Abstract: Sn-(20-x)Bi-xIn (x=0,1,2,3,4,5, mass fraction/%) solder was prepared, and its melting and wetting properties were analyzed. Brazing experiments were conducted on copper substrate with Sn-(2-x)Bi-xIn solder, and the effect of indium content on the microstructure at the brazing interface was studied. The results show that with the increase of indium content, the melting point of the solder decreased. When the mass fraction of indium was 5%, almost no eutectic structure was formed in the solder. The wetting angle of the solder first decreased and then increased, and the wetting area first increased and then decreased with increasing indium content. When the mass fraction of indium was 4%, the wettability of the solder was the best. The thickness of intermetallic compound layer at the brazing interface increased, and the composition of the intermetallic compound changed from Cu₆Sn₅ to Cu₆Sn₅ and Cu₆(InSn)₅.