GB774424A - Electrodeposition of copper - Google Patents

Abstract

774,424. Electrodeposition of copper. METAL & THERMIT CORPORATION. Oct. 11, 1954 [Oct. 14, 1953], No. 29285/54. Class 41. An aqueous pyrophosphate copper electroplating bath is characterized by the addition thereto of 2-mercaptobenzimidazole or its substituted- or unsubstituted-alkyl or -amino derivatives. Preferably the bath contains per litre 7.5 to 45 grams of bivalent copper, pyrophosphate in an amount ranging from that necessary to convert the copper to the complex radical Cu(P 2 O 7 ) 2 <SP>6E</SP> to that which saturates the solution, 5 to 20 grams of nitrate radical, 1 to 3 grams of ammonia, and 0.0005 to 0.5 gram of 2-mercaptobenzimidazole or its substituted or unsubstituted amino derivatives, together with 15 to 30 grams of oxalate radical, either as the acid or its alkali metal or ammonium salt, and plating is effected with a cathode current density of 2 to 75 amps/sq. ft. with the bath at 70‹ to 160‹ F. and pH 7.5 to 9.5. The copper may be added as copper pyrophosphate, sulphate, or acetate; the pyrophosphate may be added as any of the sodium or potassium salts; the nitric may be added as nitric acid or sodium or potassium nitrate ; and the ammonia may be supplied as a gas or in aqueous solution. Suitable derivatives of 2-mercaptobenzimidazole are those having one or more groups such as 4- butyl, 4- or 5-amino, substituted amino radicals such as sulphanilamido p-toluene sulphanilamido and acylamido in which the acyl group has up to 10 carbon atoms, and alkylol and carboxyalkyl radicals having up to 6 carbon atoms, e.g. 6-sulphanilamido, 5-propionamido, 4-amino 7-acetamido, N: N-dihydroxymethyl, 5 - carboxymethyl. Instead of the oxalate radical, 5 to 15 grams of citrate, 5 to 20 grams of tartrate, or carbonate radicals may be used. Thick level platings, e.g. more than “ inch thick, may be produced. Specifications 509,650 and 597,407 are referred to.