Deformation Mechanism
Time-dependent plastic deformation occurring under constant mechanical stress at elevated temperatures determines the long-term structural integrity of high-reliability sensor packages. This mechanical process of high temperature dwell creep accumulates localized strain during hold times in thermal cycles. The rate of this deformation depends on the operating temperature relative to the melting point of the material.
Test Procedure
Qualification of sensor substrates involves holding the assembly at its maximum rated temperature for several hundred hours under load. Test systems monitor the extension of the specimen over the entire hold duration to detect early stage changes. This protocol measures the susceptibility to high temperature dwell creep in the metallic and ceramic interconnects.
Structural Degradation
Microstructural voids develop along grain boundaries when tensile loads remain constant over extended periods. These void networks eventually coalesce to form microcracks that degrade the conductivity and sensitivity of embedded gauges. For sensors in aerospace applications, high temperature dwell creep represents the primary failure mode during extended operational flights.
The damage is irreversible and lowers the fatigue threshold of the sensor housing.
Measurement Validation
High-precision dilatometers and capacitance strain gauges provide the displacement data needed to calculate steady-state creep rates. This verification step relies on stable reference temperatures to avoid thermal expansion noise that mimics plastic flow.
