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Wire Bonding Adhesive for Multiwire Circuit Boards

IP.com Disclosure Number: IPCOM000053078D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Alpaugh, WA: AUTHOR [+3]

Abstract

In the multiwire circuit board process, insulated copper wires are embedded in an adhesive layer by a wiring machine. A layer of epoxy glass pre-preg is hot pressed over the wires and adhesive to encapsulate the wires. Electrical connections to the wires are made by drilling through the board and wires and making a plated through hole with plated connection to the end of the wire. The plated through hole is made by catalytically seeding the hole wall followed by electroless copper plating.

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Wire Bonding Adhesive for Multiwire Circuit Boards

In the multiwire circuit board process, insulated copper wires are embedded in an adhesive layer by a wiring machine. A layer of epoxy glass pre-preg is hot pressed over the wires and adhesive to encapsulate the wires. Electrical connections to the wires are made by drilling through the board and wires and making a plated through hole with plated connection to the end of the wire. The plated through hole is made by catalytically seeding the hole wall followed by electroless copper plating.

A problem has existed in that the electroless copper plating takes well over the epoxy glass portions of the hole but poorly over the wire-bonding adhesive layer, which results in plating voids at the adhesive layer. A new adhesive material has been found which overcomes this problem and also has additional advantages. The new material is designated FM238*. It is a film and is applied by hot lamination.

Good electroless copper take occurs over FM238 when properly surface conditioned and seeded. With minimal seeding, good copper-to copper plated joints are obtained which easily withstand solder shock. It is desirable to condition the adhesive surface to create good binding of the seeder. The conditioning consists of exposure to a hot alkaline permanganate solution for a few minutes. This creates a cratered microetched surface that holds the seeder.

FM238 is thermosettable by baking and hardenable to any desired degree by increas...