GB1337338A - Process for making printed circuit boards and products obtained by said process - Google Patents

Abstract

1337338 Printed circuit boards MACDERMID Inc 19 June 1971 28854/71 Heading H1R A process for providing improved adhesion between a metal layer and an insulating substrate is characterized by the fact that it comprises chemically stripping the whole of the metal foil layer, e.g. of Cu or Ni from a polymerized resin substrate, e.g. of thermosetting epoxy or phenolic resin by means of an etchant. The resulting non-conductive surface is then catalysed and plated with a metal in the configuration of the desired circuit. The substrate is heated at least once after the catalysing step, e.g. to 220‹ F. for about 30 mins. and preferably also after the plating step. The circuit may be deposited by several methods. In one, after the substrate has been catalysed, a thin Cu or Ni layer of about 10 to 30 Î 10<SP>-6</SP> inches thickness is deposited over the whole surface. A masking negative resist pattern of the circuit is applied over the metal layer, the substrate then being dried and baked. Additional metal is then applied by electroplating so as to build up the conducting areas of the circuit. A resist is then applied to the exposed metal, the resist from the non-circuit portion is stripped and the initial thin electroless deposit is etched away. The resist applied to the exposed metal is then stripped and a protective metal, e.g. of gold, silver or nickel, is electrolessly or electrolytically plated on the circuit. The board is then baked. In another method, a negative resist circuit pattern is applied after the catalysing step, the board is dried and baked, and the exposed circuit area is reactivated by means of a dilute acid solution. Metal is then electrolessly plated on the circuit area, the board is dried and baked, the resist stripped and the completed board baked. Catalysis in the above processes may be carried out by means of a tin-palladium hydrosol.