Evaluating Thermal Stress Transfer in Silicon MEMS Accelerometer Assemblies
Thermal stress evaluation isolates CTE mismatch across silicon and packaging materials to prevent accelerometer zero-g offset drift and sensitivity shifts.
Resonant Accelerometer
Frequency Transducer
Vibrating beam instruments occupy the primary sensing stage in high precision inertial navigation systems. A resonant accelerometer operates by detecting the shift in the natural frequency of a micro-machined beam as it undergoes tension or compression.
Structural Tension
Acceleration forces act on a proof mass that is suspended by thin mechanical resonators. When the mass moves, it applies a longitudinal load to the vibrating beams, causing their resonant frequency to increase or decrease.
Digital Stability
Output from the device is a frequency signal that can be counted directly by digital electronics. This characteristic makes the resonant accelerometer less sensitive to the voltage noise and gain errors that plague analog sensors.
Error Source
Temperature fluctuations remain the primary driver of measurement drift in these instruments. Changes in the Young’s modulus of the silicon or the quartz beam alter the stiffness and the baseline frequency of the sensor. High grade units include an integrated temperature sensor to apply real time corrections to the frequency data.
Vacuum packaging is also required to maintain a high quality factor and prevent air damping from suppressing the resonance. Regular calibration against a known gravity reference ensures that the scale factor remains accurate over the life of the instrument.