Encapsulating to prevent condensation

AJ-9000

I have an outdoor project that involves the use of a BS-1 stamp, what worries me is because I know it only takes one drop of condensation on it to shut it down would encapsulating it along with the other circuitry in epoxy·be a good idea·? The external connections (non TTL level) would be made by soldering magnetic wire to a terminal strip that is also embedded in epoxy except for the terminal connections points. Note the three serial port wires would·be wired to·a screw down waterproof type plug.

Post Edited (AJ-9000) : 2/2/2008 9:05:46 PM GMT

Franklin

OK, that's do-able. I wouldn't use 'magnetic' wire but regular copper wire. I would also look into conformal coatings as they are flexible and will move with the changes due to temperature.

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- Stephen

Beau Schwabe

AJ-9000,
·
Careful, some epoxies will soften the rubber insulation on the wire.· If you meant enameled copper wire instead of "magnetic wire", that would probably be ok if it exited the epoxy’d circuit as long as it was thick enough to adequately handle the power requirements of your circuit.
·
If your epoxy requires a promoter,·lean towards the smallest amount of promoter required... if the epoxy sets off too quickly, it can damage your circuit components by excessive heat and/or create bubbles in the epoxy causing stress on the components as it hardens.
·

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Forrest

Conformal coating is what's commonly used in the industry. Typically you would spray 3 coats from different angles to get maximum coverage. There are different types of conformal coating and for low to medium volume production, you can buy it in aerosol cans. Urethane has good resistance against water, oil and solvents and if you need to repair the board, you can burn thru the coating with a soldering iron. There's a lot of good info here www.humiseal.com/. Where wires enter/exit the enclosure, you can use silicone caulk - the type used to make aquariums.

Phil Pilgrim (PhiPi)

I'll second the conformal coating recommendation. Military electronics and the better-grade marine devices all use it. Just be sure to mask off anything you don't want coated, and be generous with the coats themselves, spraying from several different directions. I use Fine-L-Kote AR, which is a hard-drying acrylic. There are many different varieties to choose from, though. Also, if you plan to order something like this, allow enough time for ground shipping: it's against regulations to ship it by air.

-Phil

Tracy Allen

Wax is also an effective option, and you can melt it off later. Or enclose the electronics in a wax-sealed canning jar.

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Tracy Allen
www.emesystems.com

deno

I have several Stamps running in the field and I "slide" the whole circuit board into the proper size diameter PVC pipe.· The ends of the approprate length of pipe are covered with the right size PVC cap.· One cap is glued on with PVC cement.· The other end with the hole for wires to come out is slipped over the end of the pipe, but not glued.· I use black tape to seal this end cap, and some "shoe goo" to seal the wires comming out of the hole.· This way, I can get back inside if I have to.· I use the euro style of terminal strip on the PCB for wire connections.· So If I need to get inside for "something", I cut the wires at the exit hole, undo the black tape, and pull the device out.· Then reassamble, attach the newly stripped wires back to the euro strip and reseal.

BTW, shoe goo or shoe goop is great stuff for waterproofing.· Much, much better then clear silicon.· Use it to hold large or heavy components to the PCB.· A small dab on wires going into headers will act as strain relief.· Absolutely great stuff...good for putting the soles back on yourf shoes...



Deno

Phil Pilgrim (PhiPi)

Since the subject of silicone has come up, it's necessary to throw out a warning to those who might be tempted: There are several kinds of silicone caulks and encapsulants. The two-part RT type that AJ-9000 mentions above is designed for use with electronics. But some single-part silicone sealants, such as tub and window caulk, cure with acetic acid and should not be allowed near electronics. Detecting this type of silicone is usually pretty easy, since it smells like vinegar. Don't use it!

-Phil