Many electronic devices have been requested to downsize with improving their functionality. Improved semiconductor technologies have been main routes to realize these requests. However, the further improvement of semiconductor technologies has become difficult and costly. The next main technologies to be used are the improvement of printed circuit boards (PCBs) and their connection with integrated circuits (ICs), especially bump formation and their connection methods. For these two technologies, both electroplating and electroless plating are employed as the main methods employed. In this paper, primarily PCBs and their connection methods are reviewed. For PCBs, copper plating technologies are mainly reviewed, especially the selection of additives and current waveforms which are most effective for via-filling. For connections, the formation of bumps and their connecting are reviewed. Two new technologies, nickel bump formation on an aluminum pad and, microbump formation by non-cyanide gold electroplating, were mainly demonstrated. Finally, the production of anisotropic conductive particles by electroless nickel plating are demonstrated. The discovery of new plating technologies is necessary for future development, especially the use of new additives and new agitating methods for copper plating as well as new formation methods and their connection technologies for bump formation.
Microinjection has long been regarded as an unusually difficult method but its potential usefulness has been well understood. In order to overcome its difficulty, a single-cell manipulation supporting robot (SMSR) has recently been developed. SMSR has enabled high throughput microinjection into any type of cell. Its excellent performance was demonstrated by the high success rate of simultaneous introduction of two genes into mouse ES cells. The size of an ES cell is only 20 µm in diameter. With use of a multichannel microelectrode, electrophoretic introduction and automatic positioning of microinjector have been successfully demonstrated. Owing to these studies, single-cell analysis is now recognized as a practical method for the dynamic analysis of functional role of genes, gene expression products, and other molecules in living cells. For instance, the specific role of a protein Sar1p in the trafficking in BY-2 cells could be analyzed by microinjection experiment of a Sar1p dominant negative. Further advancing study is focused on the development of novel electric/electrochemical devices with submicro or nano size and the analytical methods using these devices.
Since its invention by Binnig and Rohrer, scanning tunneling microscopy (STM) was immediately established as an invaluable and powerful surface analysis technique with atomic resolution in ultra-high vacuum (UHV). Belatedly, but assuredly, developments in STM operated at solid-liquid interfaces led to its valuation as arguably the premier technique for atomic-level surface structural investigations of chemical processes taking place at solid-liquid interfaces. It has been demonstrated that in situ STM makes it possible to monitor, under reaction conditions, a wide variety of electrode processes such as the adsorption of inorganic and organic species, the reconstruction of electrode surfaces, the dissolution and deposition of metals and semiconductors.
Birnessite type manganese dioxides doped with cobalt were synthesized by calcination of a mixture of KMnO4 and Co(NO3)2·6H2O at 600°C in air. The artificial birnessite was consisted of differently stacked slab phases depending on the cobalt content. These birnessites doped with Co exhibited different ratio of two phases; two-layer hexagonal (2H) and three-layer rhombohedral (3R) whose stacking sequences are different but belong to birnessite. The ratio of 3R/2H phases increased with increasing the Co quantity. Their electrochemical performances in Li cells were investigated in a LiClO4-propylene carbonate solution. As a result, the Co-doped birnessite demonstrated the smaller charge transfer resistance and higher reversible capacities than Co-free birnessite.
To understand the kinetics of charge transfer from chemically modified electrodes to solution species, the authors have investigated the influence of poly (Meldola’s blue) on the kinetic parameters of dopamine oxidation by rotating disc electrode voltammetry. The polymer film fixed on electrode surfaces raised the dopamine peak current by a factor of 10 in a 0.1 mM solution; this electrocatalytic effect enables one to detect dopamine at concentrations of the order of 5 µM. The polymer film increased the standard heterogeneous rate constant of dopamine oxidation more than 10-fold and favored a two-electron transfer step, thus raising the dependence of the kinetic current on the electrode potential. These effects were independent of electron self-exchange between redox-active sites in the film. They arose from the incorporation of dopamine with the polymer. This binding interaction decreased with protonation of the polymer, because of electrostatic repulsion between the positively charged species.
Poly (N-methylaniline) (PNMA) is prepared by the electro-oxidation of N-methylaniline in aqueous acid solutions. To prepare highly conductive PNMA, N-methylaniline was electropolymerized in several aqueous acidic solutions containing different organic solvents (acetonitrile, N,N-dimethylformamide an dimethylsulfoxide) and anions (ClO4−, Cl−, NO3− and SO42−). After the initial stage of the electropolymerization for the polymerizing solutions without the organic solvents, the anodic current linearly increased for the Cl−, NO3− and SO42− solutions, while it decreased for the ClO4− solution. The decreasing current for the ClO4− solution meant that the polymerization proceeded by oligomer-coupling reactions. The linear increasing current for the Cl−, NO3− and SO42− solutions implied one-dimensional nucleation growth of PNMA on the electrode surface. The polymerization rate estimated from the slope values of the i-t curves was in the order of SO42−>NO3−>Cl−. The conductivity of the obtained PNMAs was of the same order and the highest conductivity of 2.2×10−3 S cm−1 was seen for the SO42− doped PNMA. The order was explained by the Hofmeister series of the anions which are based on lyophilicity. During the polymerization, both the anion release from the monomer-anion and oligomer-anion ion pairs and the anion doping of the polymer occurred most frequently for SO42− with the lowest lyophilicity. The organic solvents were added to the SO42− polymerizing solution and the electropolymerization was performed. The conductivity of the obtained PNMAs was further enhanced. The most conductive PNMA was obtained when dimethylsulfoxide was added (σ=1.0×10−2 S cm−1). The PNMA polymer chains were tangled and stacked with each other by electron-donating association, and the tangling and stacking prevented the anion doping reaction. The addition of the organic solvents suppressed the tangling and stacking and the anion doping reaction was effectively promoted.
Fluorenyl anions were successfully accumulated in the cathode compartment of a two-compartment cell by electrochemical reduction of fluorene in various solvents. Examination of the anions by UV-visible absorption spectroscopy and NMR spectroscopy revealed that all the obtained fluorenyl anions with tetraalkylammonium counter cations were contact ion pairs. Their electronic states were close to those of solvent-separated ion pairs. These observations were understood as that, in the contact ion pairs with tetraalkylammonium counter cations, anion and cation centers were far apart, for the alkyl chains of the cations prevented the cation centers to get closer to the anion centers. Among the contact ion pairs, those in dimethyl sulfoxide (solvent with the largest dielectric constant) showed their electronic states closest to those of the solvent-separated ion pairs. The influence of alkyl chain length and that of temperature on the electronic state of the anions were both small.
In an ionic liquid electrolyte, namely 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), a compact and dense polypyrrole film was formed on a nano-porous Ta pellet anode (average pore diameter: 250 nm, specific surface area: 4,000 cm2 g−1, and specific capacitance: 50,000 µFV g−1) under a pulse anodization. In the EMI-BF4 electrolyte, polypyrrole film was uniformly deposited at a pellet surface (thickness: 240 nm) and a nano-porous domain (thickness: 240 nm). However, in a conventional aqueous electrolyte (0.1 M sodium dodecylbenzenesulfonate aqueous solution), deposition thickness was different at the pellet surface (3000 nm) and at the nano-porous domain (230 nm). The resistivity of polypyrrole film formed in the EMI-BF4 was found as low as 2×10−2 Ω/□.
The influences of thiol monolayers having terminal amino groups on the electron transfer rate for indigotetrasulfonate have been examined by cyclic voltammetry and ac impedance spectroscopy. The electron transfer rate for indigotetrasulfonate decrease with increasing pH at a bare Au electrode. The adsorption of indigotetrasulfonate ion onto 4-aminothiophenol monolayer, at low pH values, resulted primarily from an electrostatic attraction between the protonated terminal amino groups and the anions. An increase in solution pH, however, 4-aminothiophenol, cystamine, and 4-mercaptopyridine monolayer-modified electrode showed a increase in electrochemical reversibility with deprotonation of the terminal amino groups. Whereas 11-amino-1-undecanethiol, which is longchain thiol having terminal amino groups impedes the electrode reaction of [Co (phen)3]3+, this monolayer raised the apparent rate constant for indigotetrasulfonate to twice that observed at a bare Au in pH 6. Furthermore, in the presence of ethylenediamine or triethylenetetramine at pH 8, indigotetrasulfonate was obtained the reversible wave using at a bare Au. We propose a chemical interaction between the amine groups of the thiol monolayer and the carbonyl groups of indigotetrasulfonate. We postulate that protons transfer from the reduced indigo ion to the unprotonated terminal amino groups of thiols.
Recently, studies of electrochemical DNA sensors are attracting considerable attention, because they will be developed for an electrochemical DNA chip using integration, etc. The response current that originated from the formation of the DNA duplex was clearly observed using differential pulse voltammetry for a DNA-immobilized gold electrode in an electrolyte solution containing ferrocenylnaphthalene diimide as the hybridization indicator. A mismatch-discrimination was also exhibited. The authors carried out fundamental electrochemical analyses to obtain each parameter controlling the electrochemical response of the electrode system and to more qualitatively characterize.