Ruggedized products are conceived for use in severe conditions, environments where excessive moisture or dryness, extreme temperatures, high levels of vibration, wind, or lack of atmosphere are the rule. Internal components of these specialized products require the same degree of ruggedization as exteriors.
Parylene Coating Blog by Diamond-MT
Parylene's benefits as a conformal coating are well known. It resists heat, cold, moisture, and pressure; salt spray, electricity, and solvents can't permeate it. And while these attributes of parylene contribute to the conformal coating's appeal, they also present distinct challenges, particularly in regards to parylene removal, rework, and repair.
More and more, cars aren't just made of steel, aluminum, plastic and silicon. Parylene is becoming one of the most useful tools in an automaker's arsenal. From protecting internal sensors and circuit boards to keeping LED indicator lights bright and color-accurate, Parylene conformal coatings are an important part of protecting today's sensitive automotive electronics.
Coronary stents are tubular medical implants that serve as a scaffold to open clogged or narrowed arteries in an effort to increase blood flow and reduce the potential for adverse cardiac events such as heart attacks. And providing critical support to these support structures is parylene conformal coating.
Military and defense equipment are put to the test and subjected to uniquely harsh conditions on a daily basis. These mission-critical products must be rugged and able to withstand extreme weather and temperatures, exposed forces of gravity that are well above and beyond normal situations, and a range of contaminants such as salt, water, and fungus. Luckily, the application of a parylene conformal coating to relevant electronics can ensure that components are fit for duty in the military and defense industries.
Whether the application is a medical device, a printed circuit board (PCB), or a light-emitting diode (LED), a parylene conformal coating is typically applied to protect the product. Sometimes, however, the product actually has to be protected from the parylene conformal coating—or at least parts of it do.
Parylene conformal coating boasts a bevy of benefits and properties that make it an appealing choice for a variety of medical device applications. Chief among parylene’s advantages for medical applications, however, is that it meets USP Class VI and ISO 10993 biocompatibility requirements—a characteristic that is essential for many critical medical products and that other types of conformal coating sometimes lack.
Conformal Coating Selection: Weighing the Pros and Cons for Your Application
Plastics and polymers were first being produced, whether on accident or on purpose, in the early 1930s. Dupont's Teflon, or PTFE, is probably the most widely known polymer because of its uses in cooking as a non-stick coating for pots and pans. While there are lots of other polymers out there, there are only a few that have as many uses as PTFE, one of which is Parylene.
Parylene was developed by a chemist named Michael Szwarc while he was running experiments on chemical bonds between carbon and benzene rings. While heating para-xylene, he discovered a precipitate in his equipment that turned out to be small and tube-like. He correctly identified these tubes as the polymerization of p-xylene. After a brief period known as Szwarcite, Parylene soon found uses in the medical field as an excellent hydrophobic barrier, but has been found to have plenty of other uses in electronics; metal, rubber, and surface protection from corrosion and outside elements; and as a friction reducing coating especially with needles.
PTFE's discovery, on the other hand, was purely accidental. While working with gasses for refrigeration in the Dupont laboratories, Dr. Roy Plunkett thought that a canister containing TFE was not working. After cutting the canister in half, he discovered a white flake that had developed in the tank and correctly guessed that the flake was a polymer. After conducting several tests on the flakes, since TFE was widely thought to be impossible to polymerize, Plunkett discovered that it was insoluble in anything he tried, as well as being completely inert. The first applications for PTFE were on the seals for the atomic bomb, but it also worked as the nosecone for proximity bombs because it is transparent on a radar and resists electricity.
Parylene was the first vapor deposited polymer ever discovered, and because of the vapor deposits and the fact that no solvent or catalyst is used to cause the polymerization it has a one hundred percent yield, which makes it an extremely efficient polymer to manufacture. Because it is hydrophobic and biostable, parylene has been used extremely effectively as a coating for medical tools, instruments, and hoses. It's strong resistance to corrosion make it an excellent metal coating for scalpels, hypodermic needles, and other metallic tools. It also works as a micro barrier since its surface is impermeable above thicknesses of 1.4 nanometers. Its uniformity helps it adhere to sharp edges and points, again pointing to its widespread use in the medical field.
Unfortunately, because of its formation, it cannot be applied through a solvent. This means that the only way to coat an object in parylene is during the production of the polymer which occurs in a vacuum. While the object to be coated remains near room temperature, which aids in the safety of the process, and the coating is universal and uniform, it does mean that the polymer cannot be put into an aerosol can or produced en mass for consumer use.
PTFE can be made in one of two ways, each resulting in a different looking product, but by and large the same end result. With suspension, TFE is polymerized in water and results in the PTFE forming grains, whereas dispersion causes the PTFE to form as a milky paste. Both the paste and grain are processed and used to coat various products. Although PTFE itself is non-toxic, some of the byproducts of the manufacture process are toxic and at high heats the PTFE itself can emit toxic gasses.
So you'd like to know a little something about parylene conformal coating, but were afraid to ask. You need not be ashamed. The process is so fundamental to electronic manufacturing that it can very easily be taken for granted.