Tin-silver alloy electroplating bath and tin-silver alloy electroplating process

摘要

Disclosed is a tin-silver alloy electroplating bath containing: (A) stannous sa (B) silver sa (C) one kind or two or more kinds of acids selected from the group consisting of sulfuric acid, phosphoric acid, phosphonic acid, hydroxycarboxylic acid, alkanesulfonic acid, and alkanolsulfonic acid; (D) thiourea; (E) nonionic surface active agent; and (F) one kind or two or more kinds of additives selected from the group consisting of a mercapto group containing aromatic compound, dioxyaromatic compound, and unsaturated carboxylic acid. The electroplating using the above electroplating bath is allowed to form a homogeneous tin-silver alloy plated film having a good external appearance by eliminating preferential deposition of silver and substitutional deposition of silver on an anode and the plated film.