Effect of Intermetallic on Electromigration and Atomic Diffusion in Cu/SnAg3.0Cu0.5/Cu Joints: Experimental and First-Principles Study

Abstract

0.5 /Cu joint were investigated with current stressing. The special effect of intermetallic compound (IMC) layers on the formation of serious electromigration damage induced by nonuniform current density distribution was discussed based on experimental results. Meanwhile, hillocks were observed both at the anode and near the cathode of the joint, and they were described as the result of diffusion of atoms and compressive stress released along grain boundaries to the relatively free surface. Moreover, the diffusion behavior of Cu at the cathode was analyzed with the electromigration equation, and the stability of Ag atoms in the solder during electromigration was evaluated with a firstprinciples method.

Electromigration-induced accelerated consumption of Cu pad in flip chip Sn2.6Ag solder joints

“…The electron flow through thinner Cu 6 Sn 5 IMC was easier than thicker Cu 6 Sn 5 IMC which induced local current crowding areas during current stressing. [19] On top of that, morphology of Cu pad would also affect the current distribution. [20,21] Within the Cu pad, the distance for electron flowing into the solder at tip location of an electrode is shorter than that at concave location.…”