A very nice (but not cheap) method is laser ablation. I have done this to
remove soldermask off some pads on a very expensive board with very
expensive components and with great success.
This process also cuts a little into the FR4 around the pad, as one wants to
make sure the complete pad is bare and therefore one has to overscan the
area to be cleaned.
If you like you can contact me off-line to get more details.
Regards,
Ahne Oosterhof,
Fine Line Stencil / A-Laser, Inc.
Beaverton, OR
503-641-9428
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, 20 April, 2006 14:18
To: [log in to unmask]
Subject: [TN] Parylene Coating Removal...
Hi All!
I've always thought that when it comes to removing parylene coating, about
the only way you can remove it is with some sort of mechanical means, i.e.;
microabrasion, or scraping. Burning through it with a soldering iron when
trying to do rework it is very, very difficult...I've tried it...it doesn't
work well at all.
I was just told that a chemical that I haven't heard of before might work,
it's called THF, or Tetrahydrofuran. I was told that it won't dissolve the
coating, but will cause it to lift from the PCB where it can be brushed
away. Have any of you ever heard of this stuff? I'm not a chemist, and I'm
not about to use it until I learn more about it.
The issue that I have is with a little tiny assembly that has been built and
parylene coated with some bad programmable hall effect switches installed.
The board is so small, and there are other components installed really close
to where the coating has to be removed. I'm afraid of getting them
microblasted because I'm afraid of damaging the other components. See the
assembly at:
http://stevezeva.homestead.com/files/8001_assy_backside.JPG ...the small
components are 0402's, so that gives you a visual scale of how big the
assembly is...
I've got the information in to a company that I found that does laser
ablation to remove coatings to give us a quote, so I'm waiting on that.
But if that turns out to be really expensive, I was contemplating using the
THF as plan "B" (provided the stuff will work and it doesn't hurt anything
else on the assembly).
Kind regards,
-Steve Gregory-
Senior Production Engineer
OAI Electronics
East 12th Street
Tulsa, Oklahoma 74112
(918) 836-9077 Ext.-507
(918) 706-2779 CELL
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