What exactly is a conformal coating?

A conformal coating is a protective film that conforms to the surface of a circuit board assembly.

The conformal coating can be used to create a protective barrier between contaminants in the environment and the assembly.

It is also usually used on electronic products that are exposed to adverse environments where contamination, heat, chemicals and / or moisture are prevalent.

This means that the printed circuit board assembly may be protected from damage due to contamination, salt spray, moisture, fungus, dust and corrosion caused by harsh or extreme environments.

What does a conformal coating look like?

When the conformal coatings are applied, some materials are clear and glossy on the surface of the circuit board assembly.  Some conformal coatings may be translucent or opaque. Others are too thin to be easily seen.

Some coatings are hard while others are softer with a more rubbery texture.

Conformal coatings may include a fluorescent trace that glows a bright blue /green when illuminated by ultraviolet or black light.  This fluorescence allows for easy inspection of the applied liquid coating.

How are conformal coatings applied to circuit boards?

Some coatings, such as acrylics, polyurethanes, silicones and epoxies, are usually applied in a liquid state, using spray, dip or brush methods. They harden and dry through solvent evaporation or chemical cure reactions.

However, there are many coatings that are not liquids such as Parylene and ALD coatings. They are applied in a chemical vapor deposition process.