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Low Viscosity and High Temperature Stable Gap Filling Material for Glass/Ceramic Substrates

IP.com Disclosure Number: IPCOM000113240D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 119K

Publishing Venue

IBM

Related People

Babich, E: AUTHOR [+5]

Abstract

A technique is described whereby gaps and voids in glass/ceramic substrates are filled with a low viscosity material and cured without outgassing, so as to produce high temperature stable substrates.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Low Viscosity and High Temperature Stable Gap Filling Material for
Glass/Ceramic Substrates

      A technique is described whereby gaps and voids in
glass/ceramic substrates are filled with a low viscosity material and
cured without outgassing, so as to produce high temperature stable
substrates.

      Typically, a mismatch will occur in the thermal coefficient of
expansion of copper and glass ceramic, such that gaps and voids will
occur in multi-layer ceramic (MLC) modules in that the metal will
delaminate from the ceramic.  These gaps and voids must be filled or
a reliability problem will be experienced when the module is
subjected to solvent processing.  In prior art, various methods were
used to fill the gaps and voids, such as:

      Thermal - Typically contains a solvent such that the material
is porous after curing.  Also, after temperature cycling, gaps will
reopen.

      Siloxane backfill - Typically consists of 1) polydimethyl
siloxane - silanol terminated.  2) glycidoxy/propyltrimethoxy/silane.
3) zinc octoate in polydimethyl siloxane (50%  conc.).  There is
approximately 20%  weight loss during the cure cycle and the
temperature stability of the system may not be adequate (although
hermetic parts have been obtained, the safety margin is small).  The
disadvantage of the siloxane backfill is in the chemistry of the
crosslinking process.  The crosslinking agent contains three
methoxy-groups which react during thermal treatment with hydroxy
functionalities, with the formation of methyl alcohol, or with each
other evolving dimethyl ether.  This does not allow the preparation
of non-porous filling.  Another component, Zn octoate is applied as
50% solution in low molecular weight silicones, which are a ballast
and cannot be involved in the crosslinking process.  They evaporate
or degrade at high temperatures.  However, the Zn-catalyst helps to
crosslink the composition at 200ºC, but causes depolymerization
of polysiloxanes at 300-400ºC with the formation of low molecular
weight cyclosiloxanes, which evaporate also and can cause structure
damage and contamination.

The concept described herein overcomes the above disadvantages by
using materials such as:

      Liquid low viscosity, polydimethyl-siloxanes with terminal or
pendant glycidoxypropyl-groups, including disiloxane or T-structure
oligomers - polyfunctional molecules containing two or more
glycidoxy-groups.

      Liquid low viscosity, polydimethylsiloxanes with terminal or
pendant aminopropyl-groups, including disiloxane or T-structure
oligomers - polyfunctional molecules containing two or more
amino-propyl (or amino-alkyl, amino-phenyl) groups.

      Liquid polydimethyl siloxanes with pendant or terminal
HO-groups, including cyclolinear structures and ledde...