Mehrdad, it depends on your goals. Ground near the bottom of a six layer stack-up has the advantage that you likely have more free real estate on the bottom layer to route with. If you use Lee's trick of a capped design, ( quasi eight layer ), then you have two well controlled impedance layers both referenced to ground, like they should be. The more signals that you reference against ground versus a power layer, generally, the easier your life will be. It also means that higher speed signals are pushed down in the stack and see less of a via stub. OTOH, ground near the top can be better for EMI. Regards, Steve. At 12:03 PM 4/26/2004 +1000, Mehrdad Salami wrote: >Hello All, > >I have a question about layer stack in PCBs. For a simple six layer like >(configuration 1) > >Top (Signal1) >Ground >Signal2 >Signal3 >Power >Bottom (Signal4) > >What would be the effect if the Ground and Power planes are swapped >(configuration 2) > >Top (Signal1) >Power >Signal2 >Signal3 >Ground >Bottom (Signal4) > >Assuming the same distance between Power or Ground to signal layers and >also the same track routing on the signal layers. > > >Regards > > > >Sal > >========================================== >Mehrdad Salami >Hardware Design Engineer > >Colour Vision Systems >11 - Park St - Bacchus Marsh >Victoria - 3340 - Australia > > > >------------------------------------------------------------------ >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