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Thermally Conductive, Reworkable, Elastomeric Interposer for Chip to Heat Sink Attachment

IP.com Disclosure Number: IPCOM000110571D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 89K

Publishing Venue

IBM

Related People

Hayden, TF: AUTHOR [+2]

Abstract

In order to maintain an acceptable operating temperature for some integrated circuits, it is required that excess energy (in the form of heat) be removed by attachment of a heat sink directly to the exposed chip surface. Obviously, this attachment is made employing heat-conducting materials. Present materials used in heat sink attachment include metal or metal-oxide filler in epoxy, silicone or mineral oil carrier. Only in the third material set is rework plausible, and in this case, safety factors, high material application and processing costs, and complicated designs become of great concern during initial application and rework.

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Thermally Conductive, Reworkable, Elastomeric Interposer for Chip to Heat Sink Attachment

       In order to maintain an acceptable operating temperature
for some integrated circuits, it is required that excess energy (in
the form of heat) be removed by attachment of a heat sink directly to
the exposed chip surface.  Obviously, this attachment is made
employing heat-conducting materials.  Present materials used in heat
sink attachment include metal or metal-oxide filler in epoxy,
silicone or mineral oil carrier.  Only in the third material set is
rework plausible, and in this case, safety factors, high material
application and processing costs, and complicated designs become of
great concern during initial application and rework.

      This new method consists of an application of material whereby
chips can be readily cooled via a heat-conducting material applied in
a greatly simplified process.  The material consists of a
metal-filled elastomeric film or sheet which is interposed between
the bonded chip or chip assembly and the heat sink.  The chip or chip
assembly can be large or small.  The substrate can be of any material
type such as ceramic, organic or other.

      The film is placed and maintained under slight pressure,
sufficient so as to ensure adequate thermal contact between film-chip
and film-heat sink interfaces.  The interposer film possesses
sufficient mechanical properties such that it does not move once
placed.  Rework of the heat sink occurs simply by removing the
pressure from the material, removing the heat sink, and removing the
heat-conducting film.  These steps are required when the chip needs
to be reworked either before shipping or once in the field.  The
thermally conducting film is reusable.

      The thermally conducting film consists of an elastomer (i.e.,
silicon rubber, butyl rubber, or similar material) that contains
sufficient thermally-conductive filler material (alumina, zinc oxide,
boron nitride, or other metal, metal-oxide, ceramic, or other highly
thermally conductive materi...