[SI-LIST] Re: Layer Stackup
- From: "Steven M. Waldstein" <swldstn@xxxxxxxxxxxx>
- To: <calixlnguyen@xxxxxxxxxxx>, <chris.mcgrath@xxxxxxxx>,<si-list@xxxxxxxxxxxxx>
- Date: Fri, 9 Jan 2004 22:09:08 -0500
I have a follow up question.
My experience with other is that they prefer a stackup
more like
Signal
Ground
Signal
Pwr 1
Pwr 2
Signal
Ground
Signal
This is only an 8 layer example but I've been told they prefer
this to
Signal
Ground
Signal
Pwr 1
Ground
Signal
Pwr 2
Signal
Because all signals are uniformly reference to ground. And a signal
that has to go in both x and y stays reference to the same ground
plane. They prefer this and don't have to rely on local decoupling
when a signal changes layer to give the propeper return path.
Any comments about this or feedback.
Steve
swldstn@xxxxxxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Long Nguyen
Sent: Friday, January 09, 2004 1:50 AM
To: chris.mcgrath@xxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Layer Stackup
I agree. Having interplane capactance between power and ground planes also
provides another advantage is that you may be able to use thinner ZBC cores
with 2mils thickness instead of 3mils and thus reducing your overall board
thickness. In other words, you get 'free' buried capacitance for your
stackup at no additional charge.
-Long
----- Original Message -----
From: "Chris McGrath" <chris.mcgrath@xxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Wednesday, January 07, 2004 8:23 AM
Subject: [SI-LIST] Re: Layer Stackup
> David,
>
> Just out of curiosity, why are you going to Nelco 4000-13? From your
> original post it doesn't sound like you are overly concerned about
> routing lengths and you are not dealing with excessively high speed
> signals.
>
> Regarding Lee's post, I think it is good practice to have at least one
> pair of power and ground planes next to each other but having worked on
> a 42 layer board (Nelco 4000-13SI, 4 mils) that had interfaces running
> between 125 MHz and up to 1 GHz and routing it completely in a dual
> stripline stackup without any adjacent power and ground planes I think
> that proper coupling of the planes can be achieved without forcing you
> to muck with your proposed stackup. I should add that the 42 layer
> board carried a range of voltages including 0.9V from a daughter board
> (through connectors) and had no problems passing the EMI qualifications.
> Nothing involved with that board was easy, but it showed that what you
> are proposing can be done.
>
> -Chris
>
>
> > -----Original Message-----
> > From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx]=20
> > Sent: Wednesday, January 07, 2004 11:03 AM
> > To: david.kaushansky@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Layer Stackup
> >=20
> >=20
> > David,
> >=20
> > The problem you will have with this stackup is the lack of=20
> > interplane capacitance between power and ground planes. This=20
> > will manifest itself in several ways. Very high ripple on=20
> > your power supplies when transmission lines switch, =20
> > potentially very high EMI, unstable operation.
> >=20
> > It is imperative that you make sure that Vcc and ground=20
> > planes are close to each other. If you have several=20
> > different supply voltages, this will mean several pairs of=20
> > power planes.
> >=20
> > If you really need that many signal layers, it will be=20
> > necessary to add plane layers to get it right.
> >=20
> > Lee=20
> >=20
> >=20
> > > [Original Message]
> > > From: <david.kaushansky@xxxxxxxxxxxx>
> > > To: <si-list@xxxxxxxxxxxxx>
> > > Date: 1/7/2004 6:40:52 AM
> > > Subject: [SI-LIST] Layer Stackup
> > >
> > > The design I am working has a fairly dense placement. To=20
> > try minimize=20
> > > my
> > > time in artwork, I would like to add as many routing layers=20
> > as possible
> > to=20
> > > my layer stackup. I was thinking of using an 18 layer board of Nelco
> > > 4000-13, with the following stackup:
> > > Signal1
> > > GND
> > > Signal2
> > > Signal3
> > > PWR
> > > Signal4
> > > Signal5
> > > GND
> > > Signal6
> > > Signal7
> > > GND
> > > Signal8
> > > Signal9
> > > PWR
> > > Signal10
> > > Signal11
> > > GND
> > > Signal12
> > >
> > > The skinniest dielectric thickness is 4 mils, all signal layers are=20
> > > 0.5
> > Oz=20
> > > copper and plane layers are 1 Oz copper. The fastest signals are=20
> > > 100MHz,
> > > with rise times in 500ps range.=20
> > > My primary concern is the ratio of 6:12 of plane layers to signal
> > layers.=20
> > > I usually try to design for a ratio of about 8:10 or 9:9. I know I=20
> > > will
> > > have to be very careful about crosstalk on adjacent layers,=20
> > but other
> > than=20
> > > that, what else should I be concerned about?
> > >
> > > Thanks
> > > Dave
> > >
> > >
> > >
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