Protecting LEDs with Parylene

LEDs are gradually replacing all other types of lighting. As they move out of consumer electronics and into general purpose applications, the demands on the technology are shifting. It is relatively easy to keep an LED safe when it is mounted in the front panel of a computer or hidden under a cover on an alarm clock. Protecting it from round-the-clock exposure to the elements year-round presents a greater challenge.

One of the fundamental problems with LED technology is that LEDs are not particularly rugged in and of themselves. While many are rated for 100,000 hours of life, the inherent nature of an LED’s design means that they are unable to achieve this type of longevity when they are being exposed to real world situations. LEDs are sensitive to moisture, to electrical interference and to physical damage. Their internal light generating components and the plastic shells that cover them are also extremely sensitive to ultraviolet radiation. Organic LEDs are particularly prone to degradation.

While LED prices are constantly dropping, leaving them uncovered and exposed and just planning on replacing them as they fail is not a practical option. Replacing light bulbs or florescent tubes is a manageable challenge. Climbing up 100 feet to replace one of two million LEDs in a multi-color display is much less so. To ensure LEDs achieve their maximum lifespan, it is crucial to protect them. The ideal approach is to apply a conformal coating to shield the LED. This protective layer acts as a barrier against external factors. While liquid conformal coatings such as acrylic, urethane, silicone or epoxy offer excellent performance in various conditions, they come with inherent limitations that may render them unsuitable for LED applications.

1. Liquid coatings can be relatively thick and heavy when applied. Especially in settings that contain multiple LEDs, they can require changes to a product’s design and underlying support structure to accommodate heft and bulk.
2. When applied in thinner and lighter coats, liquids can frequently end up forming pinholes or uneven areas that fail to truly protect the LEDs they are supposed to cover.
3. Some liquid coatings can absorb or diffract the light coming out of the LEDs, changing the device’s optical performance. Given that LED light output still lags behind other technologies, losing light to a coating is rarely an acceptable option.

Parylene conformal coating is frequently the best choice for protecting LEDs and assemblies containing them. Its vapor-based deposition method eliminates the challenges inherent in using liquid-based coating compounds and its chemical properties add additional benefits.

Why Parylene?

Parylene’s first benefit comes from its unique deposition method. Since it deposits as a vapor, it creates a coat that touches everything that air can touch. It also touches everything evenly. This means that it creates a truly conformal coat with no pinholes.

Parylene stands out as a highly effective conformal coating compound renowned for its superior dielectric and moisture-resistant properties. This exceptional coating shields LEDs from signal interference, fog and water damage. Moreover, Parylene serves as a remarkable chemical insulator, mitigating the risk of corrosion. Notably, it operates efficiently at minimal thicknesses, often eliminating the need for redesigning coated items.

Parylene also provides a degree of UV protection for the LEDs. Simply coating them helps to prevent their internal components from light degradation. However, certain types of Parylene are, in and of themselves, prone to gradual color change due to UV exposure. Depending on the product’s intended life, Parylene may be stable enough for this to not be an issue, since it can typically last years without a visible color shift. However, certain types of Parylene have even longer life and can be used in those situations where color shift is not an option. Parylene HT® exhibits remarkable stability when subjected to UV exposure. It has successfully undergone industry-standard testing for 2,000 hours without any alteration in optical clarity due to UV exposure.

Ultimately, Parylene stands out as the optimal option for coating and safeguarding LEDs and LED assemblies. With its remarkable thinness and weightlessness, coupled with its all-encompassing protection against a multitude of environmental risks, no other coating rivals its effectiveness.