最佳化針狀觸點覆晶構裝之探討

本文主要是探討在覆晶構裝中，使用不同尺寸錫球的針狀觸點結構在應力上之差異，再利用這些數據進一步評估實際可能使用的疲勞壽命。本研究是利用ANSYS模擬27種不同參數的覆晶構裝結構體在25℃~125℃熱應力負荷之後所得到的熱分佈結果，分析觸點在von Mises應力與剪應力上的變化，並使用Coffin-Manson疲勞壽命方程式來求得最長壽命的最佳化參數。在27種不同參數的針狀觸點覆晶構裝中，所得到的最佳化參數為觸點直徑0.075mm、觸點高0.121mm、觸點間距1.135mm與觸點離晶片邊緣0.5mm之組合，其von Mises應力的極大值為54.594Mpa、剪應力極大值為6.016Mpa，疲勞壽命則為253706週次。在分析過程中發現針狀觸點的高度與觸點間距對於疲勞壽命的影響甚大，建議在設計覆晶結構時，須特別考慮此二項參數。

關鍵字

ANSYS ； Coffin-Manson疲勞壽命；覆晶構裝；針狀觸點

並列摘要

This investigation describes about the effect of different shape solder ball on stress in flip chip packaging. The stress developed in then used to evaluate the fatigue life. ANSYS has been implemented to study the von Mises stress an Shear strain behavior and fatigue life of pin shaped solder ball in flip chip package under mechanical and thermal stress. Twenty-seven different parameters such as solder ball shape, size etc. has been considered for simulation. The stress/strain behavior is initially studied at thermal load 25C to 125C. The thermal distribution obtained from the thermal analysis is used to simulate the structural analysis to acquire mechanical stress/strain behavior. Coffin-Manson fatigue formula is used to optimize the life of solder balls in flip chip package. The stress/strain behavior of twenty-seven pin shaped solder balls having same diameter but different heights, different solder ball separations and different distances of solder balls to the edge of a chip is studied. The optimized result is obtained with the solder ball having diameter = 0.075mm; height= 0.121mm and the ball pitch 1.135mm and the distance of solder balls to the edge of a chip 0. 5mm. The maximum values of von Mises stress and shear stress are calculated to be 54.594 MPa and 6.016 MPa respectively. The fatigue life is determined to be 253706 cycles in the optimized structure. The analysis process points out that the height of solder ball, intervals between solder ball, and distance of solder ball to the chip edge influence the fatigue life. This suggests that special attention has to be given on these parameters during the design of the structure in Flip Chip.

並列關鍵字

Flip Chip ； ANSYS ； Coffin-Manson ； Pin Shaped

參考文獻

[25]邱建嘉, ”覆晶構裝疲勞壽命與無鉛銲料可靠度評估”,中原大學機械工程研究所碩士論文, 2004。

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[2] L. L. Mercado and V. Sarihan, “Predictive Design of Flip- chip PBGA for High Reliability and Low Cost”, Electronic Components and Technology Conference, pp. 342- 348, 1999

[5] J. H. Lau and D. W. Rice, “Thermal Fatigue Life Prediction of Flip Chip Solder Joints by Fracture Mechanics Method”, Advances In Electronic Packaging ASME, pp. 385- 392, 1992

[10] A. Mendelson, “Plasticity: Theory and Application”, 1970

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最佳化針狀觸點覆晶構裝之探討

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