Improvements in plating conducting areas on insulating surfaces

摘要

In order to electroplate or galvanically plate isolated conductive areas 3 of a printed circuit formed by photo-etching a copper-clad phenolformaldehyde laminate 1, the areas 3 are interconnected by electroless deposition. After the plating step, the bridges are removed using a solvent for the resist. Alternatively, the areas to be made conductive and the resist bridges are simultaneously first electroless-coated, then plated. In an example, the bridges are formed of shellac in butyl alcohol with glycerol, a catalyst for the electroless step, comprising palladium chloride dissolved in conc. HCl, being added. Nickel is electroless-deposited in a bath comprising Nickel acetate (21 g/l), Sodium hypophosphite (24 g/l), Sodium lactate (20 g/l), acetic acid (10 ml/l); then a layer of gold may be added in an electroless-plating bath comprising Ammonium chloride (75 g/l), Sodium nitrate (50 g/l), Sodium hypophosphite (10 g/l), Potassium gold cyanide (2 g/l). The conductive areas and bridges are then electroplated with gold, after which the plated shellac bridges are removed by rubbing or brushing with methylated spirit. In another example, the bridges are formed from gum sandarac dissolved in methylated spirit, the palladium chloride catalyst solution being painted on subsequently. Ethyl alcohol is used to remove the bridges. Other resist gums mentioned include copal and kauri, and cobalt may replace nickel in the first electroless-plating step.