Viscous Migration
Polymer migration process involves the slow, irreversible displacement of a soft protective gel compound within a sensor housing over time or temperature cycling. The gel fill creep governs the long-term drift of pressure sensors by altering the distribution of forces acting on the silicon strain gauge. It ceases to apply when the gel reaches a stable mechanical equilibrium or if the gel is completely cured to a solid state.
Thermal Hysteresis
Thermal fluctuations drive the relocation of the protective gel. During heating and cooling, the gel fill creep leads to a non-recoverable change in the sensor baseline. This effect manifests as a shift in the zero-pressure output after thermal exposure.
Hardware designers utilize high-viscosity gels to reduce this mobility under extreme operating conditions.
Sensor Distortion
Unequal distribution of the gel causes localized stress fields. The mechanical forces associated with gel fill creep are transmitted directly to the sensing diaphragm, generating offset error. These forces are measured during environmental qualification stages to ensure the product stays within its specified calibration bands.
Mitigation Strategy
Housing design represents the principal method for controlling material movement. Grooved chambers or physical retention rings restrain the compound and minimize gel fill creep. Selecting a gel with a narrow molecular weight distribution also helps.
