Metal working – Barrier layer or semiconductor device making – Barrier layer device making
Reexamination Certificate
2001-07-05
2003-08-12
Pert, Evan (Department: 2829)
Metal working
Barrier layer or semiconductor device making
Barrier layer device making
C029S025420
Reexamination Certificate
active
06605127
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing an aluminum solid electrolyte capacitor whereby a product of high reliability can be mass-produced.
2. Description of the Related Art
In the aluminum electrolytic capacitors which are generally employed in large quantity, the positive electrode foil is constituted by etching aluminum foil to increase its surface area and generating an oxide film thereon by subjecting this to chemical conversion treatment; for the negative electrode foil, untreated aluminum foil is employed and an element (hereinbelow termed “coiled element”) is constituted by coiling the positive electrode foil and negative electrode foil with a separator such as Manila paper therebetween; the element is completed by impregnating with liquid electrolyte (for the essentials, see Laid-open Japanese Patent Application Publication No. H. 8-78287).
In recent years, aluminum solid electrolyte capacitors have been commercialized in which a conductive polymer material is employed as electrolyte instead of the liquid electrolyte in an aluminum electrolytic capacitor as aforesaid.
The solid electrolyte in an aluminum solid electrolyte capacitor has the characteristic advantage that its electrical conductivity is higher than that of the liquid electrolyte in an aluminum electrolytic capacitor, so losses are smaller and the frequency characteristic and temperature characteristics are excellent.
However, in contrast to aluminum electrolytic capacitors, the oxide film on the positive electrode has no self-repairing action, so if a defect is produced in the oxide film on the positive electrode, there is a high probability of a short-circuit mode fault being produced.
Usually, when a short-circuit occurs in a capacitor employed in electrical equipment, an abnormal current flows; this involves a risk of causing a fire in the electronic equipment. Accordingly, in the case of aluminum solid electrolyte capacitors, capacitors are employed in which the voltage-withstanding ability of the oxide film on the positive electrode is set to be about three times higher than in an aluminum electrolytic capacitors, but this causes the capacity to be reduced to about ⅓.
Apart from this problem, when an aluminum solid electrolyte capacitor is manufactured by applying the prior art (see for example Laid-open Japanese Patent Application Publication No. H. 10-50558 or Laid-open Japanese Patent Application Publication No. H. 10-50560), the oxide film on the positive electrode is subjected to a chemical conversion treatment again (“repeat chemical conversion” treatment) after the coiled element is produced, and before it is incorporated and fixed in the case.
FIG. 7
is a flow chart given in explanation of the steps involved in manufacturing a prior art aluminum solid electrolyte capacitor. First of all, in a first step, a coiled element is produced comprising a positive electrode foil formed with an oxide film by chemical conversion, a separator, and a negative electrode foil; in a second step, the oxide film of the positive electrode foil is subjected to repeat chemical conversion to repair any defects; in a third step, it is subjected to washing; in a fourth step, heat treatment is performed; in a fifth step, a solid electrolyte is generated; in a sixth step, this is assembled into the case; in a seventh step, the coiled element and case are stuck together by epoxy resin and curing is performed; in an eighth step, ageing is performed; and in a ninth step inspection is carried out.
In the process of
FIG. 7
mentioned above, there is the problem that, even if the oxide film on the positive electrode is perfectly formed by the repeat conversion of the second step, if any kind of stress acts on the coiled element during the period from the subsequent third step to the seventh step i.e. from the washing as far as the incorporation in the case, cracks can easily be generated in the oxide film on the positive electrode.
Specifically, when the coiled element is incorporated in the case, until adhesion and curing of the epoxy resin have been achieved, the lead terminals of the coiled element can move easily and also the coiled element itself is weak and easily deformed by external force, so handling in such a way that no stress acts on the electrode foil is difficult to achieve and furthermore the oxide film on the positive electrode is as extremely thin as 1.3 (nm/V), so even if the utmost care is taken in each step, the defect rate is high and may reach 5 (%) to 50 (%); thus the reliability is low.
SUMMARY OF THE INVENTION
According to the present invention, a sequence of steps is adopted that makes it possible to avoid application of stress to the capacitor body (for example coiled element) when manufacturing an aluminum solid electrolyte capacitor and there are provided means that make it possible to execute these steps, thereby enabling mass production of aluminum solid electrolyte capacitors of high reliability and excellent quality.
The basis of the present invention lies in that, at the stage where the capacitor body for the aluminum solid electrolyte capacitor is completed, its assembling into the case is immediately performed, together with curing and adhesion with resin, thereby fixing the coiled element at the initial stage of the steps and preventing stress from being applied to the oxide film on the positive electrode; in order to perform such a step, a case is required having an aperture that makes possible performance of the various processing steps after curing and adhesion of the resin around the lead terminals in the coiled element; such a case is disclosed in Japanese Patent Application Number H. 7-135116 (Laid-open Japanese Patent Application Number H. 8-78287).
FIG. 1
is a flow chart given in explanation of an example of the steps involved in manufacturing an aluminum solid electrolyte capacitor according to the present invention. In the first step, a coiled element comprising a positive electrode foil with oxide film formed thereon by chemical conversion, a separator and an electrode foil is produced; in the second step, the coiled element is assembled through the first aperture in a case having a first aperture and a second aperture; in the third step, adhesion of the coiled element and the case is effected at the first aperture with an epoxy resin, followed by its curing; in the fourth step, defects are repaired by repeat chemical conversion of the oxide film of the positive electrode foil; in the fifth step, washing is performed; in the sixth step, heat treatment is carried out; in the seventh step the solid electrolyte is generated; in the eighth step ageing is performed; in the ninth step the second aperture is sealed; and the product is completed by inspection in the tenth step. The chief varieties of aluminum solid electrolyte capacitors are capacitors in which a coiled element is employed as described above and capacitors in which the electrodes are of a flat plate shape; including these cases, parts which are present in the case are collectively called the “capacitor body”; in this construction, a portion of the lead terminals is also included in the “capacitor body”.
As described above, according to a first aspect of the present invention, a method of manufacturing an aluminum solid electrolyte capacitor comprises:
a step of fixing a capacitor body (for example capacitor body
1
of
FIG. 2
, to be described) within a case (for example case
3
of
FIG. 2
, to be described) having one or more apertures; and
a step of generating solid electrolyte by introducing a raw material of solid electrolyte from any of these apertures, coating or impregnating the capacitor body therewith, and inducing an oxidative polymerization reaction.
The aforesaid one or more apertures can be employed as introduction ports when the capacitor body is arranged within the case. If this is done, it is important that the aperture is of a size that is capable of allowing passage of the capacitor body. However, this is not necessa
Shoei Co., LTD
Staas & Halsey , LLP
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