Influences of Ag and Zn contents on interfacial microstructure and corrosion behavior of Sn–Zn–Ag/6061Al joints in antenna module packages

In this study, the influences of Ag and Zn contents on the interfacial microstructure and corrosion behavior of Sn-Zn-Ag/6061Al joints aiming at 4G/5G antenna module packages were investigated using scanning electron microscopy (SEM) and potentiodynamic polarization measurement, respectively. Results show that Al-rich phase detaches from 6061Al substrate and forms Al-Zn-Sn solid solution in the solder matrix; meanwhile a continuous Ag-Zn intermetallic compound (IMC) layer forms near the interface when adding Ag to the solder, resulting in the roughness interface between the solder and 6061Al. In Sn-Zn-Ag/6061Al joints, 6061Al substrate acts as an anode and corrodes preferentially. Intergranular corrosion occurs in 6061Al and the crack initiates at the edges of joints. Simultaneously, the aggressive Cl
^-
penetrates into the crack, which accelerates the corrosion, and the crack propagates rapidly along the interface, resulting in the failure of solder joints. Among the solders with different Ag and Zn contents in this study, Sn-6Zn-1.5Ag/6061Al joints exhibit superior corrosion resistance.