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Use of Sacrificial Copper Allowing Removal by Mechanical Methods

IP.com Disclosure Number: IPCOM000039954D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Carey, TJ: AUTHOR [+2]

Abstract

Copper foil used in the production of multilayered printed circuit boards, or the like, normally has a smooth or bright side and a rough or oxide side. The rough or oxide side is oriented next to the prepreg in order to achieve the optimum adhesion between the prepreg and the copper foil during lamination. This copper foil must occasionally be removed, which is conventionally done by chemical etching using either cupric chloride or ferric chloride etchants. The chemical etching process introduces a waste by-product which must be disposed, and the etchants themselves are hazardous at the higher temperatures required for their use. A described process eliminates the need for etching by using mechanical means. In producing the board there are two lamination steps required.

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Use of Sacrificial Copper Allowing Removal by Mechanical Methods

Copper foil used in the production of multilayered printed circuit boards, or the like, normally has a smooth or bright side and a rough or oxide side. The rough or oxide side is oriented next to the prepreg in order to achieve the optimum adhesion between the prepreg and the copper foil during lamination. This copper foil must occasionally be removed, which is conventionally done by chemical etching using either cupric chloride or ferric chloride etchants. The chemical etching process introduces a waste by-product which must be disposed, and the etchants themselves are hazardous at the higher temperatures required for their use. A described process eliminates the need for etching by using mechanical means. In producing the board there are two lamination steps required. The first step involves producing a power laminate consisting of two power planes separated by dielectric material. The sacrificial copper is used on the two outside extremities of this power laminate and must be removed prior to further processing. The configuration is seen in the figure. The sacrificial copper is now removed by mechanical methods, leaving a clean, active, virgin surface free of epoxy dust or copper pits. This virgin surface must be rebondable in the subsequent lamination step and have a minimum bond of 3 pounds pull on a one-inch-wide strip. The second lamination step takes the power laminates, with the sacrificial...