Liquid Conformal Coatings

Liquid conformal coatings are thin polymer films applied to components and devices to protect them from contamination, moisture, temperature extremes and corrosion.

They are applied using wet processes such as brushing or spraying the coating onto the substrate surface or dipping the substrate into the coating. Application can be performed manually or automated to support consistent results.

What Are the Main Types of Liquid Coatings?

The most common types of liquid coatings include acrylics, epoxies, silicones and polyurethanes. Each coating type offers distinct properties and benefits, such as dielectric strength, moisture barrier, thermal resistance and reworkability. Variants within each coating type provide additional options to meet specific application requirements.

Acrylic Coatings

Acrylic resin (AR) conformal coatings provide an excellent barrier to moisture and humidity and offer fungus resistance, making them a common choice for protecting electronic circuitry. Their low chemical resistance allows components be removed or reworked more easily.

Epoxy Coatings

Epoxy resin (ER) conformal coatings provide strong moisture, chemical and temperature resistance along with excellent dielectric barrier properties. Their rigid, durable finish offers outstanding abrasion resistance

Silicone Coatings

Silicone resin (SR) conformal coatings are widely used in harsh environment applications, including under hood automotive applications, because they withstand prolonged exposure to high temperatures. They also be applied in thicker films to provide vibration dampening and isolation.

Polyurethane Coatings

Polyurethane resin (UR) coatings provide excellent humidity and chemical resistance while maintaining strong dielectric properties for extended periods. Their flexibility and abrasion resistance make them effective for protecting critical components.

What Industries Use Liquid Coatings?

Electronics

Electronic components like PCBs, LEDs, sensors, MEMS and semiconductors often use liquid conformal coatings for moisture resistance, corrosion protection and dielectric insulation.

Medical Devices

Liquid coatings can be used to protect medical devices and components, including elastomers, medical electronics and surgical tools, from moisture, chemicals and harsh operating environments.

Automotive

The automotive and transportation industry rely on liquid conformal coatings to protect electrical systems, gaskets and seals, sensors and other critical components from hostile vehicular environments.

Aerospace and Defense

Liquid conformal coatings protect aerospace and defense components from moisture, fumes and dust in harsh environments. Even chemical and biological agents and subsequent decontamination processes are no match for the environmental defense liquid coatings can provide.

Frequently Asked Questions About Liquid Coatings

How do I choose between epoxy, acrylic, polyurethane or silicone conformal coatings for a given project?

To select the right liquid conformal coating for your project, consider:

• The intended use of the application you’re coating
• The temperature ranges your application will be exposed to
• The environmental challenges the application will face
• What coating properties your application requires (e.g., moisture resistance, thermal stability, lubricity, etc.)
• Whether you anticipate the need for any rework or repair to the coatings
• How involved the coating application process is

For advice on which coating is best for your application, reach out to an SCS expert.

How thick should a liquid conformal coating be?

The appropriate thickness depends on the coating type and application requirements. Acrylic, epoxy and polyurethane coatings are applied between 25–127 µm (0.001-0.005 in), and silicone coatings are generally applied at 51-203 µm (0.002-0.008 in). An SCS applications specialist can recommend the right thickness for your application and operating environment.

Are liquid conformal coatings waterproof?

Liquid coatings offer varying levels of moisture barrier protection. To discuss which conformal coating provides the right level of water resistance or waterproofing for your project, reach out to an SCS expert for a consultation.

What is the curing process for liquid coatings?

Coating requirements vary by coating chemistry.

• Acrylics: Cure in up to 24 hours at room temperature or as little as 30 minutes in an oven.
• Epoxies: Single-part compounds cure thermally or by UV exposure; two-part compounds begin curing when mixed.
• Polyurethanes: Single-part compounds have long cure cycles that can last several days, while two-part compounds cure in one to three days.
• Silicones: Cure in approximately one hour at room temperature.

Can liquid coatings be removed or reworked?

Yes, but ease of rework or removal varies by coating type. Acrylic coatings have low chemical resistance, making them easy to rework or remove. Polyurethane, silicone and epoxy coatings are generally more difficult to rework or remove due to their resistance to chemicals, heat and abrasion. Learn more about liquid coating removal. 

What certifications or standards apply to liquid conformal coatings?

IPC-CC-830C is the primary material qualification standard for conformal coatings is. It establishes qualification requirements for materials and evaluates key characteristics such as application, performance, shelf life and material properties.  Learn more about conformal coating standards, or see a full list of SCS’s certifications.