To rework a board coated with Protektor acrylic conformal coating, remove the coating locally with the matching thinner, clean the area, repair, and recoat. Micron 3308 Protektor Conformal Coating Remover and Thinner is the thinner for Protektor conformal coatings, and the Protektor 3100 and 3110 pages say the cured film can be easily removed using Protektor Conformal Coating Thinner. After removal, clean with Micron 3400 Protektor PCB Cleaner before recoating.
Why it happens
- Acrylic coatings need a solvent remover. A cured acrylic film protects the board well, which also means you cannot solder through it cleanly. It has to come off first.
- Coating too thick. If coating from a carboy is too heavy for your process, it may need thinning.
You will notice you cannot solder through the coating at a repair site, or the coating is too thick to flow and level.
How to fix it
- Removing or thinning Protektor acrylic coating: Micron 3308 Protektor Conformal Coating Remover and Thinner, 5 L. Its page says it is a thinner for use with Micron Protektor conformal coating products, describes it as plastic safe and compatible with most sensitive substrates used in electronic parts and enclosures, and lists moderate evaporation and blush resistance.
- After removal, before recoating: Micron 3400 Protektor PCB Cleaner. Its page says it provides a clean surface for the re-application of conformal coating.
The 3308 page gives no directions and no thinning ratio. Follow the TDS, and ask Micron for the right method and ratio for your process. A sensible workflow:
- Power off and disconnect the board.
- Work in a ventilated area away from ignition sources.
- Remove coating only where you need to work.
- Clean the area so no softened coating or residue is left.
- Make the repair.
- Clean again and let it dry fully.
- Recoat the repaired area and inspect it.
What to avoid
- Boards must be unpowered. 3308 is a solvent: treat it as flammable until the SDS says otherwise, keep it away from sparks, flames and hot surfaces, and use ventilation.
- Compatibility with silicone coating (3708) and UV-cured coating (3608) is not stated. Do not assume 3308 removes them.
- Test on sensitive plastics first, even though the page describes it as plastic safe.
- Do not guess a thinning ratio. No ratio is published.
When to ask an expert
Ask Micron technical if:
- the coating on the board is not a Protektor acrylic, or you do not know what it is;
- you need a thinning ratio for spraying or dipping;
- the coating is silicone (3708) or UV-cured (3608).
FAQ
Can 3308 remove any conformal coating?
Micron's pages say it is for Protektor conformal coatings, and the 3100 and 3110 pages say their cured film can be removed with it. Removal of silicone or UV-cured coatings is not stated.
Is 3308 safe on plastic parts?
Its page describes it as plastic safe and compatible with most sensitive substrates used in electronic parts and enclosures. Test on any plastic you are unsure about.
Should I strip the whole board or only the repair area?
Usually only the area you need to work on, plus a small margin. Stripping the whole board means recoating all of it and adds handling risk. Recoat the repaired area so it overlaps the existing coating.
How much thinner should I add to the coating?
Micron does not publish a ratio. Ask Micron technical for your application method.
Do I need to clean the board after removing the coating?
Yes. Clean with a PCB cleaner such as 3400, which is listed for preparing a clean surface for recoating, and let the board dry fully.
See the product: Micron 3308 Protektor Conformal Coating Remover and Thinner. Related: 3400 Protektor PCB Cleaner. More electronics fixes: electronics hub.