Integrating electrothermal coupling analysis in the calibration of experimental electromigration reliability of flip-chip packages

The electromigration reliability of solder interconnects is dominated by the current density and the temperature inside the interconnects. For flip-chip packages, current densities around the regions where traces connect a solder bump increase by a significant amount owing to the differences in feature sizes and electric resistivities between the solder bump and its adjacent traces. This current crowding effect along with induced Joule heating accelerates electromigration failures. In this paper, effects of current crowding and Joule heating in a flip-chip package are examined and quantified through a three-dimensional electrothermal coupling analysis. We apply a volumetric averaging technique to cope with the current crowding singularity. The volumetrically averaged current density and the maximum temperature in a solder bump are integrated in the Black's equation to calibrate experimental electromigration fatigue lives.