抄録
The plated films of electroless Cobalt deposited from the following 4 kinds of baths were examined macroscopically, microscopically, and by roughness tester; and the effects of fundamental conditions of the bath on the properties of films were investigated.
(1) CoSO4 0.07mol/l, NaH2PO2 0.2mol/l, Na-Citrate 0.2mol/l, (NH4)2SO4 0.6mol/l, pH=9-10 (A-C Type bath)
(2) CoSO4 0.08mol/l, NaH2PO2 0.2mol/l, Na-Tartrate 0.5mol/l, (NH4)2SO4 0.6mol/l, pH=9-10 (A-T Type bath)
(3) CoSO4 0.05mol/l, NaH2PO2 0.2mol/l, Na-Citrate 0.2mol/l, H3BO3 0.5mol/l, pH=7-8 (C-C Type bath)
(4) CoSO4 0.05mol/l, NaH2PO2 0.2mol/l, Na-Tartrate 0.5mol/l, H3BO3 0.5mol/l, pH=9 (C-T Type bath)
The appearance of the deposit depended on the kinds and concentrations of complexing agents in the bath. Namely, types of the baths were arranged in descending order of the brightness of plated films as follows:
A-C>C-C>A-T>C-T
When the plating was carried out in the bath of the same composition, the film obtained had less bright appearance as the rate of deposition was greater.
The surface state of the plated film was worse as the film was more thick, in particular, the tendency was remarkable in the baths of tartrate type.
Ammonium sulfate present in ammoniacal alkaline baths improved the surface state of plated films. The optimum concentration of ammonium sulfate was 0.6mol/l. Though thiourea was an effective brightener for these baths, its optimum amount of addition depended on the type and pH of plating baths.
