GU Tianliang, YAN Yanfu, ZHANG Shaoqi
Mixed rare earth metals, which were composed of La powder and Nd powder, was added into Zn9.3Al7Cu alloy solder with mass fractions of 0, 0.1%,0.3%,0.5%, respectively. The effects of mixed rare earth content on the melting point, wettability, microstructure, and on the shear strength of Cu/Al solder joint were studied. The results show that the microstructures of the alloy solders consisted of η(Zn) phase, ε(CuZn5) phase, β(ZnAl) eutectoid phase. The addition of the mixed rare earth resulted in the refinement and evenly distribution of the large dendritic ε(CuZn5) phase. With increasing content of mixed rare earth, the melting points of the alloy solders decreased while the wettability of the solder and the shear strength of the Cu/Al solder joint first increased and then decreased. When the mass fraction of the mixed rare earth was 0.1%, the spread areas of the solder on Al and Cu plates reached the maximum values, which were 20.4% and 46.6% higher than those without rare earth, respectively; the interface between the wetted Al plate by the solder became continuous without defects; the shear strength of Cu/Al joint welded with the alloy solder reached the maximum value of 66.5 MPa, which was 32.5% higher than that without rare earth.
