Patent ID: 6896172

Claim:
A method of soldering a surface mounted device comprising performing reflow soldering using a lead-free solder paste including a plurality of different types of metal powder mixed with a flux, one of the metal powders being a Sn alloy powder, another of the metal powders being selected from a Sn alloy powder, elemental Ag powder, elemental Cu powder, and elemental Sn powder, each Sn alloy powder including 0-8 mass % of Ag, 0-5 mass % of Cu, and at least 80 mass % of Sn, the plurality of metal powders having a composition when melted of 1-5 mass % Ag, at least 0.5 and less than 3 mass % Cu, and a remainder of Sn, the reflow soldering including melting the plurality of metal powders in the solder paste.