Elimination of Conductor Foil Roughness Effects in Characterization of Dielectric Properties of Printed Circuit Boards


A new improved traveling-wave technique to characterize material properties of printed circuit boards over a broad frequency range is proposed. This experiment-based technique is the further development of the differential extrapolation roughness measurement (DERM) technique, which separates conductor loss from dielectric loss on PCB striplines. The new improved technique is called DERM2. It is applied to both loss constant and phase constant, as opposed to the DERM procedure, which deals with the loss constant only. The DERM2 technique allows for more accurate extraction of DK and DF values, as well as losses due to smooth conductor and rough conductor-dielectric interface. The application of the DERM2 procedure to a set of five test vehicles with the same dielectric and geometry, but different copper foil roughness, is demonstrated. A new metric called "roughness factor" QR to quantify roughness profiles has been introduced. The correlation between additional slope in insertion loss due to roughness and the QR factor has been established, and it leads to the development of the "design curves", which could be used by SI engineers in their designs.

Meeting Name

DesignCon 2014 (2014: Jan. 28-31, Santa Clara, CA)


Electrical and Computer Engineering

Research Center/Lab(s)

Electromagnetic Compatibility (EMC) Laboratory

Keywords and Phrases

Dielectric losses; Broad frequency range; Conductor loss; Design curves; Improved techniques; Phase constants; Roughness effects; Roughness factor; Traveling wave; Printed circuit boards

Document Type

Article - Conference proceedings

Document Version


File Type





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Publication Date

01 Jan 2014

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