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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
01 May 2017
TL;DR: In this paper, the performance of the inductive link is enhanced with innovative high-permeability and low-loss magnetic films for improved inductive coupling between the receiver and the transmitter.
Abstract: This paper describes advances in integrated ultra-thin wireless power module components for Internet of Things (IoT) and wireless sensor applications. A typical wireless module integrates both an inductive link for wireless power transfer, and supercapacitor as a storage element. The performance of the inductive link is enhanced with innovative high-permeability and low-loss magnetic films for improved inductive coupling between the receiver and the transmitter. Up to 4X enhancement in power transfer efficiency is demonstrated with the innovative magnetic films. Energy storage is achieved through a thinfilm micro fabricated supercapacitor layer with interdigitated graphene-based planar electrodes and solid-state electrolytes for easier integration. The component properties demonstrated through this work are projected to achieve high power levels with ultra-thin form-factors.
01 Jan 2015
TL;DR: In this paper, a set of no-flow snap-cure materials with high thermal stability, beyond existing conductive films or pastes, was developed in synergy with tools and processes for compatibility with advanced substrate technologies.
Abstract: The needs for higher speed and bandwidth at low power for portable and high-performance applications has been driving recent innovations in packaging technologies with new substrate platforms with finer lithographic capability and dimensional stability, such as ultra-thin glass, to enable off- chip interconnections pitch scaling, down to 30µm. Copper pillar flip-chip thermocompression bonding (TCB) has subsequently become a pervasive technology in the past decade, and is now considered as the next interconnection and assembly node for smart mobile and high-performance systems. However, additional innovations are needed to achieve high-throughput thermocompression bonding on fragile and thin glass, with short cycle times and process conditions within HVM (high-volume manufacturing) tool capability. These include material advances in surface finishes and pre-applied underfill materials with built-in flux, along with a unique co-development strategy to provide high- speed solutions with optimized TCB profiles that consider the dynamic thermal behavior of high-density glass substrates, underfill curing kinetics, as well as tool compatibility. These innovations are the key focus of this paper. Finite element heat transfer and thermomechanical modeling were carried out to emulate assembly processes and compare the behavior of glass substrates to that of current technologies. Residual stresses created during the cool-down phase were extracted to help define process windows for stress management in interconnections, by fine control of intermetallics (IMC) formation. Emerging surface finish chemistries compatible with high-density wiring with sub- 10m spacings, such as OSP or EPAG (electroless Pd, autocatalytic Au) finish, were also evaluated for their effect on the formed IMC systems. A new set of no-flow snap-cure underfill materials with high thermal stability, beyond existing conductive films or pastes, was developed in synergy with tools and processes for compatibility with advanced substrate technologies. Model predictions were validated with assembly trials on ultra-thin glass and organic substrates with 100µm thin cores. Design guidelines for bonding tools, materials and processes were finally derived, for high-speed thermocompression bonding, customized to the performance, reliability and cost needs of next-generation mobile and high- performance systems.
Patent
23 May 2019
TL;DR: In this paper, a planar inductor consisting of a substrate, a first magnetic layer, a conductive coil, and a second magnetic layer is presented, which can be disposed on at least a portion of the substrate.
Abstract: An exemplary embodiment of the present invention provides a planar inductor comprising a substrate, a first magnetic layer, a conductive coil, and a second magnetic layer. The first magnetic layer can be disposed on at least a portion of the substrate. The conductive coil can be disposed on a first portion of the first magnetic layer. The second magnetic layer can be disposed on a second portion of the first magnetic layer and on at least a portion of the conductive coil.

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