GB1134615A - Gold electroplating bath - Google Patents

Abstract

1,134,615. Electro-plating with gold or gold alloy. TECHNIC Inc. Feb.3, 1967 [Feb.10, 1966], No. 5358/67. Heading C7B. Gold or gold alloy is electro-deposited from an aqueous alkaline bath comprising (i) between 1 and 30 g/l of gold in the form of potassium and/or sodium gold sulphite; (ii) between 40 and 150 g/l of sodium and/or potassium sulphite; (iii) between 5 and 150 g/l of a soluble phosphate, sulphate, carbonate, acetate citrate or tartrate of an alkali metal or alkaline earth metal as a buffering and conducting salt; (iv) at least one additive selected (a) as a metal brightener from Cd, Ni, Co, Sn, In, Cu, Mn or V in an amount between 5 and 500 mg/l added as a soluble salt of said metal or as a soluble complex of said metal; (b) as a semi-metal brightener from As, Sb, Se or Te in an amount between 1 and 400 mg/l added as a soluble salt or a soluble complex of said semi-metal (c) as an alloying element from Cd, Pb, Zn, Fe, Ni, Co, Sn, In, Co, Mn or Sb, the element being present in an amount between 0À5 and 5 g/l when added in the form of a salt and in an amount between 0À5 and 10 g/l when added in the form of a complex; and (v) sufficient of an acid or alkali to adjust the pH to a value above 8. The conducting salt (iii) may be a polyphosphate such as a tetra (ortho) phosphate or a hexametaphosphate, an ethylenediamine di-or tetra-acetate or a bicarbonate: while the additive elements (iv) may be used empolying the salts of acid radicals sulphate, nitrate, chloride, bromide, borate, fluoborate sulphamate, acetate, oxalate, formate or another weak organic acid, or as alkali metal, ammonium, quaternary ammonium or other organic base salts including the additive element in the anion e.g. titanates, molybdates tungstates, vanadates, arsenites, antimonites, selenates tellurates; or as chelates of nitrilo-, imino-, and amino-polycarboxylic acids, acetylacetone, or hydroxy carboxylic acids such as citric, lactic, or tartaric acids. The use of potassium antimonyl tartrate is specified. The baths may be used at temperatures up to 180‹ F. with a pH of 12 or above but preferably 9 to 11 with C.D. of 1 to 50 amps/sq.ft. and preferably moderate bath agitation.