Designer III Blog June Archive

Conformal coating is not a Hermetic Seal

A very common misconception is that Conformal Coating is a Hermetic Seal. It is used a lot in the Coal Mines, and the Electronic Industry in general, to keep the caustic dust off circuit boards.

As Conformal Coating is not a hermetic seal, what real happens is the impurities in the water are kept away from the circuit, but the water itself reaches the traces. Since the water is now fairly devoid of contaminates the water acts more like a dielectric insulator. You never notice it in a low impedance digital circuit, but unless debugging is an obsession don't let it get near a RF tuning circuit or a high impedance Wireless Sensor Network circuit.