Investigation of the Sn-0.7 wt.% Cu Solder Reacting with C194, Alloy 25, and C1990 HP Substrates

Cu-based alloys are one of the most promising substrates to enhance the performance of lead-frame materials. In the present study, the interfacial reactions in the Sn-0.7 wt.% Cu (SC) lead-free solder reacting with Cu-3.3 wt.% Fe (C194), Cu-2.0 wt.% Be (Alloy 25), and Cu-3.3 wt.% Ti (C1990 HP) were investigated. The material underwent a liquid–solid interface reaction, and the reaction time was 0.5 to a few hours at the reaction temperatures of 240 °C, 255 °C, and 270 °C. The morphology, composition, growth rate, and growth mechanism of the intermetallic compounds (IMCs) formed at the interface were investigated in this study. The results showed that the reaction couples of SC/C194, SC/Alloy 25, and SC/C1990 HP formed IMCs, which were the [(Cu, Fe)6Sn5 and (Cu, Fe)3Sn], [(Cu, Be)3Sn and (Cu, Be)6Sn5], and [Cu6Sn5] phases, respectively. Finally, the IMC growth mechanism for the SC/C194, SC/Alloy 25, and SC/C1990 HP couples displayed reaction control, grain boundary diffusion control, and diffusion control, respectively.