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in the past I always used internal Signal layers, on which I created huge GND polygon planes as a ground plane. However, there are actual solid planes definable in Altiums Layer Stackup Manager, which can be assigned a dedicated net. So I assume, the proper way to define a ground plane is to define a plane in the Layer Stack Manager and assign the GND net.

Lets take the following exemplary scenario:

  1. Top Layer has some components
  2. You define microvias from top layer to inner layer 1
  3. Inner layer one is defined in Layer Stack Manager as a solid plane
  4. Afterwards assign GND net to inner layer 1
  5. You now choose a GND pad of some component on the top layer and try to route it to inner layer 1 using a microvia.

Step 5 cant be performed.

Please let me know, why this is not possible. What am I missing? When should you use planes and when should you use signal layers in Altiums Layer Stackup Manager in order to define your planes?

All the best,

This shows, that GNDPLANE_1 is assigned GND. Moreover, GNDPLANE_1 lies in between the top layer "Top Side" and the signal layer "Inner Layer 2"

This shows, the via assigned GND. This via actually represents two stacked microvias (as seen on the right). In the bottom, you can see that altium disables routing to GNDPLANE_1, even though it is assigned GND. (previous image)

Just for your reference, this is the current stackup.

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  • \$\begingroup\$ Is your via assigned to the GND net? \$\endgroup\$
    – Pangus
    Apr 11 at 18:49
  • \$\begingroup\$ Yes it's assigned to GND. \$\endgroup\$
    – 0xb16b00b5
    Apr 11 at 18:59

2 Answers 2

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I think planes are only usefull if you want to use impedance calculations and/or automatically impedance controlled traces. Altium can only do that when you route the traces over a plane.

In all other cases I think planes are inferiour to the flexibility of simple polygons on a signal layer. I for my part basically always use signal layers.

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  • \$\begingroup\$ This is exactly, what I was guessing. :) Thank you. \$\endgroup\$
    – 0xb16b00b5
    Apr 11 at 19:00
  • \$\begingroup\$ In this case special case, I have to use a defined stackup in order to compute impedances. However, when trying to connect to GND using a microvia to the next layer, altium automatically stacks two microvias, thus exiting on internal signal layer 2, skipping the actual plane. \$\endgroup\$
    – 0xb16b00b5
    Apr 11 at 19:02
  • \$\begingroup\$ Yes, as far as I know you can not have signal traces on a plane layer. If you want that, you would have to use cutout regions to create a small area in the plane, that you assign the desired net to. Not very useful... \$\endgroup\$
    – jusaca
    Apr 11 at 19:28
  • \$\begingroup\$ Damn, I really can't believe this is the intended behaviour. :/ There must be some way. However, marked as solved. Thx :) \$\endgroup\$
    – 0xb16b00b5
    Apr 11 at 19:38
  • \$\begingroup\$ And be aware, if you do place other stuff on the plane, the impedance calculations won't take that into account. The impedance calculations just assume a solid ground plane. \$\endgroup\$
    – jusaca
    Apr 12 at 16:10
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I don't think it matters much which one you use- one is defined in negative and one in positive.

For example, if you have several power domains on your power plane you can split the plane rather than using individual polygons. It might be easier to split in some cases rather than creating polygons that are close to each other.

If it's all one net, I don't see much to pick and choose.

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