- 學位論文
底膠模型與熱循環對覆晶構裝疲勞壽命的影響
Underfill Model and Thermal Cycle Loading Effects on the Thermal Fatigue of Flip Chip
摘要
本文針對覆晶構裝，利用有限元素分析軟體ANSYS模擬封裝體在溫度循環下的應力應變與疲勞壽命值，覆晶構裝體包含了含底膠與無底膠兩種模型，而含底膠覆晶構裝中底膠以線彈性與黏彈性兩種不同的材料特性模擬。錫鉛凸塊材料以彈性-塑性-潛變的模型建立，熱循環則包含熱加速循環與熱衝擊循環。計算疲勞壽命時，將結合與時間相依的潛變應變，以及與時間獨立的塑性應變等兩種不同的疲勞模型。 模擬結果顯示，最外側的錫鉛凸塊上方位置之疲勞壽命預測值最小，也是最容易發生疲勞破壞的地方。另外，含底膠的覆晶構裝的疲勞壽命較無底膠的長許多；相對於塑性應變，潛變應變對疲勞壽命有較大的影響；而相對於熱加速循環，受熱衝擊循環之構裝體的疲勞壽命會較短。黏彈性底膠模型受加速熱循環的塑性應變較線彈性來的大，疲勞壽命則較短，但差距有限，所以模擬底膠材料時這兩種模型皆可。
並列摘要
This thesis uses finite element method to simulate the fatigue life of solder joints of a flip chip model under thermal cycle loading. The flip chip model includes with underfill and without underfill. The underfill material is modeled by two different models, linear elastic and viscoelastic. The solder joints of the flip chip are built with an elastic-plastic-creep model. Two different fatigue life models, time-dependent creep strain and time-independent plastic strain, are used in the simulation. In addition, two kinds of thermal loading including accelerated thermal cycling and thermal shock are considered in this thesis. The result shows that the outer solder joint is the first place that fatigue occurs. In addition, the fatigue life of the flip chip model with underfill is longer than that without underfill. Comparing to the plastic strain, the creep strain is more influential in determining the fatigue life of solder joints. However, comparing to the accelerated thermal cycling, the fatigue life is shorter when flip chip is under the thermal shock cycling. The plastic strain of viscoelastic model with underfill is bigger than linear elastic model, but the fatigue life is shorter.