Thermo-Mechanical Stress

Material Mismatch

Differences in the coefficient of thermal expansion between the sensor and its package are the primary cause. When the temperature changes, thermo-mechanical stress exerts a force on the proof mass or the resonator. This force is often indistinguishable from the signal the sensor is meant to measure.

Long Term Impact

Repeated cycling of these stresses can lead to hysteresis or permanent shifts in the sensor’s zero-point. In extreme cases, thermo-mechanical stress may even cause cracks in the silicon or delamination of the die-attach material. Designers use compliant adhesives or stress-relief mounting to isolate the sensing element.

These techniques absorb the expansion without passing the force to the sensor. High-precision devices often use a specialized package that matches the thermal properties of the internal die. This ensures the output remains stable even after many years of environmental exposure.

Performance Stability

Characterizing this stress is a major part of the qualification process for automotive and industrial sensors. Reducing thermo-mechanical stress is necessary to achieve the highest levels of measurement repeatability.