Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2002-11-26
2004-02-24
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S461000, C428S469000, C428S702000, C428S704000, C361S523000, C361S525000, C361S528000, C361S529000, C029S025030, C252S510000, C427S079000, C427S080000, C427S081000
Reexamination Certificate
active
06696138
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a solid electrolytic capacitor and a production method thereof. More specifically, the present invention relates to a solution of an oxidizing agent (an oxidizing agent solution) and a solution of a monomer (a monomer solution) necessary for forming a solid electrolyte of the solid electrolytic capacitor. The present invention further relates to a solid electrolytic capacitor or a production method thereof, comprising preferably a solid electrolyte formed of an electrically conducting polymer composition obtained by specifying the viscosity of the oxidizing agent solution or the monomer solution.
The present invention even further relates to a solid electrolytic capacitor and a production method thereof, preferably comprising a solid electrolyte formed of an electroconducting (electrically conducting) polymer composition obtained by specifying the humidity in the polymerization of an oxidizing agent solution and a monomer solution in the solid electrolyte.
The present invention even further relates to a solid electrolytic capacitor, more specifically, a solid electrolytic capacitor in which the solid electrolyte formed on the outer surface of an anode body is an electrically conducting polymer containing a lamellar structure, wherein the solid electrolyte provided on the dielectric film formed on a valve acting metal occupies from 10 to 95% of the space within a pore of the electrode, so that the adhesive property between the solid electrolyte and the dielectric layer formed on a metal oxide film can be improved, high capacitance and low impedance can be realized, the leakage current can be improved, and good moisture resistance load characteristics and excellent heat resistance can be achieved.
The present invention also relates to a solid electrolytic capacitor, more specifically, a solid electrolytic capacitor in which the solid electrolyte formed on the outer surface of an anode body is an electrically conducting polymer containing a lamellar structure, wherein the solid electrolyte provided on the dielectric film formed on a valve acting metal covers 60% or more of the dielectric film, so that the adhesive property between the solid electrolyte and the dielectric layer formed on a metal oxide film can be improved, high capacitance and low impedance can be realized, and good moisture resistance load characteristics and excellent heat resistance can be achieved.
DESCRIPTION OF RELATED ART
A solid electrolytic capacitor is a device where an oxide dielectric film is formed on the surface of an anode substrate comprising a metal foil subjected to etching treatment or the like, a solid semiconductor layer (hereinafter referred to as a “solid electrolyte”) is formed as a counter electrode outside the dielectric layer, and an electrically conducting layer such as an electrically conducting paste is further formed thereon. The device is actually used as a product after completely sealing the entire device with epoxy resin or the like and leading out terminals from respective electrodes.
In recent years, with the progress toward digitized electrical equipment or personal computers capable of high speed processing, demands are increasing for a compact capacitor having a large capacitance or a capacitor showing low impedance in the high frequency region. As the compact capacitor having a large capacitance, electrolytic capacitors such as aluminum electrolytic capacitor and tantalum electrolytic capacitor are known. The aluminum electrolytic capacitor can be advantageously produced to have a large capacitance at a low cost but has a problem in that when an ion conducting liquid electrolyte is used as the electrolyte, high impedance results in the high frequency region and the capacitance decreases accompanying the evaporation of electrolytic solution with the elapse of time, and in addition, the temperature characteristics are bad. The tantalum electrolytic capacitor has a problem in that a manganese oxide is generally used as the electrolyte and since this manganese oxide is mainly produced by the thermal decomposition of manganese nitrate, the possibility of damage of the dielectric film at the thermal decomposition cannot be eliminated, and moreover, due to relatively high specific resistance of manganese oxide, the impedance is high in the high frequency region.
For the solid electrolyte, it is already known to use, for example, an inorganic semiconductor material such as manganese dioxide and lead dioxide, a TCNQ complex salt, an intrinsic electrically conducting polymer having an electric conductivity of from 10
−3
to 5×10
3
S/cm (JP-A-1-169914 (the term “JP-A” as used herein means an “unexamined published Japanese patent application” , corresponding to U.S. Pat. No. 4,803,596)) or an electrically conducting polymer such as &pgr;-conjugated polyaniline (see, JP-A-61-239617), polypyrrole (see, JP-A-61-240625), polythiophene derivative (see, JP-A-2-15611) or polyisothianaphthene (see, JP-A-62-118511). These electrically conducting polymers comprising a &pgr;-conjugated structure are mostly used as a composition containing a dopant. In recent years, not only the addition of a dopant but also a combination use with, for example, manganese dioxide (see, JP-B-6-101418 (the term “JP-B” as used herein means an “examined Japanese patent publication”) (corresponding to U.S. Pat. No. 4,959,753)) or filler (see, JP-A-9-320901) is employed.
In the case of using lead dioxide, precautions as to the environment are additionally required.
Capacitors using a TCNQ complex salt solid for the solid electrolyte have good heat fusion workability and excellent electric conductivity but are considered to show poor reliability in heat resistance (soldering heat resistance) at the solder joining because the TCNQ complex salt itself has a problem in heat resistance.
Capacitors using an electrically conducting polymer for the solid electrolyte do not have a dielectric film rupture problem and favored with a high impedance property but disadvantageously are deficient in heat resistance, thermal shock resistance and vibration resistance.
The electrically conducting polymer layer as a solid electrolyte has a high electric conductivity and is formed to cover throughout the inner surfaces of pores inside the cathode. At this time, for satisfying the fundamental characteristics of the capacitor, such as leakage current and heat resistance, the structure formed inside the foil pore and the coverage must be considered.
An example of the electrically conducting polymer formed article of which the structure is controlled is a sponge-like electrically conducting polymer formed article having a continuous phase of an electrically conducting polymer disclosed in JP-A-8-53566. This formed article is produced by a method of cooling a solvent-containing polyaniline or derivative thereof in any molding container to freeze the solvent and then removing the solvent, or a method of cooling a solution containing aniline or an aniline derivative as a monomer and a protonic acid/oxidizing agent to freeze the solvent and polymerizing the solution at a temperature lower than the melting point of the solvent.
In particular, as regarding the solid electrolyte provided on a dielectric film formed on a valve acting metal which is a constituent element of a capacitor, JP-A-7-122464 refers to a structure of an electrically conducting polymer formed within a microfine pore and discloses a tantalum solid electrolytic capacitor comprising a sintered body of tantalum powder, an oxide dielectric film formed on the surface of the sintered body and as a solid electrolyte, an electrically conducting polymer compound covering the oxide dielectric film. The tantalum solid electrolytic capacitor disclosed in this patent publication is constructed such that the electrically conducting polymer compound covers the oxide dielectric film while leaving a cavity in a pore constituting the surface of a sintered body and the electrically conducting polymer compound occupies, in terms of the vol
Furuta Yuji
Monden Ryuji
Ohata Hideki
Sakai Atsushi
Sawaguchi Toru
Jones Deborah
Showa Denko K.K.
Sughrue & Mion, PLLC
Xu Ling
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