[SI-LIST] AW: Ground vias around signal via
- From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- To: "aaditya.kandibanda@xxxxxxxxx" <aaditya.kandibanda@xxxxxxxxx>, si-list <si-list@xxxxxxxxxxxxx>
- Date: Thu, 16 Oct 2014 06:59:15 +0000
Aaditya: My opinion is, if we have a proper return path, they are not
necessary.
-> As Wolfgang said, GND vias are needed for proper return path because without
any GND via there will be no proper return path. You don't have to put multiple
of those around the signal via. with proper placement one is enough even for
very high speeds.
Aaditya: Any situations they are useful other than shielding?
-> Placing many stitching vias doesn't necessarily provide any shielding.
That’s an old Myth. Take a look at waveguide filters. The placement of screws
into the dielectric (air) looks and functions very similar to a PCB where the
energy also travels in the dielectric. Stitching vias can act as a filter,
meaning that some frequencies are not shielded but guided to the outside.
Aaditya: How will they help? When do we need them?
-> As already said, use GND vias to provide a proper GND return. as a rule of
thumb there should be a return via within the range of 1/8 wavelength (Nyquist)
to the signal via.
BR
Gert
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von Aaditya K
Gesendet: Mittwoch, 15. Oktober 2014 19:42
An: si-list
Betreff: [SI-LIST] Ground vias around signal via
Hello Experts,
I have a question on ground vias placement around signal via.
My opinion is, if we have a proper return path, they are not necessary. Am I
correct?
Any situations they are useful other than shielding?
How will they help? When do we need them?
Please help.
Thanks
Aaditya
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