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Parylene for Flexible Electronics


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• Flexible electronics or flex circuits is a technology used to assemble electronic circuits on flexible plastic substrates as an alternative to rigid, printed circuit boards or PCBs
• Flexible printed circuits (FPCs) are made using photolithography and flexible flat cables (FFC) are laminates of very thin copper strips, sandwiched between two layers of PET
• FPCs are easy to manufacture and standard surface mount (SMT) components can be assembled on the flex substrate
• Single-sided FPCs are perfect for dynamic and high-flex applications
• Flex circuits can be made to conform to a desired shape or flex during use. Everyday electronic devices contain flex circuitry, like the camera in the image below

Published in: Technology

Parylene for Flexible Electronics

  1. 1. Parylene for Flexible Electronics June 2016
  2. 2. © 2016 Diamond-MT. Company website: PRESENTATION OUTLINE • Overview and Introduction • Flexible Electronics Market and Applications • Flexible Electronics Robustness and Reliability • Conformal Coatings for Flexible Electronics • Parylene for Flexible Electronics • Summary • Diamond-MT Company Overview • Diamond-MT Contact Information
  3. 3. Overview and Introduction
  4. 4. Overview and Introduction • Flexible electronics or flex circuits is a technology used to assemble electronic circuits on flexible plastic substrates as an alternative to rigid, printed circuit boards or PCBs • Flexible printed circuits (FPCs) are made using photolithography and flexible flat cables (FFC) are laminates of very thin copper strips, sandwiched between two layers of PET • FPCs are easy to manufacture and standard surface mount (SMT) components can be assembled on the flex substrate • Single-sided FPCs are perfect for dynamic and high-flex applications • Flex circuits can be made to conform to a desired shape or flex during use. Everyday electronic devices contain flex circuitry, like the camera in the image below © 2016 Diamond-MT. Company website: Image from Wikipedia Olympus Stylus camera displaying flex circuitry inside the case
  5. 5. Beyond SMT and Flex Cables • Flexible electronics are more than printed circuit board assemblies and cables. In many ways, flexible electronics is considered the future of the electronic industry, enabling new technologies and applications • A entire industry is emerging for printed and flexible electronics, with the bulk of the market being organic light-emitting diode (OLED) displays, photovoltaic (PV) applications and glucose sensors • Curved and flexible displays are already a billion dollar market while emerging components such as batteries, photovoltaics and sensors are still in R&D • The anticipation is that smart devices, wearables and the Internet-of-Things (IoT) will accelerate the market for flexible electronics of all kinds © 2016 Diamond-MT. Company website: Image from Thinfilm Printed, Flexible Smart Tag for Product Authentication
  6. 6. How Are Flexible Electronics Made? • The electronics industry is dominated by mineral materials like silicon for wafer processed semiconductor chips • Flexible electronics represents a revolution in electronics and semiconductor technology. The use of special “inks” to print circuitry on flexible media on a large scale can be done very cost effectively, almost like printing newspapers • OLED technology based on organic light emitting diodes makes up the largest market share, but this technology is expensive and it has been proven challenging to fabricate large flat-screen TVs with zero defects • Flexible electronics is not a mature industry. Encapsulation is one development area where companies are working to replace rigid glass with better and more stable flexible encapsulation techniques and materials © 2016 Diamond-MT. Company website: Image from CNR News Printed Speakers and Piezoelectric Sensors
  7. 7. Flexible Electronics Market and Applications
  8. 8. Flexible Electronics Market • Flexible electronics is a tale of two stories, PCBs and printed electronics: FLEXIBLE AND SEMI-RIGID PCBs • In 2013, the total global PCB market was $62B. Of this, flexible PCBs were 16% and rigid-flex 5%. Rigid-flex PCBs use polymer layers between rigid cores and is experiencing the highest growth at a rate of 11.3% CAGR • Flexible and semi-rigid PCBs are used for electronic assemblies and cables PRINTED FLEXIBLE ELECTRONICS • The market for printed, flexible and organic electronics is rapidly growing, and expected to increased from $26.54B in 2016 to $69.03B in 2026 • OLED displays make up the largest market share at $16B, followed by OLED light panels at $7B and flexible LCDs at $3B. These three applications make up almost the entire market • All other applications are insignificant now, but there is no lack of buzz and development of flexible electronics covering areas of power, sensors and connectivity for smart devices and the Internet-of-Things (IoT) © 2016 Diamond-MT. Company website: Sources: “Printed circuit boards: A mobile market”, Composites World, October 2014 “Printed, Organic & Flexible Electronics Forecasts, Players & Opportunities 2016-2026”, IDTechEx, 2015
  9. 9. Emerging Flexible Electronics Markets SENSORS • Total flexible sensor market is forecasted to reach $8B by 2025 • Biosensors, force sensors and photodetectors are expected to lead the way for fully printed sensors POWER • Thin, flexible batteries have been available for more than fifteen years, but high cost and low energy storage capacity have limited adoption • Apple, Samsung and LG are now developing flexible battery technology and the market is anticipated to grow from $6.9M in 2015 to $400M in 2025 © 2016 Diamond-MT. Company website: Sources: “Printed and Flexible Sensors 2015-2025: Technologies, Players, Forecasts“, IDTechEx, January 2015 “Flexible batteries enable sensing smart labels” Printed Electronics World, September 2015 0 20 40 60 80 100 120 2014 2015 2016 2017 2018 2019 2020 $USMillion Emerging Printed and Flexible Sensor Technologies
  10. 10. Flexible Electronics Applications (1/2) • Flexible circuits are used in applications that are space constrained and require physical flexibility that can not be met by rigid, lower cost PCBs • A very common application is the switch matrix in an electronic keyboard • OLED technology is used for flat, curved and flexible displays © 2016 Diamond-MT. Company website: Images from Wikipedia, LG, and
  11. 11. Flexible Electronics Applications (2/2) • Most flex circuits are passive and used to connect electronic components such as capacitors, resistors, inductors, ICs and sensors • Flexible electronics enable new and innovative products that are driven by user experience and realized by industrial design. Here are a few examples: © 2016 Diamond-MT. Company website: Images from iApple, Fixit, Chipworks, and Flexible PCB Flex Cable Nike’s Fuelband iPhone Home Button Apple Pencil
  12. 12. Flexible Electronics Robustness and Reliability
  13. 13. Reliability for Flex and Semi-Rigids • Flex and semi-rigid circuits have similar reliability challenges compared to standard, rigid PCBs • There are four broad categories for PCB reliability: • Electrical Reliability: requires clean power and low-impedance grounding. Traces must be laid out to prevent crosstalk and clock skew while being protected from environmental contamination • Mechanical Reliability: although flexible, flex circuits have mechanical limitations and excessive stress can cause damage to solder joints and traces • Thermal Reliability: flex substrates are affected by thermally accelerated failure mechanisms, such as electromigration. Since flex have less mass than rigid PCBs, they have limited heat sink capabilities • Thermochemical Reliability: is mechanical stress caused by temperature cycling that can result in cracked traces and solder balls collapsing. Flexible electronics are less prone to this since compliant substrates reduce mechanical stress effects compared to rigid PCBs © 2016 Diamond-MT. Company website: Images from Electroiq, Horizon Magazine, and Google
  14. 14. Reliability for Printed Electronics • Printed flexible electronics can bend and stretch, which is made possible by a “silicon island” approach or a buckling mechanism • Silicon Island; circuits are separated into small islands on a flexible material. The islands are rigid, but the surrounding material flexes • Buckling Mechanism; thin strips of metal or other conductive material are bonded to a flexible substrate. When the substrate flexes, the metal traces buckle and stretch, but do not break • In the future, flexible electronics is expected to be as robust and have similar density to silicon based electronics. Stanford University is developing a carbon nano tube (CNT) structure for the next generation flexible electronics © 2016 Diamond-MT. Company website: Flexible Circuit using Nanotubes from Stanford University Images from Economist, EE Times and EIT Digital Source: “Carbon Nanotube Circuits Are Back in the Running as a Viable Material for Flexible Electronics”, IEEE Spectrum, March 2014 • Flexible electronics are light weight, flexible, durable, shock resistant, shatter proof low- cost • Printed flexible electronics is mostly in R&D and reliability research is mostly academic. Each technology and device will have its own set of reliability issues, but they all need to be protected from the environment
  15. 15. Encapsulation and Exposure • A major challenge with organic materials for flexible electronics is stability, which limits the lifespan of products • One example is the photovoltaic solar cell that is constantly exposed to the elements. Direct exposure to the sun and heat will alter and degrade organic materials over time • Encapsulation and new material structures are needed to protect devices from exposure and to increase the reliability and lifetime • Devices like environmental sensors will require some exposure to the outside world to perform its sensing function. Partial encapsulation techniques combined with, for example, conformal coating will likely be needed for many of these types of applications © 2016 Diamond-MT. Company website: Image from CNR News
  16. 16. Conformal Coatings for Flexible Electronics
  17. 17. What is Conformal Coating? • Conformal coating is a thin layer of protective coating to protect electronics from moisture and harsh environments • Conformal coatings are not designed to be total sealants, but a “breathable” protective layer that shields against the elements while allowing moisture trapped in the circuit board to escape ADVANTAGES OF CONFORMAL COATING • Protects against environmental hazards including: moisture, chemicals and other corrosive materials • Is very flexible and compliant, which is very desirable for flexible circuits and electronics • Has insulating properties and allow up to 80% reduction in conductor spacing for electronic circuitry • Is very thin (25-75µm) and light weight so it adds very little mass • Conforms to any surface and even the smallest features for full protection • Several different types of conformal coatings allow the selection of the best material for a given application © 2016 Diamond-MT. Company website:
  18. 18. Conformal Coatings for Flex Circuits • Conformal coating for flex circuit assemblies is applied to protect from moisture, dust, chemicals and other contaminants that could compromise the reliability of the circuit • Increased complexity of flexible electronic circuits often requires selective conformal coating. This can be achieved by a programmable robotic coating station (i.e. spray coating) or by masking the areas where conformal coating is not needed for brush, dip, spray and CVD applications • There are five main types of conformal coatings, each with their own set of characteristics: acrylic, epoxy, polyurethane, silicone and parylene • Parylene is considered the best overall solution for applications ranging from PCBs to medical implants, but is tough to remove and rework © 2016 Diamond-MT. Company website: Images from Nexus3c and Diamond-MT Robotic Spray Coating System Parylene CVD System
  19. 19. How is Conformal Coating Applied? BRUSHING • Manual application of conformal coating using a brush • Cosmetically inferior and subject to defects such as pin-holes and bubbles • Low volume applications only SPRAYING / DISPENSING • Manual use of aerosols or automated spray and dispense systems • Very effective method for low to medium volume applications • Coating quality can be system or operator dependent DIPPING • Highly repeatable conformal coating process for PCBs • Coating gets everywhere so masking is needed to preserve keep-off areas • Low-cost and easily scalable for high volume applications VAPOR DEPOSITION • Conformal coating using chemical vapor deposition (CVD) • Tiny coating particles adhere to every surface and penetrate every crevice • More complex than dipping, but suitable for high volumes • Parylene is deposited using CVD © 2016 Diamond-MT. Company website:
  20. 20. Types of Conformal Coating © 2016 Diamond-MT. Company website: Type Material Cost Application Strengths Weaknesses Parylene* (Type XY) High CVD in vacuum Excellent thickness uniformity Chemically inert, solvent resistant Light weight and low outgassing Stress free Very high dielectric strength Cost of material Difficult to remove Poor adhesion to noble metals Acrylic Resin (Type AR) Low Brush, spray, dispense Easy to rework and repair Simple drying process Low permeability to moisture Good adhesion Easy to control viscosity Low operating temperature Sensitive to solvents High VOC content Flammable Not very robust Epoxy (Type ER) Medium Brush, spray, dispense Up to 150ºC Abrasion resistant Low stress over temperature Low permeability to moisture High dielectric dielectric strength Difficult to rework High-stress film Too thick film can result in shrinkage during curing Polyurethanes (Type UR) Medium Brush, spray, dispense God dielectric properties Solvent, acid and base resistant High resistance to abrasion Low permeability to moisture Easier to rework than epoxy Cures slowly High tolerance to solvents Sensitive to mechanical vibration Silicone (Type SR) High Brush, spray, dispense, dip Wide operating temperature Flexible, impact protection High dielectric strength Low surface energy for wetting Poor wear and abrasion resistance Lower resistance Uneven film thickness * Parylene offers the best overall protection of all the conformal coating types
  21. 21. Parylene for Flexible Electronics
  22. 22. Parylene for Flexible Electronics • Parylene was developed over 30 years ago, primarily to provide a protective dielectric layer for PCBs • Parylene is a generic name for a group of polymer-based materials (poly- para-xylylenes) that are commonly used as moisture and dielectric barriers • Parylene is perfect for flexible and semi-rigid circuits since it is light weight, can be applied in very thin layer and is flexible so it does not crack during use • Flexible electronics enable the integration of conformable systems that can be seamlessly integrated into new applications at a low cost © 2016 Diamond-MT. Company website: Image from and Technical University, Eindhoven Stretchable Electronics Semi-Rigid PCB w/ flex cable
  23. 23. Flexible Electronics | Flex Circuits • Electronic device designers across all industries are moving away from the standard multilayer FR4 printed circuit boards to use more flex materials for interconnects, especially in physically constrained applications • Flex assemblies have been historically challenging for protective conformal coatings and often required a protective case or shield. A major reason has been the lack of ability to selectively conformal coat devices in large volumes • Robotic spray systems can be programmed to selectively conformal coat devices, without the need to physically cover areas where conformal coating is undesired • Parylene provides a pin-hole free conformal coating with negligible surface tension to provide superior protection to densely populated substrates and the most intricately designed flex circuits © 2016 Diamond-MT. Company website: Images from and Examples of Flex Circuits
  24. 24. Flexible Electronics | Displays • Organic light-emitting diode (OLED) technology is used to create digital displays for televisions, computers monitors, smart handheld devices and game consoles • OLED displays work without a backlight and can therefore display deep black levels and be thinner than liquid crystal displays (LCDs) • An OLED pixel consist of an organic carbon-based film placed between two conductors. When current passes through the conductors, the film emits light • Water can instantly damage the organic materials of OLED displays and reliable sealing processes are needed for manufacturing. In addition, parylene conformal coating can protect against moisture that otherwise could compromise the reliability of flexible displays © 2016 Diamond-MT. Company website: Images from Wikipedia, Ubergizmo and Gadgets 360 WearablesFlexible OLED Device Television
  25. 25. Flexible Electronics | Batteries • Wearables is a major growth area for flexible batteries where traditional batteries do not meet requirements for flexibility, form factor and light weight • Thin-film battery technologies are still in development as the current versions struggle to delver on energy density to compete with regular batteries • Both single-use and rechargeable versions are being developed, including reusable zinc and lithium thin-film batteries • Flexible batteries have had some limited commercial success in medical skin patches • The battery itself is fully encapsulated, but exposed contacts provide a physical area that is exposed to the environment. Conformal coating can be used to protect the interface between batteries and the application it is powering © 2016 Diamond-MT. Company website: Image from Beauty Packaging
  26. 26. Flexible Electronics | Sensors • Printed electronics can be used to create disposable and more permanent sensors in ultra high-volumes • Printed electronics sensors can be used in a broad range of medical, biomedical and consumer applications like biometric sensors and asset tracking labels • Smart labels are being developed with sensory functions, memory, logic and connectivity (e.g. NFC) and be used for tracking quality data for pharmaceuticals and perishable foods • Many sensors require a sensing interface or window to the outside world, which could be vulnerable to moisture and other contamination. Conformal coating could provide the necessary protection for sensitive sensing interfaces © 2016 Diamond-MT. Company website: Images from Electronicspecifier and +Plastic Electronics Smart Sensor Tags Biometrics
  27. 27. Flexible Electronics | PV • Printed photovoltaic (PV) cells offer a convenient and cost-effective power solution over disposable batteries • These PV cells are designed to harvest energy in a wide range of light conditions indoors and outdoors, from florescent light to direct sunlight • Single cell PV modules are developed for “peel and stick” applications where multiple cells can be connected in series or parallel to charge a supercap or a re-chargeable battery • Three main interests for PV cells include sensor applications for the IoT where hard-wiring is too expensive or not practical, motorized window shades and retail displays • Similar to flexible batteries, PV cells include exposed metal contacts that interface with the rest of the system. These contacts can be protected by conformal coating once they have been permanently mounted in place © 2016 Diamond-MT. Company website: Image from Printed Electronics Now
  28. 28. Flexible Electronics | Medical (1/2) • Flexible electronics allows the development of circuitry that can conform to the shapes of a human body in ways rigid PCBs can not • Flexible circuits can already be found in a range of medical applications: • Implants – pacemakers, defibrillators and cochlear ear implants • Non Implantable – hearing aid and drug dispensing systems • Monitoring - wearables for monitoring blood-pressure • Diagnostics – equipment for ultrasound scanning, MRI and CT • Surgery Tools – electronic saws, scissors and screw drivers • Disposables – ultrasonic scalpel and biopsy instruments © 2016 Diamond-MT. Company website: Cochlear Implant• Parylene is unaffected by moisture (water, blood or perspiration), chemicals, solvents and gases, and resistant against bacteria, fungus and corrosion • Parylene does not out-gas and is very effective against transferring contaminants from the body to a substrate and vice versa Image from implantable Medical Devices
  29. 29. Flexible Electronics | Medical (2/2) • Parylene is the conformal coating of choice for the medical and biomedical industry due to its material properties and since it is approved for medical use • Parylene is bio compatible, chemically inert and conforms to material ISO- 10993 Biological Evaluations for Medical Applications • Parylene is FDA approved based on testing performed under USP Class VI bio-compatibility rating; safe for use within and outside the body • Being transparent, flexible and deposited in very thin layers (down to 0.1mil), parylene is highly suitable for even the most complex surfaces in medical applications. © 2016 Diamond-MT. Company website: Images from NY Times, Catchnews and The Independent “Smart” Skin UV Sensor Patch “Heart Glove”
  30. 30. Flexible Electronics | Military (1/2) • NASA has engaged with multiple tech companies in the Silicon Valley, including Apple to develop flexible electronics for military applications • A total of 96 companies and 11 laboratories, along with state and local governments are investing in and innovating flexible hybrid circuits for wearable computers that would wrap around a soldier’s arm • Flexible electronics could enable other military applications, including lighter and more robust robots as well as stealth electronics in aircrafts. These applications will require robust and highly reliable circuits, and conformal coating can offer environmental protection for very harsh environments © 2016 Diamond-MT. Company website: Image from and Source: “Electronics That Bend: The Pentagon, Apple And NASA Jointly Developing ‘Flexible Electronics’”, Design&Ternd, August 2015 “Wrap able” Touchscreen Future Soldiers will have Flexible Electronics Everywhere
  31. 31. Flexible Electronics | Military (2/2) • Flexible electronics is a key technology enabler for the future soldier: • Body Armor – sensor networks and IR visor • Connectivity – RFID tags and flexible displays • Health Monitoring –pulse, temperature and blood sugar levels • Power – energy harvesting to charge onboard batteries • Regardless of form factor and application, conformal coating can provide effective protection for even the most extreme conditions like a battlefield © 2016 Diamond-MT. Company website: Image from Venturebeat
  32. 32. SUMMARY
  33. 33. SUMMARY • Flexible electronics include flex circuit assemblies and printed flexible electronics, all of which can benefit from conformal coating • Parylene offers the best coverage for flex circuits since it can adhere to the smallest features and penetrate the smallest crevices for complete coverage • Parylene provides the best overall protection of all the conformal coatings PARYLENE OFFERS THE FOLLOWING ADVANTAGES • High reliability • Pin-hole free coating • Light weight • Outstanding moisture protection • High tensile strength • Thermal stability • Stress free • Chemical and solvent resistance • Dry lubricant film • High dielectric strength • Good adhesive properties • Biocompatible and biostable • Particle immobilization • Optically transparent © 2016 Diamond-MT. Company website:
  34. 34. Diamond-MT Company Overview
  35. 35. • Founded in 2001 • HQ in Johnstown, PA • Global partners in Shenzhen (China) and Manchester (UK) • Specializes in conformal coatings for electronics and sensors • Provides complete range of conformal coating services • Manufactures and sells automated equipment • Consults on advanced coating projects ABOUT Diamond-MT © 2016 Diamond-MT. Company website:
  36. 36. Diamond-MT Contact Information
  37. 37. CONTACT INFORMATION Diamond-MT 213 Chestnut Street Johnstown, PA 15906 Email Phone 814.535.3505 Fax 814.535.2080 Website © 2016 Diamond-MT. Company website: