Soldering of BAT and Thermal pads on ESP32-C3 to a motherboard

The BAT pads are on the back of the XIAO ESP32-C3 which makes surface mount soldering to a mother board problematic. There is also a thermal pad, which I presume is the heat sink for the battery charger IC which may benefit from being soldered to the ground plane of the motherboard. Can anyone please suggest how these pads might be soldered to a mother board by hand? My thought was to add vias on the mother board so solder can be applied to the back of the mother board and wick through to the BAT pads and thermal pad.

I used the via method as you suspect… works perfectly.

Next round I may up the size a tad, works best if you pre tin the top side of the board and the batt pads on the Xiao.

Relevant to OP - I wonder, since those pads are so close to pins D2 and D3… Obviously this will fry the analog pins, but I wonder if there’s a way to just short the pads to those pins and use the pins superior mechanical strength and ease of soldering and rework as the battery terminals. Would that fry the adc capability of pins D0 and D1 also? What about the whole micro?

The pads are very frustrating to use. I’ve had three boards that were well soldered come loose after the whole project was assembled, they are just very tiny and weak. Very difficult to rework!

OK going to reply to my own post here because it occurred to me that one could (duh) cut the traces of those pins and just use the headers without fear!

Hi I would like to ask a follow up question on this topic. Anybody knows it the process of surface soldering the XIAO battery pads to a motherboard can be done automatically in a PCBA order?

Singing to the Quire here, Talk about a PITA,
I ovaled the pads on my latest PCB and pre tined all four pads (2-chip) and the PCB two.
With nothing soldered I clamp(gently with long spring clamp. Flip it over and solder the holes in the pads (SLOWLY) a tad more heat exposure but it works well. Then I flip it and solder 4-5 top pins, not soldering un-used pins. Took a couple tries but that’s the tech I’m using to hand attach each to my PCB’s 5 so far NO issues.
this is the first one,

GL :slight_smile:
NOTE: on the PCB order those holes are plated thru also.(called-out)