[SI-LIST] Re: High speed signal on top layer

John in capping the tracks go on layer 2.  ( At least that is the way that 
I understand it. )  The microstrip plate up, and SM problems are simply 
avoided.

Steve.
At 12:39 PM 6/1/2005 +1000, Jon Keeble wrote:
>I'm still struggling to understand exactly what is "capping", and how it
>differs from simply being another layer, despite Steve's kind attempts to
>explain it.
>
>.. do the tracks remain on the outer layer ie do not require vias?
>
>The particular case that interests me is the multiGbit connections between
>Virtex4 MGT IO and SFP connectors.
>Xilinx have arranged for this to happen on the outer layer, i.e. no vias.
>Is "capping" going to help? i.e. mitigate the uncertainties of outlayer
>plating and soldermask on Zo?
>
>Regards
>
>Jon
>
>
>----- Original Message -----
>From: "Istvan Novak" <istvan.novak@xxxxxxx>
>To: <weirsi@xxxxxxxxxx>
>Cc: <jkeeble@xxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
>Sent: Tuesday, May 31, 2005 11:23 AM
>Subject: Re: [SI-LIST] Re: High speed signal on top layer
>
>
> >
> > Steve, John,
> >
> > Tradeoff with capping is it also means an extra layer (and for symmetry
> > reasons,
> > probably two layers) in the PCB .
> >
> > Regards,
> > Istvan
> >
> >
> > steve weir wrote:
> >
> > >John, that is where dielectric caps the uppermost signal etch.  This
> > >controls the copper dimensions, affording much better impedance control.
> > >
> > >Regards,
> > >
> > >Steve.
> > >At 07:41 AM 5/31/2005 +1000, Jon Keeble wrote:
> > >
> > >
> > >>Hi Steve ..
> > >>
> > >>What is 'capping'?
> > >>
> > >>Regards
> > >>
> > >>Jon Keeble
> > >>
> > >>----- Original Message -----
> > >>From: "steve weir" <weirsi@xxxxxxxxxx>
> > >>To: <george_dai@xxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > >>Sent: Tuesday, May 31, 2005 6:49 AM
> > >>Subject: [SI-LIST] Re: High speed signal on top layer
> > >>
> > >>
> > >>
> > >>
> > >>>George,
> > >>>
> > >>>1. Possible, but there are several pitfalls, including control over
> > >>>plate-up and solder mask.  Capping could help with those.
> > >>>
> > >>>
> > >>------------------------------------------------------------------
> > >>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
> > >>
> > >>
> > >>
> > >
> > >
> > >------------------------------------------------------------------
> > >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
> > >
> > >
> > >
> > >
> > >
> >
> >
> > -------------------------------Safe
>Stamp-----------------------------------
> > Your Anti-virus Service scanned this email. It is safe from known viruses.
> > For more information regarding this service, please contact your service
>provider.
> >
>
>------------------------------------------------------------------
>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
>


------------------------------------------------------------------
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

Other related posts: