The reversible transformation between Cu2(In, Sn) and Cu(In, Sn)2 compounds during solid-state aging

In this study, phase transformations at the interfaces between two nearly mutually insoluble elementary substances, In-48Sn solder and Cu, were investigated during serial solid-state aging process. The reversible phase transformation between Cu₂(In, Sn) and Cu(In, Sn)₂ compounds were observed, which are extremely rare to occur in one and the same system. The corresponding interfacial reactions were discussed according to physicochemical approach in detail. It was concluded that the diffusion ability of Cu and In, Sn atoms dominated different transformations at different temperatures. When the diffusion ability of In/Sn atoms is stronger than that of Cu, Cu₂(In, Sn) transforms into Cu(In, Sn)₂, while when the diffusion ability of Cu atoms is stronger than that of In/Sn, Cu(In, Sn)₂ transforms into Cu₂(In, Sn). The diffusion coefficients of Cu and In atoms at different temperatures on Cu substrate can be estimated by the growth kinetics of the compound layers.