[SI-LIST] Re: Ground clearance at connector vias

Christian,

The recommendation is for an oval antipad that encompasses both vias of 
a differential pair, not just one.  And, yes, it is much better than two 
circular antipads around each via.


best regards,

scott

-- 
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com




Christian Schuster wrote:

>Fabrizio and all the others:
>
>  
>
>>I have a question regarding ground clearances for signal vias in a
>>backplane connector, like the Molex/Teradyne HSD.  Connector and
>>semiconductor manufacturers recommend using an oval ground clearance
>>around the differential pairs, to minimize reflections.
>>    
>>
>
>I completely agree that increasing antipad sizes is one way to reduce
>parasitic via capacitiance. What makes me wonder is the fact that 
>oval shapes are proposed. Is that a mechanical/space requirement?
>
>If not: has anybody ever seen a difference in via transmission between a
>circular and an oval antipad of the same area?
>
>
>Regards,
>
>Christian Schuster
>IBM 
>
>
>
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