Surface Roughness Effect From Different Surfaces of Microstrip Lines and Reference Plane

Microstrip line structures consist of different conductors, such as trace and reference planes, which have different surface roughness levels due to the printed-circuit board manufacturing process. The bottom surface of the trace is often rougher than the top surface of the trace, and the roughness levels of different reference planes vary for different foil types and manufacturing processes. To accurately model the additional conductor loss caused by such differences in microstrip lines, a new modeling method is proposed with different roughness levels on different surfaces and a reference plane, in contrast to the traditional roughness modeling approach, which considers a uniform roughness distribution for all surfaces. The effect of the different surfaces on the resistance is determined by applying additional microstrip models to analyze the effect of surface roughness from different surfaces and to improve the accuracy of insertion loss prediction based on the modeled total resistance.