Grounding the power layer of PCB

I'm developing a new PCB and I recently realized that all my power connections are on one side of the board, easily connected with a wide trace. So, I don't really need the inner power layer of the board. I do need an inner ground, though, since the ground connections are just all over the place. I don't have the option to order a 3-layer board from my manufacturer, so I'm stuck with a 4-layer board with internal power and ground.

Since I'm not using the power layer, should it be grounded? I'm thinking of grounding it at a single point there the power enters the board.

Yes.

If you don't ground it it can accumulate charge and cause all sorts of problems.

wanderson: I suspect fungus is intentionally providing you misleading information.

Huh?

He said: "Since I'm not using the power layer, should it be grounded?"

I assume it's not connected to anything. If so, it needs grounding.

(or connecting to Vcc, just don't leave it floating)

In a 4-layer board the inner layers provide the return path for signal traces on the surface layers - the surface trace and buried ground/supply layer form a transmission line, so its vital to both connect the inner power layer to something, and that that something is either ground or decoupled to ground in many places. (Assuming you have fast logic signals).

However here it sounds like you might have no signal traces on that side so it won't matter (assuming of course that the spare inner layer is that side).

It would probably be easier to use a two layer board and accept that you have ground traces interspersed with the power feeds on that side and are going to use plenty of feed-throughs. That will generally be considerably cheaper than using fewer feed-throughs on a four layer board.

Whatever you do, inductive and resistive effects will be at least as significant as capacitive, effects so any way you use the layer you should use more rather than less interconnections.

Im with fungus on this one , dont leave it floating.