Plant for parylene coating

Coatings with parylene

Document protection with parylene.
Document protection with parylene.
Document protection with parylene.
Document protection with parylene.
Document protection with parylene.
Document protection with parylene: The parylene coating hardly changes the appearance of a document (here an approx. 100-year-old newspaper), but protects it against, for example, spilled coffee.

Poly(para-xylylene), or parylene for short, is produced by a CVD process*. Layers of some 100 nm to some 10 µm can be produced. They are characterized by a combination of positive application properties.

The layers:

  • have good mechanical properties
  • very good dielectric properties
  • a gliding surface
  • are FDA certified and biocompatible**
  • transparent (depending on the layer thickness)
  • temperature stable
  • chemically inert and solvent resistant
  • offer excellent corrosion protection
  • represent an excellent permeation barrier

The Parylene*** coating is generally free of tiny holes (pinholes), even in very thin layers. The coating conforms to the surface to a high degree, as the process is characterized by an excellent splitting action, i.e. even places that are difficult to access (e.g. inner surfaces of tubes) can be coated. Porous substrates such as paper and membranes can also be coated.

A wide variety of substrate materials can be coated with parylene: from metals, plastics and elastomers to objects such as plants, insects or archaeological artifacts.

The coating process takes place in a vacuum. In contrast to many other coating processes, the substrate surface is not exposed to elevated temperatures, radiation or solvents. Therefore, even quite sensitive substrates can be coated.

Of particular interest are chemically functionalized parylenes. Currently, amino-functionalized parylenes are available. The amino groups can then be converted in a wet-chemical process, e.g. by bioactive substances. In this way, e.g. implantable stents have been modified for better biocompatibility.

*CVD: Chemical Vapor Deposition

**Classification as "class VI polymer" by USP (United States Pharmacopeia): among other things also implantation test passed

***The spelling "Parylene" (sing.) is also common in the German language

Typical fields of application of parylene coatings

  • Medicine and biology
  • Electronic devices, especially printed circuit boards
  • Automotive industry, aerospace
  • Corrosion protection (e.g. coating of magnets)
  • Document protection

Our services include

Process development on behalf of customers.

We have extensive experience in the field of surface modification and are well equipped with analytical instruments. Therefore we can offer our customers the following:

  • Developments to improve the adhesive strength of parylene coatings
  • Development of multilayer and functionalized systems including (plasma) chemical surface technologies and PVD metallization
  • Development of complex applications in the biomedical field (together with other IGB departments, e.g. Tissue Engineering)
  • Application coatings (test equipment)

Coating plant

Coating plant.
Coating plant.

The LABCOTER® system from SCS Cookson Electronics is designed for coating small batches, especially for use in laboratories. It has a coating chamber with internal dimensions of approx. ø 30x30 cm

Physical-chemical processes in parylene coating

Physical-chemical processes in parylene coating.
Physical-chemical processes in parylene coating.
Physical-chemical processes in parylene coating.
Physical-chemical processes in parylene coating.
Physical-chemical processes in parylene coating.
Physical-chemical processes in parylene coating.

The starting substance is a chemically largely stable dimer molecule (di-para-xylylene, figure above). It is also frequently used with halogen substituents. These substances can be vaporized (sublimated) in a vacuum without chemical changes.

If the vapor is passed through a high-temperature zone, a chemically highly reactive monomer is formed from the dimer (middle figure). On a cold surface, the substance (figure below) polymerizes immediately to form a closed polymer coating.

Of the numerous possible dimers, the following are the most commonly used:

  • Parylene N® (top figure)
  • Parylene C® (each monomer unit monosubstituted with Cl)
  • Parylene D® (each monomer unit disubstituted with Cl)

whose polymers differ in their property profile.

We can also deposit fluorinated parylenes, e.g. for high-temperature applications, and amino-functionalized parylenes.