I can not route to inner layer

[nick38]

Hi,
I've changed my design from a 2 layer to a 4 layer. But now I noticed that I cannot route from the top layer to the second layer. I think that I need to add some kind of rule. What I found is that in the "PCB Rules and Constraints Editor" there is an option called "Routing Layers" and I only have to options: Top and Bottom. Is this why I'm not able to route from Top to the second layer or from the third layer to the bottom? The thing is that it won't let me add anything in this options
Thanks!

[Paul van Avesaath]

i think you have added internal planes instead of midlayer

[WhoKnewKnows]

To check this 👆 open the layer stack manager and confirm all layers are designated signal layers instead of plane layers

[nick38]

I can't see where the layers are signal or plane in the Layer Stack Manager.
This is how I have them setup.

[qdrives]

4th column from the left it states "Plane" for Gnd and VCC layers (2 and 3).
Click on it and change it to Signal.

[nick38]

Even after changing GND and VCC to Signal it still wont let me route from the Top Layer to GND. It only goes from the Top layer to the Bottom layer.

[WhoKnewKnows]

As a test case you could start a new 4 layer design with all four layers being designated signal layers, confirm you can route on any layers you like, then study what's different between the test case and your target design. It's likely gonna be the layer stack manager settings or rules, I think. Good luck 🤞

[Paul van Avesaath]

that is a good idea! maybe it could be that you have a Via defined as default via that is not allowing the connection on those layer.. you could copy a via from another design were it works an see if it connects on your new design to test this out.

but you mentioned Even after changing GND and VCC to Signal it still wont let me route from the Top Layer to GND. It only goes from the Top layer to the Bottom layer. did you define the plane to be GND and VCC as in go the the layer and doucble click it to define the net it attached to.. not sure but just naming the layer to GND doesnt connect it to the net GND

[nick38]

i think you have added internal planes instead of midlayer

Yes!! I changed it to Signal and now it lets me route! I think you have to save the project to make the changes effective and I wasn't doing that. But now I'm curious about why you have to defined them as signal and not planes, because after all they are planes (GND and VCC) right?. Thats why I chose them as planes.

[Paul van Avesaath]

yes you have to save indeed .

well on planes you draw inverterted. so they are physically the same copper layer whatever you call them plane or signal layer,
but on a plane everything you draw will be removed from the copper layer and with signal layers only that what you draw stays on the copper layer..

[qdrives]

You cannot "draw" on a plane layer.
You can place a polygon pour on a signal layer and have the 'effect' as a plane layer, but you can draw on that one.

[Paul van Avesaath]

yes you can, but not signals.. only lines to make split planes. I thought that I did not need to explain that..

[qdrives]

Paul van Avesaath do you "draw" the split in the plane??? I never used planes.

[Paul van Avesaath]

yes i draw them, that is how you use them
the benifit of using planes is for one, you can leave them on while routing the other layers since they are see through..
i really like planes its way easier and less processor heavy than all polygons.. they also do not require a repour when you drop lets say a gnd via in a power plane.. it just doesn't connect them
is also very easy to make "cutouts"underneath components if impedance requires this.