Effect of Ni addition into the Cu substrate on the interfacial IMC growth during the liquid-state reaction with Sn–58Bi solder

The interfacial reactions between Sn–58Bi solder and Cu–xNi (x = 0, 0.5, 1.5, 5 and 10 wt.%) substrates at 200 °C with different liquid-state reaction durations were investigated to reveal the effect of the Ni addition into the Cu substrate on the growth of intermetallic compound (IMC), and grains evolution in this study. The results of this research indicated that addition of Ni significantly changed the interfacial microstructure of solder joints. Moreover, the formation of Cu3Sn was suppressed with the addition of Ni element, the Cu3Sn was only observed on Sn–58Bi/Cu–0.5Ni and Sn–58Bi/Cu–1.5Ni interfaces after liquid-state reaction for 150 min while Cu3Sn was completely eliminated when 5 or 10 wt.% Ni was added to Cu substrate regardless of the reaction time, and one new single phase (Cu,Ni)6Sn5 was formed between solder and Cu–Ni substrate. The total thickness increased as the liquid-state reaction time increased and the line relationship existed between total thickness and reaction time. The total thickness and growth rate of IMC gradually increased with the mass percentage of Ni increasing from 0 to 5 wt.% for the same liquid-state reaction time. In contrast, when the Ni content increased to 10%, the thickness and growth rate decreased slightly. The grain size became fine and the prismatic grain perpendicular to the interface tended to be dominant as the Ni element was added.