Today’s electronics are deployed in increasingly demanding environments - in aircraft, medical devices, agtech applications and industrial infrastructure. In these unforgiving conditions, sensitive circuitry faces a barrage of threats. Moisture, dust, chemicals, extreme temperatures, and vibration can all take their toll, leading to system failures, costly replacements, and frustrated customers.
What is conformal coating?
Conformal coating is a nearly invisible chemical layer that acts like armour for printed-circuit boards (PCBs), shielding them from environmental hazards that could impair their performance.
Conformal coating is widely used across a variety of sectors, from consumer electronics to performance-critical industrial settings. They ensure the long-term durability and compliance of circuit boards, helping to prevent failures that can cost money and even endanger lives.
While these coatings can be microns-thin, their application is a sophisticated science, demanding expert process controls and specialised equipment to get right.
So, whether you’re thinking about outsourcing or planning to manage your coating requirements in-house, understanding the highly controlled, multi-step conformal coating process is key to making the right manufacturing decisions.
Conformal coating machinery at work in ESCATEC's Malaysian plant
What are the key steps of an automated conformal coating process?
Step 1: Clean your boards
The first rule of conformal coating?
If the board isn’t clean, your coating won’t stay in place.
Contaminants like flux residues, oils, and dust particles can prevent the coating from bonding properly. This can lead to defects like delamination, pinholes and other issues. That’s why cleaning should be done using specialist solvents, followed by Dyne testing to confirm the correct surface energy.
Cleaning methods typically include:
- Water-based multi-step or ultrasonic cleaning systems combined with cleaning agents.
- Gloved handling post-clean to prevent recontamination.
- Dyne pen testing to meet the surface energy thresholds required for coating adhesion.
Cleaning is aligned with IPC guidelines, including IPC-CH-65B, and should form a documented step in quality assurance protocols.
Skipping or rushing this phase can undermine everything that follows. Preparation should be treated as a critical quality control checkpoint—not just a formality.
Step 2: Precision masking – define protected zones
Not all parts of a PCB should be coated.
Components like connectors, switches, sensor interfaces, and test points must remain exposed to ensure proper functionality. If coating is accidentally applied to these areas, it can cause electrical failures, poor signal contact, or mechanical issues - capillary action can draw coating fluid into unwanted zones.
To prevent this, precision masking is essential. This may be done manually using masking tape, latex, or custom silicone boots—some of which can be 3D-printed to fit specific components. Manual masking is flexible but time-consuming and prone to human error.
More advanced setups use digital masking, where “do-not-coat” zones can be programed into the machine. In this case, the system automatically avoids those areas, improving accuracy and reducing labour.
Where capillary action may occur a method of applying a gel barrier prior to the coating material can physically block coating intrusion. Together, these techniques ensure effective, targeted protection and support selective coating strategies crucial to maintaining PCB function.
Step 3: Choose the right materials – not all coatings are created equal
Choosing the right coating material is about more than cost or ease of use.
Different materials offer different levels of protection based on environmental conditions, performance and compliance requirements:
- Acrylic coating (AR): Easy to apply and rework, with good moisture resistance and dielectric strength. Ideal for general use but limited chemical resistance.
- Urethane coating (UR): Strong resistance to chemicals and abrasion. Less reworkable but suited for automotive and industrial settings.
- Silicone coatings (SR): Excellent thermal flexibility and resilience in high-humidity environments.
- Epoxies (ER): Very hard and resistant to moisture and chemicals, but brittle and difficult to remove.
- Parylene coating (XY): Vapour-deposited for uniform protection in extreme conditions—often used in aerospace, medical, and defence applications.
Material selection should consider:
- Operating environment.
- Temperature range.
- Chemical exposure.
- Vibration/mechanical stress.
- Dust/particulates.
- UV exposure.
- Rework or repair requirements.
- Cost constraints and regulatory standards.
Conformal coatings are selected to balance these factors, guided by IPC-CC-830C and industry-specific durability standards.
Bear in mind medical device conformal coating may require different application standards compared to electronics present in other devices. For more information you can read our guide to medical device electronics ruggedisation.
Step 4: Control the variables
Once the coating is selected, tight control over environmental and process variables is essential to ensure a consistent, defect-free result.
Critical variables for acrylic applications include:
- Viscosity: A 1°C shift can cause up to 10% change, affecting application quality.
- Temperature and humidity: Both influence curing and coverage.
- Storage: UV-sensitive coatings must be stored under the correct light and humidity conditions.
- Nozzle maintenance: Regular purging prevents blockages and maintains consistent flow.
Conformal coating machinery typically feature:
- Multiple nozzle types for narrow and wide spray paths.
- Programmed motion profiles for consistent application.
- Real-time controls to manage flow rate and pressure.
The goal is a uniform coating thickness across every batch - measured, documented, and validated to meet quality and compliance expectations.
Step 5: Automated precision at scale
Automation allows for high-volume, repeatable coating performance.
Boards can be mounted into bespoke or universal carriers and moved beneath robotic spray heads. Each PCB design requires a custom programme defining nozzle height, width, speed, and motion paths. Universal carriers offer flexibility for varied board sizes without the cost of custom tooling.
Because many coating compounds are flammable, particularly during application and drying, the process is typically enclosed and requires ATEX-rated extraction. This ensures compliance with health and safety standards and maintains a controlled application environment.
Step 6: Curing & inspection
After application, the coating must be cured to achieve its protective properties.
Curing methods depend on the coating type:
- Air drying: Common for acrylic and polyurethane; requires 12–24 hours in controlled airflow.
- Thermal curing: Used for epoxies and silicones; accelerates hardening via oven heating.
- UV curing: For photoreactive coatings; fast and efficient in high-speed environments.
- Dual-cure systems: Combine UV and secondary methods to reach shadowed areas.
Curing conditions are tightly managed to avoid issues like pooling, uneven thickness, or incomplete polymerisation.
Final inspection involves:
- UV light inspection to check for coverage gaps or pooling.
- Conformance to IPC-A-610 and IPC-CC-830C standards.
- Documentation of inspection results as part of the batch quality record.
This inspection stage ensures every board meets defined acceptance criteria before integration into assemblies.
Why outsourcing conformal coating makes sense
Setting up a conformal coating capability from scratch requires:
- ATEX-compliant extraction.
- Trained specialists with IPC certifications.
- Health & safety infrastructure for handling hazardous solvents.
- Precision masking, jigs, and programming capability.
- Continuous validation and inspection against IPC and customer standards.
Outsourcing this process to a qualified electronics manufacturing partner enables access to all of this - without the capital expense, risk, or complexity of running it in-house.
It’s a cost-effective way to guarantee quality and protect your PCBs, while reducing the time and overhead of managing another specialised process internally.
Wrapping it up – smart protection for products that last
Conformal coating isn’t just a protective measure—it’s a product quality guarantee. But getting it right takes more than just a spray gun and a clean room.
For OEMs building complete assemblies—from mechatronic sub-systems to sealed enclosures—outsourcing to a manufacturing partner who can integrate conformal coating into the broader PCB assembly and test process helps accelerate builds, reduce handling risks, and improve overall production efficiency.
If "built to last" is part of your brand promise, then partnering with an EMS provider equipped with advanced technology, trained coating technicians, and robust process control is how you ensure that promise is delivered.
Choose a partner who prioritises precision, compliance, and efficiency - at every layer.
