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Ground Pour
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Please be positive and constructive with your questions and comments.

Ground Pour

by omerattiqahmed on Fri Apr 27, 2018 1:06 pm

Hi Community,

If Adafruit representative can comment, it would be ideal. I would like to know how you use ground pour in your boards. In most of the boards i have seen, there is no ground pour on the top layer. There might be one at the bottom layer then ?
Is it necessary to have ground pours on both layers ?
Safest ground pour clearance should be ... ? (It ultimately depends upon the manufacturer but i would like to know of a safe number)

Thanks,
Omer

omerattiqahmed
 
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Re: Ground Pour

by adafruit_support_mike on Sat Apr 28, 2018 1:00 am

Start with the assumption that the bottom copper is GND. It makes routing easier.. any time you need to connect a pin or compoent to GND, you can just pop a via through the board and be done with it. You don't have to spend time and effort trying to route GND connections among all the other signals on the component side.

The signals on the component side will fall into two categories: the ones you could route as a series of concentric circles, and the ones that form linked rings.

The first group are easy to route because the traces never have to cross each other. You can run them in parallel or wrap one around the end of the other, but can make all the necessary connections with solid traces in the same plane.

For the second group, that's impossible. You can only make the necessary connections if two traces cross each other somewhere. You deal with those by moving part of a trace to the bottom copper until you can bring it to the component side again.

Doing that cuts a slot through the GND layer on the back, so you have to make sure you keep the part connected to GND contiguous. The more signals you push through to the bottom copper, the easier it is to isolate a region so it isn't connected to GND any more. If you have vias for GND connections in that region, you have a problem.

Using GND pours on the component side is kind of iffy. If it makes routing connections easier, go for it, but that doesn't happen often.

For clearance, start with 0.012" and make it wider if you need to. Most board houses consider 12/12 pitch to be easy (0.012" traces with 0.012" spaces between them), and charge more as you start moving things closer together. That's more than enough gap for signals in the 0V to 5V range, but as you start using higher voltages and currents you'll need wider traces with wider spacing.

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Re: Ground Pour

by omerattiqahmed on Sat Apr 28, 2018 2:06 am

Thanks Mike for the insight !!

omerattiqahmed
 
Posts: 6
Joined: Sat Jul 30, 2016 9:53 am

Please be positive and constructive with your questions and comments.