Circuit Boards
Parylene was developed over thirty years ago primarily to provide a conformal coating for printed circuit boards. It provided benefits which made parylene unique compared to other dip, spray or brushed liquid conventional conformal coatings.

Parylene is the commercial name of the ply-para-xylylene polymeric family. It is applied by vapor depositionunder a vacuum in a room temperature coating chamber. The coating process exposes objects to the gas-phase monomer (see process) at low pressure. Through vacuum deposition, parylene condenses and polymerizes on the object’s surface in a polycrystalline fashion, providing a coating that is truly conformal and pin-hole free. Compared to liquid processes, the effects of gravity and surface tension are negligible,so there is no bridging, thin-out, pinholes, puddling, run-off or sagging. And with the process taking place at room temperature, there’s no thermal or mechanical stress on the object.

Parylene films ranging from 0.25 to 1.5 mils in thickness provide a barrier which is equivalent or superior to 2 to 6 mils of other conventional coatings. Parylene does not pull away from edges or exhibit meniscus forces as do conventional liquid coatings applied by spraying, dipping or brushing. Because parylene is in a molecular state and builds from the surface up, board components are coated evenly and consistently, thus electrical protection can be achieved with a thinner layer than that of the conventional coatings. The dielectric constant and dissipation factor are practically insensitive to changes in frequency.

Given its resistance to humidity, barrier properties, physical and thermal properties and its unique molecular structure, parylene is practically insoluble in all known organic and inorganic solvents including strong acids and alkali. Parylene proves to be an effective barrier to corrosive agents and does not out-gas. With parylene meeting mil spec 46058C criteria, it is an excellent choice when it comes to conformally coating printed circuit boards for military and aerospace applications.

When looking at the total cost of protecting your parts in a hazardous or contaminated environment, parylene is typically the least expensive option for coating electronics.

See Technical Information for details.

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