Parylene Coating

What is Parylene Coating

Parylene is the abbreviation for the polymer group named poly (para-xylylene). These polymers consist of differently substituted para-xylylenes. The initial state for the coating is given by the so-called dimers. A dimer is a molecule composite which consists of two identical subunits, namely the monomers.

Advantages & Properties

Parylene coatings offer a wide range of benefits. Parylene coatings …

  • are perfectly conformal: that means that the coating is adapting also on complex substrate contours such as sharp edges or holes.
  • are „pinhole-free“, starting at layer thicknesses of about 0.5 microns.
  • are chemically insoluble and resistant to a wide range of chemicals.
  • exhibit very good barrier properties to moisture and chemicals.
  • own a high dielectric strength.
  • possess dry lubricating film properties (low friction coefficient).
  • are hydrophobic - contact angle of H2O between 92 ° and 98 °.
  • are transparent between 90 and 96 % in the range of the visible wavelength (depending on the type of parylene).
  • are biocompatible - The parylene types C and N can be certified according to USP Class VI, ISO 10993 and FDA.

Process Description

The following outlines the Parylene Coating system;

  1. The deposition takes place by polymerization through a vacuum assisted coating process, the so-called chemical vapor deposition – CVD.
  2.  The “dimer” (solid [2,2]-p-cyclophane), which is present in a powder-like shape, will be sublimated within the the vapourizer.
  3. The thermal decomposition of the relatively inert „dimer-gas“ is carried out using a pyrolysis tube with temperatures of about 650 °C, resulting in the formation of highly reactive monomers.
  4. The process pressure is dependent on the used dimer-type and the dimensions/construction of the deposition system - common values are between 0.02 and 0.1 mbar. Via diffusion the reactive monomers enter into the vacuum chamber in which the coating material is placed on a rotating frame.
  5. The reactive monomers preferably polymerize on cold surfaces, and form a thin layer of poly(para-xylylene) or rather Parylene. Since not all of the monomers polymerize inside the chamber, it is necessary to work with a cold trap which is installed behind the chamber to avoid a coating/damage of the vacuum pump. 

During the process, the trap can be easily filled with liquid nitrogen, so that the residual monomers will polymerize in the cold trap.

Types of Parylene

Parylene N - Basic Parylene Type

Parylene C - Most Common Parylene Type

Parylene D - Mechanical Properties

Parylene F-VT4 - Thermally Higher Load than D

Parylene F-AF4 - Highest Temperature Resistance

Applications

Electronics

PCBs

All kinds of sensors

Semiconductor Devices

Ferrite Cores

Permanent Magents

Medical Devices

Cannulas, Catheters

Biopsy Needles

Probes and Endoscopes

Ampoules / bags

Hearing Aids

Implants, Corona Stents

Aerospace

Navigation Electronics

Cockput Instruments

Satellite Electronics

Imaging Equipment

Radar / Detectors

Automotive

Pressure Sensors

Flow Sensors

Emission Sensors

Engine Electronics

Control Units

Rotors / Stators / Motors

Monitoring and Control System

Battery / Cell Systems

Radar / Detectors

LEDs

Electronic Billboards

Aviation / Automotive Lighting

Outdoor Lighting

Traffic Lights

Industrie

Seals

O-rings

Pipes

Bottles / Containers

Products

Parylene P6

Parylene 30

Parylene P120D

Parylene P260

Parylene P300