How Do I Protect DIY Electronics from the Environment?
I'm looking to protect a piece of electronics that will be put in the Freezer and Outdoors. I've looked into Conformal Coating to protect the pcbs from Condensation. Is this a good solution?
However, if you have an RF component and/or RF circuity in your PCB, you should be careful with conformal coating. As the frequency goes up and impedance requirements gets tighter, conformal coating becomes harder and harder to use, because it alters the RF circuit behavior. Also, obviously, you should not be coating certain sensors (pressure sensors, humidity sensors, etc).
Your next line of defense is your enclosure. Ideally, all your connectors should be IP67 or IP68 rated, and you should place your PCBs in an enclosure which is itself IP67/IP68 rated. This is usually achieved by using a gasket and designing the enclosure with a proper gasket opening.
If your device is going to be exposed to sunlight, you should make sure that any active IC in your system will not exceed its operating temperature. Metal enclosures exposed to sunlight will heat up considerably. You may want to think about a cooling solution, based on your power dissipation (enclosure with fins, etc).
Edit: Looks like you're aiming for an actual product release. There's no substitute for potting your circuit inside its enclosure. I'd look for a silicone based solution as you're aiming for large temperature swings.
EDIT: Silicone based compounds can poison many of your sensors! Use epoxy based potting compounds. Again, I would call the manufacturer of the sensor for guidance.
If you need conformal coating on your PCB, most sensor manufacturers will recommend you to cover the top of the sensor with some material (for example, Kapton tape), apply conformal coating to the PCB, and then remove the tape.
I've had good results with simple plastic cases, as long as a few rules are followed:
- The case must have a gasket on its cover
- Any openings must be on the bottom of the case (including antennae!)
- Cable glands or waterproof connectors must be used on all openings
- All cables must have a little slack, so they hang below the case and come straight up
- Put a couple of dissecant bags inside the box
I've been using this for various DIY outdoor projects for years, like putting mikrotik routerboards, raspberry pis, arduinos, etc. outdoors.
Water will accumulate in all openings not on the bottom of the case, and air pressure changes will cause the box to "suck" this water in, no matter how tightly sealed that cable gland is. That's why the openings should all be at the bottom.
Just my 2 cents.
(Disclaimer: I am a moderator there)
Condensation happens when moist air hits a cool surface, how much power is your circuit consuming? You may not have a problem.
I have designed a number of telephony products (e.g. T1 repeaters) for use in outdoor environments, we never coated the circuit boards.
Along the lines of "do things that don't scale," household products such as Household Goop (aka Shoe Goo), silicone sealant, etc., work pretty well.
If you have one or two components that can't be coated, you can leave them off the board and solder them by hand after coating.