[SI-LIST] Re: Ground Pour in Signal Layers

Yuming, there are definitely cases where pour can help.  But used 
improperly, it can cause a number of problems.  For example, on dual 
stripline, unless compensated for, the same patch that can make for a 
CPW drops the impedance to tandem nets creating impedance 
dips.  Another issue that comes up is how well it is bonded to the 
other Vss structures.  Whether or not it It is a good idea is yet 
another case of "it depends".

Regards,

Steve.
At 06:58 AM 2/23/2006, Yuming Tao wrote:
>Hi, Pradeep
>
>My point of view, Ground pour on the signal layers (especially =
>intra-layer) is not useful unless you intend to create a grounded shield =
>signal channel for special signal routing, eg. high-speed signals then =
>ground via-array is required to connect GND plane vertically. This will =
>take lot of routing area. If you are looking for isolation, adding =
>ground between signal traces won't help since the spacing is a =
>dominator.
>if you are routing high-speed signal traces on top/bottom layers, you =
>may think using ground pour to create coplanar waveguide (CPW) for high =
>signal quality.=20
>
>Regards,
>
>Yuming =20
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Pradeep RSA
>Sent: Thursday, February 23, 2006 3:04 AM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Ground Pour in Signal Layers
>
>
>Hi,
>       does a Ground Pour in the Signal layers in a multilayer PCB (with=20
>sufficient internal ground planes) really helps?
>=20
>Thanks in advance
>Pradeep
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