Are you saying it will be for eberhard to remove?
Dewey

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Thursday, September 07, 2006 2:17 PM
To: [log in to unmask]
Subject: Re: [LF] Immersion Silver and tarnish

Hi Genny - I recommend avoiding any type of cardboard whenever possible
to
avoid the sulfur contamination issue altogether. However, if you put an
immersion silver pwb wrapped in silver saver paper in an unsealed poly
bag
which then sits in a cardboard box,  you should not have any sulfur
contamination issues in most typical cases.  Immersion silver can have
some
level  of tarnish which will not impact solderability - Don Cullen of
MacDermid presented a paper at an IPC Fall meeting documenting an
approximate level of acceptable tarnish. I will jump up on my soapbox
and
recommend that you never use a "pearl pink eraser" to "clean" a
solderable
surface. The use of a pearl pink eraser is an old metallurgist tool of
determining whether a corrosion/tarnish attack is a surface phenomena or
a
subsurface phenomena (one of my mentor's taught me the trick many moons
ago
when dealing with sheet metal corrosion) - unfortunately some misguided
soul long ago considered this process to be a "cleaning" process and now
we
stuck with an incorrect idea. You would be amazed at the residue that
can
potentially be left on a "treated" pad after a pearl pink eraser
treatment.

Dave Hillman
Rockwell Collins
[log in to unmask]




             Genny Gibbard
             <Genny.Gibbard@VC
             OM.COM>
To
             Sent by: Leadfree         [log in to unmask]
             <[log in to unmask]
cc
             >
 
Subject
                                       [LF] Immersion Silver and tarnish
             09/07/2006 02:58
             PM


             Please respond to
                "(Leadfree
                Electronics
             Assembly Forum)"
             <[log in to unmask]
             >; Please respond
                    to
               Genny Gibbard
             <Genny.Gibbard@VC
                  OM.COM>






Are cardboard ESD boxes a source of sulfur that could tarnish Immersion
Silver PCBs?
If you have tarnish on a PCB, would you ever try to remove it with an
eraser?

Just wondering...

Genny

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