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5.3 Land Pattern

The land pattern is recommended to be designed according to the used PCB and soldering process together

with the physical outer dimensions of the sensor. For reference, the land pattern used with Sensirion’s PCBs

and soldering processes is given in Figure 17. Soldering of the central die pad, as well as an exposed copper

pad underneath it, is not recommended by Sensirion due to it acting as a heat sink which prevents the heater

from functioning according to its specifications.

Figure 17. Recommended land pattern (in mm). Details can vary and depend on used PCBs and solder

processes. There shall be no copper under the sensor other than at the pin pads.

5.4 Pin Assignment & Laser Marking

Pin

Name

Comments

1

SDA

Serial data, bidirectional

2

SCL

Serial clock, unidirectional input

3

VDD

Supply voltage

4

VSS

Ground

Figure 18. Pin assignment (transparent top view). Dashed lines are only visible if the sensor is viewed from

below. The die pad is not directly connected to any pin.

The laser marking consists of two lines, indicated in Figure 18.In the first line a filled circle serves as pin-1

indicator and is followed by “SH4”. The last character will indicate the accuracy class of this product (here

“x” serves as place holder). In the second line, the first three characters specify the product characteristics

according to positions 7, 8 and 9 of Table 11. The second three characters serve as internal batch tracking

code.15

15

Please note, there will be no change in the laser marking for the protective option (filter membrane and protective cover).