PCB layout of 2 layer board using Electra

[Nora]

I'm laying out a 2 layer board (top and bottom only) and am using an autorouter.
Proteus/ Ares software. The autorouter is Electra.

I decided to lay out the power manually first, putting ground on the bottom and power (24VDC) on the top.

Should the power and ground be "on top" of eachother (except for being on different sides of the board). Seems that I learned this somewhere once....
??
Thanks!
Nora

 

[b4bb4ge]

PCB layout

This is not necessary but on multi-layer boards when you have a ground plane and an power plane people like to do this because it adds capacitance to your board allowing for better power stability.

but if you are just routing the power and ground I would not recommend it because then if a signal needs to go through that area (where you laid the ground and power on top of each other) you will not be able to put a via there an go under to the other side and get around the power that way because the ground will be in the way.

hope this helps.

 

[arefeidi]

Re: PCB layout

Should the power and ground be "on top" of eachother (except for being on different sides of the board). Seems that I learned this somewhere once....

This would be a good thing for radio frequency (RF) layouts - if you'd e.g. have your signal path at the top layer and a whole ground plane at the bottom, the current in theory would flow back right below the signal layer then. So in this case, if you don't use a whole ground plane, it would be recommendable to put your power and ground lines on top of each other.

In low frequency or DC layouts, the "backward" current will use the shortest way back to your ground connection (way of lowest resistance), so the ground connection e.g. shouldn't go twice around your whole board and should be as short as possible.


But how important that is, is actually depending on what exactly you're designing. If there are no sensitive signals, it's isn't as important as it e.g. is in the receiving part of a mobile phone.

Though, if you use an autorouter, especially in RF-layout you don't really have to care about where to place your power and ground lines - as the completed board probably anyway wouldn't work at all. Autorouters usually don't give you a good layout (too many vias, very bad EMC performance). If you use it, doublecheck twice where it routes critical signals!