在高性能運算或網通電子系統中為解決散熱需求，通常會在電子構裝元件上安裝散熱片並施加壓力以提升散熱效率。但在受到散熱片壓力下，電子構裝元件與系統主機板間之球柵陣列錫球會產生潛變壓縮的現象。長時間使用下，球柵陣列錫球會因變形量過大而導致錫球橋接短路失效的情形。為了解球柵陣列覆晶構裝元件在受壓情況下之可靠度，本論文建立一套錫球潛變模型來預測受壓情況下球柵陣列錫球之使用壽命。
本論文利用實驗及模擬方式建立錫銀銅3807 (Sn-3.8wt%Ag-0.7wt%Cu) 無鉛球柵陣列錫球在受壓情況下的潛變失效模型。實驗內容包括利用球柵陣列錫球試件及覆晶構裝元件進行加速壓縮實驗，以及錫柱試件之等應變率及潛變壓縮實驗。球柵陣列錫球壓縮潛變模型乃是藉由錫柱壓縮實驗結果進行曲線擬合以建立錫銀銅3807銲錫黏塑性本構模型，然後配合有限元素分析模擬球柵陣列錫球受壓潛變變形，並將模擬結果與球柵陣列錫球壓縮加速實驗結果比對，以驗證模型並調整相關參數。最後利用有限元素模擬結果建立起不同覆晶構裝元件內球柵陣列錫球之簡化壓縮潛變模型，此簡化壓縮潛變模型可提供快速分析並預測覆晶構裝元件在受特定壓力情況下之使用壽命，或是在電子系統設計壽命下，元件能夠承受之最大散熱片壓力。

Heat sinks with fans are typically used for thermal management in state-of-the-art electronic systems for computing or telecommunication. For the purpose of improving the efficiency of heat conduction, a compressive load is usually applied to the assembly of heat sink and the electronic component. For electronic components with ball grid array (BGA) solder joints the compressive load would cause solder joint creep collapse and bridging, which in turn would lead to electrical short failure. In order to predict the BGA solder joint reliability under extended heat sink compression, a numerical model is developed in this study for modeling the compressive creep deformation of solder joints.
Both experimental and numerical studies are conducted for developing the creep model for lead-free SAC3807 (Sn-3.8wt%Ag-0.7wt%Cu) BGA solder joints under compression. The experimental studies include BGA solder joint compression tests using both custom-developed solder joint samples and real flip-chip BGA packages, and solder column characterization for constant strain rate and creep compressive tests. A viscoplastic constitutive model is developed based on the compressive characterization and is implemented into numerical finite element model for simulating BGA solder joints under extended compression. The model is then validated by using the experimental results from the BGA solder joint compression test results. Finally, a simplified power-law model is developed from the numerical finite element model to calculate the creep collapse of BGA joints for two flip-chip BGA packages. The simplified model can be used to determine the service life of the flip-chip package for a pre-determined heat sink compression; or to determine the maximum allowable compression if the service life of the package is given.

[1] E.-C. Ahn, T.-J. Cho, J.-B. Shim, H.-J. Moon, J.-H. Lyu, K.-W. Choi, S.-Y. Kang, S.-Y. Oh, “Reliability of flip chip BGA package on organic substrate,” Proceedings of the Electronic Components and Technology Conference(ECTC 2000), pp. 1215-1220, 2000.

[2] K. Nagarajan, R. H. Dauskardt, “Adhesion and reliability of underfill/substrate interfaces in flip chip BGA packages: Metrology and characterization,” Proceedings of the International Electronics Manufacturing Technology (IEMT 2002), pp. 206-214, 2002.

[3] P. S. Ho, G. Wang, M. Ding, J.-H. Zhao, X. Dai, “Reliability issues for flip-chip packages,” Proceedings of the Microelectronics Reliability, Vol. 44, pp. 719-737, 2004.

[4] A. Schubert, R. Dudek, E. Auerswald, A. Gollhardt, B. Michel, H. Reichl, “Fatigue life models for SnAgCu and SnPb solder joints evaluated by experiments and simulation,” Proceedings of the Electronic Components and Technology Conference(ECTC 2003), pp. 603-610, 2003.

[5] C.-T. Peng, C.-M. Liu, J.-C. Lin, H.-C. Cheng, K.-N. Chiang, “Reliability analysis and design for the fine-pitch flip chip BGA packaging,” Proceedings of the IEEE Transactions on Components and Packaging Technologies, Vol. 27, pp. 684-693, 2004.

[6] K. E. Ong, S. L. Too, W. K. Loh, P. Christopher, L. Ong, C. K. Chan, E. H. Yap “Solder joint reliability performance of flip chip molded ball grid array (BGA) package for network/communication application,” Proceedings of the International Electronics Manufacturing Technology (IEMT 2006), pp. 179-184, 2006.

[7] L. Garner, C. Zhang, K. S. Beh, K. Helms, Y. L. Tan, “Effect of Compression Loads on the Solder Joint Reliability of Flip Chip BGA Packages,” Proceedings of the Electronic Components and Technology Conference(ECTC 2004), Vol 1, p 692-698, 2004.

[8] P. K. Bhatti, , P. Min F. Xuejun, “Reliability analysis of SnPb and SnAgCu solder joints in FC-BGA packages with thermal enabling preload” Proceedings of the Electronic Components and Technology Conference(ECTC 2006), pp. 601-606, 2006.

[9] K. S. Beh, W. K. Loh, J. S. Leong, W. A. Tan, “Compressive load challenges on sub 1.00 ball pitch for flip chip ball grid array (FCBGA),” Proceedings of the 2005 Conference on High Density Microsystem Design and Packaging and Component Failure Analysis, HDP'05, 2006.

[10] R. Zhang, “ Characterization of board level reliability of a system with flip chip HITCE BGA package through modeling and testing,” Proceedings of the Electronic Components and Technology Conference(ECTC 2008), pp. 1438-1444, 2008.

[11] M. Ahmad, K. C. Liu, C. J. Lee, J. Priest, S.-J. Pak, S. Narasimhan, M. Nagar, J. Xue, “Impact of system level thermal solution on the interconnect reliability of high performance and high heat dissipating CSP package,” Proceedings of the Electronic Components and Technology Conference(ECTC 2008), pp. 341-346, 2008.

[12] R. C. Weinbel, J. K. Tien, R. A. Pollak, S. K. Kang, “Creep-fatigue interaction in eutectic lead-tin solder alloy,” Proceedings of the Journal of Materials Science, Vol. 22, pp. 3901-3906, 1992.

[13] J. H. Lau, D. W. Rice, “ Thermal stress/strain analysis of ceramic quad flat pack packages and interconnections,” Proceedings of the Electronic Components and Technology Conference(ECTC 1990), Vol. 1, pp. 824-834, 1990.

[14] R. Darveaux, K. Banerji, “Constitutive relations for tin-based solder joints,” Proceedings of the IEEE transactions on components, hybrids, and manufacturing technology, Vol. 15, pp. 1013-1024, 1992.

[15] M. Pei, J. Qu, “Constitutive modeling of lead-free solders,” Proceedings of the ASME/Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems: Advances in Electronic Packaging, Vol. PART B, pp. 1307-1311, 2005.

[16] B. Rodgers, B. Flood, J. Punch, F. Waldron, “Experimental determination and finite element model validation of the Anand viscoplasticity model constants for SnAgCu,” Proceedings of the International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Micro-Electronics and Micro-Systems - EuroSimE 2005, pp. 490-496, 2005.

[17] L. Anand, “Constitutive equations for the rate-dependent deformation of metals at elevated temperatures,” Proceedings of the Journal of Engineering Materials and Technology, Transactions of the ASME, Vol. 104, pp. 12-17, 1982.

[18] S. B. Brown, K. H. Kim, L. Anand, “Internal variable constitutive model for hot working of metals,” Proceedings of the International journal of plasticity, Vol 5, pp. 95-130, 1989.

[19] D. Bhate, D. Chan, G. Subbarayan, T. C. Chiu, V. Gupta, D. R. Edwards, “ Constitutive behavior of Sn3.8Ag0.7Cu and Sn1.0Ag0.5Cu alloys at creep and low strain rate regimes,” Proceedings of the IEEE Transactions on Components and Packaging Technologies, Vol 31, pp. 622-633, 2008.

[20] R. Wu, F. P. McCluskey, “ Constitutive relations of indium solder joint in cold temperature electronic packaging based on Anand model,” Proceedings of the IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, I-THERM, pp. 683-686, 2008.

[21] ASTM E9-89A “Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature” West Conshohocken, PA, 2009.

[22] 楊閎鈞“錫銀銅3807在壓縮情形下的黏塑性本構模型建立”碩士論文,國立成功大學, 2009.

[23] O. A. Cornejo “Aging effects on microstructure and creep in Sn-3.8Ag-0.7Cu solder,” Master Thesis, Naval Postgraduate School, CA, USA, 2007.

[24] ANSYS, ver. 11.0, ANSYS Inc., 2008.

[25] MATLAB, R2008a, The MathWork, Inc., 2008.