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Surface Preparation of Polytetrafluoroethylene Additive Copper Plating Adhesion

IP.com Disclosure Number: IPCOM000036907D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Ellis, TL: AUTHOR [+3]

Abstract

The average peel force of copper lines to polytetrafluoroethylene (PTFE) films can be increased from essentially zero to a value greater than the cohesive strength of the fluoropolymer by a combination of surface preparations. The method involves roughening the surface of the fluoropolymer laminate to provide a mechanical bond for the overlying metal seed layer. This seed layer yields a surface which mechanically links the plated copper lines to the top of the roughened polytetrafluoroethylene. If the surface is not roughened before application of the seed layer, peel force measurements cannot be effected, since the plated copper layer falls from the laminate before removal from the copper bath.

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Surface Preparation of Polytetrafluoroethylene Additive Copper Plating Adhesion

The average peel force of copper lines to polytetrafluoroethylene (PTFE) films can be increased from essentially zero to a value greater than the cohesive strength of the fluoropolymer by a combination of surface preparations. The method involves roughening the surface of the fluoropolymer laminate to provide a mechanical bond for the overlying metal seed layer. This seed layer yields a surface which mechanically links the plated copper lines to the top of the roughened polytetrafluoroethylene. If the surface is not roughened before application of the seed layer, peel force measurements cannot be effected, since the plated copper layer falls from the laminate before removal from the copper bath.

The surface of polytetrafluoroethylene films may be prepared by laminating the fluoropolymer between a 7-ounce copper foil and a previously roughened 1/2-ounce copper foil. After lamination, the 1/2- ounce copper foil is etched, exposing the roughened fluoropolymer surface. A seed layer of 1000-1200- angstrom copper is thermally vapor deposited to the roughened surface, and copper is additively plated to a thickness of approximately 1.4 mils. Photoresist is applied to the plated copper, which is then imaged and etched to produce circuit lines. The method is shown in the diagram.

By preparing laminates from 4-mil thick polytetrafluoroethylene and circuitizing with 30-, 50- or 100-mil lines, pee...