Insights Into the Grain Orientation Effect on Electromigration-Induced Failure in Solder Interconnects Through Phase Field Modeling

A notable development of electronic packaging technologies drives that the solder interconnects include a few numbers of grains, leading to the grain orientation dependence of interconnect performance and reliably. It was experimentally observed that the void formation followed by open failure of the solder interconnects under high electric current stressing are significantly affected by the grain orientation of the Sn-based solder, but the quantitative mechanics are yet to be further understood. In this work, a phase field model is proposed to investigate the void formation and electromigration-induced failure behavior at the interface of the solder interconnects, especially being capable of considering the grain orientation effect. We found that the formation, growth, and propagation velocities of voids at the interface are faster in the solder interconnects with the c-axis of Sn perpendicular to the substrate. Moreover, it is demonstrated that more grains and a higher grain boundary diffusion coefficient promote void nucleation and growth, leading to an increase in electrical resistance and open failure. The diffusion flux analysis shows that the combined effect of surface, bulk, and grain boundary diffusions determines the magnitude of diffusion flux; thus, more diffusion channels or higher diffusion coefficients encourage void formation and propagation.

Automated summary

A notable development of electronic packaging technologies leads to fewer grains in solder interconnects, resulting in the grain orientation dependence of interconnect performance and reliability. The effect of grain orientation on void formation and electromigration-induced failure behavior of Sn-based solder interconnects is experimentally observed but not well understood. This study proposes a phase field model to investigate the void formation and electromigration-induced failure behavior at the interface of solder interconnects, with consideration of grain orientation effects. The results show that void formation, growth, and propagation velocities are faster when the c-axis of Sn is perpendicular to the substrate in solder interconnects.