| abstract |
An aqueous acidic plating bath for electrodeposition of tin, lead or tin-lead alloys on a substrate is described. The plating baths are free of fluoborate and comprise (a) at least one bath-soluble metal salt selected from the group consisting of a stannous salt, a lead salt, or a mixture of stannous and lead salts, (b) at least one alkane sulfonic acid or alkanolsulfonic acid, (c) at least one nonionic, cationic or amphoteric surfactant, (d) an effective amount of at least one primary brightening agent selected from the group consisting of aromatic aldehydes, acetophenones, and carbonyl compounds having the general formula Ar-C(H)=C(H)-C(O)-CH3 (III) wherein Ar is a phenyl, naphthyl, pyridyl, thiophenyl or furyl group, and (e) an effective amount of a secondary brightening agent selected from the group consisting of lower aliphatic aldehydes and substituted olefins of the formula <IMAGE> (IV) wherein R1 is a carboxy, carboxamide, alkali metal carboxylate, ammonium carboxylate, amine carboxylate or allyl carboxylate, and R2, R3 an R4 are each independently hydrogen or lower alkyl groups. Methods for the electrodeposition of tin, lead, or tin-lead alloys from such baths also are described. |