Cross-solder interaction on interfacial reactions in Ni/Sn-3.0Ag-0.5Cu/Cu solder interconnects

Synchrotron radiation real-time imaging technology was performed to in situ study the effect of Cu-Ni cross-solder interaction on liquid-solid interfacial reaction in Cu/Sn-3.0Ag-0.5Cu/Ni micro interconnects at 221°C. For Cu/Sn-3.0Ag-0.5Cu interconnect, the scalloped IMC remained its shape grew slightly larger with prolonged reaction time. However, with Ni substrate added on the opposite interface, the scallop grains were split into smaller grains. Besides the opinion that Ni can improve the nucleation rate of Cu₆Sn₅ on Cu interface and inhibit grain coarsening, the liquid solder/Cu₆Sn₅ interfacial energy change and the grooving effect by the addition of Ni played an important role on the growth behavior of Cu₆Sn₅.