Benefits of Conformal Coatings

Manufacturers in the electronics, transportation, aerospace, defense and medical industries have applications that need to withstand elements of heat, cold, rain, snow, vibration, fungus, oxidation and corrosion through decades of operation. Without protection, their applications would not survive these harsh environments.

Conformal Coatings Protect Circuit Boards and Electronic Devices from Their Environments

Conformal coatings add a protective, non-conductive dielectric layer to a circuit board or electronic device. There are five primary conformal coating types, each with dozens of variations, meaning there are hundreds of conformal coatings to choose from. Coating costs vary depending on the material type and application method; however, few manufacturing companies fully understand which coating is right for their application.

Define Clear Performance Requirements

It is critical to define the performance requirements for an application. What temperature range will it face? Will it have to withstand moisture? How about vibration? All of these factors and more can affect the performance of an application, making it essential to thoroughly consider them during the design and development process.

Knowing the potential environmental challenges an application may face is crucial in ensuring its success. For example, if an application will be used outdoors, it must be able to withstand a wide temperature range. Extreme heat or cold can cause malfunctions and even permanent damage to the device. Therefore, determining the optimal operating temperature range is imperative.

Moisture is another factor that should not be overlooked. If an application will be exposed to high levels of humidity or water, it must have appropriate protection to prevent damage. The level of protection needed against moisture helps determine the coating that should be selected.

The Five Types of Conformal Coatings

There are five main types of conformal coatings, each with its advantages and shortcomings: 

Acrylic Resin (Type AR)
Acrylic conformal coatings are fungus resistant and can be applied by brush, spray or dip methods. Acrylics dry to the touch at room temperature in minutes and have desirable electrical and physical properties. Typically applied at 0.002 to 0.005 inches thick, most acrylic variations cure in as little as 30 minutes, making them a great choice for a short turnaround time.

Acrylic coatings are not well suited for high-temperature environments since they can usually only withstand temperatures of up to 125°C.

Epoxy Resin (Type ER)
Epoxy conformal coatings are two-component compounds applied by brush, spray or dip methods. They deliver a rugged coating with good resistance to damage from humidity, high abrasion and chemicals.

Epoxy coatings are known for their extreme hardness, making them a good choice when  toughness and durability are needed; however, their extreme hardness means rework and repair are difficult. Epoxy also tends to experience shrinkage during the polymerization stage, and extreme temperatures reduce the stress resistance properties of epoxy coatings.

Polyurethane Resin (Type UR)
Applied by brush, spray or dip methods, polyurethane (also called urethane) conformal coatings deliver humidity and chemical resistance as well as excellent dielectric properties for long periods.

Polyurethane coating is often the optimal choice for devices exposed to chemical solvents. Its dielectric properties promote miniaturization because it insulates signal traces from circuits that are close together. Polyurethane also retains high dielectric properties over time and is often used to mitigate tin whisker growth.

Polyurethane’s resistance to solvents means it can be difficult to remove or rework. It also does not do well in high-vibration or high-heat environments.

Silicone (Type SR)
Silicone conformal coatings perform well in high-temperature environments, even up to 200°C, making them a popular choice for transportation applications. It provides resistance to humidity and corrosion and can be applied by brush, spray or dip methods in thicker layers than other coatings, which helps in damping any vibration.

Silicone is less resistant to abrasion and solvents than other coatings and requires more care to apply correctly.

Parylene
Parylene is applied through vapor deposition polymerization (VDP), resulting in a uniform coating. Parylene can be applied to virtually any surface as well as objects of any shape such as glass, metal, paper, resin, plastics, ceramics, ferrite and silicon. It is completely inert, making it an excellent choice for implants and biomedical devices.

Rework is difficult with Parylene due to its unique application process. Operators must ensure the object to be coated is completely clean and meticulously mask any areas not to be coated.

Find a Company That Provides All Five Coatings

When researching conformal coating providers, seek out a company that can offer the five types of conformal coatings. These providers work directly with manufacturers to find the best conformal coating to meet the performance requirements of their particular application.

Specialty Coating Systems offers customers regionally-located coating facilities to handle their engineering and production requirements. To discuss the benefits and properties of conformal coatings and your protection needs with an applications specialist, contact us online or call +1.317.244.1200.