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t3andy
11-03-2012, 02:14 AM
There are times the Teensy needs to venture outside in the cold, hazardous elements.
I believe the Freescale ARM microcontroller small IC pitch would be destroyed outside due to moisture and corrosion.

Questions:
1. Would you do conformal coating on the Teensy 3?

2. If yes, what would you charge for the "clear" coating on both sides?

In my application, I would have the "outside" I/O pins headers installed and would not care about anything not connected to the "interior" top/bottom pads.
The only two items - the reset tac switch and the USB connector would possibly need a special "liquid rubber" protection?
I realize the warranty on the Teensy would be void. The Teensy I/O header pins would need to be factroy re-checked and tested after the conformal coating.

3. If no, what do you recommend for a "clear" conformal coating on the Teensy?
(The chosen conformal coating would also need a "matching" conformal stripper solution.)

JBeale
11-03-2012, 03:52 AM
I don't have any experience with conformal coating, although I've heard that plain paraffin wax has been used in the past. The advantage there is you can clean it off easily with a dip in hot water (50 to 60 C). If your environment is humid enough to worry about corrosion, even the 0.1" pins might eventually have problems too, so you might be better off immersing your complete electronic assembly in the sealant, rather than just the Teensy.

You can also embed the part in hot-melt glue, which might not be very pretty, but could serve the purpose. It can be carved away with a knife or melted away with hot-air gun, but is usually difficult to completely remove.

pixelk
11-03-2012, 09:09 AM
I used some Jelt branded "Tropicoat" coating (ref 7361) before without any ill effect on arduino pro minis. It is sticky and verry liquid before it sets, so eather have all your I/O already soldered or protect them very well before spraying. It is transparent. It is not designed to be re-worked (or stripped) AFAIK.

TimO
11-03-2012, 06:23 PM
I would imagine it would be easy enough to add on yourself after assembly. The risk with applying it before using the Teensy for anything, would be that it could contaminate the pins, and make soldering them difficult, and it could get into the USB connector, and cause a poor connection to that (and indeed, you would need some way to protect that, which could be removed for programming, should you wish to be able to do that after the initial use).

I'd have thought using a water tight container (with appropriate sealing of any wiring in or out) would be more practical, and allow it to easily be reprogrammed in future.

Paul
11-04-2012, 01:49 AM
I also haven't used conformal coating. It was used on a couple products at a former employer many years ago, but I didn't get involved in that part. Having PJRC apply conformal coating probably wouldn't work out.

TimO's concerns are also my thoughts... it would be difficult to keep the USB connector in working condition. You'd almost certainly want to coat after the board is installed in whatever application you're using.

I recently did an outdoor project using Teensy 2.0 and other electronics. I put everything in a NEMA4 enclosure from Polycase.

http://www.polycase.com/surface-mount-wc-series

For the cables, we used fittings and flexible plastic hose. I don't have that info handy, but they worked well. I survived several days in rainy weather, without any sign of water inside (the lid is clear, so it's easy to see inside).

If you can use a case like that, it's probably far better than depending conformal coating and allowing the board to be exposed to moisture.

t3andy
11-04-2012, 01:45 AM
I will try to use this Urethane conformal coating and let you know how it works out.
Another alternative is to use a small AC low wattage heater in the enclosure to remove the enclosure of moisture.
http://www.mouser.com/ProductDetail/MG-Chemicals/4223-55ML/?qs=sGAEpiMZZMvJqaFk9BIiv6jhjM0Pk6Jz%2fTHEyhf6VXw% 3d

rbrockman
11-04-2012, 01:49 AM
On a recent product I used a conformal coating on the pcb's to protect them from the elements. I used products from Techspray - http://www.techspray.com/category-listproducts.php?cId=4, but I've also heard good things about coatings from MG Chemicals - http://www.mgchemicals.com/products/protective-coatings/conformal

There are acrylic, urethane, and silicon types of conformal coatings - each with particular characteristics best suited for varying applications.

The product I used went on clear and produced a nice shiny surface. I did mask off some connectors to ensure that it did not interfere with them before spraying.

slomobile
11-05-2012, 01:36 AM
As JBeale mentioned, hot glue works. I haven't performed formal tests, but I have "potted" a few teensy projects in hot glue with no ill effects noticed. In addition to corrosion protection, it provides strain relief for connected wires, some thermal mass, and a nifty optical diffusing effect which makes the onboard LED much more visible in a sea of connected wires. For the button, I waxed a plastic "pusher" rod that protruded through my case and encased it in hot glue too. The wax kept the glue from sticking to the rod but made the gap so close it was still water resistant. Removal is by mechanical means if possible at all.

t3andy
11-05-2012, 09:21 PM
The MG Chemical Urethane conformal coating that I was going to buy from Mouser, they wanted a minimum quantity of 5 which translates to about $50 and it has to be shipped UPS due to being a hazardous chemical.
I tried the super cheap "hot glue" on the Teensy outside controller and it seems to work. Only time will tell.

virtualdave
11-06-2012, 04:10 PM
Just a handy little pointer for hot glue...if you want to remove it, use rubbing/isopropyl alcohol. It doesn't dissolve the glue, but rather causes the glue to lose it's ability to stick to circuit boards, IC's, etc. Insulated wire is still a bit of a challenge, but other surfaces work great. Much easier than reheating. Just need a few drops gets the job done.

pixelk
11-06-2012, 07:25 PM
Thank you for the tip ! Re-heating is not always an option (like in plastic boxes).
While we're at it, any tip to apply it more cleanly ? I usually ave a big blob out of the gun then work with toothpicks to get the glue into the corners, but I get a lot of glue spagettis :/
It works, but it doesn't look very clean.

slomobile
11-08-2012, 01:41 AM
I work on a piece of glass or granite countertop. Put down layers of hot glue on the countertop, press the Teensy into it while still soft. Let it cool, then trim the excess square with a razor blade. The finished part with glue glue pops right off the surface by prying just a little.

t3andy
11-09-2012, 01:01 PM
@slomobile
Got picture?