Simulation of Average Strain Energy Density (SED) in the BGA Soldering during the Drop Test

Portable devices are commonly seen in our daily life, which leads to more attention to the issues of the mechanical reliability of ball grid array (BGA) soldering. This study aims to investigate the BGA soldering reliability based on the drop test conducted according to joint electron device engineering council (JEDEC) standard and to establish the Darveaux model by the data from the finite element analysis (FEA). Several constants in this model are calculated by the fatigue lifetime obtained from the drop test and average strain energy density (SED). By this modified model, once the average SED is obtainable, the fatigue lifetime of BGA soldering will be predictable. So effectively obtaining the average SED is essential to both the foundation of proper model and the sequent lifetime prediction. An effective way is developed to obtain the average SED from ANSYS/LS-DYNA explicit solve. The simulation reveals that under lower acceleration levels, the failures mainly occur in the solder-PCB interface. In contrast, under higher acceleration levels, the cracks are more likely to appear in solder-package interface. The main failure mechanism in both case s is the low-cycle-fatigue-induced crack at the interface