Parylene for Industrial MEMS
Posted by Sean Horn
Thursday, October 2, 2014 1:42
@ 1:42 PM
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.
Parylene Conformal Coatings for Industrial MEMS
To be effective, these MEMS applications often need to be situated in areas of high activity and stress. They require protection from prevailing environmental conditions brought about by exposure to heat, cold, liquids or similar circumstances that can lead to product degradation or malfunction. No current available coating substance for these products is as reliable as parylene.
Parylene conformal coatings offer chemical, dielectric, moisture, and thermal protection that surpasses industry-standards. This high degree of protection is provided with ultra-thin product coverage, a quality that supports a combination of:
- refined, highly-focused usage for specific industrial / commercial products, and
- applications of specialized industrial procedures,
- frequently under conditions of duress that might otherwise engender diminished performance or product failure.
Industrial Uses of Parylene Conformal Coatings for MEMS
Automotive Applications – MEMS automotive sensors join signal processing and communication functions for such electronic vehicular systems as power train / chassis control and passenger comfort / convenience. Other automotive applications of MEMS technology include manifold air pressure (MAP) and manifold air temperature (MAT) sensors. Parylene coatings:
- protect micro-machined circuits from aggressive automotive environments
- that contain mixtures of brake / transmission fluid, ethylene glycol, engine humidity, exhaust gases, freon, fuel, oil, or other substances,
- maintaining sensors’ functionality through changes in engine conditions,
- helping to sustain their robust performance.
More is expected in the future, as developmental / manufacturing issues resolve. A wider range of smart sensors, angular rate sensors, accelerometers for airbag deployment, and communications’ devices that connect the vehicle to the outside world, are examples of MEMS technology soon expected to become commonplace for automotive functions.
MEMS Gyroscopes – MEMS gyroscopes have been used for industrial and consumer applications to address motion processing and inertial sensing issues. Parylene structures have been fabricated for complete integration with MEMS gyroscopes. Because its applied in a gaseous state under vacuum conditions, parylene generates a uniform, impermeable coating of the gyro’s often irregular surfaces. This is important because MEMS sensors in the gyroscope must be suitably protected if they are expected to function appropriately. Motion deflections exhibited by each of its vibrating members must be accurately detected on the device’s sensor frame to assure its functional efficiency. Parylene surfaces are also resistant to mechanical and thermal pressures that commonly develop during the gyro’s operation.
Optical Switching Technology (OST) – Essentially light-switching between optical fibers, optical switching relies on MEMS to replace electronic signaling for data networking. Micro-mirrors use light as the vehicle for data transmission, with all-optical switches eliminating bottlenecks and increasing Internet speed. Parylene conformal coatings improve the ruggedization of OST, providing added durability to installed equipment and enhanced performance, by generating:
- resistance to moisture, dirt and other contaminants,
- high dielectric strength,
- improved polymer stability,
- favorable physical / electrical properties, and
- minimized power consumption / cross-talk.
MEMS Portable Electret Microphones – Such electronic consumer products as Bluetooth headsets, digital still / video cameras, notebook PCs, security / surveillance systems, smartphones, tablets, and teleconferencing systems use MEMS portable microphones. As in other industrial applications, parylene’s electrical, thermal, surface, and mechanical properties offer superior protection, without limiting product functionality. Parylene conformal coatings provide structural reinforcement to the microphone’s back plate membrane, which improves both its rigor and yield-return. Thus reinforced, the back plate’s open sensitivity and bandwidth capabilities and performance are measurably enhanced. Of the parylenes, Parylene C is most suitable for these purposes, because of its:
- good mechanical properties,
- ability to be etched,
- inertness with respect to micro-machining’s other reagenting agents, and
- superior adhesion characteristics, featuring
- uniform layers adhering to desired thickness.
Further Applications of Industrial MEMS and Parylene Coatings
For many industrial purposes, parylene provides an effective combination of adhesion, electrical conductivity, high strength, flexibility and durability in comparison to other conformal coatings.
Other MEMS devices benefiting from parylene coatings include inkjet printers, and such consumer electronics uses as accelerometers for cell phones / digital cameras and interferometric modulator display (IMOD) applications. Differentiated sensor / component parylene packaging requirements are developed according to each particular MEMS application.
Parylene is adaptable to most uses, even if specialized processes and treatments must be devised to assure appropriate conformal coating of the particular MEMS device. Ongoing developments in both MEMS and parylene technologies are establishing a mutually beneficial evolution, that will engender a wider range and distribution of industrial and consumer products in the near future.