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-32BL 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 degrees 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.