Conformal Coatings - Selection guide

How to Select the Right Conformal Coating

Introduction to Conformal Coatings

A conformal coating is a thin protective film designed to safeguard electronic assemblies from corrosion and environmental hazards in harsh operating conditions. The term “conformal” refers to its ability to conform precisely to the complex contours of the surface it covers. This coating offers several advantages, including protection from debris and dust infiltration, enhancing corrosion resistance, extending product warranties, and increasing overall reliability and safety. In essence, applying a conformal coating effectively prolongs the longevity and durability of electronic assemblies.

One of the main advantages of conformal coatings is their dielectric properties. These coatings exhibit excellent insulation resistance, effectively protecting electronic components and assemblies from electrical failures. Another significant advantage is moisture resistance, which serves as a crucial defense against moisture ingress, preventing potential damage and electrical failures in humid or damp environments. Additionally, the breakdown voltage characteristic plays a pivotal role in protecting the component from high voltages and electrical stresses. Finally, the flexibility of the coating endows the substrate with enhanced mechanical resilience, enabling it to better withstand external stresses and environmental fluctuations without deforming, cracking, or delaminating.

In summary, the notable dielectric properties and flexibility of conformal coatings combine to create a robust protective barrier, ensuring the longevity and optimal performance of electronic components in diverse and demanding applications.

30 days of exposure in an environment with H2S, SO2, and Cl2

Exposure results without Conformal coating
Figure 1a. Exposure results without Conformal Coating
Exposure results with Conformal Coating
Figure 1b) Exposure results with Conformal Coating

Different types of conformal coatings

Acrylic – Acrylic-based coatings like Loctite Stycast PC 62 represent the largest market share of conformal coatings. These coatings are formulated from single components and provide superior moisture resistance properties, making them highly suitable for protecting electronic assemblies in challenging environments. The widespread choice of acrylic-based coatings can be attributed to their ease of use, short cure time, and reworkability/repairability. Acrylic-based coatings are most often used in Engine Control Units (ECUs), Avionics, and communication equipment.

Polyurethane – Polyurethane-based coatings have excellent chemical resistance, rendering them highly effective in countering the effects of compounds such as salt spray and noxious gas. Available in both one-part and two-part systems, these coatings are easy to apply. Compared to other conformal coatings, polyurethane-based coatings like Loctite Stycast PC 18M do have a lengthier curing time. Reworkability is a notable advantage of these coatings, and they are commonly used in demanding environments with applications that include industrial controls, marine electronics, and chemical processes.

Silicone – Silicone-based conformal coatings are uniquely characterized by their exceptional high-temperature performance. Due to this characteristic, they are suitable for industrial mining equipment, electronics with temperatures greater than 150°C, and underhood components in the automotive industry. Silicone-based conformal coatings like Loctite SI 5293 offer reasonable moisture protection while remaining reworkable and repairable. They are solvent-free, yielding a 100% solid content and good solvent resistance. Moreover, these coatings incorporate flexible elastomers, enhancing their flexibility. This adaptability allows the coating to accommodate mechanical stresses and temperature fluctuations without compromising its integrity.

UV-Based – UV Based conformal coatings are primarily selected for their short cure time, which occurs within a matter of seconds. This expedited curing process reduces the cycle time while providing increased temperature performance to the coated components. UV Based coatings like Loctite Stycast PC 40-UMF exhibit excellent resistance to moisture and chemicals while also having high flexibility and abrasion resistance. One of the main advantages of this type of coating is that it is environmentally friendly, as it contains no Volatile Organic Compounds (VOCs) or solvents. Like Silicone Coatings, it is 100% solid content. Due to the short cure time, UV Based conformal coatings are suitable for high-volume applications.

Rubber-Based – Ruber-based conformal coatings represent a class of single-component coatings with excellent moisture resistance and low Moisture Vapor Permeability (MVP). Like other conformal coatings, they are easy to repair/rework, have a short cure time, and have excellent adhesion to various substrates. The characteristic that distinguishes rubber-based coatings is their superb flexibility and thermal-mechanical properties. Specifically, their low Coefficient of Thermal Expansion (CTE) and Glass Transition Temperature (Tg) enable the components to effectively withstand thermal shock, enhancing overall performance and reliability. This quality makes rubber-based coatings particularly well-suited for applications where temperature fluctuations pose a challenge, preserving functionality and integrity even in demanding environments.

Conformal Coating Selector Guide

Conformal coating selector guide for acrylic, urethane, uv, silicone, and rubber coatings
Figure 2. Conformal Coating Selector Table


In summary, conformal coatings are thin, protective films that safeguard electronic assemblies from corrosion and environmental hazards in harsh conditions. They conform precisely to the surface, providing advantages like protection from debris, enhanced corrosion resistance, extended warranties, and improved reliability and safety. The coatings offer excellent dielectric properties, insulation resistance, and moisture resistance, protecting against electrical failures and moisture ingress. Their flexibility ensures mechanical resilience, withstanding external stresses without deformation or delamination. There are multiple options to choose from, including acrylic, urethane, uv, silicone, or rubber-based, and each has specific properties beneficial to different applications. Overall, conformal coatings provide a robust barrier, ensuring long-lasting and optimal performance of electronic components in diverse applications.

Choosing the right conformal coating is critical for improving protection and reliability in electronic devices so an application-specific assessment should be conducted. Contact us and our application engineers and in-house coating experts will help you out with product selection for your application requirements.

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