What is Parylene?
Parylene – The coating
Parylene is an organic polymer, generically known as Poly (p-xylylene). This thin film coating is linear, amorphous and crystalline (10%), when in polymer form.
The Parylene film is created via a controlled Chemical Vapor Deposition (CVD) process.
This involves the vaporization and subsequent pyrolysis of a feedstock (Dimer), resulting in the formation of a monomer, that is then polymerized in a vacuum chamber (at low pressure and at room temperature).
The Parylene process starts with the dimer. This is vaporised to a monomer and polymerised in a room temperature chamber
Parylene is unique among conformal coating. It is a polymer with properties unmatched by most other conformal coating films.
The key Parylene characteristics or properties include:
- 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 di-electric properties – one variant has a di-electric 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).
Parylene is not a new material. First discovered in the late 1940’s, it found its first use as a protective film in the aerospace/aviation industry.
Later, applications evolved to include every business sector, including automotive, medical, military/defense, MEMS, nanotech, LED and other specialty arenas.
The area of fastest growth is in the Medical field where parylene is increasingly used as a passivation barrier for sensitive components and electronics. The human body, with all its salts, moisture, fluids and chemicals, presents a harsh environment. Parylene is the barrier film of choice for all of these.
It is approved by the FDA and is cited in numerous publications, from Medical to Scientific and Engineering.