Browse Prior Art Database

Hermetic Sealing of Ceramic Packaging Devices by Siloxane Based Polymers

IP.com Disclosure Number: IPCOM000106972D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 91K

Publishing Venue

IBM

Related People

Brownlow, JM: AUTHOR [+3]

Abstract

Disclosed is a process for hermetic sealing of microporous ceramic electronic packaging devices against fluid penetration, in which siloxane-based polymers, after suitable treatment, exhibit satisfactory performance through thermal cycling to 350-400~C in nitrogen.

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This is the abbreviated version, containing approximately 52% of the total text.

Hermetic Sealing of Ceramic Packaging Devices by Siloxane Based Polymers

       Disclosed is a process for hermetic sealing of
microporous ceramic electronic packaging devices against fluid
penetration, in which siloxane-based polymers, after suitable
treatment, exhibit satisfactory performance through thermal cycling
to 350-400~C in nitrogen.

      The use of copper or noble metal circuits inside ceramic
electronic packaging devices presents a serious problem. Because of
the large differences in the thermal expansion coefficients (CTEs)
between metal and ceramic, large thermal stresses develop when the
composite material is cooled from sintering to ambient temperature
and during subsequent thermal cycling, frequently leading to parting
of the two materials or to cracking of the ceramic. Incorporating a
judiciously chosen second, lower-CTE material in the conducting paste
prior to sintering can reduce the thermal stresses. However, in such
modified "composite" vias, some interconnected microporosity often
remains after sintering; this makes the substrate susceptible to
invasion by process chemicals, which may be locked in with
potentially deleterious effects.

      This remaining porosity in the via structure can be filled by a
third, liquid phase which is subsequently hardened and made into an
integral part of the composite material. This third material should
have a special combination of properties:
      The final solid phase should be rubbery, in order to
      avoid thermal stresses with the ceramic and/or the
      metal. This requirement restricts the solution to a
      polymeric material.
      The liquid phase should have a relatively low viscosity
      (most liquid polymers would not do) and low surface
      tension in order to penetrate the thinnest capillaries
      present.
      Gas evolution during curing should be low or absent;
      alternatively, the material should be fluid and tacky
      enough to "heal" itself after most of the gas has left,
      but before final cross-linking. To minimize deleterious
      effects of gas evolution, systems in which a volatile
      solvent is a major component are best avoided.
      The cured filling material should have high thermal
     ...