You are correct. I used the wrong term. I should have said the solder resist
coating. Is this coating included in the temperature ratings?
Richard Woods
----------
From: mike harris [SMTP:tecco...@i-cafe.net]
Sent: Wednesday, October 11, 2000 11:25 AM
To: Peter Tarver; emc-p...@ieee.org
Subject: Re: PCB temp ratings, etc...
Hi Richard & Peter,
Richard, I wonder if you are calling the solder resist coating as
conformal coating?
If so, I expect that the resist coating is ignored for any PWB
ratings and insulation properties.
My understanding is that conformal coating is a completely other
issue from resist coating.
Mike Harris/Teccom
-----Original Message-----
From: Peter Tarver < ptar...@nortelnetworks.com
<mailto:ptar...@nortelnetworks.com> >
To: emc-p...@ieee.org <mailto:emc-p...@ieee.org> <
emc-p...@ieee.org <mailto:emc-p...@ieee.org> >
Date: Wednesday, October 11, 2000 8:31 AM
Subject: RE: PCB temp ratings, etc...
You're welcome, Richard.
MOTs are developed for a copper clad industrial laminate and
verified by certain tests on a finished PWB. Conformal coatings are not a
normal part of this process, though I suppose a board house could ask for
such considerations to be made for a selection of coatings.
According to the Guide Card information for UL's CCN QMJU2,
conformal coatings are evaluated for their dielectric properties and effects
on flammability of a finished board after "environmental, humidity and
thermal conditioning," but I don't remember the details of the test program.
I don't know if it matters whether the coating discolors, so long as it
successfully completes the test program, though, as an end-product
manufacturer, I'd be suspicious of just how good a material it was and talk
this over with the supplier and maybe do a few more tests, if the mandate
from my employer allowed for that. If the coating bubbled or adhesion to
the PWB surfaced failed, I'd say it was no good for the application.
Regards,
Peter L. Tarver, PE
ptar...@nortelnetworks.com
-----Original Message-----
From: wo...@sensormatic.com [ mailto:wo...@sensormatic.com
<mailto:wo...@sensormatic.com> ]
Sent: Wednesday, October 11, 2000 12:59 PM
Pete thanks for your reply. I have noticed that the
conformal coating on
some boards begins to discolor when subjected to continuous
high
temperatures. In some samples, the coating begins to darken,
bubble and
delaminate from the surface. Is the conformal coating
considered when
setting the rated MOT?
Richard Woods
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