Teraspeed Consulting and Samtec presented several papers at DesignCon 2015. Here’s a link to “Anisotropic Design Considerations For 28 Gbps Via to Stripline Transitions.”
For 28-56 Gb/s design the homogeneous isotropic material assumption is a key impediment in model to measurement correlation. Without accurate dielectric material models, it is impossible to close the loop between electromagnetic modeling and actual operation. Epoxy/glass PCB materials present a layered-anisotropic dielectric profile that varies in the x, y, and z direction. We will show that by using anisotropic dielectric models the modeling/simulation/measurement loop can be closed with simulation models of single-ended and differential vias.
A simple experimental design will be used to identify z-axis dielectric properties, and combined with GMS-Parameter measurements of x-y-axis properties. Accurate dielectric models for use in the modeling and simulation of trace and via structures will be demonstrated.