The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 03, 1985
Filed:
Apr. 13, 1984
Johann Greschner, Pliezhausen, DE;
Friedrich W Schwerdt, Herrenberg, DE;
Hans J Trumpp, Stuttgart, DE;
International Business Machines Corporation, Armonk, NY (US);
Abstract
A process for producing printed circuit boards having metallic conductor structures embedded in the insulating substrate and whose front and back sides are conductively connected by means of plated through holes. The first steps of the process comprise producing a matrix on an epoxy resin substrate consisting of a lift-off layer, an aluminum barrier layer and a positive photoresist layer. A negative image of the desired conductor pattern is then generated in the photoresist layer using conventional photolithographic techniques. The negative image is etched into the barrier layer and the lift-off layer such that an undercut occurs under the barrier layer. Subsequently, vertical trenches are etched into the epoxy resin substrate. After drilling of the through holes, an activating layer of copper is deposited by means of magnetic field enhanced cathode sputtering on the surfaces of the trenches, the through holes and the barrier layer. The lift-off layer, together with the barrier layer covering it, is removed by immersion in a suitable solvent, and copper conductors are subsequently grown in the etched conductor trenches.