Different Types of Parylene

Parylene, a widely used term for Poly-para-xylylene, creates a protective plastic film when coated on substrate surfaces. This coating process is carried out using chemical vapor deposition (CVD) in a vacuum environment, where the gas is applied to specific substrate surfaces.

Parylene films offer remarkable versatility, protecting substrates with a reliable barrier against acids, caustic solutions, dust, water vapor, and various other pollutants. Their outstanding electrical insulation features low dielectric constant and high tensile strain. The coverage is devoid of pinholes, making it ideal for intricate coating of surfaces with crevices, exposed internal areas or sharp edges.

Parylene comes in various types such as N, C, D, Parylene HT®, and ParyFree®, each serving specific purposes with distinct chemical, electrical and physical characteristics. Tailored to different applications, Parylene conformal coatings can effectively range from 0.1 to 76 microns in thickness, surpassing the fineness of traditional liquid coatings.

Types of Parylene

Among the prominent Parylene types are:

Parylene N

Type N represents the foundational member of the poly-p-xylylene series, embodying a natural form characterized by linearity and high crystallinity. Each molecule is composed of a carbon-hydrogen pairing. When compared to other Parylene variants, Type N stands out for its low dielectric constant and dissipation values, making it ideal for high-frequency applications. Notably, its melting point of 420°C surpasses that of Types C and D. Type N excels in vacuum stability as a conformal coating, displaying minimal weight loss at elevated temperatures and low pressures.

Parylene C

Parylene C, a commonly used type for conformal coatings, is derived from dimer material and features a chlorine group in each repeat unit on its main-chain phenyl ring. Unlike Type N, Parylene C incorporates a chlorine atom instead of a hydrogen atom, offering exceptional protection against corrosive gases due to its low permeability to chemicals, moisture, and vapors. With high moisture resistance, Parylene C adheres rapidly to various substrate surfaces at room temperature through Parylene’s unique CVD process.

While its lower throw-capability minimizes crevice-penetration activity, Parylene C provides reliable coating protection when exposed to oxygen-rich atmospheres at 100°C for extended periods, such as 100,000 hours (equivalent to approximately a decade). Vacuum stability tests confirm Parylene C’s durability, with weight-loss performance rated at 0.12%, aligning with the stringent standards set for Type N (49.4°C/10-6 torr).

Parylene D

Types C and D stem from the same monomer. Unlike Type N, D’s structure deviates as it incorporates two chlorine atoms in lieu of two hydrogen atoms. Despite tolerating temperatures up to 125°C, D lacks the necessary biocompatibility for widespread application in medical devices. Parylene D provides efficient protective coating, enduring exposure at 134°C for extended periods under oxygen-rich environments, up to 100,000 hours.

Parylene HT

Parylene HT substitutes the alpha hydrogen atom of the N dimer with fluorine. This specific type of Parylene proves valuable for high-temperature applications (up to 450°C in the short term) and scenarios necessitating long-term UV stability. Notably, Parylene HT boasts the lowest coefficient of friction and dielectric constant, along with the highest penetrating ability among the various Parylene types.

ParyFree

ParyFree enhances Parylene N dimer by swapping hydrogen atoms with non-halogenated substitutes. This halogen-free variant upholds Parylene C’s top-notch barrier features and augments mechanical and electrical properties surpassing those of other commercially accessible Parylenes. ParyFree optimizes the crucial blend of barrier, electrical and mechanical properties to deliver robust shielding against moisture, water, corrosive solvents and gases, all while meeting the halogen-free standards of specific global industries.

Conclusion

In conclusion, Parylene coatings offer a range of protective solutions tailored to diverse applications, with types like Parylene N, C, D, Parylene HT, and ParyFree each serving specific purposes. These coatings provide exceptional barrier properties against various environmental factors, ensuring efficient protection of substrate surfaces. With characteristics like low dielectric constant, high vacuum stability, and precise coating application, Parylene coatings stand out as a reliable choice for industries requiring high-performance conformal coatings.