Phase field simulation of morphological evolution and migration of the microvoid in small scale solder interconnects driven by temperature gradient

Thermomigration issue has attracted increasing attention as it can induce the failure of solder interconnects, owing to the migration of atoms driven by heat flux. Further, thermomigration can promote the formation of microvoids, and also induces the evolution and migration of many other types of microvoids in solder interconnects, resulting in loss of the integrity of solder interconnects and a dramatic decrease of the reliability, in particular for the solder interconnects under high temperature gradient. In this paper, a phase field model is developed and employed to simulate the evolution and migration behavior of microvoids in solder interconnects under the applied temperature gradient. Simulations take into account the coupled effect of surface diffusion and temperature gradient, and the feasibility and validity of this method are confirmed. The results show that for the solder interconnect containing an initially circular void in microscale, the microvoid migrates to the cold regions along the temperature gradient. In addition, under a higher temperature gradient, the microvoid migrates with higher speed and its shape becomes unstable, which will increase the potential of failure in solder interconnects. Moreover, the temperature gradient can drive two microvoids to migrate and coalesce to a large micorvoid, and eventually a slit-like void is formed. Finally, the microvoid migration kinetics is also investigated, and the result is consistent with the analytical solution.