Abstract
Interfacial reactions in the Sn/Co couples have been examined. The reaction temperature ranges from 150°C to 250°C and CoSn3 phase is the dominant reaction phases. The growth rates of the reaction phases are very fast, and the layer thickness increases with linearly with the reaction time in the initial stage of the reaction. A very unique cruciform pattern is formed in the Sn/Co couple reacted at 200°C. The reaction phase layers are thick and uniform along the edges of the Co substrate, and there are no reaction phases at the corners. For the Sn/Co couple reacted at 180°C, a metastable CoSn4 phase is formed at the corner in addition to the CoSn3phase formed along the edge of the Co substrate. The cruciform pattern of the reaction CoSn3 phase layer is formed either by cracking or transformation to the CoSn4 phase at the corners where stresses are most intensified