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What are the most important rules for grounding in a PCB? Can anyone explain with reasons?

We are making a PCB for electrical power systems in our project. It has high switching converters and some digital circuits too.

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  • \$\begingroup\$ For grounding what? Devices on the board? The board to other things? If you are playing with high voltages you need to start asking specific questions. \$\endgroup\$ – David May 23 '15 at 8:00
  • \$\begingroup\$ for grounding devices on board. voltages on the board are low. around 5-17 v. \$\endgroup\$ – Naveen May 23 '15 at 9:31
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Ground policy is not something you can learn in a single post. You must understand, that it is affected by the board architecture, the system, the enclosure, the standards you have to comply with.

Still, the question itself suggests that you are not going to pass EMI tests, so here are some simple guidelines :

Make a good ground plane- wide, as few holes as possible, thick copper layes.

Where you have high currents, cut the ground plane so the current is routed directly to the power source (connector? Filter) and does not flow under digital or analog circuits. You can even define DGND, PGND, etc. and connect them in a single point with 0R resistors.

Put capacitors that will connect AC to metal enclosure. Usually it's like 1uF and 10nF near each mounting hole. This is effective because the enclosure is thick and its impedance is very low.

For analog circuits pay attention that no digital return current flows under them.

Most importantly, have second chance to fix any problem with new layout.

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    \$\begingroup\$ Very well put. Depending on design the "as few holes as possible" might be confusing, multi layer designs might want many stitching vias, but that might be several steps too far at this point, so I can see leaving it out for now. More common to the 0R solution is "net-ties" though, since they can be made at any width and size. \$\endgroup\$ – Asmyldof May 23 '15 at 10:56
  • \$\begingroup\$ I must admit, i had to google net ties, and found a nice image of a grey tie with white squares. Where i work we have such components im one design, but we just call it a jumper. Cool, now i will seem more professional with that net tie :D \$\endgroup\$ – Gregory Kornblum May 23 '15 at 11:01
  • \$\begingroup\$ But about the subject, it's important to understand, that thin GND islands between holes that appear if the designer doesn't pay attention are not effective at all as GND plane. \$\endgroup\$ – Gregory Kornblum May 23 '15 at 11:04
  • \$\begingroup\$ Very good point, I read it differently, is all. In general the "don't make swiss cheese of your plane" is a very good starting sentiment, I was just trying to poke at you, see how universal you apply that rule ;-). Net ties are awesome. They are hidden on the finished product, but allow you to keep the ground or power domains neatly separated. Jumper could be a reasonable name, but they already stole that for the pins with the plastic connect-y thingies :-) \$\endgroup\$ – Asmyldof May 23 '15 at 11:33

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