Coupling Effect of the Interfacial Reaction in Co/Sn/Cu Diffusion Couples

摘要

Co/Sn/Cu sandwich couples formed by electroplating were examined to investigate the interaction between Cu and Co across the Sn layer for various Sn thicknesses from 75 μm to 580 μm. At the Sn/Cu interface, both Cu₆Sn₅ and Cu₃Sn are formed. Unlike in a binary Sn/Cu couple, Cu₆Sn₅ has a spiked structure for couples with a thinner Sn layer. At the Co/Sn interface, two phases, CoSn₃ and (Cu,Co)₆Sn₅, were simultaneously observed after reaction at 200°C. Remarkably, the CoSn₃ reaction layer was much thinner than that in the binary Sn/Co couple. Furthermore, only the (Cu,Co)₆Sn₅ phase was formed at 150°C. This finding indicates that CoSn₃ growth is significantly inhibited in Co/Sn/Cu sandwich couples due to the Cu substrate.