Abstract
Sn-Zn-based alloys are promising low melting-point Pb-free solders, and it has been reported that their wetting properties and oxidation resistance can be improved with the addition of Cu. The interfacial reactions in the Sn-9 wt% Zn-xCu/Cu couples at 250 °C and Sn-9 wt% Zn-xCu/Ni at 280 °C were examined in this study. A thick γ-Cu 5 Zn 8 phase layer and a very thin β′-CuZn phase layer were formed in both the Sn-9 wt% Zn/Cu and the Sn-9 wt% Zn-1 wt% Cu/Cu couples. The γ-Ni 5 Zn 21 phase layer was formed in both the Sn-9 wt% Zn/Ni and Sn-9 wt% Zn-1 wt% Cu/Ni couples. With longer reaction time, the δ-Ni 3 Sn 4 phase were formed in the Sn-9 wt% Zn/Ni couple as well. In both the Cu and Ni couples, the Zn-containing γ phases were uniform and planar and were the dominant reaction products. However, when the Cu content of the Sn-9 wt% Zn-xCu solders was 10 wt%, the interfacial reaction product becomes the η-Cu 6 Sn 5 phase in both the Cu and Ni couples. © 2006 Materials Research Society.