Parylene and FAQs

Frequently Asked Questions about Parylene

What is Parylene?

Parylene is the generic name for a polymer series based on Poly-para-xylylene. Applied by vapour deposition process at room temperature this unique polymer creates an ultra-thin film highly lubricious and protective conformal coating.

Parylene coatings conform to MIL-I-46058 Type XY, IPC-CC-830B and USP Class VI, and ISO 10993 approved for use as a medical biocompatible and implantable material.

What is the Parylene Coating process?

Parylene Coating process image

Parylene is applied at room temperature with specialized vacuum deposition equipment that permits control of the coating rate and thickness.

The deposition process takes place at the molecular level as the chemical, in a dimer form, is first converted into a gas under vacuum and heat; then it is pyrolized to cleave the dimer; and finally the monomer is deposited as a clear polymer film on all exposed surfaces in the deposition chamber.

The single coating builds up one molecule at a time, encapsulating any and all exposed surfaces. The material is applied at rates of 1 to 2 µm per hour. Coating thicknesses from 0.1 to 76 µm can be applied in a single operation.

Parylene will conform to any surface that is stable in a vacuum environment, regardless of the complexity of the geometry.

Parylene is applied in a gaseous state, so there is no risk for bridging, spotting or pooling as can occur with a liquid conformal coating.

What is the typical coating thickness?

Typical coating thickness for lubricity of metal and plastic substrates is 3 to 5µm, while for silicone and rubber components 1 µm will significantly reduce tackiness.

For chemical and moisture protection printed circuit boards and medical devices these are typically coated 6 to 25 µm depending on the specific purpose required.

Does CW dimer for Parylene coatings differ from other dimer available on the market?

Yes. CW dimer differs in purity. Our proprietary dimers are over 99.7% pure. Industry standard dimers are in the 93% range. The higher purity ensures a higher yielding dimer and a Parylene coating that is clearer and more consistent in conformance to the substrate.

Are there different types of Parylene?

While there have been many types of Parylene researched and developed over the past 40 plus years, Parylene N and C have the widest commercial use. Each has its own unique electrical and physical properties.

CW Parylene N

Type N or Natural, has the highest dielectric strength of these two commercial versions, and a dielectric constant value independent of frequency. It is able to penetrate crevices more effectively than type C because of the higher level of molecular activity that occurs during deposition. Parylene N is commonly used where lubricity is most needed and for high frequency electrical applications because of its low dissipation and dielectric constant values.

N image

CW Parylene C

Parylene C differs chemically from N, having a chlorine atom on the benzene ring that results in a useful combination of electrical and physical properties including particularly low moisture and gas permeability. Parylene C deposits on substrates at a faster rate than Parylene N, and has a lower throw capability and an associated reduction in crevice penetration activity. Parylene C is commonly used for environmental protection.

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Other types of Parylene Coatings

For applications operating continuously in air temperatures greater than 125°C other variants are available. However, the deposition rates for these higher temperature capability variants are significantly slower than those for Parylene N or C and the cost of application will increase proportionally. For the majority of commercial applications, Parylene N or C will be the logical choice. However, in some cases an alternative variant may be more appropriate. We can advise on the best route on specific projects once the end use requirements are assessed.