Hi,
Stress could yield to low and high humidity. The stress is invisible and it doesn't always yield to low humidity values.
In Bosch factory each BME280 is trimmed, calibrated and tested at chip level in the socket. And the H1-H7 values are stored in the NVM of each BME280. It is not possible to know how users will solder BME280 on their own PCBs. Since the formula to calculate the humidity from raw measurements and H1-H7 parameters is not linear, it is not possible to figure out new H1-H7 values and write them back to NVM. Users can perform compensation and save the calibration parameters in the flash memory of the host processor.
BME280 is MSL1 and doesn't need to be baked before soldering if BME280 storage is not beyond the specs. in Section 1.2. So you can use option 3 doing at approx 25degC with >40%rH for > 5 days.
Thanks.
... View more