SI7005-B-GM1 データシートの表示（PDF） - Silicon Laboratories

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SI7005-B-GM1

DIGITAL I2C HUMIDITY AND TEMPERATURE SENSOR

Silicon Laboratories 

Si7005

4.7. PCB Assembly

4.7.1. Soldering

Like most ICs, Si7005 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. Devices should be

soldered using reflow and a “no clean” solder process, as a water or solvent rinse after soldering may affect

accuracy. See "11. PCB Land Pattern and Solder Mask Design" on page 34 for the recommended card reflow

profile.

It is essential that the exposed polymer sensing film be kept clean and undamaged. It is recommended that a

protective cover of some kind be in place during PCB assembly. Kapton®* polyimide tape is recommended as a

protective cover. See Table 12 below for examples of tape products that may be used for protection during the

soldering operation.

Alternatively, Si7005s may be ordered with a factory-fitted, solder-resistant protective cover that 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 "9. Ordering Guide" on page 31 for a list of ordering part numbers that include the cover.

4.7.2. Rehydration

The measured humidity value will generally shift slightly after solder reflow. A portion of this shift is permanent and

is accounted for when using the linearization procedure given above. After soldering, an Si7005 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.

4.7.3. 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.

Avoid water or solvent rinses after touch-up.

Minimize the heating of the device. It is recommended that soldering iron temperatures not exceed 350 °C

and that the contact time per pin does 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.

Table 12. Tape Products for Protection During Soldering

Manufacturer Part Number*

KPPD-1/8

*Note: Provided for information only.

Manufacturer

Kaptontape.com

Figure 8. Si7005 with Factory-Installed Protective Cover

Rev. 1.3

17

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