What is conformal coating?
In simplest terms, it’s a plastic or urethane that you paint (usually via spray can, but also by brush) over a circuit board to protect it from harm. For example if you have a circuit that it going in a boat or other high humidity/highly corrosive area, you may want to coat everything in plastic to keep it pristine and functional. You’ll see this listed as a feature on many marine electronics. It’s also a little bit of insurance, say you are shoving a circuit board into a metal enclosure (such as our Wallbox project) and you want to ensure that none of your metal bits stick out and touch the case, which could short them out or cause other problems. Lastly it will help show if someone has tampered with your design, and is sometimes applied to commercial products as a kind of warranty voider (if this coating is removed, we know you tried to do something). This isn’t so much the case anymore, but in the 80’s and 90’s when ISA cards could be easily modified, it occurred, if not all the time, at least occasionally.
That last feature is also a downside. Once you have sprayed your board with the coating it’s all coated in plastic. If you want to make a change to a wire or IC pin, you have to scrape or grind it off and then make your change. Most conformal coatings are like wood polyurethane, and sort of shred off when you scrape them.
One other protection it offers is from stray static discharge. You can’t zap a circuit if it’s covered in plastic! Static isn’t really the issue it used to be, but if you live somewhere very dry where you get a lot of zaps this may be a bonus.
- Electronics boards and parts can be virtually waterproof
- Protected from corrosion
- Protected from accidental shorting with stray metal
- Protection from static discharge
- Acts as a “glue” to help hold things together for a little more sturdiness.
- Once sealed it’s a pain to make changes
- Adds a little cost
- Needs an area that you’d feel comfortable spray painting in, as mist will get everywhere.
I use this coating below normally from Amazon, it’s well reviewed, and I’ve never had any trouble with it. They claim you can solder thru it, but I always scrape for re-work.