Abstract: The cross-sectional microstructures of joints with Sn37Pb, Sn3.0Ag0.5Cu, and Sn0.7Cu under electromigration were investigated. At a temperature of 60℃ and current density of 1e3A/cm2,after 187h, micro-voids form at the electron entrance of the Sn37Pb solder/Cu interface, and strip-like Pb enriches the anode side. For Sn3.0Ag0.5Cu, electromigration only results in the dissolution of the substrate Cu at the cathode side, and the thicknesses of the Cu6Sn5 and Cu3Sn intermetallic layers at the anode side are markedly bigger than the counterparts at the cathode. Likewise, the Cu6Sn5 and Cu3Sn intermetallic layers at the anode side are thicker than the counterparts at the cathode, indicating that EM also occurs in the Sn0.7Cu joint, but little Cu dissolves into the solder at the cathode side.

Key words: Sn37Pb,  Sn3.0Ag0.5Cu,  Sn0.7Cu,  electromigration,  microstructure