How to Select the Right Conformal Coating
It’s Not as Difficult as You Think!
Selecting a conformal coating for your printed circuit board (PCB) might initially feel like navigating a maze of technical terms, standards, and chemical options. However, the process becomes much more approachable once you understand the core considerations. Conformal coatings play a critical role in extending the life of your electronics, protecting them from moisture, dust, corrosion, and other environmental stressors, so it is important to get it right. The key to making the right decision lies in asking the right questions early and evaluating all relevant factors systematically.
The earlier a conformal coating is considered in your product development, the better the outcome. Making this decision during the design phase ensures that the PCB layout and component placement support the chosen coating type and application method.
Step 1: Understanding the Application
One of the first things to determine is the intended application of the PCB. The environment in which the product will be used and the industry it serves will directly affect which coatings are suitable. For example, boards intended for aerospace or defence applications will often need to meet stringent military specifications. If the PCB operates at high voltage, coatings with a high Comparative Tracking Index (CTI) or those compliant with standards such as IEC 60664-3 are essential to minimise risk. Similarly, if fire safety is a concern, coatings that comply with flammability standards like UL94-V0 or EN45545-2 should be prioritised. Boards used in LED lighting or displays require coatings that are optically clear to ensure light output is not compromised. These first considerations can ensure that a coating meets the necessary performance, safety and regulatory requirements specific to its end-use.
Step 2: Evaluating the Operating Environment
Once the application requirements are defined, the next consideration is the operational environment. Environmental stressors such as temperature fluctuations, chemical exposure, moisture, and mechanical abrasion all influence coating selection. Most conformal coatings perform well in temperatures ranging from -40°C to 125°C, but extreme applications may demand materials with broader thermal stability. In industrial settings, the board may be exposed to aggressive solvents, oils, or acids. In these cases, chemically resistant coatings, often based on silicone or urethane, may be required. For applications exposed to salt spray or high humidity, the coating must form a robust barrier against moisture ingress. It’s important to remember that conformal coatings are designed to resist water, not completely block - they are not waterproof. If full immersion protection is necessary, a different approach such as potting or encapsulation should be considered.
Step 3: Considering Board Composition and Layout
After assessing the external environment, it is equally important to evaluate the PCB’s own composition. Compatibility between the coating material and the board’s substrates, components, and adhesives can significantly affect long-term reliability. The interaction between the coating and surface finishes or component housings should be examined to avoid unintended reactions or adhesion issues. Silicones RTVs or thermal pastes, for example, can act as a barrier between coating the substrate, which can inhibit adhesion.
Step 4: Assessing the Need for Reworkability
Another factor that often determines the suitability of a coating is the likelihood of rework. In many electronics applications, especially during prototyping or in repairable field units, access to components for re-soldering or replacement is essential. In such cases, coatings that can be removed without damaging the underlying board (most commonly acrylic-based) are preferred. These coatings offer the benefit of reversibility, allowing engineers to make changes or corrections without scrapping the entire board. On the other hand, coatings like silicones and urethanes offer superior protection but are significantly more difficult to remove and reapply, making them more suitable for applications where rework is unlikely or undesirable.
Step 5: Environmental and Sustainability Considerations
Environmental impact and regulatory compliance are increasingly influential factors in coating selection. With global emphasis on sustainability, selecting coatings that are low in volatile organic compounds (VOCs) or that comply with REACH, RoHS, and other environmental regulations can simplify production and improve a company's sustainability. In high-volume manufacturing environments, minimal waste disposal and hazardous emissions can lead to long-term cost savings and reduced compliance burdens.
Extra Consideration: Choosing the Right Application Method
Finally, even the most carefully selected conformal coating can underperform, or completely fail, if it is applied incorrectly. Whilst the application method is secondary to getting the coating right, the method of application should match both the type of coating and the design of the PCB. To be effective, every coating must be applied in strict accordance with the manufacturer’s Technical Data Sheet (TDS), using the appropriate equipment and following all recommended safety procedures. In short, if it is not applied properly, it will not deliver the intended benefits.
Conclusion: Talk to the Experts Early
Selecting the right conformal coating involves more than just picking a product from a catalogue. It’s a process of matching your coating to your board’s function, its exposure to physical and chemical stress, the materials it interacts with, and the practicalities of repair and sustainability. By following the five steps outlined, you can navigate the decision with far greater ease. By incorporating coating considerations early in the design phase, you can avoid costly redesigns, ensure compliance with industry standards, and increase product longevity.
If you're still unsure about the best coating for your needs, you’re not alone. Many successful applications begin with a conversation. Our team of experts can guide you through coating selection and application processes tailored to your specific requirements. We encourage you to reach out (early and often) so that together we can ensure your PCB is protected with the most suitable coating, ensuring your electronics perform better and last longer.
Need some answers to the points above? Talk to us.
At Chiltern Connections Ltd, protective coatings aren’t just something we do, they’re what we specialise in. With over 35 years of experience, we have built a reputation for delivering high-quality, reliable coating solutions across multiple industries. Our 15,000 sq. ft. facility is fully equipped with dedicated areas for conformal, conductive, potting and encapsulation coatings, ensuring precision and efficiency in every project.
We take quality and safety seriously, holding both ISO 9001 and ISO 45001 certifications, guaranteeing that our processes meet the highest industry standards.
By outsourcing your protective coatings to us, you eliminate the hassle of managing materials, equipment, compliance, and quality control in-house. We take care of everything, so you don’t have to.
Still not sure? We’d love to show you around! Book a visit to our facility, see our operations in action, and have a chat over a cup of tea (and biscuits).