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Selectively Dissolvable Photopolymerized Coating Produced by Ultraviolet Light

IP.com Disclosure Number: IPCOM000082662D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Eisenmann, DE: AUTHOR

Abstract

Conductors, such as the lead frame of a dual-in-line semiconductor package, can be coated with a selectively dissolvable insulating film by the process described.

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Selectively Dissolvable Photopolymerized Coating Produced by Ultraviolet Light

Conductors, such as the lead frame of a dual-in-line semiconductor package, can be coated with a selectively dissolvable insulating film by the process described.

An epoxy functional acrylic copolymer, such as a diglycidol ether of bisphenol-A acrylic copolymer containing vinyl unsaturation will undergo rapid polymerization to give cross-linked films, upon irradiation with ultraviolet light from a mercury vapor lamp, in the presence of a photoinitiator such as benzoin. A gaseous nitrogen blanket over the reaction chamber may be necessary to prevent oxygen chain stopping reactions. Portions of the film can be rendered selectively dissolvable in isopropanol, toluene, methyl ethyl ketone or xylene by masking them from irradiation by the ultraviolet light.

Other compositions which can be selectively photopolymerized by ultraviolet light in the presence of a photoinitiator, include polyester or urethane copolymerized with unsaturated carboxylic acids such as methacrylic acid.

The ultraviolet lamp can be 2.2 KV mercury vapor lamp having principal spectral lines at 3660, 3120, and 3200 angstroms.

Permanent electrical insulation and mechanical protection is required for the major portion of a dual-in-line package lead frame, but the ends of the leads must be accessible for soldering or other electrical contact. To apply a selectively permanent insulating coating, the lead frame is dipped or sp...