JP2008004583A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having nearly equal equivalent series resistance characteristics as compared with before, and superior leakage current characteristics. <P>SOLUTION: The capacitor includes: a capacitor element, a positive electrode external terminal 9, a negative electrode external terminal 6, and a mold resin 7 for sealing the capacitor element. The capacitor element includes: an anode body 1, an element lead wire 8 led from the anode body 1, a dielectric layer 12 formed on the surface of the anode body 1, a solid electrolyte layer 2 that is formed on the dielectric layer 12 and comprises a conductive polymer layer, a graphite paste layer 3 formed on the solid electrolyte layer 2, and a silver paste layer 4 formed on the graphite paste layer 3. In the solid electrolytic capacitor, a layer 10 having higher density than that of the solid electrolyte layer 2 made of a conductive resin or an insulating resin is installed between the graphite paste layer 3 and the solid electrolyte layer 2 of a surface opposite to a surface where the element lead wire 8 of the anode body 1 is led. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor using a valve action metal such as aluminum or tantalum and a solid electrolyte layer.

  The basic structure of a conventional solid electrolytic capacitor is a layered structure in which a dielectric layer, a solid electrolyte layer, and a cathode are laminated on an anode. Generally, a metal having a valve action (valve action metal) is used as an anode. An oxide film (hereinafter referred to as a dielectric layer) is formed on the surface layer as a dielectric layer, a conductive polymer layer is formed thereon as a solid electrolyte layer, and a cathode layer such as graphite is formed thereon as a cathode. The structure is formed.

  Here, the valve metal is a metal capable of forming an oxide film whose thickness can be controlled by anodic oxidation, and corresponds to metals such as Nb, Al, Ta, Ti, Hf, and Zr. Two metals, Al (aluminum) and Ta (tantalum), are mainly used.

  Hereinafter, a conventional structure and manufacturing method of a tantalum solid electrolytic capacitor will be described with reference to the drawings.

  FIG. 3 is a cross-sectional view showing a conventional configuration example of a tantalum solid electrolytic capacitor. 3A is an overall cross-sectional view, and FIG. 3B is an enlarged cross-sectional view of a portion A in FIG. 3A showing the layer structure.

  As shown in FIG. 3, a conventional solid electrolytic capacitor using Ta includes an anode body 1 obtained by sintering Ta mixed powder, and an element that is embedded in one end of the anode body 1 and pulled out from one surface of the anode body 1. Contains lead 8, dielectric layer 12 formed by oxidation on the surface of anode body 1, and carbon powder formed on a portion other than the surface from which element lead 8 is drawn on dielectric layer 12. A capacitor element composed of a solid electrolyte layer 2 made of a conductive polymer layer, a graphite paste layer 3 formed on the solid electrolyte layer 2, and a silver paste layer 4 formed on the graphite paste layer 3. The anode external terminal 9 having one end connected to the element lead 8, the cathode external terminal 6 having one end connected to the silver paste layer 4 via the conductive adhesive 5, and the capacitor element are connected to the anode external terminal 9 and Cathode external terminal It consists molding resin 7 for sealing to expose the respective end of the.

  In solid electrolytic capacitors, reducing leakage current has become an important issue in practice, and various improvements have been made in the past, for example as shown in Patent Documents 1 and 2 below.

JP 2004-31875 A JP 2004-266171 A

  In the conventional solid electrolytic capacitor, the graphite paste layer 3 is formed using the highly permeable graphite paste as described above as a means for reducing the equivalent series resistance which is an important characteristic for the capacitor. However, there is a problem in that the particles in the graphite paste penetrate into cracks and low density portions of the solid electrolyte layer 2 made of the conductive polymer layer and contact the dielectric layer 12 to increase the leakage current of the capacitor characteristics. In this regard, no improvement method has been shown in the past including the above-mentioned patent documents.

  Usually, the method for forming the conductive polymer layer uses dipping. In order to pull the element lead wire 8 upward, the surface opposite to the surface from which the element lead wire 8 is drawn (part A in FIG. 3). The conductive polymer layer on the surface of the surface is liable to be pooled. For this reason, the conductive polymer film on this surface is particularly susceptible to cracking and density reduction.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a solid electrolytic capacitor having equivalent series resistance characteristics substantially equivalent to those of the prior art and excellent leakage current characteristics.

  In order to solve the above problems, a solid electrolytic capacitor according to the present invention includes an anode body formed by sintering a valve action metal powder, an element lead wire embedded in one end of the anode body and drawn from one surface of the anode body. A dielectric layer formed on the surface of the anode body, a solid electrolyte layer formed on at least a part of the dielectric layer, and a graphite paste layer formed on the solid electrolyte layer. A capacitor element, a silver paste layer formed on the graphite paste layer, at least two external terminals having one end connected to the element lead wire or the silver paste layer, and at least one end of the external terminal exposed. A solid electrolytic capacitor comprising a mold resin for sealing the capacitor element, wherein the solid electrolyte is partly disposed between the solid electrolyte layer and the graphite paste layer. It has established a high-density resin layer than solutions electrolyte layer.

  The solid electrolytic capacitor according to the present invention includes an anode body formed by sintering a valve action metal powder, an element lead wire embedded in one end of the anode body and drawn from one surface of the anode body, A capacitor element composed of a dielectric layer formed on the surface, a solid electrolyte layer formed on at least a part of the dielectric layer, and a graphite paste layer formed on the solid electrolyte layer; A silver paste layer formed on the graphite paste layer; at least two external terminals having one ends connected to the element lead wires or the silver paste layer; and at least one end of the external terminals exposed to expose the capacitor element. In the solid electrolytic capacitor comprising a mold resin to be sealed, the graphite paste layer is disposed in front of a portion between the solid electrolyte layer and the silver paste layer. It is replaced by a dense resin layer than the solid electrolyte layer.

  The resin layer having a higher density than the solid electrolyte layer may be formed on the surface of the anode body that faces the surface from which the element lead wire is drawn.

  The resin layer having a density higher than that of the solid electrolyte layer desirably has a density capable of preventing the penetration of fine particles of the graphite paste layer.

  The resin layer having a higher density than the solid electrolyte layer may have a high water and oil repellency, and may be made of a material having an effect of preventing adhesion of the graphite paste layer in the manufacturing process.

  The resin layer having a higher density than the solid electrolyte layer preferably covers 90% or more of the surface area of the surface of the anode body facing the surface from which the element lead wire is drawn.

  As described above, according to the present invention, a high-density layer is installed in a portion between the solid electrolyte layer and the graphite paste layer, particularly in a portion where the solid electrolyte layer is susceptible to cracking and density reduction, or the portion. By replacing the graphite paste layer with a high-density layer, the particles in the graphite paste are prevented from penetrating the conductive polymer layer and coming into contact with the dielectric layer. A solid electrolytic capacitor having excellent leakage current characteristics can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view showing an embodiment of a solid electrolytic capacitor according to the present invention. FIG. 1A is an overall cross-sectional view, and FIG. 1B is an enlarged cross-sectional view of a portion A in FIG.

  The solid electrolytic capacitor of this example is the same as the conventional solid electrolytic capacitor of FIG. 3, the anode body 1 formed by sintering Ta mixed powder, and one end embedded in the anode body 1 and pulled out from one surface of the anode body 1. Device lead 8, dielectric layer 12 formed by oxidation on the surface of anode body 1, and carbon powder formed on a portion other than the surface from which device lead 8 is drawn on dielectric layer 12 And the like, a solid electrolyte layer 2 composed of a conductive polymer layer containing, etc., a graphite paste layer 3 formed on the solid electrolyte layer 2, and a silver paste layer 4 formed on the graphite paste layer 3. A capacitor element, an anode external terminal 9 having one end connected to the element lead 8, a cathode external terminal 6 having one end connected to the silver paste layer 4 via a conductive adhesive 5, and the capacitor element outside the anode Terminal 9 and It consists molding resin 7 for sealing to expose the respective end of the cathode external terminal 6.

  However, in the present embodiment, the solid electrolyte is disposed between the solid electrolyte layer 2 and the graphite paste layer 3 on the surface (the surface having the A portion in FIG. 1) opposite to the surface from which the element lead wire 8 of the anode body 1 is drawn. The layer 10 having a higher density than the layer 2 is provided. As this high-density layer 10, a conductive resin or an insulating resin can be used.

  In the production of the solid electrolytic capacitor of this example, the dielectric layer 12 is formed by oxidation as in the prior art, and the solid electrolyte layer 2 made of a conductive polymer is formed thereon by immersion. In this embodiment, after that, a conductive resin or an insulating resin is attached to the surface facing the surface from which the element lead 8 is drawn, and the resin is dried. Further thereon, a graphite paste layer 3 and a silver paste layer 4 are formed. By using a conductive resin as the high-density layer 10, an equivalent series resistance characteristic equivalent to the conventional one can be obtained. As a result of actually making a prototype of the solid electrolytic capacitor of this example, the defect rate due to leakage current was reduced to 1/6 compared to the conventional case, and the increase in equivalent series resistance was about 8%.

  In order to further reduce the leakage current, a higher density insulating resin can be used as the high density layer 10. By using a high-density resin, even if the insulating resin layer is thin, the effect of preventing the penetration effect of the fine particles of the graphite paste can be obtained.

  As described above, in this embodiment, the leakage current can be reduced by inserting a high-density layer on the surface where the conductive polymer film constituting the solid electrolyte layer 2 is particularly susceptible to cracking and density reduction. it can. In this embodiment, the high-density layer 10 is provided on the entire surface opposite to the surface from which the element lead wires 8 are drawn. Can be improved.

  FIG. 2 is a sectional view showing a second embodiment of the solid electrolytic capacitor according to the present invention. 2A is an overall cross-sectional view, and FIG. 2B is an enlarged cross-sectional view of a portion A in FIG. 2A.

  Similarly to the conventional solid electrolytic capacitor of FIG. 3, the solid electrolytic capacitor of this example is also made of an anode body 1 obtained by sintering Ta mixed powder, and one end embedded in the anode body 1 and pulled out from one surface of the anode body 1. Device lead 8, dielectric layer 12 formed by oxidation on the surface of anode body 1, and carbon powder formed on a portion other than the surface from which device lead 8 is drawn on dielectric layer 12 A solid electrolyte layer 2 made of a conductive polymer layer containing, etc., a graphite paste layer 3 formed on the solid electrolyte layer 2, a silver paste layer 4 formed on the graphite paste layer 3, and an element lead wire 8, a capacitor element composed of an anode external terminal 9 having one end connected to 8; a cathode external terminal 6 having one end connected to the silver paste layer 4 via a conductive adhesive 5; Terminal 9 and It consists molding resin 7 for sealing to expose the respective end of the cathode external terminal 6.

  However, in this example, the portion between the solid electrolyte layer 2 and the silver paste layer 4 on the surface (surface with the A portion in FIG. 2) facing the surface from which the element lead wire 8 of the anode body 1 is drawn is There is no graphite paste layer 3, and a resin layer 11 having a higher density than the solid electrolyte layer 2 is provided instead.

  In the production of the solid electrolytic capacitor of this embodiment, as in the embodiment of FIG. 1, the dielectric layer 12 is formed by oxidation, and the solid electrolyte layer 2 made of a conductive polymer is formed thereon by immersion. Thereafter, a high-density resin is attached to the surface opposite to the surface from which the element lead 8 is drawn, and the resin is dried. However, in this embodiment, the high-density resin layer 11 is a silicone resin having high water and oil repellency. By using this silicone resin, formation of the graphite paste layer on this silicone resin can be prevented. That is, when the graphite paste layer is adhered by coating or the like, the adhesion is hindered only on the silicone resin due to its water and oil repellency. A silver paste layer 4 is formed on the high-density resin layer 11 made of the silicone resin and on the graphite paste layer 3 on the other surface.

  As described above, in the present embodiment, in particular, the conductive polymer film constituting the solid electrolyte layer 2 has a higher density than that of the solid electrolyte layer 2 except for the crack of the conductive polymer film and the graphite paste layer on which the density tends to decrease. By providing a simple layer, leakage current can be reduced.

  As mentioned above, although embodiment of this invention was described by the Example, it cannot be overemphasized that this invention is not restricted to the said Example. For example, depending on the equivalent series resistance characteristics and leakage current characteristics required for the solid electrolytic capacitor to which the present invention is applied, the area and area where the high-density layer is provided can be changed, and the material of the high-density layer is solid. Any material can be used as long as it can adhere to the electrolyte layer and has an effect of preventing the penetration effect of the fine particles of the graphite paste, and a resin material other than the above materials can be used.

Sectional drawing which shows one Example of the solid electrolytic capacitor by this invention. 1A is an overall cross-sectional view, and FIG. 1B is an enlarged cross-sectional view of a portion A in FIG. Sectional drawing which shows the 2nd Example of the solid electrolytic capacitor by this invention. 2A is an overall cross-sectional view, and FIG. 2B is an enlarged cross-sectional view of a portion A in FIG. 2A. Sectional drawing which shows the example of the conventional structure of a tantalum solid electrolytic capacitor. 3A is an overall cross-sectional view, and FIG. 3B is an enlarged cross-sectional view of a portion A in FIG. 3A showing a layer structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode body 2 Solid electrolyte layer 3 Graphite paste layer 4 Silver paste layer 5 Conductive adhesive 6 Cathode external terminal 7 Mold resin 8 Element lead 9 Anode external terminal 10 High-density layer 11 High-density resin layer 12 Dielectric layer

Claims (6)

  An anode body formed by sintering valve action metal powder, an element lead wire embedded in one end of the anode body and drawn from one surface of the anode body, and a dielectric layer formed on the surface of the anode body; And a solid electrolyte layer formed on at least a part of the dielectric layer, a graphite paste layer formed on the solid electrolyte layer, and a silver paste layer formed on the graphite paste layer. Solid electrolysis comprising a capacitor element, at least two external terminals having one end connected to the element lead wire or the silver paste layer, and a mold resin that seals the capacitor element by exposing at least one end of the external terminal In the capacitor, a solid layer characterized in that a resin layer having a higher density than the solid electrolyte layer is disposed in a part between the solid electrolyte layer and the graphite paste layer. Solutions capacitor.   An anode body formed by sintering valve action metal powder, an element lead wire embedded in one end of the anode body and drawn from one surface of the anode body, and a dielectric layer formed on the surface of the anode body; And a solid electrolyte layer formed on at least a part of the dielectric layer, a graphite paste layer formed on the solid electrolyte layer, and a silver paste layer formed on the graphite paste layer. Solid electrolysis comprising a capacitor element, at least two external terminals having one end connected to the element lead wire or the silver paste layer, and a mold resin that seals the capacitor element by exposing at least one end of the external terminal In the capacitor, the graphite paste layer is placed on a resin layer having a higher density than the solid electrolyte layer in a part between the solid electrolyte layer and the silver paste layer. The solid electrolytic capacitor characterized in that being gills.   3. The solid electrolytic capacitor according to claim 1, wherein the resin layer having a higher density than the solid electrolyte layer is formed on a surface of the anode body facing a surface from which the element lead wire is drawn.   4. The resin layer according to claim 1, wherein the resin layer having a higher density than the solid electrolyte layer has a density capable of preventing penetration of fine particles of the graphite paste layer. Solid electrolytic capacitor.   The resin layer having a density higher than that of the solid electrolyte layer is high in water repellency and oil repellency, and is made of a material having an effect of preventing adhesion of the graphite paste layer in a manufacturing process. 5. The solid electrolytic capacitor according to any one of 4   6. The resin layer having a density higher than that of the solid electrolyte layer covers 90% or more of the surface area of the surface of the anode body facing the surface from which the element lead wire is drawn out. The solid electrolytic capacitor according to any one of the above.

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