Electromigration induced failure on lead-free micro bumps in three-dimensional integrated circuits packaging

Abstract

We report electromigration induced failure on lead-free micro bumps in three-dimensional integrated circuits samples with chip on chip configuration. Compared to flip chip solder joints, micro bumps of chip-on-chip samples exhibit better electromigration resistance and are able to withstand a higher current density. No exhibited electromigration-induced failure was observed when current density was below 2 × 10 4 A/cm 2. A threshold current density to trigger electromigration in chip-on-chip samples was found to be 3.43 × 10 4 A/cm 2. When current density was higher than 7.5 × 10 4 A/cm 2 at an ambient temperature of 150°C, no void propagation through whole bump opening was found; instead, electromigration induced voids were observed at the cathode side of Al trace. © 2012 American Institute of Physics.