Abstract
The results contained within this paper examine the combined influence of electromigration stressors (elevated current density and elevated ambient temperature) and tensile stress on the lifetime of SAC305 solder joints (300[μm] diameter) compared to either individual stress condition acting singularly. Tensile stresses of 0 to 5 [MPa] were applied to samples already experiencing electromigration conditions of 9,100 [A/cm2] (4.611 [A]) at ambient temperatures of 100 and 150 [°C]. The testing duration was limited to 48 hours per sample. All samples tested without an applied tensile stress (i.e. 0 [MPa]) survived the 48 hour period. The same was true for only five of 24 samples tested under combined electromigration and tensile stressing conditions. Post failure analysis of the samples tested under combined electromigration and tensile stress showed necking or breakage at the Cu/SAC305 interface on the upstream side of electron flux. Cross-sectional analysis of tested samples is consistent with findings from other studies regarding electromigration failure in Cu/SAC305/Cu solder joint assemblies, where the intermetallic regions at Cu/SAC305 interfaces grow asymmetrically. Inherent process-voids in the experimental samples are discussed as a source of error and a brief computational examination of the impact of process-related voiding on current density and self-heating within solder samples is provided.
