Improving the impact reliability of the Ni-doped solder joint by applying Cu-Zn under bump metallization

This study focuses on the correlation between the impact reliability and the interfacial reaction in Sn-3.0Ag-0.5Cu-0.1Ni/Cu (wt%) and Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joints. Adding Ni into the Sn-Ag-Cu solder can suppress the formation of Cu₃Sn and alter the morphology of the interfacial IMCs. Alternatively, replacing Cu substrates by Cu-Zn substrates can effectively limit the growth of Cu-Sn IMCs. In the Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joint, layer-type (Cu, Ni)₆(Sn, Zn)₅ is the dominate phase at the interface. Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joint exhibits the thinner IMCs after aging for 500h. Due to the effective suppression of interfacial reaction, the Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn joint significantly improve the impact reliability.