Specific Process Knowledge/Polymer Processing/Polymer Processing/Coating/Parylene Coater

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Parylene is the common name for a family of poly(p-xylylene) polymers deposited as thin, conformal films by chemical vapour deposition (CVD). Unlike liquid coatings (spray, dip, spin), parylene is deposited from the vapour phase with no solvent, catalyst, or curing step. This gives pinhole-free, uniform-thickness films on virtually any geometry, including sharp edges, crevices, and fine features that liquid coatings cannot reach evenly.

A parylene coater is the integrated CVD system — vaporiser, pyrolysis furnace, deposition chamber, cold trap, and vacuum system — used to run this process.

Working Principle

The Parylene deposition process consists of four main stages:

1. Sublimation: Solid Parylene dimer is heated (approximately 120–180°C) under vacuum to produce a vapour.
2. Pyrolysis: The vapour passes through a high-temperature furnace (650–750°C), where the dimer molecules split into reactive monomers.
3. Deposition and Polymerisation: The monomer enters a slightly heated vacuum chamber containing the substrate. The monomer condenses and polymerises directly on all exposed surfaces, forming a thin, conformal polymer coating.
4. Cold Trap: Residual monomer and by-products are captured in a cryo-cooled cold trap before reaching the vacuum pump.