Mike Fenner takes me to task that my 'reply did not equate with accepted
industry wisdom' 
Well there are all kinds of 'wisdom.' Manko in 'Solders and Soldering' lists
a 56Sn/39Pb/5Ag solder and Klein Wassink in 'Soldering in Electronics' gives
a concentration of 5% Ag as slowing down the dissolution rate of Ag (which is
about 8-times higher than copper) and that thin solder layers can contain
upwards of 15% Ag. The formation of the IEEE Compliant Lead Task Group in
1983 was precipitated by the Ag-plated PLCC-J leads from TI, where SEM
results showed that in the thinnest solder joint sections half of the solder
joint contained nothing but Ag and Sn. These PLCCs, by the way, fell off
circuit boards made by IBM-Austin to the brittle and weak Ag3Sn intermetallic
compounds, which of course also contain large amounts of Ag. So, yes, silver
can have rather bad practical consequences.

Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ  07945  USA
Phone & Fax: 201-543-2747
E-mail: [log in to unmask]



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