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Bubble Free Protective Coating

IP.com Disclosure Number: IPCOM000096812D
Original Publication Date: 1963-Dec-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

McGough, DR: AUTHOR

Abstract

A bubble free protective coating applied to printed circuit by silk screening is provided by adding butyl cellosolve acetate (B.C.A.) to polyurethane resin or epoxy resin or alkyd.

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Bubble Free Protective Coating

A bubble free protective coating applied to printed circuit by silk screening is provided by adding butyl cellosolve acetate (B.C.A.) to polyurethane resin or epoxy resin or alkyd.

Entrapped carbon dioxide bubbles in an applied protective coating are dispersed before the coating sets by adding a small amount of B. C.A. This is accomplished because of the high molecular weight and very low vapor pressure of the additive. B. C.A. can be added to any coating material which contains a compatible solvent and liberates excessive carbon dioxide upon application. A smooth coating results when the application is by dipping or with a brush.

As an example, 5% by weight of B. C.A. is added to epoxy resin and filler and is silk screened onto printed circuits as a solder mask and protective coating. Upon drying, the coating is smooth and bubble-free. In another example, 5% by volume of B. C.A. added to polyurethane resin and applied by silk screening was found to remove entrapped bubbles without retarding curing of the coating.

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