In this guide
What NTC thermistor aging means
NTC aging is a time-dependent, usually irreversible change in a component’s electrical characteristics. It may affect resistance at the rated temperature (R25), the B value, or the measured resistance–temperature (R/T) curve. Aging does not produce an identical shift in every thermistor: the magnitude and direction depend on the material, construction, process history and conditions of use.
TDK’s NTC technical information describes commonly observed resistance increases and B-value changes, and discusses mechanisms including thermal stress, oxygen exchange in unprotected non-glass-encapsulated parts, and diffusion at metallized contacts. This describes possible mechanisms, not a guaranteed drift pattern for every product. A blanket claim that sensitivity always decreases or that all NTCs require the same calibration interval is not justified.
What can cause resistance drift
- Time and temperature: solid-state changes can continue in storage and use; higher temperature can accelerate some mechanisms. Review the part’s rated conditions and long-term data.
- Humidity and surrounding media: protection, coating, sealing and terminal design influence exposure. Do not infer moisture resistance from the NTC technology alone.
- Electrical load: current causes self-heating. Sustained or excessive power can change the component temperature and add stress; evaluate the actual circuit and thermal dissipation.
- Assembly and mechanical stress: soldering, board flex, potting, molding, thermal expansion and contact materials can affect the assembled sensor. TDK advises evaluating sealing/potting processes and testing their influence on functionality and reliability in its glass-encapsulated sensor documentation.
Drift can become a measurement error when the system continues to convert resistance using the original curve. The resulting temperature error depends on where the shift occurs on the curve, circuit resolution, sensor tolerance, calibration and the operating interval.
How OEMs evaluate and manage stability
Read reliability data with its test conditions
Compare data for the exact part family and orderable specification. Check the stated change limit, test duration, temperature, humidity, electrical or mechanical stress, sample conditions and measurement method. For example, the TDK M820 leadless NTC documentation lists an empirical long-term stability result under 70 °C for 10,000 hours. That result is specific to its stated series and conditions, not a universal NTC lifetime guarantee.
Control the sensor and assembly stresses
Keep operating temperature and electrical load within the selected part’s limits. Confirm that coatings, potting, cleaning agents, terminals and mounting stresses are compatible with the sensor. Where enclosure or assembly changes the thermal or environmental exposure, validate the final construction rather than relying only on bare-component data.
Set verification and calibration from system requirements
Record incoming baseline resistance or R/T data where required, then define post-assembly or environmental checks with acceptance limits tied to the system’s error budget. Use aging or qualification tests that represent the real temperature, humidity, power and mechanical conditions. Establish recalibration intervals from measured drift, risk and application requirements; periodic calibration is not automatically necessary at one fixed cadence for every NTC design.
Specification checklist
For an OEM stability review or quotation, provide:
- Exact NTC type, construction, R25, tolerance and B/R/T curve data.
- Operating and storage temperature profiles, humidity and surrounding media.
- Measurement current, power dissipation and self-heating allowance.
- Mounting, soldering, board-flex, potting/sealing and cleaning details.
- Required lifetime, allowed resistance/temperature drift, test method and acceptance criteria.
- Traceability, supplier reliability reports and any application qualification requirements.
For related design issues, see our NTC thermistor trade-off guide and glass-encapsulated NTC selection guide. Browse NTC products or send your stability requirements for an OEM review.
