The study on the rapidly-solidified Sn-0.7Cu lead-free solders and the interface reactions with Cu substrate

The rapidly-solidified lead-free solders had lower melting point, narrower melting interval, better wettability and improved mechanical performance because of the fine, uniform and small segregation microstructure compared with the as-cast lead-free solders. In this study, a rapidly-solidified Sn-0.7Cu eutectic alloy was used as a sample for investigating the microstructure, wettability and the Cu₆Sn₅ IMCs and their growth behavior formed between the solders and Cu substrate. In addition, an as-cast Sn-0.7Cu solder was prepared as a reference. The results of the study showed that the microstructure composition was more uniform, the wettability was much better, the melting rate was much faster of the rapidly-solidified Sn-0.7Cu solders than the as-cast solders; the morphology of Cu₆Sn₅ grains formed between solders and substrate was different between rapidly-solidified and as-cast Sn-0.7Cu solders in short soldering duration; the rapidly-solidified Sn-0.7Cu solders were suitable for soldering with low temperature and short duration.