1,195,217. Coating with copper. TECHNOGRAPH Ltd. Sept.25, 1968 [Oct. 4, 1967], No.45117/67. Heading C7F. An electroless copper plating bath, which does not contain a cuprous ion complexing agent, comprises 0À002 to 0À15 mol. per litre of a water soluble copper salt, e.g. sulphate, nitrate, gluconate, pyrophosphate formate or acetate, 0À5 to 4À5 ml. per litre of 40% aqueous formaldehyde, 0À5 to 2À5 times the mols of copper per litre of a cupric ion complexing agent and an alkali metal hydroxide to bring the PH to 10À5 to 14. The complexing agent may be E.D.T.A., hydroxyethyl E.D.T.A., Rochelle salt, cream of tartar, triethanolamine, sugars, mannitol, sorbitol, ethylene glycol and gluconic acid. The solution may also include an additional reducing agent e.g. sodium sulphate, non-ionic, anionic, and cationic wetting agents, e.g. sodium lauryl sulphate, and a stabilizer e.g. sodium orthophosphate. The bath temperature is preferably 35 to 65‹C. An insulating panel to be plated may be first sensitized and seeded using stannous chloride followed by Pd, Pt, Au, Rh, Os or Ir chlorides. The coating may be subsequently electro-plated with Cu.
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