Exposed pad in Stm32wb55rg connection with gnd mandatory or not?

[ajaykrishna097]

In my design I left the exposed pad in Stm32wb55rg VFQFN68 package. when I try to flash the device using st link , iam getting error "target not found". I am check the design and found i left the epad (69th pin) floating. Does this cause any issue ?. Please help me out here .thanks @Amel NASRI .

[STTwo-32 · Accepted solution]

Hello @ajaykrishna097 and welcome to the ST Community 😊.

So, as indicated on the DS11929, the exposed pad must be connected to ground plane:

 So, for a working design, you need to connect the exposed pad to the GND plane.

Best Regards.

STTwo-32

[ajaykrishna097]

Just to reconfirm, if I didn't connect the exposed pad to gnd then my design "will not work". Sorry for asking it again , if this is a issue that will for cause the MCU to not work, then I will redesign and initiate the manufacturing.

[ajaykrishna097]

One more thing, I have drilled the pcb from the bottom of the MCU and reached the exposed pad and check the connectivity with gnd it is connected, is the exposed pad internally connected to VSS. Note: I have not connected the epad to gnd, I checked it in a non populated pcb the epad is just not connected to anything, after soldering the IC then there is a connectivity from epad and gnd may be it is internal connected 

[STTwo-32]

To guarantee that the PCB will work on the best conditions, you should connect the exposed pad to the GND plane.

Best Regards.

STTwo-32