycles. However, only the new portion of the laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of the laminate. The baseline material, Fiberite 3501-6, exhibited cure shrinkage that was in accordance with expectations. Cure strains were {minus}4.5E-04. The YLA RS-3 material had cure strains somewhat lower at {minus}3.2E-04. The Fiberite 954-2A cure strain was {minus}1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did not result in meaningful results because the processing methods were not fully compatible with the material.

  4. Advanced Flip Chips in Extreme Temperature Environments (United States)

    Ramesham, Rajeshuni


    material and the silicon die or chip, and also the underfill materials. Advanced packaging interconnects technology such as flip-chip interconnect test boards have been subjected to various extreme temperature ranges that cover military specifications and extreme Mars and asteroid environments. The eventual goal of each process step and the entire process is to produce components with 100 percent interconnect and satisfy the reliability requirements. Underfill materials, in general, may possibly meet demanding end use requirements such as low warpage, low stress, fine pitch, high reliability, and high adhesion.

  5. Process-induced damage evolution and management in resin transfer molding of composite panels (United States)

    Kuan, Yean-Der


    Woven fiber composites made by resin transfer molding process are currently used as the primary and secondary load bearing structures in automotive and aircraft industries. A variety of defects could be evolved during the injection stage and the curing stage of the process. Improper injection conditions or unsound tool design would result in process induced damage in the form of dry spots, incomplete filling, or displacement of the fiber. In the curing stage, the process parameters of heating and cooling rates, and the temperature level at each element of the curing cycle have direct effects on the development of internal residual stresses, and shape distortion due to warpage. The work in this dissertation aims at developing numerical models to predict, characterize, and minimize process-induced damage during both the injection stage and curing stage in RTM process for woven-fiber composites. A control volume technique based on the finite difference method is used to characterize the flow behavior in resin transfer molding (RTM) of composite structures. Resin flow through fiber mats is modeled as a two-phase flow through porous media. Experimental results on flow behavior of EPON 826 epoxy resin into irregular mold cavity with fiberglass mats agree well with the present numerical simulation. Parametric analysis of several case studies using developed model illustrates the effectiveness of the flow model in investigating the flow pattern, mold filling time, dry spots formulation, and pressure distribution inside the mold. A numerical model describing the evolution of process-induced damage during curing in molded composite panels was developed. The effects of thermo-mechanical and thermo-chemical responses of the material on the evolution of damage during resin transfer molding of the panels are quantified. The developed numerical model in conjunction with an optimization module based on Simulated Annealing (SA) scheme form a useful tool for conducting a parametric

  6. Anisotropic shrinkage characteristics of tape cast alumina (United States)

    Patwardhan, Jaideep Suresh

    Dimensional control during sintering is a major issue in ceramics processing to avoid high post-sintering costs associated with machining of the fired ceramic part to desired tolerances and dimensions. Ceramic forming processes such as tape casting, injection molding, and extrusion involve shear of anisotropic particles resulting in preferential alignment of the particles in the green body. This preferential alignment causes directionality in mechanical, electrical, optical, and magnetic properties and most importantly warpage or distortion during sintering. A large effort has been devoted to synthesizing ceramic green bodies with minimal density gradients and uniform packing and modeling the sintering behavior evolution but little effort has been devoted to characterizing orientation of particles and the effect of preferential alignment on sintering shrinkage anisotropy. A systematic study was initiated to study the effect of processing variables such as shear rate, solids loading, temperature, and binder content on aqueous tape cast alumina. Three different alumina systems: A16-SG, Baikowski RC-UFX DBM and RC-LS DBM were investigated. Aqueous tapes of high solids loading alumina (56 vol. %) were tape cast at various speeds and thicknesses and assuming plane Couette flow a shear rate regime of 21--270 s-1 was investigated. Higher shear rates and high solids loading resulted in higher in-plane anisotropy whereas the anisotropy in the thickness direction was higher for low solids loading systems. The anisotropy was found to be fairly constant above a certain critical shear rate (˜100 s-1) irrespective of the temperature and the solids loading and this correlated with the viscosity-shear rate relationship of the cast slips. The higher shrinkage anisotropy in the thickness direction for the low solids loading systems (35 and 45 vol. %) was attributed to the higher amount of organics in the slip required to sustain the suitable viscosity for tape casting and

  7. Reduced Moment-Based Models for Oxygen Precipitates and Dislocation Loops in Silicon (United States)

    Trzynadlowski, Bart

    The demand for ever smaller, higher-performance integrated circuits and more efficient, cost-effective solar cells continues to push the frontiers of process technology. Fabrication of silicon devices requires extremely precise control of impurities and crystallographic defects. Failure to do so not only reduces performance, efficiency, and yield, it threatens the very survival of commercial enterprises in today's fiercely competitive and price-sensitive global market. The presence of oxygen in silicon is an unavoidable consequence of the Czochralski process, which remains the most popular method for large-scale production of single-crystal silicon. Oxygen precipitates that form during thermal processing cause distortion of the surrounding silicon lattice and can lead to the formation of dislocation loops. Localized deformation caused by both of these defects introduces potential wells that trap diffusing impurities such as metal atoms, which is highly desirable if done far away from sensitive device regions. Unfortunately, dislocations also reduce the mechanical strength of silicon, which can cause wafer warpage and breakage. Engineers must negotiate this and other complex tradeoffs when designing fabrication processes. Accomplishing this in a complex, modern process involving a large number of thermal steps is impossible without the aid of computational models. In this dissertation, new models for oxygen precipitation and dislocation loop evolution are described. An oxygen model using kinetic rate equations to evolve the complete precipitate size distribution was developed first. This was then used to create a reduced model tracking only the moments of the size distribution. The moment-based model was found to run significantly faster than its full counterpart while accurately capturing the evolution of oxygen precipitates. The reduced model was fitted to experimental data and a sensitivity analysis was performed to assess the robustness of the results. Source

  8. Battery powered portable vapor compression cycle system with PCM condenser (United States)

    DeNardo, Nicholas M.

    stresses and sometimes detrimental warpage. The current solution to this problem has been to print faster in order to lessen the temperature gradients, however very high extrusion speeds are likely not ideal for achieving optimal material properties. The high shear rates induce further damage to fibers, and entrapped air during the extrusion process may not escape, leading to high void content. Another significant challenge is overcoming the anisotropy in printed parts, which arises due to the stiff reinforcing fibers orienting primarily in the print direction. This complicates the use in demanding applications such as composite tooling, where high stiffness and low CTE are desirable in all directions. In 2014, a group of graduate students at Purdue University was formed to develop a better understanding of large-scale additive manufacturing processes incorporating high temperature and high fiber content polymer composites. The team spent more than one year designing, developing, and optimizing a lab-scale system that offers full control over all processing parameters, and has begun studying the relevant phenomena and developing models to predict the outcome of printing processes. This thesis will summarizes the system development process, printing process, composite tooling applications, as well as the mechanical, structural, and viscoelastic properties of printed materials, making it one of the most comprehensive documents written in large-scale additive manufacturing of fiber-reinforced polymers to date. The properties of 50 weight percent carbon fiber-reinforced PPS, a material of high interest in the field, will be presented in detail. The viscoelastic properties will be measured and discussed in the context of both stress relaxation during the printing process and the required performance metrics of composite tooling. A summary of the major results and recommendations can be found in chapter 7.

  9. Metrology of Large Parts. Chapter 5 (United States)

    Stahl, H. Philip


    As discussed in the first chapter of this book, there are many different methods to measure a part using optical technology. Chapter 2 discussed the use of machine vision to measure macroscopic features such as length and position, which was extended to the use of interferometry as a linear measurement tool in chapter 3, and laser or other trackers to find the relation of key points on large parts in chapter 4. This chapter looks at measuring large parts to optical tolerances in the sub-micron range using interferometry, ranging, and optical tools discussed in the previous chapters. The purpose of this chapter is not to discuss specific metrology tools (such as interferometers or gauges), but to describe a systems engineering approach to testing large parts. Issues such as material warpage and temperature drifts that may be insignificant when measuring a part to micron levels under a microscope, as will be discussed in later chapters, can prove to be very important when making the same measurement over a larger part. In this chapter, we will define a set of guiding principles for successfully overcoming these challenges and illustrate the application of these principles with real world examples. While these examples are drawn from specific large optical testing applications, they inform the problems associated with testing any large part to optical tolerances. Manufacturing today relies on micrometer level part performance. Fields such as energy and transportation are demanding higher tolerances to provide increased efficiencies and fuel savings. By looking at how the optics industry approaches sub-micrometer metrology, one can gain a better understanding of the metrology challenges for any larger part specified to micrometer tolerances. Testing large parts, whether optical components or precision structures, to optical tolerances is just like testing small parts, only harder. Identical with what one does for small parts, a metrologist tests large parts and optics