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The Chosen One , 06-04-2024, 01:38 AM

Just a general question, I currently am in the process of making a 4-layer PCB with a ground plane and just had two questions regard the planes.

1. I get that making a ground plan saves space, and they are useful, but for this design what do I do with the 4th plane? I have 2 signal, a GND, and the other should also be a GND? I only have one type of GND in the PCB

2. Related question, I have a couple resistors that are tied to ground and when I pour the GND plane, for some reason the resistors still to connect to one of the transistors in order for the ground to be connected.

Any advice on either of the queries?

Arkev , 06-04-2024, 10:21 AM

You could do sig-gnd-pwr-sig, or just go for sig-gnd-gnd-sig which is a good idea if you have very sensitive/RF traces

I didn't understand the 2nd point, maybe it's more of a software/project issue ?

Arkev , 06-04-2024, 10:23 AM

Zach Peterson has made a few videos/articles about PCB stackups, you can look them up if you want to learn more

Mini , 06-04-2024, 10:46 AM

We just had a thread about ground planes few days ago. Check this thread named: Multi-Layer Board Grounding question

Mini , 06-04-2024, 10:47 AM

I linked video from Rick Hartley there as well which you should watch.

Mini , 06-04-2024, 10:55 AM

1. Arkev already mentioned two combinations. I would add signal-gnd-signal-gnd(power routed). This is more for sensitive signals, since on layer 3 you will have ground on top and below. There is no "the best" layer stackup on 4 layers. There is so much you can only do. But you will get better explanations from Rick Hartley.

Mini , 06-04-2024, 10:59 AM

https://www.youtube.com/watch?v=ySuUZEjARPY

QDrives , 06-04-2024, 07:44 PM

1. This is already mentioned a few times here already. If you do not have that many signals or plenty space, I would go for sig-gnd-sig-gnd.
2) I assume you mean to pour a gnd polygon? A plane cannot be on the outer layers with components on it. For polygone pour the question is how is the thermal relief setting for those resistor pads?
- If they are set to no connection, then this is the result. Altium default is thermal relief. If you remove the checkbox pointed to in [2] in the screenshot above, it should connect.
- The other thing is that the default for polygons is to only connect to other (same net) polygons.