PCBs intended for use in tough or non-controlled environments are covered in a protective coating, often referred to as ‘conformal coating’, which provides protection to the electronics against the ingress of moisture and dirt. It also helps prevent the effects of condensation affecting the operation of the PCB during heating (power-on) and cooling (power-off) cycles.

Functional testing is usually performed from the edge connector of a circuit and therefore the coating does not interfere with the operation of the test, however, as soon as there is a need to probe internal networks or clip a device for diagnostic testing the coating needs to be removed.