Parylene is the generic name for a unique series of polymers based on paraxylene. Unlike other more conventional types of conformal coatings, Parylene does not have any liquid phase and is applied at ambient temperature through a vacuum vapor deposition process without traditional curing time.
The three most common types of Parylene used in industrial applications are Parylene C, Parylene N, and Parylene D. These types are the obvious choice for 95% of all Parylene applications with each type having its own unique electrical and physical properties.
Parylene F is used in a few select applications where substrates are exposed to relatively higher temperatures. Type F is the costliest Parylene material available in the market and less commonly required.
Parylene C is highly resistant to corrosive gasses, moisture, vapor, and various chemicals. The coating can protect products for upwards of 10 years in extreme environments. Because of these characteristics, Parylene C is used for most products that need a conformal coating for protection.
Parylene N is a common and widely used conformal coating. Often considered a basic type of coating because there are many applications of the product. Parylene N has a melting point of 420°C (or 788°F), has unique vacuum stability, and has proven very useful in applications of high frequency. If you need to protect a difficult surface full of cracks, crevices, and tricky topography, then Parylene N is right for the job.
Parylene D and C have similar characteristics. However, Parylene D has a slightly higher temperature tolerance. This coating provides reliable assembly protection at 100°C in oxygen-dominated areas.
Parylene possesses several valuable properties that set the material apart from other conformal coatings.
Parylene provides superior mechanical protection and corrosion resistance at thicknesses utilized for conformal coating applications compared to epoxy and polyurethane hardness.
The unique structure of parylene coatings grant them many useful properties, but the thermal properties are among the most efficient--simply because the ability to withstand temperature extremes is crucial in countless applications. The coefficients of thermal expansion of the Parylene are similar to epoxies and Parylene is capable of withstanding exposure to cryogenic temperatures.
Parylene displays excellent dielectric strength, is a dielectric constant and has a consistent dissipation factor.
Parylene is unmatched when it comes to tensile strength, yield strength, and elongation, coefficient of friction, and hardness.
Due to the physical properties of Parylene and the method of deposition, the film is pinhole free and provides an excellent barrier to both liquids and gasses. The gas and moisture vapor permeability characteristics far exceed that of liquid coatings.
Parylene exhibits very little absorption of light and is therefore transparent and colorless. If a substrate is used outdoors and repeatedly exposed to direct sunlight, it is recommended to apply UV protection on top of Parylene.
Here's a closer look at parylene's optical properties:
Advanced Coating performs ongoing and thorough testing of the Parylene types and their performance. Detailed documentation is available upon request.