A thin polymeric film that conforms to the contours of a printed circuit board to protect the components of the board is a conformal coating material. Usually applied at a thickness of 25-250 μm[1](micrometers), Conformal coating is applied to electronic circuits to protect against extreme humidity, dust, chemicals, and temperature.It is possible to apply coatings in a variety of ways, including cleaning, spraying, dispensing,

If insulating surfaces become contaminated with ionic substances such as fingerprint residues, which can become weakly conductive in the presence of moisture, precision analog circuitry can experience degraded precision. (Sudden drops in performance at high humidity, for example when a technician breathes on it, are the classical indication of micro-contamination on an analog circuit board). A suitably chosen conformal coating can reduce the effects of mechanical stress and vibrations on the circuit and its ability to perform in extreme temperatures.

For example, a silicon die is mounted on the board with an adhesive or a soldering process in a chip-on-board assembly process, then electrically linked by wire bonding, usually with gold or aluminum wire of.001 inch diameter. The chip and wire are fragile, so they are encapsulated in a conformal coating version called "glob top." This protects the wires or the chip from being harmed by unintentional touch. Increasing the voltage rating of a dense circuit assembly is another application of conformal coating[5]. Particularly at high altitudes, an insulating coating can withstand a far stronger electrical field than air.