The conductive sheet traces are modeled using the surface impedance boundary condition:
:<math> \hat{n} \times \hat{n} \times \mathbf{E} = -Z_s\mathbf{J_s} </math><!--[[File:PMOM17(1).png]]-->
where Z<submath>sZ_s</submath> is the surface impedance of the conductive sheet. If the thickness of the sheet is greater than the skin depth of the metal at the project frequency, then the surface impedance is given by
:<math> Z_s = \dfrac{1+j}{\sigma \delta}, \quad \delta = \sqrt{\dfrac{2}{k_0 Z_0 \sigma}} </math><!--[[File:PMOM18.png]]-->
If the thickness t of the sheet is less than the skin depth, then the conductive sheet transition boundary condition is used instead, and the surface impedance is given by
:<math> Z_s = \dfrac{1}{[j k_0 Y_0 (\varepsilon_r - 1) + \sigma] \tau} = \dfrac{1}{\sigma_{tot} \tau} </math><!--[[File:PMOM19(2).png]]-->
When you start a new project in [[Planar Module]] with no traces defined, if you simply draw a new object, a default PEC trace is created and added to the Navigation Tree to hold that object. Alternatively, you can define your own new traces from the Layer Stack-up Settings dialog or directly from the Navigation Tree.