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From [log in to unmask] Wed May 15 17: |
59:09 1996 |
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Phil -
What is your cleaning process? If you have been using FTIR to look
at the residue make sure that your suspect materials have seen the
same temperature excursions as the residue has! Your FTIR fingerprint
will be different due to changes in the suspect material because of
the temperatures. These changes will give you an FTIR false negative
test result on your suspect materials and lead you to no longer
suspect the 'suspect" samples. I have seen rosin fluxes look quite
different after going through a soldering and cleaning process than
just testing the flux out of the bottle unprocessed.
Dave Hillman
Rockwell CACD
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______________________________ Reply Separator _________________________________
Subject: White residue between soldered leads
Author: [log in to unmask] at ccmgw1
Date: 5/7/96 3:21 PM
I have a white residue problem that is becoming all to common. The
white residue appears between and behind soldered leads on the
polyimide substrate. It does not appear on or inside of
soldered-through holes. On some boards I can find it between all the
leads. On others I see it only between a few leads.
I have analyzed this residue many times with FTIR. Everytime, I get
proteinaceous matter (protein). I see no evidence of rosin-based or
water-soluble flux, but at times I see cellulose fibers mixed in with
the proteinaceous matter.
What is this stuff?
We have considered:
1. skin residue (dandruff)
2. debris from camel hair brushes
3. fungus
There appears to be far too much residue to consider 1. and 2.
The problem appears after the final cleaning/rinsing step.
Any ideas would be greatly appreciated.
Thank you.
--Phil
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