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February 2013

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From:
Steven Creswick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steven Creswick <[log in to unmask]>
Date:
Fri, 8 Feb 2013 13:28:23 -0500
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Just some old thoughts ...

I suppose it is kind of a scary, uncontrollable thought, but we used to do
the same technique for manually burnishing PdAg thick film metallizations
for soldering, or conductive adhesive component attachment for hybrid
applications back in the 70's.  We did not use an electric eraser, however.

That was back in the earlier days of fritted metallizations where the glass
often came to the surface of the metallization, if the firing profile was
not optimum.

Only certain pink erasers were allowed.  And due to operator skill, certain
operators were only allowed to do it.  A light touch, by a good operator,
could make a lot of pain go away .... I am talking conductive wetting
characteristics here.

Some particularly nasty fritted PtAu's, or PtPdAu metallizations got hit
with fiberglass brushes!   Yikes!  Even more scarey, but it worked.

Once mixed bonded systems hit the scene, much of this went away, but you
would be amazed at how a skilled operator could clean things up, and the
part would be more reliable, or so it seemed at the time by passing all
manner of environmental, PIND, and life tests.

With the right operator, it could still be viable, but I probably wouldn't
seek to do it on Production boards & Quantities.  Nowadays, it is easier to
plasma, or bring them back to supplier.

For someone with a small board, or portion of board, that doesn't have
access to a plasma cleaner, a light touch with a clean pink eraser just
might clean things up, without taking off the plating.  

Actually, I have found that most cleanroom wipes are quite abrasive if you
can rub them on a surface to be cleaned.  Kind of tough on a PWB, however,
as the wipe shreds to pieces quickly and really leads to all manner of
particulates and fibers.

Definitely not proposing the widespread use of an eraser either, but it may
not hurt to be kept in mind for emergencies...

Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
                         616 834 1883






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