Despite 85°C/85% being an overstress
condition for polymer-based humidity sensors, it may still be required for some
systems. Four approaches can be used if attempting to run 85°C/85% testing on a
system involving a polymer-based RH sensor:
- Run the system test, but exclude
the humidity sensor results – these devices functionally passed the silicon
qualification (an example of these qualification tests can be found on the Texas
Instruments quality and reliability page). You can populate humidity sensor
results afterwords, or exclude them from evaluation.
- Understand and accept that 85°C/85% testing will lead to a shift in sensor
accuracy – it is possible to characterize this shift in accuracy with testing,
but do not consider accuracy results as a pass/fail criterion for the test, as
lifetime operation within data-sheet recommended operating conditions will not
lead to such results.
- Choose a humidity sensor
specifically designed to minimize shifts after stress conditions – this includes
the HDC3020 family of integrated humidity and temperature sensors.
- Attempt to recover sensor
performance, after 85°C/85% testing, by leveraging the heater within the device
to correct for errors caused by the overstress conditions.