Issue link: https://iconnect007.uberflip.com/i/258943
28 The PCB Design Magazine • February 2014 in details. It is shown that proper separation of loss and dispersion effects between dielectric and conductor models is very important. With- out proper roughness model, dielectric models become dependent on the width of strips used in the test structures. If strip width is changed, difference in insertion loss predicted by models with roughness effect accounted in the dielec- tric models may be up to 20–30% off from the proper model with conductor roughness. Note that PCB materials are composed of glass fiber and resin, and have layered structure and thus display anisotropy. Separate dielectric models for composite and resin layers may be required as shown in reference 10, or vertical and horizontal components of dielectric con- stant will have to be separately identified. Also, differences in dielectric properties of glass and resin can cause further signal degradation in form of skew and jitter induced by the fiber- weave effect. Composite material models to ac- count for all these effects are available in Sim- beor software 8 . PCBDESIGN References 1. Y. Shlepnev, Modeling frequency-de- pendent conductor losses and dispersion in serial data channel interconnects, Simberian App. Note #2007_02, www.simberian.com/Ap- pNotes.php. 2. Y. Shlepnev, Modeling frequency-depen- dent dielectric loss and dispersion for multi- gigabit data channels (with experimental vali- dation), Simberian App. Note #2008_06, www. simberian.com/AppNotes.php. 3. P. G. Huray, O. Oluwafemi, J. Loyer, E. Bo- gatin, X. Ye, Impact of Copper Surface Texture on Loss: A Model that Works, DesignCon 2010. 4. Y. Shlepnev, C. Nwachukwu, Roughness characterization for interconnect analysis. Pro- ceedings of the 2011 IEEE International Sympo- sium on Electromagnetic Compatibility, Long Beach, CA, USA, August, 2011, p. 518-523. 5. Y. Shlepnev, A. Neves, T. Dagostino, S. McMorrow, Practical identification of dispersive dielectric models with generalized modal S-pa- rameters for analysis of interconnects in 6-100 Gb/s applications. DesignCon 2010. 6. Y. Shlepnev, System and method for iden- tification of complex permittivity of transmis- sion line dielectric, US Patent #8577632, Nov. 5, 2013, Provisional App. #61/296237 filed on Jan. 19, 2010. 7. Y. Shlepnev, System and method for iden- tification of conductor surface roughness mod- el for transmission lines, Patent Pending, App. #14/045,392 filed on Oct. 3, 2013. 8. Simbeor Electromagnetic Signal Integrity Software, www.simberian.com. 9. E. Bogatin, D. DeGroot, P. G. Huray, Y. Shlepnev, Which one is better? Comparing Op- tions to Describe Frequency Dependent Losses, DesignCon2013, paper and presentation, www. simberian.com/AppNotes.php. 10. W. Beyene, Y. C. Hahm, J. Ren, D. Secker, D. Mullen, Y. Shlepnev, Lessons learned: How to Make Predictable PCB Interconnects for Data Rates of 50 Gbps and Beyond, DesignCon 2014. Yuriy Shlepnev is the founder and president of Simberian electromagnetic Solutions, a company that develops and distributes electromagnetic signal integrity software for the design of PCB and packaging interconnect. PCB AND PACkAGING DESIGN UP To 50 GHz continues feature Table 1: Broadband material models identified in 10 . Dielectric constant and loss tangent values define Wideband Debye model (2), Dk values in brackets and loss tangent are from datasheets, roughness parameters are for modified hammerstadt model (eq. 4).