Solder electromigration behavior in Cu/electroless Ni–P plating/Sn–Cu based joint system at low current densities

Abstract

Electromigration (EM) in solder joints has great influence on their reliability. Nevertheless, few reports have been published on the EM in solder joints with Ni–P barrier layers at lower current densities less than 10 kA/cm2. In the present study, EM in Cu/Ni–P/Sn–0.7Cu/Ni–P/Cu joints was investigated at 150 °C with current densities of 5.0 and 7.5 kA/cm2. The breakdown mode was open failure of the solder joint on the cathode. It was found that Ni in the Ni–P barrier layer diffused toward the anode, resulting in a thicker P-rich layer, which caused the cracks and the delamination of the P-rich layer. Additionally, the diffusion of Sn detached the solder from the Ni3SnP intermetallic compound on the cathode.