Parylene C, Parylene N, Parylene Electrical Properties, Parylene Mechanical Properties, Parylene Thermal Properties, Parylene, Gas Permeability, melting point, dielectric strength

Parylene Properties

Humans have used coatings to protect and enhance objects for thousands of years. The Egyptians mixed amber with oils to make protective varnishes.  Early cave dwellers sealed walls with earth pigments ground in egg whites.

Coatings today are highly engineering materials with a range of application options.  Designers must find materials with the properties that let them turn a need or idea into a tangible and reliable product.

The high-performance properties of parylene, combined with the way it is deposited, enable solutions that would otherwise not be possible. Parylene is a unique class of vapor deposited polymers. Its characteristics make it an enabling solution for precision applications demanding the highest levels of protection.  Parylene creates an unmatched barrier layer, it is truly conformal and it has a proven track record of use in the body for implants.  With typical thicknesses between 1 to 50 microns, parylene is pinhole free with excellent moisture, chemical, and dielectric barrier properties.

Understanding parylene’s properties is an important step in designing parylene into your process. The electrical, mechanical, thermal and barrier properties of parylene listed below.

 

Electrical Properties

Parylene is a material with exceptional electrical insulation properties that can be applied in a conformal thin film.  This unique combination allows parylene to be used as a precision dielectric layer in a variety of applications.

When compared to epoxy, silicones and urethane coatings, all parylene types have an extremely high dielectric strength.  Parylene N is a unique dielectric material because of the extremely low dissipation factor which changes only slightly with frequency.  The chlorine in parylene C increases the dielectric constant and dissipation factor when compared to parylene N.  

Parylene Properties, Parylene N, Parylene C, Parylene F, Parylene, dielectric strength, silicone, polyurethane, epoxies, acrylic, medical coating

Below are some highlighted applications that take advantage of parylene’s unique electrical properties and thin film deposition:

  • Capacitors- Protection against arc-over and corona discharge.
  • Protection on electrically sensitive devices.
  • Thin dielectric layer on neural probes and nueralstimulators.
  • Semiconductor wafer level test probes.
  • Magnets and ferrite cores.
  • A micro dielectric layer for micro transducers, MEMS, and micro-coaxial probes.

Electrical Properties

Dielectric Strength

Dielectric strength defines the maximum voltage required to produce a dielectric breakdown of the material.  The higher the dielectric strength of a material the better its quality as an insulator.

 

Volume Resistivity

Volume resistivity is the electrical resistance through a cube of insulating material. The higher the volume resistivity, the lower the leakage current and the less conductive the material is.

 

Surface Resistivity

Surface resistivity is the electrical resistance of the surface of an insulator material.  The higher the surface resistivity, the lower the leakage current and the less conductive the material is.

 

Dielectric Constant (k)

A ratio measuring the ability of a substance to store electrical energy in an electric field.

 

Dissipation Factor (tan δ)

A measure of a dielectric material’s tendency to absorb some of the AC energy from an electromagnetic (EM) field passing through the material.

 

Parylene C

220 V/micron at 25.4microns

5600 V/mil at  0.001”

 

8.8x1016 ohm-cm

at  23°C, 50% RH

 

1x1014 ohms

at 23°C, 50% Relative Humidity

 

60 Hz  3.15

1 KHz 3.10
1MHz 2.95

6 GHz 3.06 ‐ 3.10


 

60 Hz  0.020

1 KHz  0.019
1MHz  0.013


6 GHz  0.0002 ‐ 0.0010

 

Parylene N

276 V/micron at  25.4microns

7000 V/mil at  0.001”

 


1.4x1017 ohm-cm

at  23°C, 50% RH

 

1x1013 ohm

at 23°C, 50%  Relative Humidity

 

60 Hz  2.65
1 KHz  2.65
1MHz  2.65
6 GHz  2.46 ‐ 2.54

 

60 Hz  0.0002

1 KHz  0.0002
1MHz  0.0006


6 GHz  0.0021 ‐ 0.0028

 

Parylene F

276 V/micron at  25.4microns

7000 V/mil at  0.001”

 

1.1x1017 ohm-cm

at  23°C, 50% RH

 

4.7x1017 ohm

at 23°C, 50%  Relative Humidity

 

60 Hz  2.20
1 KHz  2.25
1MHz  2.42

 

60 Hz  0.0002


1 KHz  0.0002
1MHz  0.008

 

 

Barrier Properties

Parylene is an extremely effective moisture and chemical barrier layer that can be used to protect materials from an incompatible environment.  VSI is able to encapsulate medical devices, electronics and oxidative materials from their environment with a very thin and conformal parylene layer.

Parylene type C is typically selected as a barrier layer because the chemical structure allows for the best barrier properties and it has a faster deposition rate.  Because parylene is biocompatible and implantable, it has a long history of use examples in medical devices.  A layer of parylene can be used to create military-grade protection that is used to waterproof and ruggedize electronics for industrial and consumer products.  Parylene also has excellent chemical resistance.  It is resistance to almost every solvent, acid and alkaline chemistry commonly used.  This allows parylene to be used to protect parts that will encounter harsh chemical environments.    

To assist in designing parylene into your product, the tables below provide the gas permeability, water absorption, and chemical resistance data for parylene.    

Parylene Properties, Parylene N, Parylene C, Parylene F, Parylene, medical coatings, VSI Parylene, parylene material properties, moisture vapor transmission rate

Below are some highlighted applications that take advantage of parylene’s unique barrier properties and thin film deposition:

  • Stents, defibrillators, pacemakers and other devices permanently implanted into the body.
  • Sensors.
  • Cochlear and intraocular implants.
  • Electronics for space and aerospace applications.
  • Corrosion protection for metals.
  • Printed Circuit boards (PCB) and flex-circuits.
  • Protection for plastic and elastomeric materials from harmful environments.
  • Protective layer for 3D printed parts to improve compatibility with chemicals.
  • Power supplies.
  • LED in displays, marine lighting, harsh environment lighting and outdoor illumination.

Gas Permeability

Gas permeability is a material property that defines the penetration of a gas through a solid membrane.  A low gas permeability rate is very desirable for coatings that need to seal and encapsulate a part.

Parylene C is an excellent barrier.  Compared to epoxies, urethanes and silicones parylene has considerably better gas permeability.  The table below shows the gas permeability of parylene for common gases.

Gas permeability is expressed in the following units:  (amount of gas)(thickness of membrane) / (membrane area)(time)(differential pressure of gas).

Gas

Nitrogen (N2)

 

Oxygen (O2)

 

Carbon Dioxide (CO2)

 

Hydrogen (H2)

 

Parylene C

0.4  

at 25°C, (cc*mm)/(m2*day*atm)

 

2.8  

at 25°C, (cc*mm)/(m2*day*atm)

 

3.0  

at 25°C, (cc*mm)/(m2*day*atm)

 

43.3  

at 25°C, (cc*mm)/(m2*day*atm)


 

Parylene N

3.0  

at 25°C, (cc*mm)/(m2*day*atm

 

15.4  

at 25°C, (cc*mm)/(m2*day*atm)

 

84.3  

at 25°C, (cc*mm)/(m2*day*atm)

 

212.6  

at 25°C, (cc*mm)/(m2*day*atm)

 

Parylene F

 

16.7

at 25°C, (cc*mm)/(m2*day*atm)

 


 


 

 

Chemical Resistance

Parylene is insoluble in all common solvents, acids and alkalis used in processing and cleaning electronics.  The table below reports testing that was done on parylene test strips 12-35 microns thick.  The test strips were immersed in test liquids until equilibrium swelling was reached.   The percent thickness change was either be due to swelling or the solvent content of the film after surface drying. In no case was there a decrease in the original film thickness.  After the strips dried, they all returned to their original thickness.

This testing demonstrates how parylene reacts to different chemicals.  The minimal swelling and return to original thickness inindicate parylene’s resistance to the chemicals listed below.

Chemical

Inorganic Reagents

 

10% Hydrochloric

(Non-Oxidizing Acid)

 

37% Hydrochloric

(Non-Oxidizing Acid)

 

10% Sulfuric

(Non-Oxidizing Acid)

 

95-98% Sulfuric

(Non-Oxidizing Acid)

 

10% Nitric

(Oxidizing Acid)

 

71% Nitric

(Oxidizing Acid)

 

10% Chromic

(Oxidizing Acid)

 

74% Chromic

(Oxidizing Acid)

 

10% Sodium Hydroxide

(Base)

 

10% Ammonium Hydroxide

(Base)

 

100% De-Ionized Water

(Inert)

1

Organic Solvents

 

Isopropyl

(Alcohol)

 

Iso-Octane

(Aliphatic Hydrocarbon)

 

Pyridene

(Amine)

1

Xylene

(mixed)

 

Trichloroethylene

(TCE)

 

Chlorobenzene

(Chlorinated Aromatic)

 

O-Dichlorobenzene

(Chlorinated Aromatic)

 

Trichlorotrifluoroethane

(Fluorocarbon)

 

Acetone

(Ketone)

 

2,4-Pentanedione

(Ketone)

1

Parylene C

% Swelling

 

0.0% at 25°C

0.0% at 75°C

 

0.0% at 25°C

4.1% at 75°C


 

0.3% at 25°C

0.2% at 75°C


 

0.4% at 25°C

5.1% at 75°C

 

0.1% at 25°C

0.1% at 75°C

 

0.2% at 25°C

1.85% at 75°C

 

0.1% at 25°C

0.0% at 75°C

 

0.0% at 25°C

7.8% at 75°C

 

0.0% at 25°C

0.5% at 75°C

 

0.2% at 25°C

0.4% at 75°C

 

0.0% at 25°C

0.0% at 75°C

 


 

0.1% at 25°C

0.2% at 75°C

 

0.4% at 25°C

0.5% at 75°C

 

0.5% at 25°C

0.7% at 75°C

 

2.3% at 25°C

3.3% at 75°C

 

0.8% at 25°C

0.9% at 75°C

 

1.5% at 25°C

2.0% at 75°C

 

3.0% at 25°C

1.4% at 75°C

 

0.2% at 25°C

0.3% at 75°C

 

0.9% at 25°C

0.9% at 75°C

 

1.2% at 25°C

1.8% at 75°C

 

Parylene N

% Swelling

 


0.0% at 25°C

0.0% at 75°C

 

0.2% at 25°C

2.3% at 75°C

 

0.1% at 25°C

0.2% at 75°C

 

0.2% at 25°C

5.3% at 75°C

 

0.1% at 25°C

0.2% at 75°C

 

0.2% at 25°C

Became Brittle at 75°C

 

0.1% at 25°C

1.2% at 75°C

 

0.3% at 25°C

8.2% at 75°C

 

0.1% at 25°C

0.0% at 75°C

 

0.3% at 25°C

0.4% at 75°C

 

0.0% at 25°C

0.0% at 75°C

 


 

0.3% at 25°C

0.3 % at 75°C

 

0.2% at 25°C

0.3 % at 75°C

 

0.2% at 25°C

0.4% at 75°C

 

1.4% at 25°C

2.1% at 75°C

 

0.5% at 25°C

0.7% at 75°C

 

1.1% at 25°C

1.7% at 75°C

 

0.2% at 25°C

0.3% at 75°C

 

0.2% at 25°C

0.2% at 75°C

 

0.3% at 25°C

0.4% at 75°C

 

0.6% at 25°C

0.7% at 75°C

 

 

Mechanical Properties

Parylene is a crystalline polymer which results in generally high mechanical strength.  Parylene has a relatively high tensile and yield strength compared to other polymer coatings.  Parylene has a hardness higher than polyurethane and epoxy however it has the approximate hardness of human skin.  Parylene isn’t recommended to be used in applications with repeated abrasion with harder materials.

Using a thin layer of parylene for dry lubricity is one of the unique applications of parylene.  This use takes advantage of the low static and dynamic coefficient of friction and the ability to deposit molecule by molecule.

When we take a look at parylene’s surface energy, parylene is naturally hydrophobic.  This can be a benefit for many situations but be challenging for adhesion to other materials.  VSI Parylene is able to modify the parylene surface to promote adhesion to the parylene surface.  Contact us to learn more about this capability.  

Parylene Properties, Parylene N, Parylene C, Parylene F, Parylene, dry lubricity, catheters, silicone rubber sticky, teflon, urethane, glass, silicone rubber, VSI Parylene, parylene material properties, coefficient of friction

Below are some highlighted applications that take advantage of parylene’s mechanical properties:

  • Dry lubricity for silicone parts and silicone cables.
  • Dry lubricity for catheters, balloon catheters and guidewires.
  • Dry lubricity for o-rings, seals and gaskets
  • Encapsulating circuit boards and electronics to reduce the effects of vibration.
  • Add rigidity to a fragile component.

Mechanical Properties

Young's Modulus

The force is needed to stretch or compress a material. Stress/Strain.

 

Tensile Strength


The force required to pull a material to point where it will break.

 

Yield Strength


The stress at which permanent (plastic) deformation occurs.

 

% Elongation to Break


The ratio between the change in length and initial length that causes the material to break.

 

Elongation at Yield


The ratio between the increased length and initial length at the yield point.

 

Density


The mass per unit volume.

 

Hardness (Rockwell)

Rockwell hardness is a measure of the indentation resistance of a material. Testing is performed forcing a steel ball indentor into the surface of a material. The R scales tests between 10 and 60 kg.  

 

Coefficient of Friction


The coefficient of friction is the minimum force required to get an object to slide on a surface, divided by the forces pressing them together.  It is important to note that the difference in static and dynamic coefficient of friction is undetectable for parylene.

 

Parylene C

2.8 GPa

400,000 psi

 

68.9 MPa

10,000 psi

 

55.2 MPa
8,000 psi

 

20-200%


 

2.9%

 

1.289 g/cm3

80.5 lb/ft3

 

R80

 

0.29 static and dynamic

 

Parylene N

2.4 GPa
350,000 psi

 

48.3 MPa
7,000 psi

 

42.1 MPa

6,100 psi

 

20-250%

 

2.5%

 

1.11g/cm3
69.3 lb/ft3

 

R85

 

0.25 static and dynamic

 

Parylene F

3.0 GPa
435,000 psi

 

55 MPa
7,800 psi

 

52 MPa

7,600 psi

 

10-50%

 

2.4%

 

1.652 g/cm3

103.1 lb/ft3

 

R80

 

0.35 static

0.39 dynamic

 

 

Parylene Properties, Parylene N, Parylene C, Parylene F, Parylene, medical coatings, VSI Parylene, Wear Index, taber, urethanes, epoxies, high impact PVC, teflon

 

Thermal Properties

Parylene, like all polymers, has an ideal temperature operating range which is dependant on the application and environment.    At temperatures outside the ideal temperature operating range, parylene will start to become translucent or yellow and will become brittle.  

The operating range increases significantly if parylene can be used in the absence of air or in inert atmospheres.  In an oxygen-free environment, oxidative degeneration does not take place.  Degradation is due primarily to the thermal cleavage of carbon-carbon bonds.

If high temperature is a concern, VSI recommends every application is looked at and tested individually. The melting point of each parylene type defines an upper limit.  The table below gives guidelines for 1,000-hour use and continuous use.  VSI Parylene has a temperature and UV test chamber to test specific applications, contact us today to discuss testing.        

Parylene Properties, Parylene N, Parylene C, Parylene F, Parylene, medical coatings, VSI Parylene,parylene temperature rating, parylene temperature, vapor deposition process, conformal coat

On the other end of the temperature spectrum, parylene is outstanding in cryogenic applications. As an example, steel panels coated with parylene C that were chilled in liquid nitrogen to -160ºC withstood impacts of more than 100 in/lb.  Unsupported 2-mil films of parylene C were flexed 190 degrees six times a -165ºC before failure occurred.  At even lower temperatures, near absolute zero, tests show that parylene N provides the best electrical insulation of any known plastic.  Neither electrical or physical properties are noticeably affected by cycling from -270ºC to room temperature.  The cryogenic test results were published in volume 45: no. 14A “Modern Plastics Encyclopedia”.

Designers may also need to consider the coefficient of thermal expansion and thermal conductivity of parylene.  The table below provides data points for these properties.

Thermal Properties

Melting Point

 

Short-term Service Temperature

Recommended maximum temperature for 1,000 hours of use.

 

Continuous Service Temperature

Allowable temperature exposure for 10 years service life.

 

Linear Coefficient of Thermal Expansion

The relative change in length per degree temperature change.

 

Thermal Conductivity (k)

Thermal conductivity is a material property describing the ability to conduct heat.

 

Specific Heat (c)  

The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.

 

Parylene C

290ºC

554ºF

 

95ºC [203ºF]  in oxygen environments

265ºC [509ºF] in inert environments

 

80ºC [176ºF] in oxygen environments

230ºC [446ºF]in inert environments

 

35 ppm/ºC at 25ºC


 

0.084 (W/(m*K) at 25ºC

 

0.17 cal/(g* ºC)

at 20º C

 

Parylene N

420ºC

788ºF

 

115ºC [239ºF] in oxygen environments

350ºC [662ºF] in inert environments

 

60ºC [140ºF] in oxygen environments

220ºC [428ºF] in inert environments

 

69 ppm/ºC at 25ºC

 

0.126 (W/(m*K) at 25ºC

 

0.20 cal/(g* ºC)

at 20º C

 

Parylene F

435ºC

815ºF

 

250ºC [239ºF] in oxygen environments

 

200ºC [239ºF] in oxygen environments

 

45 ppm/ºC at 25ºC

 

0.1 (W/(m*K) at  25ºC

 

1.652 g/cm3

103.1 lb/ft3

 

 

Parylene Types

Parylene Properties, Parylene N, Parylene C, Parylene F, Parylene, medical coatings, VSI Parylene, penetrating power, vapor deposition process, conformal coat

Parylene is the name for a group of vapor-deposited poly(p-xylylene) polymers.  Within the parylene group are different types of organic coatings with a polycrystalline or linear structure. Below is a brief description of the various parylene types.

Parylene C

Parylene C is the most popular parylene type because it provides a combination of barrier and dielectric properties while also having cost and processing advantages.  

Parylene C is produced from the same raw material as parylene N but substitute a chlorine atom for one of the aromatic hydrogens.  This gives parylene C very low permeability for better protection from moisture, chemicals and corrosive gases.   Parylene C deposits much faster than other parylene types which allow a thicker layer to be applied with less machine time.

Parylene C is the best choice for:

  • Pinhole free barrier layers to electronics or materials from harsh environments.
  • Meeting IPC-CC-830 or MIL-I-46058C standards.
  • Encapsulating electronics to provide dielectric protection.
  • Implantable medical devices.

Parylene N

Parylene N is the base structure of the parylene group.  Parylene N has excellent dielectric properties. It has a very low dissipation factor, high dielectric strength, and a low dielectric constant that does not change with frequency.

Parylene N is more molecularly active than parylene C during the deposition process.  An advantage of the higher activity is increased crevice penetration, which allows parylene N to get farther into tubes, and small openings.  A disadvantage of the higher activity is slower deposition rates which increase the machine time and cost for thicker layers.

Parylene N is the best choice for:

  • Dry lubricity even when applied at very thin layers.
  • High frequency/RF applications because of its low dissipation factor at high frequencies.
  • Applications that require high penetration.

Parylene F (VT-4)

Parylene F fills a niche because it is capable of higher operating temperatures and is more resistant to UV than parylene C or parylene N.  Parylene F also has very good dielectric properties and good crevice penetration.  The chemical structure of Parylene F has four fluorine atoms on the aromatic carbons.  Parylene F has a slower deposition time and the raw material is more expensive.

VSI Parylene offers parylene F for applications that require the increased temperature and UV resistance parylene F offers.

Parylene D and Parylene AF4 (Parylene HT)

Parylene D and Parylene AF4 (Parylene HT) are two other parylene types that are available.

  • For most applications, parylene C is preferred over parylene D because parylene D has poor distribution in the deposition process.
  • Parylene AF4, also called Parylene HT, has the highest temperature and UV resistance of any parylene.  However, at the moment, the raw material price and long deposition time have made it hard for parylene AF4 to find viable commercial applications.

VSI Parylene is able to deposit parylene D and parylene AF4. We have found limited commercial demand and we look at applications on a case by case basis.  If you have an application that you think could benefit from one of these dimers, please contact us to discuss.  We look forward to being a resource to you.   

Not finding what you’re looking for?  Ask an Expert.