CircuiTree - July 2008 - (Page 28)

Toward a PCB Production Floor Metric for Go/No Go Testing of Lossy High-Speed Transmission Lines RIE ﬁgure implies that a measurement taken with one TDR under certain conditions cannot currently be directly compared to another instrument or location around the world without reference to an independent loss standard. Provision of a uniform loss standard is key to the successful adoption of a test metric where worldwide correlation and acceptance of measurements have to be made. Such is the case in the impedance world where air conductor co-axial transmission lines (airlines) are universally accepted as such a standard. – Vias are acceptable; back-drilling (or similar mitigation technique) is not required. • The frequencies of interest are limited to 1.4 GHz or a limit commensurate with high reliability and repeatability. For material differentiation stripline gives better results than microstrip; thus it is suggested that an embedded stripline coupon be employed as the test vehicle even if this structure does not represent those used on the board. This recommendation requires a conceptual shift from conventional impedance testing where the test trace is designed to be a typical board trace. The RIE test proposed here does not replace conventional impedance control techniques that are currently in use. A suitable standard for loss and cross test equipment calibration is key and will need to be established before this new measurement technique can gain widespread trust throughout the industry. ■ References 1. Mellitz, R., Ballou, T., and Pytel, S. G., “Low Cost Energy Based TDR Loss Method for PWB Manufacturers,” IPC Works 2005 in the D-24b Committee Meeting, Las Vegas, 2005. 2. IPC Test Methods, IPC-TM-650 2.5.5.12 rev 0.5, Nov. 2007. 3. Loyer, J., Kunze, R., and Ye, X., “Fiber Weave Effect: Practical Impact Analysis and Mitigation,” Proceedings of DesignCon 2007. 4. Wadell, B. C., Transmission Line Design Handbook, Artech House, 1991 5. Si9000e, PCB Transmission Line Design System, www.polarinstruments.com, 2005. 6. Bogatin, E., Signal Integrity Simpliﬁed, Prentice Hall, 2004. 7. Johnson, H., and Graham, M., High-Speed Signal Propagation, Prentice Hall, 2003. 8. Staniforth, J. A., and Gaudion, M., “Impedance Modelling on Multiple Dielectric Builds,” 2004. This article was awarded U.S. Best Paper at the 2008 IPC Printed Circuits Expo®, APEX® and the Designers Summit. It is reprinted here with permission from IPC. Conclusion and Recommendations RIE with a 250 ps reﬂected risetime appears suitable for discerning signiﬁcant differences in material loss properties, provided: • Proper coupon design is incorporated into the panel design. – Traces must be at least 200 mm (8 in) long and 300 mm (12 in) length is desired for higher precision; – Serpentine routing must have adequate spacing between legs of the serpentine; and Brandon Gore is signal integrity engineer, Richard Mellitz is principle engineer, and Jeff Loyer is senior signal integrity engineer, Intel Corporation. Martyn Gaudion is sales and marketing director and Jean Burnikell and Paul Carré are design engineers, Polar Instruments. Email: martyn.gaudion@polarinstruments.com Are You Getting Weekly? Our weekly e-Newsletter recaps the week in the electronics industry and provides links to FREE educational resources you won’t ﬁnd anywhere else: Live and on demand webinars; Technology Tip audio podcasts; Video presentations; and Web-only articles. Don’t miss another edition. Sign up today at www.circuitree.com/enews. 28 July 2008 • circuitree.com http://www.polarinstruments.com http://www.polarinstruments.com http://www.circuitree.com/enews http://circuitree.com

Table of Contents Feed for the Digital Edition of CircuiTree - July 2008

CircuiTree - July 2008 Contents My Line Industry Review Tech Talk Flexible Thinking Toward a PCB Production Floor Metric for Go/No Go Testing of Lossy High-Speed Transmission Lines Intelligent Design 20-Year Retrospective Ask the Flexperts Environmentally Speaking BPA Growth Curves Considering Design Variants to Maximize Process Efficiency Market Outlook Technical Product Spotlights Classified Ads Upcoming Events Ad Index

CircuiTree - July 2008

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