Digi XBee S2C 802.15.4 User Manual page 174

PCB design and manufacturing
While the underside of the module is mostly coated with solder resist, we recommend that the copper
layer directly below the module be left open to avoid unintended contacts. Copper or vias must not
interfere with the three exposed RF test points on the bottom of the module (see below).
Furthermore, these modules have a ground plane in the middle on the back side for shielding
purposes, which can be affected by copper traces directly below the module.
XBee/XBee-PRO S2C 802.15.4 RF Module User Guide
Recommended footprint and keepout
174