Lifetime model of copper pillar micro-bump interconnects under bi-directional pulse current stress

The electromigration life of interconnects under pulsed current will change significantly compared to DC conditions. To accurately predict the reliability life of micro-copper pillar bump under pulsed current stress, in this paper, based on the built electromigration test system, accelerated life tests were carried out at 110°C, 125°C and 140°C temperature coupled 100Hz frequency bidirectional pulsed current 2.5-3.0 ×10
⁴
A/cm
²
. The effects of parameters such as temperature, current density, and forward current percentage on electromigration life were investigated. The reliability life model of micro-copper pillar bump interconnects under bi-directional current stress was successfully established by introducing a damage recovery factor γ into the Black equation. The modeling establishment process entirely considers the effect of the Joule heating effect, fitting the current density index n is 15.52, activation energy Q is 1.09 eV, and the damage recovery coefficient γ is determined to be -0.81. No significant correlation is found between γ and temperature and current density performance. The lifetime model shows that the change in current direction will slow down the electromigration effect of the micro bump but will not eliminate the resulting electrically induced damage. The mathematical relationships the model establishes between parameters such as temperature, current density, time proportion of the forward current, and electromigration lifetime of copper pillar bumps under bidirectional current are important engineering references to support high-density packages' design and lifetime prediction.