[SI-LIST] Re: Differential BGA Breakout
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: garys@xxxxxxxxxxx
- Date: Thu, 12 Apr 2012 14:39:29 -0400
Both are acceptable from an SI perspective.
The first solution takes up fewer routing channels per layer, which is
why it is often used.
Assuming that the signals have matched delay up to the balls, option 2
is easier to skew match.
Scott McMorrow
Teraspeed Consulting Group LLC
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(401) 284-1827 Business
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On 4/12/2012 1:40 PM, Gary Stein wrote:
> With a uniform breakout of a 1mm BGA, one often sees a pattern such as:
> O O balls
> \ \
> x x vias
> ---/ /
> --------/ diff pair
> (forgive the crude ascii drawings!)
>
> Is there any significant issue to using a pattern like this at 10 Gbps?
> x
> /|
> ____/_|
> O O
> ~~~~~ | /
> | /
> x
>
> Excuse the lack of scale in these drawings, but in both cases the vias are
> the same distance apart.
> Assume proper return vias and other factors are the same. If any asymmetry
> is introduced, it would seem to be no worse than meanders for length
> matching and other short length discontinuities.
>
> Thanks,
> Gary Stein
> Network Instruments
>
>
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