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4 Layer PCB

tpr , 08-22-2021, 02:52 AM
Hello guys,

Supposing that i have a four layer pcb with one of the standards stackup (Signal L1, GND L2, VCC L3, Signal L4).

I would like to ask if it's right to pour copper (gnd plane) on top and bottom layer between tracks or not?

My theory is that on top layer it's not necessary because there is a solid gnd plane underneath, but what i have to do with layer 4?

Thanks in advance,

robertferanec , 08-23-2021, 02:04 AM
I would recommend to watch this video: How to Decide on Your PCB Layer Ordering, Pouring and Stackup (with Rick Hartley) https://youtu.be/52fxuRGifLU

PS: I normally do not pour GND between signals, however as you would see from the video, there may be situations when you maybe would like to do it.
qdrives , 08-27-2021, 02:15 PM
Do keep copper balance in mind. If layer 2 is solid gnd, make layer 3 as full a possible too. It prevents the board from 'curling'.
binayak , 09-09-2021, 12:27 AM

- What is the nature of the board - RF/digital/mixed signal? If digital, then how fast are the rise/fall times and what is the baud rate?
- Is it allowed to increase the layers to 6? If yes, then 6-layer would be much better.

- To your question of what to do with layer 4 in current scenario: if signal edges are slow enough (10s of ns) and data rate is low enough, then we can think of routing the signals on that layer similar to routing on a single layer board with signals routed as triplets - "SGS".

Hope this helps.
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