Abstract: We investigated the electromigration mechanisms of Cu-Ni/solder/Ni-Cu structures.An electromigration process was observed when the applied average current density (0.4e4A/cm2) was lower than the threshold value for electromigration (1.0e4A/cm2).This was attributed to the maximum current density (5.83e4A/cm2) being much higher than the threshold value at the cathode area due to effects of current crowding.Because forced-convection heat transfer was introduced,the atoms’ thermal migration maximum was suppressed and did not disturb electromigration in the propagation stage.The electromigration force was dominant in this stage.In the quick-failure stage,atomic motion was driven by the cooperation of thermal migration and electromigration,which was generated by local temperature and the atoms thermal migration increasing rapidly and significantly.

Key words: SnCu solder, Ni-Cu layer, electromigration, intermetallic compound