Application Methods of Conformal Coatings

Applying Conformal Coatings

After deciding on the conformal coating type, the next step is to select the application method. It is crucial to select the correct one as it determines the protection level of your coating. Even the best conformal coating may provide inadequate levels of protection if it is incorrectly applied.

There are 5 main ways to apply conformal coatings:

Manual Spraying
Coating is easily applied using an aerosol can or handheld spray gun. Although it is widely used in low volume production due to its simplicity, this method can be time-consuming because areas not requiring coating need to be masked. Being sprayed manually may result in inconsistent coverage, varying from board to board.
Automated Spraying
A programmed spray system that moves the printed circuit board on a conveyor under a reciprocating spray head that applies an even layer of conformal coating. Ideal for single layer PCB plate, however, areas not requiring coating need to be masked.
Selective Coating
An automated coating process using programmable robotic spray nozzles for conformal coating in specific areas on the printed circuit board. It is mainly used in high volume processes and can eliminate the need for masking. The applicator may include built-in UV lamps to immediately cure the coating.
As the name suggests, the process involves immersing and withdrawing the printed circuit board in the conformal coating solution. The film formation is determined by the immersion speed and time, withdrawal time, and viscosity. It requires a great amount of masking before coating, and is only applicable if both sides of the board can be coated.
A simple application technique commonly used in repair and rework applications. It is applied with a brush to specific areas on the board. It is a low cost but labor intensive and highly variable method, which is ideal for small production runs.

To achieve an even coating coverage with the right thickness can be difficult. Hence, measurements for coating thickness must be taken to ensure that it meets the quality specifications. Find out more about the commonly used measurement methods here.