Why are there pads around the mounting holes in this pcb?

[jasonc2]

Looking at: https://en.wikipedia.org/wiki/File:VIA_VL810_SuperSpeed_Hub_Demo_Board.jpg

Does circle of pads surrounding the mounting holes serve some purpose?

 

[arbabar]

yeah when we fix the circuit board into the case(casing) we tight it through screws, these circle pads have naked PCB, it is therefore short with the body of casing and become common ground for the pcB and case(casing is usually ground).

 

[jasonc2]

I see, thank you. Is there a risk of ground loops when you use more than one screw or if grounded connector shields are also connected to the case?