Printed Circuit Design & Fab - December 2007 - (Page 27) FIGURE 2. E field distribution, narrow via spacing of 1.3X height over ground. (Image courtesy of Dr. George E. Ponchak of NASA GRC.) FIGURE 1. E field distribution, wide via spacing of 5.2X height over ground. (Image courtesy of Dr. George E. Ponchak of NASA GRC.) Unwanted Coupling We also have to deal with unwanted coupling. Unwanted coupling is any coupling of energy from one system to another where it is not intentionally designed as a part of the circuit. There are several sources or “entries” for unwanted coupling: the most obvious path is direct coupling in the form of inductive and capacitive coupling between signal conductors. Today, it is commonly understood that wide traces at narrow spacing far from ground will have large mutual capacitance and inductance and, hence, be able to couple energy between them. Since this is obvious, it becomes second nature to control this direct coupling. The really nasty and sneaky scoundrel is indirect coupling from the power/ground system, and signal return paths. In a circuit schematic, we only draw the signal paths, and the return path is implicit. Everyone knows that a return path is needed, or the circuit remains open and will not work. You don’t typically wire them as you do with signal conductors. They appear indirectly as a consequence of your wiring and the design of your power/ground system. The smart thing about return paths is that the circuit will find one if one exists, or we would have an open circuit. The bad thing is Find the cure. High Variety of Pitches, Signal Routing, Stack Heights and Terminations www.samtec.com/signal_integrity http://www.samtec.com/signal_integrity
Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - December 2007 Printed Circuit Design & Fab - December 2007 Contents Our Line Market Watch Around the World Happenings ROI 2007 PCB Designer Salary Survey Interconnect Strategies Positive Plating RF Design Ad Index Noise Reduction Supply Chain DfM Off the Shelf Marketplace The Signal Doctor Printed Circuit Design & Fab - December 2007 Printed Circuit Design & Fab - December 2007 - Printed Circuit Design & Fab - December 2007 (Page Cover1) Printed Circuit Design & Fab - December 2007 - Printed Circuit Design & Fab - December 2007 (Page Cover2) Printed Circuit Design & Fab - December 2007 - Printed Circuit Design & Fab - December 2007 (Page 1) Printed Circuit Design & Fab - December 2007 - Contents (Page 2) Printed Circuit Design & Fab - December 2007 - Contents (Page 3) Printed Circuit Design & Fab - December 2007 - Our Line (Page 4) Printed Circuit Design & Fab - December 2007 - Our Line (Page 5) Printed Circuit Design & Fab - December 2007 - Market Watch (Page 6) Printed Circuit Design & Fab - December 2007 - Market Watch (Page 7) Printed Circuit Design & Fab - December 2007 - Market Watch (Page 8) Printed Circuit Design & Fab - December 2007 - Around the World (Page 9) Printed Circuit Design & Fab - December 2007 - Around the World (Page 10) Printed Circuit Design & Fab - December 2007 - Around the World (Page 11) Printed Circuit Design & Fab - December 2007 - Happenings (Page 12) Printed Circuit Design & Fab - December 2007 - Happenings (Page 13) Printed Circuit Design & Fab - December 2007 - ROI (Page 14) Printed Circuit Design & Fab - December 2007 - ROI (Page 15) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page 16) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page V1) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page V2) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page 17) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page 18) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page 19) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page 20) Printed Circuit Design & Fab - December 2007 - 2007 PCB Designer Salary Survey (Page 21) Printed Circuit Design & Fab - December 2007 - Interconnect Strategies (Page 22) Printed Circuit Design & Fab - December 2007 - Interconnect Strategies (Page 23) Printed Circuit Design & Fab - December 2007 - Positive Plating (Page 24) Printed Circuit Design & Fab - December 2007 - Positive Plating (Page 25) Printed Circuit Design & Fab - December 2007 - RF Design (Page 26) Printed Circuit Design & Fab - December 2007 - RF Design (Page 27) Printed Circuit Design & Fab - December 2007 - Ad Index (Page 28) Printed Circuit Design & Fab - December 2007 - Ad Index (Page 29) Printed Circuit Design & Fab - December 2007 - Ad Index (Page 30) Printed Circuit Design & Fab - December 2007 - Ad Index (Page 31) Printed Circuit Design & Fab - December 2007 - Noise Reduction (Page 32) Printed Circuit Design & Fab - December 2007 - Noise Reduction (Page 33) Printed Circuit Design & Fab - December 2007 - Noise Reduction (Page 34) Printed Circuit Design & Fab - December 2007 - Noise Reduction (Page 35) Printed Circuit Design & Fab - December 2007 - Supply Chain (Page 36) Printed Circuit Design & Fab - December 2007 - Supply Chain (Page 37) Printed Circuit Design & Fab - December 2007 - Supply Chain (Page 38) Printed Circuit Design & Fab - December 2007 - Supply Chain (Page 39) Printed Circuit Design & Fab - December 2007 - DfM (Page 40) Printed Circuit Design & Fab - December 2007 - DfM (Page 41) Printed Circuit Design & Fab - December 2007 - DfM (Page 42) Printed Circuit Design & Fab - December 2007 - Off the Shelf (Page 43) Printed Circuit Design & Fab - December 2007 - Marketplace (Page 44) Printed Circuit Design & Fab - December 2007 - Marketplace (Page 45) Printed Circuit Design & Fab - December 2007 - Marketplace (Page 46) Printed Circuit Design & Fab - December 2007 - Marketplace (Page 47) Printed Circuit Design & Fab - December 2007 - The Signal Doctor (Page 48) Printed Circuit Design & Fab - December 2007 - The Signal Doctor (Page Cover3) Printed Circuit Design & Fab - December 2007 - The Signal Doctor (Page Cover4)
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.