Hi Joyce - my response would "it depends" (and Doug gets another Diet Mt. 
Dew) as Rockwell Collins utilizes immersion silver pwb surface finishes on 
many IPC Class 3 type products with no reliability issues.

Dave



Joyce Koo <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
04/15/2009 04:11 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Joyce Koo <[log in to unmask]>


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Subject
Re: [TN] Gold/Tin Intermetallics, why are we afraid?






"ImAG finishes have a 12-month shelf life in a controlled environment
(<35[degrees]C/<85[degrees] RH), which can be significantly shortened
when exposed to air pollution with high sulfur and chlorine content.
Silver embrittlement Embrittlement

A general set of phenomena whereby materials suffer a marked decrease in
their ability to deform (loss of ductility) or in their ability to
absorb energy during fracture (loss of toughness), with little change in
other mechanical properties, such  ([Ag.sub.3]Sn intermetallics) of
solder joints may occur when the finish thickness exceeds IPC-4553
recommendations and Pb-free, high silver content solders are used. ImAG
is not recommended for high-reliability assemblies that must meet
IPC-6010 Class 3 requirements, but is acceptable for Classes 1 and 2."

http://www.thefreelibrary.com/Will+discoloration+tarnish+ImAg+reliabilit
y%3F+Watch+for+silver...-a0193896272

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Wednesday, April 15, 2009 4:34 PM
To: [log in to unmask]
Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?


 Hi Vlad,
I cannot comment on your specific case, but look at the pics below to
see 
Ag-embrittlement.
Sorry 'Netters, IPC strips pics.

Werner

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