I’m making a new device that I need to waterproof somewhat. The problem is that the board itself is going to be in a (sometimes) wet environment. What I had planned to do was epoxy over all of the chips and traces. The only catch is that I have to use a chip antenna for my RF signal, and I was wondering if you guys knew how much attenuation covering it with epoxy would give.
hard to know. I’d avoid it on the antenna and RF traces.
PC boards are often “conformally coated” in military applications. See:
You could try putting a lump of the cured epoxy in a microwave oven with a glass of water, and see if it gets warm. That will give you an indication of how lossy it is. Radio amateurs often test plastics this way
Leon
Put a thick layer of parafin wax over the board.An eighth of an inch at least. Then, coat with clear epoxy if necessary. The parafin will interact somewhat with trace capacitances, but alot less than other sealants. The best would be clear polyethylene melted into place. It can be purchased in 1/2" sticks at ski shops, and used in a high heat glue gun.Very chemically non reactive.
Ron
Several sprays / coatings are commercially available, with already specified loss factor and permittivity, for example:
http://www.loctite.com/int_henkel/locti … 7&layout=2
In order to keep the optimum range, you will probably need to relayout the antenna and characteristic impedance traces.
You probably already thought about the fact that even if the board is waterproof, the radio link will be disturbed by the water…
Good luck.