Accidentally discovered in 1947, by chemist Michael Szwarc, the polymer parylene originally bore his name, and was known for a brief period known as Szwarcite. Working to thermally decompose the solvent p-xylene at temperatures exceeding 1000 °C, Szwarc identified the monomer para-xylylene di-iodide as the only product resulting when para-xylylene was reacted with iodine.Read More
Parylene Coating Blog by Diamond-MT
Available in five basic material types, conformal coatings can be readily adapted as protective, insulating films for electronics. However, there can be some confusion about which type is best-suited for a specific use. Clearly defining the performance parameters for the component[s] to-be-coated helps coordinate the conformal film material with a unit’s functional requirements. Accurate assessment of environmental conditions like anticipated levels of corrosion, contact with foreign particulates, expected concentrations of moisture/salt spray, temperature fluctuations and vibrational range determine which coating type is best-suited to your electronics’ applications. Without appropriate protection, printed circuit boards (PCBs) and similar electronics will not survive harsh environments, and malfunction.Read More
Tags: acrylic conformal coating, parylene, silicone conformal coating, urethane conformal coating, rugged electronics, electronics, epoxy conformal coating, ruggedization, conformal coating selection, electronic conformal coatings
If, for some reason, you are told parylene is NOT a conformal coating, simply because it has no liquid phase of application, just walk away. And maybe have yourself a good laugh. For, as you may already know, parylene has repeatedly proven itself to be the most definitive of conformal coatings, for a variety of reasons, including:Read More
Superior to liquid coatings like acrylic, epoxy, silicone and urethane, parylene conformal films offer unparalleled protection for aerospace printed circuit boards (PCBs) and related electronic assemblies. Their complete encapsulation conforms entirely to all device surfaces – flat, round, creviced or edged, while adding almost no weight to the covered device.Read More
Selecting the best material/application method for your coating assignment prolongs assembly service-life and promotes optimal performance. The conformal coating industry is highly competitive, with competent providers available throughout the country. Compared to liquid resin coating materials – acrylic, epoxy, silicone and urethane – the polymer parylene generates superior conformal coating, but is more complex and expensive.Read More
Materially, parylene is the most distinctive of the major conformal coatings. But just how does it differ from liquid coatings -- acrylic, epoxy, silicone and urethane??Read More
Contributing to good performance for internal medical appliances, lubricity is a conformal coating’s ability to lower operational friction that might retard its function and endanger patient health. Lubricious coatings offer essential protection for appliances like cardiac-assist devices (CADs), catheters, elastomers, guidewires, and stents. Compared to an uncoated device, lubricious films can reduce frictional forces by more than 90%, dramatically decreasing potential harm caused by excessive insertion-force or internal puncture damage. This relative ease of use is important for implants and similar devices that require navigation throughout the patient’s vascular system or other internal structure; otherwise, patients can suffer from abrasion generated between the device surface and blood vessel walls.
Coefficient of Surface Friction
The degree of physical resistance a device demonstrates is numerically expressed by a coating’s coefficient of friction (µ), which quantifies:
- the magnitude of resistance a surface exerts on substances moving across it, or
- the minimum force necessary for an object to slide on a surface, divided by the forces pressing them together.
Static friction (µs) occurs when an object moves across a stationary surface; kinetic friction (µk) results for two objects simultaneously in motion, moving across each other. Conformal coatings are used in both circumstances, especially for medical implants with moving MEMS/nano-tech components.
Where higher-level surface lubricity is sought, lower µ-values are the objective; they signify lessened frictional resistance, minimizing non-release, dry-sticking challenges that interfere with devices’ performance. For instance, a µ-value of 1 indicates an equal quantity of force is needed to either lift an object, or slide it across a level surface; these calculations compare an object’s weight to the total force required to make it move. Most everyday objects and materials have a coefficient between 0 and 1; values closer to 1 are not feasible for medical purposes. For medical devices, a µ-value:
- ranging from 0.01 to 0.1 is ideal,
- but remains difficult to achieve
- for application to the expansive degree of metallic and polymeric substrates used for medical appliances,
- which require highly-specified levels of abrasion resistance and non-thrombogenic properties,
- in addition to biocompatibility and lubricity.
Appropriate safety standards also need to be met.
Much depends on the materials comprising the touching surfaces. Conformal coatings like Teflon (PTFE) and parylene, which provide high-level lubricity, maintain that level for a prolonged operational duration, making them very useful for specialized medical applications.
Properties of Reliable Coating Lubricity
Lubricated surfaces have lower levels of friction. Wet hydrophilic coatings amass water as a source of lubricity, applied by liquid methods such as dipping or spraying the film substance onto substrates. Applied to catheters or guidewires, they temporarily minimize development of thrombosis. However, their lubricious function decreases with time, dissociating or dissolving from the matrix surface, leaving particulates in tissue or the bloodstream, endangering patient health. Thus, they are less reliable long-term than hydrophobic coatingsRead More
For various reasons, even people familiar with the variety of existing conformal coatings, their strengths, weaknesses and respective use often assume that the chemical vapor deposition (CVD) process used for parylene films incorporates a solvent, as an integral component of the procedure. This is false, for the reasons detailed below.Read More
The value of polymeric conformal coatings for protecting printed circuit boards (PCBs) from functional retardants like dust, corrosion, moisture, and temperature fluctuations has been well-documented. Conforming to the physical configurations of the exposed face of the PCB, conformal coating:Read More