Micro-Electro-Mechanical Systems (MEMS) have become an important enabling technology across aerospace and defence applications. Their ability to combine microscopic mechanical structures with electronic sensing in compact packages makes MEMS devices particularly valuable where size, weight, power consumption and measurement capability are important considerations.
Applications range from accelerometers and gyroscopes to pressure sensors and complete inertial measurement units (IMUs). These devices can contribute to aircraft control, navigation, platform stabilisation, condition monitoring and other sensing systems.
However, aerospace and defence environments can place significant demands on miniature sensors. Vibration, mechanical shock and temperature changes can affect MEMS structures and their associated packaging. NASA guidance for space applications consequently considers material properties, processing, device structures, packaging, failure mechanisms and qualification as interconnected aspects of MEMS reliability. (NASA Technical Reports Server)
For engineers developing specialist sensors, MEMS manufacturing is therefore about much more than producing microscopic structures. Wafer processing, thin-film deposition, precision dicing, die bonding, wire bonding and micro assembly can all contribute to the performance and long-term reliability of the finished device.
MEMS Accelerometers in Aerospace and Defence
MEMS accelerometers measure linear acceleration. At their core are microscopic mechanical structures that respond to movement, with this displacement converted into an electrical signal.
Their compact dimensions make MEMS accelerometers suitable for applications including motion sensing, navigation, platform monitoring and vibration measurement.
The operating environment is particularly important. Research into MEMS accelerometers for aerospace applications has identified reliability considerations including cyclic fatigue, packaging-induced mechanical stresses and contamination within packages. Mechanical shock and thermal cycling are also significant environmental considerations. (NASA Technical Reports Server)
These requirements place considerable importance on manufacturing repeatability. Small variations in material properties, component geometry, bonding or assembly can potentially influence how a sensor behaves when exposed to repeated environmental stresses.
MEMS Gyroscopes
Where accelerometers detect linear acceleration, gyroscopes measure rotational movement or angular rate.
MEMS gyroscopes can use microscopic vibrating structures whose motion changes in response to rotation. They can be integrated alongside accelerometers and other sensors to create sophisticated motion-sensing systems.
Aerospace applications can expose these devices to particularly challenging conditions. Research into MEMS vibrating gyroscopes highlights potential reliability issues associated with microfabrication process stability, elevated temperatures and external vibration. (MDPI)
Precise manufacturing becomes essential because characteristics including critical dimensions, material properties and structural stiffness can affect sensor behaviour.
MEMS Pressure Sensors
Pressure measurement is another important application for MEMS technology.
MEMS pressure sensors commonly incorporate microscopic diaphragms that deform in response to pressure differences. Depending on the sensor design, that deformation can be measured using technologies such as piezoresistive or capacitive sensing.
Aerospace applications can include atmospheric and altitude-related measurements, airflow monitoring and other pressure-monitoring functions.
Producing these structures consistently can require tight control over wafer thickness, surface condition, thin films and component dimensions. Precision wafer processing and dicing are therefore important stages when converting processed wafers into individual sensor dies.
Combining Sensors into an IMU
The capabilities of individual MEMS sensors become particularly powerful when several devices are combined into an inertial measurement unit (IMU).
A typical MEMS IMU combines accelerometers and gyroscopes, potentially alongside other sensors, to provide measurements of acceleration and rotational movement. NASA describes IMUs as key navigation instruments on many autonomous and semi-autonomous platforms, with MEMS accelerometers and gyroscopes providing acceleration and rate information respectively. (NASA Technical Reports Server)
Sensor outputs can then contribute to navigation, attitude determination, stabilisation and control systems.
Integration introduces additional manufacturing considerations. Research into MEMS IMUs notes that the reliability of individual sensors does not automatically guarantee the reliability of the complete unit: multiple sensors, electrical interfaces, connections and additional electronics create a more complex system. (MDPI)
Die attachment, electrical interconnection, packaging and micro assembly therefore become important parts of the overall manufacturing process.
MEMS Sensors and Navigation Systems
Traditional high-performance inertial navigation equipment can be relatively large and complex. MEMS technology provides opportunities to create significantly smaller sensing packages suitable for systems where available space and weight are limited.
Accelerometers can provide information about linear acceleration, while gyroscopes measure angular movement. Combining their measurements allows an IMU to provide information that can be used by a wider navigation or control system.
The challenge is maintaining dependable measurement performance under realistic operating conditions.
For aerospace and defence engineers, this makes manufacturing quality inseparable from sensor performance. A device may perform correctly under laboratory conditions but must also remain stable when subjected to the environmental stresses associated with its intended application.
Why Vibration Matters in MEMS Manufacturing
Aircraft, spacecraft and defence platforms can expose components to sustained and highly variable vibration.
Because many MEMS devices contain moving microscopic structures, vibration can influence sensor output and potentially contribute to mechanical fatigue or structural failure. Research specifically examining MEMS IMUs in vibrating environments has consequently assessed both individual sensing performance and complete-system reliability. (MDPI)
Manufacturing processes must therefore achieve repeatable structures and robust interconnections.
Controlled die bonding and wire bonding can be particularly important when creating assemblies expected to withstand vibration. Bond integrity, alignment and process consistency need to be considered alongside the MEMS structure itself.
Thermal Cycling and Dimensional Stability
Temperature presents another challenge.
Aerospace equipment can experience substantial temperature changes during manufacture, storage, operation or deployment. Different materials expand and contract at different rates, potentially creating mechanical stresses within dies, thin-film structures, bonds and packages.
NASA describes thermal cycling as a method of exposing electronics to temperature extremes and controlled changes between them to verify performance and help identify material or workmanship defects. (Small Spacecraft Institute)
At microscale dimensions, manufacturing tolerances and material interfaces become especially significant.
Thin-film deposition processes need good control over layer composition and thickness, while bonding and assembly processes must create mechanically stable interfaces appropriate for the intended device.
Mechanical Shock and MEMS Reliability
Some aerospace and defence applications also expose electronics to sudden mechanical shock.
Despite their small size, MEMS structures are not immune to these forces. Research into MEMS reliability under shock conditions identifies potential failure mechanisms including fracture and adhesion of microscopic structures, particularly under severe shock loading. (MDPI)
The ability of the completed assembly to withstand shock depends on multiple factors, including device architecture, materials, packaging and manufacturing quality.
Precision processing helps reduce avoidable variability so that devices can subsequently be tested and qualified against appropriate application requirements.
Manufacturing for Long-Term Reliability
Aerospace and defence components may be required to operate reliably for extended periods, sometimes where maintenance or replacement is extremely difficult.
Long-term MEMS reliability therefore needs to be considered throughout design, manufacturing, packaging and qualification rather than assessed only at final inspection.
Environmental verification programmes for MEMS intended for demanding applications can include acceleration, random and sinusoidal vibration, acoustic testing, pyroshock, thermal cycling and thermal-vacuum testing. Package integrity and, where appropriate, radiation performance may also need consideration. (NASA Technical Reports Server)
Accelerated life testing can additionally expose aerospace components to elevated temperature, rapid thermal cycling or vibration to reveal manufacturing or design weaknesses within a shorter timeframe. (Small Spacecraft Institute)
Precision MEMS Manufacturing at ICT
Developing aerospace and defence MEMS devices often requires access to several complementary micro-manufacturing capabilities.
ICT has more than 30 years’ experience in precision engineering and provides specialist manufacturing support for organisations requiring prototype, development and low-volume production capabilities.
ICT’s in-house capabilities include wafer thinning, wafer dicing, precision lapping and polishing, thin-film deposition, die bonding, wire bonding and micro assembly.
Bringing these processes together can be particularly valuable during MEMS development. Instead of treating wafer preparation, component separation, bonding and assembly as unrelated operations, manufacturing requirements can be considered across the complete device.
For universities, research organisations, aerospace and defence companies and technology start-ups, this also provides a route for developing prototypes and specialist components without necessarily committing immediately to high-volume semiconductor production.
Why Precision Matters at the Microscale
MEMS devices demonstrate how apparently small manufacturing variations can become important at microscopic dimensions.
Surface condition, wafer thickness, deposited layers, dicing quality, die positioning, bond integrity and assembly accuracy can all contribute to the characteristics of the finished component.
When that component must subsequently withstand vibration, shock, thermal cycling and extended service, process control becomes even more important.
Effective MEMS manufacturing therefore combines precision engineering with controlled processing, inspection and an understanding of the demands placed on the finished device.
For aerospace and defence applications, where sensing systems can operate in demanding environments, precision manufacturing provides an essential foundation for producing MEMS components capable of progressing from prototype development towards application-specific testing and qualification.
