JP2007005354A - Laminated solid electrolytic capacitor, and formation method of negative electrode extraction layer in same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated solid electrolytic capacitor having low ESR and high yields by reducing the resistance between laminated capacitor elements. <P>SOLUTION: After a plurality of capacitor elements comprising valve action metal foil 1, a dielectric oxide layer 2 formed on the surface of the valve action metal foil, a solid electrolyte layer 3 successively formed on the surface of the dielectric oxide layer, a carbon layer 4, and a silver layer 5 are laminated via a conductive adhesive layer 6, the surface of the obtained laminated element is covered to form a silver layer 7 integrally. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer solid electrolytic capacitor and a method for forming a cathode lead layer in the multilayer solid electrolytic capacitor.

  In recent years, CPUs represented by Intel's Pentium (registered trademark) have increased in processing speed, and the operating clock has reached 3 GHz or more. Correspondence, that is, low ESR (equivalent series resistance) and low ESL (equivalent series inductance) have been strongly demanded. In addition, with the reduction in size and thickness of devices, there is a demand for lowering the height of capacitors.

  On the other hand, as a capacitor requiring low ESR, a solid electrolytic capacitor employing a conductive polymer having a low specific resistance as a solid electrolyte has been developed and widely used. The solid electrolytic capacitors using the conductive polymer as a solid electrolyte are roughly classified into a winding type using an aluminum foil as an anode, a laminated type, and a tantalum sintered body as an anode. It has characteristics.

  In general, a multilayer solid electrolytic capacitor is easy to cope with low height and low ESR, and after etching the valve action metal foil surface to form a porous body, an anode element having a dielectric oxide film formed on the surface, After laminating a plurality of capacitor elements formed of a solid electrolyte layer, a carbon layer, and a cathode lead layer made of a silver layer formed on a dielectric oxide film via a conductive adhesive layer, an external electrode is connected. Configured.

However, in the case of the above lamination method, the interfacial resistance between the capacitor elements becomes very large. Therefore, after laminating capacitor elements on which a solid electrolyte layer is formed, a carbon layer and a silver layer are sequentially formed so as to cover the laminated elements. Some of them constitute a laminated element (for example, see Patent Document 1).
JP 2004-281515 A

  However, in the method described in Patent Document 1, since the cathode extraction layer is formed by laminating after forming the solid electrolyte, particularly when the solid electrolyte is a conductive polymer having low mechanical strength, the leakage current of the capacitor element increases. Therefore, there is a problem of lowering the yield.

Because of the problems as described above, a multilayer solid electrolytic capacitor having a structure capable of low ESR and high yield has been demanded.
Another object of the present invention is to provide a method for forming a cathode lead layer useful for reducing the ESR of a multilayer solid electrolytic capacitor.

The multilayer solid electrolytic capacitor of the present invention includes a valve action metal foil, a dielectric oxide film formed on the surface of the valve action metal foil, a solid electrolyte layer sequentially formed on the surface of the dielectric oxide film, carbon A plurality of capacitor elements composed of a layer and a silver layer are laminated via a conductive adhesive layer to form a laminated element, and the surface of the laminated element is covered with silver paste and integrated. Such a multilayer solid electrolytic capacitor is made of a dielectric oxide film formed on the surface of a valve-acting metal foil, and a plurality of capacitor elements in which a solid electrolyte layer, a carbon layer, and a silver layer are sequentially formed are conductive. It is manufactured by forming a conductive silver layer so as to cover and integrate the surface of the obtained laminated element after lamination through an adhesive layer.
In the multilayer solid electrolytic capacitor having the above-mentioned characteristics, the valve-acting metal foil is selected from the group consisting of tantalum foil, niobium foil, and aluminum foil. But there is.

Furthermore, the present invention is a method for forming a cathode lead layer capable of achieving a low equivalent series resistance (low ESR) of a multilayer solid electrolytic capacitor, and this method comprises a valve action metal foil. A step of manufacturing a plurality of capacitor elements in which a dielectric oxide film is formed on the surface, and a solid electrolyte layer, a carbon layer, and a silver layer are sequentially formed on the surface of the dielectric oxide film; and the plurality of capacitors The element is laminated through a conductive adhesive layer, and the laminated element is manufactured, and the surface of the laminated element is covered with silver paste and integrated to draw out the cathode from all the laminated capacitor elements. Forming a cathode lead layer that can be formed.
By the above cathode lead layer forming method of the present invention, the connection resistance of the edge portion of the capacitor element that cannot be covered with the conductive adhesive for joining the capacitor element can be reduced to the maximum, and the interface resistance between the capacitor elements can be reduced. Since it can be lowered, it is possible to reduce the ESR of the multilayer capacitor.

  Further, in the cathode lead layer forming method of the present invention, the capacitor element is laminated after the silver layer is formed, so that damage to the dielectric oxide film due to mechanical stress can be prevented, and the yield of the product is increased. be able to.

The conductive silver paste applied to the laminated element may be a general one using a binder of epoxy resin, acrylic resin, rubber resin, etc., but applied to the capacitor element before lamination. It is desirable to use the same material.
Further, the conductive silver layer formed on the laminated element may be formed by a known method such as drying after dipping the capacitor element in a silver paste.

In the case of the multilayer solid electrolytic capacitor of the present invention, since the conductive silver layer is formed so as to cover all the capacitor elements after lamination, the cathode can be efficiently drawn out from all the multilayer elements with low resistance. In addition, since the connection resistance of the edge portion of the capacitor element that cannot be covered only with the conductive adhesive can be lowered, the ESR of the multilayer solid electrolytic capacitor can be reduced. In addition, since the multilayer solid electrolytic capacitor of the present invention has a structure in which capacitor elements after silver layer formation are laminated, damage to the dielectric oxide film due to mechanical stress is suppressed, and the leakage current failure rate is reduced. It can also be reduced.
In addition, the method for forming the cathode lead layer in the production of the multilayer solid electrolytic capacitor of the present invention is to efficiently form all of the conductive silver layers so as to cover all the capacitor elements after the lamination, and efficiently with a low resistance. Since the cathode can be drawn out from the device and the connection resistance of the edge portion of the capacitor device that cannot be covered only with the conductive adhesive can be lowered, it is useful for manufacturing a multilayer solid electrolytic capacitor having a lower ESR. is there. In addition, since the capacitor elements after the formation of the silver layer are stacked, damage to the dielectric oxide film due to mechanical stress is suppressed, and the leakage current defect rate can be reduced.

Example 1
Hereinafter, preferred embodiments of the multilayer solid electrolytic capacitor of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a preferred example of the cross-sectional structure of the multilayer element in the multilayer solid electrolytic capacitor of the present invention, and FIG. 5 is an overview of the multilayer element.

  As the valve action metal foil 1 in the multilayer solid electrolytic capacitor of the present invention illustrated in FIGS. 1 and 5, an aluminum foil subjected to etching treatment was used. A dielectric oxide film 2 was formed on the cathode layer forming portion on the surface of the aluminum foil to form an anode element. And in order to prevent the short circuit of an anode and a cathode, after forming the insulating layer 8, the solid electrolyte layer 3 was formed. Here, a conductive polymer made of polythiophene was used as the solid electrolyte. After that, after sequentially forming the carbon layer 4 and the silver layer 5 to constitute the capacitor element, as shown in FIG. 1, two capacitor elements are laminated via the conductive adhesive layer 6, and the laminated element is After dipping in the conductive silver paste, it was dried to form a silver layer (cathode lead layer 7) so as to surround the periphery of the laminated element. Here, a silver paste containing an epoxy resin was used before and after lamination.

  After joining the foil on the anode side of the laminated element obtained above by resistance welding with the external electrode, after joining the cathode side and external electrode on which the silver layer was formed with a conductive adhesive, after packaging with an epoxy resin, Aging was performed to obtain a multilayer solid electrolytic capacitor of the present invention having a rated voltage of 6.3 V and a rated capacity of 100 uF.

(Comparative Example 1)
Two capacitor elements formed by forming the carbon layer 4 and the silver layer 5 by the same method as in Example 1 were laminated through the conductive adhesive layer 6, and then external electrode terminals were formed in the same manner as in Example 1. The structure, package, and aging were performed to obtain a multilayer solid electrolytic capacitor. FIG. 2 shows a cross-sectional structure of the multilayer solid electrolytic capacitor manufactured in Comparative Example 1.

(Comparative Example 2)
Two capacitor elements formed up to the solid electrolyte layer 3 by the same method as in Example 1 were laminated, and the carbon layer 4 and the silver layer 7 were formed so as to cover the laminated element. Thereafter, through the same process as in Example 1, a multilayer solid electrolytic capacitor was obtained. FIG. 3 shows a cross-sectional structure of the multilayer solid electrolytic capacitor manufactured in Comparative Example 2.

(Comparative Example 3)
Two capacitor elements formed up to the carbon layer 4 by the same method as in Example 1 were laminated, and a silver layer 7 was formed so as to cover the laminated element. Thereafter, through the same process as in Example 1, a multilayer solid electrolytic capacitor was obtained. FIG. 4 shows a cross-sectional structure of the multilayer solid electrolytic capacitor manufactured in Comparative Example 3.

  Table 1 below shows the ESR value and the leakage current defect rate of the multilayer solid electrolytic capacitors produced in the above Examples and Comparative Examples 1 to 3.

From the experimental results of Table 1, the multilayer solid electrolytic capacitors obtained in the examples have lower ESR and lower leakage current failure rate than the multilayer solid electrolytic capacitors of Comparative Examples 1 to 3 (high yield) )

  As shown in FIG. 1, the ESR can be reduced in this way by forming the silver layer 7 so as to cover the stacked elements, thereby reducing the interfacial resistance between the capacitor elements, and The edge portion of the capacitor element that easily loses the flow of current is also covered with the silver layer 7, which is due to the effect of reducing the resistance.

  The reason why the leakage current defect rate is reduced is due to the effect that the dielectric oxide film 2 can be prevented from being damaged by mechanical stress because the silver layer 5 containing resin is laminated after being formed.

  In the above embodiment, aluminum foil was used for the valve action metal foil. However, the same effect can be obtained by using a tantalum foil, niobium foil, or an element formed by sintering valve metal powder into a sheet shape. was gotten.

  In the above embodiment, the silver layer is formed by dipping on the laminated element, but the same effect can be obtained by using other known forming methods such as spraying.

  Further, although silver paste containing an epoxy resin is used in the examples, the same effect can be obtained by using other commonly used conductive silver pastes such as acrylic resin and rubber resin.

  In the above examples, a conductive polymer made of polythiophene was used as the solid electrolyte, but the same effect can be obtained by using other known conductive polymers such as polypyrrole and polyaniline, and the absolute value of ESR. However, it was confirmed that the same effect was obtained even when the manganese dioxide layer was used as the solid electrolyte.

  Furthermore, in the above embodiment, the number of stacked capacitor elements is two, but the same effect can be obtained even when two or more capacitor elements are stacked.

It is sectional drawing of the multilayer type solid electrolytic capacitor in Example 1 of this invention. 6 is a cross-sectional view of a multilayer solid electrolytic capacitor in Comparative Example 1. FIG. 6 is a cross-sectional view of a multilayer solid electrolytic capacitor in Comparative Example 2. FIG. 6 is a cross-sectional view of a multilayer solid electrolytic capacitor in Comparative Example 3. FIG. It is a general-view figure of a lamination element.

Explanation of symbols

1 Valve metal foil (aluminum foil)
2 Dielectric oxide film 3 Solid electrolyte layer 4 Carbon layer 5 Silver layer 6 Conductive adhesive layer 7 Cathode extraction layer (silver layer applied after lamination)
8 Insulation layer

Claims (3)

A capacitor element comprising a valve metal foil, a dielectric oxide film formed on the surface of the valve metal foil, and a solid electrolyte layer, a carbon layer, and a silver layer sequentially formed on the surface of the dielectric oxide film. A multilayer solid electrolytic capacitor characterized in that a plurality of sheets are laminated via a conductive adhesive layer to form a laminated element, and the surface of the laminated element is covered and integrated with a silver paste. 2. The multilayer solid electrolytic capacitor according to claim 1, wherein the valve metal foil is selected from the group consisting of a tantalum foil, a niobium foil, and an aluminum foil. A method for forming a cathode lead layer of a multilayer solid electrolytic capacitor,
In this method, a dielectric oxide film is formed on the surface of the valve action metal foil, and a solid electrolyte layer, a carbon layer, and a silver layer are sequentially formed on the surface of the dielectric oxide film to produce a plurality of capacitor elements. A step of laminating a plurality of capacitor elements through a conductive adhesive layer to produce a laminated element, and covering and integrating the surface of the laminated element with a silver paste, Forming a cathode lead layer capable of pulling out the cathode from the capacitor element, and forming a cathode lead layer in a multilayer solid electrolytic capacitor.