SI7015-A20 Datasheet, PDF (15/39 Pages) Silicon Laboratories – DIGITAL IC HUMIDITY AND TEMPERATURE SENSOR

Si7015-A20
4.6. PCB Assembly
4.6.1. Soldering
Like most ICs, Si7015 devices are shipped from the factory vacuum-packed with an enclosed desiccant to avoid
any drift during storage and to prevent any moisture-related issues during solder reflow. The following guidelines
should be observed during PCB assembly:
Si7015 devices are compatible with standard board assembly processes. Devices should be soldered
using reflow per the recommended card reflow profile. See Section “10. PCB Land Pattern and Solder
Mask Design” for the recommended card reflow profile.
A “no clean” solder process is recommended to minimize the need for water or solvent rinses after
soldering. Cleaning after soldering is possible, but must be done carefully to avoid impacting the
performance of the sensor. See application note, “AN607: Si70xx Humidity Sensor Designer’s Guide” for
more information on cleaning.
It is essential that the exposed polymer sensing film be kept clean and undamaged. This can be
accomplished by careful handling and a clean, well-controlled assembly process. When in doubt or for
extra protection, a heat-resistant, protective cover such as Kapton^® KPPD-1/8 can be installed during PCB
assembly.
Si7015s may be ordered with a factory-fitted, solder-resistant protective cover. This cover provides protection
during PCB assembly or rework but without the time and effort required to install and remove the Kapton^® tape. It
can be left in place for the lifetime of the product, preventing liquids, dust, or other contaminants from coming into
contact with the polymer sensor film. See Section “8. Ordering Guide” for a list of ordering part numbers that
include the cover.
4.6.2. 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 Si7015 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.
Rev. 1.0
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