Operationally, a tube is a hollow cylinder composed of glass, metal, plastic or a similar substance, designed to contain or transport something, typically liquids or gases.  When many people think of tubing, they envision its use in construction or mechanics.  Tubing of this nature is defined not only by its purpose and the stuff its made of, but also by two dimensions -- outside diameter (OD) and wall thickness (WT). 

Although parylene (XY) is a well-recognized and often used conformal coating, misconceptions about what it is and can do are common.  These mistaken beliefs interfere with true understanding of parylene’s uses.  Five of the most consistent misconceptions – and appropriate corrective information – should clear things up.

Permeation barriers for electronic devices are essential to assure their ongoing performance through a wide range of operational environments.  Polymer flexible conformal coatings provide good barrier protection, protecting device substrates from unwanted incursion by solid contaminants, chemicals, gaseous permeation and liquid water or vaporous forms of moisture.  Permeability reduction improves with enhanced coating adhesion, minimizing the surface’s  

          Parylene (XY) conformal coatings are known and recommended because of their many beneficial performance characteristics.  They provide uniform, pinhole-free protective films with excellent barrier/dielectric/insulative properties, able to conform to virtually any substrate configuration.  One property in particular – micron-thin coating layers – distinguishes XY from liquid coating materials such as acrylic (AR), epoxy (ER), silicone (SR) and urethane (UR), which need to be applied at least twice as thick in most cases and frequently more, limiting their range of uses.  Parylene typically is applied at 0.1 to 50 microns (0.004 -2 mils), while the thicknesses of liquid coatings generally range from 25 to 250 microns (1-10 mils).  Compared to liquid processes, gravity and surface tension generate negligible impact with parylene, eliminating film bridging, pinholes, puddling, run-off, sagging or thin-out during application.  XY’s coefficient of friction coefficient can be as low as 0.25 to 0.30.

          Of the five most commonly used conformal coatings, four – acrylic (AR), epoxy (ER), silicone (SR) and urethane (UR) – are classified as wet materials, meaning they are applied to substrates by three basic types of liquid-based technology:

Generally applied at micron-thin coating layers, parylene (XY) offers numerous barrier, dielectric, insulative and similar protective benefits to printed circuit boards (PCBs) and related electronic assemblies.  One property of parylene applied in its normal range of 0.013 – 0.051 mm. (0.0005 to 0.002 in.) is exceptional optical clarity, which makes it suitable for coating lenses and other devices requiring visual transparency, like photosensitive components. 

          Each conformal coating material exhibits a range of unique performance properties that determine its product uses.  Relevant factors include the required coating-thickness necessary to assure reliable performance.  Like other coating types, parylene (XY) layer thickness is largely a function of several factors:  (1) substrate material, (2) the kind of assembly being covered, and (3) its operational purpose.  Chemically inert parylene is effective at far-thinner application thickness than liquid-applied materials for coating printed circuit boards (PCBs) and related electro assemblies: 

After pertinent research you’ve determined parylene (XY) is the best conformal film for your coating assignment.  Especially relevant were XY’s uniform protective and insulative properties, which are useful for numerous applications, ranging from printed-circuit boards (PCBs) to medical implants to military-grade purposes.  Among parylene’s other advantages are: 

Liquid conformal polymers – resins of acrylic (AR), epoxy (ER), silicone (SR) and urethane (UR) – use wet application processes to attach to substrates.  Most prominent of these are brushing the wet coating onto an assembly, dipping (immersing) the assembly in a bath of liquid coating, or spraying the conformal film onto the designated surface.  The coating materials are wet when they are applied.  If

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.