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Dielectric Dissipation Factor (DF) Extraction Based on Differential Measurements and 2-D Cross-sectional Analysis

Dielectric substrate properties are critical for highspeed circuit design. It is important to accurately characterize material's dielectric constant (DK) and dissipation factor (DF) after multi-layer PCB fabrication. A method using measured S-parameters and stripline cross-section geometry information to extract DF is developed. Unknown contribution of foil surface roughness to the transmission line loss is reduced by taking into account the ratio between the differential and common mode resistances (K). DF is extracted by relating it to the modal attenuation factors, PUL inductances and capacitances, and K. Several examples are provided using full-wave simulation and fabricated PCB, which demonstrate feasibility of the proposed method.