Parylene for Industrial MEMS

In modern industrial applications, sensors play a crucial role in collecting and converting analog data into digital form. The design of sensors for various purposes has become increasingly reliant on microelectromechanical systems (MEMS) technology. MEMS consist of tiny mechanical devices made from semiconductors, often operating by reflecting optical signals between input and output fibers using movable micro-mirrors. They hold immense potential for a wide array of rapidly advancing products in information technology (IT), telecommunications, consumer electronics, automotive engines and various other markets.

Parylene Conformal Coatings for Industrial MEMS

To be effective, MEMS applications often need to be situated in areas of high activity and stress. They require protection from prevailing environmental conditions like exposure to heat, cold, liquids or similar circumstances that can lead to product degradation or malfunction. Among available coating options, none match the reliability of Parylene.

Parylene conformal coatings provide superior chemical, dielectric, moisture, and thermal protection that exceeds industry standards. This exceptional level of protection is delivered through ultra-thin product coverage, catering to:

• Precise, targeted utilization for particular industrial/commercial products
• Implementation of specialized industrial processes
• Challenging conditions that could otherwise lead to reduced performance or product failure

Industrial Uses of Parylene Conformal Coatings for MEMS

Automotive Applications – MEMS automotive sensors integrate signal processing and communication functions for electronic vehicle (EV) systems like powertrain/chassis control, battery management systems, power inverters, primary electronic control units (ECU) and passenger comfort/convenience. Additionally, MEMS technology finds application in other automotive areas, such as manifold air pressure (MAP) and manifold air temperature (MAT) sensors. Parylene coatings:

• Safeguard micro-machined circuits from harsh automotive conditions, which may include mixtures of brake and transmission fluid, ethylene glycol, engine humidity, exhaust gases, freon, fuel, oil, and other substances
• Maintain sensors’ functionality through changes in engine conditions
• Help to sustain their robust performance

An array of advanced smart sensors, including angular rate sensors, accelerometers for airbag deployment, and communication devices linking vehicles to the outside world, represent examples of MEMS technology that are anticipated to become standard for automotive operations in the near future.

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 it is applied in a gaseous state under vacuum conditions, Parylene generates a uniform, impermeable coating of the gyroscope’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 gyroscope’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 and electrical properties
• 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, bandwidth capabilities and performance are measurably enhanced. Among the variants, Parylene C stands out as the most optimal choice for these purposes due to its:

• Good mechanical properties
• Ability to be etched
• Inertness with respect to micro-machining’s other reagenting agents
• Superior adhesion characteristics
• 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 smart phones, hearables and wearables applications. Differentiated sensor / component Parylene packaging requirements are developed according to each particular MEMS application.

Parylene demonstrates versatility across various applications, although tailored processes and treatments are necessary to ensure proper conformal coating of specific MEMS devices. The ongoing advancement in MEMS and Parylene technologies is driving a mutually beneficial evolution, paving the way for a broader array of industrial and consumer products in the foreseeable future.