Parylene for LEDs

LED Lifespan as Effected by UV Light

LEDs are engineered to deliver up to 100,000 hours of light in ideal lab settings. Yet, their endurance diminishes significantly in real-world applications due to factors like electrical interference, moisture, UV light and physical damage. To maximize efficiency, LEDs need safeguarding against these persistent threats. Of all the conformal coatings available to deliver reliable protection on an ongoing basis, none surpasses Parylene.

Parylene and Application with LEDs

Parylene stands out as the top choice for coating LEDs that need to function reliably round the clock, every day of the year, for many years. While safeguarding indoor LEDs like those under a kitchen clock or computer panel is relatively straightforward, challenges arise when protecting LEDs in more rigorous outdoor settings, especially those with continuous real-time use. These scenarios are becoming more common; LEDs are now frequently used in outdoor environments with tough conditions, demanding consistent component security to ensure performance aligns with product specifications.

Parylene significantly outperforms other conformal coatings. Although liquid coatings like acrylic, epoxy, silicone and urethane meet the protective needs of specific applications, Parylene excels in providing enduring protection for LED PCBs and electrical assemblies against corrosion, environmental exposure and UV light. Parylene offers unparalleled chemical barrier and moisture protection and is applied through a unique deposition process. This advanced application distinguishes Parylene from other conformal coatings, ensuring exceptional protection and reliability for LEDs in various operational environments.

Leveraging Parylene Deposition for Enhanced LED Protection

Other conformal coatings have specific LED applications that necessitate less robust protection. Liquid coatings like acrylic, silicone, epoxy and urethane typically use wet application techniques, which can add weight to LED assemblies due to their final consistency. The thick and uneven covering of assembly substrates from wet technologies reduces component performance and lifespan. Moreover, exposure to harsh environmental conditions and UV light exacerbates these issues.

Liquid coatings face several significant challenges when used for LEDs, including:

• Voids within the surface coatings, acting as conduits for moisture that can negatively impact PCB’s efficient performance.
• The weightiness of wet-application coatings in comparison to Parylene may damage LED components, disrupting their specialized operational features.
• Insufficient long-term UV resistance can significantly limit PCB protection when LEDs are utilized outdoors for lighting fixtures, traffic signals, transportation signage and similar applications.
• Continual maintenance for these LED applications can rapidly escalate, becoming very expensive.

The continuous advancement of Parylene types and technologies has resulted in the creation of Parylene compounds that exhibit significantly enhanced UV resistance compared to their predecessors. Unlike traditional methods involving dipping, painting or spraying, Parylene utilizes a chemical vapor deposition (CVD) process. This process enables the substance to bond with substrates in a gaseous form, facilitating thorough and uniform penetration into the surface of LED components. The remarkably small molecular size of Parylene guarantees a uniform coating that perfectly conforms to the shape and size of the elements it covers. In addition to the UV stability provided by Parylene HT,® using Parylene for LED coatings offers various advantages:

• Resistance to temperature extremes
• Ultra-thin, pinhole-free covering
• Considerable, reliable dielectric properties
• Effective component insulation
• Repels abrasive substances, chemicals, corrosive liquids and moisture
• Lightweight barrier protection without the significant dimension or mass of liquid coatings

The CVD process fosters molecular growth on and within substrate surfaces, allowing gaseous Parylene properties to permeate every crevice and encase delicate components securely.

Protection from UV Radiation and Temperature Extremes

Parylene coatings provide a uniform, lightweight layer that offers superior protection for LEDs. arylene HT, a UV and heat-resistant coating, offers reliability even in outdoor conditions. Despite its thin application (from 500 angstroms to 75 microns), Parylene outperforms other coatings and remains virtually undetectable on the final product. Concerns like yellowing or discoloration due to UV exposure are minimized with Parylene HT. While some surface discoloration may occur over time, Parylene effectively shields internal LED components from UV radiation, safeguarding against degradation and performance issues.

The use of Parylene HT enhances the efficiency, durability and longevity of LED lighting, making it more versatile in operation. To fully leverage Parylene’s benefits for UV-exposed LEDs, collaboration with coating specialists is key for optimal performance. SCS provides LED-coating methods that ensure UV stability and long-term protection, preserving the integrity of LED components without compromising Parylene’s protective properties.

SCS has developed a unique process to enhance UV stability using Parylene C or N, ensuring exceptional protection. Through accelerated UV testing, our process demonstrated superior UV resistance compared to traditional coatings like Parylene C and DOWSIL™ 1-2577, which showed significant yellowing. SCS’ approach proved to be the most effective in preventing UV damage, making it the preferred choice.

Conclusion

Even in the absence of constant UV exposure, LEDs need conformal coatings for prolonged functionality. The reliability of conformal coatings depends on the material and usage conditions. Outdoor LED performance is affected by UV light, which degrades efficiency over time. This deterioration worsens with prolonged exposure. Specialized processing and inspection procedures are necessary for conformal coatings if PCBs and related LED assemblies are to be used directly under UV light.

When comparing Parylene to other coating types like acrylic, epoxy, silicone and urethane, it is evident that the liquid coating methods they employ often lead to uneven, excessively thick, and viscous layers. These coatings provide only moderate protection, which may hinder LED performance, particularly with prolonged use. Moreover, prolonged exposure to UV light can cause significant harm to LED components treated with these substances, ultimately restricting their long-term functionality.

In this regard, while most types of Parylene generate better overall protection to UV radiation than liquid application coatings, they are also limited in the longer-term security they provide LEDs exposed to UV light. However, SCS Parylene HT has been formulated to ensure long-lasting, superior preservation of LED assemblies, supporting reliable performance in the longer-term.

Although many variants of Parylene offer superior UV protection compared to liquid coatings, they fall short in safeguarding LEDs from UV exposure in the long run. However, SCS Parylene HT has been developed to guarantee long-lasting, superior preservation of LED assemblies, supporting their sustained performance over time. To learn more about protecting LEDs with Parylene, contact SCS.