[SI-LIST] Re: One stitching via or more vias is better for 25Gbps application???

  • From: Leeyuyun <lee.home.61@xxxxxxxxx>
  • To: steve weir <weirsi@xxxxxxxxxx>
  • Date: Sat, 6 Sep 2014 22:37:11 +0800

Hi, Steve
Could you help indicate which paper in Simberian website is about vias
I want to clarify my question as below
# means stitching vias, * means signal vias, + means positive signal, - means 
negative signal
1. Only on stitching vias
+++++++++++++++++*++++++++++
                                  #               
--------------------------*----------------
2. At least two stitching vias
                                 #
++++++++++++++++*+++++++++++
------------------------*------------------
                                 #
For each structure, what is theory behind? What is your recommendation for 
stitching via structure in the 25Gbps structure?
Thank you
Lee

> "steve weir" <weirsi@xxxxxxxxxx> ©ó 2014/9/6 ¤U¤È8:31 ¼g¹D¡G
> 
> Typically, HFSS is used to design structures.
> 
> There is not a single correct answer.   Z axis transitions are not entirely 
> localized.  One could design a D pair  transition for a single pair and then 
> find out when they place that structure, that they have important differences 
> in performance due to other surrounding structures including other 
> transitions and stitch via patterns.  Simberian has several good papers on 
> their web site addressing these types of issues.
> 
> Steve
>> On 9/6/2014 5:16 AM, leeyuyun wrote:
>> Hi, Steve
>> Thanks your information
>> I have SI wave and HFSS software, and which one is better for 25Gbps 
>> application?
>> Do you agree P/N share the same stitching via is a good way?
>> Appreciate your teaching
>> Regards, Lee
>> 
>> > "steve weir" <weirsi@xxxxxxxxxx> ©ó 2014/9/6 ¤U¤È7:45 ¼g¹D¡G
>> > 
>> > "It depends".  In the general sense: Tighter stitching increases the
>> > lowest cavity resonant frequencies.  However stitching is not free, and
>> > where stitching goes particularly close to signal vias can have a big
>> > impact on how the overall structure performs.
>> > 
>> > If you want well controlled results that meet a particular loss budget,
>> > then you really need to model in a good solver.  You can always contract
>> > with someone to design your transitions for you. There are entire
>> > businesses built around getting structures like this right:  Teraspeed,
>> > Wild River, etc.
>> > 
>> > Steve
>> > On 9/6/2014 4:25 AM, Leeyuyun wrote:
>> > > Hi, all
>> > > I am doing 100Gbps (4x25Gps) product now
>> > > How do we put stitching vias when high speed signal change the layer?
>> > > This is a differential pair, which has P and N
>> > > Someone told me that one stitching vias is better because P and N share 
>> > > the common return
>> > > Someone told me that more stitching vias is better because loop 
>> > > inductance could be reduced more
>> > > I am confused which one is better?
>> > > Can anyone help me?
>> > > Thanks, 
>> > > Lee------------------------------------------------------------------
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>> > --
>> > Steve Weir
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> 
> -- 
> Steve Weir
> IPBLOX, LLC 
> 1580 Grand Point Way
> MS 34689
> Reno, NV  89523-9998 
> www.ipblox.com
> 
> (775) 299-4236 Business
> (866) 675-4630 Toll-free
> (707) 780-1951 Fax
> 
> All contents Copyright (c)2013 IPBLOX, LLC.  All Rights Reserved.
> This e-mail may contain confidential material.
> If you are not the intended recipient, please destroy all records
> and notify the sender.

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