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Placement of an Isolation Border on Power Planes

IP.com Disclosure Number: IPCOM000051065D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Carey, TJ: AUTHOR [+2]

Abstract

In manufacturing high technology printed circuit boards, pre-drilled two-ounce copper foil is used for the power planes. This pre-drilled hole pattern must then be isolated from the remaining copper inner planes. The standard practice in manufacturing power planes for multi-layer printed circuit boards uses photolithographic techniques which require the use of photoresist and the subsequent chemicals normally used in a subcomposite manufacturing.

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Placement of an Isolation Border on Power Planes

In manufacturing high technology printed circuit boards, pre-drilled two- ounce copper foil is used for the power planes. This pre-drilled hole pattern must then be isolated from the remaining copper inner planes. The standard practice in manufacturing power planes for multi-layer printed circuit boards uses photolithographic techniques which require the use of photoresist and the subsequent chemicals normally used in a subcomposite manufacturing.

It is proposed to use a "dry" process to accomplish the two basic requirements of producing power planes without using chemicals. First, the pre-drilled hole pattern in the two-ounce copper foil is partially isolated by mechanically punching or milling a 1/8" wide slot around the periphery of the hole pattern, leaving 1/4" retainer supports every three inches to maintain the support and integrity of the registration from the location holes to the drilled hole pattern.

The registration slots are precisely punched into the copper foil prior to drilling and must be maintained throughout the lamination processes. Once the isolation border with the retainer has been milled into the two-ounce copper foil, the next step is to remove the copper retainer while maintaining the registration from the location slots to the drilled hole pattern.

This is accomplished by first applying one layer of epoxy/glass prepreg to one side of the two-ounce copper foil. The epoxy/glass prepreg is n...