Fabrication of High-Temperature Solder by Zn Plating Films Containing Al Particles

Abstract

This study investigated the microstructure and melting point of the Zn–Al composite electroplating film. The cross-sectional microstructure and shear strength of the joints made from the plating films were also evaluated. Zn and Al were confirmed in the plating films from initial microstructure observation. The plating film prepared by a plating bath without cationic surfactant melted near the melting point of Zn and the eutectic point of Zn–Al. When jointed at a joining temperature of 443°C, joining pressure of 5 MPa, and holding time of 5 min, multiple intermetallic compounds, Zn–Al eutectic layers, and unreacted Al particles were observed in the joint layer. From quantitative analysis, the multiple intermetallic compounds were estimated to be Zn–Ni and Zn–Al–Ni intermetallic compounds. The shear strength of the joints increased with increasing joining pressure but was lower than that of Sn–5Sb solder. Fracture after the shear test was observed at the interface between unreacted Al particles and Zn–Al–Ni intermetallic compounds, and inside unreacted Al particles.