[SI-LIST] Re: High Speed Traces Under Card Edge Fingers
- From: Leon Wu <Leon.Wu@xxxxxxxxxx>
- To: Stefan Milnor <stefan.milnor@xxxxxxxxxxxxxx>, Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 9 Jan 2012 06:45:49 +0000
Yes, both CST and HFSS can simulate the effect of the GND plane underneath the
gold fingers.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Stefan Milnor
Sent: Monday, January 09, 2012 2:27 PM
To: Hermann Ruckerbauer; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: High Speed Traces Under Card Edge Fingers
Can current simulation tools and connector models really answer this
question about GND plane "pull back" on edge cards? I am no simulation
expert, but my understanding is that most simulation tools can not even
handle plane splits.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Hermann Ruckerbauer
Sent: Sunday, January 08, 2012 10:10 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: High Speed Traces Under Card Edge Fingers
Hi,
On Memory modules the Pullback is also done to adjust impedance of the
wider fingers.
I would assume that also on MXM3 the fingers are wider, so reduction of
the impedance should make sense.
As mentioned: Simulation can give a better answer then just assumptions
...
Hermann
Our next Events:
================
Visit us on Embedded World 2012
Our location Hall 1 / Booth 509
Check our website or contact us for details
EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer@xxxxxxxxxxxxx
Veilchenstrasse 1
94554 Moos
Tel.: +49 (0)9938 / 902 083
Mobile: +49 (0)176 / 787 787 77
Fax: +49 (0)3212 / 121 9008
schrieb Stefan Milnor:
> My PCB crew was routing some HS pairs along the edge under the
fingers,
> I was the bad cop and stopped them.
>
> If the planes are not pulled back, and the traces are isolated from
the
> fingers by planes, it would seem that the trace sig int would be OK.
>
> But I am getting the message that the "pullback is necessary" for the
> connector sig int performance.
>
> Although - Devil's advocate - the only place I can recall seeing this
in
> print is in the PCIe CEM spec. I don't see this recommendation in the
> MXM3 spec, or in the connector vendor's materials.
>
> Thanks, SM
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of steve weir
> Sent: Sunday, January 08, 2012 5:46 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: High Speed Traces Under Card Edge Fingers
>
> The pullback is necessary to maintain a relatively constant impedance.
>
> Were you routing high speed signals on inner layers in the finger
area?
>
> That's something I would avoid with or without the PCIe pullback
> requirement.
>
> Steve.
> On 1/7/2012 10:28 PM, Stefan Milnor wrote:
>> Hello Experts
>>
>> The "DDR3 Clock Failing Radiation Tests" discussions have been quite
>> interesting. But here is a different topic:
>>
>> "Remove Planes Under Card Edge Fingers?"
>>
>> In the PCIe CEM document, one finds the following statement:
>>
>> "On the add- in card, the ground and power planes underneath the PCI
>> Express high-speed signals (edge fingers) shall be removed.
Otherwise
>> the edge fingers will have too much capacitance and greatly degrade
>> connector performance"
>>
>> Is this really a concern?
>>
>> We are making small form factor boards with MXM3 connectors, and are
>> wondering if we have to relieve the planes in the "edge finger" area.
> If
>> we do so, then we lose some routing space, for high speed signals at
>> least, as we want to route these against a plain. This is a bit
>> painful.
>>
>> Thanks,
>>
>> Stefan
>> ------------------------------------------------------------------
>> To unsubscribe from si-list:
>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>
>> or to administer your membership from a web page, go to:
>> //www.freelists.org/webpage/si-list
>>
>> For help:
>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>
>>
>> List technical documents are available at:
>> http://www.si-list.net
>>
>> List archives are viewable at:
>> //www.freelists.org/archives/si-list
>>
>> Old (prior to June 6, 2001) list archives are viewable at:
>> http://www.qsl.net/wb6tpu
>>
>>
>>
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
