Sn/Ni–Co solid/solid interfacial reactions

Solid state interfacial reactions in Sn/Ni–Co couples are examined in this study. The Ni–Co alloys examined are Ni–10 at%Co, Ni–20 at%Co, and Ni–40 at%Co. The major reaction phases are the CoSn2 and (Ni, Co)Sn4 phase. The reaction phases grow thicker with the longer reaction time and higher temperatures. No Sn–Ni binary compound is formed. With the increase of the Co content from 10 at% to 40 at%, the main reaction phase changes from the CoSn2 phase to the (Ni, Co)Sn4 phase, and the reaction rate increases first, and then decreases. The reaction constants at 120, 150, and 200 °C in the three different reaction couples are determined. Sn/Ni–40 at%Co couples are with the smallest reaction rate. The determined activation energy of the interfacial reactions in the Sn/Ni–10 at%Co, Sn/Ni–20 at%Co, and Sn/Ni–40 at%Co couples are 65.4, 44.8, and 63.5 kJ/mol, respectively. Reaction rates in Sn/Ni–Co couples are higher than that in Sn/Ni couples.