Why Use Parylene?
Parylene is considered by many to be the ultimate conformal coating for the protection of devices,components and surfaces in the electronics, instrumentation, aerospace, medical and engineering industries.
Parylene is unique in being created directly on the surface at room temperature.
There is no liquid phase involved. Coatings are truly conformal, of uniform controllable thickness, and are completely pinhole-free at thicknesses greater than 0.5μ.
The coating completely penetrates spaces as narrow 0.01mm.
No initiators or catalysts are involved in the polymerisation so the coating is very pure and free from trace ionic impurities.
Room temperature formation means the coatings are effectively stress-free.
Any substrate that is vacuum-stable can be coated and the coating adheres strongly to all materials,even stainless steel, provided the appropriate adhesion-promotion techniques are used.
Parylene is chemically and biologically inert and stable and make excellent barrier materials.
Parylene is almost completely unaffected by solvents, have low bulk permeability and are hydrophobic.
Coatings easily pass a 100hr salt-spray test.
Parylene has excellent electrical properties: low dielectric constant and loss with good high-frequency properties; good dielectric strength; and high bulk and surface resistivities.
Parylene has good thermal endurance: Parylene C performs in air without significant loss of physical properties for 10 years at 80°C and in the absence of oxygen to temperatures in excess of 200°C.
Parylene is transparent and can be used to coat optical elements.
Coatings perform well as dry lubricants: static and dynamic friction coefficients are equal and comparable to fluoropolymers with the advantage that they also have good wear and abrasion resistance.
1. A Poly-para-Xylylene coating film formed by the chemical vapor deposition (CVD) process.
The coating film is completely pinhole free and the film thickness can be uniformly controlled in the micron range to conform to any irregular shape, whether it has a sharp edge or a complicated internal surface without any thermal stress.
2. Parylene is a conformal protective polymer coating material utilized to uniformly protect any component configuration on such diverse substrates as metal, glass, paper, resin, plastic, ceramic, ferrite and silicon. Because of its unique properties, Parylene conforms to virtually any shape, including sharp edges, crevices, points; or flat and exposed internal surfaces.
3. Parylene provides exceptional protection for the most extreme environmental conditions. This polymer is called out as "Type XY" coating in the MIL specs such as MIL-I-46058C, and IPC-CC-830.Parylene is unique as it is deposited through a vacuum deposition system, as gaseous molecules capable of providing a pin-hole free film at 3 microns thickness. This method of application yields a true conformal film complexion that contours all surfaces, exposed or hidden. Further, the thickness of the Parylene film could be very tightly controlled due to this unique method of deposition.
4. The Parylene film is chemically inert, no acid or alkaline material will attack it in any significant manner. The FDA has approved the Parylene film for human implantable devices. The Parylene film possesses superior dielectric properties, approaching 8000 volts for 1 mil thickness.
5. Usages for the Parylene coating includes, implantable devices, fish tags, circuit boards (SMT, Thruhole, or mixed technology) sonar applications, ultrasonic applications, surgical devices, and elastomers.The Parylene coating process involves changing the molecular structure of the Parylene dimer into a monomer, then depositing monomers at room temperature onto the substrate to form the polymeric chain of the Parylene film.
6. Parylene coatings are completely conformal, of uniform thickness and pinhole free. This is achieved by a unique vapor deposition polymerization process. The advantage of this process is that the coating forms from a gaseous monomer without an intermediate liquid stage. As a result, component configurations with sharp edges, points, flat surfaces, crevices or exposed internal surfaces are coated uniformly without voids.
7. Parylene has no curing cycle, unlike other conformal coating materials. Once deposited, it is ready to go to work.
8. Parylene has chemical resistance similar to Teflon. It resists attack and is insoluble in all organic solvents up to iS00C and is resistant to permeation by most solvents with the exception of aromatic hydrocarbons. Since Parylene coating is a high molecular weight, linear, crystalline polymer having an all carbon backbone without any oxygen, nitrogen, or sulfur atom links in the backbone it is hydrophobic. This carbon backbone, coupled with its substantial crystallinity, makes Parylene quite stable and highly resistant to chemical attack.
There are three common forms of the Parylene polymer:Parylene C, Parylene N, Parylene D and Parylene F, each with unique properties that suit it to particular insulation applications.
For example, Parylene N provides particularly high dielectric strength and a dielectric constant that is independent of frequency.Because of its high molecular activity in the monomer state, Parylene N has the highest penetrating power of the Parylenes, with the ability to coat deep recesses and blind holes.
Parylene N has a very low dissipation factor, a low dielectric constant, and is ideal for high frequency applications where the coating is in the direct RF field.Unlike liquid coatings, the Parylene deposition process does not entrap air that can lead to high frequency corona problems.
Parylene C has a chlorine atom on the benzene ring, and this results in modified electrical and physical properties including very low permeability to moisture and corrosive gases.The Parylene C deposition rate is substantially faster than that of Parylene N, resulting in reduced crevice penetration ability.
Parylene D, with two chlorine atoms on the benzene ring, has the highest degree of thermal stability.