Parylene is a transparent polymer that offers uniform and pinhole-free conformal coatings for printed circuit boards, medical devices, and microelectronics. Varieties of parylene are made available through a modification of the molecular structure of para-xylylene (Parylene N, C, D, and F-AF4, and F-VT4). Each modification results in a set of material properties that are applicable in different service conditions.

Parylene conformal coatings are highly reliable and are highly sought after in applications such as military sensors to medical implants. Because, parylene coatings are colorless (transparent), thin (micro-scale) and uniformly deposited all over the target surface they are hardly visible to the naked eye. However, there are methods to detect or test the quality of the coatings that are designated by standards (MIL-STD, ASTM). These standards test coatings for the encapsulation properties of Parylene conformal coatings depending on where they will be used.  Leakage current and accelerated lifetime tests under different conditions (salty water, temperature, etc.)

Conformal coatings provide a long-term, stable and reliable encapsulation method for the electronic components from the environmental effects. Different industries and service conditions calls for different protective coatings. In some cases, changes in the requirements or mistakes would call for action to remove the coating. While some coating materials are easily removed, some are virtually impossible to remove without damaging the products (eg. epoxy) . The coating removal process has been standardized by the standard IPC-7711C/7721C titled Rework, Modification and Repair of Electronic Assemblies [1]. According to the IPC-7711C/7721C coating removal starts by the identification of conformal coating (Chart. 1) type and followed by the selection of the method to be used depending on the substrate and components. If prepared onsite the coating material is generally known, but if the coating was done elsewhere the following chart can be used to identify the type of conformal coating.

Polyurethanes (Urethane Resin- UR) are polymeric, flexible, insulating, hard and chemically resistant (Acid—Alkali—Salty water) conformal coatings that are used to protect electronic parts from chemical corrosion, oil, moisture, fungus, and static discharges. Polyurethane coatings are supplied as single or two-component formulas. These coatings are suitable for printed circuit board applications such as sensors in the oil and gas industry, automotive, agriculture and common electronics. Polyurethane can be optically excited under UV-light and fluoresces therefore its inspection is also straightforward. Optically transparent coatings with a bit of tint are visually suitable for encapsulation purposes. Maximum service temperature for these conformal coatings (depending on the type) is ˂130 °C.

Parylene films are highly employed in different applications because they are chemically inert, transparent in the visible range of the solar spectrum, offer high dielectric strength and insulation resistance, low moisture vapor transmission and gas permeability rates [1]. They can also be deposited as void-free layers on complex geometries in deep, narrow crevices.

Company meets strict requirements for aerospace and defense markets in the Southeast.

Implications of Parylene Coating Thickness:

Today, security systems rely on different types of advanced, intelligent and connected sensor technologies. Application areas are diverse: radar systems, vision, night vision (IR-cameras), acceleration- orientation-location detection (accelerometers, gyroscopes, GPS), chemicals (neural toxins, other toxic gasses, liquids, materials), wearable sensors (body temperature, relative humidity, location detection), barometric (under water), air flow (aerospace, missiles) and they are brought together for multifunctionality on PCB’s which carry many sensor at a time. Sensors used in military applications pose stringent requirements such as robustness under severe environmental conditions and require longevity of sensing functions. Some of the environmental conditions that are harsh on sensors can be listed as:

At Diamond MT, we offer parylene coatings of different polymeric varieties (N, C, and F) as listed in the following Table. The basic parylene molecule is the Parylene N (poly-para-xylylene) monomer. Modification of the Parylene N monomer by a functional group such as Chlorine and Fluorine leads to Parylene C (poly(2-chloro-para-xylylene)) and Parylene F, respectively. The derivatization of new varieties can be done by the addition of functional groups to Paryelene N main-chain phenyl ring and its alip

Parylene is a transparent polymer offering uniform and pinhole-free conformal coatings. Different varieties of parylene (Parylene N, C, D, AF4, and F) formed by a modification in their molecular structure. Each modification results in a set of material properties that are applicable in different service conditions. The basic type of parylene derivatives is the Parylene N (poly-para-xylylene) monomer.