A Practical Approach to Analyze Copper Surface Roughness Effects with Applications to Stripline Structures

Conductor loss due to the roughened metal foil surface has significant effects on high-speed signals propagation on backplane traces designed for 10+ Gbps network. A practical method to evaluate these effects, including the signal attenuation and the propagation phase velocity, is proposed in this paper. A periodic structure is assumed to model the morphology of the roughness profile. The equivalent surface impedance is extracted from the grating surface wave propagation constant to model the roughness. This modified surface impedance can hence be used in the traditional attenuation constant formula to calculate the actual conductor loss. This approach is validated using both full-wave simulation tool and measurement, and is shown to be able to provide robust result within 0.2 dB/m relative error.