Does Parylene Prevent Abrasion Damage?

Unlike liquid coatings – acrylic, epoxy, silicone and urethane – Parylene does not use wet method application. It can neither be brushed or sprayed onto substrate surfaces, nor will immersion – soaking the substrate in a bath of coating material – work.

Parylene relies on a unique chemical vapor deposition (CVD) method of coating application. Depositing a film via CVD results in superior conformity compared with other deposition techniques, primarily because of the distinctive chemical interactions between the surface and the reactive compounds. Vaporized, the gaseous dimer is introduced into a vacuum chamber containing the assemblies to be coated. These may be printed circuit boards (PCBs), implantable medical equipment, backplanes, MEMS/nano devices, motor components, sensors or optical lenses, among a wide and proliferating range of products.

Liquid coatings are pre-synthesized before application, whereas XY synthesizes during CVD, attaching onto and within substrate surfaces. During CVD, the polymer is vaporized into small segments, then pyrolized into a monomer as it enters a vacuum chamber containing the assemblies designated for coating. Parylene monomers connect into chains creating polymers both on the surface of the substrate material and within as well. Thus, rather than simply offering surface conformal protection, Parylene penetrates the substrate surface, generating additional security. Room temperature formation means the process and coatings are effectively stress-free. Parylene’s excellent mechanical properties and ability to withstand abrasion, begin with CVD.

The result is perhaps the strongest, most resilient of all commonly used conformal coatings. However, once applied, XY is not essentially indestructible, but Parylene resists most normal types of abrasion. Chemically inert, and with a broad temperature range, it is unlikely to corrode, despite micro-thin film coverings for many uses; protected above and below a substrate’s surface, XY coatings withstand persistent marring, scuffing, scratching or other instances of rubbing away/wearing down, generally for the life of the assembly.

Once deposited, Parylene impact resistance is high. Compared to other coatings, Parylene conformal films are generally less than 1 mil (0.001 inches or 25.4 microns) in thickness, averaging between 1 – 25 microns in many cases. Parylene types vary somewhat in chemical structure and functional properties, but all possess very high dielectric strength (5500-7000 volts/mil), withstanding the effect of solvents while resisting abrasion, enhancing the film’s performance. In addition, Parylene may be annealed to increase cut-through endurance, coating hardness and overall abrasion resistance, which is the result of polymer density and an increase in crystallinity.

Measured against liquid coatings, Parylene conformal films offer high tensile and yield strength. This includes a physical hardness greater than epoxy or urethane, adding rigidity to a fragile component, while reducing the impact of operational vibration. Despite Parylene’s wear resistance, persistent, prolonged use in applications characterized by repeated abrasion with harder materials is not recommended.