Conformal Coating Comparison: Parylene N vs. Parylene C— 16 / 01 / 2017
Posted by Scott Curtis on Monday, January 16, 2017
In 1986, a Converse shoe commercial pitted two premiere NBA superstars one on one; Larry Bird vs. Magic Johnson. Long before this TV spot aired, interesting back-and-forth debates occurred over who was the more dominant player. I idolized Bird at the forward position for his hard-nosed style, blue-collar work ethic, fierce determination, and deadly accurate jump shooting. I admired Magic at the point guard position for his flashy style, intense desire, magnetic personality, and incredible passing skills. If you liked high-scoring and clutch-shooting you probably favored Bird. If you enjoyed fast breaking and dazzlingly no-look passes you most likely preferred Magic. Each had an incredible impact on their respective teams and I appreciated them both for their greatness.
It’s difficult to imagine the “Showtime” Lakers running the floor with the introverted, Larry Bird. Visualizing the glamour of Magic Johnson in Celtics green is equally as bizarre. Playing at different positions, it’s apparent that each greatly benefited the team for which they represented. The head-to-head likenesses of these two legendary athletes leads me into the comparisons of the two most common types of Parylene; Parylene N and Parylene C.
What is Parylene? Parylene is a vapor-deposited conformal coating, so it surrounds the target and perfectly follows its contours, achieving total encapsulation. Parylene films are commonly used as transparent, flexible coatings in electronic devices and biomedical applications, exhibiting barrier properties against corrosion, low dielectric constant, and moisture resistance.
Which Parylene should I use for my job? Learning the differences between Parylene N and Parylene C coating types will help you better understand which is best for your application.
Parylene N is typically used to coat areas that C cannot. That favors its use in several applications, particularly as a coating for select medical products and elastomers. It is able to penetrate crevices more effectively than the Parylene C because of the higher level of molecular activity that occurs during deposition. In addition, Parylene N provides a higher dielectric strength of the two versions and a dielectric constant value independent of frequency. Parylene N is commonly used in high frequency applications because of its low dissipation. Parylene has a coefficient of friction similar to PTFE (Teflon) making it ideal for coating forming mandrels. However, because the molecule in N is more active than the C molecule it takes twice as long to do runs of Parylene N. The longer deposition time for Parylene N will result in more chamber time and a higher coating cost for an equivalent thickness of Parylene C.
The benefits of Parylene N combine supreme levels of conformation and functionality at higher temperatures of up to 220° C (without oxygen), making this type of coating especially valuable.
Parylene C is produced from the same raw material (dimer) used to make Parylene N, modified by a chlorine atom for one of the aromatic hydrogens. It has a useful combination of electrical and physical properties, plus a low permeability to moisture, fluids, and corrosive gases. Its ability to provide pinhole-free conformal barriers makes it the coating of choice for many critical medical electronic assemblies. Parylene C has proven to be suitable to protect devices from the body and the body from the device. Additionally, Parylene C performs in air without significant loss of physical properties for 10 years at 80°C and in the absence of oxygen to temperatures in excess of 200°C.
The benefits of Parylene C combines depositing on substrates at a faster rate than Parylene N, and has a low throw capability and an associated reduction in crevice penetration activity. This is a driving factor in Parylene C being the Parylene of choice for most dielectric and barrier coating applications.
Technical Data Sheet obtained following appropriated ASTM methods: Properties of Parylene
The debate over who was more superior; Larry Bird or Magic Johnson will never really have a clear answer. Even though their personalities were very different, the similarities in their games was striking. Both exhibited a rare ability to make everyone else around them better. Conversely, there are many differences between Parylene N and Parylene C, but it’s important to remember that both types offer the same basic benefits, including thermal stability, electrical insulation, reliability and longevity. Depending on the properties required, it can sometimes be difficult to determine whether to use Parylene N or Parylene C. Deciding which type of Parylene is right for your job comes down to the specifics; consider your needs, then consider the strengths and weaknesses of each type.
For more info on Parylene N and C, Contact PCT today!
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