Carl,
We had a problem years ago with Molex/Amp tin-plated power connectors (0.156" spacing). We traced the problem to corrosion (we could see the discoloration on the pins caused by the humid enviroment + airborne contaminants). We contacted Molex who recommended Nye Lubricants Nyogel 760G connector lubricant.
At the time I happened to be visiting Henning Leidecker and Jay Brusse at NASA Goddard Space Flight Center so asked them for advice. I was advised to read the following paper.
http://www.agingaircraftconference.org/all_files/20/20c/123_doc.pdf
That convinced us we were on the right track (we had been concerned it was a circuit design or component problem as the falures were random).
We sent the client a tube of 760G which he applied to over 200 of our units in 2007. The problem (intermittant power failure) vanished. www.nyelubricants.com We now apply 760G to all our tin-plated connectors. Also some gold plated connectors (RJ-45 type) as we found in some environments (like sewage treatment plants) the atmosphere quickly finds and corrodes the tiny pinholes in the gold flash coating. Unless the mfg plates a very thick gold coating, you can expect such imperfections to corrode. The result is a greenish tarnish which is an insulator. I have several HP calculators that used to be intermittant (battery contacts) until I took a q-tip and applied 760G on them. Also several flashlights and the trailer hitch on my Volvo wagon.
Regards,
Bob Landman
H&L Instruments, LLC
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl VanWormer
Sent: Monday, August 23, 2010 1:53 PM
To: [log in to unmask]
Subject: [TN] humid environments and long term reliability
We are considering conformal coating our boards that will go into a chassis that may be an occasional high humidity environment. I have been told that the humidity (and water) is "slowed down" by the conformal coating, and that good cleaning before the conformal coating is essential for reliability. Assuming we have done all we can do for the PC board assembly, my worry goes to the next level; the cables that connect between boards and also to the valves, relays, and sensors. Is it worth considering messing up the system with silicone grease smeared on all of the 2-pin, 5-pin, and 50 pin (IDC) plugs and sockets? I know some of the cute little phone-wire crimp-on IDC button connectors are filled with a dielectric grease, so it must have some value. And what about the IDC connector, with its pins just piercing the ribbon cable .
. . Is there a long term reliability problem there, too?
I'm looking for "fatherly guidance" on making a system that won't ever need a field service call.
Thanks for tolerating my paranoia,
Carl
Carl Van Wormer, P.E., AE7GD
Senior Hardware Engineer
Cipher Systems
1800 NW 169th Place, Suite B-100
Beaverton, OR 97006
Cipher Systems (503) 617-7447 x 5163
Direct Line (503) 425-5163
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