Some basic questions about grounds on 1 and 2 layer pcbs

[jasonc2]

I have no real experience laying out pcbs and I have no specific project or requirements in mind these are general questions. The circuits I have in mind are analog circuits with signals of varying frequencies and a single common ground for all components and DC power. The general goal is to reduce external emi effects as well as internal noise. I realize some of these questions may not have simple answers, in which case references to good reading material would be greatly appreciated.

- For a single layer board its simpler to route it if I just draw a big copper rectangle for grounds and run all the power and signal traces through it. Is this the way to go or is there a reason to use "normal" traces for grounds instead?

For a 2-layer board with through-hole components on the "top" layer:
- Should the ground plane be on the bottom layer, or on the top with power/signal traces on the bottom?
- Is it better to run all power through the ground layer or on the signal layer?
- If I have to run a trace through the ground plane to route the board, should I choose a signal trace or a power trace?
- If I have to run a trace through the ground plane, are there any considerations related to making cuts in the ground plane re: creating bottlenecks in / increasing distance of the ground path through the plane?
- Is it preferred to use existing through holes instead of vias where possible?
- Is there any reason why I'd want to have a power plane and traces for ground instead of a ground plane and traces for power?

Also can anybody recommend a good resource for how signal frequencies affect pcb design choices?

Thanks!

 

[amselden]

See in line comments:


- For a single layer board its simpler to route it if I just draw a big copper rectangle for grounds and run all the power and signal traces through it. Is this the way to go or is there a reason to use "normal" traces for grounds instead?

----The plane method is generally considered better than traces. Just make sure it connects to all required places (no islands).

For a 2-layer board with through-hole components on the "top" layer:
- Should the ground plane be on the bottom layer, or on the top with power/signal traces on the bottom?
----you can put ground on either side, but usually with a two layer board I do a power and ground plane. One on each side. I have found it to be more convenient to put ground on top for debugging purposes.
- Is it better to run all power through the ground layer or on the signal layer?
---- I usally put ground plane on top, power plane on bottom and signals on both sides. It is common practice to put horizontal traces on one side and vertical on the other. This often makes routing easier.
- If I have to run a trace through the ground plane to route the board, should I choose a signal trace or a power trace?
----see other notes.
- If I have to run a trace through the ground plane, are there any considerations related to making cuts in the ground plane re: creating bottlenecks in / increasing distance of the ground path through the plane?
----Watch your clearances to make sure not to create islands. Leave a clearance of at least your trace width for all ground plane bottlenecks (may need larger, look at amount of power expected and figure out what is your min). And remember when working with a plane there will be a keep out zone next to all traces though it. Usually tools will have the capability to turn on and off the viewing of your planes, it is easier to rout with the plane off, but make sure you turn it back on and check for bottlenecks and islands.
- Is it preferred to use existing through holes instead of vias where possible?
----If the through hole is convenient that is fine, or if you are having space issues it might be good, but generally there is no problem with using vias.
- Is there any reason why I'd want to have a power plane and traces for ground instead of a ground plane and traces for power?
----see other notes.

Also can anybody recommend a good resource for how signal frequencies affect pcb design choices?
----sorry, someone else will have to help you with this one.

 

[jasonc2]

Thanks! Those are the kinds of tips I was looking for. It seems much easier to route the board with a ground plane and power plane and horizontal/vertical traces on different sides. The ground plane on top for debugging tip is another good idea too.