Damage of SAC405 solder joint under PDC

Pulse current induced electromigration (EM) damage of lead-free 95.5%Sn-4.0%Ag-0.5%Cu (SAC405) microelectronics solder joints has been investigated numerically. Solder joints were subjected to 0.05 Hz to 20 Hz pulse current loading with maximum current density varying between 10⁵ A/cm² and 10⁶ A/cm² at an ambient temperature of 353 °K. Entropy based damage evolution model was used in this work, which uses the irreversible entropy production rate as a measure of material damage. Thermal fluctuation period is 72s, which lags far behind the current loading period. Low cycle thermal fatigue may happen at current crowding corner. The EM induced damage develops exponentially during the whole loading history. It is observed that increasing duty factor and frequency leads to a faster damage accumulation. EM and thermomigration (TM) induced damage was found proportional to r^1.3, f^1.5 and j^2.3.