Effect of Conductor Profile Structure on Propagation in Transmission Lines

Designers of high frequency electrical devices have long known that conductor surface roughness affects loss. Earlier correlations such as those of Morgan and Groisse underestimate insertion loss by a large margin at higher frequencies and on narrower transmission lines, where conductor effects dominate. The present work experimentally demonstrates that the recent Hall-Huray “snowball” model and the Sonnet conductor loss correlation correctly predict the shape of the insertion loss versus frequency curve up to 110 GHz, over a wide range of copper profiles. Quantitative agreement, however, requires empirical adjustment of the SA ratio, snowball radius or RMS roughness. “Rolled” copper foil, as well as some experimental ED foils, exhibit conductor loss that approaches that of theoretically smooth foil. Achieving good adhesion to these lowest profile foils is key to achieving low insertion loss on thin dielectric layers, such as those used in 77 GHz automotive sensors and high speed digital boards. This webinar will cover the following topics:
 

• Copper foil basics
• Copper profile measurements
• Hammerstad & Jensen and Sonnet software correlation
• Hall-Huray snowball model
• Copper foil data and images
• Differential insertion loss measurements and modeling

Presenter Bio:
Allen F. Horn III holds a bachelor’s degree from Syracuse University and a doctorate from M.I.T., both in chemical engineering. Since joining Rogers’ Lurie R&D Center, he has worked on the development and testing of ceramic powder-filled high frequency circuit substrates. He is an inventor or co-inventor on 16 U.S. patents in the area of high frequency dielectric materials. Before joining Rogers, he worked at Dow Corning on silicone thermoplastic materials and ARCO Chemical Company on polymeric oilfield chemicals.