In this instructable I will show you how to waterproof a circuit board. I will be waterproofing a cheap RC receiver from HobbyKing, but the same method can be applied to many different boards. I have used this technique for a few years now, and never had issues with it.
This will void warranty! Do at your'e own risk. This method will not protect connectors from water, so do not use high voltage boards. You can use marine grease to protect connectors or silicone sealant which can peel off.
Step 1: Parts.
You will need:
- A board that you want to waterproof.
- Clear silicon sealant (optional, used if you have buttons)
- Tools to take the receiver apart
- ESD strap (optional)
- Gold connectors (optional)
- Blu tack
- Balloon (for switches)
- Thermal conductive silicone pad (for hot parts)
- Aluminium heat sync (hot parts)
The epoxy that you choose for this project is very important. Epoxy can sometime have metal aditives making it bond better to metal. However this can make the epoxy conductive, and fry the board. Your'e best bet for getting epoxy with no metal additives to get a clear one. I used Selleys araldite ultra clear. This not only lets me still see led's on the board, but it also means that there is less chance of the epoxy conducting.
Step 2: Disassemble the Board.
Here you need to expose the bare board. Different manufactures have their boards held down in different ways. My receiver was held together by 2 small screws on the back, which is typical of most receivers. Some may use clips or be glued together. Preferably you want a new board, because grime and build up on the board will affect how well the epoxy bonds to the board. Try to handle the board only by the edges to prevent ESD discharges and oil from your fingers on the board.
Step 3: Gold Connectors.
If you are planning on having the board exposed regularly to water, you might want to replace the connectors and pins with gold. This is because gold does not react as fast as copper connectors, so will handle things like water better without corroding.
To replace the connectors you will need to remove the old ones with some solder wick or a solder sucker, and replace with gold plated ones.
Step 4: Cover Up Any Part You Don't Want to Be Glued
Cover up any connectors, pins, switches or buttons that you will need to use with blutack.
If there are any surface mount switches, you can glue a piece of balloon over it and epoxy around it. This will still let you operate the switch through the balloon.
Some parts such as power transistors, or amplifiers may become hot, and sealing them with epoxy will insulate them. This will mean that they are less affective at dissipating heat, shortening the components life span and sometimes causing death!
For parts that only get hot you can take a aluminium heat sync and attach it to the component using a thermal conductive silicone pad. the pad can be purchased for $4 on ebay. Use a small clamp or bulldog clips to hold it in place for the next step.
Thermally conductive epoxy can also be used. Just make sure that it non-electrically conductive. Anything that is designed to be directly applied to a PCB should be fine.
Step 5: Mix
Mix a generous amount of epoxy that you are using as per directions. You want enough to give a thick coating over the entire board. You will need to work fast as the epoxy that I used set in about 5mins. Avoid any place that you do not want to get sealed up. For any parts that get warm, make sure that the layer of epoxy is as thin as possible. Also epoxy to the edges of any heat syncs, but not over them.
Hang the board up to dry afterwards. I used the antenna cable to hand mine, but you could but in a plug to hold it from.
After dry, inspect the board for any places you might have missed. You might need to do another thin coar to cover up any places.
Step 6: Silicone.
Anything like buttons mounted on the board will still be able to be used under a layer of silicone. I put a blob of silicon over the button so it can still be used, without gettaing any water in it.
I would also apply silicon around any mounting paints or connectors. Because these places are likely to crack the epoxy. By putting a extra flexible layer you insure that the cracks will not allow water to reach the board.
Step 7: Done!
Re-assemble your'e board after dry. And test. Make sure that all the buttons and switches have not been accidental sealed up.
You can also spear marine grease into any connectors. This is non conductive and it will prevent water from getting to the connectors.
Thanks for reading!