Conformal Coating for Electronics and Unmanned Systems

What is Conformal Coating?

A conformal coating for electronics is a thin protective layer applied to printed circuit boards (PCBs) and other electronic assemblies. It shields components from humidity, corrosion, and contaminants, preventing electrical failures in demanding operational conditions.

These coatings are typically applied using conformal coating spray, automated conformal coating machines, or manual brushing, depending on the application requirements. Many conformal coatings adhere to industry standards such as MIL-I-46058C* and IPC-CC-830C, ensuring reliability in mission-critical applications.

Applications of Conformal Coatings in Unmanned Systems

Unmanned systems rely on conformal coatings for PCB protection, as electronics in UAVs, UGVs, and marine drones need to operate in harsh conditions. Key applications include:

• Aerospace & UAV electronics – High-altitude UAVs and aerospace systems are exposed to extreme temperatures, UV radiation, and atmospheric moisture. Heat-resistant coatings and UV cure conformal coatings help protect sensitive electronics from thermal stress and oxidation. Silicone conformal coatings are commonly used in these applications due to their flexibility and durability in fluctuating environmental conditions.
• Maritime robotics – Electronics in unmanned surface vehicles (USV) and underwater vehicles (UUV) are constantly exposed to moisture, salt, and pressure variations. Conformal coatings for electronics applications in these systems must provide exceptional humidity protection and resistance to corrosion. While some coatings, such as parylene conformal coating, offer high moisture resistance, additional sealing methods like silicone encapsulants or potting may be necessary for full waterproofing.
• Autonomous ground vehicles – Unmanned ground systems operate in harsh terrains where dust, dirt, and humidity pose risks to electronic components. PCB corrosion protection is essential to prevent failure caused by environmental contaminants. Polyurethane conformal coatings and epoxy conformal coatings offer strong resistance against chemicals, moisture, and abrasion, ensuring long-term reliability in rugged environments.

Types of Conformal Coating

Several PCB coating types are available, each offering unique benefits depending on the application:

Acrylic conformal coating

Acrylic coatings are widely used due to their ease of application and fast-drying properties. They provide excellent moisture resistance and electrical insulation while remaining easy to remove for rework or repair. However, they offer limited chemical and abrasion resistance compared to other coatings.

Silicone conformal coating

Known for its high flexibility and thermal stability, silicone conformal coating is ideal for environments with extreme temperature fluctuations. It is commonly used in aerospace and automotive applications where components must endure continuous thermal cycling. Silicone coatings also provide excellent moisture protection but can be more challenging to remove for repairs.

Polyurethane conformal coating

These coatings offer superior chemical resistance, making them ideal for industrial and automotive electronics exposed to fuels, solvents, and harsh chemicals. Polyurethane conformal coatings form a durable barrier that protects against moisture and abrasion, though they are typically more difficult to remove than acrylic coatings.

Epoxy conformal coating

Epoxy conformal coatings create a rigid, high-strength protective layer that is highly resistant to physical damage and environmental stress. This makes them a good choice for applications where mechanical durability is critical. However, their lack of flexibility can be a drawback in applications where components experience vibration or thermal expansion.

Parylene conformal coating

Parylene is a thin film conformal coating applied via a vapor deposition process, ensuring uniform coverage even on complex geometries. It provides exceptional moisture, chemical, and dielectric protection, making it a top choice for medical, aerospace, and defense electronics. However, parylene conformal coating requires specialized equipment for application and is more expensive than other coating types.

Understanding the conformal coating process and selecting the right conformal coating material is essential to ensuring long-term durability and performance in unmanned systems.

Conformal Coating vs. Potting: Choosing the Right Protection

When comparing conformal coating vs. potting, key differences include:

• Conformal coatings provide a thin protective layer while maintaining flexibility and easy inspection.
• Potting fully encases components in resin, offering superior mechanical protection but making repairs difficult.

For unmanned systems, a combination of both methods may be used based on the environmental risks and maintenance requirements.

Challenges and Considerations in Conformal Coating

While conformal coatings offer significant benefits, certain challenges must be addressed:

• Conformal coating defects – Issues such as bubbles, cracks, and uneven thickness can affect performance.
• Adhesion testing – Ensuring proper adhesion and sealing is crucial for long-term reliability.
• Conformal coating thickness measurement – Maintaining an optimal thickness ensures balance between flexibility and protection.
• Conformal coating masking – Protecting sensitive components from coating overspray is essential for precision applications.

Application Methods and Best Practices

Applying conformal coating correctly is essential to ensuring effective protection and reliability of electronic assemblies. Various techniques are used depending on the coating type, production scale, and precision requirements. Below are the primary methods along with best practices for each.

Dip coating

Best for: High-volume production, uniform coverage.

Dip coating involves immersing the entire assembly into a bath of conformal coating material, ensuring complete and even coverage. It is ideal for large-scale production but requires careful masking of connectors and sensitive components to prevent unwanted coating deposition. Best practices include using controlled withdrawal speeds to avoid excessive thickness and ensuring proper ventilation for solvent-based coatings.

Spray coating (manual & automated)

Best for: Medium-to-large production, selective coverage.

Spray coating can be performed manually using aerosol sprays or with automated systems for high precision. It provides good control over coating thickness but requires masking of non-coated areas. Best practices include using consistent spray patterns, maintaining optimal nozzle distance, and ensuring proper drying between coats to prevent defects like bubbles or fisheyes.

Brush coating

Best for: Prototyping, repairs, small-scale applications.

Brush coating is a simple, cost-effective method used for touch-ups or selective coating applications. It allows precise control but is labor-intensive and prone to inconsistencies. Best practices include using high-quality brushes to minimize streaking, applying multiple thin layers rather than one thick layer, and working in a dust-free environment to prevent contamination.

Selective coating (automated robotic systems)

Best for: High-precision applications, reducing masking requirements.

Selective coating uses robotic dispensing systems to apply conformal coating only to designated areas, eliminating the need for extensive masking. It is commonly used in aerospace and automotive applications where precision is critical. Best practices include regular calibration of equipment, maintaining clean nozzles, and verifying coverage with UV inspection.

Vapor deposition (parylene coating)

Best for: High-performance coatings, uniform ultra-thin layers.

Parylene coatings are applied via a chemical vapor deposition (CVD) process, ensuring uniform and pinhole-free coverage even on complex geometries. This method provides excellent moisture and dielectric protection but requires specialized equipment and controlled conditions. Best practices include thorough surface preparation to enhance adhesion and verifying thickness using precision measurement tools.

Flow Coating

Best for: Large, flat assemblies, controlled thickness application.

Flow coating involves manually pouring or dripping coating material over a PCB and allowing it to spread evenly. It is useful for achieving consistent thickness but requires careful handling to prevent pooling or uneven distribution. Best practices include using controlled flow rates, working in a clean environment, and using appropriate viscosity coatings to enhance flow consistency.

Plasma Treatment (pre-coating surface preparation)

Best for: Improving adhesion, removing contaminants before coating.

Plasma treatment is often used as a pre-coating step to enhance adhesion by cleaning and activating PCB surfaces. This method is especially beneficial for challenging materials like PTFE or highly smooth surfaces. Best practices include selecting the appropriate gas mixture for treatment, maintaining controlled chamber conditions, and verifying adhesion strength post-treatment.

By selecting the right application method and following best practices, manufacturers can optimize conformal coating performance, reduce defects, and ensure long-term protection for electronics in harsh environments.

Industry Standards and Compliance for Conformal Coating

Conformal coatings must meet stringent industry standards to ensure they provide adequate protection and reliability for electronic assemblies. These standards define material properties, testing methods, and application requirements for coatings used in aerospace, military, automotive, medical, and industrial electronics.

Key conformal coating standards

Below is an overview of the most important standards governing conformal coatings:

Why compliance matters

1. Reliability in harsh environments – Ensures coatings provide sufficient protection against moisture, chemicals, and temperature fluctuations.
2. Regulatory approval – Many industries require coatings to meet specific standards for product certification and legal compliance.
3. Fire safety – UL94V-0 certification is crucial in applications where fire resistance is mandatory.
4. Environmental responsibility – RoHS and other eco-compliance standards help manufacturers meet sustainability goals.

How to Ensure Compliance

• Choose a Certified Coating – Look for products tested and approved under IPC-CC-830C, UL94V-0, or other applicable standards.
• Conduct Internal Testing – Perform adhesion, thickness measurement, and environmental stress tests to verify coating performance.
• Work with Certified Applicators – Ensure contract manufacturers and coating providers follow best practices and industry guidelines.

By selecting the right conformal coatings that meet these standards, manufacturers can enhance product durability, regulatory compliance, and overall system reliability.

Conformal Coating Removal and Rework

Conformal coating removal is necessary for repairs, modifications, or rework of electronic assemblies. The removal method depends on the coating type, thickness, and adhesion properties.

• Solvent removal – Acrylic and some polyurethane coatings can be dissolved using specialized solvents. Best practices include using chemical-resistant brushes, working in a ventilated area, and ensuring complete removal before reapplying a new coating.
• Mechanical removal – Epoxy and thick polyurethane coatings often require scraping, sanding, or micro-abrasion techniques. Care must be taken to avoid damaging PCB traces and components.
• Thermal removal – Some coatings, such as silicone, soften at high temperatures and can be peeled or scraped off. Heat application should be controlled to prevent damage to sensitive components.
• Plasma or laser ablation – For precision removal, plasma or laser techniques can selectively strip coatings without affecting the underlying circuitry. These methods are commonly used in aerospace and high-reliability applications.

After removal, proper cleaning and surface preparation are essential before reapplying a new conformal coating to ensure adhesion and long-term protection.

Conformal Coating for High-Reliability Electronics

Selecting the right conformal coating products and conformal coating services is crucial for optimizing unmanned system performance. From UV conformal coatings to plasma conformal coatings, advancements in dielectric coatings continue to push the boundaries of PCB protection in defense, aerospace, and autonomous technology sectors.

With robust circuit board coating solutions available from leading conformal coating companies, engineers can ensure their unmanned systems remain operational in the most challenging conditions.