Interfacial reactions between different Sn-based lead- free solder alloys and CuNi substrates

The effect of the presence of Ni in Cu substrates on the interface reaction during soldering and the growth of Sn-Cu intermetallic compounds (IMCs) was studied. The study involved reflow soldering of Sn-0.7Cu, Sn- 3Ag-0.5Cu and Sn-0.7Cu-0.05Ni lead-free solders on pure Cu and Cu-6Ni substrates with holding times of 5, 10 and 15 minutes at 232 °C. The presence of 6 wt% Ni in the Cu substrate strongly affects the microstructural evolution and the growth of the IMCs. The presence of Ni in the substrate significantly increased the overall thickness of the (Cu,Ni)6Sn5 layer while suppressing the formation of the Cu3Sn layer. The thickness of the (Cu,Ni)6Sn5 layer increased with reflow time for both Cu and Cu-6Ni substrate.