Abstract
Interfacial reactions of Sn-Cu alloys with Ni substrate at 250 °C have been investigated by varying the Cu contents from 0.3wt%Cu to 3.0wt%Cu. The Cu 6 Sn 5 phase is not found in the Sn-0.3wt%Cu/Ni couple. The interfacial reaction sequence of the Sn-0.6wt%Cu/Ni couple is similar to that of the Sn-0.7wt%Cu/Ni. The reaction follows Cu 6 Sn 5 formation stage, growth stage, detachment stage, Cu 6 Sn 5 layer continuing growth stage, Ni 3 Sn 4 formation stage, Cu 6 Sn 5 phase dissolution stage, Ni 3 Sn 4 detachment stage, and Ni 3 Sn 4 phase dissolution stage. Similar results are found for the couples prepared with higher Cu contents, 0.8wt%Cu, 1.0wt%Cu, 2.0wt%Cu, and 3.0wt%Cu, but the detachment positions are different. For the couples with higher Cu-content, the layer detaches at the Cu 6 Sn 5 /Ni interface; however, for the 0.6wt%Cu and 0.7wt%Cu couples, the Cu 6 Sn 5 phase layer fractures and detachment occurs inside the layer. Morphologies of the Cu 6 Sn 5 phase are also found to change with Cu contents: the pyramidal shape in the 0.3wt%Cu couple changes to the rod-shape in the 0.8wt%Cu couple, and becomes a very fine rod shape in the 2.0wt%Cu couple. © 2006 Materials Research Society.