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 …

I and i

Shape-memory polymers

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.

http://www.nanoscience.gatech.edu/zlwang/paper/2008/08_nat_1.pdf

Microfibre–nanowire hybrid structure for energy scavenging

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

http://www.nanoscience.gatech.edu/zlwang/paper/2010/10_NN_01.pdf

Self-powered nanowire devices.

Fundamentals, processes and applications of high-permittivity polymer–matrix composites

Two new 3D chip stacking technologies, WOB (wire-on-bumps) and BOF (bump-on-flex), are proposed and demonstrated with their prototypes. The WOB and BOF technologies are to stack especially memory chips and connect peripheral bumps on the chips vertically by metal wires and by flex-circuit, respectively. These new 3D chip stacking concepts have several advantages over conventional technologies, such as a lower cost than Si through-via process, unlimited number of stacked chips at a smaller package volume and a faster signal speed than wire bonding method. In this paper, the first demonstrations of the prototypes are described by emphasizing their assembly process and thermo-mechanical modeling. Thermal cycle (TC) test was also performed and some of the TC test results were reported.

New 3D chip stacking SIP technology by wire-on-bump (WOB) and bump-on-flex (BOF)

A major technological break-through was achieved with the design and development of the ES9000 glass-ceramic/copper substrate. Since then many innovations have been made to enhance the packaging technology to meet the demand of high end machines including supercomputer applications. Two technology alternatives are discussed in this paper. Both are aimed at achieving high density, yet they differ quite a bit in their applications. Various aspects of the packaging technology are described here. >

Overview of IBM glass ceramic packaging technology

This paper presents the design and demonstration of a glass package that emulates a 400 Gbps optical transceiver module. The co-design methodology ensures that requirements for optical, electrical, and thermal interconnects are met. It terms of optics, the integrated turning structure demonstrated last year is refined to reduce coupling loss to <3 dB without adding significant process complexity. 28 Gbps high speed electrical interconnects are fabricated directly on glass for insertion loss < 0.1 dB/mm. Thermal management is enabled by the use of thermal vias, which can modify the equivalent thermal conductivity of glass substrate to provide local heat sinking capability. The integrated design is fabricated utilizing a panel scalable process flow developed by the authors with shared steps. Initial characterization results confirms the electrical performance and the quality of optical turning structures.

Co-Design and Demonstration of a Fully Integrated Optical Transceiver Package Featuring Optical, Electrical, and Thermal Interconnects in Glass Substrate

In this paper, the first demonstration of a novel-concept for an ultra-high density and low-cost, non-solder based interconnection technology, which can be applied for miniaturized board-to-board (BTB) as well as 2nd level package-to-system board interconnections, is reported. This is an array type, dry-fit interconnection technology that is modeled, simulated, designed and fabricated. Such a technology is expected to have many applications in small consumer systems such as smart mobile and wearable electronics. This paper presents three key innovations. The first innovation is the introduction of non-solder based, dry-fit interconnection concept. The second innovation is the demonstration of the reduced interconnection height of 0.45 mm, compared to a typical 0.7∼1.0 mm mating height in most miniaturized BTB connectors in the market [1]. This thin mating height is one of the important features in portable electronics applications [2]. The third innovation is in the manufacturing processes. Unlike conventional BTB connectors, simplified and standard manufacturing processes were applied to build this innovative interconnection structure.

A novel non-solder based board-to-board interconnection technology for smart mobile and wearable electronics

This paper presents the first demonstration of fine pitch embedded trench RDL on glass substrates using a new family of ultra-high resolution dry film photo-sensitive polymer dielectrics and a new large area panel scale lithography tool. The specific research targets are to demonstrate multilayer RDL scaling to 1um lines and vias at >200 I/Os per mm of die edge for 2.5D interposers and high density fan-out packages.

Rao Tummala

Papers

New 3D chip stacking SIP technology by wire-on-bump (WOB) and bump-on-flex (BOF)

Overview of IBM glass ceramic packaging technology

Co-Design and Demonstration of a Fully Integrated Optical Transceiver Package Featuring Optical, Electrical, and Thermal Interconnects in Glass Substrate

A novel non-solder based board-to-board interconnection technology for smart mobile and wearable electronics

Demonstration of Embedded Cu Trench RDL using Panel Scale Lithography and Photosensitive Dry Film Polymer Dielectrics