Composition for tin-silver alloy electroplating comprising a complexing agent

Abstract

An aqueous composition comprising (a) metal ions comprising tin ions and silver ions and (b) at least one complexing agent of formula (C1) R—X—S—X[D-X—]—S—X—R, (C2) R—X—S—X-D-[X—S—]X—R, (C3) R—X—S—X-[D-X—]S—X—Rwherein X, Xare independently selected from a linear or branched C-Calkanediyl, which may be unsubstituted or substituted by OH; X, Xare independently selected from X, which may be further substituted by —X—COOR, —X—SO—O—R, a Cto Cpolyoxyalkylene group of formula —(O—CH—CHR)—OH, or a combination thereof, and —X—NH—CO—X—CO—NH—X—; X, Xare independently selected from a chemical bond and X; X, Xare independently selected from X; Xis a linear or branched Ci to C10 alkyl; Xis selected from Xand a divalent 5 or 6 membered aromatic group; R, Rare independently selected from a monovalent 5 or 6 membered aromatic N-heterocyclic group comprising one N atom or two N atoms which are separated by at least one C atom, and its derivatives received by N-alkylation with a C-C-alkyl group, which may be substituted by —COORor —SO—O—R, and which aromatic N-heterocyclic group may optionally further comprise, under the proviso that X21 is substituted by at least one OH, one S atom; R, Rare independently selected from a monovalent 5 or 6 membered aliphatic N-heterocyclic group comprising one N atom and one O atom; Dis independently selected from S, O and NR; Dis (a) a divalent 5 or 6 membered aliphatic heterocyclic ring system comprising 1 or 2 S atoms, or (b) a 5 or 6 membered aromatic heterocyclic ring system comprising at least two N atoms and optionally one or two S atoms; Dis independently selected from S and NR; n is an integer of from 0 to 5; z is an integer from 1 to 50; Ris selected from H and a linear or branched C-Calkyl; Ris selected from H and a linear or branched Cto Calkyl; and Ris selected from R10 and a cation.