Browse Prior Art Database

THERMAL EXPANSION DECOUPLER

IP.com Disclosure Number: IPCOM000006449D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2002-Jan-04
Document File: 1 page(s) / 85K

Publishing Venue

Motorola

Related People

David G. Lamoreaux: AUTHOR

Abstract

This publication describes a thermal expansion decoupler for use in packaging electronic parts for use in aerospace and avionics hardware.

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MOTOROLA INC. Technical Developments Volume 15 May 1992

THERMAL EXPANSION DECOUPLER

by David G. Lamoreaux

  This publication describes a thermal expansion decoupler for use in packaging electronic parts for use in aerospace and avionics hardware.

  Thermally induced mechanical stress resulting from mismatch in thermal expansion coefficients between interfacing elements is a commonly occurring problem in electronic hardware. This problem is especially severe in microwave electronic components and assemblies, which typically include various Kovar parts that must be attached to an slutninum chassis providing a low impedance ground connection. A previous solution to this problem involved soldering the Kovar parts to a Kovar carrier and then mechanically attaching the Koyar carrier to an aluminutn housing. Several small ground ribbons or wires were then attached between the carrier and the housing to achieve the reqired low impedance RF ground connection. A distinct disadvantage of this approach is the added cost and weight of the carrier as well as the additional assembly steps required in order to attach the carrier and ground ribbons. Soldering the Kovar parts directly to a suitably prepared or plated aluminum housing provides optimum electrical groundin& but also produces thermal expansion coe5cient mismatch which results in severe mechanical stresses which eventually degrade the solder joints to an unacceptable level as a result of exposure to thermal cycling.

  The thermal expansion mismatch decoupler described herein allows Kovar to be indirectly soldered to the aluminum chassis by acting as a them-rat expan- sion transition, thus eliminating the need for Kovar car- riers and ground ribbons.

  The embodiment of this concept includes various laminated structures where the materials in the lay-up are selected to minimize thermally induced mechanical stress between a housing or chassis and any electronic part atlixed thereto. A particular example is shown in

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