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

Integration of passive components offers inherent benefits such as reduced size, density, cost, and improved packaging efficiency and reliability. An integrated RC network requiring relatively large capacitance and resistance was selected as a model for integration of R and C components using low temperalare PWB compatible fabrication processes. Ohmega-Ply resistor/conductor laminates and photodefinable epoxies filled with high K ceramic powders were used as candidate materials for fabrication of embedded resistors and thin film capacitors. In order to reduce in-plane device area, multilayer (currently, two-layer) capacitors were stacked in the thickness direction. Meniscus coating of filled polymer dielectrics over large area (12 in x 12 in) was evaluated for cost and manufacturability advantages. This paper discusses the design, choice of materials, and fabricatilon issues of an integrated RC device. 1. Introlduction The Packaging Research Center at Georgia Tech is in the process of developing low temperalure MCM-L based processes suitable ICR L

https://ieeexplore.ieee.org/iel4/5363/14502/00664473.pdf

MCM-L Compatible Integrated Resistors And Capacitors

Residual Stresses in glass-crystal composites

Advanced substrates or printed circuit boards (PCBs) are an essential part for building the advanced IC packages (BGA, CSP, flip chip and wafer-level package), MCMs, 3D package, system-in-package (SiP), system-on-package (SOP), and all high density microelectronic systems. As processors and memory move towards nanometer-size features and processor clock speeds increase 60% per year, development of next generation system level substrates technology is required to keep pace both the wiring density and high performance requirements. The packaging research center at Georgia Tech has been developing system-on-package (SOP) technology for future high density, high performance systems. This paper introduces three important aspects for future advanced package substrates or PCBs for high density and high performance systems applications. They are (1) ultra-high density wiring technology with ultra fine circuit traces and microvias, including novel non-conformal stacked vias. The ultra high wiring density substrate is critical for the use of fine pitch, high I/O count, flip chip application and. microsystem miniaturization. (2) Integrations of passive components, and (3) integrations of high speed optical interconnects for chip-to-chip data link. This will be the revolutionary advance in future PCBs. We have developed ultra high density wiring technology by a combination of ultra-fine lines and space of 10 /spl mu/m or less and stacked microvias. We have developed optically smooth organic surfaces for optical components integration and have demonstrated a 10 Gbps chip-to-chip data rate on PCBs. The future high density, high performance, microsystems can be realized by the combinations of high density wiring technology and optoelectronics integration. Details of this work are the subject of this paper.

Multifunctional integrated substrate technology for high density SOP packaging

Rapid changes will continue in the trend toward system integration and microminiaturization. System-on-a package (SOP) is a highly integrated packaging solution based on embedding thin film passive and active components in ultra high density build-up substrates. The SOP-substrate provides a platform leading to system multi-functional and microminiaturization which demands additional wiring capability for routing chips and interconnecting embedded components. Fine line photolithography with I-line UV light is the key enabling technology to achieve the required wiring density on substrate at low cost. We have studied the fundamentals of fine image transfer by I-line photolithography based on proximity exposure. The relationship of achievable minimum feature size and gap distance between photo-mask and photo resist was investigated by calculations and experiments. Calculation showed that as fine as 2 mum line and space could be achievable on an 8 mum thick photo resist at gap of zero. While experimental results showed that 6 mum line and space was obtained with gap of zero and 10 mum line and space was obtained at gap of 60 mum. 60 mum is the maximum gap for resolving sub-10 mum line and space by I-line photolithography. Fine line categories for package substrate and related technologies are summarized. Finally we demonstrate a build-up layer having extremely high wiring capability for 100 mum pitch area array flip chip with 3 copper routing lines per pitch and 1,600 bumps per layer for satisfying year 2010 semiconductor roadmap microprocessor requirements.

Fine Line Photolithography and Ultra High Density Package Substrate for Next Generation System-on-Package (SOP)

This paper reports the first demonstration of antenna-in-package and seamless antenna-to-receiver signal transitions on panel-scale processed ultra-thin glass substrates, for high-speed 5G communication standards in the 28 GHz band. To demonstrate the benefits of g 1 ass for 5 G communications, package-integrated antennas with feedlines were modeled and designed on ultra-thin glass substrates laminated with low-loss dielectric thin films for highest bandwidth and efficiency in the mm-wave bands. The measured results for a miniaturized Yagi-Uda antenna, transmission lines, and through-package vias showed superior dimensional stability and good agreement with the simulated values on 100 µm glass substrates. The results showed low interconnect signal losses with a microstrip line loss of 0.108 dB/mm, and a through-package via loss of 0.095 dB/TPV. The Yagi-Uda antenna fabricated on glass substrates showed a center frequency of 28.18 GHz with a fractional bandwidth of 21.1%. The antenna also presented a wide-angle main lobe at the target frequency range implying good coverage of signal transmitting and receiving. The performance of package-integrated antenna, feedlines, through-package vias, and transmission lines on glass substrates was benchmarked in comparison to other 5G substrate technologies such as organic laminate, ceramic-based substrates, or fan-out wafer level packaging.

Rao Tummala

Papers

MCM-L Compatible Integrated Resistors And Capacitors

Residual Stresses in glass-crystal composites

Multifunctional integrated substrate technology for high density SOP packaging

Fine Line Photolithography and Ultra High Density Package Substrate for Next Generation System-on-Package (SOP)

3D Glass-Based Panel-Level Package with Antenna and Low-Loss Interconnects for Millimeter-Wave 5G Applications