Interfacial reactions of 68In–32Bi, 50In–50Bi and 33In–67Bi low melting alloys on Cu substrates

In this study, the interfacial reactions, microstructures, and intermetallic compounds (IMCs)of 68In–32Bi, 50In–50Bi, and 33In–67Bi (in weight percent)low melting alloys reacted with Cu substrates were investigated. CuIn₂, Cu₁₁In₉, and Cu₂In IMCs formed at the interface in different In–Bi/Cu systems and were characterized by grazing incidence X-ray diffraction (GIXRD)and electron probe X-ray microanalyzer (EPMA). The CuIn₂ and Cu₁₁In₉ IMCs formed at the interface phase transfer to Cu₁₁In₉ when annealing temperature was greater than 70 °C. CALPHAD-type thermodynamic calculations were performed to illustrate the corresponding diffusion paths. Moreover, shear tests were conducted and indicated that 50In–50Bi solder joint provide the highest shear strength among the three alloys.