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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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Patent
Jimmie L. Powell1, Rao Tummala1
18 Jun 1980
TL;DR: Alkaline ink-resistant multi-nozzle array for ink jet printers, where a number of glass nozzles are embedded in a glass substance, characterized in that the glass mass used for embedding the nozzleles comprises the following oxides, bu weight % : PbO 45 - 53,5%, Ge O2 0% SiO2 15 - 24,5% Zr O2 4,5%. B2 O3 5 - 12% Mg O 0,5 - 1,5, ZnO 3,5- 4, 5% Ba
Abstract: 1. Alkaline ink-resistant multi-nozzle array for ink jet printers, where a number of glass nozzles are embedded in a glass substance, characterized in that the glass mass used for embedding the nozzles comprises the following oxides, bu weight % : PbO 45 - 53,5% Ge O2 0% SiO2 15 - 24,5% Zr O2 4,5% B2 O3 5 - 12% Mg O 0,5 - 1,5% ZnO 3,5 - 4,5% Ba O 0 - 1,5% Al2 O3 3 - 4% Ti O2 0 - 2% Na2 O 1 - 6,5% Ca O 0,5 - 1,5% CdO 2 - 3% La2 O3 0 - 0,5% Cu2 O 0 - 2%
Proceedings ArticleDOI
01 Jun 2021
Abstract: The ever-increasing demand for high-bandwidth interconnects has given rise to the need for high IO-density package redistribution layers (RDL). This necessitates scaling down RDL critical dimensions as well as microvias. There are numerous challenges pertaining to scaling down microvias below $5\ \mu \mathrm{m}$ diameter. The main challenge is the thermomechanical reliability of vias in polymer dielectrics. Modeling and design for reliability in various polymer dielectrics is the key to achieve mechanical reliability. This paper presents a model for the prediction of micro-via failure. The effects of via geometry such as-via angle and height as well as material properties such as-CTE and elastic modulus on via failure are presented. Furthermore, modeling results are correlated with experimental results to verify the accuracy of the model. Using this model, it was determined that the conventional via geometry reaches an engineering limit at $2 \mu \mathrm{m}$ of via diameter. Below this size, it becomes difficult to achieve reliable vias in polymers as they do not survive 1000 thermal cycles. Based on the modeling studies, a novel method is proposed for enhancement of reliability of vias below the engineering limit of $2\ \mu \mathrm{m}$ .
20 May 2007
TL;DR: In this article, a brief review of work done in the domain of stability of crystalline materials using dopants and their application in nanocrystalline materials is discussed and the importance of both experiment and molecular dynamics simulations is presented.
Abstract: It is well established that nanocrystalline materials have unique mechanical and electrical properties in comparison to their microcrystalline counterparts due to their reduced crystallite or grain size. Loss of these unique properties due to grain growth under the effect of high temperature and stress is a limitation to their use in many applications. Recently it has been proposed to use dopants (alloying elements) to reduce the driving force for grain boundary motion, leading to improved microstructural stability and resistance to deformation. Inclusion of dopants has been shown to alter properties of nanocrystalline materials, although their precise effect on mechanical and electrical properties is still unclear. In this brief review article, work done in the domain of stability of crystalline materials using dopants and their application in nanocrystalline materials is discussed. The importance of both experiment and molecular dynamics simulations is presented.
Proceedings ArticleDOI
01 May 2018
TL;DR: In this paper, a panel-scale fabrication and integration process is developed for aluminum thin-film capacitors with 2.2 µF/cm2 for 30-48 V applications.
Abstract: Aluminum capacitors provide a superior combination of high volumetric density owing to their high-surface area structure and high voltage-stability owing to their paraelectric, natural oxide dielectric. However, these capacitors are currently not compatible with wafer-level packaging or high-temperature environments. In this research, a panel-scale fabrication and integration process is developed for aluminum thin-film capacitors with 2.2 µF/cm2 for 30-48 V applications. The performance of parylene film as a passivation film to extend the operating temperature of conducting-polymer capacitors such as the aluminum-polymer capacitors in this paper is also evaluated. A 700 nm thick passivation film is shown to provide the best combination of hermeticity and thermomechanical stability at high-temperature and high-humidity conditions.
Journal ArticleDOI
TL;DR: In this paper, a four-metal layer RDL buildup required for wide input/output (I/O) routing at 40-μm bump pitch and a two-metal RDL stack fabricated directly on glass for high-speed, off-package signaling are described.
Abstract: This article analyzes redistribution layer (RDL) technologies needed for 2.5-dimensional (2.5-D) die integration on thin glass interposers and developed using low-cost processes. The design, fabrication, and characterization of a four-metal layer RDL buildup required for wide input/output (I/O) routing at 40-μm bump pitch and a two-metal layer RDL buildup fabricated directly on glass for high-speed, off-package signaling are described. Such RDL technologies are targeted at 2.5-D glass interposer packages to achieve up to 1 Tb/s die-to-die bandwidth and off-interposer data rates > 400 Gb/s, driven by consumer demand of online services for mobile devices. Advanced packaging architectures including 2.5-D and 3-D interposers require fine-line lithography beyond the capabilities of current organic package substrates. High electrical loss and high cost are characteristic of silicon interposers fabricated using back-end-of-line (BEOL) processes that can achieve RDL wiring densities required for 2.5-D die integra...

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