Choosing Parylene Thickness

One common question from those who are new to conformal coating is how to choose the right Parylene thickness.

One factor to take into consideration when determining the right Parylene thickness is the amount of clearance needed. For example, if the printed circuit board that needs coated has an enclosure, there usually will not be too many clearance issues. However, in some cases, even an extra mil of coating can create a clearance issue that results in extra mechanical abrasion to the Parylene and potentially damages the coating.

Another determining factor is the dielectric strength required. For applications that require higher dielectric strength, a thicker coat of Parylene has higher dielectric properties than a thinner coat. Applying the coating thick enough to meet the dielectric strength requirements while also avoiding creating a clearance issue may be difficult. Testing different coating thicknesses may be required to adequately meet both of these needs.

In some cases, the coating thickness to be applied is specified on the drawing. To identify any potential issues with the specified Parylene thickness, the drawing needs reviewed and compared to the application to be coated.