For TrueVolume metal, you input four parameters: metal thickness, direction, Z-Mesh method and a fourth parameter which specifies the loss. For the fourth parameter, you may choose bulk conductivity, resistivity, or sheet resistance at DC. The loss is calculated in the same manner as for the Normal metal type, except that the thickness in this case represents a physical thickness which eliminates the need to enter the current ratio. The direction setting determines if the metal extends upward into the dielectric layer above, or down into the dielectric layer below. Up is the default.
For a detailed discussion of TrueVolume metal, including an explanation of the Z-Mesh method choices, see Physically Thick Metal.