Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 67 , Issue 8
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  • Takahiro YAMAGUCHI, Kohshin TAKAHASHI, Teruhisa KOMURA
    1999 Volume 67 Issue 8 Pages 843-849
    Published: August 05, 1999
    Released: November 15, 2019
    JOURNALS OPEN ACCESS

    Electron transfer of indigotetrasulfonate ion at 4-aminothiophenol (ATP) monolayer-modified electrode was examined in the pH range of 2 to 6 by cyclic voltammetry and ac impedance spectroscopy. By changing up the pH of electrolyte from 2 to 6, the redox process of indigotetrasulfonate becomes reversible in the presence of ATP monolayer-modified electrode. While the electron-transfer rate constant of indigotetrasulfonate for bare gold was decreased from 2.5×10−3 cms−1 at pH 2 to 4.7×10−5 cms−1 at pH 6, that for ATP monolayer-modified electrode was increased from 3.2×10−5 cms−1 to 1.6×10−2 cms−1. Reversible redox reaction of indigotetrasulfonate were also observed at cystamine and 4-mercaptopyridine modified electrodes at pH 6, but were not observed at 3-mercaptopropanesulfonic acid, 1-butanthiol and 4-hydoroxythiophenol at pH 6. Our results suggest that the electron transfer rate of indigotetrasulfonate ion is controlled by a specific interaction between the amine groups of the thiol monolayer and indigotetrasulfonate ion.

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Technological Reports
  • Aulis TUOMINEN, Ville LEHTINEN, Eero RISTOLAINEN
    1999 Volume 67 Issue 8 Pages 850-854
    Published: August 05, 1999
    Released: November 15, 2019
    JOURNALS OPEN ACCESS

    The compatibility of flip chip fluxes, underfill epoxies and solder resists on printed circuit boards (PCB) was compared by using a single lap shear test.1-3,15) The underfill adhesion to the plain solder resist was generally good, but in flip chip assembly, a flux for joining the connections of flip chips is used. Therefore, the PCB samples coated with different solder resists were fluxed and reflowed to simulate the real production environment. The underfill was applied on these residues and another piece of PCB, treated in same way was attached on it maintaining a consistent gap between two pieces. The underfill was cured according to each manufacturer's specification and a single lap shear test was carried out. The correlation of the variable results was verified by assembling a test flip chip using some of the tested materials and subjecting them into temperature cycling. The adhesion strength was verified by investigating underfill delamination by scanning acoustic microscopy (SAM).

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  • Hideo YAMAMOTO, Kazuyuki KANEMOTO, Masashi OSHIMA, Isao ISA
    1999 Volume 67 Issue 8 Pages 855-861
    Published: August 05, 1999
    Released: November 15, 2019
    JOURNALS OPEN ACCESS

    Current-voltage characteristics of aluminum, tantalum and platinum contacted to a pellet of chemically polymerized polypyrrole were investigated. A typical passivation curve was observed for both an anodic and a cathodic polarizations of aluminum and tantalum, which means a formation of an insulated layer at a contact surface, and there was a resemblance in the I-V curves between the anodic and the cathodic polarization curves of aluminum and tantalum. The current in the I-V characteristics was influenced by ambient moisture, decreasing with increases in relative humidity. Similar behavior has been found for a non-valve metal of platinum, which indicates the passivation is due to a transformation of conductive polypyrrole to an insulator. The deterioration of polypyrrole is assumed to be caused by a synergetic effect of oxygen and water. The self-healing behavior in a solid electrolytic capacitor with polypyrrole electrolyte would be caused mainly by a transforming reaction of a conductive polypyrrole electrolyte to an insulator occuring at the contact surface under applied voltage.

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