[SI-LIST] What's the purpose of stitching vias which just connect one GND layer?

  • From: Kevin Hou <Kevin.Hou@xxxxxxxxxx>
  • To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
  • Date: Tue, 3 Nov 2015 05:30:02 +0000

Hi Guru:
I found one interesting thing on Intel 6-layer(S-VCC-S-S-GND-S) CRB about the
stitching via.
There are pairs of stitching GND via put around the differential signals(PCIe
gen3) transited from TOP to BOTTOM layer.
The differential signal is VCC reference on the TOP layer and GND reference on
the BOTTOM layer.
My understanding for the stitching via is to provide the return path (GND
reference transited to another GND reference)
But in the Intel CRB I had on hand, these stitching vias are only connected to
one GND layer. What's the purpose?
Using capacitor to connect VCC/GND will be better, right?


Best Regards,
Kevin Hou






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