Rao Tummala

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.

Chip-last embedded interconnect structures

Abstract: The various embodiments of the present invention provide a novel chip-last embedded structure, wherein an IC is embedded within a one to two metal layer substrate. The various embodiments of the present invention are comparable to other two-dimensional and three-dimensional WLFO packages of the prior art as the embodiments have similar package thicknesses and X-Y form factors, short interconnect lengths, fine-pitch interconnects to chip I/Os, a reduced layer count for re-distribution of chip I/O pads to ball grid arrays (BGA) or land grid arrays (LGA), and improved thermal management options.

CPW high Q inductors on organic substrates

Abstract: The development of integrated passive components suitable for integration with printed wiring boards is relatively recent. This integration is required since in most mixed signal designs, off-passive components take up more real estate on the boards than the analog and digital signal processing units. Besides utilizing real estate on board, embedded passives on organic laminates significantly reduce cost and if optimized have less parasitics compared to discrete passive components. This paper discusses the design of high Q coplanar waveguide (CPW) planar inductors on laminates. The reason for choosing a CPW type layout is the ease in adding shunt elements and series elements compared to stripline and microstrip configurations. A max Q factor of 85 at 5.2 GHz was obtained for a 1.85 nH CPW type inductor. Several other inductors with similar performances were studied. The paper also presents a method to model the CPW type inductors. This approach allows designers to include metal-to-dielectric interface roughness, non-uniform signal line profiles and frequency dependent parameters such as the dielectric constant of materials.

Magnetic devices utilizing nanocomposite films layered with adhesives

Abstract: Exemplary embodiments provide a nanomagnetic structure and method of making the same, comprising a device substrate, a plurality of nanomagnetic composite layers disposed on the device substrate, wherein an adhesive layer is interposed between each of the plurality of nanomagnetic composite layers. Metal windings are integrated within the plurality of nanomagnetic composite layers to form an inductor core, wherein the nanomagnetic structure has a thickness ranging from about 5 to about 100 microns.

Embedded Trench Redistribution Layers (RDL) by Excimer Laser Ablation and Surface Planer Processes

Abstract: This paper reports the demonstration of 2-5 µm embedded trench formation in dry film polymer dielectrics such as Ajinomoto build-up film (ABF) and Polyimide without using chemical mechanical polishing (CMP) process. The trenches in these dielectrics were formed by excimer laser ablation, followed by metallization of trenches by copper plating processes and overburden removal with surface planer tool. The materials and processes integrated in this work are scalable to large panel fabrication at much higher throughput, for interposers and high density fan-out packaging at lower cost and higher performance than silicon interposers.

I and i

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 …

Microfibre–nanowire hybrid structure for energy scavenging

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.

Self-powered nanowire devices.

Abstract: The lateral and vertical integration of ZnO piezoelectric nanowires allows for voltage and power outputs sufficient to power nanowire-based sensors.