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Author

Rao Tummala

Other affiliations: Qualcomm, IBM, AVX Corporation  ...read more
Bio: Rao Tummala is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Interposer & Capacitor. The author has an hindex of 43, co-authored 623 publications receiving 11663 citations. Previous affiliations of Rao Tummala include Qualcomm & IBM.


Papers
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Proceedings ArticleDOI
27 May 2014
TL;DR: In this paper, the first demonstration of a high-throughput die-to-panel assembly technology to form Cu interconnections without solder at temperatures below 200°C is presented.
Abstract: This paper presents the first demonstration of a high-throughput die-to-panel assembly technology to form Cu interconnections without solder at temperatures below 200°C. This interconnection technology, previously established with individual single-chip packages on both organic and glass substrates, at pitches down to 30μm, is brought up to a significant manufacturable level by two major innovations: 1) ultra-fast thermocompression bonding (TCB) process with pre-applied polymer, in air, and without any prior surface activation; 2) die-to-panel assembly process with heating from die side exclusively for reduced substrate warpage. The initial proof of concept reported in this paper consists of assembly of 15 silicon dies with Cu bumps at 100 μm pitch, on a 3” × 5” organic substrate, by sequential TCB at 210°C for 3 seconds, and 190°C for 10 seconds. X-ray analysis, C-SAM imaging, cross-section observation with optical microscopy and SEM, and electrical yield characterization indicate the formation of strong metallurgical interconnections. This pioneering technology addresses many manufacturability challenges presently hindering the technology-transfer of direct Cu-Cu bonding, the “holy grail” in the semiconductor industry, by offering a potentially low-cost, high-throughput solution, compatible with industry-standard assembly lines. Scalable to ultra-fine pitches onto low-CTE glass, silicon or organic packages, it has the potential to become a major enabler for the next two or more decades.

9 citations

Journal ArticleDOI
TL;DR: The proposed EBG structure successfully and efficiently suppressed the power/ground noise coupling and improved the eye diagram of the TGV channel and embedded thin alumina film in the proposed GI-EBG structure and achieved even broader power/Ground noise suppression between 2.1 and 14.7 GHz.
Abstract: In this paper, we propose glass-interposer (GI) electromagnetic bandgap (EBG) structure with defected ground plane (DGP) for efficient and broadband suppression of power/ground noise coupling. We designed, fabricated, measured, and analyzed a GI-EBG structure with DGP for the first time. The proposed GI-EBG structure with DGP is thoroughly analyzed using the dispersion characteristics and estimated stopband edges, $f_{L}$ and $f_{U}$ . We experimentally verified that the proposed GI-EBG structure with DGP achieved power/ground noise isolation bandgap (below −30 dB) between $f_{L}$ of 5.7 GHz and $f_{U}$ of 11 GHz. Estimation of $f_{L}$ and $f_{U}$ using dispersion analysis, full 3-D electromagnetic (EM) simulation results, and measurement results achieved good correlation. Effectiveness of the proposed GI-EBG structure with DGP on suppression of the power/ground noise coupling to high-speed through glass via (TGV) channel is verified with 3-D EM simulation. As a result, the proposed EBG structure successfully and efficiently suppressed the power/ground noise coupling and improved the eye diagram of the TGV channel. Lastly, we embedded thin alumina film in the proposed EBG structure and achieved even broader power/ground noise suppression between 2.1 and 14.7 GHz.

9 citations

Patent
10 Aug 1977
TL;DR: In this paper, the lifetime of multiple capillary nozzle assemblies embedded in a glass mass, of a multiple nozzle ink-jet printer, can be increased and the thermal and mechanical compatibility of the resulting package enhanced by fabrication of the nozzles from glass compositions comprised of SiO 2, ZrO 2, Na 2 O, K 2 O and MgO.
Abstract: The lifetime of multiple capillary nozzle assemblies embedded in a glass mass, of a multiple nozzle ink-jet printer, can be increased and the thermal and mechanical compatibility of the resulting package enhanced by fabrication of the nozzles from glass compositions comprised of SiO 2 , ZrO 2 , Na 2 O, K 2 O and MgO. Inclusion of ZrO 2 as well as minor amounts of BaO, MgO, CaO, and Al 2 O 3 enhances the alkali resistance of the glass nozzles. Also, the high SiO 2 content of the glasses combined with the presence of ZrO 2 , MgO, CaO, and Al 2 O 3 imparts an acid resistance to the nozzles.

9 citations

Proceedings ArticleDOI
01 May 2016
TL;DR: In this article, the authors present the first demonstration of a novel fiber coupling structure that enables low-loss and low-cost fiber coupling in an ultra-miniaturized 3D glass photonic interposer.
Abstract: This paper presents the first demonstration of a novel fiber coupling structure that enables low-loss and low-cost fiber coupling in an ultra-miniaturized 3D glass photonic interposer. The novel 3D coupling structure consists of a tapered optical waveguide with an integrated lensed turning mirror on one end and a cylindrical lens on the other end, in a 150 im glass substrate. The lens waveguide and turning mirror provide coupling loss of

9 citations

Proceedings ArticleDOI
01 May 2016
TL;DR: In this paper, an integrated radio frequency (RF) front-end module (FEM) with precision matching circuits in ultra-miniaturized glass substrates for LTE applications is presented.
Abstract: This paper demonstrates, for the first time, an integrated radio frequency (RF) front-end module (FEM) with precision matching circuits in ultra-miniaturized glass substrates for LTE applications. Through full-wave electromagnetic (EM) simulations, electrical performance of these glass-based long term evolution (LTE) packages is compared with traditional RF modules with surface mount devices (SMDs), and organic laminates with embedded passives and actives. RF front-end modules with 3D or double-side thinfilm passive components on glass-based substrates are fabricated and characterized to correlate their performance with EM simulations.

9 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: Shape-memory polymers as discussed by the authors are an emerging class of active polymers that can change their shape in a predefined way from shape A to shape B when exposed to an appropriate stimulus.

1,575 citations

Journal ArticleDOI
14 Feb 2008-Nature
TL;DR: This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics and presents a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres.
Abstract: Nanodevices don't use much energy, and if the little they do need can be scavenged from vibrations associated with foot steps, heart beats, noises and air flow, a whole range of applications in personal electronics, sensing and defence technologies opens up. Energy gathering of that type requires a technology that works at low frequency range (below 10 Hz), ideally based on soft, flexible materials. A group working at Georgia Institute of Technology has now come up with a system that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing their associated nanowires together, mechanical energy is converted into electricity via a coupled piezoelectric-semiconductor process. This work shows a potential method for creating fabrics which scavenge energy from light winds and body movement. A self-powering nanosystem that harvests its operating energy from the environment is an attractive proposition for sensing, personal electronics and defence technologies1. This is in principle feasible for nanodevices owing to their extremely low power consumption2,3,4,5. Solar, thermal and mechanical (wind, friction, body movement) energies are common and may be scavenged from the environment, but the type of energy source to be chosen has to be decided on the basis of specific applications. Military sensing/surveillance node placement, for example, may involve difficult-to-reach locations, may need to be hidden, and may be in environments that are dusty, rainy, dark and/or in deep forest. In a moving vehicle or aeroplane, harvesting energy from a rotating tyre or wind blowing on the body is a possible choice to power wireless devices implanted in the surface of the vehicle. Nanowire nanogenerators built on hard substrates were demonstrated for harvesting local mechanical energy produced by high-frequency ultrasonic waves6,7. To harvest the energy from vibration or disturbance originating from footsteps, heartbeats, ambient noise and air flow, it is important to explore innovative technologies that work at low frequencies (such as <10 Hz) and that are based on flexible soft materials. Here we present a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing the nanowires rooted on them with respect to each other, mechanical energy is converted into electricity owing to a coupled piezoelectric–semiconductor process8,9. This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics.

1,473 citations

Journal ArticleDOI
TL;DR: This work demonstrates the vertical and lateral integration of ZnO nanowires into arrays that are capable of producing sufficient power to operate real devices and uses the vertically integrated nanogenerator to power a nanowire pH sensor and a Nanowire UV sensor, thus demonstrating a self-powered system composed entirely of nanowiring.
Abstract: The lateral and vertical integration of ZnO piezoelectric nanowires allows for voltage and power outputs sufficient to power nanowire-based sensors.

1,465 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on the important role and challenges of high-k polymer-matrix composites (PMC) in new technologies and discuss potential applications of highk PMC.

1,412 citations