As a fundamental study of the photoetching of precision metal components, the spray etching rates of ferric chloride etchants were analyzed. A full-cone spray forms the most uniform flow distribution, and this configuration was employed in this analysis. The effects of temperature, spraying pressure and spraying distance on the spray etching rates on mild steel were quantitatively investigated to develop an empirical formula for spray etching rate. A physical evaluation of fluid flows in the spraying system was made to elucidate the effect of the impact of the etchant spray. Experimental results indicate that the spray etching rate is proportional to the 1.2th power of the velocity of the ferric chloride etchant, and that the spray etching rate is proportional to the 0.6th power of the kinetic energy of the etchant on metal surfaces. Spray etching behavior was found to be analogous to the mass transport phenomena in turbulent flows.
A new method of Zn-Ni alloy coating has been developed in which Zn/Ni double coated films were electroplated onto steel substrates, and then irradiated by a high-power CO2-laser to alloy the Zn/Ni. Alloying conditions of the laser-irradiated films were then examined. X-ray diffraction analysis revealed that the irradiated films were of the Ni5Zn21 (γ-phase) structure. EPMA line analysis showed that the surface of the irradiated films was produced by diffusion from the Ni in the underlying film to the surface of the Zn overlying film. This demonstrated the utility of alloying Zn/Ni double coated films by CO2-laser irradiation.
A silica film was formed on a polycarbonate substrate by a plasma CVD technique using tetraethoxysilane (TEOS), a kind of organosilicone compound, and N2O gas as the raw materials. Adding Ar gas with TEOS to a reactor significantly improved adhesion between the silica film and the polycarbonate substrate, with the improvement becoming more pronounced as the quantity of Ar gas was increased. This phenomenon was observed only when TEOS and N2O gas were used and was not seen with SiH4 and N2O gas. XPS analysis indicated that decomposition of the phenyl groups of the substrate was accelerated with an increasing quantity of Ar gas, resulting in the formation of C-O, C=O groups. Based on these results, the following reaction mechanism is thought to occur on the substrate. Excited Ar gas and the reaction intermediates of TEOS, in which the main structure should be -Si-O-, are formed initially in the plasma state. Then, C radicals are generated on the substrate surface as a result of the attack by excited Ar gas. The C radicals combine with the reaction intermediate of TEOS, and finally -Si-O-C- bonds are formed. These bonds work to improve adhesion between the silica film and the substrate.
The effect of plasma-sprayed Al2O3-TiO2 and Ni-Cr alloy coatings as undercoatings of PTFE resin on the corrosion resistance of various Al-alloy substrates was investigated by atomic absorption analysis of dissolved Al3+ ions in a solution of 1% NaCl+1% EDTA. Ni-Cr coatings promoted substrate corrosion, while those of Al2O3-TiO2 exhibited high corrosion resistance. With a coating of Al2O3-TiO2, even Al-diecasts containing less than 84wt.% Al showed corrosion resistance similar to that of alloys containing more than 96wt.% Al.
Electroless deposition of cadmium films was investigated using titanium trichloride as a reducing agent. Cadmium films were formed direcity on the surface of aluminum substrates activated with palladium. The deposition rate increased with increasing titanium trichloride concentration, bath temperature, and pH. Silver-like bright cadmium film was produced from a solution containing cadmium dichloride 0.08M, trisodium citrate 0.34M, disodium EDTA 0.08M, NTA 0.20M, and titanium trichloride 0.04M, at temperatures above 70°C and pHs above 9.5. Each complexing agent served as bath stabilizer as well as plating promoter. Intended thickness was obtained by renewing the bath at 30-minute intervals. Cadmium sulfide film was also electrolessly plated from the cadmium bath to which sodium thiosulfate was added. Films obtained at above pH 10.0 were of polycrystalline cadmium sulfide similar to chemically deposited films for solar cell applications.
Electroless copper deposition is more uniform than the electroplating, but its uniformity is decreased with increasing aspect ratio of through holes on the printed circuit boad. To improve the uniformity, we investigated concomitant application of current during the electroless copper plating process. The studies showed that the uniformity, physical properties and plating rate were greatly improved when PR and pulse current were applied simultaneously. To investigate the effect of current, galvanostatic electroplating was carried out in an electroless copper bath containing no formaldehyde. The surface morphology was found to be similar to that of the electroless copper deposition with improved the uniformity and the physical properties. From the potential-time curves, we also found that the transient phenomena of the potential are closely related to the plating morphology and specifically to the faradic region of the cathode process. Thus it is confirmed that the uniformity and the physical properties of electroless copper plating are also greatly influenced by the faradic region of the applied cathodic current.
The throwing power of Cu (II)-ethylenediamine complex plating baths and the mechanical properties of the films obtained were investigated. The addition of ammonium sulfate and glycine was found to increase specific conductivity and polarization resistance, resulting in an increase in throwing power. The further addition of a small quantity of thiodiglycollic acid to the baths resulted in an increase in the elongation and contributed to the brighting of the films. Under suitable conditions, the films obtained were shown to have the same elongation and ultimate tensile strength as commercial high-ductile electrolytic copper films.
The collapse of cavitation bubbles in liquids resulted in a shock wave pressure, a jet flow and a water hammer pressure due to the jet flow. The cavitation action improved the physical and chemical properties of the deposited films. Micro-Vickers hardness increased with the occurrence of elastic deformation and strain hardening of crystals, or the space lattices in the crystals were crushed. Porosities decreased because the hydrostatic pressure pushed the deposited particles into the pinholes. It is considered that the crystal dislocation produced was in excess of 0.2MPa, and that the energy due to hydrostatic pressure was sufficient to account for the crystal dislocation.
The electroplating of Pd-Ni alloys from an ethylenediamine complex bath was investigated with pulsed currents. Pulse parameters, including current density and period, had a marked effect on current efficiency, the composition of the alloy deposit, and its surface morphology. Smooth, bright deposits could be obtained although there was appreciable cracking.