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Process for Making Through Holes

IP.com Disclosure Number: IPCOM000081597D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Cutillo, JG: AUTHOR [+2]

Abstract

Through holes having straight walls with negligible undercut are achieved in epoxy glass substrates.

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Process for Making Through Holes

Through holes having straight walls with negligible undercut are achieved in epoxy glass substrates.

Using copper as an etch mask, the copper is etched chemically for a period of time corresponding to about 50% of that required to effect complete etch through, in order to initiate the hole. This is followed by an abrasive spray to complete the hole.

For example, in a substrate 3.75 mils thick of epoxy glass having both sides clad with 1 oz of copper, 6 mil holes were etched in the copper at both sides of the desired interstitial hole using an etching bath comprising, by weight, approximately 90% concentrated sulfuric acid and 10% ammonium bifluoride. Etching is achieved by immersion of the copper-clad substrate for about two minutes in the above bath, while the bath is being agitated. After etching, the substrate is rinsed and dried and subjected to an air abrasive spray employing 50 micron silicon carbide as the abrasive.

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