Conformal Coating

Conformal coating is a thin protective film applied over a fully assembled printed circuit board to shield it from moisture, dust, salt, chemical contaminants, and corrosion. The coating "conforms" to the contours of the board and its components, hence the name. It is widely used on electronics that must survive harsh, humid, or condensing environments, and is sometimes encountered on mining hardware deployed in damp or dusty sites.

Coating types

The IPC-CC-830 specification recognises several coating families, including acrylic, polyurethane (urethane), silicone, epoxy, UV-curable, and parylene. Acrylics are valued for being easy to rework; silicones tolerate wide temperature swings and humidity; urethanes resist chemicals and abrasion but cure slowly; and parylene, applied as a vapour, gives the thinnest and most uniform protection but cannot be removed by ordinary means. Each balances protection against how readily a technician can later service the board.

Working through a coating

Conformal coating complicates repair because solder will not flow through it and probes will not make contact. Acrylic and some urethane coatings can be softened or dissolved with the appropriate solvent, while others are removed by careful mechanical abrasion or localised heat over just the joint being serviced. After a repair the cleared area should be re-coated to restore the barrier. Because most mining hashboards ship uncoated, a technician should always check whether a board is coated before attempting reflow or probing, since trapped solvent or residue can interfere with a clean joint and with flux activation.