Ni Interdiffusion Coefficient and Activation Energy in Cu6Sn5

Abstract

Ni diffusion in Cu6Sn5 intermetallic compound was investigated. First, we successfully fabricated preferred-orientation Cu6Sn5 crystal by liquid-phase electroepitaxy (LPEE). Then, Ni/Cu6Sn5 diffusion couples were produced by sputtering from a Ni thin film onto the Cu6Sn5 crystal. Ni/Cu6Sn5 diffusion couples were annealed at different temperatures of 120°C, 160°C, 200°C, 255°C, 290°C, and 320°C for 2 h in a vacuum. The Ni atomic profile across the Ni/Cu6Sn5 interface was obtained by electron spectroscopy for chemical analysis (ESCA). From the Ni atomic profiles, the Matano method was used to evaluate the Ni interdiffusion coefficients (\( \tilde{D}_{\rm{Ni}} \)) in the Cu6Sn5 crystal obtained with different annealing temperatures, which then yields the activation energy for Ni diffusion in the Cu6Sn5 crystal at a particular Ni content. We found that, as Ni diffuses in the ternary Cu6−xNixSn5 compound phase, the activation energy of Ni interdiffusion decreases with the Ni content.