Conformal coating is used to protect electronic circuit boards from the elements. It has insulative properties and can also protect against chemical contaminants, salt and other corrosives, extreme temperatures, and physical damage. There are five main types of conformal coating available in today’s markets. Before choosing one, equipment and device manufacturers can read on to find out about their options or go here to get professional help with choosing the right one.
Parylene (Type XY)
Parylene coatings are formed in a vacuum environment and applied as a gas within the vacuum chamber. The coating itself is hot, but the substrate must be at room temperature during application. Parylene cures into a clear plastic film that coats all external areas of the product to form a moisture-impermeable barrier.
Acrylic (Type AR)
Acrylic coatings are easy to apply and remove, dry rapidly, and reach optimal levels of protection in minutes. They’re resistant to fungi and humidity, have a long pot life, and do not shrink during curing. Additionally, acrylic coatings require no heat during curing, which means they’re perfect for heat-sensitive components.
Silicone (Type SR)
Silicone coatings have good dielectric properties, exceptional light transmission capabilities, and fantastic moisture and corrosion resistance. They’re often used in solar applications since silicone also functions well at high temperatures and is resistant to both dirt and UV light. The primary issue with silicone is that it is not solvent soluble, which means it must be removed using chemical strippers if repairs are needed.
Polyurethane (Type UR)
Polyurethane coatings are typically applied as two-component formulations, but they are now available in single-component formulas, as well. Polyurethane offers greater chemical resistance than acrylic and is great for high-humidity environments. The primary problem with polyurethane coatings is that they have lengthy cure cycles, so it takes longer to apply them. Some formulations also require a modest application of heat to ensure optimal curing.
Epoxy (Type ER)
Like most polyurethane coatings, epoxy coatings are typically formulated as two-part compounds. When the two compounds are mixed together, they start to cure immediately. Some epoxy coatings also come in single-part formulations that can be cured by applying heat or UV light. Epoxy provides less humidity resistance than some coating materials but it is known for excellent abrasive and chemical resistance. Some shrinkage usually occurs upon polymerization, which means manufacturers must create buffers around sensitive components.
Application Methods
Manufacturers will also have to decide on an application method for their conformal coatings. There are four primary methods for applying coatings: dipping, misting, brushing, or non-aerosol spraying. Each coating material has different application requirements, so it’s best to trust the judgment of a conformal coating specialist when deciding which method will be the best fit.
The Bottom Line
Conformal coatings provide a high level of protection for electrical components, but some materials are more effective than others. Before choosing a coating type, equipment manufacturers should discuss their unique needs and environmental applications with a specialist to determine which material will best meet the company’s requirements. If applied correctly, conformal coatings should offer adequate protection for years to come, so it’s worth working with a reputable service provider.