Conformal coating, for the purpose of this document, is defined as a thin, transparent, polymeric coating that is applied to the surfaces of PCAs to provide protection from the end-use environment. Typical coating thickness ranges from 12.5 µm [0.49 mil] to 200 µm [7.9 mil].

Processing characteristics and curing mechanisms are dependent on the coating chemistries used. The desired performance characteristics of a conformal coating depend on the application and should be considered when selecting coating materials and coating processes. Users are urged to consult the suppliers for detailed technical data.

This guide enables a user to select a conformal coating based on industry experience and pertinent considerations. It is the responsibility of the user to determine the suitability, via appropriate testing, of the selected coating and application method for a particular end use application.

A conformal coating may have several functions depending on the type of application. The most common are:

• To inhibit current leakage and short circuit due to humidity and contamination from service environment.

• To inhibit corrosion.

• To improve fatigue life of solder joints to leadless packages.

• To inhibit arcing, corona and St. Elmo’s Fire.

• To provide mechanical support for small parts that cannot be secured by mechanical means, to prevent damages due to mechanical shock and vibration.