The Internet of things (IoT) allows us to connect everyday things to the internet. It is defined as a network of devices, vehicles, appliances, and other things that are connected. IoT is possible with the use of sensors, actuators, electronics, and software embedded into the later. Data collected from these physical devices are sent back and forth for better operation through network connectivity. A multitude of applications in defense, security, medical and industrial applications are available. Wearable devices, underwater systems, agricultural technologies, smart home applications, automotive, aviation systems and other areas of applications make use of IoT devices.Read More
Parylene Coating Blog by Diamond-MT
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
Multilayer conformal coatings are advantageous in resolving diffusion or stability issues. A vast amount of knowledge is available in the literature about the use of multilayered stacks of Parylene and stacks making use of different intermediate materials such as metals and so on. Mostly, use of Multiple layers of Parylene C was commonly reported for Medical Implants .Read More
Under ambient conditions (room temperature, in air) Parylene is a lifetime conformal coating. The exposure to environmental stressors like temperature, oxygen, UV-light and chemicals can degrade the lifetime especially when two or more are existent at the same time.Read More
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
At Diamond MT we often get the question: “Can my xxx be parylene coated?” The number of substrate surfaces that can be coated with parylene is plenty. In the table below a number of industrial applications that using Parylene conformal coatings are listed. The examples can be extended.Read More
Parylene XY is a transparent, thin (hundreds of nanometers to a few micrometers), well adhering, pin-hole and defect free conformal coating. They are coated uniformly on flat surfaces and component configurations with sharp edges, points, flat surfaces, crevices or exposed internal surfaces are coated uniformly without voids.Read More
Oil & Gas industry makes use of sensors which face extremely high temperature and high pressure (HTHP) environments as in downhole drilling (>200°C and 30 kspi). In US natural gas supply lie in reservoirs below 15,000 ft. Wells at these depths pose environmental challenges of drilling due to the temperature, pressure and gasses. Increasing the lifetime of drilling equipment and possibility for recalibration of sensors that drift at such depths would save millions of dollars if they can be preserved under these HTHP environments. The packaging of sensors is a key element in providing this kind of protection.Read More
Parylene Process:Read More
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.Read More
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.)Read More
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 . They can also be deposited as void-free layers on complex geometries in deep, narrow crevices.Read More
Implications of Parylene Coating Thickness: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
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.Read 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
Parylene (XY -- poly(para-xylylene)) organic polymers are highly regarded through a wide range of industries – aerospace/defense, automotive, commercial, industrial, medical – for their utility as conformal coatings. Chemically inert, colorless, linear/polycrystalline and optically clear, XY coatings provide exceptional barrier protection, dielectric reliability, and insulation for printed circuit boards (PCBs) and similar electronic assemblies whose components must maintain performance through all operating conditions. Parylene conformal films safeguard function in the presence of biogases, biofluids, chemicals, moisture/mist, salt compounds, and temperature fluctuations.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
Company is looking to serve the aerospace, defense, and medical markets in Florida with the new location.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.
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
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
Conformal coatings are used to protect printed circuit boards (PCBs) from dust, humidity/moisture, mildew/mold, temperature extremes, and other elements whose prolonged contact might interfere with assembly function. Coatings also enhance electrical clearance-tolerance, while safeguarding PCB components from contamination (particulate or otherwise), corrosive materials, and mechanical stress.Read More
Originally published in the IPC Proceedings, the article “Effectiveness of Conformal Coat to Prevent Corrosion of Terminals“ was published online by circuit insight (http://www.circuitinsight.com/programs/54223.html). Author Michael Osterman is affiliated with the Center for Advanced Life Cycle Engineering, University of Maryland (College Park, MD).Read More
The value of polymeric conformal coatings for protecting printed circuit boards (PCBs) from functional retardants like dust, corrosion, moisture, and temperature fluctuations is well-known. What may be less known is, that as the electrical components used in PCBs become smaller, traditional conformal films are commensurately less effective for certain coating purposes. With the rise of microelectricalmechanical systems (MEMS) and nano technology, nanocoats are increasing in prominence, in many cases surpassing even micro-thin parylene not-liquid coatings in utility for MEMS/nano applications.Read More
Conformal coatings are non-conductive dielectric film-coverings applied over printed circuit boards (PCBs) to protect them from damage caused by chemical incursion, corrosion, current-leakage, dirt/dust, extreme temperatures, fungus, moisture, rain, salt-spray, wind and persistent, intensive vibrations both within and external to the device. These failure mechanisms can soon lead to PCB malfunction and eventual breakdown. Rugged coatings’ exceptional performance durability and versatility protect delicate, finely-tuned components.Read More
Long used to safeguard printed circuit boards (PCBs) and other essential automotive electronics from harsh operating environments, conformal coatings’ importance in auto-design/manufacture has never been greater. Fragile electronic components and the paths between them require protection for PCBs to perform reliably. Conforming to PCBs’ topographies, coatings insulate assembly components, safeguarding specialized electronics’ functional integrity through extreme operating conditions.Read More
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
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
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
The acronym UAV stands for an unmanned aerial vehicle, an aircraft piloted by remote control or onboard computers. UAVs are an integral element of America’s unmanned aircraft system (UAS), consisting of three basic components:Read More
Like any other renewable energy technology, electronics for solar (photovoltaic) panels are necessary for transforming, transmitting, and monitoring the system. Unfortunately, system electronics can be fragile, and frequently are the panel’s weakest link. Converting the sun’s light to electricity, solar panels have demonstrated their utility in numerous operational contexts. The basic operational unit of panels, the solar cells themselves, can be used to power small scale products like calculators, re-chargeable batteries or watches; full panels can be adapted to a range of larger level operations, like powering homes, lighting systems or water treatment plants.Read More
Applied as a conformal coating through a unique chemical vapor deposition (CVD) process, parylene provides micron-thin, resilient barrier protection for an exceptional range of electrical assemblies. In comparison to liquid coatings -- acrylic, epoxy, silicon, urethane -- parylene is the coating-of-choice for protecting printed circuits boards (PCBs) and medical devices. It’s films negate the impact of gravity and surface tension during the coating process; .Read More
The parylenes consist of a range of para-xylylene polymers whose desirable physical and electrical properties support expansive utilization as conformal coatings for electronic and medical devices Parylene films are applied to substrates via a chemical vapor deposition (CVD) process, which deposits monomeric parylene vapor homogeneously and deeply into the surface of printed circuit boards (PCBs) and related assemblies/components.Read More
Perhaps the most reliable of the conformal coatings, parylene (para-xylylene di-iodide) is also one of the more expensive coating options. Production costs typically encompass three primary expense categories -- raw materials, labor, and lot volume. Of the three, labor expenses are generally the most costly, but raw materials can add significantly to production overhead; materials’ costs can be largely attributed to the raw parylene dimer required to make conformal coatings.Read More
Wearable devices have become familiar, ever more an integral component of everyday life, with expanded uses for many conventional activities. Advanced med-tech -- ranging in format from external exercise monitors to implanted cardiac pumps, defibrillators and deep-brain sensors –- represent only a fraction of wearable medical devices currently applied for healthcare and treatment. Smartphones and watches can be found everywhere; smart fabrics are used with increasing frequency for clothing and textiles. Wearables reflect the expanding scope of the Internet of Things in most areas of human endeavor.
As use of wearables grows, manufacturers try to determine the optimal mix of form, function and technology that will encourage further consumer/ professional application of the devices. In healthcare, wearables provide a range of status indicators (heart rate, physical activity levels, etc.) that monitor individual’s engagement of healthful (or unhealthy) activities. In addition to focusing on improving their functional technology, battery life and consumer fashion, the need to safeguard wearables performance is a prominent concern. All wearable devices are informed by technologies that need conformal protection for and from their functional environments. Parylene films are the most appropriate choice for protection in just about every case.Read More
Outgassing occurs when previously adsorbed or occluded gases or water vapor are released from some material. With respect to protective conformal coatings, outgassing encompasses the discharge of gases previously confined within a high-frequency printed circuit board (PCB) or similar assembly material, often resulting in functional difficulties.Read More
Applied in a gaseous form to component surfaces through a chemical vapor deposition (CVD) process, parylene (Poly-para-xylylene) films protect printed circuit boards (PCBs) and similar electrical assemblies. Gaseous CVD application supports efficient coating of complex component surfaces characterized by crevices, exposed internal areas, or sharp edges. Depending on the specific use, parylene conformal coatings can be effective in the range of 0.1 - 76 microns' thickness, far finer than competing coating materials. Equally as strong, adaptable and versatile parylene protects substrates withRead More
While parylene provides a reliable, versatile conformal coating, it can require removal. When circumstances necessitate removal of liquid coatings – acrylic, epoxy, silicone or urethane – a wide range of chemical solvents can be used to detach the film from the underlying substrate. No single chemical material/process is equally successful for all uses, but solvent processes are employed most frequently because they do the least damage to printed circuit boards (PCBs) and their components. Such is not the case with parylene.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
The engineering of functional systems at the molecular scale, nanotechnology encompasses management of individual atoms, combined into effective working units, often complex as machines. Yielding advantages like enhanced chemical reactivity and strength than larger-scale structures, they offer greater control of the light spectrum and weigh significantly less. Incredibly small, one nanometer is a billionth of a meter (10-9 of a meter) -- one inch equals 25,400,000 nanometers; more illustratively, a sheet of newspaper is 100,000 nanometers thick.Read More
Parylene deposition takes place at the molecular level. Applied at room temperature through CVD processing, the typical thickness of parylene conformal film is in the microns-range.Read More
Biocompatible parylene conformal coatings provide superior protection for medical stents. They represent an enabling technology consistently applied to medical devices of all types for 35 years, to diminish problems stemming from surface microporosity and consequent biofluid corrosion after implant. Providing a reliable barrier to chemicals and moisture, parylene’s static and dynamic coefficients of friction are comparable to those of Teflon.Read More
A metal alloy of nickel (Ni) and titanium (Ti), nitinol (NiTi) exhibits the properties of shape memory and superelasticity, which make it very useful for adaptation to conformal coatings. However, like parylene, nitinol is often difficult and expensive to produce; the extreme reactivity of the alloy’s titanium component requires exceptionally tight compositional control during combination and manufacture.Read More
Not completely understood, electrically conductive tin whiskers are crystalline structures between 1-2 millimeters (mm) that can grow from surfaces where tin is used as a final finish; surfaces finished with electroplated tin are particularly susceptible to whisker growth. Although their occurrence was originally documented during the 1940s, no real solution has yet been devised to prevent their development, which may reach 10 mm in some cases. This is unfortunate because tin whiskers have the capacity for generating arcing and short circuits between electrical elements of printed circuit boards (PCBs) and related electronic equipment.
Tin Whiskers: Their Origin and Impact
Physically, tin whiskers result from the spontaneous growth of tiny, filiform hairs or tendrils upon tin surfaces. These structures can create electrical paths, often within the presence of compressive stress during component operation. Because they usually develop in a functional environment that supports short circuits or arcing, tin whiskers don't need to be airborne to damage electronics. Among other problems, the four main risks with tin whiskers are:
- Stable short circuits in low voltage, high impedance circuits.
- Transient short circuits may develop where tin whiskers span tightly-spaced circuit elements maintained at different electrical potentials.
- Metal vapor arcs result when a whisker-short occurs in a high-current/voltage environment. They are perhaps the most destructive of electronic system failures attributed to tin whiskers.
- Contamination from debris resulting from tin whisker presence can interfere with component performance.
- Behaving like miniature antennas in fast digital circuits or at frequencies above 6 GHz, generating a negative impact on circuit impedance and stimulating reflections.
- Causing failures in relays, a source of deep concern for relay-functions as important as those for nuclear power facilities.
- In outer space (or any vacuum), tin whiskers can short circuit high-power components, ionizing and potentially conducting hundreds of amperes of current, exponentially increasing the short circuit’s damage.
- Tin whiskers have caused malfunction and recall of medical pacemakers.
- Whiskers located in computer disk drives can break, resulting in bearing failures or head crashes.
Conformal Coatings Mitigate the Effects of Tin Whiskers
Selecting a tin whiskers’ mitigation strategy is important; because the source of their growth is unknown, they cannot be entirely eliminated. Although ceramic coatings have proven successful, conformal films made from polymeric compounds such as vapor-deposited parylene, or wet application acrylic and urethane, deflect whiskers away from the coating surface. For instance, studies conducted by NASA seeking tin whisker control for space craft have shown urethane conformal coatings successfully mitigate tin whisker growth. In addition, some acrylic wet coatings, such as HumiSeal 1B31, also mitigate tin whisker’s problems. For various reasons, other conformal coatings -- epoxy, and silicone – are less effective minimizing the development of tin whiskers and their impact on PCB performance.
Perhaps the most effective conformal coating for alleviation of tin whisker related issues is parylene. Deposited in gaseous form, through a chemical vapor deposition (CVD) process, parylene seeps deep into substrate surfaces, penetrating spaces as minute as 0.01mm. In doing so, it forms a pinhole-free protective film that is ultra-thin but exceptionally durable. Chemically inert and of high tensile strength, parylene retains its stability throughout a wide range of temperatures. Because it can be applied at room temperature, parylene application is stress-free. These properties combine to support superior mitigation of tin whiskers.
. However they are applied, conformal coatings create a physical barrier over electronic components that stops tin whisker damage. Conformal coatings:
- Form a protective film that safeguards assembly circuitry and components, physically separating them from each other.
- Substantially diminish tin whiskers bridging between the separated components.
- Lower whiskers’ capacity to generate arcing and shorts.
Tin whiskers can generate arcing and short circuits leading to systemic failures in PCBs and similar electrical assemblies, significantly damaging and otherwise altering their performance expectations. Vital devices, equipment and facilities such as pacemakers, power plants, and even satellites have had their function diminished by the presence of tin whiskers. Determining methods for preventing or slowing tin whisker growth is difficult because:
- outside of some evidence they are the product of mechanically- and thermally-induced stresses,
- the exact mechanism behind their development is not fully understood.
Where they develop, mitigation of tin whiskers is essential to limiting their impact on assembly performance. Conformal compound coatings such as parylene, and to a lesser extent acrylic and urethane, can stop tin whiskers from;
- penetrating an applied protective barrier,
- bridging electrical components and
- creating arcing or a short.
While it is impossible at the moment to completely prevent the occurrence of tin whiskers, their mitigation with conformal coatings will dramatically limit whisker growth and equipment damage. Vapor-deposited parylene and wet coatings such as acrylic and urethane, provide generally good tin whisker defense. Other traditional wet conformal coating materials such as epoxy and silicone are mostly ineffective as protection against the development and effect of tin whiskers.Read More
High-tech electronic systems increasingly regulate automotive management functions for emissions’ controls, fuel systems, fluid monitoring, lighting, and powertrain mechanics, frequently comprised of miniaturized, multi-layer MEMS/Nano packages. Systems’ survival in hostile vehicular environments typified by condensation, corrosive fluids and vapors, excessive temperatures, humidity and prolonged UV exposure is partially assured by protective conformal coating.Read More
Protection of printed circuit boards (PCBs) is most often achieved with either potting or conformal coating. The selection of which method to use depends upon the PCB’s purpose and how much protection it requires. Potting offers the strongest shielding barrier, but is also affected by a range of operational disadvantages that can offset its functional benefits. Conformal coatings generate reliable barrier protection, which frequently circumvent the problems inherent in potting. This is particularly the case with parylene, a non-liquid conformal coating.Read More
Parylene Varietals: Matching Material to Purpose
A common generic name for Poly-para-xylylene, parylene forms a protective plastic film when applied to substrate surfaces. Application is achieved through a chemical vapor deposition (CVD) process in a vacuum, as a gas to targeted substrate surfaces.Read More
Parylene’s CVD method of application generates exceptionally lightweight yet durable conformal coatings, with superior barrier properties. Compared to liquid processes, the effects of gravity and surface tension are negligible, so there is no bridging, thin-out, pinholes, puddling, run-off or sagging.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
Despite conformal coatings’ ability to dependably protect substrate surfaces of printed circuit boards (PCBs) and related electrical components, problems can sometimes occur which compel their removal. Chemical removal, which does the least damage to PCBs, is fine for wet coating substances like acrylic, epoxy, silicon and urethane. Chemical removal methods are far less successful for parylene, despite the use of a chemical vapor deposition (CVD) process for its film application.Read More
Due to its excellent ability to stop the passage of gases, liquids, or radiation onto circuit board components, parylene is often considered to be the ultimate conformal coating for the protection of devices, components, and surfaces in many industries.Read More
Parylene Coatings and COTS ElectronicsRead More
Application of parylene’s xylylene monomer employs a chemical vapor deposition (CVD) process implemented under a vacuum. Unlike wet coating application methods – brushing, dipping, spraying, etc. – parylene CVD is not line-of-sight. Because the vaporous monomer envelopes all sides of the assembly being coated, appropriate process control allows vacuum deposition of an entirely conformal coating, one that penetrates deep into any crevices, rivulets, or sharp edges and points that exist on the assembly’s surface. The resultant parylene film is insulating, ultra-thin, and pinhole-free, exhibiting superior protective barrier qualities and very low moisture permeability.Read More
Parylene Conformal CoatingsRead More
Often considered the ultimate conformal coating, Parylene is well suited to protect many types of products and devices.Read More
In addition to cracking, a range of associated issues may interfere with successful coating of parylene films. Because it is applied via CVD, parylene generates a structurally continuous film covering a PCB or similar assembly. In CVD, the interaction of vapor-phase chemical reactants formulate a non-volatile solid film on a substrate, useful for a variety of applications like corrosion resistance, erosion defense, and high temperature protection.Read More
Parylene is often considered the ultimate conformal coating for the protection of devices, components, and surfaces in the electronics, instrumentation, aerospace, medical, and engineering industries.Read More
One liquid coating type that rivals the use of parylene is silicone conformal coating (Type SR), which cures rapidly, is reliably dielectric and displays exceptional stability across a wide temperature range. These properties make it parylene’s chief performance competitor, for many purposes. Further comparison delineates their benefits and disadvantages relative to each other.Read More
The Workmanship Standards developed by the National Aeronautics and Space Agency (NASA) are essential to assuring reliable performance of the aeronautic, defense and space equipment it uses and monitors.Read More
Designers must keep costs in mind when designing a project.Read More
Parylene C is the most widely used parylene type for conformal coatings. It is classified as a poly-monochoro para-xylene, produced from dimer material, with one chlorine group per repeat unit on its main-chain phenyl ring. As a conformal coating, Type C can be deposited at room temperature via CVD. The resulting film exhibits low chemical, moisture, and vapor permeability, making it particularly useful where protection is needed from corrosive gases. C’s alliance of electrical and physical properties distinguish it uses from those Parylene F, a consequence of their different chemical composition; F has a fluorine atom on its benzene ring, in contrast to C’s chlorine atom.Read More
Basic Thermal Properties of Parylene Conformal Coatings
CVD-generated parylene combines high thermal stability with a low dielectric constant, minimal moisture absorption, and other advantageous properties which sustain its adhesion to substrate surfaces. Among the most beneficial of the parylenes’ thermal properties is their ability to function at an exceptional range of temperatures. Depending on the parylene type, they are operative at temperatures as low as -271º C, and as high as 450º C, representing an ability to perform within a span of 721º C.Read More
The Need for Adhesion Testing
Applied mechanical processes stimulate the binding force between surface molecules required for parylene adhesion to substrates, which is essential to both good parylene performance and assembly/component functionality. The emergence of conditions characterized by non-adherence and delamination squander parylene’s typically exceptional substrate protection against chemical attack, corrosion and moisture, as well as its superior dielectric insulation (er = 3.1).Read More
Characteristics of Noble Metals
Selecting the appropriate pre-treatment procedures is a key factor to this success of parylene adhesion to any substance. Procedures vary quite considerably, according to the materials designated for conformal coating and substrate. Chemically inert surfaces like gold, silver and other noble metals, and nonpolar thermoplastics such as parylene, are extremely difficult to bond; they require additional surface treatments besides cleaning.Read More
Parylene only adheres to substrates mechanically, and this can require assistance from additive substances; parylene’s chemically-based adherence is nonexistent. Adhesion is a consequence of molecular attraction stimulating the surface unification of two dissimilar substances; their joining creates a significant physical bond between them. Of the two primary types of adhesion, chemical adhesion results when a compound joins with another, because they share sufficient mutual chemical interaction to form a bond with each other. Because parylene is chemically inert, chemical adhesion is impossible; it adheres using the other method -- mechanical adhesion. Applied mechanical processes can stimulate this binding force between surface molecules.Read More
A photochemical process used to preserve conformal coatings, adhesives, and inks, UV curing generates a variety of value-added properties in comparison to conventional curing techniques. Applying high-intensity UV light to dry (cure) coatings or other substances, UV curing can provide instant results, increasing production speed while reducing the need for and number of typical set-up and clean-up processes. Lowered operating costs and increased production capacity are further advantages of UV curing for many coating materials and processes.Read More
Poor parylene adhesion negates many of the coating’s most-valued functional properties, including dielectric strength, and resistance to the effects of chemicals, corrosive agents, and moisture. Surface treatments that amplify the interface adhesion between the deposited parylene and the coated substrate are therefore highly desirable. These treatments entail depositing parylene on a clean hydrophobic surface before its chemical vapor deposition (CVD) process is enacted.Read More
LED Lifespan as Effected by UV Light
Although LEDS are designed to provide as many as 100,000 hours of illumination under laboratory conditions, they are not nearly as resilient when subjected to persistent real-world, real-time usage. Sensitive to electrical interference, moisture, UV light, and other persistent sources of physical damage, LEDs require protection to operate at levels anywhere near maximum efficiency. Of all the conformal coatings available to deliver reliable safeguards on an ongoing basis, none surpasses parylene.Read More
Delamination Problems of Parylene Conformal Coatings
Providing a uniform and pinhole-free substrate coating that is ultra-thin, lightweight and durable, parylene coatings completely conform to targeted components and assemblies. Parylene CVD generates a structurally continuous film that, with appropriate pre-treatment, penetrates deep within substrate surfaces, rather than simply attaching themselves to substrates as liquid-application coatings do. These provide effective, dielectrically efficient safeguards with coatings as thin as a fraction of a micrometer. Parylene is chemically and biologically inert and stable, an excellent barrier material to abrasive chemicals, bodily fluids, solvents, liquid water and water vapor.Read More
Once you've decided to use conformal coating for your device, a question that often comes up is:Read More
Conformal Coatings and UV Trace
Conformal coatings provide exceptional protection for printed circuit boards (PCBs) and similar electrical assemblies, through a wide variety of operating circumstances, safeguarding their chemical, electrical, and/or mechanical properties.Read More
Parylene has numerous outdoor applications. However, a major drawback of most parylene types is limited resistance to direct contact with UV radiation. Daylight is the most common source of UV light. Prolonged exposure to its high energy radiation can cause objects extensive surface damage and lead to eventual malfunction of electrical light-generating assemblies within.Read More
Conformal coatings are a protective, non-conductive dielectric layer that are added to a circuit board or electronic device.Read More
Improving Parylene Adhesion
Parylene provides an entirely conformal, durable, pinhole-free substrate coating of extreme utility for an exceptional range of materials, products and purposes. Despite its many advantages, parylene's chemical structure can actually interfere with the reliable interface adhesion required for optimal performance. The chemical vapor deposition (CVD) process that generates so many of parylene's benefits also nullifies chemically-based substrate adhesion; only mechanical adhesion is possible.
Implementing optimal adhesion can require surface modification via application of adhesion promoting agents or methods. The materials and processes used for these purposes are largely dependent on the substrate surface and component's specific operational environments and functions. Although most adhesion promotion methods are used prior to CVD, several can be integrated into the coating-process itself, Among the methods of adhesion promotion used with parylene are:
- Thorough surface-cleaning, which stimulates enhanced adhesion by eliminating accumulated substrate contaminants whose presence can diminish overall coating quality.
- Heat-treating. for three hours at temperatures of 140°C, beneficially activates longer-term adhesion and insulation.
- Active, wired devices profit from bilayer component-encapsulation processes.
While these techniques have their uses for parylene adhesion promotion, the chemical monolayer Silane A-174 (3-Methacryloxypropyltrimethoxysilane - C10H20O5Si) is used most frequently to modify substrate surfaces and improve parylene adhesion.
The Uses of Silane A-174
Silane A-174's value as an adhesion promoting agent stems largely from its versatility. It can be successfully applied to substrate materials like elastomer, glass, metal, paper, plastic or quartz, among a wide range of surface substances. The A-174 silane molecule develops a robust chemical bond with the substrate, facilitating the improved surface adhesion capacity of parylene’s mechanical property. Optimal parylene adhesion is commonly achieved by a treatment with A-174 silane prior to initiating the CVD process. However, regarding appropriate procedural scheduling:
- it is recommended that A-174's application be completed after any necessary masking operations have been finished;
- depending on substrate materials, manual spray, soaking, or vapor phase silane processing techniques may be used to apply A-174.
While the silane promotes adhesion, the parylene assures protection. Thus, appropriately proportional intermixtures of silane A-174 and parylene need to be used, in all cases. Corrosion-resistance can be diminished where the relationship between parylene and silane is inexact, causing part and function deterioration from both beneath- and external to the conformal covering. This is especially the case with medical implants, where reliable component function is mandatory, despite being subjected to persistent exposure to often harsh bodily fluids.Read More
Electronics manufacturers need devices that withstand heat, cold, rain, snow, vibration, fungus, oxidation, and corrosion through decades of operation.Read More
Implantable Medical Devices and the Uses of ParyleneRead More
Defining MEMSRead More
Ruggedized ProductsRead More
Parylene Chemistry and Production RequirementsRead More
Removal of Conformal CoatingsRead 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
Properties of Polytetrafluoroethylene (PTFE)Read More
Protective Conformal CoatingsRead More
While parylene is an extremely effective conformal coating, its benefits only come into play when it is properly applied. When parylene is either applied incorrectly or is deposited on a surface that is not prepared for adhesion, the coating can become compromised. Luckily, common parylene defects can be identified, planned for and mitigated through proper procedures.Read More
Parylene and Conformal CoatingsRead More
Parylene Bio-compatibilityRead More
Parylene DepositionRead More
The Growing Internet of Things
The term Internet of Things ( IoT ) describes the expanding interactive capacities of smart networks of processing systems. Increasingly communicating with each other, they drive enhanced smart automation in many fields, including:
Overall the generic name parylene describes a distinct collection of polycrystalline and linear organic coating materials with innumerable applications. The essential basis of today's parylene N, p-xylene, was inadvertently synthesized at England's University of Manchester in 1947. The filmy residue resulted after high-temperature heating of compounds of toulene and the xylenes polymerized into para-xylene. The substance immediately demonstrated an exceptional capacity for generating the fine but resilient surface-covering that characterizes today's range of parylene conformal coatings.Read More
Recognition of parylene's excellence as a conformal coating for many product uses has grown along with its application. However, issues of barrier failure, current leakage, poor processing, and cost limit its further development and use.Read More
Silicone and Parylene conformal coatings are a lot like humans and dogs. At first glance, we are very different from our canine friends. However, we have a lot in common -- noses, two eyes, hearts, dreams. In fact, we share 84 percent of our DNA with Rover (or Spot). So too with the two coatings. While both have some functional differences -- which we'll explore here -- they also have an important similarity. Parylene and Silicone are both some of the best choices for conformal coatings of your company's products.Read More
Parylene's deposition process is unique among conformal coatings. Unlike others that start as a liquid, get deposited and dry, it starts as a solid. Parylene coating equipment turns it into a vapor, where it then deposits onto the substrate. This unique four-step method poses some challenges but also brings real advantages.Read More
Conformal CoatingsRead More
Masking and Parylene DepositionRead More
If you have a printed circuit board or other item that needs protection, you typically have a choice between potting and conformal coating. While potting offers the largest and most powerful barrier against the outside world, it also carries some significant drawbacks. Conformal coating, especially with parylene, also offers a protective barrier, but does it without the challenges that potting poses.Read More
While Parylene can coat just about anything, one of its most common uses is for protecting printed circuit boards. Product engineers specify Parylene because it offers a unique blend of five capabilities.Read More
Wearables are no longer emerging technology -- they are here. Whether a wearable item is a medical device like an insulin pump, a smart watch or even a finely woven piece of smart fabric, they all have one basic fact in common. All of them contain technologies that need protection from the outside world and, in just about every case; parylene is the most appropriate choice for protection.Read More
Basic Dielectrics and Conformal CoatingsRead More
Light emitting diodes are gradually replacing all other types of lighting. As they move out of consumer electronics and into general purpose applications ,the demands on the technology are shifting. It's relatively easy to keep an LED safe when it is mounted in the front panel of a computer or hidden under a cover on an alarm clock. Protecting it when it is going to be exposed to the elements 24 hours a day, 365 days a year is more challenging.Read More
Parylene can be used outdoors. However, it has one drawback that could limit its suitability in some outdoor applications: sunlight can yellow it. With this in mind, product designers specifying a coating for a product to be used where it will be subject to sunlight should carefully consider the coatings pros and cons before specifying it. Frequently, but not always, it remains the best choice.Read More
Parylene and urethane conformal coatings share many characteristics. Both are physically strong, resistant to chemicals and mitigate tin whisker formation. This doesn't mean that the two compounds are interchangeable, though. While parylene offers a unique blend of capabilities, many projects choose urethane because of its cost, strength and other advantages.Read More
Parylene Surface ProtectionRead More
Implantable devices place a special set of requirements and challenges on their coatings. The moisture and broad mixture of chemicals that are found inside of the body are challenging in and of themselves. However, the body also has needs from the coatings that are placed within it. They need to be non-irritating and inert enough to be harmless. For most applications, the best choice is USP Class VI compliant parylene coatings.Read More
The Need for Rugged ProductsRead More
Parylene and acrylic conformal coatings represent two extremes of the types of compounds you can use to coat printed circuit boards, sensors, or other devices. While acrylic is popular and inexpensive, parylene offers some of the best performance of any coating compound.Read More
Just about every major type of conformal coating provides protection against moisture. If you get a printed circuit board coated with epoxy, acrylic, urethane, silicone or parylene wet, typically all that you have to do is wipe it off. Environments with high humidity pose a different set of challenges. Because moisture is omnipresent in humid environments, the conformal coating doesn't just have to resist water ingress. It also needs to completely seal the coated item. Given this additional requirement, the best choice will usually be either silicone or parylene.Read More
Parylene is the most bio-compatible conformal coating currently available. Its chemical properties make it a natural for use in medical and biological applications. In addition, some of its general benefits also make it particularly valuable in healthcare applications. Finally, parylene also enjoys a stringent USP Class VI bio-compatibility certification.Read More
When it comes to reworking, parylene's strengths are also its biggest drawbacks. In addition to its ability to comprehensively coat substrates, it is also, by design, very challenging to remove. However, "very challenging" and impossible are two different things. Furthermore, good planning strategy before coating can also help to reduce the need for parylene rework.Read More
Parylene conformal coatings have protected medical device components with an extended range of applications for over 40 years. They offer both patients and medical personnel the most reliable level of uniform, biocompatible device-security for cardio- logical and surgical procedures. Their value and application proliferate, as technology develops.
Organic Polymers used as Coatings
The overall generic name parylene designates a unique set of organic polymeric coating materials with innumerable applications. All commercially applied parylene configurations are polycrystalline and linear in nature.Read More
In the course of our business applying parylene to a range of different products, our clients ask many questions. They also have a few consistent misconceptions. Here are the five biggest ones -- and the facts to clear things up.Read More
Parylene has a well-deserved reputation as one of the leading choices for conformal coatings. For many applications, it is the best choice. However, there are some real parylene disadvantages, as well. For many applications, other conformal coatings such as acrylic, epoxy, silicone or urethane offer better performance, lower cost or both.Read More
As engineers continue to seek out the most powerful technologies packed into the smallest footprints possible, the use of microelectromechanical systems (MEMS) are on the rise. At the forefront of progress in miniaturization, MEMS enable small form factors without sacrificing precision and reliability. In many cases, MEMS technologies even offer an increase in performance over their larger, traditional counterparts. MEMS technologies can also be produced at low cost, owing to the use of semiconductor fabrication methods.Read More
Parylene and It's UsesRead More
What is Parylene?
Parylene is a conformal protective polymer used for coating, first postulated by Michael Szwarc in 1947. His early experiments involved the decomposition of the solvent p-xylene. His worked proved that when the vapors of the p-xylene reacted with iodine, para-xylyene di-iodide was the only resulting product. The reaction produced only a low yield and the process was later made more efficient by William F. Gorham.Read More
Regardless of the variant, Parylene in general garners a great deal of praise for the many advantages it offers as a protective conformal coating for applications as varied as medical, aerospace, defense, LEDs, and automotive. Chief among the coating’s benefits, however, is that it can withstand common sterilization techniques, such as electron beam (e-beam), gamma, ethylene oxide (EtO), and autoclave.
Like many chemicals, para-xylylene actually comes in several common variants:
- N. The most basic type of the compound is highly elastic and, as such, is very good at penetrating small areas on components.
- C. The C variant of the chemical replaces one aromatic hydrogen component with a chlorine atom. It is less elastic and is extremely popular in medical applications, in part due to its high degree of moisture resistance.
For contemporary industrial uses, sensors collect and respond to analog information, transforming it to a digital format. Sensor design for many uses has increasingly relied on microelectromechanical systems (MEMS) technology. MEMS are semiconductor-made micro-mechanisms, which typically work by deflecting optical signals from input-to-output fibers by deploying movable micro-mirrors. They demonstrate virtually unlimited potential for an exceptional range of rapidly evolving products for information technology (IT), telecommunications, consumer electronics and automotive engines, among many other purposes.Read More
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'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.
Driving development of such emerging areas as microfluidics, advanced bio-sensing, capsule endoscopy, and personalized medicine, microelectromechanical systems (MEMS) are enabling an array of breakthroughs that promise to enhance patient care and outcomes. Protecting sensitive MEMS products from the harsh conditions both inside the body and out is Parylene conformal coating, which is helping to bring these futuristic technologies to fruition.
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.
Offering sensitivity and performance in a compact package, microelectromechanical systems (MEMS) have become increasingly prevalent in U.S. military applications over the last few decades and are enabling significant technological advances. As with all things military, however, robust protection of these sensitive electronics is imperative in order to ensure that they can withstand the harsh conditions often found on the battlefield. Conformal coatings such as Parylene can help MEMS-based military technologies withstand conditions such as extreme temperatures, humidity, dust/dirt, chemicals, and rugged terrain.
Parylene adhesion can be tricky to manage. Unlike other coatings that adhere to the surfaces they coat, parylene sticks to itself. This can cause trouble when it needs to be applied to smooth surfaces, like areas made of stainless steel or noble metals like gold or silver. However, since parylene has so many other advantages, it's worth looking into methods to improve adhesion. You can use the product; you just might need an extra step.
Tin whiskers have long been a frustrating occurrence for those manufacturing and using electronic devices. First discovered in the 1940s, the whiskering of metal has been the cause of serious problems including the damaging of vital and difficult to replace equipment. Finding ways to prevent or slow the growth of whiskers has been a focus of engineers and scientists for quite some time.
Parylene conformal coatings are used in many different industries. With their hardness, chemical inertness and ability to perfectly coat any surface, they have expanded well beyond their original military and aerospace applications. Whether it's a protective coating for an LED or a protective shell around a coronary artery stent, the compound is found in places where you might not expect to find it.
From front to back, LEDs are improved by conformal coatings. Whether the coating is improving the LED's color accuracy, protecting it from damage or keeping the electronics functioning well, conformal coating of LED electronics extends the suitability of LED technology. Here are the top six ways that conformal coating and LEDs go well together
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'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.
The quality of a conformal coating job is directly related to the cleanliness of the substrate that is being coated. Clean substrates coat well, and contaminated ones don't. The only way to manage the problem is to inspect and clean the board or other item before applying the coating -- once it's coated, it's essentially too late.
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.
It is imperative to obtain proper adhesion of the coating to the substrate in order to truly reap the benefits of parylene conformal coating. Poor parylene adhesion, after all, can negate some of parylene's most-prized properties, including corrosion resistance, chemical resistance, moisture resistance, and dielectric strength. So, it's in an engineer's best interest to understand the importance of parylene adhesion and how to obtain it.
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.
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.
While parylene coating companies are not exactly on every street corner, there are certainly a lot more of them than you think! Below you will find a list of the headquarters for knownNorth American parylene coating companies. If you do not see your company listed and would like it to be, please do not hesitate to email me.
Parylene and acrylic resins are both conformal coatings. Most of the similarities stop there. Because their properties vary so much, they have their own unique uses and capabilities.
People often wonder if their project can be parylene coated. While there are huge list of items that can be coated with parylene, there are some limitations. One of these limitations is size.
Parylene conformal coating is a very robust coating, but sometimes it is not the right fit for a customer’s application for one reason or another. The entire conformal coating process is based on first identifying the standards to be used and customer’s protection desired. It would therefore only make sense that there are alternatives to parylene for different conformal coating demands.
Type xy conformal coating refers to parylene conformal coating. Parylene gets the type xy from its’ full name, para-xylylene. It was shortened to parylene and eventually type xy so that it could be grouped with the other conformal coatings (type ar, ur, etc.).
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.
Diamond SCH Global Conformal Coating Solution Provider exhibiting at Nepcon Shenzhen next week
- Printed circuit boards
- Ferrite Cores
- Metallic Blocks
- Optical lenses
- Implantable devices
- Silicon Wafers
- Motor Assemblies
- Power Supplies
- Photoelectric Cells
- Test tubes
- Fiber Optic Components
- And many more…
Light emitting diodes (LEDs) are a huge and growing even bigger segment of the electronics industry. LEDs are expanding into environments that demand a higher l evel of protection in order for the LED to function properly. One way to get this level of protection is by using conformal coating.
WHAT ARE MEMS?
Microelectromechanical systems (MEMS) is the technology of very small devices; it merges at the nano-scale into nanoelectromechanical systems (NEMS) and nanotechnology. MEMS are made up of components between 1 to 100 micrometres in size (i.e. 0.001 to 0.1 mm), and MEMS devices generally range in size from 20 micrometres (20 millionths of a metre) to a millimetre (i.e. 0.02 to 1.0 mm). They usually consist of a central unit that processes data (the microprocessor) and several components that interact with the outside such as microsensors.
A downfall for wet chemistry, liquid coatings such as silicones, acrylics, epoxy, or urethanes is that they do not meet bio-compatibility requirements and cannot be applied with precise control. On the contrary, parylene does not out-gas and is very effective against the passage of contaminants from both the body to substrate or substrate to body.
Silicone conformal coating is becoming an increasingly popular choice for conformal coating applications. Because of its high temperature capabilities, moisture protection, and ease of application/rework, people are strongly considering silicone coatings for their projects.
One of the different factors to take into account when trying to determine the proper parylene thickness is the amount of clearance needed. If it is a printed circuit board that is an enclosure, there usually will not be too many clearance issues. However, in some cases, even an extra mil of coating can cause extra mechanical abrasion to the parylene which can result in damaged parylene.
Raw Materials – Parylene Dimer and Adhesion Promotion
Parylene dimer is the raw form of parylene. It is the solid inserted into the machine that is broken down through the deposition process. Cost for parylene dimer can be anywhere from $200 to $5,000 per pound depending on the different type of dimer. A typical coating run is around a pound of dimer.
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Parylene Coating Process – Phase 1 – Prior to Parts Arrival
Once we receive a purchase order from a customer, all of the pertinent information such as drawings, specifications, and special instructions are given to the quality department from our marketing team to create custom work instructions for that particular part.
How to Improve Parylene Adhesion
Parylene, through its deposition process, does not adhere chemically, only mechanically, to any given substrate. In order to improve parylene adhesion to its best possible levels for a wide variety of substrates, different methods of surface modification via adhesion promoters must be used. Adhesion promotion methods are typically used prior to the actual coating process, however some can be integrated during the process itself.
The Parylene Deposition Process
Parylene coating is applied through a vapor deposition process onto the substrate or material that is being coated. Depending on the coating type and required thickness, typical parylene deposition rates are about .2/mils per hour, so machine runs can vary from as little as 1 hour to over 24 hours. The process begins with raw dimer in solid state (these are: Parylene C, Parylene N, Parylene D, Parylene AF-4, or other variants) being placed into a loading boat, which is then inserted into the vaporizer. The raw dimer is heated between 100-150º C. At this time, the vapor is pulled, under vacuum into the furnace and heated to very high temperatures which allows for sublimation and the splitting of the molecule into a monomer. The monomer gas continues to be drawn by vacuum one molecule at a time onto the desired substrate at ambient temperatures in the coating chamber. The final stage of the parylene deposition process is the cold trap. The cold trap is cooled to between -90º and -120º C and is responsible for removing all residual parylene materials pulled through the coating chamber.