コバルトの無電解メッキにおける析出速度について

Abstract

The relation between the precipitation velocity and the composition of bath was studied on acidic or alkaline electroless baths consisting of cobalt sulfate and sodium hyposulfite, including buffers and additives. As the results of experiments, it was shown that all acidic baths containing organic acids were not in practical use because of so small precipitation velocity as lower than 1μ/h, while caustic or ammonical alkaline baths containing citrate or tartrate gave a considerable velocity as high as 10-15μ/h at 90±1°C.The precipitation velocity was remarkably increased by the addition of boric acid (0.5mol) into caustic alkaline baths, and the surface state of deposits was improved by the addition of ammonium sulfate (0.6mol) into ammoniacal alkaline bath.The optimum composition of bath for practical use was as follows:(1) Caustic alkaline citrate bath (pH=7-8-NaOH); 0.1mol CoSO4, 0.2mol NaH2PO2, 0.2mol Na-citrate, and 0.5mol boric acid.(2) Caustic alkaline tartrate bath (pH=9-NaOH); 0.08mol CoSO4, 0.2mol NaH2PO2, 0.5mol Na-tartrate, and 0.5mol boric acid.(3) Ammoniacal alkaline citrate bath (pH=9-10-NaOH); 0.07mol CoSO4, 0.2mol NaH2PO2, 0.2mol Na-citrate, and 0.6mol (NH4)2SO4.(4) Ammoniacal alkaline tartrate bath (pH=9-10-NaOH); 0.08mol CoSO4, 0.2mol NaH2PO2, 0.5mol Na-tartrate, and 0.6mol (NH4)2SO4.