ST STEVAL-WBC2TX70 - Figure 49. Layer 4 GND; Ground Plane on Layer 4

7.2.2 Ground plane on Layer 4
The ground plane integrity on layer 4 shall be maximized as much as possible. Therefore, try to limit the number
of tracks routed on this layer.
Figure 49. Layer 4 GND
UM3286
Designing a wireless power transmitter based on STEVAL-WBC2TX70 evaluation board
UM3286 - Rev 1
page 65/84