RE: [SI-LIST] : Distance between Power and Ground planes

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From: Clewell, Craig W (ClewelCW@bergelect.com)
Date: Mon Jan 24 2000 - 10:00:52 PST


If you need to preserve the height, and cost is not an issue you might want
to stick a ground layer between your signal layers instead of moving the
pwr/gnd ratio. The farther apart you make them the longer the return path
becomes. This will cause some undesired coupling onto the signal line at
higher freq.

-----Original Message-----
From: Lee Ritchey [mailto:leeritchey@earthlink.net]
Sent: Monday, January 24, 2000 10:58 AM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Distance between Power and Ground planes

You sure can. This will reduce the size of the capacitor formed by the
power planes. This can cause higher frequency noise to increase.

david gil donate wrote:

> Hi,
> We have some problems with signal impedances between two PCB boards. We
want to rebuild the board with different layer heights to fit impedances. I
have to preserve the board height. Then when I try to reduce the distance
between the sig int 1 and power plane I add distance between ground and
power plane. My question is: Can I have some SI or EMI problems if I change
the distance between Power and Ground planes to 1.42 mm from 0.2 mm?
>
> Current PCB New PCB
> sig top -----------------------------
-----------------------
> 0.36
0.2
> sig int 1 -----------------------------
-----------------------
> 0.8
0.35
> grd -----------------------------
-----------------------
> 0.2
1.42
> pwr -----------------------------
-----------------------
> 0.8
0.35
> sig int 2 -----------------------------
-----------------------
> 0.36
0.2
> sig bottom ----------------------------
----------------------
>
> ------------------------------------------------------------------------
>
> Part 1.2 Type: application/ms-tnef
> Encoding: base64

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