[SI-LIST] Re: stitched via shielding
- From: Jim G Roberts <jgroberts@xxxxxxxxxx>
- To: Paul.Denomme@xxxxxxxxxxxxxx
- Date: Mon, 07 Apr 2003 17:28:16 +0200
Hi,
Just as a reminder, the highest frequency is a function of the rise time
[0.34/Tr]. Lambda/16 is often used but depends on your criteria.
Please note that if the proximity of the vias is similar to the ground
height, the vias will have an effect on the transmission i.e. the impedance.
--
Regards, __________ James G Roberts
/___ ____ | jrobert@xxxxxxxxxxxxxxxxxxxxx
Jim __ / /___/ / jgroberts@xxxxxxxxxx
/ /_/ /---| | Room: BE436, Hilversum
\____/ /_/ Tel: +31 35 687 4308 Fax: 5976
=================================================
"Denomme, Paul S." wrote:
> Hi All,
>
> I am looking to shield a trace using stitched vias. What is the general
> practice for stitching vias around a trace in order to obtaining shielding
> from the rest of the system?
>
> Here is my scenario:
>
> I have .2mm wide 10Ghz signal trace going down a PWB. The nearest trace
> running parallel to it is 0.2mm and the edge to edge distance of the traces
> are 0.9mm. I will have stitched 0.3mm DIA ground vias located directed between
> the two traces. What would the center to center spacing for the vias need to
> be to virtually contain the 10GHz signal?
>
> In practice I have seen via stitching rules of Lambda/20, and I have heard of
> people using Lambda/30. This is not a production board, but a test vehicle,
> so I am looking for what people are using today that helped them obtain
> acceptable results.
>
> Regards,
>
> Paul S. Denomme
> Design Engineer
> Viasystems
> 804-226-5155
> 804-226-5193 (Fax)
>
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