A lead-free solder which can reduce the occurrence of voids and a connecting member which uses the solder and has excellent adhesion, bonding strength, and workability are provided. The lead-free solder alloy contains Sn: 0.1-3% and/or Bi: 0.1-2%, and a remainder of In and unavoidable impurities and has the effect of suppressing the occurrence of voids at the time of soldering. The connecting member is prepared by melting the lead-free solder alloy, immersing a metal substrate in the melt, and applying ultrasonic vibrations to the molten lead-free solder alloy and the metal substrate to form a lead-free solder alloy layer on the surface of the metal substrate. A heat sink and a package are soldered to each other through this connecting member by reflow heating in the presence of flux.