There are various conformal coating technologies available: Acrylic, Silicone, Urethane, and parylene.  Acrylic, Silicone and Urethane are the most common types used for printed circuit boards.

The main specification requirement should be the level protection afforded, but application and ease of removal for rework also need to be considered as they have an influence on the overall cost. Please contact us to discuss your requiremnents.

Acrylics

Acrylic coatings can be considered entry-level protection because they are economical and protect against a broad level of contamination.  They are easily applied and can be removed by using the appropriate solvent, making any rework economically viable. Unfortunately, as the acrylic can be removed using solvent, they do not protect against solvents or solvent vapour and therefore are of little use in certain applications.

Silicones

Silicone conformal coatings provide excellent moisture protection in a very wide temperature range. Coatings typically have a continuous operating temperature ratings of 200°C, whilst some specialist formulations are rated as high as 600°C for ultra-high temperature applications.  They are most widely used in high-temperature environments due to their ability to withstand prolonged exposure to higher temperatures. Due to this ability, they tend to be specified by the automotive industry.  However, because of its flexible rubbery construction they are not abrasion resistant and have a relatively weak resistance to solvents.

Urethanes

Polyurethane coatings provide excellent humidity resistance and far greater chemical resistance than acrylic coatings and have outstanding dielectric properties for extended periods. They are also exceptionally resistant to abrasion and other forms of mechanical corrosion/wear.

Removal of polyurethane coatings can be difficult due their high resistance to solvents.