Method of making plated hole printed wiring boards

Claim 1

THE PROCESS OF FORMING ELECTRICALLY CONDUCTIVE METAL PORTIONS EXTENDING OVER SURFACES AND THROUGH HOLES IN AN INSULATION BACKING COMPRISING THE STEPS OF APPLYING A PLATING RESIST OVER THE MEATL SURFACES OF A SHEET OF FOIL CLAD INSULATION SO AS TO COVERALL THE SURFACES EXCEPT THOSE FORMING A CONDUCTIVE PATHWAY PATTERN, COVERING THE PLATING RESIST AND THE EXPOSED METAL SURFACES WITH A STRIPPABLE FILM, FORMING HOLES THROUGH SAID FOIL CLAD INSULATION AND SAID FILM IN SUCH A WAY THAT THE ENDS OF THE HOLES ARE SURROUNDED BY FOIL WHICH IS NOT COVERED BY SAID PLATING RESIST, APPLYING A CONDUCTIVE COATING NOT SUBJECT TO MIGRATION TO THE WALLS OF SAID HOLES, REMOVING SAID STRIPPABLE FILM, PLATING A FIRST METAL OVER SAID CONDUCTIVE COATING AND THE SURFACES OF SAID FOIL NOT COVERED BY SAID RESIST, SAID METAL HAVING THE PROPERTIES OF HIGH ELECTRICAL AND THERMAL CONDUCTIVITY AND RESISTANCE TO STRESS, PLATING A SOLDER TYPE METAL OVER SAID FIRST METAL, REMOVING SAID PLATING RESIST, AND REMOVING BY CHEMICAL ACTION ATTACKING SAID FOIL BUT NOT SAID SOLDER TYPE METAL ALL PARTS OF SAID FOIL THAT HAD BEEN COVERED BY SAID PLATING RESIST.