Interfacial reaction and morphology between molten Sn base solders and Cu substrate

Abstract

The morphologies and growth of ε(Cu3Sn) and η(Cu 6Sn5) intermetallic compounds (IMCs) between a molten Sn base solder and a Cu substrate were experimentally investigated. It is shown that the thickness of the ε(Cu3Sn) and η(Cu 6Sn5) compounds decreases with deceasing Sn content and that the order of the growth rate of the compounds on the Cu substrate are as follows: Sn-57(mass%)Bi < Sn-37Pb < Sn-3.5Ag < Sn < Sn-6.7Sb. The growth of these phases basically obeys the parabolic law, but the growth behavior is divided into two stages, the growth rate and morphology of the η(Cu6Sn5) compound are differing from each other in the two-stage. It is suggested that the grooving effect is at least one of the origins of the formation of the scallop morphology of the η(Cu 6Sn5) compound.