Elevation in Overlapping Stackups

In overlapping stackups, dielectric layers must be continuous (i.e., stack on top of one another). They cannot overlap and there can be no gaps between them. To create an air gap between two dielectric layers, you must explicitly add a dielectric layer between them and define its material as “air”.

In contrast, signal layers can reside at arbitrary elevations and be embedded in a dielectric layer or at the interface of layers. Signal layers and negative signal layers can overlap one another. They can also have non-zero thicknesses.

Via layers must connect two signal layers.

To help you understand where each layer in an overlapping stackup is located, four elevation columns appear by default for overlapping stackups. The Lower and Upper columns refer to the layer’s elevations and can contain variables or expressions. The Evaluated Lower and Evaluated Upper columns provide calculated values for their elevations.

To change the order of layers in an overlapping stackup, choose on the following instructions.

Method A

1. From the Edit Layers ’ control grid, change the Lower value of the bottom most dielectric layer. This is the only layer whose Lower value can change.
2. Change the Thickness and Material of the other dielectric layers as chosen.
3. Add and remove dielectric layers as appropriate.
4. Change the Lower value for each signal layer that should move.

Method B

1. Change the stackup’s Type to a Laminate.
2. Click+drag the dielectric layers into the correct order.
3. Change the stackup’s Type back to Overlapping.
4. Changing the Lower value for each signal layer.