Formation and growth of intermetallic compounds of Sn-2Ag-2.5Zn on Cu and Ni substrates

The formation and growth of intermetallic compounds of Sn-2.0Ag-2.5Zn solder on Cu and Ni substrates after soldering and subsequent aging process have been investigated in this study. Ni films were electrodeposited on copper substrates. The interfacial micrographs of solder joints prepared at 250°C for 15s and aged for 24h, 96h and 216 h respectively. Double-layer IMC composed with Cu₅Zn₈ and Ag₃Sn was observed at the interface of Sn-2Ag-2.5Zn and Cu couple, which was compact and acted as a barrier layer to confine the further growth of Cu-Sn IMC. On Ni barrier layer, a thin Ni₃Sn₄ film appeared between the solder and Ni-W layer, which is thin and smooth. After aging process, the thickness increased slowly and steadily, which revealed that Ni barrier layer acts as a promising barrier layer.