JP2007180075A - Solid-state electrolytic capacitor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state electrolytic capacitor, having a large capacitance with respect to the outer package volume by making it into a structure such that it does not have any anode lead wires extruding from an anode body, and to provide its manufacturing method. <P>SOLUTION: The solid-state electrolytic capacitor 10 includes a capacitor element formed with an oxide coating layer, a solid-state electrolytic layer, and a cathode extraction layer, in this order, on the surface of the anode body made by pressure-molding and sintering valve action metal powder. The solid-state electrolytic capacitor 10 comprises an anode body (porous portion 21) formed of powder of a first valve actio metal, such as tantalum, and a non-porous portion 20 formed at least on one side of the anode body. The non-porous portion 20 consists of a non-porous portion, formed of powder of another valve action metal, such as niobium, which has a lower melting point than the first valve action metal, or of the powder of the first valve action metal having a finer grain diameter than the one used for the porous anode body 21, and an anode terminal 12b so formed as to coat at least the surface of the non-porous portion 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and more particularly to a structure of a solid electrolytic capacitor that enables a reduction in size and capacity, and a method for manufacturing the same.

A capacitor element 11 using a valve action metal powder such as tantalum conventionally used has a structure in which an anode lead wire 1 is embedded as shown in FIG. Therefore, all of the part cannot be removed. Therefore, as shown in FIG. 8, 1) the cathode lead layer 5 of the capacitor element 11 and the anode lead wire 1 are connected to a pair of left and right anodes and cathode lead frames 8a and 8b, respectively, and the whole is made of synthetic resin or the like. It was set as the structure covered with the mold 9, or 2) it was set as the structure which gives a simple exterior with a synthetic resin (for example, refer patent document 1).
However, in the solid electrolytic capacitor having the above structure, the capacitor element 11 is covered with the mold 9 made of a synthetic resin or the like in the state including 1) the cathode lead layer 5 and the anode lead wire 1 or 2) Since the anode lead wire 1 is covered with a synthetic resin or the like, the volume efficiency is low because the anode lead wire 1 is included, that is, the capacitance of the capacitor element with respect to the outer volume is reduced. It was.

  As a technique for increasing the volumetric efficiency, a metal particle is solidified on one end face of a chip piece obtained by sintering a powder of valve action metal (tantalum or the like) used as an anode material of a capacitor element into a porous shape without gaps. A method for forming a porous portion has been proposed (see, for example, Patent Document 2).

Here, a manufacturing process of a general solid electrolytic capacitor made of valve action metal powder such as tantalum will be described with reference to the attached FIGS. 5 to 8. 1) Valve action metal powder made of tantalum or the like is pressurized. At the same time as molding into a predetermined shape, the first step of embedding the anode lead wire 1 in this pressure-molded body, 2) the obtained pressure-molded body is sintered under high vacuum to obtain a physical bond, Second step for forming anode body 2 3) An oxide film layer 3 serving as a dielectric is formed on the surface of anode body 2 by anodic oxidation (described later) performed in the embodiment illustrated in FIG. Three steps, 4) As illustrated in FIG. 7, the oxide film layer is formed by immersing the chemical formation 2 ′ in a second treatment liquid (described later) such as an aqueous manganese nitrate solution or polymerizing a conductive polymer. A fourth step of forming a conductive material (solid electrolyte layer 4) on 3; ) Fifth step of forming the cathode lead layer 5 for connecting the conductive substance and the external terminal with low resistance, 6) Sixth step of bonding with the external terminal (8a, 8b, etc.) and covering with the synthetic resin or the like (See FIG. 8).
5 is a side view of the capacitor element of the solid electrolytic capacitor according to the conventional example, and FIG. 6 is an oxide film formed with a first treatment liquid such as an aqueous phosphoric acid solution on the anode body in manufacturing the solid electrolytic capacitor according to the conventional example. FIG. 7 is a diagram showing a state in which a process for forming a layer is performed. FIG. 7 is a process for forming a solid electrolyte layer using a second processing solution such as manganese nitrate after the process shown in FIG. FIG. 8 is a side sectional view of a solid electrolytic capacitor (50) according to a conventional example.
As shown in FIG. 6, generally, the oxide film layer 3 is formed to a certain height T of the anode lead wire 1 (see, for example, Patent Document 2). At this time, since the oxide film layer 3 is formed from the pressure molded body to the surface of the anode lead wire 1, the anode side which is the tip side of the anode lead wire 1, and a solid electrolyte made of manganese dioxide or a conductive polymer It is reliably insulated from the cathode side which is the layer 4.

However, in order to apply the technique described in Patent Document 2 as a method for increasing volumetric efficiency, it is necessary to separately insert a step of providing a non-porous portion on one end face of the anode body 2 in the second step. (Partial heating by laser irradiation, etc .; see the same document [0016]), there is a problem that the loss is large in terms of cost and time.
Japanese Utility Model Publication No. 53-72161 Japanese Patent No. 3294362

  The present invention solves the above-described problems, and an object of the present invention is to provide a solid electrolytic capacitor having a high volumetric efficiency and a manufacturing method thereof without newly inserting a new process.

As a result of various studies to solve the above problems, the present inventors have found that the above-described problems can be solved by adopting the following means, and have completed the present invention.
That is, the inventor of the present application: 1) In the first step, the melting point is lower than that of tantalum such as niobium on at least one side of the surface of the anode body made of the first valve metal powder such as tantalum. By arranging the valve action metal powder with a larger shrinkage like other valve action metal powder or finer tantalum valve action metal,
2) An anode body made of a powder of a tantalum valve metal first pressure-molded with another valve metal having a melting point lower than that of tantalum or a finer tantalum valve metal by sintering in the subsequent second step. 3) When the conductive material (solid electrolyte layer) is formed in the fourth step, the portion is impregnated with the conductive material or the conductive material precursor. Therefore, the present invention was completed by finding that the part can be used as it is as the anode lead part.

The solid electrolytic capacitor of the present invention capable of solving the above problems is as follows. (1) An oxide film layer, a solid electrolyte layer, and a cathode lead layer are formed on the surface of an anode body obtained by pressure forming and sintering a valve action metal powder. Is a solid electrolytic capacitor having capacitor elements sequentially formed,
A porous anode body made of a powder of a first valve metal, and a non-porous part provided on at least one side of the porous anode body, wherein the non-porous part is made of the first valve metal A non-porous portion made of another valve action metal powder having a low melting point, or a first valve action metal powder having a particle size finer than that forming the porous anode body, and the non-porous portion And an anode terminal part formed by covering at least the surface.

In addition, the method for producing a solid electrolytic capacitor of the present invention capable of solving the above-described problems includes (2) an oxide film layer, a solid electrolyte on the surface of an anode body obtained by pressure forming and sintering a valve action metal powder. A method for producing a solid electrolytic capacitor having a capacitor element in which a layer and a cathode lead layer are sequentially formed,
A step of pressure-molding a powder of the first valve metal that becomes a porous anode body, and at least one side of the porous anode body has a melting point lower than that of the first valve metal that becomes a non-porous part Secondary pressurization in which another valve action metal powder or a first valve action metal powder having a finer particle diameter than that forming the porous anode body is pressure-molded together with the porous anode body. Sintering the molded body after the molding step and the second pressure molding step, the first powder having a finer particle diameter than that of the other valve metal powder or the porous anode body. A step of eliminating the porosity of the powder of the valve metal to obtain a non-porous portion, and a step of covering the surface of the obtained non-porous portion to form an anode terminal portion. It is what.
(3) Preferably, the first valve metal powder is made of tantalum, and the other valve metal powder is made of niobium.

According to the present invention, it is possible to provide a solid electrolytic capacitor having a high volumetric efficiency of the capacitor element when packaged. Therefore, it is possible to provide a solid electrolytic capacitor having a larger capacitance with respect to the exterior volume than before.
Further, according to the method of the present invention, it is possible to provide a solid electrolytic capacitor having a high volumetric efficiency of the capacitor element when packaged and a method for manufacturing the same without adding a new process.

  Hereinafter, based on an accompanying drawing, one embodiment of the solid electrolytic capacitor concerning the present invention and its manufacturing method is described. 1A and 1B show an embodiment of a solid electrolytic capacitor according to the present invention, where FIG. 1A is a side sectional view and FIG. 1B is an enlarged view showing a laminated state. FIG. 2 is an example of the third step, and shows a state in which the sintered anode body is subjected to a treatment for forming an oxide film layer with the first treatment liquid, and FIG. 3 shows the fourth step. FIG. 4 is a diagram illustrating a state in which an impregnation treatment for forming a solid electrolyte layer is further performed with a second treatment liquid after the formation treatment of the oxide film layer shown in FIG. It is a figure which shows the process process by the other method of forming a solid electrolyte layer with the process liquid of.

FIG. 1 (a) is a side sectional view showing an embodiment of a solid electrolytic capacitor according to the present invention. In this embodiment, an anode body is manufactured by appropriately using tantalum or niobium metal powder, A solid electrolytic capacitor is completed through several steps.
As shown in an enlarged view of the laminated state in FIG. 2B, the tantalum solid electrolytic capacitor 1 according to this embodiment uses tantalum powder as a valve metal, and after molding and sintering, the surface of the anode body 2 In addition, an oxide film layer 3 serving as a dielectric (insulator) is formed by chemical conversion treatment, and a solid electrolyte layer 4 (made of manganese dioxide or a conductive polymer) is provided on the outside as a cathode.
Subsequently, similarly to a general solid electrolytic capacitor, a cathode lead layer 5 composed of a carbon layer and a silver layer is sequentially formed on the solid electrolyte layer 4 which is also a cathode of the present embodiment, and a cathode terminal is formed from a part thereof. 12a is pulled out. As the exterior of the solid electrolytic capacitor 10, there are various forms such as a resin dip, a resin mold, and a metal case. In this embodiment, the exterior resin 6 is further formed on the cathode lead layer 5.

Further, in this embodiment, at least one side of a porous anode body made of pressure-formed tantalum valve metal powder has a valve metal powder having a melting point lower than that of the tantalum valve metal, or finer tantalum. The powder of valve action metal is arranged, and the one side is made non-porous by sintering. As a result, the non-porous portion 20 is not impregnated with the second treatment liquid such as manganese nitrate or the polymerization treatment liquid used when forming the solid electrolyte layer 4, so that no cathode is formed.
Therefore, according to the configuration of the present embodiment, the non-porous portion 20 can be newly used as the anode lead portion instead of the anode lead wire after the third step.
Initially, the anode lead wire 1 is embedded in the anode body 2, but in the present embodiment, it is cut in a subsequent process (see FIG. 1A). Details of the manufacturing process will be described in detail in the following examples.

  In the following, the material forming the non-porous portion is 1) niobium powder (Example 1), and 2) tantalum powder having a finer particle diameter than the powder forming the porous anode body (Example 2). The solid electrolytic capacitor and the manufacturing method thereof according to the present invention will be described separately. In addition, a comparative example corresponding to Examples 1 and 2 will be described, and the effects of the present invention will be specifically compared and examined using these three factors.

Example 1
First, Example 1 of the present invention will be described. In this example, the material (first valve action metal) forming the porous anode body [the part indicated by reference numeral 2 in FIG. 1] is tantalum powder, and the non-porous portion [indicated by reference numeral 20 in FIG. This is an example in which the material forming the [part] is niobium powder as another valve metal.

[Description of manufacturing process]
(1) First Step—Method for Producing Press Molded Body First, 30,000 μF · V / g (= 30 kCV) tantalum powder was used as the material of the anode body of this example. In this example, a granulated powder for pressure molding was prepared by mixing 0.5 wt% of a binder for enhancing moldability with this valve action metal powder. In this step, primary pressure molding is performed using this granulated powder. After that, only the upper end surface of the molding die is opened, niobium powder is supplied from the opening, and then the mouth is closed to perform secondary pressure molding. As a result, an anode body 2 in which the anode lead wire 1 was embedded was obtained.
In addition, the range of the preferable CV value of the tantalum which is a 1st valve action metal is about 30,000 CV-about 200,000 CV. In addition, a preferable particle size range of niobium, which is another valve action metal constituting the non-porous portion 20, is about 1 μm to about 15 μm.

(2) Second Step—Method for Producing Anode Body By sintering the secondary pressure-formed body of (1) above at 1,475 ° C. for 20 minutes under high vacuum (about 10 ⁻³ Pa or less), At the same time as obtaining physical connection between tantalum, niobium, and both metal powders, an anode body 2 having a niobium powder portion (non-porous portion 20) that lost porosity by being greatly shrunk was obtained (hereinafter referred to as “anode body 2”) Then, the pressure-formed body after sintering is referred to as an anode body 2).

(3) Third Step—Formation of Dielectric Oxide Film Layer In order to form the oxide film layer 3 on the surface of the anode body 2 obtained in the above (2), an oxide layer functioning as a dielectric was formed by anodic oxidation. . A 1.0 vol% phosphoric acid aqueous solution was used as an anodic oxidation electrolyte solution (first treatment solution, hereinafter referred to as a chemical conversion solution) used at this time.
In this example, this process was performed in the manner as shown in FIG. At this time, the anode body 2 is completely immersed in the first treatment liquid (chemical conversion liquid) F filled in the container C except for a part of the anode lead wire 1. Anodization was carried out by keeping this chemical conversion solution at 40 ° C., setting the current density per anode body to 35 mA / piece, and the ultimate voltage to 12.1 V. Then, after the anodic oxidation voltage reached 12.1 V, the voltage application state was maintained for 4 hours to form the oxide film layer 3 (hereinafter, the anodic body 2 obtained by anodic oxidation is referred to as a chemical formation 2 ′).

(4) Fourth Step—Formation of Solid Electrolyte Layer Corresponding to the anode in the porous portion 21 (the portion excluding the non-porous portion 20 in the anode body 2) made of tantalum of the chemical formed body 2 ′ obtained in the above (3) As the counter electrode, the solid electrolyte layer 4 was impregnated in a monomer solution containing 3,4-ethylenedioxythiophene in this example, and a conductive polymer made of polyethylenedioxythiophene was formed by polymerization. The state of the solid electrolyte layer 4 formed on the chemical conversion body 2 ′ is shown in FIG.

(5) Fifth Step—Formation of Cathode Lead Layer Similarly, the cathode lead layer 5 made of carbon and silver was formed on the porous portion 21 after the solid electrolyte layer 4 of (4) was formed. This is also shown in FIG.

(6) Sixth step—formation / exterior of external terminals The oxide film on the end face on the non-porous part 20 side in the capacitor element after the formation of the cathode lead layer 5 of (5) above is removed with a laser (see FIG. 1). Thereafter, as shown in FIG. 1, the portion excluding the anode side end face and the opposing cathode side end face was coated with a covering material made of a synthetic resin. Thereafter, the anode lead wire 1 is cut from the base, and both end surfaces not covered with the covering material are coated with tin and solder to form the cathode and anode terminal portions 12a and 12b. Finally, as shown in FIG. A solid electrolytic capacitor 10 having a side sectional shape was obtained.

(Example 2)
The niobium powder used for forming the non-porous portion 20 in Example 1 is made of the same material and process as Example 1 except that the tantalum powder is 100,000 CV / g (= 100 kCV). A solid electrolytic capacitor 10 was produced. In the present embodiment, the tantalum powder used to form the non-porous portion 20 is finer than the tantalum powder that forms the porous portion 21.
When the non-porous portion 20 is made of the same metal as the first valve action metal as in this example, the preferable CV value range is about 100,000 CV to about 250,000 CV.

(Comparative Example 1)
Next, as a conventional example, a solid electrolytic capacitor 50 having a structure shown in FIG. 8 was produced using the granulated powder used in the production of the anode body 2 according to Example 1 described above. At this time, the anode body 2 in which the anode lead wire 1 is embedded is prepared so as to have the same size as that of the first embodiment, and this is subjected to chemical conversion (anodic oxidation) under the same conditions as in the first embodiment. It was. Thereafter, in this specification, the solid electrolytic capacitor 50 having the structure shown in FIG. 8 was manufactured by a conventionally known method described with reference to FIGS.

(Comparison of the three)
As described above, according to the present invention, it is possible to provide a solid electrolytic capacitor having a high volumetric efficiency of the capacitor element when packaged. Therefore, in order to express the effect concretely, a comparative study was conducted on the magnitude of the capacitance with respect to the unit outer volume of the solid electrolytic capacitors produced in Example 1, Example 2 and Comparative Example 1. Table 1 shows the size of the capacitance with respect to the unit outer volume of the solid electrolytic capacitors produced in Example 1, Example 2 and Comparative Example 1.

According to the present invention, at least one side of the anode body 2 made of tantalum valve metal powder, 1) another valve metal (niobium in Example 1) which is a valve metal having a melting point lower than that of tantalum, or 2 ) By disposing a finer tantalum valve metal (Example 2) of the valve metal having a larger shrinkage than the powder forming the porous portion 21, a sintering process at a high temperature continues to 1 Porosity can be lost by shrinking niobium valve metal having a lower melting point than tantalum, or 2) finer tantalum valve metal.
At this time, the obtained non-porous portion 20 is impregnated with the conductive material precursor (second treatment liquid or the like) in the formation step of the conductive material (solid electrolyte layer 4) subsequent to the third step. I do not receive it. Therefore, in the configuration of the present invention, this non-porous portion 20 can be newly used as the direct anode lead portion instead of the conventional anode lead wire.
Thus, since the volume for covering the anode lead wire is unnecessary, the exterior volume in Example 1 and Example 2 is smaller than the exterior volume in Comparative Example 1 and is clear from Table 1. As can be seen, according to the present invention, a solid electrolytic capacitor having a large capacitance with respect to the exterior volume can be obtained as a result.

[Modification]
Although the present invention has been specifically described with reference to several examples, the present invention is not limited to the above-described configurations, and various modifications can be made.

For example, in each of the above examples, the solid electrolyte layer 4 is formed by polymerizing a conductive polymer, but the solid electrolyte layer 4 may be made of manganese dioxide. At this time, as shown in FIGS. 3 and 4, the solid electrolyte layer 4 impregnates the porous portion 21 of the anode body 2 excluding the non-porous portion 20 with the second treatment liquid S such as a manganese nitrate aqueous solution. Then, it can be formed by a process of thermal decomposition.
In addition, when forming the solid electrolyte layer 4, the anode lead wire 1 is not particularly required, so that the anode body 2 with the anode lead wire 1 removed is immersed to the vicinity of the non-porous portion 20 as shown in FIG. It does not matter as a process of an aspect.

The first valve metal powder or other valve metal powder is not limited to the metals described in the above examples, but may be a conventionally known one that can exhibit the same effect, for example, aluminum. Can also be used as the first valve metal or other valve metal.
Further, the first or second treatment liquid is not limited to the treatment liquids described in the above examples, and conventionally known ones that can exhibit the same effect, for example, the first treatment liquid includes adipic acid. Citric acid and boric acid can also be used, and a monomer solution containing thiophene, pyrrole or aniline or a derivative thereof can be used as the second treatment liquid.

  Thus, the present invention is not limited to the configurations described in the above examples, and various modifications can be conceived by those skilled in the art based on the basic technical idea and teachings disclosed above. Is self-explanatory.

  As described above, the present invention provides a solid electrolytic capacitor having a large capacitance with respect to the exterior volume and a method for manufacturing the same, by providing a structure having no anode lead wire protruding from the anode body, and is novel and useful. It is clear that it is.

It is a sectional side view showing one embodiment of the solid electrolytic capacitor concerning the present invention. It is a figure which shows the state which has performed the process which forms an oxide film layer with a 1st process liquid to the sintered compacting body. It is a figure which shows the state which has performed the process which forms a solid electrolyte layer further with the 2nd process liquid after the process shown in FIG. It is a figure which shows another process process which forms a solid electrolyte layer with a 2nd process liquid. It is a side view which shows the capacitor | condenser element of the solid electrolytic capacitor which concerns on a prior art example. In manufacturing the solid electrolytic capacitor which concerns on a prior art example, it is a figure which shows the state which has performed the process which forms an oxide film layer with a 1st process liquid to the sintered compacting body. It is a figure which shows the state which is performing the process which forms a solid electrolyte layer further with the 2nd process liquid after the process shown in FIG. It is a sectional side view which shows the solid electrolytic capacitor which concerns on a prior art example.

Explanation of symbols

C container F 1st process liquid S 2nd process liquid E Power supply 1 Anode lead wire 2 Anode body 2 'Formation 3 Oxide film layer 4 Solid electrolyte layer 5 Cathode extraction layer 6 Exterior resin 7 Conductive adhesive 8a Cathode lead Frame 8b Anode lead frame 10 Solid electrolytic capacitor 11 Capacitor element 12a Cathode terminal portion 12b Anode terminal portion 20 Nonporous portion 21 Porous portion 50 Solid electrolytic capacitor according to conventional example

Claims (3)

A solid electrolytic capacitor having a capacitor element in which an oxide film layer, a solid electrolyte layer, and a cathode lead layer are sequentially formed on the surface of an anode body obtained by pressure forming and sintering a valve action metal powder,
A porous anode body made of a powder of a first valve metal,
A non-porous portion provided on at least one side of the porous anode body, wherein the non-porous portion has a melting point lower than that of the first valve-acting metal, or the porous metal A non-porous portion made of a powder of the first valve metal having a finer particle diameter than that forming the anode body;
An anode terminal part formed by covering at least the surface of the non-porous part;
A solid electrolytic capacitor comprising:   2. The solid electrolytic capacitor according to claim 1, wherein the first valve metal powder is made of tantalum, and the other valve metal powder is made of niobium. 3. This is a method for producing a solid electrolytic capacitor having a capacitor element in which an oxide film layer, a solid electrolyte layer, and a cathode lead layer are sequentially formed on the surface of an anode body obtained by pressure forming and sintering a valve action metal powder. And
A step of pressure-molding a first valve metal powder to be a porous anode body;
At least one side of the porous anode body has a particle diameter larger than the powder of another valve action metal having a melting point lower than that of the first valve action metal to be a non-porous part, or the one forming the porous anode body. A second pressure forming step of pressure-forming the fine first valve metal powder together with the porous anode body,
Sintering the molded body after the second pressure molding step to obtain a non-porous part;
Coating the surface of the obtained non-porous part to form an anode terminal part;
The manufacturing method of the solid electrolytic capacitor characterized by including this.

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