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

Purpose – The functionality of personal mobile electronics continues to increase, in turn driving the demand for higher logic-to-memory bandwidth. However, the number of inputs/outputs supported by the current packaging technology is limited by the smallest achievable electrical line spacing, and the associated noise performance. Also, a growing trend in mobile systems is for the memory chips to be stacked to address the growing demand for memory bandwidth, which in turn gives rise to heat removal challenges. The glass interposer substrate is a promising packaging technology to address these emerging demands, because of its many advantages over the traditional organic substrate technology. However, glass has a fundamental limitation, namely low thermal conductivity (∼1 W/m K). The purpose of this paper is to quantify the thermal performance of glass interposer-based electronic packages by solving a multi-scale heat transfer problem for an interposer structure. Also, this paper studies the possible improve...

Multi-scale thermal modeling of glass interposer for mobile electronics application

An overview of ceramic packaging as it evolved over the last two decades from dual-in-line packages to state-of-the-art multilayer multichip packages ispresented. IBM’s 69 layer glass-ceramic/copper multilayer multichip substrate with dielectric constant of 5.0, thermal expansion exactly matching silicon and exceptional dimensional control is summarized.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400496934

Ceramics and Glass-Ceramics in Electronic Packaging

Measurement, Modeling and Characterization of Embedded Capacitors for Power Delivery in the Mid-Frequency Range

In this study, individual interactions between various classes of organic additives in electrolytic copper plating solutions are characterized by electroanalytical methods. Cyclic voltammetry and chronopotentiometry were used to compare cases of sequential and competitive adsorption of additive combinations to the Cu cathode. Of the polyalkylene glycol (PAG) suppressors investigated, polypropylene glycol was in general a weaker suppressor than polyethylene glycol, showing weaker polarization of the Cu cathode and faster depolarization when combined with bis(sodium sulfopropyl)disulfide (SPS). The rapid depolarization of PAG with SPS resulted in a conformal Cu filling behavior in blind-vias. By itself, the leveler molecule polyvinyl pyrrolidone (PVP) shows very weak and slow suppression compared to the PAG-type suppressors, but depolarization of the Cu cathode is prevented when combined with SPS. The weak polarization of PVP combined with SPS resulted in sub-conformal filling behavior in blind-vias. The potential response of SPS, PAG, and PVP combined was found to be the sum of their individual interactions: PAG adsorbs rapidly to strongly polarize the cathode, but PVP prevents depolarization with time from SPS. This strong and consistent polarization outside the vias resulted in a superconformal filling behavior, with more than twice the thickness of Cu plated in the vias than outside.

Electroanalytical Study of Organic Additive Interactions in Copper Plating and Their Correlation with Via Fill Behavior

This paper demonstrates the high frequency performance and thermo-mechanical reliability of through vias with 25 µm diameter at 50 µm pitch in 100 µm thin glass substrates. Scaling of through via interconnect diameter and pitch has several electrical performance advantages for high bandwidth 2.5D interposers as well as mm-wave components for 5G modules. This paper focuses on the assessment of thermo-mechanical reliability, of high aspect ratio TPVs at ultra-fine pitch, metallized using a via–first approach, and the accurate electrical modelling of TPVs and transmission lines with TPVs up to 40 GHz, using ANSYS HFSSTM. Test vehicles consisting of through via daisy chain structures were designed and fabricated on 100 µm thick glass, laminated with a 5 µm epoxy dry film polymer on both sides. Fine pitch TPV arrays were subjected to Thermal Cycle Testing (TCT) between -55 °C and 125 °C, and the majority of TPV chains passed 1000 cycles with less than 15% change in DC resistance. The impact of pitch scaling on the reliability was studied by varying the spacing of neighboring TPVs using 3D quarter-symmetric finite element models. A novel approach based on wave dimensional analysis was investigated to accurately capture the electrical parasitics of the vias in mm wave frequency bands. The resistance and inductance of a single signal TPV at 28 GHz were estimated to be 93 m and 60 pH respectively. Using Voltage Standing Wave Ratio (VSWR) calculations, it was shown that smaller via diameters are preferable for transitions from a 50 impedance matched planar to vertical interconnection.

High Frequency Electrical Performance and Thermo-Mechanical Reliability of Fine-Pitch, Copper-Metallized Through-Package-Vias (TPVs) in Ultra-Thin Glass Interposers

Rao Tummala

Papers

Multi-scale thermal modeling of glass interposer for mobile electronics application

Ceramics and Glass-Ceramics in Electronic Packaging

Measurement, Modeling and Characterization of Embedded Capacitors for Power Delivery in the Mid-Frequency Range

Electroanalytical Study of Organic Additive Interactions in Copper Plating and Their Correlation with Via Fill Behavior

High Frequency Electrical Performance and Thermo-Mechanical Reliability of Fine-Pitch, Copper-Metallized Through-Package-Vias (TPVs) in Ultra-Thin Glass Interposers