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Etching Of Epoxy Glass Circuit Board

IP.com Disclosure Number: IPCOM000095450D
Original Publication Date: 1964-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Reed, LJ: AUTHOR

Abstract

This is for producing through-holes in epoxy glass printed circuit boards. In A, there is shown a section of a printed circuit board having copper sheets 4 and 6 which are bonded to an epoxy glass laminate 8. The epoxy glass is essentially a sheet of woven glass fibers 10 which are impregnated with an epoxy resin 12. As shown in both A and B, copper sheets 4 and 6 have been etched so as to expose circular areas 14 and 16.

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Etching Of Epoxy Glass Circuit Board

This is for producing through-holes in epoxy glass printed circuit boards. In A, there is shown a section of a printed circuit board having copper sheets 4 and 6 which are bonded to an epoxy glass laminate 8. The epoxy glass is essentially a sheet of woven glass fibers 10 which are impregnated with an epoxy resin 12. As shown in both A and B, copper sheets 4 and 6 have been etched so as to expose circular areas 14 and 16.

By applying hot concentrated sulphuric acid to exposed area 14, epoxy resin 12, which is located directly beneath area 14, is etched away. Copper sheet 4, which is impervious to the acid, protects the remainder of the board. Glass fibers 10 are sufficiently porous to allow the sulphuric acid to etch completely through to area 16. Since, however, the sulphuric acid has no affect upon the glass fibers 10, they remain within the etched-out area (C). To terminate the acid's etching effects, the board is washed and dipped in an alkaline neutralizer.

To then dissolve glass fibers 10 and produce the desired through-hole, a solution of hot sodium hydroxide is applied. If it is desired to make electrical connection between copper sheets 4 and 6, hole 20 can be plated with copper as in D.

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