copper pour on signal layers

Hi Everyone,

Does pouring copper on top and bottom routing layers give any advantage in a 4-layer board?I know in 2-layer systems it helps in reducing EMI and helps signals find the shortest return path.But if we have 4 layer board with solid copper does copper/ground filling in signal layers give any advantage??Please comment,

Regards
DB

It can reduce the impedance of ground and power planes further in some circumstances

If I don't ground fill signal layers in a 4-layer board will it give any performance difference?

For most designs, you should be fine with filling the inner ground and vcc plane.

I have poured copper on top and bottom layers (and all other signal layers) for years (at least 20), it helps balance the copper, helps with EMC, shielding routes, crosstalk etc etc.
Plenty of vias to stich the layers together.
Int' early days you had to do it using composite layers and combine them in Gerber land, but these days it easy, so I'd say do it

Definitely ground pour will improve the performane as far as EMC issues are concerned. Try to put some stiching vias also where ever possible. So the it will act as a good ground plane.
Care should be taken your ground pour is not affecting impedance of any microstripline impedence controlled traces.

There are some interesting emc related tips on Tech Tips point 10 about pcb stack-up

We work closely with the PCB manufacturers for our hugh speed boards, due to the complxity of both power requirements and signal speed. We will have 3 power/ground pairs 4 inner signal layers and the top and bottom layer for most of our HS designs. To minimise SSN (simultaneous switching noise) and improve power integrity our power/gnd pairs have a 0.1mm seperation to maximise plane capacitance. The copper pours around signals dont have as much effect on SI and impedance as they are edge coupled to the signal by the height of the copper.
Two excellent books that cover most of this are Henry Ott: Electromagnetic compatability & Howard Johnson: High speed digital design, they are worth having, even if some parts can get a bit heavy on the ild maths.

Thanks marce for good insight and suggesting the reading material.

NIKHILRAJ said:

Definitely ground pour will improve the performane as far as EMC issues are concerned. Try to put some stiching vias also where ever possible. So the it will act as a good ground plane.
Care should be taken your ground pour is not affecting impedance of any microstripline impedence controlled traces.

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Hi,
Could you please tell me more about stitching vias and need for using it? I am using PADS layout and I dont know how to add stitching vias. Is there any tutorial available to learn. Could you please solve my another post? https://www.edaboard.com/threads/262319/#post1122078

Regards,
Vikash.

Marce above has explained well enough about stitching vias and there uses. I didn't use PADS so can't help in that aspect.