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PARYLENE PROPERTIES

Parylene Coating Properties:
Tables of Values, Types, & Technical Data Sheets

Introduction

Pinhole and defect-free Parylene coatings provide exceptional dielectric strength and superior resistance to chemicals and corrosion. Parylene is one of the best coatings for moisture impermeability, with complete coverage, even on complex substrates. Parylene's many benefits are due to the chemical deposition process and material properties. 

Parylene Coating Properties Overview

Parylene Electrical Properties

2024-parylene-properties-photosParylene-Electrical-Properties-01

As a film that coats conductive areas on electronics, Parylene is an excellent dielectric (electrical insulator) coating. Its lack of pinholes and defects enhances capabilities, but its fundamental composition defines Parylene's dielectric properties. 


As the table below indicates, Parylene's electrical properties are among the best of the conformal coatings.

Electrical Properties of Conformal Coatings
Parylene N Parylene C Acrylic Epoxy Silicone Urethane
Dielectric Strength (DC (V/mil) 7000 5600 1200 900-1000 1100-2000 1400-3000
Sheet Resistivity (Ω·cm) @ 23°C 50%RH 1.4x1017 6-8x1016 1013-14 1012-17 1015-16 1011-15
Dielectric Constant (60Hz) 2.65 3.15 3.0-4.0 3.5-5.0 2.7-3.1 5.3-7.8
Dielectric Constant (1KHz) 2.65 3.1 2.5-5 3.5-4.5 2.6-2.7 5.4-7.6
Dielectric Constant (1MHz) 2.65 2.95 3.0-4.0 3.3-4.0 2.6-2.7 4.2-5.2
Dielectric Loss (tan δ) (60Hz) 0.0002 0.02 0.2-0.4 0.002-0.01 0.001-0.007 0.015-0.05
Dielectric Loss (tan δ) (1KHz) 0.0002 0.019 0.02-0.04 0.002-0.02 0.001-0.005 0.04-0.06
Dielectric Loss (tan δ) (1MHz) 0.0006 0.013 0.035-0.056 0.03-0.05 0.001-0.002 0.05-0.07
Dielectric Loss (tan δ) (1GHz) — < 0.007 — — — —

The volume resistivity and dissipation factors of various Parylene types are detailed below.

Volume Resistivity and Dissipation Factors of Parylene Types
Parylene N Parylene C Parylene F (VT-4)
Volume Resistivity, Ω·cm, 23 °C,50% RH 1.4 x 1017 8.8 x 1016 1.1 x 1017
Dissipation Factor (tan δ) (60Hz) 0.0002 0.020 0.0002
Dissipation Factor (tan δ) (1KHz) 0.0002 0.019 0.0002
Dissipation Factor (tan δ) (1MHz) 0.0006 0.013 0.0008
Dissipation Factor (tan δ) (6GHz) 0.0021 - 0.0028 0.0002 - 0.0010 —
Parylene's breakdown voltage is a function of film thickness, allowing for the possibility of fine-tuning electricity-blocking properties. Additionally, each Parylene type has different dielectric properties, ensuring a suitable Parylene for virtually any operating environment. 

Parylene Mechanical Properties

2024-parylene-properties-photosParylene-Physical-Properties-01

Parylene has a relatively high yield and tensile strength compared to other polymer coatings, and wear resistance is substantial. It is a crystalline polymer, resulting in mostly high mechanical strength. 

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.

Young's Modulus
Material Young's Modulus Tensile Strength
Polyester 7.1x105 psi MD 29,000 psi MD
Polyimide 3.6x105 psi ~29,000 psi
Parylene C 4.6x105 psi 10,153 psi
Parylene N 3.5x105 psi 6,526 psi

Taber Wear Index

Taber wear index values of Parylene  C, N, an epoxy, and a urethane are listed below. 

Taber Wear Index
Material Taber Wear Index
Parylene C 44
Parylene N 9.7
Epoxy 38
Urethane 55-67

Impact Resistance

Impact resistance of two Parylene types, Epoxy, and Urethane can be found below.

Impact Resistance
Material Impact Resistance (kg·cm)
Parylene C >85
Parylene N >85
Epoxy 35
Urethane 23

Although Parylenes have good abrasion resistance, they will still be susceptible to scratches because they are polymer films. However, housing a Parylene-coated assembly in an enclosure will ensure that abrasion will be negligible. Additionally, using a thicker coating should extend the product's life. 

Parylene Barrier Properties

2024-parylene-properties-photosParylene-Barrier-Properties-01

Parylene coatings are of high purity, so any moisture absorbed or permeated will not contribute to chemical corrosion or become absorbed. Furthermore, the water vapor transmission rates of the Parylenes are among the lowest of polymers. 

The table below compares the gas permeability and WVTR (Water Vapor Transfer Rate) of Parylene with other conformal coating types:

Gas Permeability and WVTR of Conformal Coating Types
Polymer Gas Permeability at 25 °C, (cc·mm)/ (m2·day·atm) WVTR
(g·mm)/ (m2·day)
N2 O2 CO2 H2 H2S SO2 CI2
Parylene C 0.4 2.8 3.0 43.3 5.1 4.3 0.1 0.08
Parylene N 3.0 15.4 84.3 212.6 313 745 29.2 0.59
Parylene D 1.8 12.6 5.1 - 0.6 1.9 0.2 0.09
Parylene F (VT-4) - 16.7 - - - - - 0.28
Epoxy (ER) 1.6 4 3.1 43.3 - - - 0.94
Polyurethane (UR) 31.5 78.7 1.81 - - - - 0.93
Silicone (SR) - 19,685 118,110 17,717 - - - -

Corrosion Resistance Properties

2024-parylene-properties-photosCorrosion-Resistance-Properties-01

In addition to exhibiting low WVTR (Water Vapor Transfer Rate) and gas permeability, Parylene performs particularly well as a barrier to corrosion due to its ability to minimize the influence of these factors:

  • Liquid water uptake – Parylene absorbs minimal water
  • Coating porosity – Parylene coatings are pore and pinhole-free
  • Ionic permeability – Salts do not pass through the coating easily  
 The table below demonstrates the resistance of different polymers to 0.9% saline solution, including Parylene C.
Resistance of Different Polymers to 0.9% Saline Solution
Polymer Coating Method Layer Thickness (μm) Time Until Total Breakdown
Parylene C CVD 25 > 30 Days
Epoxy (ER) Dip Coating 100 ± 25 6 Hours
Polyurethane (UR) Dip Coating 100 ± 12.5 6 Hours
Silicone (SR) Dip Coating 75 ± 12.5 58 Hours
Teflon Spraying 75 6 Hours

 

Parylene Optical Properties

2024-parylene-properties-photosParylene-Optical-Properties-01

Transparent in appearance, Parylene coatings protect optical lenses, sensors, fiber optic components, electro-optical components, and related products. The films have excellent transmission and low absorption in the near-infrared and visible regions of the electromagnetic spectrum, allowing for desirable performance. 

If exposed to UV (Ultraviolet Light/Radiation) in air or oxygenated atmospheres for extended periods, Parylene N, C, and, much later, VT-4 will degrade, which means measures must be taken to limit direct sunlight exposure, or limiting the amount of oxygen near the coating. VT-4 does better with UV exposure than N and C, but dimer (starting material) can cost at least three to five times more than C. 

Index of Refraction

Parylene's refraction index is compared with other materials below.

Index of Refraction of Parylene and Other Materials
Material Index of Refraction
Air 1.0003
Liquid Water 1.333
Parylene C 1.602
Parylene N 1.585
Polyimide 1.70
Polyester 1.640-1.670

 

Parylene Thermal Properties

2024-parylene-properties-photosParylene-Thermal-Properties-01The temperature stability values for the parylenes are collected in the table below and are based on industry literature.

Temperature Stability Values for Parylene Types
Parylene-Type Long-Term Temperature Limit (°C) Duration = ~10+ Years) Short-Term Temperature Limit (°C) Duration = ~1 Month Melting Point Temperature (Tm)
Parylene N 60 95 420
Parylene C 80 115 290
Parylene D 100 135 380
Parylene VT-4 200 250 –
Parylene AF-4 350 450 >500

 

Coefficient of Linear Expansion
Material Coefficient of Linear Expansion
FR-4

1.4x10-5/ °C

1.2x10-5/ °C

7.0x10-5/ °C
Polyester 1.7x10-5/ °C
Polyimide 2.0x10-5/ °C
Parylene C 3.5x10-5/ °C
Parylene F 3.6x10-5/ °C
Parylene N 6.9x10-5/ °C

 

Specific Heat Capacity
Material Specific Heat
FR-4 Epoxy Glass no Copper

0.28 cal/g·°C
Polyester 0.28 cal/g·°C
Polyimide 0.26 cal/g·°C
Parylene C 0.17 cal/g·°C
Parylene F 0.25 cal/g·°C
Parylene N 0.20 cal/g·°C

 

Thermal Conductivity
Material Specific Heat
FR-4 (through-plane) 0.29 - 0.34
FR-4 (in-plane) 0.81 - 1.06
Polyester 0.15
Polyimide 0.12
Parylene C 0.08
Parylene F 0.10
Parylene N 0.12

 

Flammability

Both Parylenes C and VT-4 contain halogens with C having chlorine (Cl) and VT-4 having fluorine (F), both of which function as flame retardants. Therefore, these materials self-extinguish almost immediately after a flame is removed. Flammability is typically tested using UL 94 HB for horizontal burn and UL 94 V for vertical burn.

Dry Lubricity

Cold Temperatures

Although oxidation and degradation aren't concerns at these lower temperatures, polymer materials, including Parylene, cool down, they become stiffer, less flexible, and more likely to incur physical damage. However, Parylene films can be flexed multiple times (up to 6 to 9) when cooled down to liquid nitrogen temperatures, while most other coatings will crack on the first or second flex.

2024-parylene-properties-photosDry-Lubricity-01Parylene is a low-friction coating that allows easy sliding and is a dry lubricant. The friction coefficient for Parylene coatings is low, ranging from 0.25 to 0.33, so their lubricity is close to Teflon™. Due to this slickness, Parylene is used in medical device applications as a high-flexibility, low-friction coating that resists contamination and discoloration. 

Biocompatibility

2024-parylene-properties-photosBiocompatibility-01Parylene conforms to the USP Class VI and ISO 10993 standards and is biocompatible. Parylene is also non-toxic and physiologically non-reactive.

Parylene Types

chemical structure of Parylene dimerParylene 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 a hydrocarbon polymer entirely. 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, such as VT-4, are more challenging to manufacture and expensive but benefit from higher ultraviolet (UV) and thermal resistance than N and C. This is due to a greater difficulty oxidizing CH2 connections in the VT-4 polymer since they were replaced with CF2 groups.

Parylene starting materials polymerize through a free radical  addition mechanism, that doesn’t create reaction byproducts. 

Types of Parylene Compared

chemical structures of the common Parylene polymers

Parylene C Properties

Both Parylenes C and VT-4 contain halogens with C having chlorine (Cl) and VT-4 having fluorine (F), both of which function as flame retardants. Therefore, these materials self-extinguish almost immediately after a flame is removed. Flammability is typically tested using UL 94 HB for horizontal burn and UL 94 V for vertical burn.

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

Parylene N is halogen-free and is a unique dielectric material because of a low dissipation factor which changes only slightly with frequency. 

The Parylene Process for Each Parylene Type

Each Parylene type's deposition process is affected by its chemical composition. For example, N and VT-4 deposit much more slowly than C. Additionally, it can be more challenging to control a Parylene type's coating uniformity and dispersion within the deposition chamber. Finally, different starter materials have varying costs, availability, and temperature requirements for the deposition chamber. 

Relative Properties of the More Common Parylenes
Properties ← Decreasing – Parylene Type – Increasing →
Raw Material Cost N C D VT-4 AF-4
Deposition Rate AF-4 N VT-4 C D
Temperature & UV Exposure Performance N C D VT-4 AF-4
Moisture Barrier Performance VT-4 N AF-4 D C
Crevice Penetration D C VT-4 N AF-4
Dielectric Properties C D N VT-4 AF-4

 

Download Parylene Datasheet

2024-parylene-properties-photosParylene-Datasheet-01Want to understand if Parylene conformal coating specifications properties are suitable for your project? Download the HZO Parylene datasheet; no contact information is required. Meanwhile, please contact us if you would like to speak to a member of our Applications Engineering team. 

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