Coating process
Before coating a printed circuit board, it must be cleaned and de-moisturized within 8 hours of conformal coating. De-moisturizing can be done in an oven with temperature set to 88 °C to 98 °C for 4 hours. Methods of coating include spraying, brushing or dipping. Chemical vapor deposition is used to coat with paraxylene. Steps of a spray coating are as listed below.
a) Board is cleaned.
b) Protected areas like terminal pins, connectors are masked off or removed.
c) Coating is applied using a spray process on both sides of the PCB and its edges.
d) Coating is cured using oven according to the coating type.
e) Masking is removed and any removed parts are reassembled.
f) Board undergoes full production testing to ensure functionality of board is not affected by the process.