Method of producing printed circuits

Claim 1

THE PROCESS OF PRODUCING A PRINTED CIRCUIT WHICH COMPRISES THE STEPS OF STARTING WITH A SHEET OF METALLIC CONDUCTOR OF SUFFICIENT THICKNESS TO BE CAPABLE OF SELFSUPPORT, PHOTOGRAPHICALLY PRODUCING ON SAID SHEET AN IMAGE OF LANDS DESIRED, PARTLY ETCHING AWAY UNDESIRED CONDUCTOR LEAVING PROJECTING LANDS, APPLYING TO THE ETCHED SURFACE A LAYER OF INSULATING MATERIAL, REMOVING A PORTION OF SAID INSULATING MATERIAL DOWN TO THE LEVEL OF SAID LANDS SO AS TO EXPOSE SAID LANDS, PLATING ON A LAYER OF CONDUCTOR OVER AND IN CONTACT WITH SAID LANDS AND INSULATING MATERIAL, PHOTOGRAPHICALLY PRODUCING ON SAID LAYER AN IMAGE OF A FIRST CIRCUIT, ETCHING AWAY UNDESIRED CONDUCTOR FROM SAID LAST MENTIONED LAYER FORMING A CIRCUIT PATTERN INTERCONNECTED WITH SAID LANDS, AND ETCHING THE PREVIOUSLY UNETCHED SIDE OF SAID SHEET TO FORM ANOTHER CIRCUIT INTERCONNECTED AT SELECTED POINTS WITH SAID FIRST CIRCUIT.