Hello, I've been wondering if its possible to apply conformal coating over the soldered joints where my motors are connected. Im just trying to fully waterproof the drone and afaik if water gets on those pads it would cause a short? I also dont think that its a problem if I put coating over it but I just wanna make sure. I coated everything else except the boot button, gyro etc.

That is usually the whole point of conformal coating quad electronics. You cover everything with it including solder joints. Just be extremely careful not to get any into the sockets, buttons or on the barometer chip (which has a hole in the top of it), otherwise things will stop working or become unreliable.

Conformal coating is a love/hate thing. Some people swear by it any others who avoid using it have dropped their quad into puddles of water with no conformal coating without any issues. If you need to re-solder anything, any conformal coating on the solder joint ends up creating a right mess when you try to burn it off or re-solder through it.

(29-Feb-2024, 01:33 PM)SnowLeopardFPV Wrote: Conformal coating is a love/hate thing. Some people swear by it any others who avoid using it have dropped their quad into puddles of water with no conformal coating without any issues. If you need to re-solder anything, any conformal coating on the solder joint ends up creating a right mess when you try to burn it off or re-solder through it.

I'm firmly in the "love it" camp. I use MG Chemicals "Formula 422C" and I never had a mess when I soldered through, but it is specifically formulated to allow soldering through. Also I always use the flux paste. The only disadvantage of conformal coating for me is that I can't clean the board as usual after soldering if I solder through, because my PCB cleaner (IPA) will remove the conformal coating.

Also, a "pro tip" is to cover in kapton tape what you don't want covered and be very careful around barometers. With very low viscosity conformal coat like Formula 422C it is easy to put a big drop a good 5mm away and have it flow and engulf what you don't want.

(29-Feb-2024, 04:23 PM)Luk5569 Wrote: ...
Also, a "pro tip" is to cover in kapton tape what you don't want covered and be very careful around barometers. With very low viscosity conformal coat like Formula 422C it is easy to put a big drop a good 5mm away and have it flow and engulf what you don't want.

A tiny blu-tack ball squished onto the baro, reset switch, USB, etc works peachy too! Roll off and back into the blu-tack borg ball...

I recently bought some MG 419D after watching a video on YT, haven't used it yet, but we'll see. I know nothing about it from first hand experience, just what people on here have said and YT. No one seemed to specify any particular brand or type, so i want with acrylic as opposed to silicone. Can anyone confirm you don't need to cover the ceramic top of chips. I would prefer the CPU on the FC dissipates heat as effectively as possible which kind of requires it not to have a layer of plastic on top of it. Also ceramic is not conductive AFAIK.

(01-Mar-2024, 03:58 AM)Pathfinder075 Wrote: I recently bought some MG 419D after watching a video on YT, haven't used it yet, but we'll see.  I know nothing about it from first hand experience, just what people on here have said and YT.  No one seemed to specify any particular brand or type, so i want with acrylic as opposed to silicone.  Can anyone confirm you don't need to cover the ceramic top of chips.  I would prefer the CPU on the FC dissipates heat as effectively as possible which kind of requires it not to have a layer of plastic on top of it.  Also ceramic is not conductive AFAIK.

All ICs are sealed and waterproof by design, so as long as the legs of the IC right up to the edge of the ceramic body are covered in conformal coating then that will be fine.

Acrylic conformal coating can potentially crack under stress if if a board is flexed. Silicone coating on the other hand is usually a slightly rubbery compound that will give and flex without the watertight seal being breached.

I'l try it for a bit. Kind of hoping the board won't be flexing though (and if it does, it's probably going to be toasted afterwards).

Half the issue was actually finding coatings in the UK. There were a few sketchy listings on ebay but for whatever reason at the time I didn't have many legit looking listings. Anyway I will order some silicone when I have the need.

I'm very interested in finding out practical differences between MG 419d and 422C. All it says in the product description is that 419d is acrylic and 422c is acrylic/silicone.

It was said above acrylic may crack easier when flexed, but the product description calls both "flexible". So IDK.

Neither description mentions the biggest advantage of 422c - through solderability with no mess. Perhaps they differ in this? I'd recommend to do a test on some old pcb to see, unless someone here knows it can be soldered through easily.

One more thing about using conformal coating in general. I've used it on lots of electronics, but yesterday I had it dissolve paint on top of a radiator on a hglrc zeus 48A ESC. Normal pcb screen printed text is resistant, but it seems they used normal paint to put text on top of the radiator which promptly smeared on the first touch of conformal coat. If I was doing one like it again I would seal just the edges.

The only time a pcb might flex is when you ram it into the ground or some other object with some force. In normal operation, it shouldn't be flexing if you bolted it correctly and used gummies as required.

An interesting side note (of sorts) form a couple of videos I watched was the comparison between acrylic coating and nail varnish. If you don't have big bucks for conformal coating, nail varnish may also work. But then thinking about it, nail varnish and acrylic plastic coating are pretty much the same in terms of basic waterproofing. i would be interested to find out what is in those spray cans they sell on ebay, badged as waterproofing for PCB's and how effective it is.

As to your question Luk, the problem is removal. The silicone stuff is apparently less of a pain to remove if you need to resolder. The acrylic stuff needs acetone at a guess to remove. They sell acrylic conformal coating remover (thinners), but my guess is it's a solvent like acetone or xylene. Over here you can buy acetone at most pharmacies. Or you could solder on top of the board and use decent extraction or wear an ABEK1 respirator (which is what I do). As to the smearing of paint, that will be the thinners in the coating, which will be a solvent of some sort. if you paint acetone on any paint, it generally smears.