NC pins making a net

Hello everyone,
I’m a total noob and I’m just correcting some errors on an existing PCB. I recently noticed that all the “not connected” pins (using a cross symbol on the schematic) in my layout seems to be connected, but I’m not even sure they are.
I assume they are because when I highlight one of those pin, they all light up, so I believe they form, somehow, a net.
I don’t see this net in Inspect > List Nets
I don’t see how they are connected, even with filled areas etc.
However, on a previous version of the PCB, those pins had somekind of label on them like X1 net 46, and it didn’t light all the other nc pins. Therefore I think it might have something to do with regenerating the netlist when I corrected some stuff on the schematic.
So my question is : are those pin really connected ? Is this a problem when generating gerber files ? If so, any idea on how to fix it ?

Thank you for your time, and feel free to ask for more info, i’ll try to be quick to answer

In v7, they are not “on the same net” for me. When I highlight one of the NC pins with the backtick (`), only that pin is highlighted. Same behaviour if I click on the pad, no others are highlighted, except the rest ot the layout isn’t darkened. See screenshot.

In any case, don’t worry. NC is definitely NC.

What version are you using?

Thank you for your answer ! I am using Kicad 5.1.
Indeed, i thought it would have generated a DRC error if they were in fact connected even though the schematic specified NC. Thank you again

Gosh, that is ancient, almost prehistoric.
It is also not a full version number. KiCad version numbers always have three numbers separated by two dots.
I had to scroll a few pages back in the Release Notes | KiCad EDA to get to V5.

If you want to stay with V5, then at least update to KiCad-5.1.12

The most common reason for using a very old KiCad version is having an old and unsupported windows version. There are ways to update to KiCad V7 on old windows systems, but I use Linux myself and never looked into the details for that.

Hi paulvdh,
My bad ! It’s KiCas 5.1.10 on Ubuntu. However I don’t have the freedom to update the software. I’ve been told it will create compatibility issues with specific custom libraries, so i’ll stay on this version. Thanks for your answer ! I appreciate it. I’ll take a look at the release note

I wonder who told you that, and why you believe him.
KiCad should always be able to read and convert both projects and libraries made by older versions, at least as far back as KiCad V3. Sure, there are some problems with project conversions, but most of those are user error. (for example deleting the [Project]-cache.lib or [Project]-rescue files).

If a conversion really does not work, then it is a KiCad bug, and it will get fixed quickly after reporting it. Such bugs have a high priority.

Those issues can be solved. However I would also check your Ubuntu version first. It may be out of support both by Ubuntu and by KiCad.

PS: I seem to remember that in v5 when you selected a NC pad, all the other NC pads would also highlight, probably due to a naive highlighting algorithm based on the name of the pad. But my memory may be unreliable and v5 is soon to be 3 versions old.

From schematic you know the pin numbers that are NC. Find koresponding pads at PCB and check if any track is going out of them and if they are connected to zones. On the left you have button to make zones visible. Zooming in at pad allows to examine it exactly.

Screenshot below, (KiCad V7.0.10) the net inspector clearly shows that each of the 8 unconnected pins have their own net (Asterisk in the search filter)

It is possible KiCad V5 handled this in some other way. KiCad V5 also does not have the net inspector as best as I can remember, but you can always use DRC. That will flag both unconnected pads and wrongly connected pads.

Another option is to just attempt to rout a track from one unconnected pin to another unconnected pin.