[SI-LIST] Re: 24-layer PCB Stack-up
- From: "Geva" <geva@xxxxxxxxxxx>
- To: <istvan.novak@xxxxxxxxxxxxxxxx>, <ched_chang@xxxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
- Date: Fri, 12 Mar 2004 09:17:55 -0800
I think Istvan is right about minimizing the number of ground layers.
Instead of using Gnd in between 2 signal layers, you can impliment 2 signal
layers in between 2 Gnd layers, in such way that the 2 signals will be close
only to one Gnd plane (~.04" approx.) and far away from each other (~.08"
dielectric thickness).
This way you will have signal in microstrip structure, with fairly good
isolation between the 2 signals, especially if they are in 90 degrees to
each other.
The stack up will looks like (partly):
4. Gnd
5. Signal
6. Signal
7. Gnd
8. Signal
9. Signal
10. Gnd
Ehood
you can use
----- Original Message -----
From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
To: <ched_chang@xxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Friday, March 12, 2004 5:55 AM
Subject: [SI-LIST] Re: 24-layer PCB Stack-up
> Chai,
>
> Usually board fabricators prefer symmetrical stackup, so you
> may want to arrange the ground and signal layers accordingly.
>
> Do you need the many GND layers to achieve a particular
> DC resistance?
>
> Regards,
> Istvan
>
>
> ----- Original Message -----
> From: "Ched-Chang Chai" <ched_chang@xxxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Sent: Friday, March 12, 2004 4:32 AM
> Subject: [SI-LIST] 24-layer PCB Stack-up
>
>
> > Dear all,
> >
> > I have a question about a PCB stack-up. Due to certain reasons, I must
> > design a 24-layer and 5mm thick board although we will be only using 8
> > signal layers. The other 16 layers will be Power or Ground. The signals
> are
> > operating at 166MHz. I have a few concerns about this board:
> > (1) the inductance and capacitance of through-hole via (they are 5mm
> long!).
> > (2) the effect of vias to power-ground decoupling (bypass, decoupling
> > capacitors).
> > (3) Electromagnetic Interference.
> > To minimize the above effects, I am thinking to set the stack-up as:
> >
> > 1. Signal
> > 2. GND
> > 3. Power
> > 4. Gnd
> > 5. Signal
> > 6. Gnd
> > 7. Signal
> > 8. Gnd
> > 9. Signal
> > 10. Gnd
> > 11. Signal
> > 12. Gnd
> > 13. Signal
> > 14. Gnd
> > 15. Gnd
> > 16. Gnd
> > .
> > .
> > .
> > Gnd until 24 layers.
> >
> > I set ground and power planes at layers 2 and 3 respectively to minimize
> the
> > via length associated with the bypass/decoupling capacitors. The other 5
> > signal layers are set closest to Layer1 to minimize the via length when
> > traces change layers. I sandwich the signal layer between Gnd planes to
> > reduce EMI effect.
> >
> > Is this a good choice? How to set a stack-up that can minimize the above
> > mentioned effects?
> >
> > Please advise me since I am green horn in PCB stack-up.
> > Thank you very much in advance.
> > --
> > Regards,
> > Chai
> >
> > _________________________________________________________________
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