Interfacial reactions at 100C with and without the passage of electric currents were studied by using Sn/Ni/Sn sandwich-type reaction couples. The Ni3Sn4 and metastable NiSn3 phases were formed at both the Sn/Ni and Ni/Sn interfaces in couples reacted at

100C without passing electric currents. Metallographic analyses revealed that the metastable NiSn3 phase nucleated and grew at the grain boundary, and the growth rate of the NiSn3 phase was much faster than that of the Ni3Sn4 phase. In couples through which were passed currents of 4 x 103A/cm2 density, Ni3Sn4 reaction layers were found at both interfaces as well. However, the NiSn3 phase was found only at the Ni/Sn interface where the directions of electron flow and Ni diffusion were the same, and the NiSn3 phase was not found at the Sn/Ni interface. The NiSn3 phase formed at the Ni/Sn interface was found to nucleate and grow much faster than those without the passage of electric currents. It was thought likely that the electromigration effect enhanced the movement of Ni atoms and accelerated the nucleation and growth of the NiSn3 phase while at the Sn/Ni interface, where the directions of electron flow and Ni diffusion were opposite, electromigration effects retarded the movement of Ni atoms and inhibited nucleation of the NiSn3 phase.

Electromigration Effects upon the Low-Temperature Sn/Ni Interfacial Reactions. C.Chen, S.Chen: Journal of Materials Research, 2003, 18[6], 1293-6