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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
07 Aug 2006
TL;DR: In this article, the authors present key technologies developed at Georgia Tech PRC for manufactureable and scaleable high performance waveguides on packages or on printed circuit boards (PCBs).
Abstract: We present key technologies developed at Georgia Tech PRC for manufactureable and scaleable high performance waveguides on packages or on printed circuit boards (PCBs). The rough and irregular topographic surface is the first challenge when waveguides are implanted onto a high-density interconnects (HDI) board. Optical buffer layer technology is developed to modify the rough and irregular topography of PCB to a surface with less than 5 nanometer smoothness, which is required for making high quality waveguides, waveguide-based devices and micro optical components. Defects such as particle contaminations, mechanical scratches and damages, and debris etc. process related problem will be a big challenge for manufacturability of volume production for the optoelectronics industry. As a solution, a novel Cap-Clad technology has been developed to make defect-free or defect-less waveguides and high definition optical devices. This technology allows us to make high quality waveguides at a low cost package or PCB environment. Fabrication of other optical components such as 45 degree micro-mirrors and micro-lenses is also discussed and demonstrated in this paper. In the end, the thermal mechanical and optical reliability issues are studied by experiments.

1 citations

Proceedings ArticleDOI
18 May 1997
TL;DR: The Packaging Research Center (PRC) as mentioned in this paper views research and education being equally important in addressing the competitiveness need in electronic packaging in the next decade, which involves two critical items: development of next generation of technologies; and development of human resources, by means of globallycompetitive education to apply the technologies to the global market.
Abstract: The Packaging Research Center (PRC), funded by NSF as one of its engineering centers in the US, views research and education being equally important in addressing the competitiveness need in electronic packaging in the next decade. The strategy to achieve this competitiveness goal involves two critical items: (1) development of next generation of technologies; and (2) development of human resources, by means of globally-competitive education to apply the technologies to the global market. The PRC views that four major education challenges must be addressed in order to meet the above need. These are: (1) system-level education. This is currently missing and includes technologies, manufacturing, business economics and management, global markets and foreign culture; (2) cross-discipline education: current university education is highly discipline-oriented, whereas electronic products are highly cross-disciplinary; (3) industry education: industry engineers are immersed in current, short term technologies and generally are not addressing the next generation needs; and (4) undergrad and pre-college education. To address the above challenge, an education strategy has been developed which consists of educational programs grouped into six strategic major categories: (1) undergraduate, (2) graduate; (3) under-represented outreach; (4) industry engineers; (5) national education; and (6) global education. This paper reviews all of these programs.

1 citations

Patent
30 Aug 2012
TL;DR: In this article, a Chip/Substrat-Verbindungsanordnungen with feinem Abstand and Verfahren zum Herstellen and Verwenden der Anordnings vor.
Abstract: Die verschiedenen Ausfuhrungsformen der vorliegenden Erfindung sehen Chip/Substrat-Verbindungsanordnungen mit feinem Abstand sowie Verfahren zum Herstellen und Verwenden der Anordnungen vor. Die Anordnungen umfassen im Allgemeinen einen Halbleiter mit einem Die-Pad und einem Bump, der darauf angeordnet ist, und ein Substrat mit einem darauf angeordneten Substratpad. Der Bump ist so konfiguriert, dass er mindestens einen Teil des Halbleiters mit mindestens einem Teil des Substrats elektrisch verbindet, wenn der Bump mit dem Substratpad kontaktiert wird. Wenn ferner der Bump mit dem Substratpad kontaktiert wird, werden mindestens ein Teil des Bumps und mindestens ein Teil des Substratpads verformt, um dazwischen eine nichtmetallurgische Verbindung zu erzeugen.

1 citations

Proceedings ArticleDOI
27 May 2008
TL;DR: In this article, the authors present a fast, non-destructive, sensitive, and real-time technique for detailed investigation of the propagation properties of planar optical waveguides and lightwave circuits.
Abstract: Optical polymer waveguide is a key passive component for the optical interconnection. Design, fabrication, and characterization of high performance waveguides have critical importance for the success of optoelectronic integration. In addition, defect effect, coupling, leakages and cross talk etc. are big concerns for the lightwave circuits. We present here a fast, non-destructive, sensitive, and real-time technique for detailed investigation of the propagation properties of planar optical waveguides and lightwave circuits. We use this technique to measure low loss polymer waveguides on printed circuit board (PCB) substrates and have measured the propagation loss of 0.065 dB/cm at 850 nm and 0.046 dB/cm at 980 nm. To the best of our knowledge, these are among the lowest loss data reported for polymer waveguides on PCB substrates to date. A high sensitive CCD camera with a built-in integration function is utilized to observe the light streak in two dimensions through a two lens imaging system. A few seconds to a few ten seconds is required for a complete measurement, compared to several hours for the sliding prism method and even longer for time cutback method. This technique can be used to evaluate not only the overall performance of a waveguide but also the local waveguide performance and the in-situ propagation properties (i.e., defect effect, bending effect, coupling and leakages, etc.). It can be extended to monitor the process of waveguide fabrication and alignment control during the assembly for the lightwave circuit integration.

1 citations

Journal ArticleDOI
TL;DR: In this paper , the major lithography techniques for package redistribution layer (RDL) fabrication for panel level 2 are surveyed, including contact aligners, projection aligners/steppers, laser direct writing (LDW), and laser ablation.
Abstract: This article analyzes the lithography design rules in package foundry and wafer foundry and reviews the major lithography techniques for package redistribution layer (RDL) fabrication for panel level 2.5-D/3-D interposers, fan-out packages, and heterogeneous integration. The techniques surveyed in this article are contact aligners, projection aligners/steppers, laser direct writing (LDW), and laser ablation, capable of resolving routing line and space (L/S) of 0.8– $1.5 \mu \text{m}$ with aspect ratio (AR) $\le 5$ and creating microvia with a diameter of 1.5– $2.0 \mu \text{m}$ at via pitch $\le 5 \mu \text{m}$ . The biggest challenge of advanced packaging is scaling the critical dimensions (CDs) on the package to keep up with the pace of scaling of the bump pitch. In addition, there is a critical need for patterning fine lines-and-spaces with high AR to have low resistance traces. These high AR ultra-fine lines and ultra-fine pitch vias are crucial for meeting the needs of high-bandwidth die-to-die interconnections at high input–output (I/O) densities. All these challenges are mainly driven by lithography. With the development of advanced photoresists (PRs), the resolution factor $K_{1}$ in projection lithography reduces from 0.66 to 0.39, improving the resolution by 40% without the negative impacts on the depth-of-focus (DOF). This article also discusses the specific lithography challenges associated with the topography of multi-layer RDL as well as their impacts on the fabrication of fine features. The fine pitch microvias can be a solution for scaling the I/O pitch down to 5– $10 \mu \text{m}$ as a bumpless way to connect copper pads of known-good-dies to known-good-substrates in fan-out packages.

1 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