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 application with each type having its own unique electrical and physical properties. Parylene F is used in 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.
- Most common Parylene type
- Useful combination of properties for most types of applications
- Extremely low permeability to moisture, chemicals, and corrosive gasses
- Average crevice penetration activity
- Deposits onto substrates faster than Parylene N
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 a unique vacuum stability, and has proven very usefulness 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.
- Highest dielectric strength
- Dielectric constant does not vary with changes in frequency
- Best selection where greater coating protection is required
- Commonly used in high frequency applications
- Most often used on elastomers/rubbers for lubricity
- Removes tackiness
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.
- Greatest thermal stability compared to C and N
- Maintains physical strength and electrical properties at higher temperatures
- Lowest crevice penetration activity
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.
Learn more about Relative 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.
Learn more about Thermal Properties.
Parylene displays excellent dielectric strength, is a dielectric constant and has a consistent dissipation factor.
Learn more about Electrical Properties.
Physical & Mechanical Properties
Parylene is unmatched when it comes to tensile strength, yield strength and elongation, coefficient of friction and hardness.
Learn more about Physical & Mechanical Properties.
Due to the physical properties of Parylene and the method of deposition, the film is pin-hole free and provides an excellent barrier to both liquids and gasses. The gas and moisture vapor permeability characteristics far exceed that of liquid coatings.
Learn more about Barrier Properties.
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:
- Absorption: Parylene has good absorption, which means that different types of light can interact with the coating without impacting appearance. Under almost all circumstances, parylene coating is colorless.
- Clarity and Transparency: One of parylene's most important properties is clarity. Different application processes will impact clarity, but for the most part, parylene is reliably clear at any level of thickness and does not interfere with visibility. Parylene coating is clear and colorless. This transparency is particularly crucial for sensitive applications--for example, over gallery-level artwork or interactive displays. Although clear, the coating remains strong and reliable, making it a perfect choice for projects of all shapes and sizes.
- Light Interaction: Since parylene is often used in combination with light--for example, to protect LED systems--it is important to note that refraction indexes may change depending on temperature and method of deposition.
- UV resistance: When combined, oxygen and high levels of UV light can be damaging to parylene coating. However, under controlled circumstances, parylene can offer certain levels of UV resistance.
Learn more about Optical Properties.
Advanced Coating performs ongoing and thorough testing of the Parylene types and their performance. Detailed documentation is available upon request.