A hard chromium plating technique was established using trivalent chromium chloride with a highly concentrated calcium chloride aqueous solution. The obtained films show dense and uniform microstructure, high hardness of 1000 HV and good wear resistance, which are comparable to those of conventional hexavalent chromium plated film. The hardness properties showed little thermal degradation, in contrast to the case of hexavalent chromium film. The carbon content was one magnitude lower than that of a conventional trivalent chromium bath containing carboxylic acids. The lack of thermal degradation of film hardness might derive from the inhibited particle growth resulting from the low carbon content and the high oxygen content. The current efficiency was 60-70%, much higher than those of hexavalent chromium plating and conventional trivalent chromium plating. Because trivalent chromium plating technique using a highly concentrated calcium chloride aqueous solution produces excellent film characteristics and productivity, this plating technique is anticipated as a technology underpinning the industrial production of hard chromium plating.
As a formaldehyde-free electroless copper plating bath for thin conductive covering inside through-holes of printed circuit boards, this study evaluated a room-temperature glyoxylic acid and Cu-ethylenediaminetetraacetic acid（EDTA）system. Electrochemical behavior was analyzed through polarization curves obtained on Cu plate with three baths:（a）a Cu-ion bath without glyoxylic acid,（b）a glyoxylic acid only bath without Cu-ion, and（c）a completely electroless bath containing all components. They showed similar behavior to that of the Cu-EDTA system using formaldehyde as a reducing agent. The Cu-ion concentration was the most effective at improving the plating rate. Three additives were used to improve the bath stability: K2S, 2-2‘-bipyridyl, and polyethylene glycol. The following items were found to be important to achieve a sufficient level of through-hole coverage: i）maintaining the copper concentration inside the through-hole above a sufficient level, and increasing the bulk Cu-ion concentration and proper agitation; ii）controlling the plating rate using additives of 0.8-2.0 μm / h, even in the high Cu-ion concentration condition. Results demonstrated that glyoxylic acid can replace formaldehyde even in the field of low-temperature thin covering application as the pretreatment of electrolytic through plating. It helps eliminate health and the environmental issues resulting from the widespread use of formaldehyde in the printed circuit board manufacture industry.
Among hydantoin derivatives, a monovalent gold complex was obtained when 1-methylhydantoin（MH）and hydantoin（HY）were used as ligands. These are more beneficial for use in gold plating solutions than trivalent gold complex of 5,5-dimethylhydantoin（DMH）. Moreover, these complexes can be extracted as crystals. Therefore, the chlorine concentration, constituting a major impurity in gold plating for the electronics industry, can be kept low. Each crystal coordinated two hydantoin derivatives to gold and had water of crystallization. The gold-HY complex solution is stable at pH 5-9. Moreover, no change in pH or decomposition occurs even when hydrogen peroxide is added. Higher stability can be expected in the gold plating solution than for gold sulfite.
A neutral（pH 6-7）gold plating solution using the gold-HY complex was investigated. When a large amount of DMH as the complexing agent is added in anticipation of an increase in the plating bath stability, the deposited film appeared to be dark brown. When DMH in the composition of the plating solution was set to a molar equivalent ratio with gold of 0.6-1, the deposited film appearance was bright yellow.
Using the electrochemical dissolution phenomenon of platinum counter electrode, we investigated the surface functionalization and characterization of platinum nanoparticles that had been electrodeposited onto aminated carbon electrodes. The electrodeposited platinum functions with nitrogen-atom-containing functional groups introduced by electrolysis in ammonium carbamate solution. The groups can include aromatic amine groups such as aniline. Together, they function as active sites of specific electrocatalytic current, as found from SEM and XPS observations and electrochemical properties.
Efficient analysis of Cr(VI) samples is important for the environment and for metal finishing industries. For this study, microplate assay was applied for Cr(VI) analysis using diphenylcarbazide for rapid and simultaneous analyses of multiple samples. Results demonstrated that the microplate assay can also detect Cr(VI) at concentrations below the effluent standard. Furthermore, the assay has high measurement repeatability and good agreement with the official assay method.
Catalyst modification on SiC substrates is a key technology for forming electrodes of power devices by electroless deposition. We deposited noble metals of five kinds on 4H-n-SiC substrates in a mixture solution of metal salt and HF under photoillumination. The metal particle nucleation and growth behavior differed considerably depending on the kind of metal.