| 摘要 |
PROBLEM TO BE SOLVED: To suppress the decomposition of a thio compd. to be added as a color developing agent caused by anodic oxidation in the process of electrolysis by allowing the soln. to contain ruthenium sulfate, sulfamic acid, a thio compd. and a sacrificial oxidizer added for preventing the decomposition of the thio compd. caused by anodic oxidation in the process of electrolysis. SOLUTION: Preferably, the sacrificial oxidizer is selected from hydroxylamine sulfate, formalin and ascorbic acid, and the thio compd. is selected from thiourea, a thiourea derivative, a compd. having a marcapto group, thiomalic acid and ammonium thiocyanate. The concn. of ruthenium is desirable controlled to 1 to 10 g/L considering the current efficiency, plating time and the loss of ruthenium caused, e.g. by the cleaning of electrodeposite in the process of the treatment. The concn. of the thio compd. is preferably controlled to 0.1-10.0 g/L. In the black ruthenium plating soln., pH is preferably controlled to <2, current density to 5-15 A/dm2, and soln. temp. to >=40 deg.C.
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