Hello Lorraine,
Can't help you with the articles, but we have an immersion tin board that
has been sitting on a shelf for the last 12 months that at least still
appears to be solderable. (still bright - no blackening)
It was packaged in a heat sealed plastic wrap by our supplier.
Unwrapped boards exhibit tarnishing after a few months - less if handled.

regards,

Phil.

Phil Dutton C.I.D.
Senior CAD Technician
IPC Certified Interconnect Designer

Tenix Defence Pty Ltd
Electronic Systems Division
Second Avenue, Technology Park,
Mawson Lakes.  SOUTH AUSTRALIA  5095


-----Original Message-----
From: Reid, Lorraine [mailto:[log in to unmask]]
Sent: Thursday, 27 June 2002 01:05
To: [log in to unmask]
Subject: [TN] Shelf life of Immersion Silver Fabs


A couple of months ago there was a discussion thread running on the merits
of immersion silver boards.  One of the contributors (Jack Olson, I think)
made the comment that -

"Most sources say a silver surface will not be solderable after a month or
so unprotected. (Even in a baggie it will be okay a year later?)"

What are these "sources"?  Are there published articles giving guidelines on
how fabs should be packed to maximise shelf-life?

Basically, we've just received some Immersion Silver boards from fab house
which were wrapped in tissue paper then bubble-wrap.  Not in sealed bags or
anything.  They claim boards should be OK, even though we won't be using all
supplied boards for a few months.  They have offered to repackage if we
insist on it.  I'm a little concerned, having seen how Immersion Silver
boards can easily tarnish.

I'd be interested to hear what TechNet contributors have to say on this
matter.

Thanks in advance for your replies

Lorraine Reid
Senior Electronics Engineer
Trivirix International
tel. +44 (0)28 9096 0932

-

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