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Multilayer Printed Circuit Board

IP.com Disclosure Number: IPCOM000089231D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Haining, FW: AUTHOR [+2]

Abstract

When glass cloth strands from the epoxy-glass laminating material (prepreg) make contact or near contact between the plated thru hole (PTH) and the buried power planes of the multilayer printed circuit, there is a possibility of insulation resistance failure. Thus, when a potential is imposed between the PTH and the power plane, conductive material may migrate from one to the other causing a short or low resistance connection.

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Multilayer Printed Circuit Board

When glass cloth strands from the epoxy-glass laminating material (prepreg) make contact or near contact between the plated thru hole (PTH) and the buried power planes of the multilayer printed circuit, there is a possibility of insulation resistance failure. Thus, when a potential is imposed between the PTH and the power plane, conductive material may migrate from one to the other causing a short or low resistance connection.

To prevent contact between the glass fibers and the power planes, an epoxy barrier is imposed between the two. This epoxy barrier acts as an insulating layer on the conductor(s). The dielectric barrier is formed by coating the copper foil with epoxy laminating resin on one side before the raw power cores are laminated. This forms a dielectric barrier that prevents contact between the glass fibers of the prepreg and the copper foil. Thus, it prevents one of the most prevalent failure mechanisms during insulation resistance testing at elevated temperatures and humidities.

Briefly, the treated side of copper foil or other suitable foil material is coated with epoxy laminating resin. Next, two sheets of coated foil, with a suitable number of sheets of prepreg between, are laminated to form a raw power core. The cores are then circuitized and formed into multilayer printed circuits by conventional techniques.

The power cores so formed can be coated again after circuitizing to prevent contact from glass strands in...