• Title/Summary/Keyword: thermomechanical reliability

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Improvement in Thermomechanical Reliability of Power Conversion Modules Using SiC Power Semiconductors: A Comparison of SiC and Si via FEM Simulation

  • Kim, Cheolgyu;Oh, Chulmin;Choi, Yunhwa;Jang, Kyung-Oun;Kim, Taek-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.25 no.3
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    • pp.21-30
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    • 2018
  • Driven by the recent energy saving trend, conventional silicon based power conversion modules are being replaced by modules using silicon carbide. Previous papers have focused mainly on the electrical advantages of silicon carbide semiconductors that can be used to design switching devices with much lower losses than conventional silicon based devices. However, no systematic study of their thermomechanical reliability in power conversion modules using finite element method (FEM) simulation has been presented. In this paper, silicon and silicon carbide based power devices with three-phase switching were designed and compared from the viewpoint of thermomechanical reliability. The switching loss of power conversion module was measured by the switching loss evaluation system and measured switching loss data was used for the thermal FEM simulation. Temperature and stress/strain distributions were analyzed. Finally, a thermal fatigue simulation was conducted to analyze the creep phenomenon of the joining materials. It was shown that at the working frequency of 20 kHz, the maximum temperature and stress of the power conversion module with SiC chips were reduced by 56% and 47%, respectively, compared with Si chips. In addition, the creep equivalent strain of joining material in SiC chip was reduced by 53% after thermal cycle, compared with the joining material in Si chip.

Thermo-mechanical Reliability Analysis of Copper TSV (구리 TSV의 열기계적 신뢰성해석)

  • Choa, Sung-Hoon;Song, Cha-Gyu
    • Journal of Welding and Joining
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    • v.29 no.1
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    • pp.46-51
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    • 2011
  • TSV technology raises several reliability concerns particularly caused by thermally induced stress. In traditional package, the thermo-mechanical failure mostly occurs as a result of the damage in the solder joint. In TSV technology, however, the driving failure may be TSV interconnects. In this study, the thermomechanical reliability of TSV technology is investigated using finite element method. Thermal stress and thermal fatigue phenomenon caused by repetitive temperature cycling are analyzed, and possible failure locations are discussed. In particular, the effects of via size, via pitch and bonding pad on thermo-mechanical reliability are investigated. The plastic strain generally increases with via size increases. Therefore, expected thermal fatigue life also increase as the via size decreases. However, the small via shows the higher von Mises stress. This means that smaller vias are not always safe despite their longer life expectancy. Therefore careful design consideration of via size and pitch is required for reliability improvement. Also the bonding pad design is important for enhancing the reliability of TSV structure.

Effect of Underfill on $\mu$BGA Reliability ($\mu$BGA 장기신뢰성에 미치는 언더필영향)

  • 고영욱;신영의;김종민
    • Proceedings of the International Microelectronics And Packaging Society Conference
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    • 2002.05a
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    • pp.138-141
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    • 2002
  • There are continuous efforts in the electronics industry to a reduced electronic package size. Reducing the size of electronic packages can be achieved by a variety of means, and for ball grid array(BGA) packages an effective method is to decrease the pitch between the individual balls. Chip scale package(CSP) and BGA are now one of the major package types. However, a reduced package size has the negative effect of reducing board-level reliability. The reliability concern is for the different thermal expansion rates of the two-substrate materials and how that coefficient CTE mismatch creates added stress to the BGA solder joint when thermal cycled. The point of thermal fatigue in a solder joint is an important factor of BGA packages and knowing at how many thermal cycles can be ran before failure in the solder BGA joint is a must for designing a reliable BGA package. Reliability of the package was one of main issues and underfill was required to improve board-level reliability. By filling between die and substrate, the underfill could enhance the reliability of the device. The effect of underfill on various thermomechanical reliability issues in $\mu$BGA packages is studied in this paper.

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The Nondestructive Reliability Evaluation which it Applies Ultrasound Thermography about Cutting Crack of Piston Skirt (초음파 서모그래피를 적용한 피스톤 스커트 절단균열에 대한 비파괴 신뢰성 평가)

  • Yang, Yong-Ha;Ma, Sang-Dong;Kim, Jea-Yeol
    • Tribology and Lubricants
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    • v.26 no.6
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    • pp.336-340
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    • 2010
  • Ultrasound thermography detects defects by radiating 20 ~ 30 kHz ultrasound waves to the samples and capturing the heat generated from the defects with the use of an infrared thermographic camera. This technology is being spotlighted as a next-generation NDE for the automobile and aerospace industries because it can test large areas and can detect defects such as cracks and exfoliations in real time. The heating mechanism of the ultrasound vibration has not been accurately determined, but the thermomechanical coupling effect and the surface or internal friction are estimated to be the main causes. When this heat is captured by an infrared thermographic camera, the defects inside or on the surface of objects can be quickly detected. Although this technology can construct a testing device relatively simply and can detect defects within a short time, there are no reliable data about the factors related to its detection ability. In this study, the ultrasound thermography technique was used to manufacture gasoline and diesel engine piston specimens, and nondestructive reliability tests to verify the applicability and validity of the ultrasound thermography technique.

Evaluation of Thermal Deformation Model for BGA Packages Using Moire Interferometry

  • Joo, Jinwon;Cho, Seungmin
    • Journal of Mechanical Science and Technology
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    • v.18 no.2
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    • pp.230-239
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    • 2004
  • A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis of BGA package assembly. High-sensitivity moire interferometry is applied to evaluate and calibrated the model quantitatively. Two ball grid array (BGA) package assemblies are employed for moire experiments. For a package assembly with a small global bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package assembly with a large global bending, however, the relative displacements determined by spring model agree well with that by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder damage of the critical solder ball.

A Study on Optimal Design of Underfill for Flip Chip Package Assemblies (플립칩 어셈블리의 언더필 최적설계에 관한 연구)

  • Lee, Seon-Byeong;Kim, Jong-Min;Lee, Seong-Hyeok;Sin, Yeong-Ui
    • Proceedings of the KWS Conference
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    • 2007.11a
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    • pp.150-152
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    • 2007
  • It has been known that the underfilling technique is effective in reducing thermal and environmental stress concentration at solder joint in FC asscemblies. In this paper, the effect of thermomechanical properties of underfill such as coefficient of thermal expansion(CTE) and Young's modulus on reliability of FC assembly under thermal cycling was investigated. For parametric study for optimal design of underfill, finite element analyses(FEA) were performed for seven different CTEs and five different Young's modulus. The results show that the concentrated maximum stress decreases as Young's modulus of underfill increases and the CTE of underfill decreases.

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A study on the stress distribution and nugget formation in resistance welding process using computer simulation (컴퓨터 시뮬레이션을 이용한 저항용접에 관한 연구)

  • 함원국
    • Journal of Welding and Joining
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    • v.9 no.3
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    • pp.41-51
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    • 1991
  • The thermomechanical coupling phenomena in the resistance welding process is complicated due to interactions of mechanical, thermal and electrical factors. Although experimental investigations of resistance spot welding have been carried out, but there are a few by computer simulation. so the purpose of this research is to decrease the time and cost much required in experimental investigation by carrying out the analysis of the resistance spot welding process through computer simulation based on the finite element method. The tool used in the computer simulation is the commercial ANSYS program package. A two dimensional axisymetric model is used to simulate the resistance spot welding for two stainless steel sheets of equal thickness and parametric study is carried out for variable welding current, workpieces of unequal thickness and dissimilar materials. The results from the computer simulation are in good agreement with the experimental one. Through these results, such items as stress distribution, temperature profiles, thermal expansion and weld nugget formation are predicted. Reliability and applicability of finite element models have been demonstrated to simulate and to analyze the resistance spot welding process.

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The Effect of Grain Size and Film Thickness on the Thermal Expansion Coefficient of Copper and Silver Thin Films (구리와 은 박막의 열팽창계수에 미치는 결정립 크기와 박막 두께의 영향)

  • Hwang, Seulgi;Kim, Youngman
    • Korean Journal of Metals and Materials
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    • v.48 no.12
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    • pp.1064-1069
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    • 2010
  • Thin films have been used in a large variety of technological applications such as solar cells, optical memories, photolithographic masks, protective coatings, and electronic contacts. If thin films experience frequent temperature changes, thermal stresses are generated due to the difference in the coefficient of thermal expansion between the film and substrate. Thermal stresses may lead to damage or deformation in thin film used in electronic devices and micro-machined structures. Thus, knowledge of the thermomechanical properties of thin films, such as the coefficient of thermal expansion, is an important issue in determining the stability and reliability of the thin film devices. In this study, thermal cycling of Cu and Ag thin films with various microstructures was employed to assess the coefficient of thermal expansion of the films. The result revealed that the coefficient of thermal expansion (CTE) of the Cu and Ag thin films increased with an increasing grain size. However, the effect of film thickness on the CTE did not show a remarkable difference.

Experimental and Numerical Analysis of Package and Solder Ball Crack Reliability using Solid Epoxy Material (Solid Epoxy를 이용한 패키지 및 솔더 크랙 신뢰성 확보를 위한 실험 및 수치해석 연구)

  • Cho, Youngmin;Choa, Sung-Hoon
    • Journal of the Microelectronics and Packaging Society
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    • v.27 no.1
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    • pp.55-65
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    • 2020
  • The use of underfill materials in semiconductor packages is not only important for stress relieving of the package, but also for improving the reliability of the package during shock and vibration. However, in recent years, as the size of the package becomes larger and very thin, the use of the underfill shows adverse effects and rather deteriorates the reliability of the package. To resolve these issues, we developed the package using a solid epoxy material to improve the reliability of the package as a substitute for underfill material. The developed solid epoxy was applied to the package of the application processor in smart phone, and the reliability of the package was evaluated using thermal cycling reliability tests and numerical analysis. In order to find the optimal solid epoxy material and process conditions for improving the reliability, the effects of various factors on the reliability, such as the application number of solid epoxy, type of PCB pad, and different solid epoxy materials, were investigated. The reliability test results indicated that the package with solid epoxy exhibited higher reliability than that without solid epoxy. The application of solid epoxy at six locations showed higher reliability than that of solid epoxy at four locations indicating that the solid epoxy plays a role in relieving stress of the package, thereby improving the reliability of the package. For the different types of PCB pad, NSMD (non-solder mask defined) pad showed higher reliability than the SMD (solder mask defined) pad. This is because the application of the NSMD pad is more advantageous in terms of thermomechanical stress reliability because the solderpad bond area is larger. In addition, for the different solid epoxy materials with different thermal expansion coefficients, the reliability was more improved when solid epoxy having lower thermal expansion coefficient was used.

Analysis of Thermomechanical Properties Considering the Thermal Expansion Anisotropy of Membrane-Type Fiber-Reinforced Composite Material (멤브레인 형 섬유강화 복합재료의 열팽창 이방성을 고려한 열 기계적 특성 분석)

  • Jeong, Yeon-Jae;Kim, Hee-Tae;Kim, Jeong-Dae;Oh, Hoon-Gyu;Kim, Yong-Tai;Park, Seong-Bo;Lee, Jae-Myung
    • Journal of the Society of Naval Architects of Korea
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    • v.58 no.1
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    • pp.17-23
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    • 2021
  • The membrane-type Liquefied Natural Gas (LNG) cargo tank is equipped with a double barrier to seal the LNG, of which the secondary barrier serves to prevent LNG leakage and mainly uses fiber-reinforced composite materials. However, the composite materials have thermal expansion anisotropy, which deteriorates shape distortion and mechanical performance due to repeated thermal loads caused by temperature changes between cryogenic and ambient during the unloading of LNG. Therefore, in this study, the longitudinal thermal expansion characteristics of the composite materials were obtained using a vertical thermo-mechanical analyzer, and the elastic modulus was obtained through the tensile test for each temperature to perform thermal load analysis for each direction. This is considered that it is useful to secure reliability from the viewpoint of the design of materials for a LNG cargo hold.