Some of the space application is very benign from environmental point of
view regarding conformal coat, particularly, if it is used in the
cabinet (almost as good as vacuum chamber). Outgas would be a key
issue. However, if it is used externally, that is another story. Can't
see circuit board being exposed to the external space environment.
Solar cell is another matter... They got special coating on them for
that reason (atomic oxygen, proton damage, etc.etc.)....Regarding
electronic assembly, temperature extream more of a concern than
conformal coat usually.
As for non-condensing, if you go to south Asia, you got water beeds
(with contamination) on the table during the Monsoon season, you will
need better coating than you used for north america product (few of
coating with hydrophobic surface treatment do not work well in that
environment. Change of surface tension occurred upon contaminating the
surface). You MUST understand what are you try to protect againest
before you change your conformal coat.
By the way, I do like urethane coating very much, if you can get them
coat under the module leads ;-).
My 2 cents.
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Newland, Scott
>Sent: Wednesday, December 18, 2002 7:57 AM
>To: [log in to unmask]
>Subject: Re: [TN] conformal coat survey
>
>
>We use exclusively use urethane and acrylic and have passed
>several military
>(MIL-STD-810) salt fog and humidity tests. Our products run
>the gambit from space hi rel to ground military to military
>avionics. We also have test results that show urethanes gave
>better electrical insulation compared to paralyne for very
>high impedance circuits.
>
>The big secret to passing these types of tests are: Clean PWBs
>(No residual solvents), good conformal coating, orienting the
>PWB so the moisture will not condense on them, providing
>adequate drain holes to let the condensed liquid out of the
>chassis, and to seal or move any cover chassis parting lines
>to prevent moisture from running on to the PWBs.
>
>Scott Newland
>Harris GSCD
>321 727 6472
>Pager 321 690 4131
>E-Mail [log in to unmask]
>For a brain teaser try:
>http://pao.gsfc.nasa.gov/science.html
>
>
> -----Original Message-----
>From: WEEKES, MICHAEL HS-SNS [mailto:[log in to unmask]]
>Sent: Tuesday, December 17, 2002 4:07 PM
>Subject: conformal coat survey
>
>Can participants reply with the conformal coating they use,
>why they think it's the best and why alternatives did not work
>out? PS: does anyone use anything besides paralyne /
>paraxylene in order to pass salt fog or humidity tests?
>Choices: silicone, paralyne, acrylic, epoxy, urethane. To be
>honest, we'd love to ensure a rugged coating without the
>process horror and non-reworkability of vapor deposition.
>Please include whether your product operates in an aerospace,
>MIL, telecom, automotive, industrial, agricultural,
>off-highway, etc. environment
>
>thanks,
>
>Mike Weekes
>[log in to unmask]
>
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