AN607

12

Rev. 1.7

The Si70xx filter cover is compatible with standard reflow soldering. It provides lifetime protection against dust and

liquids and should not be removed after soldering.

Figure 9. Do Not Remove Si70xx Protective Cover

The reflow should follow JEDEC standards for lead free solder and reflow with a peak temperature of less than

260 ºC. “No clean” solder paste should be used. The use of an ultrasonic bath with alcohol for cleaning after

soldering is specifically not recommended. The Si70xx sensor opening must be kept clean and free of particulates

during assembly; the pre-installed white filter cover will protect the opening from particulates. Ensure the sensor

opening does not come into contact with conformal coatings. Do not expose the Si70xx to volatile organic

compounds or solvents. If installed, do not remove the white filter cover from the devices.

The use of water-soluble flux and water rinse after soldering is permissible if done with care. The use of DI water is

recommended. If the hydrophobic cover is used, a spray pressure of less than 40 PSI will prevent water entry into

the cover. Without the cover, care would need to be taken to avoid particles from the water or from blow drying to

contaminate the sensor area.

The high-temperature soldering process will introduce a recoverable shift in the sensor indication. Generally,

accuracy will be back within tolerance limits within 48 hours of soldering if the sensor is stored in normal ambient

conditions with ~50%RH.

4.4. Sensor Sensitivity to Chemicals and Vapors

The Si70xx is sensitive to many chemicals and fumes. Notably, household cleaning agents, such as ammonia, are

known to cause sensor readings to drift. To maintain accuracy of the SI70xx, avoid exposure to chemical fumes

and contaminants.

4.5. Recovering Calibration after High Humidity or Chemical Exposure

Typically, initial accuracy can be recovered by baking the sensor at 125 °C for 12 hours followed by ~2 days

storage period in normal ambient conditions with ~50%RH. High RH exposure (i.e., 75% RH for 12 hours) will

accelerate the post-bake recovery, but, after high RH exposure, approximately two days at normal RH is still

recommended for the device to fully recover its accuracy.

                                        

 

Do not remove 

protective filter