Package fatigue reliability of the stacked chip BGA evaluated by optimal equivalent solder

A global/local method along with an optimization algorithm, so called the modified sub-modeling approach of optimal equivalent solder is introduced as a simple but effective approach to predict the deformation and the reliability in the package. The viewpoint of equivalent solder in this method is facilitated to obviously reduce the number of elements/nodes so as to enhance computing accuracy and efficiency. To verify the proposed approach, a model of wire-bonded stacked chip Ball Grid Array (WB-SC BGA) package is simulated for analysis. Comparing the global fine mesh method with the global/local method, it is found that the computing time and the data storage space required for this proposed method are only 18.8% and 9.98% of that by the global fine mesh model. Moreover, under the cyclic thermal loading, the difference of the accumulated strain energy density (SED) between the two models is merely 5.76 % with the coincident trends for each other, which means the adopted method is eligible to replace the global fine mesh method. Finally, the analysis model with design factors optimized can highly improve the fatigue life of solder ball up to 79.4% compared to the baseline model.