Control of compound forming reaction at the interface between SnZn solder and Cu substrate

Effects of additives, Cu and Ni, on intermetallic compound formation at the interface between Sn-Zn-based solder and Cu substrate have been studied. (Sn91Zn9)99.98−xMxAl0.02 (wt.%) solder (M = Cu or Ni) alloys were prepared. The microstructures of the samples after annealing at 120 °C for 100 h were investigated using a scanning electron microscope, and the melting temperatures of the alloys were measured with a differential scanning calorimeter for different Cu or Ni contents. Although the melting (liquidus) temperature increases up to about 210-220 °C by alloying Cu or Ni of 2.6-2.7 wt.% to the solder, the well-known formation of intermetallic compounds, Cu5Zn8 and Sn6Cu5, are found to be significantly restrained.