5 Key Properties of Parylene
Posted by Sean Horn
Tuesday, January 7, 2014 9:42
@ 9:42 AM
Since its discovery in the 1940s, Parylene has skyrocketed to prominence as an ideal conformal coating choice for a range of applications. Given its unique blend of properties, it might seem like an unparalleled conformal coating option. In many ways, it is. Here are five key properties of Parylene that differentiate it from the rest.
Parylene possesses exceptional electrical properties, notably its low dielectric constant and high dielectric strength. These attributes establish Parylene as a desirable coating candidate for an array of applications across multiple industries. Of course, Parylene has long been used in the electronics sector as a coating for printed circuit boards (PCBs), in particular. The use of parylene to coat PCBs serves to protect the board from electrical interference while allowing the design of smaller, more compact boards. Furthermore, parylene’s status as a dielectric make it an attractive option for medical implants because it forms an electrical barrier between the device’s electronics and the electrical signals produced in the body. Although parylene is inherently equipped with high dielectric strength, designers can increase dielectric strength, if necessary, by applying a thicker coat of parylene to the substrate. Other considerations may arise in such cases, however.
Broad Temperature Stability
Another one of parylene’s unique properties is its ability to withstand temperature extremes. Demonstrating thermal endurance, Parylene C can reliably perform in air for 10 years at 80 degrees Celsius without significant loss of physical properties. In a vacuum, however, Parylene can perform in temperatures in excess of 200 degrees Celsius.
Parylene handles cold temperatures, too. Even at -165 degrees Celsius, the coating can be folded in half and back six times before cracking. Heating the coating from two degrees above absolute zero to room temperature won’t affect it; the coating will be just as strong from both a physical and dielectric standard as it was previously.
Another one of parylene’s many great properties is its high degree of chemical resistance. At room temperature, for instance, parylene demonstrates excellent chemical resistance to acids, bases, and solvents. In fact, it can’t be dissolved in organic solvents up to 150 degrees Celsius.
Parylene also withstands more common chemicals. As per military specifications, it can withstand a 100 hour salt spray test without affecting performance, for example. It also is chemically inert, thereby relatively unaffected by acidic or alkaline elements. These particular properties make parylene well suited for use in medical implants, which are placed inside the human body.
Chief among parylene’s desirable characteristics is its biocompatibility. Compliant with USP Class VI biocompatibility requirements, parylene is a viable and proven coating option for a range of medical device applications. Consequently, engineers can leverage the manifold benefits of the conformal coating to enhance life-critical and life-saving products. Medical implants such as stents, for example, reap the additional benefits of parylene’s dry-film lubricity, which facilitates implant placement, and its use as a drug-delivery vehicle. Parylene is also suitable for use in a range of applications that span catheters, needles, electrosurgical tools, medical electronics, and cardiac-assist devices.
Parylene stands out from the pack owing to the degree of conformability, uniform nature, and pinhole-free appearance. Circumventing the need for an intermediate liquid stage, the vapor deposition process by which Parylene is applied prevents voids and ensures that all exposed substrates are effectively and uniformly coated. As a result, the process is ideal for coating complex geometries and topographies that may be exposed to harsh environments.
These are just five of the many properties, characteristics, and benefits that have established parylene as the gold standard of conformal coatings. It is leveraged by markets and groups that span the medical device industry, electronics industry, Department of Defense, and NASA, and has provided valuable protection to applications ranging from life-saving medical implants to PCBs on satellites orbiting the Earth.