GB1199634A - Improvements relating to Acid Tin Electroplating Solutions - Google Patents

Abstract

1,199,634. Bright tin electro-plating. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Sept. 14, 1967 [Sept. 14, 1966], No.42001/67. Heading C7B. An aqueous acid tin electro-plating bath contains bivalent tin and fluoborate, sulphate and sulphonate or sulphate anions, a non-ionic surfactant, a brightener formed by an unsaturated organic compound containing an aldehyde or a ketone group, and at least one organic compound other than formaldehyde which is capable of reducing the hydrogen overvoltage at a tin cathode. Typically the brightener is a compound R 1 -C(R 2 )= C(R 3 )-C(R 4 )=O where R 1 , R 2 and R 4 represent hydrogen atoms, aromatic or heterocyclic groups which may be wholly or partly hydrogenated, or aliphatic groups which are unsubstituted or contain one or more non-ionizable substituents which are not reducible in the solution to ionizable forms, and R 3 is a hydrogen atom, an alkyl group or an esterified carboxyl group or R 1 and R 2 together with the attached carbon atom form a ring or R 1 and R 3 together with the two ethylenically bonded carbon atoms form a cycloaliphatic ring, but excludes compounds of the general formula in which one of R 1 and R 2 is hydrogen and the other is an aromatic group, a hydrogenated aromatic group or a heterocyclic group, R 3 is hydrogen, and R 4 is hydrogen or an alkyl, alkenyl or alkoxy group. Specified examples are dihydrotolylaldehyde, benzalacetone and furfural. The overvoltage reducing compound may be an acrylic or an α-alkyl or α-phenyl-acrylic acid, amide or ester, the amide group being unsubstituted or monosubstituted by an alkyl or phenyl group and the ester group being mono-substituted by an alkylated or non-alkylated amino group; or a saturated aliphatic dialdehyde which may also include a hydroxy group. Examples given of suitable overvoltage reducing compounds are acrylic and methacrylic acid and amide, glycidyl acrylate, propylene glycol diacrylate, dimethylaminoethyl methacrylate, glyoxal, glutaric or α-hydroxyadipic dialdehyde, and also N-vinylpyrollidone, N- vinylcarbazole, p-diethylaminobenzaldehyde, 2- vinyl-pyridine, tetrahydrofuran, vinyl acetate and allylglycidyl ether. The non-ionic surfactant is preferably an alkylphenol-ethylene oxide condensate A specified sulphonate anion is that derived from m-benzene disulphonic acid. Uniform bright deposits may be obtained on complex profile iron sheet at 20‹ C. using current densities of 0À5 to 5 amps/sq.dm. Specification 1,141,283 is referred to.