I’m currently designing a 4-layer board that utilizes dedicated ground planes for the inner layers, leaving the top and bottom layers for signal routing (no high-speed signals involved).
In my past experience with 2-layer boards, I’ve always included ground pours on both sides. My question is: On a 4-layer board with internal ground planes, is it still beneficial to add ground pours on the top and bottom signal layers, along with stitching vias?
Yes, if done properly. Biggest risk is creating ground areas too close to high frequency signal lines. The ground will capacitively load the trace and reduce the available signal.
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Like always the good answer is: it depends. You will take some benefit if the ground pour is connected to the internal layers but if you do that then the available routing area decrease dramatically and you create some barriers in case you need to cross the stitching vias line. The worse scenario is when a pour area is floating. In this case it is counterproductive. Doctor Eric Bogatin has some articles and webinars regarding copper pour. Take a look and most probably you will decide don´t include it in your new design.
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Certainly! Your choice of a signal-ground-ground-signal stack-up is optimal. With this arrangement, your signal traces benefit from being referenced to the adjacent ground plane, ensuring a low-impedance path for return currents.
While it’s generally not necessary to include a ground pour on the outer layers, there are potential benefits. It can simplify manufacturing by reducing the amount of copper that needs to be etched off, and it may offer advantages for thermal dissipation.
If you’ve already incorporated vias to inner planes near your ground connections and you’re not dealing with high-frequency signals, additional stitching vias may not be required. However, adding them won’t hurt, as long as you don’t overdo it and increase manufacturing costs unnecessarily. Another consideration is including ground return vias near signal and power vias when transitioning layers, ensuring that signals passing through those vias have a reliable reference “plane” in the vertical axis.
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