[SI-LIST] Re: Stripline vs. Microstrip selection
- From: Luping Liu <liewluping@xxxxxxxxx>
- To: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- Date: Thu, 10 Jul 2014 17:46:19 +0800
Hi Gert:
Thank you for you advice, yes , our channel is BGA to MXP connector, and
the serdes are on the outer row of the pin map, so the signal can route out
on top layer without vias . What block us from use microstrip on this
~4inch channel is , both on simulation and measurement shows that , for M4
material, the Width/Gap =8mil /8mil micostrip have ~ 1.3dB/inch@12.5GHz
IL, and a 6mil/8mil stripline just have ~0.8dB/inch @12.5GHz, even consider
the via loss , I think stripline still have dominance, so we may use
Microstrip even we can route the signal without vias. May be we should ask
, does our IL measurement data right ?
Best Regards,
LIU Luping
2014-07-09 15:26 GMT+08:00 Havermann, Gert <Gert.Havermann@xxxxxxxxxxx>:
> Hi LIU,
>
> the answer was already given in your first link of the SI-List.
> It all depends on what and how you are comparing.
>
> Just use an Impedance calculator and check both options for your Project
> with the given restrictions in Stack-up, material, Layer count, EMI
> rules... and then you will find the best solution.
>
> One thing you should keep in mind is the impact of vias. If aou are able
> to route the signals without using vias, then Microstrip has advantages. If
> your Chip is a BGA and has vias anyway, then stripline should be the best
> option as no madditional vias have to be used.
>
> BR
> Gert
>
>
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> -----Ursprüngliche Nachricht-----
> Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> Im Auftrag von Luping Liu
> Gesendet: Mittwoch, 9. Juli 2014 08:25
> An: si-list@xxxxxxxxxxxxx
> Betreff: [SI-LIST] Stripline vs. Microstrip selection
>
> Hi All:
> I have a few 4 inch 25Gbps channel on my board,the design
> requirement is the lowest total loss first, and if possible , use hybrid
> stackup to reduce the cost (M6+FR4), but I am not sure if we can use
> microstrip to get lowest total loss, some different view points are found :
>
> 1.For the same trace width and copper thickness considerations,stripline
> results in less signal attenuation compared with microstrip.
> http://www.altera.com/literature/an/an672.pdf, figure 10 .
>
>
> 2. Stripline more lossy than Microstrip.
>
> //www.freelists.org/post/si-list/Stripline-more-lossy-than-Microstrip,2
> //www.freelists.org/post/si-list/Microstrip-vs-Stripline,6
>
> 3. Microstrip have more impedance variations
> 8_FR1Paper_MovingHigherDataRateSerial Designcon2014
>
> My question is :
>
> qs1. Why they have so much difference at IL@ 12.5GHz? if radiation loss
> play the role, does it have a knee freq which the microstrip loss over the
> stripline?
>
> qs2. Consider the via loss , is it better to use microstrip to get lowest
> loss for this <4 inch channel (all use 8mil width)?
>
>
> Thanks and Regards,
> LIU Luping
>
>
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