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Alternative Metallurgy for Glass Ceramic Modules Disclosure Number: IPCOM000103820D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 61K

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Brady, MJ: AUTHOR [+5]


Disclosed is an alternative metallurgy and the processing steps for its use in the multi-layer glass ceramic modules.

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Alternative Metallurgy for Glass Ceramic Modules

      Disclosed is an alternative metallurgy and the processing steps
for its use in the multi-layer glass ceramic modules.

      The coefficient of thermal expansion (CTE) of glass ceramic
used in IBM* high end packages matches that of Si closely
(approximately 5 ppm/º C).  The metallurgy used in these
modules should also have similar CTE so that there are no internal
stresses generated during cooling from sintering temperatures due to
CTE mismatch.  Internal stresses generated from any such thermal
excursions can lead to cracking in the lines or vias in the package,
lowering yield significantly.  Metals like molybdenum (Mo) and
tungsten (W) etc. show CTE similar to the glass ceramic, however,
they can not be co-sintered with glass-ceramic at its sintering
temperature (800-900ºC) due to the refractory nature of W
and Mo.

This disclosure proposes  W, Mo, or other such CTE matched metals
coated with copper as the optimized metallurgy.  This disclosure
further proposes the use of certain alloys forming liquid phase at
temperatures around 750º C to sinter the metallurgy
concurrently with glass ceramic.  The alloys forming the liquid phase
are so chosen that they dissolve the copper coating partially and the
melting point of the copper enriched liquid phase keeps on increasing
monotonically with increasing copper content, finally increasing
beyond the sintering temperature, at which point the liquid phase
solidifies.  The thickness of the copper coating on the particles and
the amount of the liquid phase forming alloy is adjusted such that
complete densification is achieved at about the same time when the
liquid phase solidifies due to copper enrichment.  The copper coating
also serves as a protective coating to prevent the oxidation of W, Mo
particles during the burning out of the organic binder materials
prior to the commencement of sintering.

      Several alloys of Cu and Au have been identified for use as the
liquid phase forming alloys.  The possible copper alloys...