Managing a PCB Layer Stackup
You can keep working with your project or open it from the Workspace and continue from where the previous step is completed.
The PCB will contain four layers. Let's set up its structure with the Layer Stack Manager using the Design » Layer Stack Manager command. You can learn more about the Layer Stack Manager here. The Layer Stackup is supposed to look like the one shown below.
To add a new layer, right-click the layer where the new layer will be placed, then select the Insert Layer Below or Insert Layer Above command.
If you have the Stack Symmetry checkbox selected in the Layer Stack Manager Properties panel, a pair of layers will be added to maintain the board stackup symmetry.
Do not forget to specify the Dk parameter – we’ll need it, since there is a differential pair in the project.
Note: To quickly generate a board stack with the right number of layers, you can also use templates from the Tools » Presets menu. You can also change materials as needed or adjust their physical parameters in the table to meet your requirements.
In our project, all signal routes are 50 ohms, and the differential pair is 90 ohms. We will place them on the outer layers. The parameters of such lines are calculated in the Layer Stack Manager. It is necessary to switch to the Impedance tab, which is located at the bottom of the Stackup document.
Then press the button 
and set the values in the Properties panel as shown below.
The second and third layers should be excluded from the calculation.
Press the +Add button again and set values as shown below.
It will be the differential pair. Don't forget to click Save and Save to Server.
