Interfacial reactions of Sn-Cu/Ni couples at 250 °C

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 Cu₆Sn₅ 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 Cu₆Sn₅ formation stage, growth stage, detachment stage, Cu₆Sn₅ layer continuing growth stage, Ni₃Sn₄ formation stage, Cu₆Sn₅ phase dissolution stage, Ni₃Sn₄ detachment stage, and Ni₃Sn₄ 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 Cu₆Sn₅/Ni interface; however, for the 0.6wt%Cu and 0.7wt%Cu couples, the Cu₆Sn₅ phase layer fractures and detachment occurs inside the layer. Morphologies of the Cu₆Sn₅ 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.