Implications of Parylene Coating Thickness:

Parylene is a transparent polymer offering uniform and pinhole-free conformal coatings. Different varieties of parylene (Parylene N, C, D, AF4, and F) formed by a modification in their molecular structure. Each modification results in a set of material properties that are applicable in different service conditions. The basic type of parylene derivatives is the Parylene N (poly-para-xylylene) monomer.

A natural process, corrosion enacts chemical/electrochemical reactions that degrade and gradually destroy materials or components within a functional environment.  The outcome can be dangerous and costly to repair.  

Parylene (XY) polymers provide robust, dielectric, micron-thin conformal coatings for a considerable range of electronic devices, most prominently printed circuit boards (PCBs).  XY’s unique chemical vapor deposition (CVD) application method synthesizes in-process, depositing gaseous parylene deep into a substrate’s surface.  CVD occurs on a molecule-by-molecule basis, conforming to all underlying contours, regardless of shape or position, to the nanometer, if necessary.  Pre-synthesized liquid coatings lack many of parylene’s performance properties, having far less ability to successfully and conformally penetrate crevices in the substrate

 Used as moisture and dielectric barriers, polymer parylene (p-xylylene/XY) coatings are conformal and pinhole free.  Applied by a unique chemical vapor deposition (CVD) method, parylene penetrates beneath substrate facades, simultaneously attaching above surfaces at the molecular level.  CVD generated films cover crevices, exposed internal regions, points and sharp edges uniformly, without gaps or breaches.  Compared to liquid coating materials – acrylic, epoxy, silicone and urethane -- XY film layers are micron-thin, enhancing their utility for microelectricalmechanical systems (MEMS) and nano technology (NT). 

For conformal coatings, elongation is a measure of material ductility -- a specific coating's ability to undergo significant plastic deformation before rupture.  A coating’s yield elongation is the maximum stress the material will sustain before fracture.  Thus, computed parylene (XY) elongation measurements represent the total quantity of strain the conformal film can withstand before failure.  While elongation is equal to a material’s operating failure strain, it has no exclusive units of measurements.  Typically,

Parylene (XY) conformal coatings are applied to substrate materials through a specialized chemical vapor deposition (CVD) process that completely eliminates the liquid phase of wet coatings.  No initiators or catalysts are involved in CVD polymerization, which synthesizes truly conformal protective film in-process.  This is in stark contrast to wet coating materials such as acrylic, epoxy, silicone and urethane, which are synthesized prior to application via, brush, dip or spray methods.  Wet during application, liquid-coated substrates requiring further drying and curing.

Parylene:  Properties and Processes

Parylene conformal coating (XY) provides insulative protection for complex electronic circuit assemblies expected to function through rigorous operating conditions -- potential chemical, electrical, moisture and vapor incursion during performance.   Applied through chemical vapor deposition (CVD), parylene penetrates deep within substrate surfaces, generating a level of assembly security surpassing that offered by liquid coatings such as acrylic, epoxy, silicone and urethane.  Yet, although XY is applied in a vacuum, it’s capacity to provide these extraordinary qualities does not exist in one.  Parylene’s durable protective value depends on film adhesion, a quality subject to persistent, thorough inspection throughout the production process.

Parylene Chemistry and Production Requirements