IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, VOL. 5, NO. 3, MARCH 2015
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High-Performance and High-Data-Rate Quasi-Coaxial LTCC Vertical Interconnect Transitions for Multichip Modules and System-on-Package Applications Emmanuel Decrossas, Member, IEEE, Michael D. Glover, Member, IEEE, Kaoru Porter, Tom Cannon, Thomas Stegeman, Student Member, IEEE, Nicholas Allen-McCormack, Michael C. Hamilton, Senior Member, IEEE, and H. Alan Mantooth, Fellow, IEEE
Abstract— A new design of stripline transition structures and flip-chip interconnects for high-speed digital communication systems implemented in low-temperature cofired ceramic (LTCC) substrates is presented. Simplified fabrication, suitability for LTCC machining, suitability for integration with other components, and connection to integrated stripline or microstrip interconnects for LTCC multichip modules and system on package make this approach well suited for miniaturized, advanced broadband, and highly integrated multichip ceramic modules. The transition provides excellent signal integrity at high-speed digital data rates up to 28 Gbits/s. Full-wave simulations and experimental results demonstrate a cost-effective solution for a wide frequency range from dc to 30 GHz and beyond. Signal integrity and high-speed digital data rate performances are verified through eye diagram and time-domain reflectometry and time-domain transmissometry measurements over a 10-cm long stripline. Index Terms— Full tape thickness feature, low-temperature cofired ceramic (LTCC) interconnect, multichip module (MCM), quasi-coaxial vertical transition, signal integrity, system on package.
I. I NTRODUCTION PPLICATIONS in the field of high-speed digital electronics have been driving the trends of future communication equipment. Cost-effective technologies for multichip modules are necessary to realize high- frequency
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Manuscript received May 14, 2014; revised September 8, 2014 and January 14, 2015; accepted January 16, 2015. Date of publication February 2, 2015; date of current version March 5, 2015. This work was supported by Auburn University, Auburn, AL, USA. Recommended for publication by Associate Editor T. J. Schoepf upon evaluation of reviewers’ comments. E. Decrossas was with the High Density Electronics Center, University of Arkansas, Fayetteville, AR 72701 USA. He is now with the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125 USA (e-mail:
[email protected]). M. D. Glover, K. Porter, and T. Cannon are with the High Density Electronics Center, University of Arkansas, Fayetteville, AR 72701 USA (e-mail:
[email protected];
[email protected];
[email protected]). T. Stegeman, N. Allen-McCormack, and M. C. Hamilton are with the Department of Electrical and Computer Engineering, Auburn University, Auburn, AL 36849 USA (e-mail:
[email protected];
[email protected];
[email protected]). H. A. Mantooth is with the Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701 USA (e-mail:
[email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TCPMT.2015.2394234
communication systems. Low-temperature cofired ceramic (LTCC) substrates offer promising solutions because of the combination of multilayered structures, flexible fabrication techniques, advanced passive device integration of radio frequency (RF)/microwave components, and low losses up to millimeter-wave frequencies. Novel trends in LTCC processing and packaging allow highly integrated and versatile components [1]. In addition, manufacturer efforts to produce high-performance LTCC tape materials benefit the development of new designs for future densely integrated electronic systems. Previous vertical transition structures include microstrip-to-stripline transitions where the signal lines are connected through a via. However, to compensate for the large capacitive effect occurring at the transition, it is necessary to lower the ground of the stripline in the transition region [2] or to use air cavities [3] to reduce the impedance mismatch. Schm¨uckle et al. [2] have measured a reflection coefficient below −10 dB from 10 to 30 GHz. Using an air cavity, Lee [3] was able to obtain a reflection coefficient below −10 dB from 55 to 60 GHz. It should be noted that a reflection coefficient level below −10 dB is commonly accepted, i.e.,
