HZO produces pinhole-free and ultra-thin Parylene coatings for electronics within drones and robotics, providing exceptional dielectric strength and superior resistance to chemicals and corrosion.
Parylene coatings’ superior moisture impermeability ensures complete coverage, even on complex substrates. These advantages stem from Parylene’s chemical deposition process and material characteristics.
Parylene Coating Properties Overview
Parylene Electrical Properties
For electronics, Parylene serves as an excellent dielectric (electrical insulator) coating. Its performance is enhanced by the lack of imperfections, while its fundamental composition defines its dielectric properties.
The table below showcases Parylene’s electrical properties among conformal coatings.
The volume resistivity and dissipation factors of various Parylene types are detailed below.
Parylene’s breakdown voltage is a function of film thickness, allowing for the possibility of fine-tuning electricity-blocking properties. Each Parylene type offers different dielectric properties, ensuring suitability for diverse operating environments.
Parylene Mechanical Properties
Compared to other polymer coatings, Parylene demonstrates high yield and tensile strength, with substantial wear resistance. Its crystalline structure contributes to mechanical robustness.
Young’s Modulus
The table below shows Young’s Modulus and Tensile Strength values for Parylenes C and N, as well as a polyester and a polyimide.
Taber Wear Index
Taber wear index values of Parylene C, N, an epoxy, and a urethane are listed below.
Impact Resistance
Impact resistance of two Parylene types, Epoxy, and Urethane can be found below.
While Parylenes resist abrasion well, they remain susceptible to scratches as polymer films. Housing Parylene-coated assemblies in enclosures can minimize abrasion. Thicker coatings may also extend product lifespan.
Parylene Barrier Properties
Parylene coatings’ high purity prevents moisture absorption from contributing to chemical corrosion. Their water vapor transmission rates rank among the lowest for polymers.
The table below compares the gas permeability and WVTR (Water Vapor Transfer Rate) of Parylene with other conformal coating types.
Corrosion Resistance Properties
Parylene excels as a barrier to corrosion by minimizing liquid water uptake, coating porosity, and ionic permeability.
The table below demonstrates the resistance of different polymers to 0.9% saline solution, including Parylene C.
Parylene Optical Properties
Transparent in appearance, Parylene coatings protect optical lenses, sensors, fiber optic components, electro-optical components, and related products. The films transmit excellently and absorb minimally in near-infrared and visible electromagnetic spectrum regions.
Extended UV exposure in air or oxygenated atmospheres degrades Parylene N, C, and later, VT-4. Limiting direct sunlight or oxygen near the coating can mitigate this. VT-4 outperforms N and C in UV resistance, but its starting material costs significantly more.
Index of Refraction
Parylene’s refraction index is compared with other materials below.
Parylene Thermal Properties
The temperature stability values for the parylenes are collected in the table below and are based on industry literature.
Flammability
Parylenes C and VT-4 contain halogens (chlorine and fluorine respectively) that act as flame retardants, allowing quick self-extinguishing after flame removal. UL 94 HB and UL 94 V tests typically assess flammability.
Dry Lubricity
Cold Temperatures
At lower temperatures, Parylene becomes stiffer and less flexible, like other polymers. However, Parylene films can be flexed multiple times at liquid nitrogen temperatures, while most coatings crack on initial flexing.
Parylene’s low friction coefficient (0.25 to 0.33) makes it an effective dry lubricant, comparable to Teflon™. This property suits medical device applications requiring flexibility, low friction, and resistance to contamination and discoloration.
Biocompatibility
Parylene meets USP Class VI and ISO 10993 standards for biocompatibility. It’s non-toxic and physiologically non-reactive.
The types of biocompatibility-related testing that Parylene has passed are shown in the table below.
Parylene Types
Parylene coatings come in several types, including Parylene C, N, and F (VT-4) and high-purity. No sodium, ammonium, or chloride ions are generated from or inherent in the coatings.
Parylene N is purely a hydrocarbon polymer. Parylene C is identical to N except for chlorine atoms covalently bonded along the polymer chain. However, these chlorine atoms are not easily ionized or ionic.
Fluorinated dimers like VT-4 offer greater UV and thermal resistance than N and C, but are costlier to manufacture. VT-4’s CF2 groups replace CH2 connections, increasing oxidation resistance.
Parylene starting materials polymerize through free radical addition, producing no reaction byproducts.
Types of Parylene Compared
Parylene C Properties
Both Parylenes C and VT-4 contain flame-retardant halogens (chlorine and fluorine), and so these materials self-extinguish almost immediately after a flame is removed. UL 94 HB and UL 94 V tests assess flammability.
Parylene F Properties
Parylene F (VT-4) is free from bromine and chlorine halogens and contains fluorine. It exhibits the highest resistance to heat and UV when compared to C and N.
Parylene N Properties
Halogen-free Parylene N offers unique dielectric properties with a low, frequency-stable dissipation factor.
The Parylene Process for Each Parylene Type
Chemical composition affects each type’s deposition process. For example, N and VT-4 deposit slower than C.
Additionally, it can be more challenging to control a Parylene type’s coating uniformity and dispersion within the deposition chamber.
Starting materials differ in cost, availability, and temperature requirements for deposition.
Relative Properties of More Common Parylenes
