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Thermal Fatigue-Resistant Joint for I/C Packaging Applications

IP.com Disclosure Number: IPCOM000101241D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Ozmat, B: AUTHOR

Abstract

This article describes a thermal fatigue-resistant joint which consists of a superplastic alloy (tailored for superior fatigue life through thermal-mechanical processing) and a lower melting point eutectic fusable alloy, which combine to perform the joining of a superplastic alloy to a substrate, board or metal cap.

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Thermal Fatigue-Resistant Joint for I/C Packaging Applications

       This article describes a thermal fatigue-resistant joint
which consists of a superplastic alloy (tailored for superior fatigue
life through thermal-mechanical processing) and a lower melting point
eutectic fusable alloy, which combine to perform the joining of a
superplastic alloy to a substrate, board or metal cap.

      In the "as-formed" state, the superplastic alloy component of a
joint will absorb any thermal mismatch strains, leaving the rest of
the joint relatively stress-free.  In particular, the regions of the
joint next to the top and bottom metallurgies contain brittle
intermetallic phases and are susceptible to fatigue failures.  The
joints described in this disclosure do not stress the intermetallic
or reach brittle regions, however, resulting in a drastic improvement
in fatigue life.  The lower melting point alloy that bonds the
superplastic preform to the substrate, board or cap may be applied by
various techniques, depending upon the particular application, i.e.,
it may be applied as a solid preform (cap join applications), be
screened as a solder paste for surface mount technology (SMT), or be
evaporated or sputtered on a surface.

      Superplastic tall solder preforms can increase the thermal
fatigue life of large DNP SMT ceramic packages that are to be joined
to an epoxy-glass printed circuit board (PCB).  Manufacturing steps
involve the casting, rolling and punching of the superplastic alloy
into a cylindrical shape. The uniform height required...