GB1425732A - Methods of manufacturing printed circuits and a printed circuit produced by such method - Google Patents

Abstract

1425732 Printed circuits THOMSON-CSF 7 May 1973 [10 May 1972] 21731/73 Heading H1R In a method of making a printed circuit having conductors on both sides of a support interconnected through eyelet holes, a first metal, e.g. copper, readily soluble in chemical reagents, is deposited, e.g. electrolytically on a metal substrate except where studs of a photoresist mask occupy the location of eventual eyelet holes, the mask is dissolved and the substrate removed, a pattern of conductors 6, 7, 8, 10 interconnected through the holes 9 is deposited on both sides of the first metal layer 3 (Fig. 8) using masking techniques, the conductor metal being resistant to reagents dissolving the first metal, e.g. gold, and the first metal is dissolved away and replaced by insulating material. To permit handling of the assembly, not all of the first metal is removed at once, and to this end, the first metal layer bearing the conductive pattern is located on a rigid insulating base 50 (Fig. 9), studs 12 of insulating material are deposited at regions where the conductors cross so as to cover adjacent surface portions of layer 3 but leaving the major portion 14 of layer 3 uncovered, the metal of layer 3 is dissolved away, replaced by insulating material, the studs 12 removed, then the remaining metal of layer 3 under the studs removed and replaced by insulating material. The process may be adapted for making multilayer assemblies (Figs. 13 to 17, not shown).