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By definition, a guard trace is a trace routed coplanar between an aggressor line and a victim line. There has always been an argument about whether to use guard traces in high-speed digital and mixed signal applications to reduce the noise coupled from an aggressor transmission line to a victim transmission line.
On one side of the debate, the argument is that the guard trace should be shorted to ground at regular intervals along its length using stitching vias spaced at 1/10 of a wavelength of the highest frequency component of the aggressor’s signal. By doing so, it is believed the guard trace will act as a shield between the aggressor and victim traces.
On the other side, merely separating the victim trace to at least three times the line width from the aggressor is good enough. The reasoning is that crosstalk falls off rapidly with increased spacing anyway, and by adding a guard trace, you will already have at least three times the trace separation to fit it in.
Read the full column here.
Editor's Note: This column originally appeared in the April 2013 issue of The PCB Design Magazine.
Kris Moyer, IPC
In today’s ever-shrinking world of electronics designs, the use of BGA parts with very fine pitch features is becoming more prevalent. As these fine-pitch BGAs continue to increase in complexity and user I/O (number of balls), the difficulty of finding escape routes and fan-out patterns increases. Additionally, with the shrinking of silicon geometry leading to both smaller channel length and increased signal integrity issues, some of the traditional BGA escape routing techniques will require a revisit and/or adjustment to allow for not only successful fan-out, but also successful functioning of the circuitry of the BGA design.
I-Connect007 Editorial Team
I recently spoke with Todd Westerhoff, product marketing manager for signal integrity software tools at Siemens. We discussed a new capability called HyperLynx Apps that offers a new take on traditional signal and power integrity analysis, and how that fits in with the Siemens plan to put SI and PI tools into the hands of more designers early in the design cycle.
To give readers a sample of 'The Printed Circuit Designer’s Guide to... Stackups—The Design within the Design,' by Bill Hargin, we are providing the book's introduction. He writes, "Another book about stackups? If you’re asking this question, I’d like to know the book you’re thinking of, as I was looking for it a few years back. I have a pretty good PCB signal integrity (SI) library, and I’ve only found one chapter on stackup design so far."