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.
Zero-G Offset Shift
Null Deviation
Residual voltage deviation identifies the error present in a transducer output when no external acceleration acts upon the device. A zero-g offset shift measures the variance of this quiescent signal from its calibrated null position.
Package Stress
Mechanical forces from the housing or the solder joints often press against the sensing element. This pressure causes a zero-g offset shift by distorting the internal structure of the transducer even when the sensor is at rest.
Temperature Cycling
Environmental exposure often accelerates the relaxation of internal stresses. As the device undergoes heating and cooling, the materials in the package expand and contract, leading to a permanent zero-g offset shift if the materials do not return to their original state. This effect is particularly pronounced in surface mount components where the circuit board can apply significant torque to the package.
Stability Verification
Qualification of high precision sensors involves monitoring the baseline signal over several months. A stable zero-g offset shift indicates that the internal stresses have reached equilibrium and the device will maintain its accuracy in the field. Metrologists use multi axis tumble tests to separate the static offset from the sensitivity of the instrument.
Final calibration coefficients are stored in the sensor memory to subtract this residual error from the live data stream.