Investigations of Sn-9Zn-Ag-Ga-Al-Ce Solder Wetted on Cu, Au/Ni/Cu, and Sn-plated Cu Substrates

Interfacial reaction products between Sn-9Zn-0.25Ag-0.2Ga-0.002Al-0.15Ce solder and Cu, Au/Ni/Cu, Sn-plated Cu substrates were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD), while the hardness and indentation modulus of the interface reaction products were studied by the nanoindentation technique (NIT). The SEM and XRD results indicated that interfacial reaction products between solder and substrates were Cu5Zn8, AgZn3, AuZn3, and Ni(5)ZSn(21). A Cu5Zn8/ Sn/Cu5Zn8 sandwich structure formed at the interface between solder and Sn-plated substrate. The hardness and modulus values of Cu5Zn8 and Ni5Zn21 obtained through NIT were noticeably high, while that of Sn-9Zn-0.25Ag-0.2Ga-0.002Al-0.15Ce solder was low, exhibiting significant plasticity. Moreover, the wetting balance test and mechanical property test indicated that Sn-9Zn-0.25Ag-0.2Ga-0.002Al-0.15Ce solder exhibited good solderability on Sn-plated Cu substrate, and the application of Au/Ni/Cu substrate may enhance the soldered joints.