Stripper 1063 is the recommended stripper for 1A33. It will remove
cured 1A33 in about 1-2 hours depending on factors such as thickness,
age and agitation (spray under immersion is good).
The stripper is quite basic, so I would recommend a thorough rinse in a
mildly polar solvent such as an IPA/water mixture to remove any
residues.
As long as the board is not left immersed for too long in stripper 1063
it will be fairly selective and leave the inks, resist and components
alone. However, I have seen corrosion of unusual hybrid alloy
connectors.
Leave your board in overnight and you might have more problems. Leave
it in over the weekend and ...... My advice is to keep an eye on the
process and develop a tight process spec for your operators.
HumiSeal Tech Support team are normally pretty helpful. It might be
worth talking it through with them. ([log in to unmask])
Hope this gives you something to work with.
Regards,
Phil Kinner
Chief Chemist
Concoat Ltd
2C Albany Park, Frimley Road,
Camberley, Surrey, GU16 7PH
Tel: +44 (0) 1276 691100
Fax: +44 (0) 1276 691227
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carroll, George
Sent: 03 October 2001 15:58
To: [log in to unmask]
Subject: Re: [TN] Seeking Conformal Coating (Type UR) Removal Process by
S olvent Dipping
Les,
Removing 1A33 after it has cured for over a week or two is indeed
difficult.
Per Mr. Caswell's response, most solvents that will remove the cured
coating
are likely to attack any other markings or coatings, too. I have found
that
tetrahydrofuran will remove the coating. My employment of the solvent
is
for removal of splashes and splatters after coating and drying of 1A33
through a conveyorized oven. In such an application it is almost
instantaneous (we use a cotton swab). It is much slower (like minutes
to
hours) on cured 1A33. I have never had to remove the coating from an
entire
assembly and don't know what prolonged to exposure to tetrahydrofuran
would
do to inks, soldermask or components. THF is slightly more volatile
than
isopropyl alcohol and I believe the NFPA ratings are about the same. It
would have to be kept in a closed vessel for the period of time required
to
soften or dissolve the coating. Be sure to employ good ventilation.
I have also used Kyzen 4402 to remove cured 1A33 from aluminum carriers.
At
room temp it requires about a day's soak and gentle brushing. At
elevated
(120-140F) it takes much less time, but requires ventilation. I would
suspect that while the Kyzen will remove the polyurethane with no attack
to
metals or plastic, the markings and soldermask might suffer. I haven't
tried this, myself, on populated assemblies.
George Carroll
[log in to unmask] <mailto:[log in to unmask]>
-----Original Message-----
From: Bogert [mailto:[log in to unmask]]
Sent: Tuesday, October 02, 2001 5:25 PM
To: [log in to unmask]
Subject: [TN] Seeking Conformal Coating (Type UR) Removal Process by
Solvent
Dipping
10/2/2001
Folks, I am seeking technical help on the pros/cons of removing Humiseal
Type 1A33 conformal coating (MIL Spec Type UR) using Humiseal 1063
Stripper
Solvent, or any other solvent that can remove the coating by dipping.
We
are returning boards from the field for a significant amount of rework
where
removal of coating by conventional means such as by soldering iron or
spot
application of solvents is not practical. The boards are FR4 base
material
(0.063 to 0.125 inch thick) with all parts being plated-thru-hole
military
specification parts. There are parts such as connectors and numerous
Integrated Circuit sockets where the stripper material could get into.
There
are also a significant number of teflon insulated stranded wire jumpers
that
are fastened to the board using RTV covered over with conformal coating.
The
OEM plans on dipping the complete board in a pan of Humiseal 1063 liquid
and
leaving it sit till the coating is dissolved. Cleaning will then be
done
using alcohol with DI water applied manually followed by automatic
cleaning
via in-line cleaner using solvent and DI water. Omega Meter type ionic
test
will then be done on sample basis to verify the ionic contamination has
been
removed (Humiseal 1063 stripper is highly conductive).
Has anyone out there removed conformal coating using Humiseal 1063
stripper
or other solvent dipping process. If so, please advise if you found the
process technically acceptable, and please provide specific process
details,
including the post cleaning method used. I would appreciate an answer
as
soon as possible.Thanks.
I can be reached at following contact:
Les Bogert
Bechtel Plant Machinery Inc.
412-829-8489
[log in to unmask] <mailto:[log in to unmask]>
FAX 412-825-8997
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