Hi Rob - I went digging through my files and found a reference made by
Klein Wassink that recommended  the Zinc level be limited to less than
0.005% due to it causing drossing, grittiness, and grain boundary weakening
(ok, solder colony weakening for those who don't like the words grain
boundary and solder in the same sentence). I couldn't find anything on
Cobalt, I don't have a Sn-Co phase diagram and the Pb-Co phase diagram
shows that lead and cobalt don't like each other at all. Hope this helps.
Did you have a suspected contamination issue?

Dave Hillman
Rockwell Collins
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[log in to unmask] on 10/20/97 10:56:31 AM

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Subject:  [TECHNET] Assembly




Hi Technet,
        Does anyone have information regarding the maximum percentage of
cobalt and
zinc that are permissible in a Sn-Pb solder joint?  Thanks in advance for
any
answers.
        Rob Schetty
        LeaRonal Inc.
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