RE: [SI-LIST] : stackup question

Peterson, James F (jfpeterson@space.honeywell.com)
Wed, 15 Apr 1998 07:29:31 -0400

Layers 2 through 9 look great. It will be difficult to control things on
layers 1 and 10 (impedance, and crosstalk) since they don't have an
adjacent power plane. It would help if you went to a pads only approach
on 1 and 10, but then you would only have 4 signal layers.
good luck,
Jim Peterson
Honeywell Space Systems;

> ----------
> From: Ravinder Ajmani[SMTP:ajmani@us.ibm.com]
> Sent: Tuesday, April 14, 1998 11:26 AM
> To: si-list@silab.Eng.Sun.COM
> Subject: Re: [SI-LIST] : stackup question
>
> For a high-speed board, it will be necessary to use the stackup that
> will
> provide good inter-plane capacitance. I have observed that this
> capacitance is
> most effective for suppression of noise above 200 MHz. Based on this
> assumption, I would suggest the following stackup:
>
> Signal
> Signal
> Power
> Ground
> Signal
> Signal
> Power
> Ground
> Signal
> Signal
>
> This stackup provides 4 microstrip layers, and 2 stripline layers for
> routing
> high-speed signals. It also ensures that the two power planes will
> not overlap
> each other. You should provide sufficient vias between the two ground
> planes.
>
> Regards,
> Ravinder Ajmani
>
> Always do right. This will gratify some people and astonish the rest.
> ....
> Mark Twain
>
>
>
> owner-si-list@silab.Eng.Sun.COM on 04/13/98 07:54:36 PM
> Please respond to owner-si-list@silab.Eng.Sun.COM
> To: si-list@silab.Eng.Sun.COM
> cc:
> Subject: [SI-LIST] : stackup question
>
>
> I'd like to know what people think about the following stackup for a
> 10
> layer board with 2 power planes and 2 ground planes:
>
> Signal 1
> -4 mil-
> Ground 1
> -5 mil-
> Signal 2
> -8 mil-
> Signal 3
> -5 mil-
> Power 1
> -6 mil-
> Power 2
> -5 mil-
> Signal 4
> -8 mil-
> Signal 5
> -5 mil-
> Ground 2
> -4 mil-
> Signal 6
>
> The idea is first to get the impedance of all layers quite close, and
> secondly to get as much of the return currents as possible in the
> ground
> planes rather than the power planes (this is obviously not the case
> for
> signal layers 3 and 4, but I can keep my critical signals off them.
>
> Can anyone think of a better stackup, or are my priorities mixed up
> for a
> high speed (~100 MHz) digital board? Am I sacrificing high speed
> decoupling by not putting power and ground planes right next to each
> other?
> (One plane is 5V and the other is 3.3V, BTW)
>
> Regards,
>
> Paul
>
> --
> Paul Thompson crash@apple.com
> System Integrator, Macintosh Desktop Systems Apple Computer
>
>
>
>
>
>