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December 2001

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Subject:
From:
David Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 21 Dec 2001 08:34:05 -0600
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text/plain (78 lines)
Hi Andre! I would suggest you get a Scanning Electron Microscopy element
scan conducted on the white residue. The white residue you describe could
be tin or lead oxides, lead crystals due to a component plating problem,
calcium crystals due to poor washing, etc. The SEM analysis will help
eliminate the inorganic (e.g. metallic) possibilities leaving the possible
flux related  (organic) source causes. Good luck and Happy Holidays.

Dave Hillman
Rockwell Collins
[log in to unmask]





Andre Leclair <[log in to unmask]>@ipc.org> on 12/19/2001 07:57:26 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>

Sent by:  TechNet <[log in to unmask]>


To:   [log in to unmask]
cc:

Subject:  [TN] white powder on leads


Hi All

Here is another residue issue

We have an assembly which has a white residue remaining after wash.
The board is completely SMT (WS609) using a DI-Wash process,  the board is
spotless except for one location.  The location is a QFP (from CRONTEL),
the white powder is on the leads of the IC only.  There is not a spot on
the PCB.

The Powder dry brushes extremly easily. On a few of the leads ( usually
about half way up the lead, nver near the joint)after brushing there is
evidence of flux residue( yellow sort of like Crystal Flux residue) in
spots.
We have put a few boards through the Omega with readings lower then
2.3microgram/sq.inch.

Could this be something the part manufacture has left/put on the leads? I
have noticed that the plating is thin on the leads (exposed copper on the
faces) the leads also look like sheared stock ( exposed copper on the
sides)

Thanks
Andre

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