Is that okay to make ground unrouted polygon area of internal layer of PCB ?

[Kulunu]

Dear Robert and All,

I need some designing help regarding internal layer of PCB. Is that okay to make ground the unrouted polygon area of a PCB like follow ? I need to do this to make correct impedance of another layer routing traces.

Are there any impact to this layer traces if I ground polygon area ?

Hi Robert,
As an example lets take OpenRex open hardware layout. Let's take layer 10 of that PCB. If I apply polygon area to this layer 10 and if I make ground that polygon area will the Memory traces affect from that grounding change ?

Regards,
Kulunu.

[robertferanec]

I always try to have at least one solid GND above or bellow layer with impedance controlled tracks. Sometimes we do use partial power polygons (e.g. memory power polygon above/below memory tracks) as the second reference layer, often I use solid GND / PWR as the second reference plane. I almost never pour GND into empty space of signal layers as I read, that if it is not correctly done it can me your layout worse (e.g. if GND is noisy and there are some slivers - thin tracks with one end open going nowhere, they can work as antennas).

So, to answer your question directly, I do not know if that can help you as I do not use it. It may depend on the shape of GND polygon, where it is placed (if it really covers the right area) and how it is connected to the other ground planes/pins (if it really works as reference plane).