Hi Gaby - the issue of silver embrittlement was a topic that Werner and I 
had long, torturous, fun, engaging discussions about silver embrittlement 
(I miss Werner, he would have some great comments on this topic). Werner 
was a  participant in a industry consortia in the 1980's where a silver 
embrittlement issue happened with some CLCC components. The project data 
was semi-restricted so a complete report was never published. The IPC 4-14 
committee did some of the most recent work on the topic - look in the IPC 
4553 specification, Appendix 6 for a summary of that work. Also IPC-TR-586 
contains the entire test report covering the thermal cycle testing the 
committee completed.  A version of the TR-586 was also published in the 
2008 SMTA Toronto Conference proceedings. It takes a greater silver 
content in a solder joint to cause embrittlement than gold content. The 
4-14 committee showed that you can have up to 30 uinches of immersion 
silver surface finish and not have an embrittlement situation under 
standard SMT process conditions (and there is no reason to have 30 uinches 
of ImAg on a pwb!). The amount of silver in Sn62, even combined with a 
typical ImAg surface finish, won't result in a silver embrittlement 
situation.  Werner had a good point on SAC solder - all sources of silver 
need to be accounted for when determining if you could have too much 
silver - the silver content of the solder should not be overlooked. Hope 
this helps.

Dave Hillman
Rockwell Collins
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Gabriela <[log in to unmask]> 
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Subject
[TN] Silver embrittelment in solder joints






Is there anyone who studied if tin lead solders with 2% silver used for
soldering gold plated leads are less reliable than the classic 63/37
tin/lead solder for the same application because of silver embrittlement 
in
addition to gold embrittelment?
The late Werner Engelmaier published an article:

 
<
http://www.globalsmt.net/smt/index.php?view=article&catid=42%3Acolumns-wern

er-engelmaier&id=13358%3Asolder-joint-embrittlementits-not-just-gold&format=
pdf&option=com_content&Itemid=65>
http://www.globalsmt.net/smt/index.php?view=article&catid=42%3Acolumns-werne

r-engelmaier&id=13358%3Asolder-joint-embrittlementits-not-just-gold&format=p
df&option=com_content&Itemid=65

This article explains silver embrittelment as an addition to gold
embrittelment in lead free solders used for soldering gold plated  leads
with SAC.

Is there a correlation between my question and the article?
Gaby



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