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From: Robbie Hatley on 8 Jul 2010 18:26

Greetings, group. I've got a sticky issue here. I'm repairing a number of circuit
boards from a manufacturer who coats their boards after assembly with some
sort of plastic clear coat. (Polyurethane, maybe? Indoors it's clear and
colorless, but outdoors under skylight, it glows a pale blue.) It makes probing
and soldering/unsoldering quite difficult. What's the best way to remove it?

So far, I've tried:

91% isopropyl alcohol:
Loosens bond between coat and board, but doesn't dissolve coat.

Unknown solvent in unmarked 55-gallon drum (possibly toluene-based):
Dissolves coat, but very slowly, requiring a lot of scrubbing with a brush.
Noxious fumes.

CRC Letra-Motive Electric Parts Cleaner:
Dissolves coat, but slowly, requiring a lot of scrubbing with a brush.
Turns coat into a thick goo that mucks-up brush and is hard to rinse out.
Noxious fumes.

Are there better options?

--
Varnished,
Robbie Hatley
lonewolf [[at]] well [[dot]] com




From: William Sommerwerck on 8 Jul 2010 21:27
> Try acetone.

But with great caution. Acetone attacks a lot of plastics.


From: Sjouke Burry on 8 Jul 2010 23:09
William Sommerwerck wrote:
>> Try acetone.
>
> But with great caution. Acetone attacks a lot of plastics.
>
>
I would try MEK(Methyl-ethyl-keton) if you are still allowed
to use it. :)
From: Jeff Liebermann on 9 Jul 2010 01:13
On Thu, 8 Jul 2010 19:24:02 -0700, dplatt(a)radagast.org (Dave Platt)
wrote:

>Conformal coatings may be urethane, epoxy, acrylic, or silicone. I
>believe that the urethane types are the most common but I could well
>be wrong about taht.

I think acrylic is the most popular these days. If it's hard as a
rock and clear, it's acrylic. If it's soft and yellowish, it's
urathane. If it's hard and yellowish, it's epoxy.

Go unto thy local paint or hardware store and get some urethane and
epoxy paint remover. Use it sparingly as it will attack G10 and FR4
PCB material, which is epoxy and fiberglass. Don't dunk the board
into the stuff. Just paint some on the area where you're working and
wipe it off when the coating gets soft. The rest of the way, use a
scraper.

>The pale-blue glow you observed is probably a
>UV-fluorescent tracer dye, added to the liquid coating so that boards
>can be checked during manufacture to ensure that they're properly
>coated.

Yep. Get a UV lamp (black light) so you can see where the coating is
missing.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl(a)cruzio.com
# http://www.LearnByDestroying.com AE6KS
From: William Sommerwerck on 9 Jul 2010 18:24
> Confirmed. Coworker put a UV light on it, and it glows crazily. (The
> cuticles of all the fingers of my left hand also glow extremely brightly
> under UV; seems I now have a poisonous muck of plastic resins,
> toxic solvents, and radioactive isotopes embedded under my
> fingernails. Great. Sigh.)

Actually, you're mutating into a scorpion.


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