Silver and silver alloy plating bath

Abstract

A silver and silver alloy plating bath, includes (A) a soluble salt, having a silver salt or a mixture of a silver salt and a salt of a metal such as tin, bismuth, indium, lead, and the like; and (B) a particular aliphatic sulfide compound, such as thiobis(diethyleneglycol), dithiobis(triglycerol), 3,3′-thiodipropanol, thiodiglycerin, 3,6-dithiooctane-1,8-diol, and the like, which contain at least one or more of an ether oxygen atom, a 1-hydroxypropyl group, a hydroxypropylene group, or two or more of a sulfide bond in the molecule, and not containing a basic nitrogen atom. Compared to baths containing aliphatic monosulfide compounds, such as thiodiglycol or beta-thiodiglycol, which do not contain an ether oxygen atom, 1-hydroxypropyl group, a hydroxypropylene group, or two or more of a sulfide bond in the molecule, by having these particular compounds, the plating bath of the present invention has excellent stability over extended time, excellent co-deposition of silver and various metals, and excellent appearance of the electrodeposition coating.

Dependencies are inferred from the claim text.