PVA Pro Tip #1: Conformal Coating Dewetting – Frequently Asked Questions
Understanding Conformal Coating Dewetting
When it comes to protecting circuit boards, a smooth, even application of conformal coating is essential. But if the surface isn’t properly prepared, you may run into a frustrating issue known as dewetting. This phenomenon causes the coating to pull away from certain areas, leaving components exposed and vulnerable. Below, we break down what causes dewetting, how to recognize it, and most importantly—how to prevent it.
Q: What is conformal coating dewetting?
Conformal coating dewetting, occurs when a coating material fails to evenly coat a surface, instead pulling away or contracting, leaving areas unprotected. This is often caused by contamination, surface energy mismatch, or improper surface preparation.
Q: Why is cleaning important before applying conformal coating?
Cleaning your circuit board prior to conformal coating is critical for successful coating. Many manufacturers, however, do not clean their boards before this process which can then lead to dewetting.
Q: What are some common causes of conformal coating dewetting?
Dewetting can be caused by various contaminants on the board surface, including foreign objects, flux residue, oils from handling, and even trace amounts of mold residue on integrated circuits (ICs) from the manufacturing process.
Q: How can I tell if dewetting has occurred?
Dewetting is visually apparent as the conformal coating pulls back or retracts from certain areas of the circuit board that it initially covered leaving unprotected areas.
Q: How can dewetting be prevented?
To prevent dewetting and ensure proper adhesion of the conformal coating, PVA recommends implementing a cleaning or surface treatment process before applying the coating.
Q: What kind of cleaning process is recommended?
Implementing a basic cleaning step using a brush or wipe and a solvent like isopropyl alcohol is a good start. For more stubborn micro-layers of residue, plasma cleaning can be particularly effective.
Q: How to fix dewetting?
If dewetting occurs, you’ll have to remove all conformal coating from the board and reapply from the beginning.
Q: Why is preventing dewetting so important when working with expensive materials?
If dewetting occurs, it can result in wasted expensive materials and compromised product quality, leading to costly rework or replacement.
