PURPOSE:To obtain an electroplating soln. giving a Pd-Ni-P alloy plating film contg. relieved stress, free from cracks and having satisfactory corrosion resistance by specifying the compsn. of an aq. soln. so that P is codeposited in a Pd-Ni alloy plating film. CONSTITUTION:This plating soln. is an aq. soln. contg. 0.01-0.5mol/l Pd compd., 0.01-1mol/l Ni compd., 0.02-1mol/l amine compd. and 0.001-0.5mol/l one or more kinds of P-contg. compds. selected among phosphorous acid and hypophosphorous acid compds. In the case of 0.01mol/l Pd compd., current efficiency is reduced and 0.5mol/l Pd compd. deteriorates the stability of the soln. without further increasing current efficiency. In the case of 0.01mol/l Ni compd., Ni codeposits hardly and 1mol/l Ni compd. deteriorates the stability of the soln. The amine compd. contributes toward stabilizing the soln. but 1mol/l amine compd. is uneconomical and 0.02mol/l amine compd. does not ensure stability. In the case of 0.001mol/l P-contg. compds., P codeposits hardly and 0.5mol/l P-contg. compds. deteriorate the appearance of a plating film.
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