Conformal Coating Dewetting and How to Avoid It – Pro Tip #1
PVA Pro Tip #1: Conformal Coating Dewetting and How To Avoid It
Cleaning is Key
Keeping your circuit board clean prior to conformal coating is critical to any coating process. Despite this, many manufacturers are still opting not to clean their boards prior to conformal coating. In a recent Global SMT Panel “Etching, Cleaning, and Coating for Harsh Environments,” Trevor Galbraith estimated only about 20% of manufacturers clean their boards prior to conformal coating.
What is Dewetting?
The result of this lack of preparation can result in a common-known condition called dewetting. Dewetting occurs when a conformal coating will not adhere to a board surface. This is easily detected as the coating retracts from an area it had previously covered.
Foreign objects, flux residue, and even oils from improper handling can all result in dewetting. Jon Urquhart, PVA’s Global Director of Applications of Engineering, who was interviewed for the panel, goes on to explain, “If you’re performing a liquid applied conformal coating, whether you’ve got unreactive fluxes, fingerprints, residue upstream in the process that has carried over into the coating process, these are all contaminations or residues that must be removed from the substrates.” In fact, residues can even exist prior to board assembly, Urquhart says. “Tops of ICs may have trace amounts of mold residue left over just in the manufacturing process, way before it even gets to the build step.”
Conformal Coating Dewetting Examples
How to Combat Dewetting
To prevent dewetting and combat adhesion issues in your coating process, PVA recommends implementing a cleaning or surface treatment process prior to conformal coating. “Cleaning is key,” Urquhart explains, “The cleaning step alone is a good start, and plasma cleaning can help remove those micro-layers of residues left over.”
To learn more about combatting dewetting issues in your conformal coating process, or to make your manufacturing process more efficient, reach out to the team at PVA team and let us help make you a pro.