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Composite Circuit Panel Design Features to Minimize Copper Blistering in a Full Additive Plate Process

IP.com Disclosure Number: IPCOM000036440D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Bhatt, AC: AUTHOR [+4]

Abstract

This article describes a technique that will prevent the formation of copper blisters on the external mounting plane areas of composite circuit panels fabricated with the full additive plate process.

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Composite Circuit Panel Design Features to Minimize Copper Blistering in a Full Additive Plate Process

This article describes a technique that will prevent the formation of copper blisters on the external mounting plane areas of composite circuit panels fabricated with the full additive plate process.

Circuit boards fabricated with the full additive plate process * are subject to the formation of copper blisters when a sufficiently large area of copper is being plated. These copper blisters are characterized by the formation of a bubble and failure at the copper/ epoxy interface. This problem limits the design of pattern dimensions and can cause panels to be scrapped for blistering in critical areas, such as capacitor pads on external mounting planes. The blister formation is associated with the evolution of gas during additive plating and the physical constraint of this gas by the layer of copper being deposited.

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This blistering can be ameliorated by the Z direction construction of the printed circuit board, rather than the X-Y considerations used heretofore in the pattern design. This relationship is demonstrated in Fig. 1. A dielectric thickness of 8 mils for a pad dimension of 150 mils X 100 mils results in a blistering frequency of 60%. A dielectric thickness of 11 mils will, however, reduce the blistering frequency to 14%.

A second approach to using Z direction construction is to employ pilot holes in power plane areas directly underneath su...