Parylene Disadvantages

Parylene stands out as the ultimate shield against solvents among conformal coatings. It boasts exceptional defense against moisture and gases, incredibly high dielectric strength and biocompatibility. Despite these advantages, Parylene does come with certain drawbacks compared to other coating options.

One of these disadvantages is cost. The cost for Parylene is typically higher than other conformal coatings. This is because of many factors, such as the process itself, the raw materials involved and the labor required to properly prepare a device for coating. Although not always true, the pricing for Parylene tends to be higher than liquid coatings.

The Parylene is coated in a batch process. This means that there is only a finite amount of space available in the chamber for every coating machine run. The goal is to maximize the amount of items to be coated in the chamber. If there is a suboptimal amount of items to be coated available, the difference in price per piece could escalate drastically.

The raw material, Parylene dimer, is rather expensive ranging from a few hundred to several thousand dollars per pound. Due to the vapor deposition process used for applying Parylene, every surface, even those unnecessary to coat like the inner chamber diameter, ends up being coated. This inherent inefficiency of Parylene results in wastage of materials, ultimately leading to increased costs for the customer.

Masking and prepping an article for Parylene coating can be labor intensive. Because Parylene is applied as a vapor, it literally gets everywhere that air can. Coating operators and quality inspectors must consider this before applying the coating to guarantee that all requested coating-free areas are precisely as desired by the customer.

One major issue that often comes up for high-volume manufacturers is the limited throughput of Parylene. Runs of the Parylene machine can take anywhere from eight to over twenty-four hours. As a result of the limited chamber space, there is a fixed amount of product that can be processed during one coating cycle.

One final disadvantage of Parylene to consider is the poor adhesion to many metals. Parylene has always had poor adhesion to gold, silver, stainless steel and other metals. Many printed circuit board manufacturers use gold in their products because of its conductivity. While there are some adhesion promotion methods that will greatly improve adhesion to these metals, they are either material or labor heavy and can increase costs significantly.

While Parylene offers exceptional defense against solvents, moisture and gases, its disadvantages such as high cost, limited chamber space, material wastage, labor-intensive preparation and poor adhesion to certain metals need to be carefully weighed by customers considering this coating option.