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Refractory Metal Powder Filled Braze

IP.com Disclosure Number: IPCOM000122738D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 63K

Publishing Venue

IBM

Related People

Doscher, MJ: AUTHOR

Abstract

A method is described in which a low stress braze connection between a metal and ceramic is achieved. Such a low stress connection can enable the use of inherently weaker ceramic materials, or effectively increase the ceramic's critical flaw size in close proximity to the stressed brazed connection.

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Refractory Metal Powder Filled Braze

      A method is described in which a low stress braze connection
between a metal and ceramic is achieved.  Such a low stress
connection can enable the use of inherently weaker ceramic materials,
or effectively increase the ceramic's critical flaw size in close
proximity to the stressed brazed connection.

      Many metal / ceramic braze joints have a natural tendency for
high residual stress.  This arises from the difference in the thermal
coefficient of expansion (TCE).  The TCE of the braze metal may
typically be from 2 to 10X that of the ceramic, depending on the
exact materials being used.  Upon cooling from the joining
temperature, the braze metal contracts to a greater extent than the
ceramic.  The problem can be aggravated by the use of large or
excessive braze metal volume in a given connection.  This can result
in peeling or separation of the braze metal from the ceramic, or low
stress failure of the joint.

      A ceramic system, as is the case for any material, is chosen
based on trade-offs of the various mechanical, physical, and
processing characteristics.  Materials with ideal physical properties
based on one or more criteria are often found to have less than
desirable mechanical strength. In such a case, minimizing the
residual stress of a brazed metal to ceramic connection is all the
more necessary. Alternatively, a lower strength ceramic with
otherwise optimal properties can be used if the residual...