Just to round this topic off. There is an alternate way to apply metal to
plastic. When this issue first came up back in the early 80's as the FCC
rules for computers was being implemented the scramble was on to find a
solution. Paint was one method. Impregnating the plastic with metal flakes
was another. It had its own set of problems such as high wear on the
injection molding tools, appearance of the plastic, and required thickness
of the plastic, and cost.
It seems to me that the paint has outlasted the impregnation
process, but either of these seem to be pretty limited these days. This is
just personnel observation but you can bet I tear a lot of equipment apart
just to see how others solve problems. Monitors seem to be the biggest user
of paint, and sometimes laptops. But it appears that mostly folks build sub
enclosures of metal and formed fingerstock that they attach to the insides
of the "pretty panels" of the enclosure.
Gary
-----Original Message-----
From: WOODS, RICHARD [SMTP:[email protected]]
Sent: Tuesday, April 13, 1999 11:54 AM
To: 'emc-pstc'
Subject: RE: Conductive Paint
When I worked for a major PC manufacturer we started out with
conductive
coatings on our laptops. Paint over spray was a problem that we had
to
address. Also, the coatings did not always touch at all points due
to bowing
of the plastics. We were also concerned with the long term effects
of
servicing on the conductivity. Many times on the OATS we had to
remove and
replace covers just to ensure we had good contact so we would
comply. It was
a pain.
We found a much cheaper way of conforming with EMC. Source
suppression. It
is possible to suppress the noise at the sources and eliminate a
metal
enclosure. One good source of knowledge in this area is Ken Keenan
(813)
544-2594. Other gurus are also available. Ken gave our designers a
two day
course specially designed for us. Once the designers finally learned
- some
took longer than others - that there are no short cuts in source
suppression, we finally got a compliant product out the door without
conductive paint.
Once last remark. Conductive coatings may soon be a thing of the
past in the
EU due to recycling requirements. Conductive coatings cause a big
problem in
that area. Check it out.
----------
From: JENKINS, JEFF [SMTP:[email protected]]
Sent: Tuesday, April 13, 1999 12:07 PM
To: 'emc-pstc'
Subject: Conductive Paint
Hello Group,
My company is proposing to use conductive paint on our
enclosures,
and I
would like your input as to the acceptability of this
vis-a-vis
protective
earth bonding of enclosure panels. I am interested in the
perspective of
both European and North American requirements.
This should be a generic question, but if it helps, here are
the
standards
we use:
EN 60950 / IEC 950 / UL 1950 / CSA 950
EN 50178
UL 1012
CSA C22.2 No. 107.1
Regards,
Jeff Jenkins
Senior Regulatory Compliance Engineer
Advanced Energy Industries, Inc.
Fort Collins, CO USA 80525
Opinions are my own and not necessarily shared by Advanced
Energy
Industries, Inc. or its affiliates.
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