β-titanium alloys are convenient as eyeglass frame materials because they are light and have good cold-workability and corrosion resistance. However, hydrogen penetrates easily into them by cathodic reaction, which may cause hydrogen embrittlement. Measuring the diffusion coefficient of dissolved hydrogen around room temperature is important to prevent breakage by hydrogen embrittlement. In the present work, the entry of hydrogen into Ti-22V-4Al alloy caused by cathodic polarization in sulfuric acid solution at 298K was examined by using the heating extraction method. The catholic polarization introduced a large amount of hydrogen into the titanium alloy. The hydrogen atoms dissolved in the titanium alloy were stable and evolution of hydrogen was negligibly small at room temperature. To obtain the diffusion coefficient of hydrogen DH, the polarization time dependence of the hydrogen concentration was examined. DH at 298K was determined to be 4.8×10-14m2/s and the activation energy for diffusion of hydrogen was found to be 36kJ/mol by analysis of the thermal spectra of the hydrogen evolution rate.
Palladium was electroplated on copper at 50-200A/m2 in a chloride bath. The current efficiency for palladium deposition was nearly equal to 100% at 50A/m2 and smaller at a larger current density. Hydrogen in the electroplating palladium film was analyzed by measuring its thermal evolution spectrum. Two peaks were observed in the thermal spectrum of the hydrogen evolution rate. The lower and higher temperature peaks originated in evolution of the hydrogen dissolved in normal lattices of palladium atoms and the hydrogen trapped by lattice defects such as dislocations and grain boundaries, respectively. The concentration of hydrogen was calculated from the area of the hydrogen evolution peaks. The concentrations of the lattice-dissolved hydrogen and the trapped hydrogen in the palladium film electroplated at 50A/m2 were 14 and 5 mass-ppm, respectively. The concentrations of hydrogen were higher at a larger current density.
In the basic concept of conventional electroplating, the additive, which determines the properties of the de-posited film, is included in the bath. However, it is difficult to solve the problems related to copper minute wiring as long as one clings to this concept. In this report, ULSI copper minute wiring formation by a new process, which consists of the pre-adsorption of the additive and copper electrodeposition from an acid copper sulfate bath without an additive, will be described. A copper layer of 1μum thickness was deposited from a basic bath on the copper electrode on which the additive had been pre-adsorbed, and the catholic polarization in the basic bath which does not contain an additive was then measured. The continuance of the efficacy of the additiveafter the copper electrodeposition was confirmed. The copper electrodeposition was done using an insoluble anode in the basic bath without an additive after the silicon wafer which formed the copper seed had pre-adsorbed the additive. In the method utilizing pre-adsorption., a minute hole can be filled with copper without causing voids and seams due to the effect of the pre-adsorbed additive.
Effects of stabilizers such as lead nitrate, thiourea and thiodiglycolic acid on nickel-boron electroless plating were studied in a bath containing sodium borohydride as a reductant and tartrate salt and glycine as ligands. Lead nitrate remarkably stabilized the plating bath and gave significant deposition rates with sodium fluoride as an accelerator. Effect of the concentration of each component on the deposition rate of the film was investigated and it was found that a bath containing 0.04mol dm-3 of nickel chloride, 0.05mol dm-3 of sodium borohydride, 0.1mol dm-3 of potassium sodium tartrate, 0.1mol dm-3 of glycine, 1.2×10-4mol dm-3 of lead nitrate and 7.1×10-2mol dm-3 of sodium fluoride gave 0.54g dm-2h-1 of deposition rate comparable to ca. 1/4 of that in Nibodur bath. Spectrophotometric measurement suggested the plating rate and appearance of plating film did not depend on alteration of nickel-complex caused by concentration changes of ligands.
An electroless nickel plating bath was examined using hydrazine as a reducing agent to improve the bath stability. The plating films obtained from the basic bath are pure nickel, however, the plating films tend to show a dendrite structure of a black appearance. Therefore, the deposited films are not applicable to electronics fields. This report examines smoothing the plating films obtained from a basic bath using hydrazine as a reducing agent. Smoothing the plating films was accomplished by lowering the reducing power of hydrazine whilst the basic bath is left at a high temperature for several days. Sulphur compounds as additives and gluconic acid as a complexing agent were also effective in achieving bath stability and smoothness of deposits. Nickel can be directly deposited on copper substrate from a hydrazine reduced electroless nickel bath without a palladium activation step. Therefore, the applicability of the formation of capping metal on ULSI devices was also investigated. As a result, it was confirmed that selective capping metal deposition on the 250nm copper pads can be accomplished by this bath without palladium catalyst treatment.
Colloidal mixing hydroxide, which consists of nickel ions and copper ions, was allowed to adsorb onto an ABS resin. After making these colloids dry up, carbon and then zinc were deposited on it using the physical vapor deposition technique. Articles containing the colloids, carbon and zinc were used as substitutes for palladium catalyst in the electroless nickel plating. In the 90° peeling strength test, all of these electroless plated nickel films showed about 200kg/m compared with the peeling strength obtained by the conventional method which couples tin (2+) as a sensitizer with palladium (2+) as an activator. The strong adhesion resulted in a cohesive fracture of the ABS resin during the peeling test. Such a result shows the following; (1) the colloids invaded and adsorbed into the etching holes which occurred in the etching of the ABS resin by the chromic acid, (2) the colloids were reduced to nickel and copper by the electrons produced by dissolution of the zinc in the plating solution, and then the nickel and copper worked as an anchor for the plated nickel films. Also the nickel naturally worked as a self-catalyst for continuing the electroless nickel plating.