Electrodeposited tin-silver alloys show promise as lead-free alternatives to solder coating. Eutectic tinsilver alloy film was deposited at 2∼3A/dm2, 25°C, and pH 8 using the following bath composition: 0.19M SnCl2, 0.01M CH3COOAg, 1.0M L-tartaric acid, and 0.2M N-acetyl-L-cysteine. The presence of N-acetyl-L-cysteine markedly promoted silver deposition over a noble potential range. The eutectic tin-silver alloy film consisted of β-Sn and ε (Ag3Sn) phases, and its solidus temperature was 221°C. An intermetallic compound layer (Cu6Sn5) was formed at the interface of the alloy film and copper substrate in heat treatment, forming a Sn-Ag-Cu ternary eutectic (m. p. 217°C) with reactions of Cu6Sn5 and ε (Ag3Sn) phases.
Tungstate ion reduction was studied in 1mol·dm-3 KCl or 0.5mol·dm-3 citric acid solutions using DC polarography. In citric acid solutions containing only tungstate ions, a tungstate ion reduction wave was observed only at 3.5 pH. This wave disappeared when cobalt ions were added to the solution because the hydrogen evolution current increased. Polarograms from KCl solutions containing only tungstate ions showed a well-defined tungstate ion reduction wave when the solution's pH was from 3.2 to 3.9. A clear tungstate ion reduction wave preceded by a cobalt deposition wave appeared in the KCl solution containing tungstate and cobalt ions at 6.0pH, but no reduction wave was obtained in the solution without cobalt ions. The limiting current for the tungstate ion reduction was proportional to that for the cobalt deposition, when the concentration of cobalt ions was lower than that of tungstate ions. This linear relation suggests that cobalt deposition induces tungstate ion reduction.
Fe-B amorphous alloy film was formed by means of contact plating method, in which Cu foils in contact with Al wires were used as substrates. Local battery configuration of the Cu foil anode and the Al wire cathode was responsible for film formation. The boron content in film was controlled from 0at% to 28at% by changing the KBH4 concentration in the bath. The bath temperature strongly affected the crystallographic structure of resultant films. Fe80B20 amorphous films required a bath temperature below 40°C. Film structure and composition also affected magnetic properties. Film coercivity below 17Oe was also observed.
This paper describes the effects of conditions, such as prebaking length, exposure energy, and postbaking temperature, on polybutadiene resist film formation, when obtaining high chemical resistance to hot phosphoric acid etchant. After alumina ceramic was etched at temperatures from 260°C to 320°C, we measured the change in resist thickness, resist film breakdown ratio, and etch factors. Polybutadiene molecules are cross-linked both photolytically and pyrolytically, so postbaking critically affects the enhancing of the resist's thermal and chemical stability. Prebaking at 80°C for 30min, exposure at 7-9mJ/cm2, and postbaking at 300°C for 30min yielded a highly chemically resistant, strongly adhesive, optimal resist film. The etch factor increased with increasing etching temperature, probably due to decreased acid viscosity, becoming about 2 at an etching temperature of 300°C. At higher etching temperatures, however, the etch factor decreased and the resist breakdown ratio increased, indicating that the applicable maximum etching temperature was 300°C for the polybutadiene resist.
Cr-Mo steel was plasma-sulfnitrided using hollow cathode discharge between steel and MoS2 plates. The MoS2 plate was parallel to the steel plate at an interval of 3-10mm. Treatment was at 823K for 10.8ks in an atmosphere of 30vol% N2-70vol% H2 mixing gas at 665Pa. Steel was also ion-nitrided without MoS2 under the same conditions to compare plasma sulfnitriding. Plasma-sulfnitrided layers formed on the steel were analyzed using EDX, XRD, micrographic structure observation, and hardness measurement. An iron nitride layer of 4μm and a nitrogen diffusion layer of 400μm were formed on the steel ion-nitrid without MoS2. A compound layer 8-15μm thick and a nitrogen diffusion layer about 400μm thick were formed on plasma-sulfnitrided steel. The compound layer consisted of FeS containing Mo and iron nitrides. ε-Fe2-3N and γ′-Fe4N iron nitrides form beneath the FeS. The compound layer thickness and surface hardness differ with the spacing interval two cathodes in the same sample temperature. Surface hardness in plasma sulfnitriding was distributed from 640 to 830Hv. The hardness of nitrogen diffusion layers was distributed mainly from 600 to 400Hv, gradually decreasing to the base. Surface hardness was higher in plasma sulfnitriding than conventional molten salt sulfnitriding, perhaps due to Mo in the sulfnitriding layer.