SAC305 Solder Electromigration Kinetics

Studying electromigration in SAC305 solder at low current densities and low temperatures resembling the application conditions is challenging due to the low rates of electromigration and the homogeneous nature of the alloy consisting mainly of tin.  This paper takes a straightforward approach of studying electromigration in SAC305 solder by measuring the rates of resistance changes as a function of time at various temperatures and current densities.  Electromigration rates were measured over at least 2-month period for each condition.  The resistance readings were corrected for minor temperature changes to obtain more accurate rates of change of resistance.  The low rates of change of resistance also necessitated the inclusion of the Cu-Sn intermetallic growth contribution to the resistance values. The micro-structures before and after the test were compared to shed light on the physical metallurgy of electromigration in SAC305 solder.  The electromigration results will be presented in the form of an Arrhenius plot that can be used to predict the electromigration life of a SAC305 solder under any temperature and current density application condition.