Parylene is a conformal coating exhibiting extraordinary properties such as high mechanical strength and biocompatibility. It is a transparent (colorless) film in the UV-V is range of the solar spectrum (Parylene N and C absorb below ≈280 nm). The high transmittance of the polymers in the visible region (90%) make them eligible for use in optical applications. For further information on the optical properties of Parylene you can visit “Parylene’s Optical Properties and Performance”.Read More
Parylene Coating Blog by Diamond-MT
Parylene is a chemically inert conformal coating . It has a well-established chemical vapor deposition process and patterning methods. It is a great candidate for use in various application areas (health, aerospace, oil and gas, microelectronics, and so on.) due to its mechanical, physical, optical and chemical properties. Parylene is known to withstand highly corrosive environments and it can be utilized as a barrier material against various etchants in different processes (e.g. Hydrofluoric acid (HF), nitric acid, and acetic acid; potassium hydroxide; and tetramethylammonium hydroxide).Read More
The stability and insulation property of Parylene conformal coating is critical for the reliable operation of electronic devices throughout their lifetime (PCBs, MEMS, sensors, implants and so on.). The failure mechanism of the conformal coating layers is known to be due to pore formation, blistering, delamination and thinning or pinhole formation due to dielectric breakage of the coating over time , . Therefore, the surface where the interface between the conformal coating and the substrate will be formed is of high importance. The cleanliness of this surface has a great impact on the final results of the conformal coating process and the coatings durability. At Diamond MT we provide professional surface cleaning services ensuring the long lasting results for your components. Also, the parylene conformal coating thickness and parylene varieties required for different service are considerations to take into account. We offer our professional services to direct our customers. Some of the variables of different service conditions can be listed as:Read More
Poly(para-xylylene) derivatives (parylenes) are used as conformal coatings in a wide range of applications in the automotive, medical, electronics, military and semiconductor industries. They are inert, transparent and have excellent barrier properties as dielectric thin films. Because their deposition takes placeunder vacuum sub-micron range crevices can be coated leading to excellent barrier properties (void free) and they have extraordinary purity that is of great importance in electronic applications. Not all parylene derivatives show same dielectric properties (Table 1). It is also important to note that dielectric properties of parylenes depend on their thickness thus their %crystallinity which is explained below.Read More
The answer is “No!”Read More
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:Read More
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 alipRead More
The polymer parylene (XY) is a reliable protective conformal film that safeguards the visual clarity and color of printed circuit boards (PCBs), similar electronic assemblies and other products. XY optical clarity seldom diminishes to the extent either the coating or the underlying substrate becomes visually indistinct, although over-exposure to ultraviolet (UV) light may eventually interfere with optical perception. However, in the majority of cases, colorless parylene generates advantageous optical properties for a wide range of uses -- including artwork/museum artifacts, cameras/sensors, computer touchscreens, healthcare/medical devices, light-emitting diode systems (LEDs), and optoelectronic components maintaining consistent aerospace, scientific, and telecommunication operations.Read More
A natural process, corrosion enacts chemical/electrochemical reactions that degrade and gradually destroy materials or components within a functional environment. The outcome can be dangerous and costly to repair.Read More
A primary function of all conformal coatings is maintaining sufficient insulation and avoiding dielectric breakdown while protecting printed circuit boards (PCBs) and related electronic assemblies. Providing a completely homogeneous coating surface, parylene (XY) conformal coatings are exceptionally corrosion-resistant, dense and pinhole-free. Among other performance advantages, ultra-thin XY protective films offer superior dielectric properties. Dielectric substances maintain electrical insulation, simultaneously transmitting electricity without conduction. They have the potential to store energy because they support electrostatic fields that release only low levels of thermal energy.Read More
Conformal coatings primary purpose is protecting the performance of highly sophisticated electronics such as printed circuit boards (PCBs), sustaining their functionality through often unfriendly operating conditions. Among the most important coating-requirement is safeguarding PCBs from the negative impact of moisture incursion. Sources are many. Liquidized obstacles to appropriate assembly function can result from unwanted contact with acid rain, aggressive solvents, atmosphere pollutants, chemicals, fog, high humidity, intermittent immersion, persistent rain, snow, salt water/mist and wet sprays of any kind.Read More
Chemically inert parylene (Poly-para-xylylene/XY) conformal film is often selected because its micron-thin protective films generate precise coating uniformity, regardless of substrate topography. To this extent, XY far exceeds the capacities of liquid materials – resins of acrylic, epoxy, silicone or urethane – for a wide range of coating assignments. It is true that pre-synthesized liquid coatings are easier to apply. However, their conformal films are dimensionally thicker, making them difficult to position in constricted operating spaces. Liquids are also generally less resistant to contaminant incursion and other problems that interfere with reliable performance of printed circuit boards (PCBs), and most other contemporary electronics, including biomedical implants.Read More
A specialized chemical vapor deposition (CVD) process attaches conformal coatings composed parylene (XY) to substrates. CVD uniformly encapsulates all exposed substrate surfaces as a gaseous monomer; completely eliminating wet coatings’ liquid phase and need for post-deposition curing. Synthesizing in-process, CVD polymerization requires careful monitoring of temperature levels throughout.
Beneficial thermal properties of XY protective coatings include reliable performance through an exceptional range of temperatures. Parylene is available in variety of material formats, prominently Types C, N, F, D and AH-4. Each has a particular range of properties that determine its optimal uses. Types C and N exhibit faster deposition rates than other parylenes, making them useful for a wider range of coating functions. However, operating temperature is a significant determinant of use: Much depends on chemical composition.
- Used more frequently than other XY varietals, Parylene C is a poly-monochoro para-xylene. It is a carbon-hydrogen combination material, with one chlorine group per repeat-unit on its main-chain phenyl ring. In oxygen-dominated atmospheres, C conformal films regularly provide reliable assembly security at temperatures of 100° C (212° F/water’s boiling point) for 100,000 hours (approximately 10 years). C is suggested for use in operating environments reflecting these temperature conditions. Chemical, corrosive gas, moisture, and vapor permeability remain consistently low. C generates exceptional vacuum stability, registering only 0.12% total weight-loss (TWL) at 49.4° C/10-6 torr (1 torr = 1/760 SAP (standard atmospheric pressure, 1 mm Hg). C can also be effective at temperatures below zero, to -165º C.
- With a completely linear chemical format, Parylene N is the most naturally-occurring of the parylene series. Used less regularly than Type C, N is highly crystalline; each molecule consists of a carbon-hydrogen combination. N’s melting point of 420° C is greater than most other XY types. Vacuum stability is high, registering TWL-levels of 0.30% at 49.4° C, and 10-6 torr. These properties encourage higher temperature applications. Compared to other XY varietals, N’s low dielectric constant/dissipation values also recommend uses with assemblies and parts subjected to higher levels of unit vibration during operation. N’s electrical/physical properties are not noticeably impacted by cycling from -270º C to room temperature, adding to its versatility.
- Parylene F has fluorine atoms on its aromatic ring. Possessing aliphatic -CH2- chemistry, F’s superior thermal stability is attributed to this aliphatic C-F bond, compared to Type C’s C-C bond. Better thermal stability, and reduced electrical charge/dielectric constant expand its use for ILD (inner layer dielectric) applications, such as those for ULSI (ultra large-scale integration), where a single chip can incorporate a million or more circuit elements. F is a good choice for many microelectromechanical systems (MEMS)/nanotech (NT) solutions.
- Originating from the same monomer as Type C, Parylene D’s chemical composition contains two atoms of chlorine in place of two hydrogen atoms. Like Type C, D conformal films can perform at 134° C (273° F), dependably securing assembly performance in oxygen-dominated environs for 10 years, at a constant 100° C. Parylene F resists higher operating temperatures and UV light better than C or N.
- Parylene AF-4’s melting point is greater than 500° C. It survives at higher temperatures/UV-exposure better than other parylenes for long durations because it possesses CF2 units, situated between its polymer-chain rings.
Parylene (XY) polymers provide robust, dielectric, micron-thin conformal coatings for a considerable range of electronic devices, most prominently printed circuit boards (PCBs). XY’s unique chemical vapor deposition (CVD) application method synthesizes in-process, depositing gaseous parylene deep into a substrate’s surface. CVD occurs on a molecule-by-molecule basis, conforming to all underlying contours, regardless of shape or position, to the nanometer, if necessary. Pre-synthesized liquid coatings lack many of parylene’s performance properties, having far less ability to successfully and conformally penetrate crevices in the substrateRead More
Parylene (XY) polymer conformal films are recognized for their exceptional range of desirable functional properties for coating printed circuit boards (PCBs) and similar electronics. Beneficial properties include biocompatibility, chemical/solvent resistance, dielectric/insulative reliability, and ultra-thin pinhole-free film thicknesses between 1-50 μm. They also generate complete surface conformability, regardless of substrate configuration, exceeding the coating capabilities of liquid conformal materials, such as acrylic, epoxy, silicone and urethane.Read More
For conformal coatings, elongation is a measure of material ductility -- a specific coating's ability to undergo significant plastic deformation before rupture. A coating’s yield elongation is the maximum stress the material will sustain before fracture. Thus, computed parylene (XY) elongation measurements represent the total quantity of strain the conformal film can withstand before failure. While elongation is equal to a material’s operating failure strain, it has no exclusive units of measurements. Typically,Read More
Protecting printed circuit boards (PCBs) and similar electronics from the incursion of water is an essential responsibility of parylene (XY) conformal coating. Suitable XY permeation barriers assure no form of liquid passes through to underlying components and that the water vapor transmission rate (WVTR) is minimal. WVTR measures the level of water vapor migration through the applied barrier film, in terms of area and time. Optimal WTVR ratings are represented by lower numerical values. In comparison to liquid coatings, parylene typically provides lowest-level values, indicating better moisture barrier provision.
Acrylic, epoxy, silicone and urethane coatings can be more quickly affected by water, its vapor, and other sources of moisture, such as:
- acid rain,
- mists of other airborne pollutants,
- salt-air and
- chaotic weather.
As the electrical components used to power printed circuit boards (PCBs) grow smaller, conventional conformal films become less effective for coating them. Ongoing development of microelectricalmechanical systems (MEMS) and nano technology (NT), has little room for the thicker conformal films provided by liquid materials, such as acrylic, epoxy, silicone and urethane. Nanocoats (NCs) are increasing in prominence, frequently surpassing micro-thin parylene (XY) for many MEMS/NT purposes.Read More
Hydrophobic Basics and HydrophilicityRead More
With reliable moisture barrier properties, parylene (XY) conformal coatings generally have a hydrophobic surface when deposited onto substrates, causing liquids to form separate droplets on film surfaces. While this outcome is useful for many XY applications, greater hydrophilic response, wherein XY molecules form ionic or hydrogen bonds with water molecules, can also be desired. This can be achieved by applying glue or epoxy on top the deposited parylene; surfaces acquire enhanced hydrophilic properties, becoming more wettable.Read More
Parylene: Properties and ProcessesRead More
Taber tests are designed to measure a material’s capacity to withstand abrasion and its effects during operation. Conformal coatings – both liquid and parylene (XY) – areRead More
Unlike liquid coatings – acrylic, epoxy, silicone and urethane – parylene (XY) does not use wet method application. It can neither be brushed or sprayed onto substrate surfaces, nor will immersion – soaking the substrate in a bath of coating material – work. In addition, XY’s:Read More
Although parylene (XY) is a well-recognized and often used conformal coating, misconceptions about what it is and can do are common. These mistaken beliefs interfere with true understanding of parylene’s uses. Five of the most consistent misconceptions – and appropriate corrective information – should clear things up.Read More
Permeation barriers for electronic devices are essential to assure their ongoing performance through a wide range of operational environments. Polymer flexible conformal coatings provide good barrier protection, protecting device substrates from unwanted incursion by solid contaminants, chemicals, gaseous permeation and liquid water or vaporous forms of moisture. Permeability reduction improves with enhanced coating adhesion, minimizing the surface’sRead More
Parylene (XY) conformal coatings are known and recommended because of their many beneficial performance characteristics. They provide uniform, pinhole-free protective films with excellent barrier/dielectric/insulative properties, able to conform to virtually any substrate configuration. One property in particular – micron-thin coating layers – distinguishes XY from liquid coating materials such as acrylic (AR), epoxy (ER), silicone (SR) and urethane (UR), which need to be applied at least twice as thick in most cases and frequently more, limiting their range of uses. Parylene typically is applied at 0.1 to 50 microns (0.004 -2 mils), while the thicknesses of liquid coatings generally range from 25 to 250 microns (1-10 mils). Compared to liquid processes, gravity and surface tension generate negligible impact with parylene, eliminating film bridging, pinholes, puddling, run-off, sagging or thin-out during application. XY’s coefficient of friction coefficient can be as low as 0.25 to 0.30.Read More
Of the five most commonly used conformal coatings, four – acrylic (AR), epoxy (ER), silicone (SR) and urethane (UR) – are classified as wet materials, meaning they are applied to substrates by three basic types of liquid-based technology:Read More
Each conformal coating material exhibits a range of unique performance properties that determine its product uses. Relevant factors include the required coating-thickness necessary to assure reliable performance. Like other coating types, parylene (XY) layer thickness is largely a function of several factors: (1) substrate material, (2) the kind of assembly being covered, and (3) its operational purpose. Chemically inert parylene is effective at far-thinner application thickness than liquid-applied materials for coating printed circuit boards (PCBs) and related electro assemblies:Read More
After pertinent research you’ve determined parylene (XY) is the best conformal film for your coating assignment. Especially relevant were XY’s uniform protective and insulative properties, which are useful for numerous applications, ranging from printed-circuit boards (PCBs) to medical implants to military-grade purposes. Among parylene’s other advantages are:Read More
Liquid conformal polymers – resins of acrylic (AR), epoxy (ER), silicone (SR) and urethane (UR) – use wet application processes to attach to substrates. Most prominent of these are brushing the wet coating onto an assembly, dipping (immersing) the assembly in a bath of liquid coating, or spraying the conformal film onto the designated surface. The coating materials are wet when they are applied. IfRead More
Unlike liquid conformal coatings joined to substrate surfaces by wet application methods, polymeric parylene (XY) uses a unique chemical vapor deposition (CVD) process to assure adherence. There is no intermediate liquid phase. Rather, cross-link polymerization of powdered raw XY-dimer converts the solid to a vapor at the molecular level, polymerizing XY directly as a transparent film on assembly surfaces.Read More
Dielectric strength is a measurement of a conformal coating’s insulation effectiveness. The higher the numerical designation of strength, the more likely a coating is to resist dielectric breakdown -- a level of 7,000 is dielectrically stronger than 2,200. Conformal coatings with higher hydrophobic properties and lower extractible ionic impurities are less likely to attract water, rendering them less mobile, while enhancing existing dielectric strengthRead 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
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
The parylene variants are resistant to solvents and protect substrates solvents. This high level of security is maintained through temperatures of 150° C, seldom encountered in the actual use of PCBs or related electronics. These properties are largely a development of the unique molecular structure of parylene polymers, rendering them:Read More
Although its basic component is remarkably small – with 25,400,000 nanometers included in just one inch(!!) -- nanotechnology encompasses a growing, interdisciplinary field with an unlimited future. Nanowires and nanotubes are used in transistors for printed circuit boards (PCBs) and associated electronic assemblies. Bio-nanobatteries, capacitators, LCDs, and microprocessors represent just a few nano-applications, which include uses for aerospace, agricultural, automotive, consumer, industrial, medical, military and oceanic products.Read More
Despite parylene’s numerous benefits as a conformal coating, it has several disadvantages that should be recognized before it is used. Failure mechanisms that can emerge from parylene coatings have limited its wider scale application in comparison to liquid conformal films such as acrylic, epoxy, silicon, and urethane. In many situations, wet coatings can provide better performance and lower cost (or both) for many applications.Read More
The conformal coating process creates a protective barrier for product substrates. The type of coating material used is a consequence of several conditions:Read More
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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.
For all of Parylene's strengths, it has one key drawback—Parylene's resistance to ultraviolet (UV) radiation is limited. Most formulations of Parylene gradually yellow when exposed to the kind of UV light that's produced by the sun. While this isn't a problem when Parylene gets used to conformally coat a printed circuit board that's sealed in a box, it can be a problem when a display made of Parylene-coated LEDs is installed outdoors.
Parylene offers the best protection against solvents of any conformal coating. It is also brings to the table excellent moisture and gas protection, very high dielectric strength, and is bio-compatible. Even with all of these benefits, there are still some disadvantages to using parylene versus other conformal coatings.
There are a couple different factors that go into decided parylene cost. One of these factors is the material cost. Parylene dimer can be anywhere from $100 to $10,000+ per pound depending on the type and quality. Other raw materials, such as the cleaning materials and adhesion promotion mediums, also factor into the materials costs for parylene.