Tin or tin alloy electroplating bath, and electronic component having electrodeposit formed thereon using the plating bath

1. A tin or tin alloy electroplating bath, comprising:

(A) a soluble salt of a stannous salt or a mixture of a stannous salt and a salt of at least one metal selected from the group consisting of zinc, nickel, bismuth, cobalt, indium, antimony, gold, silver, copper and lead;

(B) an acid or a salt thereof;

(C) at least one branched polyoxyalkylene compound selected from the group consisting of the following compounds (C3), (C4) and (C5):

(C3) an alkylene oxide adduct of trimethylolalkane or triethylolalkane in which oxyalkylene chains are respectively bonded to a plurality of oxygen atoms of an alcohol structure in a molecule;

(C4) an alkylene oxide adduct of glycerin in which oxyalkylene chains are respectively bonded to a plurality of oxygen atoms of an alcohol structure in a molecule; and

(C5) an alkylene oxide adduct of polyglycerin in which oxyalkylene chains are respectively bonded to a plurality of oxygen atoms of an alcohol structure in a molecule; and

(D) at least one complexing agent selected from

(i) a sulfide compound selected from the following compound (a), compound (b) and compound (c);

(ii) a heterocyclic sulfur-containing compound corresponding to the following compound (d); and

(iii) salts thereof:

(a) an aliphatic sulfide compound represented by the following formula (a): X n —R 1 —S—(CH 2 CH 2 S) m —R 2 —X n (a)

in which R 1 and R 2 are C2-C4 alkylene; X is selected from NR a R b in which R a and R b are C1-C6 alkyl, and CONR a R b in which R a and R b are hydrogen or C1-C6 alkyl, and may be bonded to any carbon atom in an alkylene chain included in R 1 and R 2 ; m is 2; and n is an integer of 1 to 4;

(b) an aliphatic sulfide compound represented by the following formula (b): H—(OA) n -S—(OA) n -H (b)

in which A is ethylene or propylene with a hydroxyl group optionally bonded to a carbon atom included in an ethylene or propylene chain; and n is an integer of 1 to 25;

(c) an aromatic sulfide compound having one or repeated mono-, di- or trisulfide bond, and having one or more basic nitrogen atoms in at least one of atom groups disposed on both sides of the bond and selected from aliphatic, alicyclic, aromatic ring and heterocyclic atoms; and

(d) a heterocyclic sulfur-containing compound that has a monocyclic heterocyclic group or a fused heterocyclic group containing 1 to 5 atoms of at least one selected from nitrogen, sulfur and oxygen, excluding pyridine, morpholine, benzimidazole, benzothiazole and benzoxazole ring groups, and the monocyclic heterocyclic group or the fused heterocyclic group being any one of heterocyclic groups selected from tetrazole, triazole, thiazole, thiadiazole, imidazole, quinoline, furan, morpholine, thiophene, pyridine, oxazole, oxadiazole, pyrrole, pyrazole, pyrazine, isothiazole, isoxazole, pyrazolidine, pyrimidine, pyridazine, pyrrolidine, indolizine, indole, isoindole, indazole, purine, isoquinoline, naphthyridine, quinoxaline, carbazole, phenanthroline, phenazine, phenothiazine, phenoxazine, phenanthridine, pyrroline, imidazolidine, pyrazoline, imidazoline, piperidine, piperazine, indoline and thianthrene, and that has a sulfide group or a mercapto group bonded adjacently to the heterocyclic group.

2. The tin or tin alloy electroplating bath according to claim 1 , wherein regarding the branched polyoxyalkylene compound (C),

the compound (C3) is trimethylolpropane tripolyoxyethylene ether,

the compound (C4) is polyoxypropylene glycerol ether, and

the compound (C5) is polyoxypropylene polyglyceryl ether.

3. The tin or tin alloy electroplating bath according to claim 1 , further comprising at least one additive selected from a surfactant, an antioxidant, a brightening agent, a semi-brightening agent, a pH adjusting agent and an antifoaming agent.

4. The tin or tin alloy electroplating bath according to claim 1 , wherein the at least one complexing agent is the aliphatic sulfide compound (a).