Electroless nickel/gold plating and electroless nickel/palladium/gold plating processing have been applied widely to copper patterns as a surface finishing treatment for electronic devices. Recently, miniaturization of copper patterns has advanced to increase the functionality of electronic devices. Conventional electroless nickel plating processing applied to fine copper patterns causes nickel growth in the lateral direction. As a result, the copper pattern distance narrows, which might cause short circuits. To resolve this difficulty, electroless palladium plating on copper has been investigated. This study specifically examined pretreatment processes involving cleaning and soft etching. Results show that the wire bonding characteristics on the electroless palladium/gold plated film differed remarkably depending on the selection of the pretreatment solution used for cleaning and soft etching. Particularly, using a neutral cleaner and a thiol type soft etching solution suppressed dissolution of the copper during the palladium catalyst treatment. Results show that the possibility of obtaining a palladium plated film with fewer pinholes and voids. For electroless palladium /gold plating processing, results show that the soft etching step and the selection of the pretreatment solution used in the cleaning step are important.
To elucidate the mechanisms of the low friction coefficient in CVD diamond film, a series of pin-on-plate type friction tests was performed in ambient air and in argon. As the test piece, a combination of high-speed tool steel JIS-SKH51 pin and CVD diamond plate was used. Results obtained in air showed that the coefficient of friction decreased concomitantly with the increase of the applied load. Furthermore, the existence of the graphite-like material was confirmed from the Raman spectrum of the wear debris. These results confirmed that, for friction between SKH51 and diamond in air, frictional heat promoted the graphitization of diamond. However, in tests conducted in argon, the load dependence was the same as that in air in the low load region but the coefficient of friction increased at the highest load. In tests conducted in argon, the possibility was considered that a low coefficient of friction might develop because of adsorbed oxygen and oxide film formed on the SKH51 pin. To clarify their effects, a friction test was conducted using a non-heat-treated pin and a pin that was heat-treated at 550 °C for 1 h in air. Test results show that the heat-treated pin maintained a low coefficient of friction for a long time. Results suggest that the adsorbed oxygen and the oxygen in oxide film promote graphitization of diamond in argon in the low-load region. However, at the highest load, the coefficient of friction increased because adsorbed oxygen and oxygen in oxide film alone were unable to produce sufficient graphite-like material to accommodate the increased friction area. These results indicate that when oxygen in ambient air or oxide film is present on the friction surface, diamond transformed to the soft graphite-like material by frictional heat shows a low coefficient of friction.
To improve the frictional properties of titanium, a series of pin-on-plate friction tests was performed using a TiC-coated sample, a plasma carburized titanium sample, and a pure titanium sample. Friction tests were conducted in ambient air for all combinations of pins and plates with surfaces of three types, including no-treatment. Results show that all combinations, including plasma carburized samples in pins, plates or both, had a coefficient of friction of less than 0.2. Raman spectroscopic analysis of the plasma carburized specimen surface confirmed the presence of a graphite-like material, which explains the low friction coefficient. A combination of the TiC-coated pin and plate also showed a low coefficient of friction at about 0.1 in ambient air, but no graphite-like material was observed from the wear debris. A friction test performed in argon using the same combination of pin and plate confirmed graphite-like material in the wear debris. From this observation, it was inferred that most of the friction-produced graphite-like material was lost through oxidation in ambient air. Experiment results clarified that use of the plasma carburized surface or of the TiC-coated surface, or both together, is effective for improving the frictional properties of titanium. Results further showed that the combination of the TiC-coated surface is optimal for improving wear resistance, whereas the combination of the plasma carburized surface is optimal for lowering the coefficient of friction. Additionally, results indicated that graphite-like material existing with friction surfaces lead to a low coefficient of friction.