Parylene – A unique coating
Parylene is indeed unique as a barrier film. Few other conformal coatings can match the scope of benefits offered by Parylene. The strengths of this chemistry, regardless the application, is further elaborated here.
However, the weakness of parylene can be summed up in a few sentences:
- Parylene is a soft film. It does not have great mechanical or “cut” resistance.
- Parylene deposition is slow. It is a CVD batch process. The advantage is in packing the chamber and securing a certain “economy of scale”. Otherwise, due to the slow deposition rate, the price, the throughput and the turnaround time are negatively impacted.
Great strides are being made in the deposition rate and in various other areas designed to improve parylene’s value proposition. Thin Film Partners is involved in several of these and will be the first to bring you the latest in process development and improvements in equipment.
The key Parylene characteristics or properties:
- Chemically inert. Parylene is stable and does not readily react with any other substance or chemical.
- Non-toxic. It is routinely used in medical and bio-medical applications.
- Bio-compatible. Parylene is used in stents, pacemakers, internal defibrillators, guide wires, ultrasound devices, hearing aids, surgical instrumentation, tubes and elastomers …in implants and almost every medical product that communicates directly with the human body.
- Clean/Sterile. Parylene does not promote the growth of biologics. Its surface is unsuitable for the proliferation of bacteria and other pathogens.
- Ideal dielectric properties. One variant has a dielectric standoff of 5,400 volts at 1 mil thickness.
- Pinhole free. Parylene is an excellent film against water/moisture ingress. Coated parts, even at micron thickness, can withstand and protect against water damage for prolonged periods.
- Chemical resistance. Parylene is impervious to acids, alkalis, olefins, and organic solvents – almost everything. Parylene is the preferred protective barrier for magnets, cameras and other products that must pass through the highly acidic digestive tract. Parylene-coated electronics can survive salt exposure and is employed in delicate and hi-value, mission-critical electronics.
- Uniform and Conformal. The Parylene process is a controlled Chemical Vapor Deposition, where the film is deposited one molecule at a time, and it is completely uniform. A layer of this material can uniformly coat around the contours of the tip of a syringe needle. Its crevice penetration is precise enough to even coat the inner diameter of that needle. It does not pool around corners, form a meniscus (or occlude pores and crevices).