This work has been done for illustration purposes. Do not try to follow these instructions, if You don't have prior knowledge with conformal coating. Thanks.

Background

This page is a result of discussion from industrial io baseboard.

Sometimes printed circuits are coated (lacquering) to protect them from humidity and other environment effects. This way they can work in much more extreme conditions e.g outside, industrial plants. This does not make them waterproof, it just helps the PCBs copper plating and solder joints to withstand higher level of humidity and even corrosive environments (some industrial plants).

Materials & Application

Conformal coating material Humiseal e.g Humiseal 1B73. Humiseal contains UV chemical marker (fluorescence), which glows under black light. That way we can see the coating under black light, otherwise it's transparent.

1-3 mils (25-75um) layer is recommended, thicker layer may crack at some stress levels.

A brush was used to apply the coating and it's important to avoid electromechanical parts - USB connector, reset switch, board pins. I also kept clean the MCU chip casing, for heat dissipation.

Curing (drying) is done 60 min. @ 76°C if You follow the specs.