Patent ID: 6458514
Filing Date: 2002-10-01
Classification: H05K,Y10S

Abstract:
A process for forming one or more through holes in a printed circuit board (PCB) substrate formed of a resinous dielectric sheet and a conductive layer covering a first surface of the dielectric sheet, said process comprising the steps of:(a) forming by laser one or more annular cavities on a second surface of the PCB substrate such that the cavities penetrate only the dielectric sheet; (b) coating the first surface and the second surface of the substrate with a liquid photoresist layer such that the cavities are filled with the liquid photoresist; (c) forming by photolithography one or more small areas on the first surface covered by the conductive layer such that the small areas correspond in location and shape to the cavities; (d) removing by etching the conductive layer covering the small areas formed in the step (c); and (e) stripping the cavities of the photoresist to form through holes in the small areas which are defined by the cavities.