Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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Numerical Study of Warpage and Stress for the Ultra Thin Package

수치해석에 의한 초박형 패키지의 휨 현상 및 응력 특성에 관한 연구

  • Song, Cha-Gyu (Seoul National University of Science and Technology NID Fusion Technology School) ;
  • Choa, Sung-Hoon (Seoul National University of Science and Technology NID Fusion Technology School)
  • 송차규 (서울과학기술대학교 NID 융합기술대학원) ;
  • 좌성훈 (서울과학기술대학교 NID 융합기술대학원)
  • Received : 2010.09.28
  • Accepted : 2010.12.22
  • Published : 2010.12.30
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Abstract

Semiconductor packages are increasingly moving toward miniaturization, lighter and high performance. Futhermore, packages become thinner. Thin packages will generate serious reliability problems such as warpage, crack and other failures. Reliability problems are mainly caused by the CTE mismatch of various package materials. Therefore, proper selection of the package materials and geometrical optimization is very important for controlling the warpage and the stress of the package. In this study, we investigated the characteristics of the warpage and the stress of several packages currently used in mobile devices such as CABGA, fcSCP, SCSP, and MCP. Warpage and stress distribution are analyzed by the finite element simulation. Key material properties which affect the warpage of package are investigated such as the elastic moduli, CTEs of EMC molding and the substrate. Geometrical effects are also investigated including the thickness or size of EMC molding, silicon die and substrate. The simulation results indicate that the most influential factors on warpage are EMC molding thickness, CTE of EMC, elastic modulus of the substrate. Simulation results show that warpage is the largest for SCSP. In order to reduce the warpage, DOE optimization is performed, and the optimization results show that warpage of SCSP becomes $10{\mu}m$.

최근 휴대폰, PDA 등과 같은 모바일 전자 기기들의 사용이 급증하면서 다기능, 고성능, 초소형의 패키지가 시장에서 요구되고 있다. 따라서 사용되는 패키지의 크기도 더 작아지고 얇아지고 있다. 패키지에 사용되는 실리콘 다이 및 기판의 두께가 점점 얇아지면서 휨 변형, 크랙 발생, 및 기타 여러 신뢰성 문제가 크게 대두되고 있다. 이러한 신뢰성 문제는 서로 다른 패키지 재료의 열팽창계수의 차이에 의하여 발생된다. 따라서 초박형의 패키지의 경우 적절한 패키지물질과 두께 및 크기 등의 선택이 매우 중요하다. 본 논문에서는 현재 모바일 기기에 주로 사용되고 있는 CABGA, fcSCP, SCSP 및 MCP (Multi-Chip Package) 패키지에 대하여 휨과 응력의 특성을 수치해석을 통하여 연구하였다. 특히 휨 현상에 영향을 줄 수 있는 여러 중요 인자들, 즉 EMC 몰드의 두께 및 물성(탄성계수 및 열팽창 계수), 실리콘 다이의 두께와 크기, 기판의 물성 등이 휨 현상에 미치는 영향을 전반적으로 고찰하였다. 이를 통하여 휨 현상 메커니즘과 이를 제어하기 위한 중요 인자를 이해함으로써 휨 현상을 최소화 하고자 하였다. 휨 해석 결과 가장 큰 휨 값을 보인 SCSP에 대하여 실험계획법의 반응표면법을 이용하여 휨이 최소화되는 최적 조합을 구하였다. SCSP 패키지에서 휨에 가장 큰 영향을 미치는 인자는 EMC 두께 및 열팽창 계수, 기판의 열팽창계수, 그리고 실리콘 다이의 두께였다. 궁극적으로 최적화 해석을 통하여 SCSP의 휨을 $10{\mu}m$로 줄일 수 있음을 알 수 있었다.

Keywords

References

  1. W. D. van Driel, G. Q. Zhang, J. H. J. Janssen, L. J. Ernst, F. Su, K. S. Chian and S. Yi, "Prediction and Verification of Process-Induced Thermal Deformation of Electronic Packages using Non-linear FEM and 3D interferometry," Proc. EuroSimE, 362 (2002).
  2. T. Y. Wu, Y. Tsukad and W. T. Chen, "Materials and Mechanics Issues in Flip-chip Organic Packaging," Proc. 46th Electronic Components and Technology Conference (ECTC), 524 (1996).
  3. L. Yip and A. Hamzehdoost, "Package Warpage Evaluation for High Performance PQFP", Proc. 45th Electronic Components and Technology Conference (ECTC), 229 (1995).
  4. W. Y. Kong, J. K. Kim and M. F. Yuen, "Warpage in Plastic Packages: Effects of Process Conditions, Geometry and Materials", IEEE Transitions on Electronics Packaging Manufacturing, 26(3), 245 (2003). https://doi.org/10.1109/TEPM.2003.820806
  5. G. Kelly, C. Lyden, W. Lawton, J. Barrett, A. Saboui, H. Pape and H. Peters, "The Importance of Molding Compound Chemical Shrinkage in the Stress and Warpage Analysis of PQFPs", Proc. 45th Electronic Components and Technology Conference (ECTC), 977 (1995).
  6. B. Kiang, J. Wittmershaus, R. Kar and N. Sugai, "Package Warpage Evaluation for Multi-Layer Molded PQFP", Proc. 11th IEEE/CHMT International Electronics on Manufacturing Technology Symposium (IEMT), 89 (1991).
  7. M. J. Ko, D. S. Shin, M. S. Moon, I. H. Lee and Y. J. Park, "The Effect of Mold Compounds on Warpage in LOC Package", Proc. 49th Electronic Components and Technology Conference (ECTC), 1196 (1999).
  8. R. Ingkanisorn and A. Sriyarunya, "RoHS-Compliant Molding Compound Evaluation and Manufacturability For FBGA Packages", Proc. 6th Electronic Packaging Technology Conference (EPTC), 479 (2004).
  9. H. Tang, J. Nguyen, J. Zhang and I. Chien, "Warpage Study of a Package on Package Configuration", International Symposium on High Density Packaging (HDP), 1 (2007).
  10. J. Joo and D. Kim, "Thermo-mechanical Deformation Analysis of Flip Chip PBGA Packages Subjected to Temperature Change", J. Microelectron. Packag. Soc., 13(4), 17 (2006).
  11. K. Irving, Y. Chien, J. Zhang, L. Rector and M. Todd, "Low Warpage Molding Compound Development for Array Packages", Proc. 1st Electronics Systemintegration Technology Conference (ESTC), 2, 1001 (2006).
  12. W. H. Zhu, G. Li, W. Sun, F. X. Che, A. Sun, C. K. Wang, H. B. Tan, B. Z. Zhao and N. H. Chin, "Cure Shrinkage Characterization and its Implementation into Correlation of Warpage between Simulation and Measurement", Proc. 8th International Conference on EuroSimE, 1 (2007).
  13. K. Xue, J. Wu, H. B. Chen, J. B. Gai and A. Lam, "Warpage Prediction of Fine Pitch BGA by Finite Element Analysis and Shadow Moiré Technique", International Conference on Electronic Packaging Technology & High Density Packaging (ICEPT-HDP), 317 (2009).
  14. G. Xu, J. Zhou and L. Luo, "Warpage and Reliability of Three-dimensional Multi-chip Module with High Density Embedded Substrate", Proc. 8th International Conference on Electronic Packaging Technology (ICEPT), 1 (2007).
  15. W. Sun, W. H. Zhu, C. K. Wang, A. Y. S. Sun and H. B. Tan, "Warpage Simulation and DOE Analysis with Application in Package-on-Package Development", International Conference on EuroSimE, 1 (2008).
  16. T. Jin, N. S. Goo, S. Woo, H. C. Park, "Use of a Digital Image Correlation Technique for Measuring the Material Properties of Beetle Wing", Journal of Bionic Engineering, 6, 224-231 (2009). https://doi.org/10.1016/S1672-6529(08)60105-5
  17. M. Tsai, H. Chang, M. Pecht, "Warpage Analysis of Flip-Chip PBGA Packages Subject to Thermal Loading", IEEE Trans. on Device and Material Reliability, 9(3), 419 (2009). https://doi.org/10.1109/TDMR.2009.2023847
  18. Y. L. Tzeng, N. Kao, E. Chen, J. Lai, Y. Wang, C. Hsiao, "Warpage and Stress Characteristics Analyses on Package-on-Package (PoP) Structure", 9th Electronics Packaging Technology Conference, 482 (200)
  19. J. Y. Choi, C. G. Song, H. S. Lee and S.H. Choa, "Numerical Study of Thermo-mechanical Stress on TSV", Korea Society of Professional Engineers (KSPE), 26(12), 23 (2009).
  20. S. Hwang, B. Kim, S. Jung, H. Lee and Y. Joo, "Thermo-Mechanical Analysis of Though-silicon-via in 3D Packaging", J. Microelectron. Packag. Soc., 17(1), 69 (2010).