What’s the most effective method for connecting ground planes together on a PCB?
I’m aware that connecting ground planes at various points helps maintain a low impedance ground across the entire board and establishes a return path for signals. However, I’ve come across different approaches:
Adding vias close to every decoupling capacitor.
Implementing a grid pattern of vias with a spacing of 1/20th of the maximum wavelength on the board.
Placing vias along the traces.
Scattering vias randomly across the ground planes.
I’ve also seen a combination of these methods: vias along the lines along with randomly scattered vias on the ground planes.
What’s the recommended practice or the most efficient approach for achieving low radiation, good signal integrity, and power supply decoupling?
I’d go for all of them (within reason). Each one of these techniques was created to solve a specific problem (more or less). As such, each will contribute to the best performance of your board. You want to step back, look at your design, and see where you think problems might occur. You don’t want to place vias randomly or saturate the board with them, especially on a small PCB. But if you see parts of the circuit where a clear path to ground is not obvious, these are the tools to fix that.
What is your alternative that you think of as a default?
My assumption (feel free to correct me, or point out counterexamples) is that if you have enough layers for multiple ground planes, you have to tie them together somehow, and it might as well be near decoupling capacitors. You have to get the ground up to them somehow, and it would be strange if you had room for a long ground trace, but not room for a via. (Tying them together at only a single via to maintain “single point of connection” is maybe also an option, but it sounds like you’re assuming multiple connections.)
When you talk about “along the traces”, if you really mean “beside signal traces” rather than just “inside a ground trace”, then I assume that is a waveguide. Like the 1/20th grid, it should reduce interference in or out. I’ve seen it mostly on antenna feeds, and am guessing you don’t need it elsewhere until you’re working with very high speeds or very sensitive signals. But it shouldn’t hurt, either, unless you need controlled impedance, and forget to recalculate for the waveguide. Or if it eats through needed routing space on other layers.
I’m not sure what the point of “randomly scattered” is, except maybe “gotta connect it somewhere; plenty of room here.”