Electronics in quadcopter can last longer if you make it waterproof, the easiest way is Conformal coating. It helps prevent components from moisture and chemical damage when flying in extreme environments.
Conformal coating is basically a thin film which conforms to the contours of a PCB to protect the components and solder joints on it.
You don’t actually have to fly in the rain or snow to Conformal coat your electronics. Many pilots use Conformal coating as a good practice to protect the quad from humidity and wet grass/leaves that can cause water induced electrical short on exposed solder joints. It will even increase the chance of survival if you crash your quad in the water.
There are two popular solutions to waterproof drone electronics: silicone and acrylic.
The main advantage with Acrylic is that it’s easily removable. You can burn through the coating simply with your solder iron almost like it’s not there.
However, for quadcopters or RC models in general, silicone is better as it can handle heat better than acrylic. Many components in a quadcopter can get very hot, for example, the video transmitters, acrylic coating would simply melt and burn away.
I use MG Chemical Silicone Modified Conformal Coating, you can get them from:
These exist in two versions, the older version, and the newer “modified version”. They are basically the same stuff, but the “modified version” fluoresce under UV light (ultra-violet, aka black light). It makes it very handy to verify the full coverage of the coating, strongly recommended!
Its available on Amazon around US$20 for a 55ml bottle, which should last years for an ordinary pilot. It has a nail polish type brush attached to the lid for easy application.
Avoid the spray version because it will get everywhere you don’t want it to be. For example, your USB connector or bootloader button, and they might stop working. And it’s difficult to apply it evenly like you can with a brush.
Don’t forget to grab a cheap UV light torch too, these are cheap:
Finally, It’s optional, but I recommend getting some isopropyl alcohol (rubbing alcohol). It’s for cleaning your electronics before coating, and it’s useful for removing the coating as well.
It’s best to apply Conformal coating on an existing quad, because getting the stuff on solder pads will make soldering much harder. If you want to do this on a new quad, you should first finish building the quad and fly it to make sure all components are working properly.
If you are doing this on an existing quad, then you will want to remove all the tapes and heatshrinks that are covering any PCB. Make sure to clean the electronics to remove any dirt before applying the Conformal coating. I use a toothbrush and isopropyl alcohol for that.
Warning: Do not sniff the stuff as it is carcinogen! It’s important have good ventilation when applying it.
Brush it on like nail varnish. If you are unfamiliar with the procedure, ask your sister :-p
It takes about half an hour to dry, though I recommend leaving it to dry overnight. Usually one layer is enough, but if you don’t think you have applied enough or missed some spots, feel free to repeat for another coat for better result.
Use a blacklight (UV torch) to see if you missed anywhere.
What areas to avoid:
- flight controller: boot button, USB Port
- FPV camera: sensor
- VTX: channel button
- RX: bind button
Say if I covered the solder pads by mistake and I want to remove it, the best way is to use Isopropyl alcohol. It can also be burnt away with a soldering iron, but I don’t recommend it. Not only It takes a while, you can also overheat the copper pad and damage it.
Just take a cotton bud, dip it in alcohol, and rub it on the PCB where you want the coating to be removed.
It should only take a few rubs to remove a thin layer of coating.
If you want to remove every bit of coating on a PCB, you will have to dip the whole board in alcohol, the coating will dissolve, and finally let it dry completely.
Best to connect all the plugs before applying coating. This will ensure sure it doesn’t ruin the contact inside the header/plug.
As mentioned, Silicone coating can be burnt away by soldering iron. Therefore whenever you re-soldered something, you should apply Conformal coating again to the area.
You can try filling the small gaps, e.g. between capacitors and resistors, by blowing the coating with compressed air (not too close or you can make a mess).
It’s important to clean the rim of the bottle well with paper towel before putting the cap back on after use. This coating works just like glue and you might get the top stuck if you leave it on the rim.
Here are some ideas what to do when you can’t get the top off:
- Slightly heat up the cap with a hairdyer or heat gun (don’t melt the plastic though!)
- Smack the edge of the top with a butter knife or against the bench, all around the edge to break the hardened coating
This is a rebranded product.
Someone found an existing product and though it’s great for drone uses. So he bought a big amount of this and sell in smaller quantity, which would otherwise be too much for ordinary users to buy.
You can use UV light to see where it’s been applied on. You should put the cap on tightly, because this stuff evaporates very quickly!
Rumour has it that it is rebranded 3M novec 1700, or Novec 2700 series which has the uv detectable dye in it. I am not sure. I haven’t tried this either to verify the effectiveness.
You can get them on Amazon: https://amzn.to/2sAM6cl