TIN PLATING METHOD WHICH SUPPRESSES OXIDATION WITHOUT MIXING OF IMPURITY

摘要

PROBLEM TO BE SOLVED: To provide a tin plating method which suppresses the change of the divalent first stannous ion to the tetra-valent second stannic ion and prevents contamination of a tin-based plating solution with impurities.SOLUTION: Tin plating is carried out while the concentration of dissolved oxygen in a room-temperature tin-based plating solution of a ratio (M/M) of the concentration M(g/L) of the second stannic ion to the concentration M(g/L) of the first stannous ion of 0.01 or lower is kept in 1 ppm or lower by adding metal tin grains to the tin-based plating solution as a deoxidizer in the atmosphere of ambient air. The average grain size of the metal tin grains is preferably 1-10 mm. When 1 liter of the tin-based plating solution contains A(g) of the first stannous ion, A×(0.01-0.05)(g) of metal tin grains are preferably added.