GB979779A - Method of making printed circuits - Google Patents

Abstract

Printed circuits are prepared by providing an insulating base with at least one surface having incorporated therein or thereon finely divided particles of cuprous oxide, curing the adhesive resinous bonding agent used in conjunction with said particles so that they adhere firmly to the base, exposing those particles which correspond with the desired circuit pattern to an acid to reduce at least some of the cuprous oxide to copper, and depositing metal, e.g. copper or nickel from a currentless metal deposition bath on to the copper particles. The circuit may be further built up by depositing more metal electrolytically on it. The insulating base may be of resinous material with incorporated copper oxide particles, or with a layer of resin containing copper oxide particles formed on one if its surfaces. Alternatively copper oxide particles can be applied to the uncured surface of a tacky resin which is then cured, or an adhesive ink containing copper oxide particles may be printed on to the resinous base and cured. When the surface is completely covered with copper oxide particles it is printed with a resist ink and the whole surface is then treated with sulphuric acid to reduce exposed copper oxide to copper. If the proportion of copper oxide particles in the surface is low, it may be necessary lightly to abrade the surface before the acid treatment. Other acids which may be used are acetic, phosphoric and hydrofluoric. In Example 1. A base is moulded from a mixture of epoxy resin, "Ciba 502" (Registered Trade Mark), copper oxide particles and diethylene triimine. One surface is covered with a resist, portions of which are then removed to expose copper oxide, and sulphuric acid is applied for 5-15 minutes. The base is rinsed and copper or nickel deposited in known manner. Copper may subsequently be electrolytically deposited (2). A coating of epoxy resin-cuprous oxide-hardener mixture is applied to a urea-formaldehyde resin support and cured thereon (3). An organosol composition of vinyl chloride-vinyl acetate copolymer, dioctyl phthalate and methyl ethyl ketone is placed in a mould and while still tacky is dusted with cuprous oxide particles and curing is completed. The surface is printed with a resist to leave the circuit pattern expose before treatment as in (1), (4). An ink containing phenol formaldehyde resin, polyvinyl butyral resin, ethanol, cuprous oxide, powdered silica and methyl ethyl ketone is printed on to a polymethyl methacrylate base and the circuit formed as in (1), (5). The ink used contains butadiene-acrylonitrile copolymer, phenolformaldehyde resin, zirconium silicate, silica, cuprous oxide, isophorone and xylene. It is printed on to an epoxy-glass laminate and cured (6). A composition containing epoxy resin, cuprous oxide, polyamide resin, zirconium silicate and silica was moulded and a circuit formed thereon as in example (1). Specification 938,365 is referred to.ALSO:Printed circuits are prepared by providing an insulating base with at least one surface having incorporated therein or thereon finely divided particles of cuprous oxide, curing the adhesive resinous bonding agent used in conjunction with said particles so that they adhere firmly to the base, exposing those particles which correspond with the desired circuit pattern to an acid, to reduce at least some of the cuprous oxide to copper, and depositing metal, e.g. copper or nickel, from a currentless metal deposition bath on to the copper particles. The circuit may be further built up by depositing more metal electrolytically on it. The insulating base may be of resinous material with incorporated copper oxide particles, or with a layer of resin containing copper oxide particles formed on one of its surfaces. Alternatively copper oxide particles can be applied to the uncured surface of a tacky resin which is then cured, or an adhesive ink containing copper oxide particles may be printed on to the resinous base and cured. When the surface is completely covered with copper oxide particles it is printed with a resist ink and the whole surface is then treated with sulphuric acid to reduce exposed copper oxide to copper. If the proportion of copper oxide particles in the surface is low, it may be necessary lightly to abrade the surface before the acid treatment. Other acids which may be used are acetic, phosphoric and hydrofluoric. In Example (1) a base is moulded from a mixture of epoxy resin ("Ciba 502", Registered Trade Mark), copper oxide particles and diethylene triamine. One surface is covered with a resist, portions of which are then removed to expose copper oxide, and sulphuric acid is applied for 5-15 minutes. The base is rinsed and copper or nickel deposited currentlessly in known manner. Copper may subsequently be electrolytically deposited. (2) A coating of epoxy resin-cuprous oxide-hardener mixture is applied to a ureaformaldehyde resin support and cured thereon. (3) An organosol composition of vinyl chloride-vinyl acetate copolymer, dioctylphthalate and methyl ethyl ketone is placed in a mould and while still tacky is dusted with cuprous oxide particles and curing is completed. The surface is printed with a resist to leave the circuit pattern exposed before treatment as in (1). (4) An ink containing phenol formaldehyde resin, polyvinyl butyral resin, ethanol, cuprous oxide, powdered silica and methyl ethyl ketone is printed on to a polymethyl methacrylate base and the circuit formed as in (1). (5) The ink used contains butadiene-acrylonitrile copolymer, phenol-formaldehyde resin, zirconium silicate, silica, cuprous oxide, isophorone and xylene. It is printed on to an epoxy-glass laminate and cured. (6) A composition containing epoxy resin, cuprous oxide, polyamide resin, zirconium silicate and silica was moulded and a circuit formed thereon as in Example (1). Specification 938,365 is referred to.