UL Recognized Component Category QMRX2 covers parts and enclosures made
from polymeric materials that are electroplated, metal foiled, hot stamped,
painted, cathode sputtered or vacuum metalizzed.
This category approves the combination of the coating applicator, coating
thickness, plastic manufacturer and plastic material designation.
In order to make life easier when obtaining UL or other NRTL approvals, I
would recommend using coating applicators/plastics that have already been
approved under this category.
Regards
Joe Martin
EMC/Product Safety Engineer
Applied Biosystems
"Doug McKean"
<[email protected]> To: "EMC-PSTC Discussion
Group" <[email protected]>
Sent by: cc:
owner-emc-pstc@majordom Subject: Re: Spray-on
Conductive Coatings
o.ieee.org
01/11/02 03:02 PM
Please respond to "Doug
McKean"
"Darrell Locke" wrote:
>
> Dear Colleages,
>
> We have seen an issue lately with spray-on conductive coatings used
on the
> inside of electronic enclosures. The coating works great for EMC,
but there
> seems to be a problem with adhesion and tiny flakes of conductive
material
> getting in the electronics. I'm thinking that the spray-on type
materials
> should not be used at all. Has anyone else experienced this
problem?
Try to avoid it if you can. You're absolutely right about the problem
of flaking onto or getting into any energized electrical parts. Safety
will
be all over you about using it. And because of that, you'll have to
get:
1. a UL approval for plastic of the cover,
2. a UL approval for the plastic molder who's making the cover for
you,
3. a UL approval for the conductive coating,
4. a UL approval for the marriage of the coating with the plastic,
5. and a UL approval for the vendor applying the coating to the
cover.
All approvals have to be verified of course in black-and-white
for approval and for all subsequent factory inspections with
of course appropriate Certificates of Compliance handy as well.
As far as emi, it's sort of a once used thing. Don't use it on
a cover that will be repeatedly removed and replaced. It's
not meant to be disturbed to any extent once in place. And
do not use it as a primary ground either. And it's all dependent
upon the thickness of the layers for effectiveness. Oil based
coatings seem to have a higher ohms-per-square than the water
based coatings. You want to keep it down around less than
0.5 ohms.
Been there, done that, sorta don't want to do it again.
Other personal experience mileages may vary of course.
All strictly my own 2 cents worth of opinion.
- Doug McKean
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To cancel your subscription, send mail to:
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unsubscribe emc-pstc
For help, send mail to the list administrators:
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Dave Heald [email protected]
For policy questions, send mail to:
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All emc-pstc postings are archived and searchable on the web at:
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