Abstract
The relation between the plating rate and the bath conditions were studied on electroless cobalt plating baths containing hydrazine as a reducing agent, and the properties of the deposited film were investigated in comparison with those from the baths containing hypophosphite.The following results were obtained.1. Caustic alkaline tartrate bath was selected for a suitable bath having a relatively large plating rate and a good stability, and its optimum conditions were as follows:CoCl2 0.05-0.08mol/l Thiourea 2-4ppmN2H4⋅2HCl 1.0mol/l pH 12.0(NaOH)Na-tartrate 0.4mol/l Bath temperature 90°C2. The appearance of the deposit was bright when the thickness of the film was less than about 2μ, but it changed to be dull when the film was thicker. The surface state became more deteriorated with the increase of film thickness.3. It was found that the deposit consisted of α-cobalt polycrystals, being the same as the deposit from hypophosphite baths. However, the grain size of the present deposit was in the range of 200-400Å which was larger than that from hypophosphite baths (100-200Å).4. It was also found that the deposit was a ferromagnetic substance having coercive force (Hc) of about 100oe., maximum magnetic flux density (Bs) of 11, 000-13, 000 gauss, and squareness (Br/Bs) of 0.4.
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