A global/local method along with an optimization algorithm, so called the modified sub-modeling approach of the 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 elementsodes 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 difference of the accumulated strain energy density (SED) under the cyclic thermal loading is merely 5.76 % between the two models, which means the adopted method is eligible to replace the global fine mesh method. In addition, the analysis model with design factors can highly improve the fatigue life of solder ball up to 79.4% for the best choice from one-factor-at-a-time analysis, however, it turns out 123.7% for the double response surface method when those cases is compared with the baseline model.
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