PCB Conformal Coating 101: Everything You Need to Know
- Harshit Shah
- 2 days ago
- 7 min read
Electronics today are expected to survive in tough conditions—inside medical devices, aircraft, outdoor lighting systems, or factory floors. While the components on a circuit board do the real work, it’s often the layer you do not see that keeps everything running smoothly.
That layer is a conformal coating. It’s a transparent, protective film applied over a circuit board that helps prevent damage from moisture, dust, chemicals, and temperature changes. Think of it as a breathable raincoat for electronics. It does not interfere with performance, but it keeps the board protected and dependable.
In this guide, we explore everything you need to know about PCB conformal coating—what it is, where it’s used, how it’s applied, and why it’s an important part of reliable electronics manufacturing.
Table of Contents
What Is Conformal Coating in PCB Assembly?
A conformal coating is a lightweight protective film applied to circuit boards and components to shield them from environmental exposure. It forms a flexible, non-conductive shield that protects the board from moisture, corrosion, dirt, and chemical exposure.
This coating adapts to the shape and structure of the board, making it a preferred method for enhancing the long-term performance of sensitive electronics. At A2Z, conformal coating services in the USA are a key offering to help protect assemblies from harsh environments.
Why Is Conformal Coating Important for PCBs?
Without a protective layer, circuit boards are exposed to the environment they operate. That exposure can cause corrosion, short circuits, or complete failure. Conformal coating helps prevent these issues by:
Blocking moisture and humidity
Providing resistance to chemicals and salt spray
Preventing dust or particles from creating short circuits
Reducing wear from temperature changes and vibrations
In short, it supports the reliability and longevity of electronic products in real-world conditions.
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Industries That Rely on Conformal Coating
Many industries rely on printed circuit board conformal coating to ensure reliability and protection in challenging operating conditions.
Electronics used in medical devices require added protection to function reliably in cleanroom conditions and areas with high humidity.
Aerospace and defence systems face vibration, altitude shifts, and extreme temperatures.
Automotive components operate under the hood and outdoors
Outdoor lighting and LED drivers need to resist water, UV rays, and dust.
Industrial machines are exposed to chemicals, movement, and heat
These sectors trust conformal coating to maintain device function in demanding environments.
Types of Conformal Coatings for PCBs
Several conformal coating types are available, each with its performance strengths:
Acrylic Coatings
Acrylic coatings are among the most popular choices because they are easy to apply, cost-effective, and simple to remove when needed. They offer solid protection against moisture and general contaminants. Acrylic coatings also dry quickly and have good dielectric properties, making them suitable for many commercial and consumer electronics.
Silicone Conformal Coating
Silicone coatings are well known for their flexibility and ability to withstand a wide temperature range. They provide excellent resistance to moisture, vibration, and thermal cycling. Because of this, silicone conformal coating is often used to waterproof PCB boards or to protect electronics exposed to outdoor and automotive environments.
Urethane Coatings
Urethane coatings, sometimes called polyurethane coatings, are valued for their outstanding chemical resistance. They are commonly used in industrial applications where circuit boards might be exposed to solvents, fuels, or corrosive gases. Urethane coatings provide a strong protective barrier, but can be more challenging to remove during rework.
Epoxy Coatings
Epoxy coatings are extremely tough and mechanically strong, providing excellent protection against physical impact and harsh environments. They also deliver good resistance to moisture and chemicals.
However, epoxy coatings are more rigid than other options, which can make them less suitable for applications involving vibration or frequent thermal expansion. Additionally, they are difficult to remove once cured.
Parylene Coatings
Parylene coatings are applied through a vapour deposition process, resulting in a very thin, uniform coating that conforms perfectly to the entire surface of the PCB. This makes parylene coatings ideal for highly sensitive applications such as medical devices, aerospace electronics, and military equipment.
They provide excellent barrier protection against moisture, chemicals, and electrical interference. Parylene coatings are also known for their exceptional dielectric properties.
Each conformal coating material serves different operating conditions, and the right choice depends on your application.
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Conformal Coating Selection: Key Considerations
Selecting the right conformal coating for circuit boards depends on various factors:
Environmental exposure
If the circuit will face high humidity, chemical exposure, dust, or significant temperature variations, you will need a coating that offers strong protection in those conditions. For example, silicone conformal coating provides excellent moisture resistance, while urethane coatings excel in chemical-heavy environments.
In outdoor applications, coatings that resist UV radiation and thermal cycling are also valuable.
Repair and Rework needs
Some applications require regular maintenance or updates, making it important to select a coating that can be removed easily without damaging the underlying components. Acrylic coatings are known for being easy to rework, while epoxy and parylene coatings are more permanent and difficult to remove. Consider how often you may need to access the board for inspection or repair when making your choice.
Coating thickness requirements
Different conformal coating types offer varying levels of protection at different thicknesses. Thicker coatings generally provide more physical and chemical protection but may add weight or occupy more space, which is a consideration in compact or weight-sensitive designs such as aerospace and medical devices.
Additionally, thicker coatings may impact heat dissipation, so thermal management must also be evaluated.
Application method
The method used to apply the coating influences both the cost and consistency of protection. Manual methods such as brushing or spraying may be used for small batches or selective coverage.
For larger production volumes or when high precision is required, automated systems such as selective coating equipment or vapor deposition processes for parylene coatings ensure uniform and repeatable results.
Regulatory and Industry Standards
In certain industries, such as aerospace, automotive, or medical devices, specific standards must be met for conformal coating for electronics. Compliance with standards like IPC CC 830 or MIL I 46058C is often required. The choice of coating must align with these standards to ensure product reliability and regulatory approval.
Cost and Production Scalability
Finally, your budget and production volume play a role in selection. While Parylene coatings offer premium performance, they are more expensive and require specialised equipment. Acrylic and silicone coatings offer excellent performance at a lower cost and are better suited for high-volume production.
As a PCB assembly company, we guide clients through the selection process to ensure the best fit for their needs and compliance standards.
How to Apply Conformal Coating to a PCB?
There are several ways to apply conformal coating to a board, depending on the design and production needs:
Brush coating – Brush coating is suitable for small areas or manual touch-ups on the PCB Board.
Spray coating – Common and effective for uniform coverage.
Dip coating – PCB Boards are submerged, ideal for full and consistent layers.
Selective coating – Automated systems apply coating only to required areas
Vapour deposition – Used mainly for Parylene, creating a very thin and even layer
Each technique must be paired with proper masking to avoid coating parts like connectors or test pads.
Steps to Measure Conformal Coating Thickness
Proper coating thickness is important for performance. Too much may cause issues with fit or weight, and too little may not provide enough protection. Common methods to measure thickness include:
Wet film gauges are used during application
Wet film gauges are used during the application process to provide an immediate measurement of the coating thickness while the film is still wet. This helps operators adjust the amount of material being applied in real time to ensure even coverage across the PCB surface.
Micrometres or callipers after curing
Micrometres or callipers are commonly used after the coating has fully cured to verify the final thickness of the dry film. This method provides a direct measurement and ensures that the cured coating meets the required specifications for protection and performance.
Ultrasonic testing for non-contact precision
Ultrasonic testing is a non-contact method that uses sound waves to accurately measure the thickness of conformal coating for circuit boards. It is especially useful for delicate or irregularly shaped boards where physical measurement tools may not be practical.
Optical inspection in large volume production
Optical inspection systems use advanced imaging and software to measure coating thickness across multiple boards in a production run. This method provides fast, repeatable, and highly accurate results, making it ideal for quality control in the PCB manufacturing process, especially in high-volume production environments.
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Conformal Coating Testing and Standards
To ensure quality and consistency, several industry standards apply to conformal coating for circuit boards:
IPC-CC-830 – It outlines the standard guidelines for conformal coating materials and their proper application on circuit boards.
MIL-I-46058C – This standard defines military-grade performance characteristics.
UL746E – It assures flammability and electrical safety standards.
At A2Z Electronics LLC, we follow these benchmarks to deliver high-reliability conformal coating services across critical applications.
Conclusion
PCB conformal coating plays a key role in protecting electronic assemblies from the elements. By using the right coating and applying it properly, you help ensure the long-term reliability and performance of your devices. From medical systems to defence electronics, conformal coatings allow circuits to do their job—day after day, no matter the conditions.
At A2Z Electronics LLC, we use advanced methods to apply and test conformal coating so every product is protected from the inside out.
Looking for expert guidance on PCB conformal coating for your next project? Contact us today and let us help you assemble electronics that last.
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