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Polyvinyl Alcohol as a Protective Banking Agent in Chemical Machining Processes

IP.com Disclosure Number: IPCOM000078547D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Beach, BL: AUTHOR [+4]

Abstract

In a normal photochemical machining process, a resist is applied and the unprotected areas are chemically etched to a predetermined depth. This depth is restricted by the product tolerances and the etch factor of the metal. The present process allows etching to a greater depth in the metal by eliminating undercutting of the resist image.

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Polyvinyl Alcohol as a Protective Banking Agent in Chemical Machining Processes

In a normal photochemical machining process, a resist is applied and the unprotected areas are chemically etched to a predetermined depth. This depth is restricted by the product tolerances and the etch factor of the metal. The present process allows etching to a greater depth in the metal by eliminating undercutting of the resist image.

The present process covers the application of an unsensitized film of polyvinyl alcohol from a water solution, to protect the sides of the initial resist image during secondary deep etching.

Steps in the process are as follows:
1) Application of the polyvinyl alcohol film.

a. Normally applied by dipping in a water-based

solution of polyvinyl alcohol; however, the

film may be applied by whirling, spraying, etc.
2) Dry the film in place.

a. Any suitable standard drying technique can be used;

for example, infrared lamps or electrically heated

circulated air.
3) Develop - Chemically insolublize.

a. Immerse in chromic acid solution. Chemical

reactions taking place in this step involve

dissolving, oxidizing, and dehydrating of the

polyvinyl alcohol film.
4) Rinse

a. Immerse in running water.
5) Bake - Optional depending on the degree of protection

desired and the depth of secondary etching.

a. Heat the panel at 250-270 degrees F for 2-3 minutes.

As shown above, the polyvinyl alcohol solution dries on the partially etched panel surface by concentrating aroun...