Electronic – Can acrylic latex spray paint be used as a DIY solder mask


I have recently begun etching my own circuit boards for miscellaneous Arduino projects and I need to apply a solder mask so that my copper traces don't oxidize.

I bought this acrylic latex spray paint for a different project, but I am wondering if it could be used as a solder mask.

My thought is that I would solder my components on first and then spray the board. Possibly, I would just cover any sensitive components with a small piece of masking tape first, but largely I wouldn't even think this would be necessary(?).

Any thoughts or reasons why this would mean certain doom for the board or, more importantly, why this may be unsafe or a fire hazard?

Best Answer

It looks like it might work "okay", certainly unlikely to damage your circuit in any way (unless sprayed in pots/switches/etc) Check if it says flammable in the datasheet to ascertain fire safety.

However, if you are just looking for a "sealant" to add after populating the PCB (as you mention in your question), then there are plenty of coatings around specifically for this purpose. They are usually know as Conformal Coatings.
There are various types and methods of application, so you need to decide which is best for you. Here is a comparison of the various types (acrylic, epoxy, etc)
Some will protect the PCB from moisture, oxidising, etc, but you can solder through them if you need to alter something (e.g. spray lacquers)
More permanent and hard wearing solutions include potting compounds (e.g. put circuit in suitable potting box, pour compound in, leave to set)
Look on places like Farnell, RS, Mouser for "PCB coating" or "Conformal Coating" and you will get plenty of options.
Here is an example of a spray on conformal coating you can solder through.
Conformal coating is not just to prevent oxidisation, it also helps prevent problems caused by contamination (e.g. acids/alkalis) or moisture (important for e.g. sensitive/high impedance circuits), and also can protect against arcing in high voltage circuits (with suitably high breakdown voltage rated compound)

If you are looking for something to apply before populating the board to stop trace oxidisation, then see the tinning suggestions in the other answers.