The types of conformal coatings and their advantages and disadvantages

Tony Zh Yi

·June 6, 2025

·5 min read

The types of conformal coatings and their advantages and disadvantages — Image Source: pexels

Conformal coatings work like a shield to protect circuit boards. These thin layers keep electronics safe from water, dust, and chemicals. This helps them last longer and work better. For example, in car electronics, they make parts stronger in tough conditions. By protecting circuit boards, conformal coatings help devices perform well and last longer.

Key Takeaways

Conformal coatings keep circuit boards safe from water, dirt, and chemicals. This helps electronics work well and last longer.
There are different coatings like acrylic, epoxy, silicone, polyurethane, and parylene. Each has its own good and bad points. Pick one that fits your needs.
Think about the environment and how to apply the coating. This helps your circuit board stay strong and work well in its surroundings.

Types of Conformal Coatings and Their Applications

Acrylic Conformal Coatings

Acrylic conformal coatings are popular because they are easy to use. You can apply them by spraying, dipping, or brushing. This makes them useful for many circuit board designs. They protect against moisture and dust, keeping boards working in tough conditions. Acrylic coatings also provide good electrical insulation.

But, acrylic coatings have some downsides. They don’t handle strong chemicals or high heat well. If your circuit board is in extreme conditions, you might need a different coating. Still, acrylic coatings are affordable and work well for general uses.

Epoxy Conformal Coatings

Epoxy conformal coatings are strong and resist chemicals. They create a hard layer that protects boards from damage and corrosion. These coatings are great for industries where boards face chemicals or stress.

Epoxy coatings also handle temperature changes well. For example:

HumiSeal UV500-2 survived 750 cycles of temperature changes from -40°C to 85°C without damage.
Tests from -40°C to 125°C showed epoxy coatings kept solder joints working, though some reduced joint lifespan.

However, epoxy coatings can crack under extreme stress. Their stiffness makes them less useful for flexible needs.

Silicone Conformal Coatings

Silicone conformal coatings are best for humid places. They block moisture and stop corrosion. Silicone lets water vapor pass through, so liquid water doesn’t build up on boards. This makes them perfect for wet or humid areas.

Silicone coatings also insulate electricity well. They stay strong across different temperatures and frequencies. This makes them good for aerospace and car uses where conditions change.

Silicone is more flexible than acrylics and epoxies. It reduces stress on parts, making them last longer. But, silicone costs more, which might be an issue for tight budgets.

Polyurethane Conformal Coatings

Polyurethane conformal coatings are tough and resist wear. Tests show their strength:

Test Methodology	What It Measures
Tabor Abrasion Drop Tests	How well it resists wear.
Cut-through Tests	How it handles cuts.
Puncture Tests	How it resists punctures.
Sward Hardness	How hard the coating is.
Custom Abrasion Test	How it handles wear on key board areas.

These coatings are great for protecting against physical damage. They also resist chemicals, keeping boards safe in harsh places.

However, polyurethane coatings can be harmful during use. Safety steps are needed when working with them. Their hardness also makes them less ideal for flexible uses.

Parylene Conformal Coatings

Parylene conformal coatings give the best protection for advanced boards. They are applied using a special process called chemical vapor deposition (CVD). This creates a thin, even layer that sticks at the molecular level. It covers even complex shapes completely.

Key benefits of parylene coatings include:

Excellent moisture and corrosion protection.
Strong electrical insulation.
Safe for sensitive uses like medical devices.
Long-lasting and reliable.

Parylene coatings are perfect for tiny electronics and high-frequency devices. They stop ionic movement in small parts, keeping boards working well in tough conditions. However, their special application process can make them more expensive.

Choosing the Right Conformal Coating for Your PCB Needs

Environmental Factors to Consider

When picking conformal coatings, think about your PCB's surroundings. Conditions like heat, moisture, and chemicals matter a lot. For example:

Acrylic coatings stop moisture but don’t resist chemicals well.
Silicone coatings handle wet places but wear out in rough spots.
Polyurethane coatings are tough but hard to fix later.

Testing for temperature and moisture shows why stable conditions are key. For instance:

Test Type	What It Measures
Water Absorption Test	Checks PCB weight change after moisture exposure to find water absorption.

Keeping the environment steady during coating stops problems like bubbles or peeling. This keeps your PCB strong, even in tough places.

Application Methods and Techniques

How you apply conformal coatings changes cost and performance. Two common ways are spraying and dipping. Each has good and bad points:

Method	Good Points	Bad Points
Spraying	Easy to do, works for tricky designs, low starting cost	Uneven coverage, more waste, needs masking, may need extra coats
Dipping	Fast process, even coverage, great for machines	Only works with thin coatings, needs steady conditions

Spraying is better for detailed PCB designs. Dipping gives even coverage for simple boards. Both need masking to keep some parts uncoated.

Cost, Availability, and Maintenance

Price and supply affect which coating you pick. Parylene coatings protect well but cost more due to special tools. Acrylic coatings are cheaper and easy to find, making them good for general use.

Maintenance matters too. Epoxy coatings are hard to remove, making repairs tricky. Silicone coatings are easier to fix but need more care in rough spots. Balancing price, supply, and upkeep helps you choose the best option.

Why LTPCBA Recommends High-Quality Conformal Coatings

LTPCBA knows how important it is to shield PCBs with top coatings. These coatings fight moisture, rust, and heat changes. They also make products last longer by reducing damage in hard conditions.

Benefit	What It Does
Better Resistance	Stops moisture, rust, and heat damage.
Longer Product Life	Cuts down damage in tough environments.
Strong Electrical Insulation	Prevents short circuits and lowers failure chances.
Saves Money	Fewer repairs or replacements needed due to longer-lasting boards.

With LTPCBA, you get expert help and advanced PCB services. We make sure your boards get the best care for your needs. Visit our website to learn how we can improve your PCB’s performance and durability.

Conformal coatings help protect circuit boards in different ways. Acrylic coatings are cheap and simple to use. Epoxy coatings are strong against chemicals and stress. Silicone coatings work well in wet places. Polyurethane coatings are tough and resist damage. Parylene coatings give the best protection for advanced electronics.

Think about the environment and how to apply the coating. This helps your PCB work well and last longer. LTPCBA offers expert advice and top-quality PCB services to fit your needs.

FAQ

What is the best conformal coating for humid places?

Silicone coatings are great for humid areas. They stop moisture and prevent rust, making them perfect for wet or tropical places.

Can conformal coatings be removed for fixing?

Yes, most coatings can be taken off. Acrylic coatings are the easiest to remove. Epoxy and parylene need special tools or chemicals to take off.

How do conformal coatings help PCBs last longer?

Coatings guard against water, dust, and chemicals. This stops rust and electrical problems, helping your PCB work well for a long time in tough conditions.