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Parylene Masking

Have you ever heard of too much of a good thing? Parylene Conformal Coating is an extremely protective coating that encapsulates the entire PCB, LED, or medical device to ensure your electronics remain resilient throughout exposure to harsh environments. But what happens when certain components are covered with our polymeric film? Well, it can inhibit some of the critical functions of those key components. Thankfully, we have masking processes that resolves this issue so devices can still benefit from the Parylene coating without losing their functionality.

What is Masking and why is it important?

Masking is the process of applying a temporary film, boot, tape or plug to a designated assembly, assuring that selected components are not covered by our Parylene film.

The purpose of Parylene is to provide environmental and mechanical protection to extend product life, prevent costly repairs, and reduce risks of failure. However, if Parylene coating gets in the wrong component it can interfere with the stability and performance of the product causing a failure. Therefore, one of the most critical stages in the Parylene coating process is to properly mask the product.

Masking Materials

When masking, different components require different materials, such as: peel-able tape dots, tapes/contact pads, boots and either non-ammoniated or water-soluble liquid latex. It is always important to identify certain factors when deciding what masking materials to use for each project. Factors include, but not limited to, the quality of each material to ensure masking failures do not occur and how each masking material is used within the parylene process either by itself or in a combination with other materials.

Parylene masking dots and tape generally use a polyester or polyimide backing. In most cases properties such as conformability is just as necessary to the masking process as strength, stability, and overall quality.

For masking tapes and contact pads, there are two widely used solutions. Polyester or kapton tape and liquid peel-able latex. These masking materials effectively prevent coating seepage into the component; they then easily peel from contacts after coating is applied.

Masking caps, also called boots, are designed to be a perfect fit on components. They shield a component during spray or dipping coating processes. Our boots use the standard, anti-static materials.

The Parylene Masking Process

Here at Para-Coat Technologies, our highly trained staff understands the importance of conformal coating masking materials and the effective process in protecting components from ingress of Parylene coating. Improper or poor Parylene masking can compromise the coating or possibly cause failure of the finished product. Therefore, proper masking for Parylene coating is one of the most important phases. Masking is done in accordance with the customer’s drawings and requests for coating keep-out areas. Although the masking process can be labor-intensive and time-consuming, it is important to clearly identify the customer’s keep-out areas that are not to be coated during the vapor deposition of Parylene.

Post Masking

After the masking phase, the product is thoroughly inspected to ensure that all areas have been properly masked and then it is placed into the vacuum chamber for Parylene deposition. Parylene is vapor-deposited and uniformly coats all surfaces of the substrate.

However, on the areas that are masked, the Parylene is deposited on the masking materials instead of on the actual substrate. Stopping any unwanted Parylene from entering certain areas.

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