Spectroscopy Techniques for Parylene Coating Applications
Poly (para-xylylene), more commonly known as parylene, is a highly versatile family of polymers used in many conformal coating applications. At present, there are a wide range of parylene
variants available on the market – types N, C, D, F(VT-4), and F(AF-4) – each with their own unique thermal, dielectric, and mechanical properties. Despite all these variations, parylene is
an extremely simple polymer. Parylene N is the natural (or neutral) form of poly (para-xylylene) is comprised of alternating aromatic rings and methylene groups forming a highly stable polymeric
The other parylene variants can be broadly grouped into two main categories – chlorinated or fluorinated. For the chlorinated variants, one (type C) or two (type D) of the hydrogen atoms around the aromatic ring are replaced by chlorine, increasing the maximum operating temperature but decreasing the dielectric strength. Fluorinated parylene, on the other hand, requires the
substitution of four hydrogen atoms with fluorine. The two fluorinated variants are differentiated by whether the aromatic rings, F(VT-4), or the methylene groups, F(AF-4), have been fluorinated. It is important to note that Parylene F(AF-4) is often referred to as parylene HT due to its extremely high operating temperature (~350oC) and is the most used fluorinated variant.