Parylene is one of the most widely used and widely trusted conformal coatings in any industry. It is used in every application from space travel to microwaves, and it is strong, reliable, and long-lived--but before it can do any of that, parylene needs to have proper adhesion. Let our experts explain why a little cleaning goes a long way in this case.
The rule of thumb when it comes to parylene coating adhesion is that cleanliness is crucial. If the surface area is contaminated in any way, the adhesion may be interrupted, or the parylene may not be able to provide strong, long-lasting protection. This means that no matter the situation, properly cleaning the substrate material and using clean equipment is crucial. However, cleanliness is only the first step. There are a few additional mechanisms that are also important for strong coating adhesion (and they just so happen to rely on cleanliness).
Chemical bonding occurs at the place where conformal coating and the substrate surface meet. Strong bonding is necessary because it allows proper adhesion that will last for extended periods of time--but any contamination on the substrate surface can interrupt this bonding, so again, cleaning is a critical first step.
Adsorption takes place as the coating "spills" over the surface, which is what allows parylene to coat evenly the most unusual shapes and crevices. If contamination is present, the coating won't be able to flow freely and adsorption, as well as adhesion, will be interrupted.
When conformal coating dries and breaks through the substrate surface's top layer, mechanical interlocking is occurring. However, unclean surfaces are too smooth to allow mechanical interlocking, so a clean, rough surface is necessary.
Although all three of these mechanisms aren't required for adhesion, they help guarantee a reliable, long-lived bond between parylene and the substrate surface. This is why cleaning is a crucial part of the adhesion process.