Preventing Parylene Delamination
Parylene conformal coatings are chemically inert, ultra-thin, lightweight, and due to the chemical vapor deposition (CVD) application process, the coatings are highly conformal, wrapping around every edge available. Parylene films deeply penetrate component surfaces, an ideal solution for complex component configurations such as angular surfaces. All surfaces are coated evenly regardless of the CVD chamber position, and the coating deposits the same thickness all around the objects being coated. This vapor phase coating process also leads to pinhole-free coatings free from defects.
Delamination describes instances in which the conformal coating separates from the coated surface, which can result in an unattached, torn, non-conformal coating and an unacceptable finish.
However, some of Parylene’s desirable properties and its superior application method can also raise challenges. Although Parylene’s chemical inertness is a benefit because it doesn’t react to many chemicals, this means it also may not adhere enough to the substrates it is applied to. To remedy this, application surfaces should be stringently cleaned of fluxes and solvents before coating. And although the CVD coating application process allows Parylene to flow into crevices and be apply on hard-to-reach substrates, it is a mechanical adhesion method. These issues, if not adequately addressed, can lead to Parylene delamination.
Delamination describes instances in which the conformal coating separates from the coated surface, which can result in an unattached, torn, non-conformal coating and an unacceptable finish. Delamination defeats the purpose of Parylene conformal coatings and should be avoided at all costs. Even partial lifting can render the protective coating useless.
Causes of Parylene Delamination
There are many sources of Parylene delamination, including standard processes such as demasking, which can create a need for exceptional quality control inspection procedures after production. Other causes include:
- Coating porosity: When a difference in vapor pressure occurs between the component surface and the Parylene coating, this creates vulnerability to moisture permeation and intrusion into the substrate. As fluctuations of pressure and temperature subsequently occur, osmotic pressures are generated, separating the coating from the component.
- Incompatible materials: For successful coverage, the component surface and the Parylene coating must bond together. When the Parylene and the surface are incompatible, incongruous surface energies are generated, causing minimal, if any, bonding.
- Contaminated surfaces: Improperly cleaned component surfaces do not support adhesion.
How to Prevent Parylene Delamination
Fortunately, defining the causes of Parylene delamination leads to appropriate solutions. To prevent Parylene delamination, use these techniques before, after, and during CVD processing:
- Select a Parylene type with suitable moisture impermeability while ensuring the material is compatible with the component or substrate.
- Coordinate component or substrate material with the proper grade of Parylene to generate reliable adhesion.
- Ensure that the surfaces being coated are free from contamination and adequately cleaned to enhance adhesion qualities.
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Parylene Services With HZO
Typically, reworking Parylene is challenging as it requires specialized training and technique. Therefore, the best approach to avoid Parylene delamination is to take the preventative measures discussed. Ensuring you have an excellent quality control team to detect any defects post-production is helpful as well. At HZO, we have rigorous quality assurance tests to ensure delamination will not be a problem. Since our inception, there has not been a single product failure due to coating issues. To learn more, contact us.
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