The mechanical and electrical reliability of Cu/Sn–3.5Ag microbumps under both annealing and current-stressing conditions were systematically evaluated. Intermetallic compound (IMC) growth was controlled by a diffusion-dominant mechanism and a chemical reaction-dominant mechanism with annealing and current-stressing time, respectively. The transition time for IMC phase change had an inverse relationship with current density because of the electron wind force under current stressing conditions. The shear strength and IMC thickness increased monotonically with annealing time at 150 °C, while the amount of solder decreased. It was clearly revealed that strong correlations exist between IMC growth kinetics, shear strength, and fracture modes in Cu/solder microbumps.

No abstract