JP5850658B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same.

  Conventionally, solid electrolytic capacitors using tantalum, aluminum, and the like have been widely used in electronic devices such as portable electronic terminals and personal computers because of their large capacitance and excellent frequency characteristics. In recent years, with the increase in reliability and performance of electronic devices, demands such as reduction of leakage current (LC) and low equivalent series resistance (low ESR) are increasing.

  Here, the structure of a conventional solid electrolytic capacitor will be described. FIG. 2 is a cross-sectional view of a conventional solid electrolytic capacitor. The anode body 21 is a sintered body having a large number of minute holes (porous layer) obtained by molding and sintering fine powder of valve action metal such as tantalum or aluminum. Together with the anode body 21, the anode lead 28 serving as the anode portion is made of a valve metal wire or the like, and is led out from the anode lead lead-out surface (lead-out surface) of the anode body 21. A dielectric layer 22 made of an oxide film is formed on the lead-out surface, side surface, bottom surface of the anode body 21 and the surface of the internal porous layer. Further, a solid electrolyte layer 23 is formed on the surface of the dielectric layer 22. The insulating part 30 is made of an epoxy resin and is arranged so that the solid electrolyte layer 23 does not contact the anode lead 28 and cause an electrical short circuit.

  On the surface of the solid electrolyte layer 23, a graphite layer 24 and a silver paste layer 25 are formed as a cathode portion to constitute a capacitor element. The anode part and the cathode part of the capacitor element are electrically connected to the lead frame 27 which is an external electrode terminal by a conductive adhesive 26 or welding. Thereafter, an exterior made of the exterior resin 29 is provided to complete the solid electrolytic capacitor 120.

  The solid electrolyte layer has a function of electrically connecting the dielectric layer and the cathode portion to draw out the capacitance of the dielectric layer. The solid electrolyte layer is one of the important components for obtaining the electrical characteristics of the solid electrolytic capacitor, and the structure, manufacturing method, and the like have been studied. In recent years, solid electrolytic capacitors using a conductive polymer layer made of a conductive polymer as a solid electrolyte layer have been manufactured.

  Conventionally, a conductive polymer layer is formed by immersing an anode body (anode body element) on which a dielectric layer is formed in a solution obtained by adding a monomer, a catalyst, an oxidant as a dopant to a solvent, and the like. A chemical oxidative polymerization method is used in which polymerization is performed on the surface of the layer. In general, the chemical oxidative polymerization method uses a solution that has good permeability and easily penetrates into the details of the porous layer, and has features such as good adhesion between the dielectric layer and the layer formed as the cathode part. A conductive polymer layer is obtained.

  In addition to the chemical oxidative polymerization method, a method using a conductive polymer suspension is also used. This conductive polymer suspension solution method (conductive polymer suspension solution method) is a method in which a conductive polymer suspension solution containing a conductive polymer that has been polymerized in advance and added with a dopant is added to an anode. In this method, a body element is immersed and impregnated, pulled up, and then dried by heating to form a conductive polymer layer. The conductive polymer layer obtained by this method has a higher density, better heat resistance, and faster formation of the conductive polymer layer than a conductive polymer layer obtained by a chemical oxidative polymerization method, etc. There is. A conductive polymer suspension solution (described as a conductive polymer compound suspension aqueous solution in Patent Document) and a production method used in this method are described in Claims 2 and 3, paragraphs 0014 to 0028 of Patent Document 1. ing.

  As a state of formation of the conductive polymer layer with respect to the dielectric layer by the conductive polymer suspension solution method, as shown in FIG. 2, the conductive polymer layer (in FIG. 2, solid electrolyte layer) ). An example of a solid electrolytic capacitor having such a structure is described in FIG.

  Further, as a state of formation of the conductive polymer layer different from Patent Document 2 by the conductive polymer suspension solution method, the conductive polymer layer is not formed on the lead-out surface, and the dielectric layer May be exposed. An example of a solid electrolytic capacitor having such a structure is described in FIG.

Japanese Patent Laid-Open No. 11-121281 JP 2010-3772 A JP 2005-109252 A

  In the step of forming the conductive polymer layer using the conductive polymer suspension solution method, since the anode element is immersed in the conductive polymer suspension solution, air remaining in the porous layer of the anode element and In addition, moisture or the like, which is a solvent of the conductive polymer suspension solution that has permeated into the porous layer, tends to remain inside the porous layer. When the conductive polymer layer covers the entire surface of the anode element without sufficiently releasing these residues, the above-described air, moisture and the like expand due to heating during drying. In some cases, the gas resulting from air, water vapor, or the like may cause minute separation at the interface between the conductive polymer layer and the dielectric layer. As a result, there is a problem that ESR increases and manufacturing yield decreases.

  Further, as shown in FIG. 1 of Patent Document 3, if there is a portion that is not covered with the conductive polymer layer on the lead-out surface of the anode body element, the anode body element impregnated with the conductive polymer suspension solution is heated when the anode body element is heated. Gas tends to be released to the outside of the body element, but before the exterior is provided, the gas is likely to enter from the outside, and the conductive polymer layer inside the porous layer may be oxidized. As a result, there is a problem that ESR increases and reliability decreases.

  Accordingly, an object of the present invention is to provide a solid electrolytic capacitor and a manufacturing method thereof with high reliability by suppressing the increase in ESR and improving the manufacturing yield by solving the above-mentioned problems.

A solid electrolytic capacitor according to the present invention includes a lead-out surface for leading out an anode lead, a bottom surface facing the lead-out surface, a side surface in contact with the lead-out surface and the bottom surface, and an anode made of a valve metal having a porous layer A dielectric layer formed on the surface of the anode body, a conductive polymer layer formed on the surface of the dielectric layer, a graphite layer sequentially formed on the surface of the conductive polymer layer, and A capacitor element comprising a silver paste layer, the capacitor element being a solid electrolytic capacitor electrically connected to an external connection terminal and having an exterior covering the entire surface with an insulating material, the conductive polymer layer Consists of a first conductive polymer layer and a second conductive polymer layer, the first conductive polymer layer covering at least a part of the bottom surface and the side surface, and of the lead-out surface at least Made by opening part, the second conductive polymer layer, the first conductive polymer layer and Ri formed over said outlet surface, the dielectric layer and the first conductive polymer Gas permeability, adhesion between the dielectric layer and the first conductive polymer layer, and between the layers and between at least a portion of the lead-out surface and the second conductive polymer layer; and wherein characterized Rukoto that having a third conductive polymer layer comprising a dielectric layer and the adhesion of the second conductive polymer layer.

  In the solid electrolytic capacitor of the present invention, it is preferable that the first conductive polymer layer covers at least 70% of the area of the side surface.

  The solid electrolytic capacitor of the present invention is characterized in that the first conductive polymer layer and the second conductive polymer layer have gas barrier properties.

  The solid electrolytic capacitor manufacturing method of the present invention includes a lead-out surface for leading out the anode lead, a bottom surface facing the lead-out surface, a side surface in contact with the lead-out surface and the bottom surface, and a valve metal having a porous layer A step of forming an anode body comprising: a step of forming a dielectric layer comprising an oxide film on the surface of the anode body; dipping in a conductive polymer suspension and drying; Covering at least a portion and opening at least a portion of the lead-out surface to form a first conductive polymer layer; and covering the first conductive polymer layer and the lead-out surface A step of forming a second conductive polymer layer, a step of forming a silver paste layer after forming a graphite layer on the surface of the second conductive polymer layer, and forming a cathode portion; and the anode lead And the cathode part electrically connected to the external electrode terminal , Characterized in that it comprises a step of molding an insulating material.

  In the method for producing a solid electrolytic capacitor of the present invention, between the dielectric layer and the first conductive polymer layer, and between at least a part of the lead-out surface and the second conductive polymer layer, The chemical oxidative polymerization method is used to provide gas permeability, adhesion between the dielectric layer and the first conductive polymer layer, and adhesion between the dielectric layer and the second conductive polymer layer. The method further includes a step of forming three conductive polymer layers.

  In addition, in the step of forming the first conductive polymer layer, in the case of forming by one immersion in the conductive polymer suspension, the immersion time is controlled or the anode element is used. The operation of immersing is performed in a plurality of times, and the residual gas can be sufficiently reduced by gradually increasing the ratio of the area covering the side surface of the anode element. Therefore, generation of gas that affects the increase in ESR and the like is suppressed from the anode element after the formation of the first conductive polymer layer, and even if the second conductive polymer layer is formed. Thus, the problem of peeling as in the prior art does not occur.

  The first conductive polymer layer is formed so as to cover at least a part of the bottom surface and the side surface of the anode element and to open at least a part of the lead-out surface. It facilitates the release of the gas remaining in the porous layer during the formation of the molecular layer. As a result, even when heated during drying, it is possible to suppress peeling of the dielectric layer and the first conductive polymer layer. Further, by covering the entire surface of the anode element with the second conductive polymer layer, gas is prevented from entering from a portion where the conductive polymer layer is not formed until the exterior is provided. The deterioration of the conductive polymer layer inside the porous layer due to oxidation is prevented. As a result, it is possible to provide a solid electrolytic capacitor and a method for manufacturing the same that suppress an increase in ESR, improve the manufacturing yield, and have high reliability.

The schematic sectional drawing explaining the structure of the solid electrolytic capacitor of this invention. The schematic sectional drawing explaining the structure of the conventional solid electrolytic capacitor.

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

  FIG. 1 is a schematic cross-sectional view illustrating the configuration of the solid electrolytic capacitor of the present invention. The solid electrolytic capacitor of the present invention has an anode body 1 made of a sintered body of a valve action metal having a lead-out surface for leading out the anode lead 8 and having a porous layer. Dielectric layer 2 is formed on the surface of anode body 1 having the porous layer. The insulating part 11 is formed by applying an epoxy resin or the like.

  The anode body 1 is formed of a sintered body made of metal fine particles having a valve action, a valve action metal whose surface is expanded by etching and formed into a porous layer, and the like. The valve metal is appropriately selected from tantalum, aluminum, titanium, niobium, zirconium, or alloys thereof.

  The dielectric layer 2 is a film obtained by electrolytically oxidizing the surface of the valve action metal, and is formed on the lead-out surface, the side surface, the bottom surface of the anode body 1 and the surface of the internal porous layer. The thickness of the dielectric layer 2 can be adjusted as appropriate by the voltage of electrolytic oxidation.

  Here, the difference between the present invention and the prior art will be described. The solid electrolytic capacitor of the present invention is formed by immersing and impregnating an anode body (anode body element) on which a dielectric layer is formed in a conductive polymer suspension, lifting it and drying it by heating. One conductive polymer layer 3 is formed so as to cover the bottom and side surfaces of the anode element and open the lead-out surface. Further, the second conductive polymer layer 10 is formed so as to cover the lead-out surface and the first conductive polymer layer 3. The immersion of the conductive polymer suspension when forming the second conductive polymer layer 10 is performed so as to reach the insulating portion 11 and not adhere to the anode lead 8.

  In this way, the first conductive polymer layer 3 is formed on the surface of the dielectric layer 2 so as to cover the bottom surface and the side surface of the anode element and open the lead-out surface. When the polymer layer 3 is formed, the gas remaining in the porous layer is easily released. As a result, even when heated during drying, it is possible to suppress peeling of the dielectric layer and the first conductive polymer layer. As a result, it is possible to provide a solid electrolytic capacitor in which an increase in ESR is suppressed and a manufacturing yield is improved, and a manufacturing method thereof.

  The first conductive polymer layer 3 facilitates the release of the gas remaining in the porous layer, and the influence of the solvent that enters the porous layer when forming the second conductive polymer layer 10. In order to reduce, it is preferable to cover at least 70% of the area of the side surface of the anode element.

  The first conductive polymer layer 3 does not have to be formed by opening the entire lead-out surface. If the gas can be released, the first conductive polymer layer 3 is formed by opening only a part of the lead-out surface. Also good.

  Further, by covering the entire surface of the anode element on which the first conductive polymer layer 3 is formed with the second conductive polymer layer 10, until the exterior is provided with the exterior resin 9, the first Gas is prevented from entering from a portion where the conductive polymer layer 3 is not formed. In particular, the first conductive polymer layer 3 inside the porous layer is prevented from being deteriorated by oxidation due to gas. As a result, it is possible to provide a solid electrolytic capacitor having high reliability and a method for manufacturing the same.

As the conductive polymer used in the conductive polymer suspension, it is preferable to select at least one of polyaniline, polypyrrole, polythiophene, and derivatives thereof because it exhibits high conductivity. It is preferable to select from at least one of polystyrene sulfonic acid, benzene sulfonic acid, naphthalene sulfonic acid, and derivatives thereof, which have high molecular conductivity and enhance thermal stability. The solvent may be a mixed solvent of water and an organic solvent such as alcohol or acetone, but it is easy to install exhaust equipment for solvent vapor that evaporates during the drying process of the conductive polymer suspension, has low environmental impact, and is removed. From the viewpoint of easiness, it is more preferable to use only water.

  In addition, since content of the conductive polymer in the conductive polymer suspension makes dispersibility or dissolution favorable, 0.1 part by mass or more and 20.0 parts by mass with respect to 100 parts by mass of water as a solvent. Part or less.

  In order to improve the binding property of the conductive polymer, a binder such as polyacrylonitrile, methylcellulose, polyvinyl alcohol, or the like may be used.

  The first conductive polymer layer 3 and the second conductive polymer layer 10 are not limited to the conductive polymer layer formed by the conductive polymer suspension method, and block the gas. The conductive polymer layer may be formed of a material having a function of preventing intrusion.

  Further, the solid electrolytic capacitor of the present invention has gas permeation between the dielectric layer 2 and the first conductive polymer layer 3 and between at least a part of the lead-out surface and the second conductive polymer layer 10. And further improving the adhesion between the dielectric layer and the first conductive polymer layer and the adhesion between the dielectric layer and the second conductive polymer layer. A third conductive polymer layer (not shown) formed by a legal method may be provided.

  The third conductive polymer layer is not limited to the conductive polymer layer formed by the chemical oxidative polymerization method, but is formed from a material having gas permeability and adhesion. If it is.

  Thereafter, a graphite layer 4 and a silver paste layer 5 serving as a cathode portion are formed on the surface of the second conductive polymer layer 10 to obtain a capacitor element. Finally, the capacitor element and the lead frame 7 which is an external electrode terminal are electrically connected by the conductive adhesive 6 or welding, and the exterior by the exterior resin 9 is provided to complete the solid electrolytic capacitor 100 of the present invention.

  The conductive polymer suspension can form a conductive polymer layer by drying with ultraviolet irradiation in addition to heating. The heating temperature when drying by heating is preferably 100 ° C. or higher and 250 ° C. or lower.

  The reason is that if the temperature is lower than 100 ° C., the volatilization of the solvent is not efficient, and if it exceeds 250 ° C., the conductivity of the conductive polymer may be impaired.

  Examples of the present invention are described in detail below.

Example 1
The solid electrolytic capacitor of Example 1 of the present invention has the same structure as that of the embodiment.

  Tantalum wire was used for the anode lead. In a molding die filled with fine tantalum powder, an anode lead was embedded in advance on one surface serving as a lead-out surface of the anode lead, and press molding was performed. The molded body was sintered to obtain an anode body having a porous layer from which an anode lead was derived. Thereafter, the anode body was electrolytically oxidized in a phosphoric acid aqueous solution to form a dielectric layer. The anode body has a length of 3.5 mm, a width of 1.0 mm, and a thickness of 4.5 mm. The lead-out surface is a portion having a length of 3.5 mm and a width of 1.0 mm. The insulating part was formed by applying an epoxy resin.

  Next, it is immersed in the conductive polymer suspension solution from the bottom surface to the side surface of the anode body (anode element) on which the dielectric layer is formed, and the conductive polymer suspension solution is not attached to the lead-out surface. The process of controlling and lifting was performed once. The immersion time in this step was 1 minute. Then, it dried at 125 degreeC for 1 hour, and formed the 1st conductive polymer layer. The first conductive polymer layer was formed to have an average thickness of 10 μm.

  Subsequently, in order to attach the conductive polymer suspension solution to the surface of the anode element including the lead-out surface, the conductive polymer suspension is immersed so as to reach the insulating portion, pulled up once, and then dried at 125 ° C. for 1 hour. A second conductive polymer layer was formed. The second conductive polymer layer was formed so as to have an average thickness of 10 μm.

  The formation of the first conductive polymer layer and the second conductive polymer layer is performed by using polythiophene, which is a conductive polymer, and polystyrene sulfonic acid as a dopant in an amount of 10 masses per 100 mass parts of solvent water. The conductive polymer suspension contained so as to be part was used.

  Thereafter, a cathode part composed of a graphite layer and a silver paste layer was formed on the second conductive polymer layer to obtain a capacitor element. Further, the anode lead and the cathode part are electrically connected to the anode and cathode side lead frames by using welding and a conductive adhesive, and finally molded with an exterior resin, and the solid electrolytic having a rated voltage of 20 V and a capacity of 22 μF is used. A capacitor was obtained. The production quantity was 200 pieces.

  Table 1 shows the ESR when the frequency is 100 kHz, the LC measurement result at an applied voltage of 20 V, and the product yield and reliability evaluation results for the manufactured solid electrolytic capacitor. ESR and LC were measured according to JIS C5101-1. The number of measurements is 100. In addition, the manufacturing yield was judged as acceptable based on the ESR criterion value. For the evaluation of reliability, the increase rate of ESR after standing at high temperature (105 ° C., 500 hours, in air) was evaluated. The number of measurements is 50.

(Comparative Example 1)
Next, as Comparative Example 1, the first conductive polymer layer was dipped and pulled up so that the conductive polymer suspension solution adhered to the entire surface of the anode element including the lead-out surface of the anode lead. Formed. The other points were the same as in Example 1. The production quantity was 200 pieces.

  Table 1 shows the measurement results of ESR and LC of the manufactured solid electrolytic capacitor, and the results of manufacturing yield and reliability evaluation. The measurement method and the like are the same as in Example 1.

(Example 2)
In Example 2, a third conductive polymer layer was formed on the surface of the dielectric layer by chemical oxidative polymerization so that gas permeated and adhesion was improved. In order to release gas on the surface of the third conductive polymer layer, the lead-out surface was opened to form the first conductive polymer layer.

  Further, a second conductive polymer layer was formed so as to cover the entire surface of the first conductive polymer layer and the opened lead-out surface. The components and production conditions of the conductive polymer suspension used were the same as in Example 1.

  In chemical oxidative polymerization, a conductive polymer solution in which thiophene as a monomer and aromatic sulfonic acid iron salt as an oxidant that also serves as a dopant are added to 25 parts by mass with respect to 100 parts by mass of ethanol as a solvent. Was used.

  Table 2 shows the measurement results of ESR and LC, and the results of manufacturing yield and reliability evaluation. The measurement conditions were the same as in Example 1.

(Comparative Example 2)
On the surface of the dielectric layer, a third conductive polymer layer was formed by chemical oxidative polymerization using the same liquid as in Example 2 so that the gas permeated and the adhesion was improved. Others were the same as in Comparative Example 1.

  Table 2 shows the measurement results of ESR and LC, and the results of manufacturing yield and reliability evaluation. The measurement conditions were the same as in Example 1.

  As shown in Table 1, in the solid electrolytic capacitor obtained in Example 1, an increase in ESR was suppressed as compared with the solid electrolytic capacitor obtained in Comparative Example 1. It also improves manufacturing yield and reliability test results. In addition, as shown in Table 2, the solid electrolytic capacitor obtained in Example 2 was suppressed from increasing in ESR than the solid electrolytic capacitor obtained in Comparative Example 2. It also improves manufacturing yield and reliability test results. From these, the effect of this invention has been confirmed.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to these embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

1, 21 Anode body 2, 22 Dielectric layer 3 First conductive polymer layer 4, 24 Graphite layer 5, 25 Silver paste layer 6, 26 Conductive adhesive 7, 27 External electrode terminal 8, 28 Anode lead 9, 29 Exterior resin 10 Second conductive polymer layer 11, 30 Insulating part 23 Solid electrolyte layer 100, 120 Solid electrolytic capacitor

Claims (5)

  An anode body comprising a lead-out surface for leading out the anode lead, a bottom surface facing the lead-out surface, a side surface in contact with the lead-out surface and the bottom surface, and made of a valve metal having a porous layer, and a surface of the anode body A dielectric layer formed on the surface of the dielectric layer, a conductive polymer layer formed on the surface of the dielectric layer, and a graphite layer and a silver paste layer sequentially formed on the surface of the conductive polymer layer. A solid electrolytic capacitor having an element, wherein the capacitor element is electrically connected to an external connection terminal and has an exterior covering the entire surface with an insulating material, wherein the conductive polymer layer is a first conductive polymer A first conductive polymer layer covering at least a part of the bottom surface and the side surface and opening at least a part of the lead-out surface. The second guide The conductive polymer layer covers the first conductive polymer layer and the lead-out surface, and is between the dielectric layer and the first conductive polymer layer and at least a part of the lead-out surface. Between the second conductive polymer layer, gas permeability, adhesion between the dielectric layer and the first conductive polymer layer, and the dielectric layer and the second conductive polymer A solid electrolytic capacitor comprising a third conductive polymer layer having layer adhesion.   The solid electrolytic capacitor according to claim 1, wherein the first conductive polymer layer covers at least 70% or more of the area of the side surface.   The solid electrolytic capacitor according to claim 1, wherein the first conductive polymer layer and the second conductive polymer layer have gas barrier properties.   A step of forming an anode body made of a valve metal having a porous layer having a lead-out surface for leading out the anode lead, a bottom surface facing the lead-out surface, and a side surface in contact with the lead-out surface and the bottom surface; Forming a dielectric layer made of an oxide film on the surface of the anode body, dipping in a conductive polymer suspension and drying, covering at least a part of the bottom surface and the side surface, and the lead-out surface Forming a first conductive polymer layer by opening at least a part of the first conductive polymer layer, and forming a second conductive polymer layer so as to cover the first conductive polymer layer and the lead-out surface Forming a graphite layer on the surface of the second conductive polymer layer and then forming a silver paste layer to form a cathode portion; electrically connecting the anode lead and the cathode portion to an external electrode terminal; Connecting to and molding with insulating material Method for producing a solid electrolytic capacitor according to claim. Gas permeability between the dielectric layer and the first conductive polymer layer and between at least a part of the lead-out surface and the second conductive polymer layer by chemical oxidative polymerization, Forming a third conductive polymer layer having adhesion between the dielectric layer and the first conductive polymer layer, and adhesion between the dielectric layer and the second conductive polymer layer; The method for producing a solid electrolytic capacitor according to claim 4 , further comprising:

Images