In the second part of a two-part series of articles, AZoM talks to Masterbond about the properties and benefits of conformal coatings.
Could you outline the best way to apply conformal coatings?
Typical methods used for applying conformal coatings include brushing, spray coating, and dip coating (Figure 1). Depending on the nuances in the production settings, the most suitable techniques are used.
However, irrespective of the application method used, it is vital to begin with a clean and contaminant-free surface to enhance adhesion.
Figure 1. Conformal coatings can be applied by dipping, spraying, flow coating or any other conventional processing technique.
What would be a typical thickness for a conformal coating?
The thickness, design, and operating parameters of the eventual application have to be determined keeping the processing in mind.
To this end, two main methods are used to protect components: providing a conformal coat that measures a few thousands of an inch, or encapsulating the components to render a thicker layer, which might have a thickness of approximately ¼ inch.
How do you select the right conformal coating for a specific application?
In order to select a suitable conformal coating, the main application need has to be taken into account. When thermal stability or stress relief is important, a silicone coating provides a suitable solution. When there is a thermal variance between the coating and the components, flexible coatings that can bend without delaminating or cracking are extremely important. The coating material can absorb any thermal stress induced during temperature cycling and such flexibility is particularly important in present miniaturized circuits that have fragile leads and small components.A rigid epoxy-based coating can be used when chemical or abrasion resistance is important.
The next aspect to be considered is the specific environment to which the assembly will be exposed. Severity and duration of contact, heat, humidity, shock, stress, vibration, the types of contaminants, and degree of mechanical stress are other important factors that dictate the suitable combination of coating properties.
Additional factors involved in the selection of a conformal coating include application time, reworkability, cure time, and capital and labor costs. For example, UV curable coatings are usually recommended when processing speed is important, as long as limited temperature and chemical resistance are satisfactory.
What if you have a specialized application involving high voltage?
In order to prevent electrical breakdown of the coating, high dielectric strength is very important.
The thickness of the coating will differ, depending on the voltage resistance required.
Lastly, could you please summarize the primary benefits of conformal coatings?
Conformal coatings considerably improve the longevity and reliability of high-performance electronic printed circuit boards.
They are capable of protecting electronics from environmental conditions that can hinder circuit performance and promote premature failure.
This information has been sourced, reviewed and adapted from materials provided by Master Bond Inc.
For more information on this source, please visit Master Bond Inc.