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

Method of fabricating electric connection package of glasssceramic*conductor

Novel low CTE-high stiffness organic and inorganic boards were evaluated for flip-chip on board technology without underfill. Standard liquid-liquid thermal shock tests were carried out on test vehicles with different board materials and failure modes were characterized. In-situ warpage and stress measurements were made to analyze the observed failure modes and to set guidelines for optimal board material selection. The effect of interlayer dielectric thickness on the package reliability has also been studied. The reliability test results are in accordance with the inferences from the in-situ warpage and stress measurements and it can be concluded that along with low CTE, high modulus is an inevitable substrate property requirement for flip-chip reliability without underfill in next-generation packages. This paper also presents photostimulated luminescence spectroscopy as a nondestructive and direct technique for the in-situ stress measurement in microsystems and thus a powerful means for reliability assessment.

Reliability assessment of high density multi-layer board assembly using shadow Moire and luminescence spectroscopy

Durch Erhitzen oberhalb 750°C werden in Cu-haltigen Bleiglasern betrachtliche Mengen an Cu+-Ionen erzeugt, die wahrend fortdauernder Erwarmung eine braunen CuzO-Niederschlag im Glas bilden.

Crystallization in Copper‐Containing Solder Glasses

Provided is a stress-relieving, second-level interconnect structure that is low-cost and accommodates thermal coefficient of expansion (TCE) mismatch between low-TCE packages and printed circuit boards (PCBs). The interconnect structure comprises at least a first pad, a supporting pillar, and a solder bump, wherein the first pad and supporting pillar are operative to absorb substantially all plastic strain, thereby enhancing compliance between the two electronic components.

Stress relieving second level interconnect structures and methods of making the same

Embedded systems play a crucial role is achieving very high component density and functions. Embedded actives have been the focus for three most important paradigms in systems integration. The paradigms are system in a package (SIP), system on a package (SOP) and system on a chip (SOC). ITRS road map requires very high component density by the year 2007. Embedded passives play an important role in determining frequency stability and signal integrity. Their stability depends on design, choice of material and process. There are limitations in achieving accurate parameters in the passives. Embedded passives have non reversible function or reworkability. These needs require techniques and process developed to have controlled actives which can change its parameters in a combination of mechanical, electrical and material properties. Flip chips are assembled on substrates enable thermal management. The need to mount several chip in unit area drives assembly process to wafer level chip stacking. There is need for embedded techniques to achieve good process for variable capacitors, resistors and inductors along with embedded flip chips. In this paper, we characterized the performance of a novel embedded variable capacitor fabricated using a polymer dielectric material, with one metal electrode fabricated on a low strength back plane to allow the electrode to flex. Sol-gel process is selected as it is a versatile technology to produce fine powders, fibers, coatings and is expected to yield highly homogeneous thin/thick films. A variable DC current is applied on the piezoelectric material to deform the dielectric, thereby changing the capacitance thus allowing the dielectric to behave as a variable capacitor. The compression effect on the dielectric also causes a thickness variation there by making the already submicron thick dielectric vary in thickness. The thinner dielectric makes it suitable for high frequency capacitance application. By changing the thickness of the dielectric and varying the frequency, the capacitor becomes very suitable to work over a broad range of frequencies and capacitances. The characteristics including material components and construction, dielectric properties and topography at metal-dielectric interfaces are optimized for a wide frequency band width. Attention is given to frequency dependence of the different material properties. Effects of the material characteristics on electrical performance, including capacitance are examined. Finally, processing and fabrication issues are discussed.

http://ieeexplore.ieee.org/iel5/9844/31024/01441999.pdf

Rao Tummala

Papers

Method of fabricating electric connection package of glasssceramic*conductor

Reliability assessment of high density multi-layer board assembly using shadow Moire and luminescence spectroscopy

Crystallization in Copper‐Containing Solder Glasses

Stress relieving second level interconnect structures and methods of making the same

Variable embedded capacitor for active systems packaging