Is Parylene a Nanocoating?

al films become less effective for coating them. Ongoing development of microelectricalmechanical systems (MEMS) and nanotechnology, has little room for the thicker conformal films provided by liquid materials, such as acrylic, epoxy, silicone and urethane. Nanocoatings are increasing in prominence, frequently surpassing micro-thin Parylene for many MEMS/nanotechnology purposes.

This is surprising, since Parylene’s micron-thin coating layers typically range between 0.1 to 50 microns (0.004 -2 mils) with film thicknesses controllable to less than a single micron (1 μm). Parylene’s capacity for providing effective, pinhole-free conformal protection with micro-level coating layers unavailable to liquid materials offer a significantly wider range of product/process applications in comparison to conventional liquid film materials.

Nanocoatings are another story.

Nanocoating Properties in Comparison to Other Conformal Films

Evolving nanotechnology deploys individual atoms as working units, engineering functional systems on a molecular scale. Incredibly minute, one nanometer equals one-billionth of a meter (10-9 m) so that one inch = 25,400,000 nm; more illustratively, a sheet of newspaper is 100,000 nm thick. In addition to being far smaller, nano devices offer additional advantages:

• Substantially lighter in weight
• Enhanced chemical reactivity/strength compared to larger-scale structures
• Better control of the light spectrum
• Some nanotechnolgoy devices possess the mechanical complexity of machines

Nanocoatings provide reliable conformal protection at far finer film layers than any liquid coatings or Parylene, often replacing Parylene for projects only it was suitable for, in the recent past. Nanocoatings’ prevention of corrosive substances access to electronic components aligns them with conventional conformal coatings but far more effectively at MEMS/nanotechnology levels. Nanocoating flexibility and nano thickness permits excellent, uniform coverage of complicated 3D structures, deposited essentially anywhere regardless of a component’s size, with minimal impact on performance. They provide uniform, pinhole-free protective films with excellent dielectric/insulative properties and are able to conform to virtually any substrate configuration. In addition, Nanocoatings are:

• Scratch-resistant, limiting surface chipping/scratching
• Ultra-hydrophobic, repelling water/moisture
• Barrier-resistant, protecting substrates from intrusive elements

Nanocoating Application: Similarities and Differences

Nanocoating applications can use liquid methods; both immersion (dip) and spray procedures are acceptable. Brush procedures are unsatisfactory for nanocoatings’ minute and comparatively delicate structures. The coatings are simply overwhelmed by brush procedures. With liquid processes, nano-particles suspended in solvent are applied to the PCB and allowed to either bake in an oven or air dry. In the first case, temperatures need to be precise because nano-particles can melt into a glassy substrate if the oven is too hot. Nanocoatings’ ultra-thin film consistency makes them susceptible to abrasion, although amenable to timely rework.

Nanocoatings somewhat resemble Parylene because they can also be deposited using non-curing, single-step plasma deposition techniques, similar to Parylene’s chemical vapor deposition (CVD) methodology. Nano-plasma technology transforms matter from solid to liquid to gas to plasma in a manner parallel to Parylene; with CVD, chemically inert, powdered-but-solid Parylene dimer is transformed into a vapor at the molecular level, in a vacuum and at ambient temperature. Like nanocoating, Parylene uniformly covers virtually any board topography.

Nano-plasma technology creates a stable plasma through electromagnetic discharge of gas at low pressure/temperature; molecules decompose into a mix composition of neutral and charged particles, which interact with exposed substrate surfaces. The result is coating through plasma particle-interaction with internal surfaces.

Parylene coatings are ultra-thin, measuring 0.1 torr (0.000133322 bar), and very useful for MEMS/nanotechnology applications. While these levels are far thinner than liquid coatings, they can only approximate those operational for nanocoatings. Assessing nanocoating thicknesses in relation to Parylene compares nanometers with centimeters; 1 cm = 10,000,000 nm. The 0.1 cm common to XY molecular path separation equals 1,000,000 nm. By any estimation, the difference is remarkable, especially in consideration of the fact that some nanocoatingss are effective at 1 nm.

Parylene can provide reliable conformal protection for many MEMS/nanotechnology applications and does share a similarity with some nanocoating application processes. It is not a nanocoating in the strictest sense, primarily due to nanocoatings exceptional film layer thinness compared to all other conformal materials. Parylene does come closest, and further technological development will improve its performance compared to nanocoatings. At this juncture is process evolution, XY does provide a generally stronger conformal film than nanocoatings for many MEMS/nanotechnology purposes.