Simulation of electromigration induced stress of solder

Abstract

In this paper, failure modes of solder under electromigration were shown, the failure mechanism was usually attributed to tensile stress at cathode and compressive stress at anode. To evaluate the electromigration induced stress in solder, a finite element model was developed basing on the coupling equation of stress-mass diffusion with the aid of user development on the platform of ABAQUS. Simulation precision of the finite element model was confirmed with analytical results of a benchmark problem first. Then electromigration induced stress in solder was instigated with the finite element model, the maximum sphere stress was found to be about 50 MPa. Vacancy density and its variation with time were also investigated, it was found that vacancy density at cathode increased with current stressing time. These results can be used to interpret the electromigration induced failure and provide a basis for comprehensive evaluation of solder reliability.