| 摘要 |
PROBLEM TO BE SOLVED: To swiftly and securely execute solder joining even in the case of solder contg. no lead by coating the surface of parts with a tin-copper alloy plating film obtd. from a noncyanic plating bath having gloss or semi-gloss. SOLUTION: The surface of circuit parts is coated with a tin-copper alloy plating film obtd. from a noncyanic tin-copper alloy electroplating bath and having gloss or semi-gloss. Prior to this treatment, lower layer plating of nickel or a nickel alloy is preferably applied by electroplating or electroless plating. Moreover the surface of the tin-copper alloy plating is furthermore applied with plating of one or >= two kinds of metals selected from gold, silver, palladium, bismuth, antimony, indium and alloys essentially consisting of them by electroplating or electroless plating to form into upper layer plating. The concn. of the metal in the plating bath is suitably controlled to 1 to 100 g/l. Moreover, a surfactant may be added to the plating bath.
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