A vehicle is a volatile environment for sensitive electronics. Traditionally, custom enclosures and potting have served to protect PCBs from heat, vibration, contaminants, and other threats to a board's lifecycle and performance. However, as the number of electronic features in today's vehicles increases, the weight and space that enclosures and potting can consume puts pressure on automotive manufacturers. Are conformal coatings a viable alternative to these traditional approaches?
While factors like board complexity and environmental strains must be considered for each individual application, conformal coatings are often viable alternatives to traditional PCB protection and insulation methods. Coatings can be applied by automated selective application, manual spray, jetting, and brushing, and typically range in thickness from .002" to .005". Thin, light-weight coating applications can enable more boards to fit into a single space, unlike enclosures and potting which extend beyond the boards themselves.
Once applied, coatings can be cured in several ways. One-part, solvent-free light-curable conformal coatings cure when exposed to light that produces energy at the correct spectral output. The photoinitiators in the coating fragment to form free radicals, which begin to form polymer chains with the acrylates that comprise the coating. Once all the radicals have attached and formed a solid polymer, termination has occured and the coating is polymerized, or cured.
Light-curable conformal coatings eliminate both the need for mixing as is required with two-part epoxies, and the use of hazardous materials that can be found in solvent-based materials. Shadowed areas of the board can pose minor challenges, but can easily be cured by alternative methods such as ambient moisture in the air or heat curing of secondary thermal cure materials. Overall, the use of light-cuable conformal coatings can help reduce processing time with quick on-demand curing.
Conformal coatings can also electrically insulate the boards, potentially improving performance. They have also shown to slow tin whisker growth to extend board longevity.
Just like the vehicles themselves, each electronic application has unique requirements that should be considered when evaluating options for board protection and insulation. These are just some of the benefits and challenges of using light-curable conformal coatings, but they can certainly be considered a viable alternative to traditional enclosures and potting for automotive electronics protection.
