IBM® uses printed-circuit board materials in its servers that are incompletely or erroneously characterized by typical fabricators. This problem results in IBM's having to perform extensive recharacterization in order to extract the frequency-dependent properties of such structures so that accurate predictions of system performance can be made. This toolkit can be used to perform accurate extraction of broadband material properties and it thus reduces or eliminates design errors prior to product manufacturing. In addition, this technology is suitable for sharing with university educators for the purpose of training future engineers to perform complete material characterization of representative, multilayer wiring structures. Such broadband, causal extraction techniques cannot be obtained with other network analyzer-based techniques that are routinely employed in the industry. Broadband properties are essential for generating accurate models for digital signal simulations that have random-pattern data strings. Enforcement of causality is essential for >10GHz bandwidth signals.

The two components of this toolkit are CZ2D and Gamma-Z. CZ2D is a two-dimensional, electromagnetic modeling tool that has built-in facilities to guarantee causal results over wide frequency range. Gamma-Z provides the signal processing capability of the propagated short-pulses launched on very simple test wiring.

CZ2D is a two-dimensional, "method-of-moment"-based field solver that calculates resistance (R), inductance (L), capacitance (C), and conductance (G) per unit length for any transmission line structure, such as printed circuit board interconnections. Frequency-dependent calculation can be made that is guaranteed causal for both R(f)L(f) and C(f)G(f) and for inhomogeneous dielectrics.

Gamma-Z is a broadband, lossy transmission line tool that accepts two digitized short pulses that are propagated on two lengths of identical transmission lines. The tool performs signal processing, rectangular time windowing of end effects, Fourier transformation, and ratioing. From this operation, the propagation constant G (Gamma) and characteristic impedance Zo (Z in Gamma-Z) are obtained. The same elements are also calculated using CZ2D and a starting set of values of the complex permittivity for the material being evaluated. A built-in Debye model in CZ2D guarantees causality of results. By comparing the measured and calculated results and iterating a few times, the broadband complex permittivity is obtained.

The package, which is provided at no charge, includes the executable for CZ2D on Linux Red Hat 9.1 and Gamma-Z for the Windows platform. Manuals are also included, along with some example "run" cases. A graphical user interface (GUI) is additional software that allows the user to put in structure configurations to be solved using the toolkit.

The CZ2D component runs on Linux® Red Hat 9.1, and Gamma-Z runs on Windows®.

How does it work?

A short-pulse propagation technique is used to extract the frequency-dependent material parameters by using signal processing and structure modeling. The requirements for using this software involve standardized pulse generators and sampling oscilloscopes. Gamma-Z software provides the signal processing of the propagated pulses and the results are fitted to modeled results based on CZ2D calculations. A Fourier transformation is performed in order to obtain G (propagation constant) and Zo (characteristic impedance), the two parameters needed for fully analyzing any interconnect, from which the total attenuation is obtained. Iterative fitting and modeling allow extraction of complex permittivity over the range 10 KHz to 50 GHz.

This technique is applicable to representative, multilayer circuit boards, ceramic wiring, cables, or on-chip wiring that are used in digital and communication applications in the semiconductor industry when building typical server systems, and especially the ones targeted for >10GHz clock operation.

Alina Deutsch received B.S. and M.S. degrees in electrical engineering from Columbia University, N.Y., and Syracuse University, N.Y., in 1971 and 1976, respectively. She has been at IBM since 1971 and has worked in several areas, including testing of semiconductor and magnetic bubble memory devices. Ms. Deutsch has designed unique lossy transmission line configurations, and she has developed unique high-frequency high impedance coaxial probes and a novel short-pulse measurement technique for characterization of resistive transmission lines.

Currently, Ms. Deutsch is an IBM research staff member currently working on the design, analysis, and measurement of packaging and VLSI chip interconnections for future digital processor and communication applications. Her work involves the three-dimensional modeling, signal integrity, noise simulation, and testing of of a large range of package lossy transmission lines from printed-circuit boards, cables, and connectors to thin-film wiring on multi-chip modules and on-chip wiring.

Ms. Deutsch is also the manager of the Interconnect and Packaging Analysis project that develops advanced electromagnetic field-solver codes. She has written 45 papers published in refereed technical journals; has given numerous invited and tutorial speeches; holds 15 patents; and has received Outstanding Technical Achievement, Research Division, and S/390 Division Team Awards from IBM in 1990, 1993, 1996, 1999, 2000, 2001, 2002, 2003, 2005, and 2006.

Ms. Deutsch, who is a fellow of the IEEE, co-chaired for four years the IEEE "Topical Meeting on Electrical Performance of Electronic Packaging," served as technical program co-chairman for the "IMAPS Next Generation IC and Package Design Workshop" for three years, co-chaired the CPMT Society "Future Directions in IC and Package Design" workshop for four years, and served as Guest Editor of the IEEE Transactions on Advanced Packaging for five years. She is an associate editor of IEEE Transactions on Components and Packaging Technologies; is a member of Tau Beta Pi and Etta Kappa Nu; served as an elected member of the IEEE Components, Packaging, and Manufacturing Technology Society Board of Governors for 2000-2002; and served as vice-chairman of the CPMT Society TC-12 Technical Committee.