Hi Tom! I took a look at the phase diagrams for the gold/tin and palladium/tin
systems (I couldn't find any ternary information)  and I don't think you can
form a Au/Pd/Sn alloy under soldering conditions. The thermodynamics/kinetics
for the tin to form gold/tin intermetallics or  palladium/tin intermetallics are
such that a ternary should not occur. There has been an ocean of published data
on the formation of gold/tin intermetallic  and some limited information on
palladium/tin intermetallics. The Au4Sn and the Pd4Sn5 seem to be the key
troublemakers. Both of the intermetallic phases can be avoided by controlling
the Au or Pd thicknesses. Hope this helps.

Dave Hillman
Rockwell Collins
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"Thomas A. Carroll" <[log in to unmask]> on 10/19/99 10:10:58 AM

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Subject:  [TN] Gold, Palladium Tin Alloys



To All TechNet Subscibers,

Does anyone have information about a possible alloy that might form when using
the electroless nickel, electroless palladium, immersion gold surface finish and
a solder alloy that might form with tin based solders.  Specifically, does
anyone have information or phase diagrams on the potential gold-palladium-tin
alloy that might form?  Any assistance or data would be appreciated.

Thomas A, Carroll
Hughes Space and Communications Co.
P.O. Box 92919   M/S - S41/A345
Los Angeles, CA 90009-2919
Phone: 310-662-9268
FAX:      310-416-6971
email:   [log in to unmask]

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