Thermomechanical Properties of Parylene X, A Room‐Temperature Chemical Vapor Depositable Crosslinkable Polymer

Poly( p ‐xylylene) has existed commercially for many years but has never gained widespread acceptance due to its poor thermal and optical properties. Parylene X, a new chemical vapor depositable polymer on the same process platform as poly( p ‐xylylene), is a copolymer of poly(ethynyl‐ p ‐xylylene) and poly( p ‐xylylene). It exhibits thermal stability to at least 420 °C, has a low coefficient of thermal expansion of 55 ppm after it is crosslinked, and exhibits low stress. It possesses a glass transition temperature of 73 °C and starts to crosslink at ∼160 °C with a peak isotherm at 250 °C. The ethynyl functional groups crosslink to form the very stable phenyl moiety.