コバルト-ニッケル合金の無電解メッキ浴-カセイアルカリクエン酸浴-

Abstract

The relation between the plating conditions and the rate of deposition or the composition of plated film on electroless plating bath for cobalt-nickel alloy of sulfate-hypophosphite system was investigated. The results obtained were as follows.1) The following 3 kinds of baths were selected for stable plating baths having relatively high rate of deposition.a) Caustic alkaline citrate bath (C-C)b) Ammoniacal alkaline citrate bath (A-C)c) Ammoniacal alkaline tartrate bath (A-T)2) The preferable conditions for plating bath of C-C type were as follows: CoSO4+NiSO4 0.1 mol/l, Na-citrate 0.2mol/l, H3BO3 0.5mol/l, pH=7(NaOH), and operating temperature 90°C.Under the above conditions, a desired film composition containing phosphorus with any ratio of nickel to cobalt was obtained by controlling the ratio of concentrations of nickel to cobalt in the bath.3) The phosphorus content in the alloy film decreased almost linearly from 14% (in nickel film) to 4% (in cobalt film) with the increase of cobalt content in the film.4) The sum of the rate of deposition in each single bath was almost equal to the rate of the alloy plating bath; however, the ratio of nickel to cobalt in the alloy film did not correspond well with the rate of deposition in each single bath, but a higher content of cobalt than the value calculated from its rate of deposition was always given.