Improved Flexible Printed Circuit and Method for the Preparation Thereof

1,156,606. Laminates. DOW CHEMICAL CO. 4 May, 1967 [23 May, 1966], No. 20864/67. Heading B5N. [Also in Division H1] A process for the preparation of a printed circuit 10 comprises providing a conductive layer 12, 13 e.g. of copper foil having the configuration necessary for the intended circuit, providing on at least one surface of the said conductive layer e.g. by extrusion a layer 28, 29 of a resinous copolymer of ethylene and an acid comonomer, the acid comonomer consisting of an olefinically unsaturated mono- or polycarboxylic acid, an anhydride of one of such acids having from 3 to 8 carbon atoms per molecule or a partial ester of one of said polycarboxylic acids with an alcohol having from 1 to 20 carbon atoms, and providing on the external surface of said copolymer layer or, if there are two copolymer layers, on the surface of each such layer, a layer 20, 32 of an oriented linear polyester film, oriented nylon film, oriented polyvinyl fluoride film or oriented polypropylene film, the acid content of at least those parts of the copolymer layer or layers which are adjacent the conductive layer or adjacent a layer of oriented film being from 2% to 25% by weight of the total weight of such copolymer layer. Specified comonomers are acrylic methacrylic, crotonic, furmaric, maleic and itaconic acid, maleic anhydride, monomethyl maleate, monoethyl maleate, monomethyl fumarate and monoethyl fumarate. Bonding of the layers is preferably effected at elevated temperature, the oriented film being electrostatically treated or subjected to corona discharge and the metallic layer treated with polyethylene imine prior to bonding.