Does anybody have suggestions for waterproofing electronics?
I know of the epoxy method, but is there something I can spray on and then forget about it?
I have used bath sealer in the past. It is not spray-on, but it is an alternative to epoxy.
Mike
How waterproff do it need to be ? Splash proof, or totally immersed under water ?
I don't think any spray on component would work, it would be difficult to get it everywhere, even under IC's and stuff like that.
maybe you could use a small plasitc enclosure that was sealed ?
For protection against moisture and spills I use Electrolube Silicone conformal coating (spray can).
Otherwise for full waterproofing there is a plastic which is used for coating tools' handles, usually it's yellow, one brand manufactures it under the name of plasti-dip( http://paint-and-supplies.hardwarestore.com/49-265-rubberized-plastic-coating.aspx ), I never used it on a board but it should work. Nothing beats the epoxy encapsulation. Also if your circuit has heatsinks, you should go for sealed box preferably a metallic box.
Any urethane conformal coating will do, try Techspray PN 2104-12S (Newark PN 10J6920). These conformal coatings contain a chemical that lights up under black light, so you can see where you need to add more to improve coverage.
Thankyou for the suggestions. I will look into all of the recommendations.
The electronics will be getting splashed by acidic chemical solutions, at least once per week or when the chemical container is refilled/emptied. Because of many issues, the electronics must be mounted on the container.
I've put a circuit board camera in a small tupperware-type plastic container (with leads coming out) and sealed the lot with aquarium sealant. it was then put on a swimmer's head and used loads of times without any problems despite being handled quite roughly at times.
Does anybody have suggestions for waterproofing electronics?
You might want to check out the avrfreaks forums--there was discussion of this topic on there late last year.
--Phil.
When you seal the board using silicone or acrylic bases, you seal in the moisture and any other ionic contaminates that happen to be on the board. This is one of those "gotcha's" that will bite you eventually.
So rule of thumb is,
make sure it's clean AND make sure it's dry.
When you seal the board using silicone or acrylic bases, you seal in the moisture and any other ionic contaminates that happen to be on the board. This is one of those "gotcha's" that will bite you eventually.
I wish I had said that before I quoted a part number :-[
Check with the conformal coating manufacturer about the specific chemicals it will be exposed to. They pay engineers to answer these questions from customers.
If you buy a liquid or aerosol conformal coat, it will come with instructions that you should follow as closely as you can. If it suggests a temperature cure, try to arrange one, but be aware that it is risky enough cooking food in some household ovens.
Be sure to mask any heatsink surfaces you want to use, and any connector pins. Says the guy who didnt.
All that said, I really think a conformal coat is what you want.
Acrylic is easier to apply than urethane. It's benefit is it is not chemical resistant so can be removed if needed. If you need chemical resistance choose the urethane or epoxy. Acrylic comes with the UV tracer the same as most other conformal coatings. Check and make sure the UV tracer is in there so you can verify the coating easily.
Degreasing is critical, Tech Spray and others have electronic compatible degreasers. Check the specifications of your parts and make sure what you use is compatible. No LCD I'm aware if can take this unless it's s specialty type.
Masking the board is critical I recommend masking tape or if you can get it humiseal tape http://www.humiseal.com/ they also make a variety of coatings none of which are available in small quantities. 
You can mask off plug in parts with the masking tape and just leave it on. It will allow you to remove it later to replace the part but you'll have a good hermetic seal otherwise. For far more robustness build the board with all soldered in parts.
Connectors are difficult because the conformal coating can and usually will wick up the bottom enough to interfere with connections. You'll need a steady hand an xacto knife to cut masking tape to fit. I've not found anything that works well and is cost effective. If you can afford it or have some electronic grade RTV it works well, the auto/hardware store stuff gives of acetic acid vapor and is not suitable.
Any component that is water sensitive such as LCD's come with their own problems. Since ones pre-sealed against moisture are outrageously pricey you can build an enclosure just for them and seal that. It's not hard, just tedious.
If you want this to work under water even for a short time you'll want a water tight enclosure rated for the max depth plus 25 percent. Conformal coating will enhance the devices reliability even though it will be enclosed.