Effects of rare earth La on microstructure and properties of Ag–21Cu–25Sn alloy ribbon prepared by melt spinning

Abstract Ag–21Cu–25Sn alloy ribbon as a promising intermediate temperature alloy solder (400–600 °C) was prepared by melt spinning technique in this paper. Rare earth La was added into Ag–21Cu–25Sn alloy to refine the microstructures and improve the wettabilities of as-prepared alloy solders. The phase constitutions, microstructures, melting temperatures and wettabilities of selected specimens were respectively tested. The results showed that the dominant phase constitutions of Ag–21Cu–25Sn– x La alloy ribbons were Ag 3 Sn and Cu 3 Sn. The grain size of Ag–21Cu–25Sn– x La alloy decreased with the addition of La increasing. La addition reduced the melting temperatures of Ag–21Cu–25Sn– x La alloy ribbons, and effectively improved the wettabilities of the alloy ribbons. When the addition of La was 0.5 wt%, the wettability of as-prepared alloy solder achieved the optimal value of 158 cm 2  g −1 under brazing temperature 600 °C and dwell time 15 min. In addition, raising brazing temperature and prolonging dwell time could improve the wettability of Ag–21Cu–25Sn– x La alloy ribbon.