Hi Bev,
The industry found out—and since forgot except for a few old-timers like
me—in 1982, what silver can do to solder joints when TI moved some of its
PLCC production to Singapore. There somebody decided to Ag-plate the leads.
At the first unfortunate recipient of this product, IBM-Austin, the PLCCs
started to literally fall off the PCBs when slight bending, such during
fixturing for functional testing, put even very small loads onto the solder
joints. As a consequence of this scary news (nobody knew about the Ag yet and
compliant leads were just invented and without history), 17 competing
companies joined forces and formed the IEEE Compliant Lead Task Force.
Silver, it turns out creates an even weaker intermetallic compound (IMC) with
tin than does gold. The necessary IMC concentration necessary for this effect
is about the same as for Au.
Because of legal problems (the 2 companies with the lowest PLCC fatigue lives
threatened to sue everybody involved in the IEEE CLTF), the results, except
for some preliminary data, were never published.
Unfortuna tely I am on rthe road, so I can onlygive you my own publications,
but some related references are listed in them:
Engelmaier, W., "IEEE Compliant Lead Task Force--Phase I: Correlation and
Analysis of Solder Joint Fatigue Results Obtained at Different Cyclic
Frequencies and Temperatures," Proc. 5th Annual Int. Electronics Packaging
Conf. (IEPS), Orlando, FL, October 1985, p. 279.
Engelmaier, W., "IEEE Compliant Lead Task Force--A Progress Report," Proc.
8th Annual Int. Electronics Packaging Conf. (IEPS), Dallas, TX, November
1988, p. 891.
There were some papers by Jack Balde and others.
Sorry, but I can not be of more help.
Werner Engelmaier
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