Hi Steve:
Micro blasting will not damage the components next to it. You
can remove the coating off the solder joints only with no problems at
all. If you still have any concerns, all you have to do is to tape mask
adjacent components. I am partial to CCRCo media due to its cleanliness
and ESD safety. Nozzles to remove coatings come in all different sizes.
For this board, use a small tip. The process is fast and inexpensive.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, April 20, 2006 5:18 PM
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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