Silver plating bath for copper-based material

PROBLEM TO BE SOLVED: To form a white dense silver film upon substitution silver plating on a copper-based material. SOLUTION: A soluble silver salt and a base acid are contained, and a specific thioaminocarboxylic acid or a salt thereof (such as methionine), an aliphatic mercaptocarboxylic acid or a salt thereof (such as a mercaptosuccinic acid), sulfides, etc. 2- (2-hydroxyethylthio) ethanesulfonic acid, 3,6,9-trithiaundecane-1,11-disulfonic acid, etc.), thiourea derivatives (1,3-bis (3-pyridylmethyl) -2- A substituted silver plating bath in which thiourea or the like is selected. Since the specific sulfur-containing compound is used as a complexing agent, the electrode potential difference between the complexed copper ions and silver ions can be appropriately adjusted, and a white and dense silver film can be obtained. [Selection figure] None