Chris, a little dielectric loss can be a good thing. In the dangerous realm of generalities, tighter stitching even on regular spacing is almost always better than looser stitching over a given planar area for the simple reason that it pushes the resonant frequency(s) up. Regards, Steve. At 12:04 PM 7/5/2005 -0700, Chris Padilla (cpad) wrote: >=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: >//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 > //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: >//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: > //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 > ------------------------------------------------------------------ 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 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: //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