5 Common Misconceptions of Parylene

There are often many questions about Parylene, its properties and its ability to protect various components across industries. There are also many Parylene misconceptions. Below is a look at the five leading misconceptions.

1. Parylene does not stick to metal.

This misconception is based in truth. One drawback of this coating is that its chemical structure doesn’t always adhere as well to metal as it does to other materials. However, there are two ways to rectify the challenge. Metal surfaces that aren’t perfectly smooth will provide enough surface area for Parylene to adhere to the substrate. If a product has smooth surfaces, Parylene adhesion can be improved by using a surface modification method such as silane. Surface modification which adheres to both the coating and the metal, providing the needed protection.

2. Once applied, it is essentially indestructible.

In the world of conformal coatings, Parylene is one of the toughest. It has a broad temperature range, can withstand most normal types of abrasion and is chemically inert, making it unlikely to corrode away. It can be removed, though. Extreme heat will eventually melt it, although it carries the risk of damaging the components underneath. Instead, the most effective removal methods usually require a mechanical approach, with the use of tools providing micro abrasion typically providing the best results.

3. Every type is the same.

Parylene dimer comes in two primary types: C and N formulations. The most popular type, Parylene C, offers better performance across most metrics. Parylene N has three key advantages. It has a higher melting point, it is a more effective dielectric and because of its more active molecular structure, it is better able to permeate very small cracks and crevices, making it a better compound for coating extremely complex surfaces. Other types of the dimer are also available, although Parylene C and N variants are, by far, the most commonly used.

4. Parylene is always the best choice.

For many applications, Parylene is the best choice. It offers a package of attributes that make it generally more attractive than other coatings. However, it might not be the best coating for an application’s exact needs. For example, epoxy is harder, providing even better protection against damage or having a product reverse-engineered. Acrylic is easier to remove. Silicone can be applied in a layer so that it serves as a shock absorber as well as a coating. Finally, most coatings are also usually less expensive and are usually easier to apply quickly to large quantities of product.

5. Parylene is too expensive for my application.

Parylene conformal coatings are usually an expensive choice due to both the high cost of the underlying chemical and the unique demands of their vapor deposition process. However, costs can be managed to make them more affordable than the material cost on its own might indicate. First, typically less dimer is needed to coat an item than anticipated. This is because it is effective at thickness levels measured in microns instead of mils. Using less means materials can be stretched further.

Second, the unique way that the coating gets applied both creates opportunities for waste and for minimizing that waste. Vapor deposition means the entire coating machine needs filled with the material and that the material will coat the chamber as well as the products. In a relatively empty chamber, the waste rate will be high. However, if a run includes enough product to fill the coating chamber, this will reduce the waste per unit, lowering cost.

Lastly, the cost benefits of failure must be weighed against the cost of coating. Often times, on critical devices, the higher price is worth the potentially life savings benefits that Parylene offers.

If you have additional questions about Parylene or other conformal coatings, contact SCS. Our expert staff can answer your questions, clear up your misconceptions and help you find the right coating for your next project.