Patent GB-1481183-A (GB)
Title: Method of manufacturing metal patterns
IPC: G03C5/56
Filed: 1974-11-22
Abstract: 1481183 Photographic processes PHILIPS GLOEILAMPENFABRIEKEN NV 22 Nov 1974 [26 Nov 1973] 50736/74 Heading G2C The invention provides a method of manufacturing an external, electrically conducting metal pattern on a layer which is at least superficially non-conducting and itself serves as a support for the pattern or is self-secured to a substrate, in which layer an organic photo-sensitive compound is homogeneously dispersed in a hydrophobic organic binder, the photo-sensitive compound forming a light-reaction product on exposure to light, said light-reaction product being capable of separating metal from solutions of the relevant metal salts in the form of a physically developable or electrolessly intensifiable image of metal nuclei, said photo-sensitive compound being soluble in one or more organic solvents in which the hydrophobic organic binder is soluble or can swell, the method comprising the steps of exposing the layer containing the organic photo-sensitive compound to light in accordance witht he pattern so as to form the light-reaction product, treating the layer containing the light-reaction product with a solution of a relevant metal salt so as to form a physically developable or electrolessly intensifiable image of metal nuclei, and then physically developing or electrolessly intensifying the image of metal nuclei to form the metal pattern, wherein at least one of the treating liquids used to convert the lightreaction product into the ultimate metal pattern comprises as a solvent a mixture of one or more water-miscible organic solvents and water in a volume ratio of the total water-miscible organic solvents to water of between 1:10 and 2:1, said mixture being capable of causing the hydrophobic organic binder to swell so that the adhesion of the metal pattern to the layer is thereby enhanced. The layer containing the organic photo-sensitive compound may be made by wetting a non-conductive layer comprising the hydrophobic organic binder with a solution containing the photosensitive compound and the binder and drying the layer. Diazosulphides are suitable photo-sensitive materials. After exposure solutions of the metal salts in water comprising, where the binder is polyester or epoxy resin, ethyl acetate, aliphatic alcohols or ketones are applied. The nuclei formed are then physically developed and the image can be intensified by electro-plating. In an example (1) to a polyethylene terephthalate support there is applied a composition of polyester is trichlorethane, aluminium silicate, silica, diphenylmethane diisocyanate hardener, dichloromethane, and 4-nitrobenzenediazo-t-butyl sulphide after drying, exposure to a printed circuit pattern is effected and then a nuclei forming water/isopropanol/ ethyl acetate solution of mercurous and silver is applied. After rinsing in the same solvent development is carried out with a stabilized physical developer solution comprising ferrous ammonium sulphate, ferric nitrate, citric acid, silver nitrate and surface active agents. After drying the pattern is thickened with copper by electro-plating. The silver image may be exchanged for palladium before intensifying with copper, Ex. 7. In ex 9 the same photo-sensitive material is diffused into the surface of glass-fibre reinforced epoxy resin for similar exposure and development. In other examples (10) the binder comprises epoxybutadieneacrylonitrile in MEK to which polyamine hardener is added; (11) the sodium salt of diethoxybenzenediazosulphonic acid is the sensitive compound, (12) erythrosine blue is used as sensitizer; (13) 3,5-dichloro-4-dimethylaminobenzene diazo t-butyl sulphide is the sensitive compound. A bleaching step is effected followed by redevelopment.