Ground Pours or Thieving for Filling Unused Space on PCB Signal Layers

Question

Often at the end of a PCB design there is unused space on the signal layers. It is important to fill this space because of:

• The electroplating process (valid only for TOP and BOTTOM)
• The even distribution of copper on internal layers ensures the boards are flat at the end

There are two ways people in the industry solve this:

• Ground pours
• Thieving dots

The way I see it is that in 95% of the cases it is better to use thieving, just because it is easier and the chance to create an issue is lower as compared to ground pours. I do understand that ground pour can be a sensible solution as well provided that you make sure that it is really well stitched and that it does not interfere with the impedances of your high speed signals. However, I don't understand what benefits it provides that would make it worth for me to put in the additional effort. Still a lot of people do it, so I was wondering if someone has a nice overview of all the pros and cons of both approaches.

Answer 1

Rick Hartley gave a talk on advanced pcb design techniques that is available on YouTube. He is strongly against dots because dots float. floating things are uncontrollable EMI risks.

Now instead of mindlessly pouring ground one can also use this space to thicken the power distribution network.

But from my limited experience, the problem with thieving is not as severe and one can get away without fills most of the time.

Answer 2

I think I found my answer. For anyone who might be interested I am posting it here.

I found a good discussion on this topic. In Eric Bogatin's book Bogatin's Practical Guide to Prototype Breadboard and PCB Design, in chapter 22, myth #2 it says that there is no compelling reason to use ground pours in signal layers, and that they can only cause problems if they are left poorly connected. I recommend everyone to take a look at this book.