SOLDERING METHOD AND BASIC SOLDERING MATERIAL

PROBLEM TO BE SOLVED: To prevent defective joint due to cracking by forming a nickel skin layer on the surface of a basic material principally comprising copper and forming a thin layer of gold, silver, palladium or tin on the surface of the nickel skin layer thereby blocking undue growth of a compound layer under high temperature. SOLUTION: Since a nickel skin layer is formed on the surface of a basic material principally comprising copper, copper is diffused into the nickel skin layer when solder adheres onto the basic material and boded through formation of a compound with zinc in the solder. Consequently, the solder is jointed surely to the basic material. Since wettability of tin-zinc based solder to nickel is insufficient when the nickel skin layer is formed simply on the surface of the basic material of copper, initial strength can not be ensured sufficiently. When a thin layer of gold, silver, palladium or tin is formed on the surface of the nickel skin layer, wettability of solder to the surface of the basic material is improved resulting in good soldering and enhanced initial strength.