SI7022-A20 Datasheet, PDF (14/25 Pages) Silicon Laboratories – HUMIDITY/TEMPERATURE SENSOR WITH PWM OUTPUT

Si7022-A20
4.4.2. Rehydration
The measured humidity value will generally shift slightly after solder reflow. A portion of this shift is permanent and
is accounted for in the accuracy specifications in Table 4. After soldering, an Si7022 should be allowed to
equilibrate under controlled RH conditions (room temperature, 45–55%RH) for at least 48 hours to eliminate the
remainder of the shift and return the device to its specified accuracy performance.
4.4.3. Rework
To maintain the specified sensor performance, care must be taken during rework to minimize the exposure of the
device to excessive heat and to avoid damage/contamination or a shift in the sensor reading due to liquids, solder
flux, etc. Manual touch-up using a soldering iron is permissible under the following guidelines:
The exposed polymer sensing film must be kept clean and undamaged. A protective cover is
recommended during any rework operation (Kapton® tape or the factory installed cover).
Flux must not be allowed to contaminate the sensor; liquid flux is not recommended even with a cover in
place. Conventional lead-free solder with rosin core is acceptable for touch-up as long as a cover is in
place during the rework.
If possible, avoid water or solvent rinses after touch-up. Cleaning after soldering is possible, but must be
done carefully to avoid impacting the performance of the sensor. See “AN607: Si70xx Humidity Sensor
Designer’s Guide” for more information on cleaning.
Minimize the heating of the device. Soldering iron temperatures should not exceed 350 °C and the contact
time per pin should not exceed five seconds.
Hot air rework is not recommended. If a device must be replaced, remove the device by hot air and solder
a new part in its place by reflow following the guidelines above.
*Note: All trademarks are the property of their respective owners.
Figure 7. Si7022 with Factory-Installed Protective Cover
14
Rev. 1.1