Low silver lead-free solder joint reliability of VFBGA packages under board level drop test at −45°C

Based on the JEDEC standard, the three-dimensional finite element model of board level VFBGA package components was established, and the reliability of low silver lead-free solder Sn0.3Ag0.7Cu under drop impact was observed. The results show that, the mechanical impact and bending of PCB caused by mechanical shock are the main reasons which induce the drop failure of solder joint in the drop impact conditions; it is not neglect to consider the strain rate and thermal effect of solders in numerical simulation; as for low silver lead-free solder Sn0.3Ag0.7Cu, the distribution of the maximum stress on the joints was observed in the interface of the solder joints at low temperature; compared with high silver solder, the stress around test plate side silver solder is greater than that around the side of the package, while high silver solder just the opposite; and the maximum stress of low silver lead-free solder is much lower than that of the high silver solder, which shows better resistance to drop.