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 (mu)m to 580 (mu)m. At the Sn/Cu interface, both Cu_(6)Sn_(5) and Cu_(3)Sn are formed. Unlike in a binary Sn/Cu couple, Cu_(6)Sn_(5) has a spiked structure for couples with a thinner Sn layer. At the Co/Sn interface, two phases, CoSn_(3) and (Cu,Co)_(6)Sn_(5), were simultaneously observed after reaction at 200 deg C. Remarkably, the CoSn_(3) reaction layer was much thinner than that in the binary Sn/Co couple. Furthermore, only the (Cu,Co)_(6)Sn_(5) phase was formed at 150 deg C. This finding indicates that CoSn_(3) growth is significantly inhibited in Co/Sn/Cu sandwich couples due to the Cu substrate.