[SI-LIST] Re: Ground Pour in Signal Layers
- From: "Chris Padilla (cpad)" <cpad@xxxxxxxxx>
- To: <ivorlist@xxxxxxxxxxx>, <Pradeep.RSA@xxxxxxxxxxxx>
- Date: Thu, 23 Feb 2006 08:51:00 -0800
"Ground" pour can serve several purposes:
(1) Create shielded islands
(2) Create some extra interplane capacitance (not sure how useful it is
for charge storage as it is most likely located electrically far from
the chip needing the current)
(3) Balance out a layer to avoid warpage issues and to ensure better
trace dimension (impedance) control
I think (3) is the big one: Fab shops often request the ability to add
"thieving" in areas of sparse metal. Some folks just go ahead and add
the metal pour and often sink several "ground" vias through it to
connect it up to something. I forget the details why, but the fab shops
have better control of trace width if they don't have to etch away a lot
of metal.
As in all cases, such items can cause problems if not carefully handled
and thought through.
Chris Padilla
Cisco Systems
San Jose, CA
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Ivor Bowden
Sent: Thursday, February 23, 2006 8:38 AM
To: Pradeep.RSA@xxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Ground Pour in Signal Layers
Pradeep,
For what its worth, we routinely ground flood single signal layers that
are immediately adjacent to power layers to reduce ground impedance and
improve thermal conductivity, but we don't flood signal layers that are
paired with other signal layers to avoid impedance discontinuities.
Ivor Bowden
on 2/23/2006 12:04 AM Pradeep RSA wrote:
> Hi,
> does a Ground Pour in the Signal layers in a multilayer PCB=20
> (with sufficient internal ground planes) really helps?
> =20
> Thanks in advance
> Pradeep
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=20
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