Characterization of intermetallic compounds formed during the interfacial reactions of liquid Sn and Sn - 58Bi solders with Ni substrates

Abstract The intermetallic compound that appears during the soldering reaction between pure Sn and Ni substrate at temperatures ranging from 250 to 400°C is analyzed to be Ni43Sn57. A similar reaction at the Sn-58Bi/Ni interface results in the formation of the Ni41.5Sn57.9Bi0.6 phase. At the Sn/Ni and Sn-58Bi/Ni interfaces, each kind of intermetallic compound formation exhibits a similar scallop-type morphology. However, the growth rate of intermetallic compounds at the Sn/Ni interface is greater than that at the Sn-58Bi/Ni interface. The growth kinetics for both cases is diffusion controlled. The activation energy for the intermetallic growth at the Sn/Ni interface is 43.7 kJ/mol, which is higher than that at the Sn-58Bi/Ni interface (28.3 kJ/mol).