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Hitachi

Corporate InformationResearch & Development

August 5, 2015

Report from Presenter

The 2015 IEEE 4th Asia-Pacific Conference on Antennas and Propagation was held in Bali Island, Indonesia on June 30 - July 3, 2015. Researchers from various areas such as China, Singapore, Japan, India, USA and Europe attended this conference and discussed antenna technologies, electromagnetic analysis method and its applications animatedly.

Research and Development Group, Hitachi, Ltd., made 2 oral presentations and this report shows one of them. The title of the presentation is "Ground planes resonance suppression technique of glass interposer using high-resistivity via holes for high-speed serial links".

Growing use of smart devices continues to drive mobile communications traffic growth at an annual rate of 140%. This trend calls for improvements at commensurate rates in communication performance and computing performance. To achieve such improvements, systems in package (SiPs) using interposers have been proposed (Fig. 1). Due to the very fine pitch of the signal lines on interposers, total data rates between logic IC and optical ICs or between logic IC and memory chips will increase dramatically.


Fig. 1 Example of system in package
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Fig. 2 Plane resonances in glass interposer
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Glass interposers have been proposed as material for interposers because of low production cost and low dielectric loss. Low dielectric loss of glass core, however, leads to an issue. Ground planes on both sides of glass core behave as cavity resonators, and the insertion loss of signal lines through glass cores degrades near resonance frequencies (Fig. 2). In this study, a ground plane resonance suppression technique for glass interposers is proposed. In this technique, resistive vias made by high resistivity material are introduced at anti-nodes of resonance voltage in glass core (Fig. 3). The resistive vias consume the energy of resonance and suppress the resonance effectively. In order to investigate the effects of resistive vias, we evaluated the Q factor of the resonance by electromagnetic field solver. Just a few resistive vias suppress effectively the resonance over several modes (Fig. 4). This result implies this technique improve the electrical characteristics of glass interposer. We will continue to develop performance improvement techniques for future ICT systems.


Fig. 3 The Proposed resonance suppression
structure

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Fig. 4 Damping effects of resistive vias
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(By TOYAMA Masahiro)

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