Possible to force unconnected copper fill to save on etching chemicals?


#1

I use ground planes on both side of a 2-sided pcb and I’d like to make the copper remain even if its not connected/needed without having to stick unnecessary vias or tracks…? So looking at this:

I’m wondering if there’s any smart way to force the right side to be filled simply to save on chemicals/earth…?


#2

Add a second copper zone with “no net” selected and a lower priority as your main zone.
(Example give your main zone the priority 1 and your no net zone the priority 0)
No net zones are created outside of the edge cuts area as well so draw it at most as large as your pcb will be.


Another maybe better option would be to add some stitching vias in the currently empty areas as this will allow better ground connections. (I know not really an option for you as you produce your boards at home without plated through holes. Adding this here for future users who have that option.)


#3

I’d look into adding a via or two, or re-routing a trace, through the empty areas to see if they would pick up the fill. Besides GND, is there some other circuit node - such as a supply rail - that could be used to fill the empty areas?

Filling unused areas with copper definitely saves on etching chemicals, and ground planes are generally a good thing, but occasionally a filled area creates capacitance that either couples noise into your circuit, or distributes noise from one section of a circuit to another, or affects overall circuit speed and stability.

Dale


#4

Besides GND, is there some other circuit node - such as a supply rail - that could be used to fill the empty areas?

The concept of prioritized zones is new to me. I have both +12V and -12V supply rails that are good candidates. If I now understand correctly I would be able to have many overlapping zones with set prio and that could possibly even save me some tracks… Gonna try it out, thanks!


#5

Add a second copper zone with “no net” selected and a lower priority as your main zone.
(Example give your main zone the priority 1 and your no net zone the priority 0)
No net zones are created outside of the edge cuts area as well so draw it at most as large as your pcb will be.

Maybe I’m misunderstanding, but I can’t seem to get it to work. I added zones over the whole board for:

gnd - prio 3
+12V - prio 1
no net - prio 0

but it’s just not filling out the no-net zone…

PS. Sorry for misusing the quoting mechanism, don’t know how to fix it…


#6

Try with only gnd and no net first. This should definitely work. (Tested in current nightly. But i remember it working like this already in version 4)

The 12V net might need a bit of extra work. You might need to design its outline closer to where you expect it to fill.


#7

Ok i played around a bit. I don’t know what i did differently than the first time around but now i can not get the no net zone to fill.


#8

Did you try smaller zones ?
Seems to work fine for zones inside GND fill, and and inside no-connected so no fill areas. (in V5)
The zones inside empty areas will fill, at any priority, but give a DRC error unless you make their priority higher.


#9

Yeah, it just doesn’t fill for me:

Only fills part that are not in a speced zone with higher prio, but then it would be too much work to setup the prio thing I thought was possible:

I’m on 6.0.0-rc1-dev-1469-g932b9a334, debug build


#10

You will need to define priority, to get full control over nested fill, but that is not too hard ?
My older V5 does fill (with both =0 priority), but does so with a DRC message, V6rc may be smarter to avoid doing the fill, that will then spawn a message.
ie your images look to be ‘expected behaviour’ ?


#11

I got the impression by previous answers that might define overlapping zones and in case the higher prio one wasn’t filled, the lower prio one would fill instead. That isn’t happening. It seems to me that the lower prio one is just overridden by higher prio one “pre-fill-calculation” so to speak.

You will need to define priority, to get full control over nested fill, but that is not too hard ?

Nothing hard with that, but it doesn’t fill unless I redraw the higher prio fill to not cover the area I want to fill with lower prio one. Basically leaving me do the fill calculation by hand if I want to solve the original problem of trying to get copper remaining for less etch.


#12

As a somewhat cumbersome workaround, what I can get working in my version (6 dev) is to first look at the GND fill and then add “no net” fill with higher prio within the unfilled parts:


#13

Great. sounds like you have a solution.
I’d not call it cumbersome, as you will have to tell the CAD tools somewhere, which of your nested coppers you want ‘to come out on top’.
Usually takes a couple of trails to get in phase with how it thinks.


#14

The cumbersome part being that I’d need to redefine the higher prio no net-zones if I reroute anything changing what will be filled by the ground plane:

I wish there was some setting that could tell a fill zone to fill even if unconnected.


#15

Looks like nobody has tested the “no net” fill. I had never heard of it either.
Time for a bug report.
Also my opinion is that the default zone priority should not be zero


#16

What happens if you draw your no-net zone aa a simple rectangle (to avoid the complex polygons you have drawn?
On 5.0.1, at least, it seem to be able to fill an unconnected net this way.
Starting with this;
10

Drawing a zone with these settings
04

Result;
37
EDIT FOR CLARIFICATION
Note - both the existing 3v3 zone and the new ‘no-net’ zone were both set to Priority 0 here.


#17

What happens if you draw your no-net zone aa a simple rectangle

This is exactly what I would have wanted and how I understood previous instructions here. But I definitely cannot get it working in 6 dev. The dialog there looks a tad different so I guess work has been done here in the nightlies?

Here is a GND rectangle with prio 4 covering the entire board and then a no net zone with prio 0 surrounding the whole thing:

Still no covering fill.

and

It doesn’t seem to have anything to do with the fact that’s it a no-net fill though. Same goes if I try +12V which is actually in there too:

It just seems to me that the prio is used before the fill of the zone is calculated. So anything covered by the high prio GND fill will just be eaten up by that and later ditched to nothing because nothing connected.


#18

Ah, ok, that makes a difference yeah. Hm… But then I don’t have control of which one to have prio… Seems to get a bit messy on my PCB. Not usable the way I interpreted previous posts.


#19

In the example I posted, the first zone I filled with a 3V3 plane with priority ‘0’. The subsequent fill of ‘no-net’ again, priority ‘0’, simply seems to fill the vacant space. I have just tried this on a recent nightly and seem to get the same behaviour.
Are you able to post your project for anyone to look at or is it NDA?



#20

Or make a copy of the project and reduce the board to minimum so that only the problem and the things necessary to reproduce it are there.