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Fabrication of Circuit Lines on Printed Circuit Boards

IP.com Disclosure Number: IPCOM000042439D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+3]

Abstract

Copper current-carrying lines are often used on polymer boards to produce electrical circuits. In the art, a three-layer, peel-apart composite is often used to provide these lines. The composite is bonded to the polymer sheet by an adhesive layer, and comprises a first thin layer of copper, an intermediate layer of a material such as chromium oxide, and a thick overlying copper layer. The thick copper layer and the chromium oxide layer are peeled away to leave the thin copper layer, which can be used as a plating base for the formation of the current-carrying lines. In order to overcome the need for this peel-apart composite, a process is described in which a thin copper layer is evaporated or sputtered onto the polymer sheet.

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Fabrication of Circuit Lines on Printed Circuit Boards

Copper current-carrying lines are often used on polymer boards to produce electrical circuits. In the art, a three-layer, peel-apart composite is often used to provide these lines. The composite is bonded to the polymer sheet by an adhesive layer, and comprises a first thin layer of copper, an intermediate layer of a material such as chromium oxide, and a thick overlying copper layer. The thick copper layer and the chromium oxide layer are peeled away to leave the thin copper layer, which can be used as a plating base for the formation of the current-carrying lines. In order to overcome the need for this peel-apart composite, a process is described in which a thin copper layer is evaporated or sputtered onto the polymer sheet. In this process, a thin copper layer is deposited to a thickness of approximately 1000 A by sputtering or evaporation onto a polymer sheet. The polymer sheet can be either partially cured or a fully cured. After this, a resist layer is applied to the continuous thin film of copper, and is exposed and developed to provide a resist pattern. Electroless plating is then used on the exposed regions of the thin copper layer in order to form the current-carrying lines. Copper is electrolessly deposited to a thickness of approximately 2.2 mils. The patterned resist layer is then stripped away and the entire structure is flash-etched in acid to remove the thin copper layer located between the ci...