FreeLists / si-list / [SI-LIST] Re: stitching vias

["Chris Padilla (cpad)" <cpad@xxxxxxxxx>]

=20
I would also say that it can cause problems and even resonances.  Most
ground stitching vias are placed very, very uniformly...this can be
very, very bad. :)  I would suggest an almost random placement of the
stitching vias...definately don't make them uniform.

Further, with stitching vias, when the energy hits the via, most of it
reflects (and its sign changes) and is now available to couple again
onto something.

I guess it is a matter of where and how you want this energy to leak:
out the edges of the board, out the top, coupling onto sensitive vias,
etc.=20

This is one area where a low-loss dielectric and stitching vias could
get one into much trouble.

For the record, I place stiching vias all around the periphery of my
boards and they are all uniformly spaced.  However, I do think about the
above situations and you should, too.


Chris Padilla
Cisco Systems
408.525.4989

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Lynne D. Green
Sent: Tuesday, July 05, 2005 11:48 AM
To: naren@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: stitching vias

Hello, Naren,

This is a good question.  Designs have failed when stitching was not
used.

Here is one failure mechanism: Without stitching, a crosstalk aggressor
signal can be coupled onto (and thus carried) by the "ground" (or
"power") trace.  This can then cause crosstalk from that "ground" (or
"power") net to another victim trace that is not physically close to the
original crosstalk aggressor.

Simulation can help you determine where and how much stitching is
required for a design.

- Lynne


"IBIS training when you need it, where you need it."

Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@xxxxxxxxxxxxxx


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Naren
Sent: Tuesday, July 05, 2005 6:59 AM
To: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] stitching vias

Hi gurus

I want to know that why stitching vias are required?

Please suggest me any web article, web portal etc (If Any)
------------------------------------------------------------------


------------------------------------------------------------------
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 FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:    =20
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20
------------------------------------------------------------------
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 FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu