Parylene Optical Properties
Sean Clancy, Ph.D. | September 3, 2020
With Parylene you always have a clear and accurate view due to its optical properties. Although the Parylene deposition process begins with white to off-white dimer powder, the result is a transparent coating that retains clarity and color throughout your product’s lifecycle.
Across myriad industries, Parylene types C, N, and F are used when optical qualities are critical to product applications. Optical lenses, fiber optic components, electro-optical components, and optical sensors are frequently coated with this thin polymeric film for protection from the environment.
Parylene has excellent transmission and, conversely, low optical absorption in the visible and near-infrared regions of the electromagnetic spectrum, which ensures desirable performance in these regions.
Parylene’s thin, transparent protection is particularly beneficial for light-emitting devices, as the colors of the emitted light and device efficiency are not affected. Therefore, Parylene proves useful for optical devices, cameras, and LED lights exposed to challenging outdoor environments.
Read about Parylene masking and Parylene removal
Refractive indices are an important consideration in many optical applications. These describe how much light changes in direction as it passes from one medium into another. Additionally, refractive indices help determine the dispersive power of prisms and the focusing power of lenses.
Specifically, the refractive index is the ratio of the speed of light in a vacuum compared to the speed of light in a material. Parylene N has a refractive index of 1.66, meaning that the speed of light in this Parylene type is 1.66 times slower than light in a vacuum.
Read about Parylene chemical resistance and Parylene biocompatibility.
With Parylene conformal coatings, you always have a clear and accurate view.
UV Light Interactions
Extended UV exposure in air degrades Parylene N, C, D, and after a more extended period, VT-4. If direct sunlight exposure is limited, the effects of the UV is not as detrimental. Both UV and oxygen must be present to raise any significant issues.
Although VT-4 is better than C and N in this regard, dimer material can cost three to five times more than C. Similarly, AF-4 is much more UV resistant than VT-4, but this dimer can cost up to 20 times more than C, with significantly more limited suppliers and availability.
Read Dr. Clancy’s blog posts on Parylene thickness and Parylene temperature range.
The Big Picture
Apart from the detrimental UV light interactions exhibited with the non-fluorinated types, Parylene films provide excellent optical properties and enhance the reliability of mission-critical applications, such as aerospace, scientific, and telecommunication components and integrated circuits. If your project specifications call for products that can retain color and clarity, Parylene is an excellent option.
Do you need help from an expert in selecting a polymer coating for your next project? We can assist with scalable Parylene coating equipment. Reach out to our team today for a consultation.
Sean Clancy, Ph.D.
View Dr. Clancy’s webinar, “Proven Methods for Achieving Advanced Product Performance and Protection From Corrosive Environments,” here.
Ryan is a 9-year veteran to the world of protecting electronics from harsh environments and a lover of all things technology.