Copper Surface Roughness Analysis in Mathematical Morphology Algorithm for the Insertion-Loss Validation

Insertion loss of a testing vehicle is widely referred for the material estimation, the differential pair and single-end striplines are generally employed for the high-speed digital applications. In addition to the matte side, the shiny side with the surface treatment of the inner layer is the critical issue for the insertion-loss improvement. In general, the inner-layer roughness is determined by the cross-section scanning electron or optical microscope photo with the manual defining of the average line. Therefore, the tolerance is produced from personal operation or gage repeatability and reproducibility (Gage R and R). In this study, a mathematical morphology algorithm is proposed for automatically detecting the roughness of the striplines. Basing on the algorithm and operating flow, the detected Rz and Rq values of the copper-foil roughness are applied in 3D simulation tool for the insertion-loss validation and comparison.