[SI-LIST] Re: asymmetrical stack-ups

  • From: jspeiffer@xxxxxxx
  • To: weirsi@xxxxxxxxxx
  • Date: Thu, 20 Jun 2013 15:53:20 -0500

Steve,
you are absolutely correct.

Pushing the copper together between power and ground not only reduces 
noise and EMI, but also allows for thicker dielectric (for a given board 
thickness) to reduce crosstalk and/or better controlled impedance (reduced 
reflections).  Thus, improving the power integrity can not only have a 
direct improvement on SI but also an indirect improvement on SI by 
allowing more design options on dielectric thickness.

If you are not using a set board thickness, then the closer power/ground 
spacing reduces board thickness which generally equates to easier PCB fab, 
improved reliability and improved thermal characteristics.

Joel

Joel S. Peiffer
3M Electronic Solutions Division
3M Center, Building 201-1E-21
St. Paul, MN  55144
Tel:  (651) 575-1464
Cell:  (612) 327-1983
Fax:  (651) 737-4601
jspeiffer@xxxxxxx



From:   steve weir <weirsi@xxxxxxxxxx>
To:     si-list@xxxxxxxxxxxxx
Date:   06/20/2013 03:23 PM
Subject:        [SI-LIST] Re: asymmetrical stack-ups
Sent by:        si-list-bounce@xxxxxxxxxxxxx



The generic guidelines are to maintain channel continuity end-to-end as 
much as possible.  To do that well you need to understand your transmit 
and receive silicon as it is packaged.  Where you are going to 
transition return path:

Transition the signals with the least HF energy and least susceptibility 
to cross-talk and timing disturbances.
Transition the fewest number of times possible.

More separation reduces cross-talk.  The places to push copper close 
together is between power and ground, and between signal and return. 
The limitation on signal to return is etch width and etch tolerance to 
maintain a given impedance.  The places to push copper apart are signals 
to signals.

Steve.


On 6/20/2013 11:10 AM, train stop wrote:
> What are the general guidelines regarding implementing asymetrical
> stack-ups to compensate for a GND-Sig-Sig-PWR in order to encourage
> coupling to the utility layers for return current paths?  Are there
> recommendations to the thickness of the dielectric thickness between the
> Sig-Sig layer versus the GND-SIG or SIG-PWR.....so for interfaces below
> 400Mhz would an acceptable guideline be x3's.......I am just looking for
> some guidelines given lack of access to modeling tools.
>
> ------------------------------------------------------------------
> 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:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List forum  is accessible at:
>                 http://tech.groups.yahoo.com/group/si-list
>
> List archives are viewable at:
>                                http://www.freelists.org/archives/si-list
> 
> Old (prior to June 6, 2001) list archives are viewable at:
>                                http://www.qsl.net/wb6tpu
> 
>
>


-- 
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.

------------------------------------------------------------------
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List forum  is accessible at:
               http://tech.groups.yahoo.com/group/si-list

List archives are viewable at: 
                                 http://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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List forum  is accessible at:
               http://tech.groups.yahoo.com/group/si-list

List archives are viewable at:     
                http://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: