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Filling Isolating Holes in Thick Multilayer Inner Layers of Circuit Boards without Pores

IP.com Disclosure Number: IPCOM000109251D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Kaeswurm, G: AUTHOR [+3]

Abstract

The supply layers of future high-end circuit boards will have a relatively thick Cu metal film (> 200 mm). For effective electrical isolation after further processing, the drilled hole pattern will have to be filled completely with epoxy resin. Filling the holes is difficult, as pores easily form which reduce the isolation characteristics of the resin. This article proposes an inexpensive simple process by which the isolating holes may be filled without pores developing.

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Filling Isolating Holes in Thick Multilayer Inner Layers of Circuit Boards without Pores

       The supply layers of future high-end circuit boards will
have a relatively thick Cu metal film (> 200 mm).  For effective
electrical isolation after further processing, the drilled hole
pattern will have to be filled completely with epoxy resin.  Filling
the holes is difficult, as pores easily form which reduce the
isolation characteristics of the resin.  This article proposes an
inexpensive simple process by which the isolating holes may be filled
without pores developing.

      For this purpose, a carrier foil of, say, TEFLON*, is
resin-coated on one side.  Then, each side of the thick multilayer
inner layer with the isolating holes to be filled is covered with a
foil, with the coated side facing the inner layer, and bonded in
several layers between planishing plates in the laminating press.
The uncoated side simultaneously acts as an isolating foil for the
planishing plate.

      The precross-linked resin on the carrier foil liquefies,
filling the isolating holes in the multilayer inner layers without
pores.  After lamination, the carrier foil is peeled off and the
inner layers are processed further.

      It is also possible to resin-coat both sides of a carrier foil.
In this case, foils and multilayer inner layers coated on both sides
are alternately stacked and bonded between planishing plates in the
laminating press.

      The advantages of th...