How to Waterproof Circuit Boards (epoxy Method).

Intro: How to Waterproof Circuit Boards (epoxy Method).

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:

1. A board that you want to waterproof.
2. Epoxy
3. Clear silicon sealant (optional, used if you have buttons)
4. Tools to take the receiver apart
5. ESD strap (optional)
6. Gold connectors (optional)
7. Blu tack
8. Balloon (for switches)
9. Thermal conductive silicone pad (for hot parts)
10. 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!

David97.

Comments

[TheVroum]

Hello :) !
At a point you suggest not to cover the heat sink. However, they are often connected to ground. If the water has no connection it is not a problem. But if, for instance, another heat sink from this board (or another for multiboard project) is connected to somehting else, you might end up with a short-circuit.
all the best

[yeskay]

I want to protection the components from desoldering and damage due to vibration and temperature. We are using in automotive application. Suggest me a solution.

[AA65]

i want to waterproof only the back part of the circuit which only has soldering can i just use araldite on the entire back side

[PeterR17]

Epoxy is better than air in heat conduction / heat capacity, so I'd not worry about extra heat build up from epoxy painting a circuit board.

[armorer243]

For boards that don't generate any heat to speak of, I have used hot glue. If you need to remove it, you can heat the board to soften the glue and scrape away the glue with a wood popsicle stick.

Good use of epoxy, I will have to try it!

[David97]

I have also seen wax used on nikko rc boards. I gave it a go but found that with temperature changes the wax would crack and flake off.

As for board that you need to remove it from, plasti-dip works well. I have also used silicone sealant over the entire thing. But it's not as durable.

I remember using the how glue method on a set of bike lights. It works well. I find that epoxy gives a more professional looking inish.

[nqtronix]

You should also cover any "moving" parts such as speaker, microphones or unsealed relays. For best heat conductivity try to keep the layer of epoxy as thin as possible or use special epoxy with a low thermal resistance.

Besides that it's a neat little trick which can be pretty handy. Nice work.

[David97]

Thanks. Will add this. As for heat, power transistors ect, I would add a aluminium heat sync or plate with a thermal pad. Then epoxy around it while it is clamped.

[amcp21]

Thank you! =)

[David97]

No problem. Let me know if there is anything you would like me to add.