Hello Peter Duncan
Humiseal's Stripper 1080 does an excellent job. You already described using
the 3 wash/strip pans and I've found that works very well. We never did an
analysis on our stripping pans. We had some motivated operators that would
change out the solution once they saw it lose effectiveness or start leaving
a conformal coating ring in the pan. Since it was a single 8 hour shift/day
process the pans would remain covered in the fume hood when not in use.
This was for a real low/no volume process otherwise we might have had
tighter controls. The used stripper was poured into 10 gallon totes that
were picked up by the haz mat folks for disposal.
I also played with a "water pick" device that could get stripping solution
under components real well - can't remember the name. We learned real quick
that spot stripping didn't work - you have to strip the entire board, run it
through the aqueous cleaner to remove residues and then continue the repair
process. We used a black light inspection step (sometimes with a Mantis
Macroscope) to check connectors & the board for residue. Our customers,
also military, expected to see a uniform, "like new" conformal coating on
the repaired assemblies.
I think Humiseal might have come out with a gel version of that stripper -
you might check @ http://www.humiseal.com And yeah, Graham is the man when
it comes to conformal coating.
Hans
Integrity First - Service Before Self - Excellence in All We Do
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hans M. Hinners
Electronics Engineer
Warner Robins - Air Logistics Center (WR-ALC/LUGE)
226 Cochran Street
Robins AFB GA 31098-1622
mailto:[log in to unmask]
Com: (478) 926 - 5224
Fax: (478) 926 - 4911
DSN Prefix: 468
-----Original Message-----
From: <Peter George Duncan> [mailto:[log in to unmask]]
Sent: Tuesday, January 08, 2002 9:53 PM
To: [log in to unmask]
Subject: [TN] Removal of Conformal Coating
Morning, All,
This is one for Graham really. I'm looking, please, for your valuable
assistance to determine the best methods, solvents and equipment for
completely stripping Humiseal 1B31 from Board Assemblies.
The boards are military avionics boards, the volume/qty that require
stripping is low, but they need to be cleaned well enough to avoid coating
residues contaminating connector pins and getting inside unsealed
components that weren't intended to be internally coated.
Can thinners/solvents be recycled or must they be disposed of once the
coating reaches a certain concentration?
At what concentration level does the coating in the solvent cause as much
contamination as it removes?
How is it measured?
I haven't had to strip boards for a while, and when I did, the only
facility we had were three small tanks of humiseal thinner to soak/strip,
wash and final rinse the boards of coating, then doing a DI water wash on
them. The first tank was emptied and cleaned quite ofen, the wash tank then
became the strip tank, the rinse tank became the wash tank and the cleaned
out strip tank then became the rinse tank. I'm hoping there is something a
little more sophisticated now that doesn't involve soaking the boards, as
this method allows a lovely thin coating of humiseal to get into every nook
and cranny there is, and it was impossible to prevent it getting where you
didn't want it.
Does anyone have a set-up they can recommend and send me details about?
Many TIA's
Peter Duncan
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