Electromigration-induced failures at Cu/Sn/Cu flip-chip joint interfaces

Various EM-induced failures were observed at a current-stressed Cu/Sn/Cu flip-chip solder joint. At the cathode interface, EM-induced Cu-pad consumption occurred at the current-entry point (maximum current-density) and voiding occurred at the other joint corner away from the current-entry point (minimum current-density). At the anode interface, EM-enhanced Kirkendall voids coalesced into a gap at the Cu3Sn/Cu interface near the current-exit corner. We believe that the above various EM-induced failure modes were resulted from different current-stressing densities at the joint interfaces.