[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

Damascene copper electroplating for on-chip interconnections, a process that we conceived and developed in the early 1990s, makes it possible to fill submicron trenches and vias with copper without creating a void or a seam and has thus proven superior to other technologies of copper deposition. We discuss here the relationship of additives in the plating bath to superfilling, the phenomenon that results in superconformal coverage, and we present a numerical model which accounts for the experimentally observed profile evolution of the plated metal.

Damascene copper electroplating for chip interconnections

Hydrogen evolution reaction (HER) in alkaline medium is currently a point of focus for sustainable development of hydrogen as an alternative clean fuel for various energy systems, but suffers from sluggish reaction kinetics due to additional water dissociation step. So, the state-of-the-art catalysts performing well in acidic media lose considerable catalytic performance in alkaline media. This review summarizes the recent developments to overcome the kinetics issues of alkaline HER, synthesis of materials with modified morphologies, and electronic structures to tune the active sites and their applications as efficient catalysts for HER. It first explains the fundamentals and electrochemistry of HER and then outlines the requirements for an efficient and stable catalyst in alkaline medium. The challenges with alkaline HER and limitation with the electrocatalysts along with prospective solutions are then highlighted. It further describes the synthesis methods of advanced nanostructures based on carbon, noble, and inexpensive metals and their heterogeneous structures. These heterogeneous structures provide some ideal systems for analyzing the role of structure and synergy on alkaline HER catalysis. At the end, it provides the concluding remarks and future perspectives that can be helpful for tuning the catalysts active-sites with improved electrochemical efficiencies in future.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201700464

Electrocatalysts for Hydrogen Evolution in Alkaline Electrolytes: Mechanisms, Challenges, and Prospective Solutions

Hybrid supercapacitors with their improved performance in energy density without altering their power density have been in trend since recent years. The hybrid supercapacitor delivers higher specific capacitance in comparison to the existing electric double layer capacitor (EDLC) and pseudocapacitors. Generally, the asymmetric behavior of hybrid supercapacitors which is the combination of EDLC and pseudocapacitor acts as an enhancer in its respective capacitance values. This asymmetric approach marks a new beginning towards the much-needed pollution free, long lasting and proficient energy-storing performance. Corresponding to their utilization in hybrid electric vehicles and similar sort of power necessity based devices; the research in developing new advanced storage devices finds an enormous and vast future ahead. The most significant factor for the energy efficient applications demands a considerably higher ratio of surface to the volume by incorporation of new materials. This review article gives an overview of recent advances in the development of hybrid supercapacitors, storage mechanism, criteria of formation, components, different electrode and electrolyte materials, electrochemical profile assessment, design fabrication and their applications.

A review on recent advances in hybrid supercapacitors: Design, fabrication and applications

Study of diffusion mechanism in low-temperature bonding method based on Cu microcones is reported. A Sn layer was electrodeposited on the Cu microcones and the electrodeposited Cu substrate then annealing at bonding temperature 463 K. IMC grains of Sn/Cu-microcones diffusion samples grew slow with smaller size. The special morphology of Cu microcones was beneficial for the growth of intermetallic layer in short annealing time and the advantage disappeared with longer annealing time, which ensured the good performance of this bonding method.

Study of diffusion mechanism in low-temperature bonding method based on surface Cu microcones

A simple electroless deposition method of fabricating silver nanosheets which is a promising replacement for a high-temperature lead-rich solder used for electronics has been reported. This substrate free deposition method can solve the surface coating problem of the nanostructured silver. By controlling the deposition time, the silver nanosheets with a length of 2μm and a width ranging from 10nm to 20nm have been selected due to its relative large surface area and high uniformity. The relatively high surface energy of nanostructured silver results in a melting point depression. About lμm high Cu micro cones are used to bond with the silver nanosheets. After room temperature bonding with the assistance of a constant pressure of 10kPa, the bonded sample was put in the oven to be heated to accumulate the diffusion between the two metals. More crystal information of the silver nanosheets has also been provided by X-ray diffraction analysis (XRD) and transmission electron microscope analysis (TEM) respectively. As silver has high electrical and thermal conductivities, this silver nanosheets has potential applications as conducting interconnectors and tracks in printed circuit boards.

Preparation of silver nanosheets used for low temperature bonding

The preparation of polymer films on silicon (Si) is one of the key technologies for microelectronics, especially in 3D package. In this work, water-phase grafting is a novel technology for grafting polymer film in the solution using water as solvent. Poly(methacrylimide) (PMI) and poly(methylacrylic acid) (PMAA) initiated by 4-Nitrobenzene diazonium (NBD) tetrafluoroborate were radical grafted on 4-inch silicon wafer. With the help of SEM, ellipsometry, XPS and AFM, the surface morphology, properties of PMI and PMAA organic grafted films was firstly researched. After heat treatment (HT) of 50 °C or 200 °C, PMI and PMAA films had low dielectric constant, low dielectric dissipation factor and strong corrosion resistance. This is of great significance for the large-scale application of Water-phase grafted organic films.

Reliability of Ultrathin Organic Insulating Films for 3D Package

In this paper, nickel-phosphorus (Ni-P) films with high phosphorus content were electroless deposited on commercial high purity Al substrates after various zincate immersion pretreatments. Single, double, and triple zincate immersion pretreatments were performed at room temperature before Ni-P electroless plating. The influence of pretreatments on the corrosion resistance of Ni-P films was analyzed by electrochemical impedance spectroscopy and Tafel curves. Scanning electron microscopy was used to characterize the surface morphologies of zinc films and Ni–P films. The best corrosion resistance performance was observed on Ni-P film pretreated by triple zincate immersion, and this may be principally due to its dense structure.

Effect of zincate immersion pretreatment on corrosion resistance of electroless plated nickel-phosphorus film for advanced packaging

Ag-8Au-3Pd alloy wire has shown its advantages as a kind of interconnect material in semiconductor packaging. In thermosonic wire bonding, a uniformed and stable Free-Air-Ball (FAB) created by electronic flame-off (EFO) is crucial to a reliable 1st bond. In this study, the relationship between Free-Air-Ball (FAB) size and EFO parameters (EFO current, EFO time) of 0.6 mil Ag-8Au-3Pd alloy wire has been investigated. According to the FAB formation curve of 0.6 mil Ag-8Au-3Pd alloy wire, a suitable EFO parameter was settled down, then a design of experiment (DOE) was set up to investigate the optimum parameter window. As expected, the experiment results illustrate that 0.6 mil Ag-8Au-3Pd alloy wire is workable as the interconnect material with less cost.

http://ieeexplore.ieee.org/iel7/6745316/6756403/06756453.pdf

Ming Li

Papers

Study of diffusion mechanism in low-temperature bonding method based on surface Cu microcones

Preparation of silver nanosheets used for low temperature bonding

Reliability of Ultrathin Organic Insulating Films for 3D Package

Effect of zincate immersion pretreatment on corrosion resistance of electroless plated nickel-phosphorus film for advanced packaging

Research on 0.6 mil Ag-8Au-3Pd alloy wire bonding process