Conformal Coating - The Basics You Should Know

Conformal coatings are merely a protective coating applied to printed circuit boards. They are applied in liquid form and cured or dried in a variety of methods. They act as a protective barrier between the devices' environment and the electronic components mounted on electronic assemblies.  

What They Do

Originally, coatings were primarily used to protect against environmental contamination like moisture and debris. They lessen the threat of solder and trace corrosion while improving the board's ability to handle thermal and mechanical shock. Electronic components that have to function in harsh environments benefit most from coating because they also increase mechanical bond strength. 

In addition to the functions above, in today’s electronic world, an essential benefit of conformal coatings is its’ ability to increase the usable board surface space. Consumer demand for smaller and smaller electronic devices continues to grow, and senior electronics engineers lead innovation by adding more functionality to these high-demand consumer products.  The advances in technology require placing more parts on shrinking printed circuit boards, so the space between surface mount devices is rapidly disappearing. Component spacing is critical. If they are too close, they can unintendedly transmit heat or electricity to adjoining parts. These low voltage electronic components are super sensitive to temperature and even the weakest electrical signal. To avoid these conductive concerns, engineers include a  protective coating.

Best Coating Type & Method

There are several types of coatings used for printed circuit board protection, and development engineers typically determine the kind that best fits the application. Acrylic is the most common type because it is easy to use. Curing, removal, and, replacement of acrylic is a relatively simple process when repairs are needed. Other coating types offer specific useful properties but are more difficult to remove once applied, i.e., silicones, polyurethanes, and UV cured coatings. 

As for our preferred method, we like a mechanized robotic application.  This process requires an initial set up of a programmable machine. Once set, the computer controls retain the programming, and it knows the location of every part and every void on the board. It can be set up to target specified parts, specific areas, or the entire board. The computer controls the flow, position, and the speed of the applicator, which eliminates human error.  Our procedures include a visual inspection of each coated board, via a UV light which makes the coating very easy to see, and brings attention to any voids. We believe machine coating is the most efficient method for most applications, but of course, there are always exceptions.