材料期刊网

The microstructure of the eutectic SnBi/Cu interface was investigated by transmission electron microscopy to study the growth mechanisms of the intermetallic compounds (IMCs). Although the growth kinetics of the total IMC layer were similar, the individual Cu(3)Sn layer grew faster on polycrystalline Cu than on single-crystal substrates. It was found that, on polycrystalline Cu, newly formed Cu(3)Sn grains with a smaller grain size nucleated and grew at both the Cu/Cu(3)Sn and Cu(3)Sn/Cu(6)Sn(5) interfaces during reflow and solid-state aging. The consumption of Cu(6)Sn(5) to form Cu(3)Sn was faster at the Cu(3)Sn/Cu(6)Sn(5) interface. While on single-crystal Cu new Cu(3)Sn grains nucleated only at the Cu/Cu(3)Sn interface, the directional growth of the initial columnar Cu(3)Sn controlled the advance of the Cu(3)Sn/Cu(6)Sn(5) interface.