Finite element simulation of the size effect on thermal fatigue behavior of solder bump joints in TSV structure

As the weakest parts in through silicon via (TSV) structures, solder bump joints bear cyclic thermal stresses under power cycling in service, which contribute to the fatigue of them. Meanwhile, the dimensions of solder bump joints keep shrinking due to the miniaturization of electronic systems and products. The size effect can have significant influence on thermal fatigue behavior of the joints. In this study, the effect of the volume and the diameter (d) on thermal fatigue behavior of solder bump joints in TSV structures under power cycling was investigated by finite element analysis (FEA). The fatigue life of each joint was calculated based on the Darveaux's energy theory. Simulation results show that the highest thermal stress locates at Cu/Si interfaces and solder bump joints alternately during the power cycling. Moreover, solder bump joints in the top and bottom arrays are more vulnerable compared with those in the middle array, and the outmost joints of each array are most dangerous. Furthermore, the fatigue life of solder bump joints is improved with increasing volume and decreasing d. For the prediction of fatigue life in this study, the von Mises stress is less important, while the creep strain has a significant influence on the creep energy density which is closely related to the fatigue life prediction.