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Technique for Etching the Base Chromium Metallized Layer On Substrates

IP.com Disclosure Number: IPCOM000037807D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-30
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Betteridge, BL: AUTHOR [+3]

Abstract

Before a ceramic substrate can have an electrical circuit formed on its surface, the surface must be "metallized", and this has been accomplished by applying a coating of chromium-copper- chromium. However, after the electrical circuit has been formed, this coating must be removed between the electrical lines on the ceramic substrate. While the top chromium layer and the intermediate copper layer can be removed readily using sulfuric acid/thiourea etcher, this etcher will not remove the base chromium layer from the ceramic substrate.

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Technique for Etching the Base Chromium Metallized Layer On Substrates

Before a ceramic substrate can have an electrical circuit formed on its surface, the surface must be "metallized", and this has been accomplished by applying a coating of chromium-copper- chromium. However, after the electrical circuit has been formed, this coating must be removed between the electrical lines on the ceramic substrate. While the top chromium layer and the intermediate copper layer can be removed readily using sulfuric acid/thiourea etcher, this etcher will not remove the base chromium layer from the ceramic substrate.

On a substrate that has been metallized with chromium- copper-chromium- polyimide, it is not possible to etch the top layer of chromium due to the smoother surface topography. The present technique has been discovered to be extremely effective in etching base chromium layers on ceramics as well as smooth chromium surfaces using the sulfuric acid/thiourea etcher.

According to this technique, a chromium layer is "doped" with copper, which, it has been discovered, seems to initiate a galvanic etching of the chromium. By this technique, it is possible to etch both top and bottom chromium on both a porous and a non-porous surface.

Disclosed anonymously.

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