Investigations of solder joint damage potentials for board-level chip-scale packages subjected to consecutive drops

Transient structural responses of a board-level chip-scale package subjected to consecutive drops are investigated in this paper using a numerical methodology based on the support excitation scheme and incorporated with the implicit time integration scheme. Evolutions of stresses, plastic strains, and plastic strain energies in the solder joints under repetitive drop impacts are examined and correlated with actual experimental observations. Effects of isotropic hardening and kinematic hardening presumed for the solder alloy are examined and compared. The numerical results indicate that under kinematic hardening, during the course of repetitive drop impacts, maximum and residual stresses remain nearly constant while plastic strains and plastic strain energies increase almost linearly. On the other hand, under isotropic hardening, as the drop count increases, maximum stresses increase while the incremental plastic strain energy decreases.