Waterproofing FPV Drone Electronics – Silicone Conformal Coating Tutorial

Waterproofing is essential to prolong the life of electronics in an FPV drone, and conformal coating is the most common method to achieve this. By protecting your components from moisture and chemical damage, you can ensure your drone can handle flying in extreme conditions.

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What is Conformal Coating?

Conformal coating is a thin, protective film that adheres to the contours of a printed circuit board (PCB). This coating creates a layer of insulation on the components and solder joints on the PCB, preventing potential electrical shorts.

Why Conformal Coat?

The goal of conformal coating a quad is to make it water resistant.

Even if you don’t plan to fly your drone over water or in rainy or snowy conditions, waterproofing your drone electronics is still beneficial. Conformal coating serves as a preventive measure against humidity and moisture from wet grass or leaves that might come in contact with the drone during landing or crashing. By protecting against these potential hazards, conformal coating helps prevent electrical shorts on exposed solder joints and prolongs the life of your drone’s electronics.

Types of Waterproofing

There are two popular solutions for waterproofing drone electronics: silicone and acrylic.

The primary advantage of acrylic coating is its easy removability. You can quickly burn through the coating with a soldering iron. However, the lack of durability is also its downside, because many components in a quadcopter, such as video transmitters, can generate substantial heat which might be enough to melt through acrylic coating.

Therefore silicone coating is the preferred choice for quadcopters or RC models in general, as it can withstand higher temperatures than acrylic. It takes more heat to melt it, but usually a soldering iron is hot enough to burn through it.

Where to Buy Silicone Conformal Coating?

I recommend using MG Chemicals Silicone Conformal Coating for waterproofing your FPV drone electronics. Although there are other alternatives, this product has proven its effectiveness and is considered the gold standard in the hobby.

You can purchase MG Chemicals Silicone Conformal Coating 422C on Amazon: https://amzn.to/3nkSWyb. Note that the label on the new version has been updated.

There are two versions available: one without UV indicator and the other with the indicator. The one with UV indicator fluoresces under UV light, making it extremely convenient for verifying complete coverage of the coating. This feature is highly recommended!

To verify the coating coverage, you can purchase an inexpensive UV light torch on Amazon: https://amzn.to/3vbOR2b.

The left board is NOT conformal coated, while the right board is coated – the glow under UV light indicates coverage.

When it comes to conformal coating for FPV drone electronics, it doesn’t take much. A 55ml bottle, available on Amazon for around US$20, should be enough for 50-100 quads and will last for years for an average pilot. The bottle comes with a nail polish-type brush attached to the cap for easy application.

Avoid the spray version, as it can get on components you don’t want to coat, such as connectors and buttons, which may cause them to malfunction. The spray also makes it difficult to achieve even coverage due to the lack of precision. Applying the coating with a brush is the best method.

Lastly, I recommend getting some isopropyl alcohol (rubbing alcohol) for cleaning your electronics before applying the coating and for removing the coating if necessary.

• Amazon: https://amzn.to/3gBL6yW

Preparation

It’s best to apply conformal coating on a quad you have already built, as the coating on solder pads can make soldering more difficult later. If you plan to waterproof a new quad, finish building it first and test-fly it to ensure all components are functioning correctly. Only then should you apply the conformal coating. Remember to reapply the coating on any solder joint if you redo the soldering on the quad.

For older quads, consider removing any tapes and heat shrinks covering the PCBs. Clean the electronics thoroughly to remove any dirt before applying conformal coating. An old toothbrush and isopropyl alcohol work well for this.

Applying Silicone Conformal Coating on PCB

Warning: Conformal coating can be a carcinogen, so avoid inhaling its fumes and ensure good ventilation when applying it.

When applying silicone conformal coating to your PCB, focus on covering exposed metal surfaces, particularly microchip pins, solder pads, solder joints, and any areas that might conduct electricity when wet. However, be cautious not to cover certain componetns, such as:

• Flight controller: boot button, USB port, barometer
• FPV camera: image sensor
• VTX: channel button
• RX: bind button

Apply the conformal coating like nail polish, brushing it on evenly to create a shiny, protective layer.

To check for complete coverage, use a UV torch. The coating contains a UV tracer that fluoresces when exposed to UV light, making it easy to see where it’s applied and if any areas need additional coating. Ensure the coated areas have a consistent, even glow.

Allow the conformal coating to dry for at least 30 minutes, but consider letting it dry overnight just to be safe before flying your drone. Typically, one to two coat layers is sufficient, but if you feel more coverage is needed or if you missed some spots, you can apply another coat for better protection.

How to Remove Silicone Coating?

If you accidentally covered solder pads or need to remove silicone conformal coating for any reason, you can use isopropyl alcohol and a brush (or cotton swap). The coating can also be burnt away with a hot soldering iron.

Some flight controllers (FC) and electronic speed controllers (ESC) come pre-coated with silicone. However, the spray coating may be uneven and miss certain spots.

To remove the coating:

1. Take a cotton bud and dip it in isopropyl alcohol.
2. Gently rub the alcohol-soaked cotton bud on the PCB where you want to remove the coating.
3. It should only take a few rubs to remove a thin layer of coating.

If you need to remove all the coating on a PCB, follow these steps:

1. Submerge the entire board in isopropyl alcohol.
2. Gently scrub the board with a soft toothbrush to dissolve the coating.
3. Allow the board to dry completely before using it again.

Pro Tips

Remember, It’s Not Fully Waterproof: Areas like plugs and buttons will still be susceptible to water.

To prevent damage to connectors, plug in all connectors before applying the coating. This ensures that the coating doesn’t ruin the contact inside the header/connector.

Keep in mind that silicone coating can be burnt away with a soldering iron. If you re-solder something, remember to reapply the conformal coating to the reworked area.

To fill small gaps, such as those between capacitors and resistors, try blowing the coating with compressed air (but not too close, or you’ll make a mess).

Preventing the Cap from Getting Stuck

Before closing the conformal coating bottle, clean the rim with a paper towel to remove any residue. The silicone coating acts like glue, and the cap can get stuck if there’s coating left on the rim.

If you can’t remove the cap, try these tips:

1. Gently heat the cap with a hair dryer or heat gun (on low heat so it doesn’t melt the plastic).
2. Tap the edge of the cap with a butter knife or against a bench to break the hardened coating around the edge.

Flying FPV Drone in the Rain

Remember, while flying an FPV drone in the rain can be an exciting challenge, it’s not something to take lightly. Always ensure you’ve taken all necessary precautions before attempting it. Apart from conformal coating your drone completely, there are a few other tips you can follow if you decide to fly in the rain.

• Visibility Problems: Be aware of potential vision issues due to water droplets on the camera lens or goggles fogging up.
• Thrust Reduction: Rain can decrease the lift produced by your propellers, you may need to use greater throttle than usual. You may want to consider using larger or higher pitch propellers.
• Transmission and Signal Loss: Keep in mind that the rain can cause signal loss or interference, affecting your video feed and control signals. Try to stay as close as possible to the drone to mitigate these issues.
• Control Difficulties: Be prepared for the possibility of harder control mid-flight due to strong wind gusts.
• Post-Flight Maintenance: After flying, it’s crucial to dry off your drone as soon as possible. Leaving it wet could cause corrosion over time.

What to Do If You Crash Into Water?

If your drone crashes into water, follow these steps:

1. Remove the drone from the water ASAP, and immediately disconnect the battery.
2. Rinse the drone with distilled water to remove minerals. Brushing with isopropyl alcohol is even better (NOT the motors just the electronics).
3. Allow the drone to dry completely. Using rice is not practical; instead, use a fan and let it dry for at least a day.

Conclusion

Waterproofing your FPV drone electronics with silicone conformal coating is essential for extending their lifespan and protecting them from moisture-related damage.

While conformal coating provides a level of water resistance, it’s important to remember that it’s not a guarantee against water damage. Always exercise caution when flying near water, and maintain your equipment properly for the best results.

By following the tips and procedures outlined in this tutorial, you can ensure your drone stays functional and ready for your next adventure. Happy flying.

Edit History

• Feb 2019 – tutorial created
• May 2023 – updated product links, added a few more pictures for instructions