Electrorefining is a method for recycling solder material. After applying constant current electrolysis to a Sn anode material containing Bi and/or Sb as impurities, we performed cross-sectional observation and mapping analysis of the generated anode slime layer. Our findings confirmed that the Sn anode electrode composition affects the generated anode slime shape. The anode slime layer generated from anode material containing Bi and Sb in a specific ratio exhibited a network-like structure. This structural change apparently has an anti-passivation effect. Mapping analyses of some samples used for this experiment revealed S-rich layers between the electrode and slime layer. We infer that S enrichment is attributable to the formation of Sn-S-O compounds and that the Sn-S-O compound formation causes passivation of electrodes. Ease of forming Sn-S-O might depend on the slime layer structure and other factors.

This study investigated plating bath additive effects on the improvement of electroless Ni-Sn plating film resistance against aqueous sodium hypochlorite solutions. Surfaces of conventional electroless Ni-Sn coatings show numerous cracks and pinholes. Through these gaps, a sodium hypochlorite aqueous solution can corrode the substrate, thereby decreasing the chemical resistance of the plated coating. A plating solution bath to which a combination of thiourea and hydroquinone had been added reduced the internal stress of the plating film, suppressed the rate of crack formation on the film surface, and reduced pinhole formation. Findings also revealed that the resultant film had higher resistance than conventional Ni-Sn films.