What types of materials can be coated in Parylene and how to avoid costly mistakes

The most popular question about Parylene: “Can my xxx be Parylene coated?”  The number of substrate surfaces that can be coated with parylene is plenty. In the table below a number of industrial applications that use Parylene conformal coatings are listed. The examples can be extended.

Examples of devices that make use of Parylene conformal coatings

Printed circuit boards Implantable devices Optical lenses
MEMs Valves Power Supplies
LEDs O-rings Backplanes
Catheters Tubing Photoelectric Cells
Stents Silicon Wafers Forceps
Magnets Keypads Test tubes
Paper Stoppers Probes
Needles Seals Fiber Optic Components
Sensors Mandrels Pace-makers
Ferrite Cores Molds Bobbins
Metallic Blocks Motor Assemblies And many more…

Substrate surface / Parylene interaction / Substrate surface preparation, interface cleanliness, surface energy

By Parylene CVD deposition it is possible to obtain stress-free and defect-free conformal coatings on almost all types of materials. Some examples of such coatings are shown in the Figure. (a) Sensors used in the automotive industry can be prone to high temperatures, hydrocarbons, and moisture. Such environments cause the sensors Aluminum contact pads to corrode quickly. Use of parylene on these pads protects them and is commonly employed. (b) Parylene is also used as a masking material in MEMS devices due to its capability to fill the crevices, in the image it fills under the undercut and acts as a spacer to produce 100 nm wide nanowires (inset). In that study, it forms interfaces with a polymeric resist, Silicon, Silicon Carbide and Platinum. In the figure (c and d) we see that the parylene can be applied to replace the glass packaging leading to a smaller dimension and weight in the package. Also, the parylene can be coated as a stack of layers combined with other thin layers such as SiO2 as shown in image c. The diversity in the applications and possibilities makes the Parylene a very attractive conformal coating.

Steps to follow before starting the deposition process:

To prevent delamination, pinholes, cracks, wrinkles, blisters and other types of thin film defects different types of surfaces require different surface preparations. We discuss some of the common types below as bullet points:

Example Parylene/Material systems:

While there are many conformal coating options available, the diversity in the applications and possibilities makes the Parylene a very attractive conformal coating choice.

About the Author: This is a guest post by Sean Horn, a VP at Parylene Conformal Coating / Diamond-MT.