Solving 3 of the Biggest Problems Facing Modern Conformal Coating Application
Conformal coatings have a long and storied history with printed circuit boards. A good conformal coating protects PCB components from moisture, corrosion, contaminants, and additional PCB threats like vibration and thermal shock. Coatings are a complicated science, and there isn’t one best coating or application method for every job. These choices are dependent on the design, use case, and assembly of the PCB. For instance, manual brushing PCB coating material is a slow, tedious process; but for small batch applications, it’s quite cost-effective.
Regardless of the chosen method, there are fundamental application errors that can occur, leading to defects forming in the coating which ultimately limit the functional service life of the PCB.
Most Common Problems in Conformal Coating Application
The printed circuit board industry is rapidly evolving. Just think of all the massive technological advancements we’ve seen in the last 30 years! PCBAs evolved at a similar rate. Through this evolution, we’ve noticed two significant trends that cause issues with conformal coating application.
• Components are becoming more intricate while also being subjected to more demanding performance expectations
• PCBs (and tech) are shrinking in size, causing the components to become smaller and placed far more densely
The second point makes conformal coating application incredibly challenging. As there’s less space to work with, the material properties of conformal coatings are limiting PCB performance. Coatings need to flow and distribute evenly across components, but the natural surface tension, adhesion, and cohesion of the material prevent proper distribution when space is tight.
This is just one symptom of an increasing problem. When we look at the issues that cause failures in design, we notice three specific pain points. In no particular order, they are:
• Bubbles forming in the coating
• Too much or too little coating spread around sharp corners
• Defects emerge during intense thermal exposure
These are the three major killers of conformal coating application.
Solving Common Application Failures for PCB Conformal Coatings
UV Curable Coatings for PCBs
Growing bodies of research show promise for UV LED curable conformal coatings. In dealing with the sharp component edges, fast-curing coatings have an advantage as they solidify before the liquid flows to the base of the component. As such, they hold their intended shape nicely.
We recommend UV-curable coatings over other fast-curing coatings (like two-part coatings) due to the ease and relative lack of specialized machinery. Two-part materials often require specialized mixing stations and heavy preparation. UV-curable coatings are not without their downsides. They typically require multiple layers of application due to the limited penetration of UV light through the material. However, there is hope.
UVA spectrum light waves have shown far greater ranges of penetration, allowing for thicker layers of conformal coating application and curing. Additionally, UVA curable coatings show far greater thermal shock resistance and physical stability. These are not the only new coatings in development.
Conclusion
The world of conformal coatings is evolving to meet the ever-changing requirements of PCBs. This is an iterative process; and as such, it’s important to stay up to date with the latest developments. The best way to do so is to sign up for our mailing list, ensuring you get the latest news and articles the moment they break.
LINK:https://blog.humiseal.com/solving-3-of-the-biggest-problems-facing-modern-conformal-coating-application
