This guideline addresses the major factors influencing the design of high-speed circuitry. Considerations include electrical noise, electromagnetic interference, signal propagation time, impedance, thermo-mechanical environmental protection, and heat dissipation. Supersedes IPC-D-317A. Key improvements over the IPC-D-317A document include updated impedance models for embedded microstrip, centered stripline and dual stripline geometries, expanded EMI layout practices, signal integrity design constraints, enhanced graphics and updated terms and definitions. 99 pages. Released November 2003.