Electrothermal coupling analysis of current crowding and Joule heating in flip-chip package assembly

Solder bumps serve as electrical paths as well as structural support in a flip-chip package assembly. Owing to the differences of feature sizes and electric resistivities between a solder bump and its adjacent traces, current densities around the regions where traces connect the solder bump increase in a significant amount. This current crowding effect along with the induced Joule heat would accelerate fatigue failure due to electromigration. In this paper we apply the three-dimensional electrothermal coupling analysis to investigate current crowding and Joule heating in a flip-chip package assembly subjected to a constant applied current. Predicted temperatures on the die and the solder bump are verified with experimental measurements.