The pads are coated with a solder mask. The solder mask can be removed carefully with a sharp object.
Be careful you don't want to cut any traces. This could damage and destroy your device!
Pad size is 0.5mm
J14 Connector on Mainboard of SurfacRT - taken from https://arstechnica.com/gadgets/2012/10/under-the-surface-ifixit-breaks-down-microsofts-tablet/ and upscaled
J14 Schematic
If you can identify some pins feel free to update this Schematic template