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Improved Adhesive Performance in Flexible Circuits

IP.com Disclosure Number: IPCOM000114269D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 4 page(s) / 86K

Publishing Venue

IBM

Related People

Jackson, DG: AUTHOR [+3]

Abstract

Current flexible circuit technology dictates the bonding of rigid and semi-rigid components such as heatsinks, wafers, brackets and polyimide stiffeners to the polyimide surface of the circuit. These are normally bonded using an acrylic adhesive such as WA adhesive by DuPont.

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Improved Adhesive Performance in Flexible Circuits

      Current flexible circuit technology dictates the bonding of
rigid and semi-rigid components such as heatsinks, wafers, brackets
and polyimide stiffeners to the polyimide surface of the circuit.
These are normally bonded using an acrylic adhesive such as WA
adhesive by DuPont.

      In general an adhesive will bond to a polymer surface but the
resulting peel strength will be highly dependant upon the surface
condition of the polymer.  An unsuitable surface condition will
result in a low and highly variable peel strength whereas a suitable
surface will produce a higher and significantly less variable peel
strength, creating a more robust process.

      For optimum adhesion, the surfaces to which any adhesive is
applied must be cleaned or converted to a suitable condition before
bonding.  This can be achieved with a surface pre-treatment.

      Several techniques exist to improve the surface condition of a
polymer prior to subsequent processing.  For instance the plastics
industry uses a variety of treatments in order to allow application
of ink or paint.  For example:
  1.  Plasma treatment is used if the components are small and
       three-dimensional.
  2.  Corona discharge treatment is used primarily for films.
  3.  Gas flame treatment is used for papers and three-dimensional
       polymeric items.

      All three processes have a similar effect on the polymer - they
oxidise the surface.  The polymer chains on the surface are broken
and modified to allow the ink or paint to react with the polymer,
giving a better bond due to this formation of chemical bonds between
the adhesive and adherent.

      In principle, the bond within a flexible circuit can be
improved by adopting a similar treatment.  It is known that plasma
treatment has been adopted in some areas, and corona discharge in
other areas.  However, both of these processes have major
disadvantages.

      By app...