I hate it when datasheets do not clearly describe what to do with Extended Pads... Use the Cxxxxx part number to look up the part and then it's datasheet on LCSC.com: [https://datasheet\.lcsc\.com/lcsc/1809192027\_Ai\-Thinker\-ESP\-12S\_C82898\.pdf](https://datasheet.lcsc.com/lcsc/1809192027_Ai-Thinker-ESP-12S_C82898.pdf)<br> <br> The datasheet does not describe this pin 17, EP but if you look carefully at pin 33 on the IC in the schematic on page 13:  you can see that IC pin 33 is connected to ground on the module PCB. Pin 33 on the IC is an EP on the chip. From the images of the module this would appear to be connected to the module PCB ground by a multi-layer pad with multiple vias. The EasyEDA Symbol and the Footprint for the module has a pin 17 EP which is this central grounded pad on the module. This pin should be connected to ground and on the PCB, the pad should be connected to ground at least on the top layer, probably by a multi-layer pad with multiple vias. If you can find a datasheet for the IC then that may have more information. It might be helpful to ask JLCPCB for their recommendations on how to connect that pad to a surrounding ground plane: should it have heat shunts (spokes) or a direct, continuous connection? A direct connection is best for RF but JLCPCB may not be able to guarantee a reliable solder joint without heat shunts. :)

Have a look at the documentation here: [https://www.espressif.com/en/products/socs/esp8266](https://www.espressif.com/en/products/socs/esp8266)

Hi, I known the ESP8266EX and designed another board with it which has the same GND pad with 9 vias which is properly described in the ESP8266EX design guides. However from the ESP-12S it is not clear, but probably is the same pad. Hower ESP-12F pin 9 is also GND but maybe this is to make it backwards compitable with the ESP-12F? What doe you mean with "Pin 33 on the IC is an EP on the chip."? What is 'an EP'? Pin 17 is marked as EP, but what does it stand for? So you suggest to follow the same instructions as the ESP8266EX and just connect the middle pad with more vias to the ground plane top and bottom?

Replying to myself. EP probably stands for Exposed Pad (not extended pad as you said). I have send JLCPCB a question for this as you suggested. Thanks.

@igor_6537, Sorry for the confusion, EP = Exposed Pad. Thought that is a silly name for them because all pads by their nature are exposed... Thermal Pad or some of the trademarked names may be more helpful. :)

@igor_6537, As I said (slightly) corrected: "I hate it when datasheets do not clearly describe what to do with Exposed Pads..."; There is no mention of the Ground Pad (i.e. the Exposed Pad or EP) in the datasheet: [https://www\.espressif\.com/sites/default/files/documentation/0a\-esp8266ex\_datasheet\_en\.pdf](https://www.espressif.com/sites/default/files/documentation/0a-esp8266ex_datasheet_en.pdf)<br> <br> But see: **Section 1.6: PCB Layout Design** in: [https://www\.espressif\.com/sites/default/files/documentation/esp8266\_hardware\_design\_guidelines\_en\.pdf](https://www.espressif.com/sites/default/files/documentation/esp8266_hardware_design_guidelines_en.pdf)

Hi, Yes I know that esp8266 design guide. Used that before and properly grounded the chip EP to GND and with vias, before I switched to ESP-12F and now ESP-12S. It is still not clear, even after contacting ai-thinker if this EP needs to be grounded just like pin 9 (GND) or must be left ungrounded. And if it needs underlaying vias on the main pcb also.

ESP-12S-8285-2M (C2764056) footprint in EasyEDA links the EP to ground.