by Alex Shepard
Conformal coatings are used to protect products from the elements. They got their start protecting printed circuit boards (PCBs), but now, conformal coatings are used in a wide variety of applications. Parylene and acrylic are two of the most popular types of conformal coating. Read on to find out about the key advantages of each.
Application Methods
Both parylene and acrylic coatings must be applied by a trained professional. Business owners can visit https://pctconformalcoating.com/ to learn about one company that can help or read on to find out what the application processes entail.
Parylene Application Process
Parylene coatings are applied onto substrates through vapor deposition. This application process can take anywhere from one hour to several days depending on the required coating depth. It involves placing a raw parylene product, typically Parylene C, N, D, or AF-4, into the loading boat in a solid-state and inserting it into the vaporizer.
The parylene is then heated to between 100 and 150 degrees Celcius, producing a vapor that splits the molecules into monomers. The monomer gas is drawn by vacuum onto the substrate then cooled to between -90 and -120 degrees Celcius in what is known as a cold trap. This removes residual materials.
Acrylic Application Process
Acrylic conformal coatings can be applied in four different ways. They can be sprayed on, brushed on, used to dip the products, or applied using robotics-assisted tech. What all these application methods have in common is that they should only be performed by a trained professional.
Coating Thickness
Acrylic coatings are typically thicker than parylene coatings. They range from between 0.002" and 0.005". Parylene films typically range from 0.0005" to 0.002" in thickness, but can be applied as thin as 0.0001", making them ideal for a wide variety of applications.
Common Uses
Acrylic coatings are typically used to provide moisture protection for PCBs. Parylene can be used for this purpose, as well, but it has a wider range of applications. It's now common to see parylene-coated medical products, including stents, catheters, and needles.
Unique Properties of Parylene
One of the most significant advantages of parylene is that it can be applied in very thin coats. It's also highly resistant to moisture, solvents, and temperature extremes and offers exceptional dielectric strength. It is very difficult to remove parylene coatings once they have been applied, though, and products can only be re-coated using the same vapor deposition process described above.
Unique Properties of Acrylic
Acrylic conformal coatings offer high dielectric strength, decent moisture resistance, and fair abrasion resistance. What really sets them apart is the ease of removal. While parylene must be removed using a specialized process, acrylic coatings can be removed by solvents. That also means they are unable to protect against solvents and solvent vapors, though.
The Bottom Line
Acrylic coatings are considered a good option for entry-level protection since they're cheap to apply and can protect against a lot of contaminants. Parylene coatings offer greater moisture and abrasion resistance and an equally high dielectric strength, but they require a more specialized application and removal process. The best way to figure out which of these coating options will be the best fit for a PCB or another product is to contact a company that specializes in applying conformal coatings. Since each has its own set of unique advantages, an expert can help business owners make an informed choice.
