Electroless nickel plating has been extensively applied on copper circuits as an under-layer deposition for solder joints, since it is possible to deposit on the isolated patterns without an outer electrode. A palladium catalyst is generally used for the electroless nickel plating reaction on the copper patterns, because copper has a lack of catalytic activity for initiation of the deposition reaction. The electroless nickel plating is applied on the condensed copper patterns by using the palladium catalyst ; however, nickel deposits tend to occur on the resin surface due to the adsorption of palladium ions on it. Dimethylamine-borane (DMAB) has a feature of catalytic activation power on the copper. Therefore we applied dilute nickel plating solution containing DMAB as an initiator for electroless nickel deposition on the copper surface instead of applying the palladium catalyst. Selective nickel plating on the copper patterns without deposition on the resin substrate was achieved using a dilute nickel plating bath containing DMAB. In addition, the strength of solder joints was improved by introducing this process. In this way, nodules on the nickel surface were greatly suppressed, and strong joints between the solder and deposited nickel were achieved.
The corrosion behavior of carbon steel in electrolyzed alkaline water, such as sodium chloride, sodium sulfate, sodium carbonate and ammonium carbonate, was investigated. As a result of that, in electrolyzed alkaline water of sodium chloride, local corrosion was occurred in the orifice area of the carbon steel. The same phenomenon was observed in the electrolyzed alkaline water of sodium sulfate. But in the electrolyzed alkaline water of sodium carbonate and ammonium carbonate, no corrosion was generated. To clarify the corrosion behavior of carbon steel in electrolyzed alkaline water, the pH and redox potential were measured, then the corrosion potential (natural electrode potential) was measured and the anticorrosion behavior of electrolyzed alkaline water was considered. The reasons why no corrosion was generated on the carbon steel immersed in alkaline water of sodium carbonate and ammonium carbonate were assumed to be that, since there were no corrosive ions present, significant alkalization of the solution and negativation of the redox potential occurred, and the immersed carbon steel was in a state of immunity or passivation.
100V aluminum electrolytic capacitors with high performance are strongly demanded from the market. Silica or aluminosilicate ethylene glycol sols in combination with three kinds of organo-phosphorous acids were added into a quaternary alkylammonium salt-based electrolyte solution to increase its sustaining voltage while keeping its high electrolytic conductivity and high thermal stability. In addition to the ordinary life evaluation test, investigation of initial electric properties and assessment for sustaining voltage of capacitors using those electrolyte solutions during dc-load life tests at 378K were performed. Consequently, we observed that the combination between aluminosilicate ethylene glycol sol and dibutyl phosphate gives the most promising performance. The capacitors using the optimized electrolyte afforded less than one-half ESR at 233K and more than twice the durability compared with those using a conventional electrolyte solution. These results demonstrate the possibility to apply quaternary ammonium salt-based electrolyte solutions for 100V aluminum electrolytic capacitors.
Formation constants of gold complexes containing hydantoin derivatives such as l-methylhydantoin (MH), 5,5-dimethylhydantoin (DMH), 1,5,5-trimethylhydantoin (TMH), and 5,5-dimethyloxazolidine-2,4-dione (DMOD) were evaluated by analyzing the amount of chloride ions which were emilinated upon coordination of the hydantoin derivatives to a tetrachloroaurate ion. Electrochemical chloride ion sensor proved to be a convenient probe to determine the concentration of the chloride ion. The formation constants decreased with the ligands in the order of TMH>DMH>DMOD>MH, which were consistent with the order of stability expected from polarization curve measurements.