Texture evolution and its effects on growth of intermetallic compounds formed at eutectic Sn37Pb/Cu interface during solid-state aging

Abstract

The growth orientation of Cu6Sn5 intermetallic compounds (IMCs) formed at the eutectic Sn37Pb/polycrystalline Cu interface during solid-state aging was investigated. The results indicate that the interfacial Cu6Sn5 grains exhibit textured growth under solid-state conditions, and their preferred orientations are affected by the initial joint preparation conditions. Cu6Sn5 grains in the [0001] direction normal to the interface are stable in solid and molten Sn37Pb solder at 200°C, but are rapidly consumed at 280°C. This effect leads to the formation of different textures in the Cu6Sn5 layer during the solid-state aging treatment of joints formed at 200 and 280°C. In addition, the influence of texture evolution on the growth of interfacial IMCs was evaluated. The results indicate that Sn diffusion is faster along the [0001] direction of the Cu6Sn5 crystal than along an angle of 25–45° to the [0001] direction; therefore, more IMCs are generated at the interface of the joints formed at 200°C than at those formed at 280°C under the same solid-state reaction conditions.