The Si9000 versions 9.10 and above allow the user optionally to include the RMS value for surface roughness in frequency dependent calculations and chart dielectric losses along with conductor losses and attenuation values that include compensation for surface roughness. Versions 11.01 and above further extend the modelling into both RLGC and S-paremeter data.
Tick the Use Roughness Compensation check box and click Set… to specify the RMS values for trace and plane roughness.
Values for surface roughness (obtainable in consultation with the board manufacturer) are specified in the currently chosen units.
Typical values for RMS roughness could be in the order of 0.8 µm (0.03mils) for stripline, 1.6µm (0.06mils) for surface microstrip. The Si9000 assumes losses on both sides of a copper trace.
The Si9000 graph above charts all losses, the dielectric loss and the significant increase in the overall loss due to surface roughness, allowing the contributions of the different loss mechanisms to be isolated.