I have a microcontroller design that is implemented using a two layer PCB. All the components need to be placed on the bottom layer due to the fact that there is a display in the top layer.

In short, I ended up placing all the components in the same layer as the VDD power. The initial design without copper pour intended to be like the following picture: enter image description here

However, after placing copper pours, the result was this: enter image description here

At first thought, I believed that there were no problems at all with the result: The capacitors where near and there were big traces to the processor pin. But as a second thought, I realized that it could be defeating the purpose of the noise suppression capacitors as I was now giving the noise source a low resistance path into the processor's power pin. Therefore, I changed the copper pours to avoid this low resistance path and forcing current to go into the capacitors leads as shown: enter image description here

In essence, I'm asking anyone that has expertise in this matter to provide some comments and guidance about this design. Is there anything I am missing? I also don't see any problem with the fact that the processor is in the same layer as the VDD signal; if there is any problem, please comment.


It is indeed a mixed signal plane. Pipe's comments makes every sense for me thus I'm renaming VDDD plane to VDD.


1 Answer 1


First of all, you don't have a VDD plane (What's VDDD? I'll call it VDD). You have a mixed signal plane.

There's absolutely no problem having the processor on the same side as the VDD copper. If it was, it would invalidate every two-layer PCB I have ever seen. Don't worry about that.

Since you have already made sure that all your current paths are laid out exactly as you want them, I see very little need filling the plane with VDD. From your initial layout, I suggest that you simply route your power traces back to the supply. This assuming you have a ground plane on the other side. Otherwise try to route the power traces close to the corresponding ground.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.