Ground Traces OR Ground Fill help


#1

Hello, I just ordered a PCB and it came back but I messed up on a couple of things. I want to make sure I have the Ground correct, but I’m very confused with the Ground and I keep seeing all kinds of different things.

I put all the traces for the Grounds on the bottom layer of the PCB and then I saw that you should add “Ground Fill Seeds” and add a “Ground Fill Layer”, I did that and then when I got the PCB back there were no visible Ground traces on the bottom, but I guess that is to be expected because of the Ground fill, I guess.


I have all the traces for the Motor GND and the Logic GND separated…

My question is, should I leave it like I have and just have the “Ground Seeds and Ground Fill” on the bottom layer, which would make the traces unnecessary, but would also leave the Motor and Logic GND the same (I think). If I do this way should I remove the GND traces?

OR

Should I leave the Motor and Logic GND traces separated on the bottom layer and not add the Ground Fill? If I do not add the Ground Fill do I place Ground Seeds…?

Thanks for any help, I am super new to this so any help is greatly appreciated!! :wink:

MP6500_ForumCopy.fzz (44.5 KB)


#2

Can you upload the sketch.

Probably doesn’t matter if the traces are there in the GND fill, it’s just that there is less isolation on the pins so you will have to add a bit more soldering heat.


#3

Sorry I meant to add it. I just added it to the original post


#4

The reason they have that isolation ring on the GND seeds is that it would be hard to solder without it, because the solid copper GND fill would suck all the heat out of your soldering iron and make the solder freeze. Hence why they delete the traces. Your traces add a bit more area to spread heat, but it’s probably not a big deal if you leave them because you can turn your iron up a bit.

As for separating the GNDs, Van is more of an expert than me. I have heard of it, and it’s probably a good thing, but maybe in this case it’s probably not that big of a deal. I know the separated GND join only at one point, and it is called a star ground.


#5

Either way should be fine. I played around a little with ground fill and as I expected it fills everything even if I set a ground seed only on the motor ground connection on the motor driver. With the ground fill you likely won’t see voltage drop problems anyway and if should work just fine. If you choose to not use the ground fill you should make the change in this sketch so the 7805 ground is on the logic ground circuit rather than the motor ground where it is currently. You want only the current to the motor flowing down the motor ground path, everything else should go to logic ground.

MP6500_ForumCopy1.fzz (44.8 KB)

Peter


#6

Ok, thank you! I just wanted to be positive before I spent more money.

Oh good catch! That’s strange too, I had that changed from the last time you helped me, not sure how it went back.


#7

Thanks so much Grey and Peter! You two have helped me out a ton, I really appreciate it!


#8

When you have the final version export the gerbers and check them with a gerber viewer such as gerbv as the gerber is what the board will look like coming back from the fab house.

Peter


#9

Hey Peter, I was wondering if you get a sec if you could take a quick look at the ground traces and make sure I have them in the correct place this time? No rush.

MP6500_ForumCopy.fzz (45.1 KB)


#10

Looks fine now.

Peter