Truly Conformal and Uniform Thickness
No Thermal Stress, No Cure Force
Chemically Pure and Homogeneous
Particle encapsulation and immobilization
Typical parylene coating thickness ranges from 0.5 microns to 50 microns. Thickness can be controlled in the micron range, regardless of geometry. This allows for high performance protection without taking up critical device space.
With thickness in the microns and density similar to air (~ 1.2 g/cm3), the additional weight added to your device is negligible
The molecular deposition process allows parylene to build up uniformly on all surfaces. It will evenly coat sharp edges, points, crevices, exposed internal surfaces and any complex shape. Because there is no liquid phase, there is no pooling or bridging between close features that is seen with liquid coatings.
Parylene is considered a green technology because there are no by-products or chemicals used that are harmful to our environment. The molecular deposition process doesn’t require any solvents for curing or any other harmful additives.
With liquid and spray coatings, small “pinholes” are created when microbubbles degas during drying. The pinholes create weak points that allow electrical current to leak and compromise the barrier layer.
The parylene deposition process ensures a complete pinhole-free coating because there are no microbubbles and no curing.
Tests have been performed to show completely pinhole-free coatings at thicknesses greater than 0.2μ.
This results in an extremely reliable coating, electrical insulator, cleaner electrical signals and a known barrier layer that will perform consistently over time.
Using spray and dip coatings on fragile devices typically introduces thermal stresses by heating up parts during coating and cooling them down during a cure phase. This temperature change can cause different materials to expand and contract at different rates. This causes cracks to form and bonding surfaces to come loose. In some cases, the coating process is leading to the failure of the device immediately or over time.
Parylene is deposited at room temperature so the coating is applied “stress-free”. Parts stay at room temperature throughout the entire process to help ensure the long term reliability of coated parts.
The room temperature, non-contact, deposition process enables parylene to add a layer of structure to fragile features. This can be the main use for the coating as a MEMS structural layer, or an added benefit when coating for other reasons.
The encapsulating support helps ruggedize devices to help them survive vibrations and other mechanical shocks. Parylene can strengthen delicate wire bonds by a factor of 10.
Parylene is ready for use immediately after it is deposited. There is no waiting. No cracking or settling during the cure process and no outgassing.
The parylene deposition process converts parylene from a pure dimer, to a gas, and finally to a solid.
Liquid-based coatings usually require reagents to promote the chemical reaction. However, after polymerization occurs, the catalysts need to be removed through a secondary process. It is common that some of the species remain behind. These residuals reduce the purity of the polymer film and can have effects on the coating properties.
Parylene is pure and does not require any reagents for a chemical reaction. The final product is a pure and homogeneous parylene film. There are no issues with leaching or outgassing. This results in a reliable coating that is free from any ionic contamination or possible leaching.
Fine particles of conductive dust can be hard to remove from parts because of their strong electro-static attraction. These particles can cause electrical shorts if they bridge wire bonds or conductive paths. A thin coating (2-5 microns) of parylene can be applied to immobilize particles and prevent electrical failures.
This benefit has been required by NASA in some applications to help ensure their system are reliable in space.
Parylene vapor that is under vacuum in the deposition chamber has high molecular activity. It is able to completely penetrate spaces as narrow 0.01mm. It has the ability to penetrate beneath and around closely spaced components.
For a tube, Parylene C will evenly coat a distance into the tube that is 5 times the diameter of the tube and 40 times the diameter for parylene N.