What is the Uniformity of Parylene Conformal Coating?

Parylene is often applied to substrates or materials where there is no room for any voids in the protective coating. The applications are subjected to harmful chemicals, moisture packed environments or even the human body. These are often mission-critical devices which cannot allow any environmental factors to alter their performance. Whenever these devices need this stringent level of protection from the elements, Parylene is the only logical choice. 

Parylene coatings are completely conformal, provide uniform thickness and are pinhole free. This is achieved by a unique vapor deposition polymerization process in which the coating is formed from a gaseous monomer without an intermediate liquid stage. As a result, component configurations with sharp edges, points, flat surfaces, crevices or exposed internal surfaces are coated uniformly without voids.

In image A, the orange layer is Parylene, displaying completely uniform coverage of the green substrate, gray leads, and black component. This all-encompassing coverage is one of Parylene’s greatest competitive advantages against other liquid conformal coatings.

Image B is an example of the coverage that liquid coating provides. On the sharp edges of the gray leads and black component, the orange layer of coating is substantially thinner than at other areas. There is also pooling on the sides where the leads meet the connector. Factors like this are inherent with liquid coatings, simply because they are a liquid.