JP2009231646A - Solid-state electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state electrolytic capacitor that maintains electrical current shutoff function when an excessive short-circuit current flows through a capacitor element, and is miniaturized. <P>SOLUTION: The solid-state electrolytic capacitor includes a capacitor element 10 having a positive electrode object 1 from which a positive electrode lead wire 1a is drawn out, a dielectric layer 2 formed on the surface of this positive electrode object 1, an electrolyte layer 3 formed on the dielectric layer 2, and a cathode layer 5 formed on this electrolyte layer 3. Here, the electrolyte layer 3 is composed of a primary electrolyte layer 3a formed on the dielectric layer 2 and a secondary electrolyte layer 3b formed on this primary electrolyte layer 3a. In the secondary electrolyte layer 3b, thermally expandable graphite 4 is included on the inside throughout its layer that expands through thermal loading. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor with a built-in fuse.

  Solid electrolytic capacitors are used in CPU power supply circuits and peripheral circuits in various portable information terminals such as personal computers and mobile phones, various video information devices such as digital cameras, and other electronic devices. The advantage is that the failure rate is small.

  In recent years, as such a solid electrolytic capacitor, a so-called built-in type solid electrolytic capacitor in which a fuse is connected between a capacitor element and a terminal and the fuse is enclosed in an exterior resin has been proposed (see, for example, Patent Document 1). ).

In the solid-state charge capacitor with a built-in fuse described in Patent Document 1, an excessive short-circuit current is caused by installing a fuse (wire-shaped sintered fuse that melts at about 300 ° C.) between the capacitor element and the terminal. When the current flows, the electric circuit is opened to cut off the current.
JP 2001-176374 A

  However, the solid electrolytic capacitor with a built-in fuse disclosed in Patent Document 1 has a problem in that the structure is complicated and the volume efficiency of the internal element is reduced by the space for housing the fuse. There was a certain limit to the increase in capacity.

  The present invention has been made in view of these problems, and the object thereof is a solid electrolytic capacitor that can be reduced in size while maintaining a current blocking function when an excessive short-circuit current flows through the capacitor element. Is to provide.

  In order to achieve the above object, a solid electrolytic capacitor according to the present invention is a solid electrolytic capacitor in which a dielectric layer, an electrolyte layer, and a cathode layer are sequentially formed on the surface of an anode body. A first electrolyte layer formed on the body layer, and a second electrolyte layer formed on the first electrolyte layer, wherein the second electrolyte layer contains thermally expandable graphite. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, when an excessive short circuit current flows into a capacitor | condenser element, the solid electrolytic capacitor which can be reduced in size is maintained, maintaining the interruption | blocking function of an electric current.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. In addition, this invention is not limited by this embodiment.

  FIG. 1 is a schematic cross-sectional view showing the configuration of the solid electrolytic capacitor according to the present embodiment. 1A is a schematic cross-sectional view of the entire solid electrolytic capacitor, and FIG. 1B is a partially enlarged view of the vicinity of the electrolyte layer of the solid electrolytic capacitor. FIG. 2 is a schematic diagram showing the state before and after the expansion of the thermally expandable graphite due to a thermal load.

  As shown in FIG. 1A, the solid electrolytic capacitor of this embodiment includes an anode body 1 from which an anode lead wire 1a is derived, a dielectric layer 2 formed on the surface of the anode body 1, and a dielectric body. A capacitor element 10 having an electrolyte layer 3 formed on the layer 2 and a cathode layer 5 formed on the electrolyte layer 3 is provided. Here, as shown in FIG. 1B, the electrolyte layer 3 includes a first electrolyte layer 3a formed on the dielectric layer 2 and a first electrolyte layer 3a formed on the first electrolyte layer 3a. 2 electrolyte layers 3b. The second electrolyte layer 3b contains thermal expandable graphite 4 that expands due to a heat load in the entire inside thereof. Then, as shown in FIG. 1A, a flat cathode terminal 7 is bonded onto the cathode layer 5 of the capacitor element 10 via a conductive adhesive (not shown), and a flat plate is attached to the anode lead wire 1a. The anode terminal 6 is joined. And the mold exterior body 8 which consists of an epoxy resin etc. is shape | molded in the form with which the anode terminal 6 and a part of cathode terminal 7 were pulled out outside like FIG. 1 (A).

  The specific configuration of the solid electrolytic capacitor is as follows.

  The anode body 1 is composed of a porous sintered body of metal particles made of a valve action metal, and the anode lead wire 1a is made of a rod-like lead wire made of the same valve action metal. A part of the anode lead wire 1 a protrudes from the anode body 1 and is embedded in the anode body 1. Here, the valve metal constituting the anode lead wire 1a and the anode body 1 is a metal material capable of forming an insulating oxide film, such as tantalum (Ta), niobium (Nb), aluminum (Al), A simple metal such as titanium (Ti) is employed. Moreover, you may employ | adopt the alloy of the above-mentioned valve action metals.

  The dielectric layer 2 is made of a dielectric made of an oxide of a valve action metal, and is provided on the surface of the anode body 1 with a predetermined thickness. For example, when the valve metal is made of tantalum metal, the dielectric layer 2 is tantalum oxide.

  The electrolyte layer 3 includes a first electrolyte layer 3a formed on the dielectric layer 2 and a second electrolyte layer 3b formed on the first electrolyte layer 3a. The first electrolyte layer 3a and the second electrolyte layer 3b are not particularly limited as long as they are conductive materials, but polymer materials such as polypyrrole, polythiophene, polyaniline, and derivatives thereof having excellent conductivity are used. Adopted. And in the 2nd electrolyte layer 3b which comprises the electrolyte layer 3, the thermally expansible graphite 4 contains in the inside of the layer inside. As shown in FIG. 2, the thermally expandable graphite 4 is mainly composed of a layered graphite crystal 4a and an interlayer 4b. The interlayer 4b is decomposed by a thermal load (high temperature heating), and the graphite pressure is generated by the gas pressure. 4a has the characteristic of expanding in the direction of the arrow. Since the graphite crystal 4a expanded in this way forms a structure having voids (spaces) between the crystals, the second electrolyte layer 3b of the present embodiment has a structure in which the thermally expandable graphite 4 is formed inside due to a heat load. The resulting electrical gap is formed.

  In addition to the conductive polymer material described above, a conductive inorganic material such as manganese dioxide may be employed for the first electrolyte layer 3a and the second electrolyte layer 3b that constitute the electrolyte layer 3.

The thermally expandable graphite 4 has an expansion degree (volume per gram when the graphite is heated at 1000 ° C. for 10 seconds: cm ³ / g), expansion start temperature (when expanded to 1.1 times or more of the original volume) Of the second electrolyte layer 3b containing the thermally expandable graphite 4 by adjusting the content (weight of the thermally expandable graphite with respect to the total weight of the second electrolyte layer: wt%) and the like. It is possible to control the ability to form an electrical gap.

  The cathode layer 5 is composed of a laminated film of a conductive carbon layer 5 a made of a layer containing carbon particles and a silver paste layer 5 b made of a layer containing silver particles, and the second electrolyte layer 3 b constituting the electrolyte layer 3. It is provided on the top.

  The capacitor element 10 includes an anode body 1 from which the above-described anode lead wire 1a is derived, a dielectric layer 2, an electrolyte layer 3 (first electrolyte layer 3a, second electrolyte layer 3b), and a cathode layer 5. The

  The anode terminal 6 and the cathode terminal 7 are made of flat terminals made of a conductive material such as copper (Cu) or nickel (Ni), and function as external lead terminals of the solid electrolytic capacitor. The anode terminal 6 is joined to the anode lead wire 1a by spot welding, and the cathode terminal 7 is joined to the cathode layer 5 via a conductive adhesive (not shown).

  And the mold exterior body 8 which consists of an epoxy resin etc. is shape | molded in the form with which the anode terminal 6 and a part of cathode terminal 7 were pulled out outside in the opposite direction. Further, the end portions of the anode terminal 6 and the cathode terminal 7 exposed from the mold exterior body 8 are bent along the side surface and the lower surface of the mold exterior body 8, and the solid electrolytic capacitor is mounted (soldered) on the mounting substrate. Function as a terminal.

  The anode body 1 is the “anode body” of the present invention, the dielectric layer 2 is the “dielectric layer” of the present invention, the electrolyte layer 3 is the “electrolyte layer” of the present invention, and the first electrolyte layer 3 a is the present invention. The “first electrolyte layer”, the second electrolyte layer 3b are “second electrolyte layer” of the present invention, the thermally expandable graphite 4 is “thermally expandable graphite” of the present invention, and the cathode layer 5 is of the present invention. It is an example of a “cathode layer”.

(Production method)
Next, a method for manufacturing the solid electrolytic capacitor of this embodiment shown in FIG. 1 will be described.

  Step 1: A porous sintered body is obtained by sintering a molded body made of metal particles having a valve action formed so as to embed a part of the anode lead wire 1a around the anode lead wire 1a in a vacuum. An anode body 1 is formed. At this time, the metal particles are welded.

  Step 2: Anodization is performed on the anode body 1 in an electrolytic solution to form a dielectric layer 2 made of an oxide of a valve action metal with a predetermined thickness so as to cover the periphery of the anode body 1.

  Step 3: A first electrolyte layer 3a and a second electrolyte layer 3b are successively formed on the surface of the dielectric layer 2 by using a chemical polymerization method. Specifically, the first electrolyte layer 3a made of a conductive polymer is formed by oxidatively polymerizing the monomer with the oxidant using the first chemical polymerization solution in which the monomer and the oxidant are dissolved. Subsequently, the second electrolyte layer 3b made of a conductive polymer is obtained by oxidatively polymerizing the monomer with an oxidant using the second chemical polymerization liquid in which the thermally expandable graphite 4 is mixed in addition to the monomer and the oxidant. Form. In the present embodiment, the thermal expansion graphite 4 is contained in the second electrolyte layer 3b at a predetermined content by performing oxidative polymerization in a state where the thermal expansion graphite 4 is mixed with the second chemical polymerization liquid. I am letting. At this time, the thermally expandable graphite 4 is added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

  The heat-expandable graphite 4 includes, for example, a method of mixing a solid neutralizer with acid-treated graphite obtained by introducing graphite into a mixture of sulfuric acid and an oxidizing agent and reacting the graphite. A material prepared by a method of mixing a solid neutralizer with an aqueous alkali solution or water washed after treatment in a mixture of agents is employed. In addition, the expansion performance (expansion degree, expansion start temperature, etc.) of the thermally expandable graphite 4 can be easily controlled by adjusting the intercalation compound (interlayer material 4b) introduced into the graphite (graphite crystal 4a) in the above-described treatment. can do.

  As described above, the electrolyte layer 3 composed of the first electrolyte layer 3 a and the second electrolyte layer 3 b containing the thermally expandable graphite 4 is formed on the surface of the dielectric layer 2.

The first electrolyte layer 3a (or / and the second electrolyte layer 3b) is replaced with a layer made of a conductive polymer as described above, and a manganese dioxide layer formed by thermal decomposition of manganese nitrate ( Or / and a manganese dioxide layer containing thermally expandable graphite) may be employed.

  Step 4: A conductive carbon layer 5a is formed by applying and drying a conductive carbon paste containing carbon particles on the electrolyte layer 3 (second electrolyte layer 3b). Furthermore, a silver paste layer 5b is formed by applying and drying a silver paste on the conductive carbon layer 5a. Thereby, the cathode layer 5 made of a laminated film of the conductive carbon layer 5a and the silver paste layer 5b is formed on the electrolyte layer 3.

  The capacitor element 10 is manufactured through the steps 1 to 4 described above.

  Step 5: After applying a conductive adhesive (not shown) on the flat cathode terminal 7, the cathode layer 5 and the cathode terminal 7 are brought into contact with each other through the conductive adhesive (not shown). By drying in a state, the cathode layer 5 and the cathode terminal 7 are joined. Further, a flat anode terminal 6 is joined to the anode lead wire 1a by spot welding.

  Step 6: Molding is performed by a transfer method, and a mold outer package 8 is formed around the capacitor element 10. At this time, the anode lead wire 1a, the anode body 1, the dielectric layer 2, the electrolyte layer 3 (first electrolyte layer 3a, second electrolyte layer 3b), and the cathode layer 5 are housed inside, and the anode terminal 6 And the end of the cathode terminal 7 is shaped so as to be pulled out to the outside (opposite directions). In addition, as resin which shape | molds the mold exterior body 8, in order to suppress a moisture entering / exiting as a mold exterior body, and in order to prevent the crack at the time of solder reflow (at the time of heat processing) and peeling, it has a small water absorption rate. Resin (for example, epoxy resin) is preferably employed.

  Step 7: The anode terminal 6 and the tip of the cathode terminal 7 exposed from the mold exterior body 8 are bent downward and arranged along the side surface and the lower surface of the mold exterior body 8. The tips of both terminals function as terminals of the solid electrolytic capacitor, and are used to electrically connect the solid electrolytic capacitor to the mounting substrate via a solder member.

  Step 8: Finally, an aging process is performed in which a predetermined voltage is applied via both terminals of the solid electrolytic capacitor. This stabilizes the characteristics of the solid electrolytic capacitor.

  The solid electrolytic capacitor of this embodiment is manufactured through the above steps.

  First, as a preliminary experiment, the content of thermally expandable graphite contained in an electrolyte layer formed using a chemical polymerization method was evaluated.

<Preliminary experiment>
A chemical polymerization solution in which 10% by weight of pyrrole as a polymerizable monomer and 16% by weight of iron (III) p-toluenesulfonate as a dopant-imparting agent and oxidizing agent are dissolved in a 5: 1 mixed solvent of ethanol and water. And 25% by weight of a particulate thermally expandable graphite (expansion start temperature: 300 ° C., expansion rate: 10 cm ³ / g) powder is uniformly mixed with the chemical polymerization solution. Thereafter, a certain amount (0.1 g) of this mixed solution is applied to a glass substrate and allowed to stand in the atmosphere for 2 hours to advance the polymerization reaction. A conductive polymer film (thickness: about 100 μm) is formed on the glass substrate. ). When the weight of the glass substrate before and after film formation was accurately weighed, the weight of the formed conductive polymer film was 0.05 g. Since the mixed thermally expandable graphite does not contribute to the polymerization reaction, the weight of the thermally expandable graphite does not change before and after the formation of the conductive polymer film. Thereby, the content of thermally expandable graphite contained in the formed conductive polymer film was calculated to be 50 wt% (= 0.1 g × 25 wt% / 0.05 g). As the above-mentioned thermally expandable graphite, commercially available thermally expandable graphite (TEG) manufactured by Air Water was used.

In the following examples and comparative examples, solid electrolytic capacitors were produced based on the above-described steps, and their characteristics were evaluated. In each example, the content of the thermally expandable graphite is evaluated in the same procedure as the preliminary experiment, and the content of the thermally expandable graphite contained in the electrolyte layer is controlled based on the results.

<Experiment 1>
In the electrolyte layer 3 constituted by the first electrolyte layer 3 a made of a conductive polymer layer and the second electrolyte layer 3 b made of a conductive polymer layer containing the thermally expandable graphite 4, the second electrolyte Evaluation regarding the effect of the heat-expandable graphite 4 contained in the layer 3b was performed.

Example 1
In Example 1, the solid electrolytic capacitor A1 was manufactured through steps corresponding to the respective steps (steps 1 to 8) in the manufacturing method of the above-described embodiment.

  Step 1A: Using a tantalum metal powder having an average particle diameter of about 2 μm, the anode lead wire 1a is partially embedded so as to be formed into a substantially plate shape and sintered in a vacuum. Thereby, the anode body 1 made of a tantalum porous sintered body is formed. At this time, the tantalum metal particles are welded.

  Step 2A: Anodization is performed on the sintered anode body 1 at a constant voltage of about 8 V for about 10 hours in an about 0.1 wt% phosphoric acid aqueous solution maintained at about 60 ° C. Thereby, the dielectric layer 2 made of tantalum oxide is formed so as to cover the periphery of the anode body 1.

  Step 3A: Dissolve 0.5% by weight of pyrrole as a polymerizable monomer and 1% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent in a 5: 1 mixed solvent of ethanol and water. A first chemical polymerization solution is prepared. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in the first chemical polymerization solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the first electrolyte layer 3a (thickness t1: 5 μm) made of polypyrrole is formed on the dielectric layer 2.

Next, 10% by weight of pyrrole as a polymerizable monomer and 16% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A second chemical polymerization liquid is prepared, and thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion degree: 10 cm ³ / g) with respect to the second chemical polymerization liquid. A mixed liquid in which 25% by weight is uniformly mixed is prepared. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 95 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

  As described above, on the surface of the dielectric layer 2, the first electrolyte layer 3 a made of polypyrrole (thickness t1: 5 μm) and the second electrolyte layer 3 b made of polypyrrole containing the thermally expandable graphite 4 ( An electrolyte layer 3 (thickness: 100 μm) composed of a thickness t2: 95 μm) is formed.

  Step 4A: A conductive carbon paste is applied on the conductive polymer layer 3 and dried at 150 ° C. for 30 minutes to form a conductive carbon layer 5a made of a layer containing carbon particles. Further, a silver paste is applied on the conductive carbon layer 5a and dried at 170 ° C. for 30 minutes to form a silver paste layer 5b composed of a layer containing silver particles. Thus, the cathode layer 5 made of a laminated film of the conductive carbon layer 5a and the silver paste layer 5b is formed on the conductive polymer layer 3.

  Thereafter, the solid electrolytic capacitor A1 in Example 1 is manufactured through the above-described Steps 5 to 8.

(Example 2)
In Example 2, Example 3 except that Step 3A of Example 1 is changed to Step 3B below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). In the same manner, a solid electrolytic capacitor A2 was produced. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 10 μm) made of polypyrrole and the second electrolyte layer 3b (thickness) made of polypyrrole containing the thermally expandable graphite 4 are formed. The electrolyte layer 3 (total thickness: 100 μm) is formed.

  Step 3B: 1% by weight of pyrrole as a polymerizable monomer and 2% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A first chemical polymerization solution is prepared. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in the first chemical polymerization solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this manner, the first electrolyte layer 3a (thickness t1: 10 μm) made of polypyrrole is formed on the dielectric layer 2.

Next, 9.4% by weight of pyrrole as a polymerizable monomer and 14% by weight of iron (III) p-toluenesulfonate as an oxidant / doping agent are dissolved in a 5: 1 mixed solvent of ethanol and water. The second chemical polymerization liquid was prepared, and a thermally expandable graphite powder (particulate form) having a predetermined expansion performance (expansion start temperature 300 ° C., expansion degree 10 cm ³ / g) with respect to the second chemical polymerization liquid. Powder) A mixed liquid in which 23% by weight is uniformly mixed is prepared. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 90 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Example 3)
In Example 3, Example 1 except that Step 3A of Example 1 is changed to Step 3C below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). In the same manner, a solid electrolytic capacitor A3 was produced. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 20 μm) made of polypyrrole and the second electrolyte layer 3b (thickness) made of polypyrrole containing the thermally expandable graphite 4 are formed. The electrolyte layer 3 (total thickness: 100 μm) is formed.

  Step 3C: Dissolve 2% by weight of pyrrole as a polymerizable monomer and 3.2% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent in a 5: 1 mixed solvent of ethanol and water. A first chemical polymerization solution is prepared. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in the first chemical polymerization solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the first electrolyte layer 3a (thickness t1: 20 μm) made of polypyrrole is formed on the dielectric layer 2.

Next, 8.5% by weight of pyrrole as a polymerizable monomer and 13% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent are dissolved in a 5: 1 mixed solvent of ethanol and water. The second chemical polymerization liquid was prepared, and a thermally expandable graphite powder (particulate form) having a predetermined expansion performance (expansion start temperature 300 ° C., expansion degree 10 cm ³ / g) with respect to the second chemical polymerization liquid. (Powder) A mixed liquid in which 22% by weight is uniformly mixed is prepared. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 80 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

Example 4
In Example 4, Example 1 except that Step 3A of Example 1 is changed to Step 3D below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). In the same manner, a solid electrolytic capacitor A4 was produced. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 50 μm) made of polypyrrole and the second electrolyte layer 3b (thickness) made of polypyrrole containing the thermally expandable graphite 4 are formed. The electrolyte layer 3 (total thickness: 100 μm) is formed.

  Step 3D: 5% by weight of pyrrole as a polymerizable monomer and 8% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A first chemical polymerization solution is prepared. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in the first chemical polymerization solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this manner, the first electrolyte layer 3a (thickness t1: 50 μm) made of polypyrrole is formed on the dielectric layer 2.

Next, 5% by weight of pyrrole as a polymerizable monomer and 8% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A second chemical polymerization liquid is prepared, and thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion degree: 10 cm ³ / g) with respect to the second chemical polymerization liquid. A mixed liquid in which 13% by weight is uniformly mixed is prepared. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 50 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Example 5)
In Example 5, Example 1 except that Step 3A of Example 1 is changed to Step 3E below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). In the same manner, a solid electrolytic capacitor A5 was produced. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 90 μm) made of polypyrrole and the second electrolyte layer 3b (thickness) made of polypyrrole containing the thermally expandable graphite 4 are formed. The electrolyte layer 3 (total thickness: 100 μm) is formed.

  Step 3E: 9.4% by weight of pyrrole as a polymerizable monomer and 14% by weight of iron (III) p-toluenesulfonate as a dopant-imparting agent and oxidizing agent are dissolved in a 5: 1 mixed solvent of ethanol and water. A first chemical polymerization solution is prepared. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in the first chemical polymerization solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the first electrolyte layer 3a (thickness t1: 90 μm) made of polypyrrole is formed on the dielectric layer 2.

Next, 1% by weight of pyrrole as a polymerizable monomer and 2% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A second chemical polymerization liquid is prepared, and thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion degree: 10 cm ³ / g) with respect to the second chemical polymerization liquid. Prepare a mixed solution in which 3% by weight is uniformly mixed. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 10 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Example 6)
In Example 6, Example 3 is the same as Example 1 except that Step 3A of Example 1 is changed to Step 3F below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). In the same manner, a solid electrolytic capacitor A6 was produced. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 93 μm) made of polypyrrole and the second electrolyte layer 3b (thickness) made of polypyrrole containing the thermally expandable graphite 4 are formed. The electrolyte layer 3 (total thickness: 100 μm) is formed.

  Step 3F: 9.7% by weight of pyrrole as a polymerizable monomer and 15.5% by weight of iron (III) p-toluenesulfonate as a dopant-imparting agent and oxidizing agent, a 5: 1 mixed solvent of ethanol and water A first chemical polymerization solution dissolved in is prepared. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in the first chemical polymerization solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the first electrolyte layer 3a (thickness t1: 93 μm) made of polypyrrole is formed on the dielectric layer 2.

Next, 0.7% by weight of pyrrole as a polymerizable monomer and 1.4% by weight of iron (III) p-toluenesulfonate as a dopant-imparting agent and oxidizing agent are mixed in a 5: 1 mixed solvent of ethanol and water. A second chemical polymerization liquid dissolved in the first chemical polymerization liquid is prepared, and a thermally expandable graphite powder having a predetermined expansion performance (expansion start temperature 300 ° C., expansion degree 10 cm ³ / g) with respect to the second chemical polymerization liquid ( A mixed liquid in which 2% by weight of particulate powder) is uniformly mixed is prepared. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 7 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Comparative Example 1)
FIG. 3 is a schematic cross-sectional view showing a partially enlarged view of the vicinity of the electrolyte layer of the solid electrolytic capacitor in Comparative Example 1. In Comparative Example 1, as shown in FIG. 3, as the electrolyte layer 3, the second electrolyte layer 3b containing the thermally expandable graphite 4 was not formed on the first electrolyte layer 3a. A solid electrolytic capacitor X was produced in the same manner as in Example 1. Specifically, in Comparative Example 1, the electrolyte layer 3 (first electrolyte layer 3a) is formed by changing the process 3A of Example 1 to the following process 3G. As a result, only the first electrolyte layer 3 a (thickness t1: 100 μm) made of polypyrrole is formed as the electrolyte layer 3 on the surface of the dielectric layer 2. The comparative example 1 (solid electrolytic capacitor Y) is an example of a general solid electrolytic capacitor (solid electrolytic capacitor having no fuse function).

Step 3G: Dissolve 10.5% by weight of pyrrole as a polymerizable monomer and 17% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent in a 5: 1 mixed solvent of ethanol and water. A first chemical polymerization solution is prepared. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in the first chemical polymerization solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, only the first electrolyte layer 3 a (thickness t1: 100 μm) made of polypyrrole is formed on the dielectric layer 2 as the electrolyte layer 3.

(Comparative Example 2)
FIG. 4 is a schematic cross-sectional view showing a partially enlarged view of the vicinity of the electrolyte layer of the solid electrolytic capacitor in Comparative Example 2. In Comparative Example 2, as shown in FIG. 4, the solid electrolytic capacitor Y is the same as in Example 1 except that the first electrolyte layer 3 a is not formed on the dielectric layer 2 as the electrolyte layer 3. Was made. Specifically, in Comparative Example 2, the electrolyte layer 3 (second electrolyte layer 3b) is formed by changing the process 3A of Example 1 to the following process 3H. As a result, only the second electrolyte layer 3b (thickness t2: 100 μm) made of polypyrrole containing the thermally expandable graphite 4 is formed as the electrolyte layer 3 on the surface of the dielectric layer 2.

Step 3H: Dissolve 10.5% by weight of pyrrole as a polymerizable monomer and 17% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent in a 5: 1 mixed solvent of ethanol and water. The second chemical polymerization liquid was prepared, and a thermally expandable graphite powder (particulate form) having a predetermined expansion performance (expansion start temperature 300 ° C., expansion degree 10 cm ³ / g) with respect to the second chemical polymerization liquid. (Powder) Prepare a mixed solution in which 27.5% by weight is uniformly mixed. Then, the anode body 1 on which the dielectric layer 2 is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, only the second electrolyte layer 3b (thickness t2: 100 μm) made of polypyrrole containing the thermally expandable graphite 4 is formed on the dielectric layer 2 as the electrolyte layer 3. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the dielectric layer 2.

(Evaluation)
First, each solid electrolytic capacitor was evaluated for capacitance and equivalent series resistance (ESR). The capacitance was measured at a frequency of 120 Hz using an LCR meter for each solid electrolytic capacitor. ESR was measured at a frequency of 100 kHz using an LCR meter for each solid electrolytic capacitor. Table 1 summarizes the evaluation results of capacitance and ESR in each solid electrolytic capacitor. In addition, each measured value of capacitance and ESR in Table 1 uses an average value of 100 solid electrolytic capacitor samples, and each value of specific capacitance and specific ESR is Comparative Example 1 (solid electrolytic capacitor X). The measurement result in is normalized as 100.

  Next, a fuse function confirmation test and a combustion confirmation test were performed for each solid electrolytic capacitor. In the fuse function confirmation test, after mounting each solid electrolytic capacitor on a printed circuit board, an overvoltage of 16 V, which is twice the anodizing voltage in step 2A, is applied to short-circuit the capacitor element and an overcurrent of 5 A is applied. Then, it was observed whether or not the electric circuit was opened. In the combustion confirmation test, it was confirmed whether the capacitor element smoked or ignited under the same conditions. Table 1 summarizes the evaluation results of the fuse function confirmation test and the combustion confirmation test for each solid electrolytic capacitor. In the fuse function confirmation test, 100 solid electrolytic capacitor samples were used, of which the number of open electrical circuits (the number of open circuits) was counted, and in the combustion confirmation test, the same 100 pieces were used as capacitor elements. The number of smoked smoke (number of smoked) and the number of capacitor elements fired (number of fired) were counted.

In the above-described evaluation of capacitance and ESR and each test (fuse function confirmation test, combustion confirmation test), a general Pb-free solder material is adopted as the solder member, and the solid electrolytic capacitor is mounted on the printed board. In mounting, the solder member was formed using a soldering iron so as not to overheat the capacitor element (specifically, heated to 250 ° C. or higher).

As shown in Table 1, in Comparative Example 1 (solid electrolytic capacitor X) in which a conventional fuse is not provided, the electric circuit is not opened even when an overcurrent is passed, and smoke is emitted from all 100 evaluation samples. It was confirmed that it would ignite. On the other hand, in Examples 1 to 6 (solid electrolytic capacitors A1 to A6) in which the second electrolyte layer 3b containing the heat-expandable graphite 4 on the first electrolyte layer 3a is used as the electrolyte layer 3, In either case, the number of open circuits is 100, and it can be seen that the fuse function is working to cut off the current when overcurrent flows. This is because the thermal expansion graphite 4 is contained in the second electrolyte layer 3b, so that when the overcurrent flows, the thermal expansion graphite 4 expands due to the heat generation of the capacitor element 10, and the second electrolyte This is presumably because the current flowing through the solid electrolytic capacitor (capacitor element 10) could be cut off as a result of the occurrence of an electrical gap inside the layer 3b.

  Further, in Comparative Example 2 (solid electrolytic capacitor Y) containing thermally expandable graphite in the entire electrolyte layer, the number of open circuits (fuse function confirmation test) was 100, indicating a good result, but compared with Comparative Example 1. Thus, a decrease in capacitance and an increase in ESR were confirmed. In Comparative Example 2, since the electrolyte layer 3 (second electrolyte layer 3b) containing the thermally expandable graphite 4 is provided in direct contact with the dielectric layer 2, the thermally expandable graphite 4 is a dielectric. There is a portion in contact with the layer 2, and the effective contact area between the electrolyte layer 3 and the dielectric layer 2 (the contact area between the polypyrrole and the dielectric layer 2 that contributes to the increase or decrease in capacitance or ESR) is reduced. It is presumed that On the other hand, in Examples 1-6 (solid electrolytic capacitors A1-A6), it turns out that both the fall of such an electrostatic capacitance and the increase in ESR are reduced. This is because, in Examples 1 to 6, the first electrolyte layer 3a exists between the second electrolyte layer 3b and the dielectric layer 2, and effective contact between the electrolyte layer 3 and the dielectric layer 2 occurs. This is probably because the area is prevented from decreasing.

  On the other hand, in Example 1 (solid electrolytic capacitor A1), although the number of open circuits (fuse function confirmation test) was as good as 100, an increase in ESR was confirmed compared to Examples 2-6. . This is because, in Example 1, the ratio of the second electrolyte layer 3b containing the non-conductive thermally expandable graphite 4 in the electrolyte layer 3 composed of the first electrolyte layer 3a and the second electrolyte layer 3b. This is probably because the resistance of the electrolyte layer 3 itself is increased.

  Further, in Example 6 (solid electrolytic capacitor A6), although the number of open circuits (fuse function confirmation test) showed a good result of 100, smoke generation was confirmed in a part (10) of the evaluation samples. This is because the thickness t2 of the second electrolyte layer 3b constituting the electrolyte layer 3 in Example 6 is as thin as 7 μm, so that the heat-expandable graphite 4 starts to expand before the current is cut off. It is inferred that the smoke generation.

  From the above, in order to impart a fuse function to a solid electrolytic capacitor while maintaining the configuration of a solid electrolytic capacitor without a conventional fuse, the first electrolyte layer 3a and the first electrolyte layer 3 are used as the electrolyte layer 3 as in the present invention. It can be seen that it is effective to form a laminated film with the second electrolyte layer 3b and to contain the thermally expandable graphite 4 in the upper second electrolyte layer 3b. In particular, in order to give a solid electrolytic capacitor a fuse function without causing an increase in ESR, a decrease in capacitance, and smoke generation of the capacitor element, the thickness t2 of the second electrolyte layer 3b constituting the electrolyte layer 3 can be increased. The ratio (t1 / t2) of the thickness t1 of the first electrolyte layer 3a is preferably in the range of 0.1 to 9.0.

<Experiment 2>
Next, in the electrolyte layer 3 constituted by the first electrolyte layer 3 a made of a conductive polymer layer and the second electrolyte layer 3 b made of a conductive polymer layer containing the thermally expandable graphite 4, Evaluation on the influence of the content of the heat-expandable graphite 4 contained in the second electrolyte layer 3b was performed.

(Examples 7 to 10)
In Examples 7 to 10, the second electrolyte layer 3b in which the content of the thermally expandable graphite 4 is 5% by weight, 10% by weight, 30% by weight, and 65% by weight is formed in Step 3D of Example 4, respectively. Solid electrolytic capacitors B1 to B4 were produced in the same manner as in Example 4 except that.

  Specifically, in Step 3D of Example 4, the content of the heat-expandable graphite powder mixed in the second chemical polymerization solution is changed to 1.3% by weight (implementation) instead of 13% by weight of Example 4. Example 7) A corresponding solid electrolytic capacitor was produced by changing to 2.6% by weight (Example 8), 8.0% by weight (Example 9), and 16.5% by weight (Example 10). is doing.

(Evaluation)
About each solid electrolytic capacitor, it carried out similarly to Experiment 1, and evaluated the electrostatic capacitance and ESR, the fuse function confirmation test, and the combustion confirmation test. Table 2 shows the evaluation results of each solid electrolytic capacitor. In addition, each measured value of capacitance and ESR in Table 2 uses an average value of 100 solid electrolytic capacitor samples, and each value of specific capacitance and specific ESR is Comparative Example 1 (solid electrolytic capacitor X). The measurement result in is normalized as 100.

As shown in Table 2, in Examples 4 and 7 to 10 (solid electrolytic capacitors A4 and B1 to B4) containing the thermally expandable graphite 4 with a predetermined content (5 wt% to 65 wt%), In addition, the number of open circuits is 100, and it can be seen that the fuse function that cuts off the current when an overcurrent flows is working.

  On the other hand, in Example 7 (solid electrolytic capacitor B1), although the number of open circuits (fuse function confirmation test) was as good as 100, smoke was confirmed in some of the evaluation samples (six). In Example 7, the content of the heat-expandable graphite 4 contained in the second electrolyte layer 3b is as small as 5% by weight, and the capacitor is expanded before the heat-expandable graphite 4 expands and cuts off the current. This is presumed to be due to the smoke generation of the element 10.

  In Example 10 (solid electrolytic capacitor B4), the number of open circuits (fuse function confirmation test) was 100, which was a good result, but an increase in ESR was confirmed compared to Examples 4 and 7-9. It was done. This is because, in Example 10, the content of the thermally expandable graphite 4 is 65% by weight, and compared with the other examples, (a) the thermally expandable graphite 4 contained in the second electrolyte layer 3b is the cathode. There are many portions in contact with the layer 5 (conductive carbon layer 5a), and the interface resistance between the second electrolyte layer 3b and the cathode layer 5 (conductive carbon layer 5a) is increased, or (b) In the second electrolyte layer 3b, the proportion of the thermally expandable graphite 4 having no conductivity is large, and it is assumed that the resistance of the second electrolyte layer 3b is increased.

  From the above, in order to impart a fuse function to the solid electrolytic capacitor, a laminated film of the first electrolyte layer 3a and the second electrolyte layer 3b is formed as the electrolyte layer 3 as in the present invention, and the upper first layer is formed. It is effective to contain the heat-expandable graphite 4 inside the second electrolyte layer 3b, and particularly for the second electrolyte layer 3b containing the heat-expandable graphite 4, the content of the heat-expandable graphite 4 It can be seen that it is preferable to employ a material having a content of 10% by weight to 50% by weight.

<Experiment 3>
Next, in the electrolyte layer 3 constituted by the first electrolyte layer 3 a made of a manganese dioxide layer and the second electrolyte layer 3 b made of a conductive polymer layer containing the thermally expandable graphite 4, Evaluation on the effect of the heat-expandable graphite 4 contained in the electrolyte layer 3b was performed.

(Example 11)
In Example 11, Example 1 except that Step 3A of Example 1 is changed to Step 3I below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). A solid electrolytic capacitor C1 was produced in the same manner as described above. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 5 μm) made of a manganese dioxide layer and the second electrolyte layer 3b made of polypyrrole containing the thermally expandable graphite 4 are formed. An electrolyte layer 3 (total thickness: 100 μm) composed of (thickness t2: 95 μm) is formed.

  Step 3I: The anode body 1 on which the dielectric layer 2 is formed is dipped in a 0.5 wt% manganese nitrate solution, pulled up, and then subjected to heat treatment at 250 ° C. for about 10 minutes. This dipping / pulling / heat treatment operation is repeated three times. Subsequently, the dipping, pulling and heat treatment operations are repeated twice using a 10 wt% manganese nitrate solution. In this manner, the first electrolyte layer 3a (thickness t1: 5 μm) made of the manganese dioxide layer is formed on the dielectric layer 2.

Next, 10% by weight of pyrrole as a polymerizable monomer and 16% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A chemical polymerization liquid is prepared, and 25% by weight of thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion rate: 10 cm ³ / g) is uniformly added to the chemical polymerization liquid. Prepare a mixed solution. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction.
In this way, the second electrolyte layer 3b (thickness t2: 95 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

Example 12
In Example 12, Example 3 except that Step 3A of Example 1 is changed to Step 3J below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). A solid electrolytic capacitor C2 was produced in the same manner as described above. Thereby, on the surface of the dielectric layer 2, a first electrolyte layer 3 a (thickness t1: 9 μm) made of a manganese dioxide layer and a second electrolyte layer 3 b made of polypyrrole containing the thermally expandable graphite 4 are formed. An electrolyte layer 3 (total thickness: 100 μm) composed of (thickness t2: 91 μm) is formed.

  Step 3J: The anode body 1 on which the dielectric layer 2 is formed is dipped in a 0.5 wt% manganese nitrate solution, pulled up, and then subjected to heat treatment at 250 ° C. for about 10 minutes. This dipping / pulling / heat treatment operation is repeated three times. Subsequently, the operations of dipping, pulling up and heat treatment are similarly repeated 4 times using a 10 wt% manganese nitrate solution. In this manner, the first electrolyte layer 3a (thickness t1: 9 μm) made of the manganese dioxide layer is formed on the dielectric layer 2.

Next, 9.5% by weight of pyrrole as a polymerizable monomer and 15% by weight of iron (III) p-toluenesulfonate as an oxidant / doping agent are dissolved in a 5: 1 mixed solvent of ethanol and water. 24 wt% of thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature 300 ° C., expansion rate 10 cm ³ / g) is prepared with respect to the chemical polymerization solution. Prepare a uniformly mixed solution. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 91 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Example 13)
In Example 13, Example 1 except that Step 3A of Example 1 is changed to Step 3K below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). A solid electrolytic capacitor C3 was produced in the same manner as described above. Thereby, on the surface of the dielectric layer 2, a first electrolyte layer 3 a (thickness t1: 15 μm) made of a manganese dioxide layer and a second electrolyte layer 3 b made of polypyrrole containing the thermally expandable graphite 4 are formed. An electrolyte layer 3 (total thickness: 100 μm) composed of (thickness t2: 85 μm) is formed.

  Step 3K: The anode body 1 on which the dielectric layer 2 is formed is dipped in a 0.5 wt% manganese nitrate solution, pulled up, and then subjected to heat treatment at 250 ° C. for about 10 minutes. This dipping / pulling / heat treatment operation is repeated three times. Subsequently, the dipping, pulling up and heat treatment operations are similarly repeated 7 times using a 10 wt% manganese nitrate solution. In this way, the first electrolyte layer 3a (thickness t1: 15 μm) made of the manganese dioxide layer is formed on the dielectric layer 2.

Next, 9% by weight of pyrrole as a polymerizable monomer and 14% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A chemical polymerization liquid is prepared, and 22% by weight of thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion degree: 10 cm ³ / g) is uniformly added to the chemical polymerization liquid. Prepare a mixed solution. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 85 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Example 14)
In Example 14, Example 1 except that Step 3A of Example 1 is changed to the following Step 3L to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). A solid electrolytic capacitor C4 was produced in the same manner as described above. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 50 μm) made of a manganese dioxide layer and the second electrolyte layer 3b made of polypyrrole containing the thermally expandable graphite 4 are formed. An electrolyte layer 3 (total thickness: 100 μm) composed of (thickness t2: 50 μm) is formed.

  Step 3L: The anode body 1 on which the dielectric layer 2 is formed is dipped in a 0.5 wt% manganese nitrate solution, pulled up, and then subjected to heat treatment at 250 ° C. for about 10 minutes. This dipping / pulling / heat treatment operation is repeated three times. Subsequently, the operations of dipping, pulling up and heat treatment are similarly repeated 20 times using a 10 wt% manganese nitrate solution. In this way, the first electrolyte layer 3a (thickness t1: 50 μm) made of the manganese dioxide layer is formed on the dielectric layer 2.

Next, 5% by weight of pyrrole as a polymerizable monomer and 8% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A chemical polymerization liquid is prepared, and 13% by weight of thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion degree: 10 cm ³ / g) is uniformly added to the chemical polymerization liquid. Prepare a mixed solution. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 50 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Example 15)
In Example 15, Example 1 except that Step 3A of Example 1 is changed to Step 3M below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). A solid electrolytic capacitor C5 was produced in the same manner as described above. Thereby, on the surface of the dielectric layer 2, a first electrolyte layer 3 a (thickness t1: 90 μm) made of a manganese dioxide layer and a second electrolyte layer 3 b made of polypyrrole containing the thermally expandable graphite 4 are formed. An electrolyte layer 3 (total thickness: 100 μm) composed of (thickness t2: 10 μm) is formed.

  Step 3M: The anode body 1 on which the dielectric layer 2 is formed is dipped in a 0.5 wt% manganese nitrate solution, pulled up, and then subjected to heat treatment at 250 ° C. for about 10 minutes. This dipping / pulling / heat treatment operation is repeated three times. Subsequently, the dipping, lifting and heat treatment operations are repeated 36 times using a 10 wt% manganese nitrate solution. In this manner, the first electrolyte layer 3a (thickness t1: 90 μm) made of the manganese dioxide layer is formed on the dielectric layer 2.

Next, 1% by weight of pyrrole as a polymerizable monomer and 2% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent were dissolved in a 5: 1 mixed solvent of ethanol and water. A chemical polymerization solution is prepared, and 3% by weight of thermally expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion rate: 10 cm ³ / g) is uniformly added to the chemical polymerization solution. Prepare a mixed solution. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this way, the second electrolyte layer 3b (thickness t2: 10 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Example 16)
In Example 16, Example 3 except that Step 3A of Example 1 is changed to Step 3N below to form electrolyte layer 3 (first electrolyte layer 3a and second electrolyte layer 3b). A solid electrolytic capacitor C6 was produced in the same manner as described above. Thereby, on the surface of the dielectric layer 2, the first electrolyte layer 3a (thickness t1: 95 μm) made of a manganese dioxide layer and the second electrolyte layer 3b made of polypyrrole containing the thermally expandable graphite 4 are formed. An electrolyte layer 3 (total thickness: 100 μm) composed of (thickness t2: 5 μm) is formed.

  Step 3N: The anode body 1 on which the dielectric layer 2 is formed is immersed in a 0.5% by weight manganese nitrate solution, pulled up, and then subjected to heat treatment at 250 ° C. for about 10 minutes. This dipping / pulling / heat treatment operation is repeated three times. Subsequently, the dipping, lifting and heat treatment operations are repeated 38 times using a 10 wt% manganese nitrate solution. In this manner, the first electrolyte layer 3a (thickness t1: 90 μm) made of the manganese dioxide layer is formed on the dielectric layer 2.

Next, 0.5% by weight of pyrrole as a polymerizable monomer and 1% by weight of iron (III) p-toluenesulfonate as a dopant imparting agent and oxidizing agent are dissolved in a 5: 1 mixed solvent of ethanol and water. A thermally-expandable graphite powder (particulate powder) having a predetermined expansion performance (expansion start temperature: 300 ° C., expansion rate: 10 cm ³ / g) with respect to the chemical polymerization liquid is prepared by 1.5 weight. Prepare a mixed solution in which% is uniformly mixed. Then, the anode body 1 on which the first electrolyte layer 3a is formed is immersed in this mixed solution and left in the atmosphere for 2 hours to advance the polymerization reaction. In this manner, the second electrolyte layer 3b (thickness t2: 5 μm) made of polypyrrole is formed on the first electrolyte layer 3a. At this time, thermally expandable graphite 4 having a predetermined expansion performance is added to the inside of the second electrolyte layer 3b at a content of 50% by weight. The thermally expandable graphite 4 is uniformly added over the entire surface of the second electrolyte layer 3b formed on the surface of the first electrolyte layer 3a.

(Comparative Example 3)
FIG. 3 is a schematic cross-sectional view showing a partially enlarged view of the vicinity of the electrolyte layer of the solid electrolytic capacitor in Comparative Example 3. In Comparative Example 3, as shown in FIG. 3, except that the second electrolyte layer 3 b containing the thermally expandable graphite 4 was not formed on the first electrolyte layer 3 a as the electrolyte layer 3. A solid electrolytic capacitor Z was produced in the same manner as in Example 11. Specifically, in Comparative Example 3, the electrolyte layer 3 (first electrolyte layer 3a) is formed by changing the process 3I of Example 11 to the following process 3P. As a result, a first electrolyte layer 3 a (thickness t1: 100 μm) made of a manganese dioxide layer is formed as the electrolyte layer 3 on the surface of the dielectric layer 2. The comparative example 3 (solid electrolytic capacitor Z) is an example of a general solid electrolytic capacitor (solid electrolytic capacitor having no fuse function).

Step 3P: The anode body 1 on which the dielectric layer 2 is formed is dipped in a 0.5 wt% manganese nitrate solution, pulled up, and then subjected to heat treatment at 250 ° C. for about 10 minutes. This dipping / pulling / heat treatment operation is repeated three times. Subsequently, the operations of dipping, pulling up and heat treatment are similarly repeated 40 times using a 10 wt% manganese nitrate solution. In this way, the electrolyte layer 3 made only of the first electrolyte layer 3a (thickness t1: 100 μm) made of the manganese dioxide layer is formed on the dielectric layer 2.

(Evaluation)
About each solid electrolytic capacitor, it carried out similarly to Experiment 1, and evaluated the electrostatic capacitance and ESR, the fuse function confirmation test, and the combustion confirmation test. Table 3 shows the evaluation results of each solid electrolytic capacitor. In addition, each measured value of capacitance and ESR in Table 3 uses an average value of 100 solid electrolytic capacitor samples, and each value of specific capacitance and specific ESR is Comparative Example 3 (solid electrolytic capacitor Z). The measurement result in is normalized as 100.

As shown in Table 3, in Comparative Example 3 (solid electrolytic capacitor Z) in which a conventional fuse is not provided, the electric circuit is not opened even when an overcurrent is passed, and smoke is emitted from all 100 evaluation samples. It was confirmed that it would ignite. On the other hand, Examples 11 to 16 (solid electrolytic capacitors) in which the second electrolyte layer 3b containing the thermally expandable graphite 4 on the first electrolyte layer 3a made of a manganese dioxide layer was adopted as the electrolyte layer 3. In each of C1 to C6), the number of open circuits is 100, and it can be seen that the fuse function that cuts off the current when an overcurrent flows is working. This is because, as in Experiment 1, by allowing the second electrolyte layer 3b to contain the thermally expandable graphite 4, the thermal expandable graphite 4 expands due to the heat generated by the capacitor element 10 when an overcurrent flows. This is probably because an electric gap was generated in the second electrolyte layer 3b, and as a result, the current flowing through the solid electrolytic capacitor (capacitor element 10) could be cut off.

  On the other hand, in Example 11 (solid electrolytic capacitor C1), although the number of open circuits (fuse function confirmation test) was as good as 100, a decrease in capacitance was confirmed compared to Examples 12-16. It was done. In Example 11, in the electrolyte layer 3 composed of the first electrolyte layer 3a and the second electrolyte layer 3b, the coverage with the lower layer compared to the first electrolyte layer 3a (manganese dioxide layer). The ratio of the poor second electrolyte layer 3b (polypyrrole) is large, and the effective contact area of the second electrolyte layer 3b with the dielectric layer 2 via the first electrolyte layer 3a (increase / decrease in capacitance) It is presumed that the contact area between the polypyrrole and the dielectric layer 2 that contributes to the decrease is reduced.

  In Example 16 (solid electrolytic capacitor C6), although the number of open circuits (fuse function confirmation test) showed good results, smoke was confirmed in some of the evaluation samples (seven). This is because the thickness of the second electrolyte layer 3b (second electrolyte layer 3b containing the thermally expandable graphite 4) constituting the electrolyte layer 3 in Example 16 is as thin as 5 μm. It is presumed that the capacitor element 10 smoked before the expansion was started and the current was cut off.

  In addition to the above evaluation, in the electrolyte layer 3 constituted by the first electrolyte layer 3a made of a manganese dioxide layer and the second electrolyte layer 3b made of a conductive polymer layer, the second electrolyte layer 3b It is confirmed that when the thermal expansive graphite 4 is not contained in the electric circuit, the electric circuit is not opened even when an overcurrent flows in all the evaluation samples, and smoke is generated and ignition is caused.

  From the above, in order to impart a fuse function to a solid electrolytic capacitor while maintaining the configuration of a solid electrolytic capacitor without a conventional fuse, the first electrolyte layer 3a and the first electrolyte layer 3 are used as the electrolyte layer 3 as in the present invention. It is effective to form a laminated film with the second electrolyte layer 3b, use a manganese dioxide layer as the lower first electrolyte layer 3a, and contain the thermally expandable graphite 4 in the upper second electrolyte layer 3b. It turns out that it is. In particular, in order to provide a solid electrolytic capacitor with a fuse function without causing a decrease in capacitance and smoke generation of the capacitor element, the first electrolyte layer with respect to the thickness t2 of the second electrolyte layer 3b constituting the electrolyte layer 3 is used. The ratio of the thickness t1 of 3a (t1 / t2) is preferably in the range of 0.1 to 9.0.

  According to the solid electrolytic capacitor of the present embodiment, the following effects can be obtained.

  (1) As the electrolyte layer 3, the first electrolyte layer 3a is provided on the dielectric layer 2, the second electrolyte layer 3b is provided thereon, and the thermally expandable graphite 4 is contained inside the second electrolyte layer 3b. By doing so, it is possible to give the solid electrolytic capacitor a fuse function for cutting off a current when an overcurrent flows through the capacitor element 10.

  (2) The first electrolyte layer 3a is provided on the dielectric layer 2 as the electrolyte layer 3, and the second electrolyte layer 3b is provided thereon, and the thermally expandable graphite 4 is contained inside the second electrolyte layer 3b. By doing so, the effect of the above (1) can be enjoyed while maintaining the configuration of the solid electrolytic capacitor without the conventional fuse, that is, without increasing the size of the solid electrolytic capacitor.

  (3) By changing the conventional electrolyte layer to a laminated film of the first electrolyte layer 3a and the second electrolyte layer 3b containing the thermally expandable graphite 4, a solid electrolytic capacitor having a fuse function is obtained. Therefore, compared with the conventional solid electrolytic capacitor with a built-in fuse, such a solid electrolytic capacitor can be reduced in size.

  (4) As the electrolyte layer 3, a first electrolyte layer 3a and a second electrolyte layer 3b are provided on the dielectric layer 2, and the thermally expandable graphite 4 is provided only inside the second electrolyte layer 3b. By containing, the effect of said (1)-(3) can be enjoyed, suppressing the fall of an electrostatic capacitance, or the increase in ESR.

  (5) Since the thermally expandable graphite 4 is distributed over the entire surface of the second electrolyte layer 3b formed on the first electrolyte layer 3a, the entire surface of the second electrolyte layer 3b is electrically exposed by a thermal load. A gap can be generated, and the current flowing through the capacitor element 10 can be reliably cut off. For this reason, the fuse function as described in said (1)-(4) can be worked more reliably.

  (6) By adopting a conductive polymer layer such as polypyrrole as the second electrolyte layer 3b, the thermally expandable graphite 4 at a lower temperature (for example, room temperature 25 ° C.) than when a manganese dioxide layer is employed. Therefore, the production yield of solid electrolytic capacitors can be improved. This is because, when a manganese dioxide layer is employed as the second electrolyte layer 3b, a part of the thermally expandable graphite 4 expands due to a high temperature (for example, 250 ° C.) in the thermal decomposition step, and the second electrolyte This is because the layer 3b itself may be damaged.

  (7) By adopting a conductive polymer layer such as polypyrrole as the second electrolyte layer 3b, compared with the case where a manganese dioxide layer is adopted, the ignition property when overcurrent flows and generates heat is reduced. Can do. For this reason, the reliability (safety) of the solid electrolytic capacitor in the event of an erroneous connection or failure can be further improved. This is because when the second electrolyte layer 3b is composed of a manganese dioxide layer, oxygen is released from the manganese dioxide layer by the heat generated when an overcurrent flows, whereas the conductive polymer layer In some cases, the amount of oxygen contained therein is small, and the release of oxygen as in the manganese dioxide layer is reduced.

  (8) By adopting a conductive polymer layer such as polypyrrole as the first electrolyte layer 3a, as in (7) above, when an overcurrent flows and heat is generated, compared to the case of employing a manganese dioxide layer. Therefore, the reliability (safety) of the solid electrolytic capacitor can be improved.

  (9) By adopting the manganese dioxide layer as the first electrolyte layer 3a, the capacitance of the solid electrolytic capacitor having a fuse function can be increased as compared with the case where the conductive polymer layer is employed. . This is because the coverage of the manganese dioxide layer with respect to the dielectric layer 2 is higher than that of the conductive polymer layer.

  (10) ESR in a solid electrolytic capacitor having a fuse function as compared with the case where a manganese dioxide layer is included by employing a conductive polymer layer for both the first electrolyte layer 3a and the second electrolyte layer 3b. Can be reduced. This is because the electric conductivity of the conductive polymer layer is higher than that of the manganese dioxide layer.

  (11) In the electrolyte layer 3, the ratio (t1 / t2) of the thickness t1 of the first electrolyte layer 3a to the thickness t2 of the second electrolyte layer 3b is preferably in the range of 0.1 to 9.0. Thereby, an electric current can be reliably interrupted at the time of a short circuit without causing an increase in ESR, a decrease in capacitance, and smoke generation of the capacitor element.

  (12) The thickness t1 of the first electrolyte layer 3a constituting the electrolyte layer 3 is preferably 10 μm or more. Thereby, an electric current can be reliably interrupted at the time of a short circuit, without causing the fall of an electrostatic capacitance.

  (13) For the second electrolyte layer 3b containing the thermally expandable graphite 4, it is preferable to employ a layer in which the content of the thermally expandable graphite 4 is in the range of 10 wt% to 50 wt%. As a result, the current can be reliably interrupted during a short circuit without causing an increase in ESR and smoke generation of the capacitor element.

  (14) By changing the conventional electrolyte layer to a laminated film of the first electrolyte layer 3a and the second electrolyte layer 3b containing the thermally expandable graphite 4, a solid electrolytic capacitor having a fuse function is obtained. Therefore, compared with the conventional solid electrolytic capacitor with a built-in fuse, the cost of such a solid electrolytic capacitor can be reduced.

  (15) When the thermally expandable graphite 4 is contained in the electrolyte layer 3 (second electrolyte layer 3b) constituting the solid electrolytic capacitor, the expansion starts higher than the temperature at which the solder member melts during reflow (mounting temperature). It is preferable to employ the heat-expandable graphite 4 having a temperature, whereby the solder member can be welded without expanding the heat-expandable graphite 4. That is, the solid electrolytic capacitor is mounted via the solder member without causing an electrical gap inside the electrolyte layer 3 (second electrolyte layer 3b) during solder reflow and damaging the solid electrolytic capacitor (capacitor element 10). It can be mounted on a substrate. For this reason, the manufacturing yield of such a mounting substrate can be improved.

  (16) In the environment of a temperature of 300 ° C., the thermally expansive graphite 4 expands and no current flows through the capacitor element 10 (between the anode terminal 6 and the cathode terminal 7). Since heat generation (excessive heat generation) can be prevented, the reliability (safety) of the solid electrolytic capacitor in the event of an erroneous connection or failure can be improved. Note that the environment at a temperature of 300 ° C. indicates a state in which the solid electrolytic capacitor (or a mounting substrate on which the capacitor is mounted) is heated to a temperature of 300 ° C. or exposed to an atmosphere at a temperature of 300 ° C.

  The present invention is not limited to the above-described embodiment, and various modifications such as design changes can be added based on the knowledge of those skilled in the art, and the embodiment to which such a modification is added. Can also be included in the scope of the present invention.

  In the said embodiment, although the example of the solid electrolytic capacitor which employ | adopted the anode body which consists of a porous sintered compact of the metal particle which consists of a valve action metal was shown, this invention is not limited to this. For example, a solid electrolytic capacitor employing an anode foil made of a valve metal may be used. In this case, the same effect can be enjoyed.

  In the said embodiment, although the example which formed the 2nd electrolyte layer containing a thermally expansible graphite using the chemical polymerization method was shown, this invention is not limited to this. For example, it may be formed using an electrolytic polymerization method, or may be formed by combining a chemical polymerization method and an electrolytic polymerization method. In such a case, the same effect can be enjoyed.

  In the said embodiment, although the example which employ | adopted particulate-form heat-expandable graphite powder was shown, this invention is not limited to this. For example, a flaky thermally expandable graphite powder or a mixed powder of particles and flakes may be used. In such a case, the same effect can be enjoyed.

(A) The schematic sectional drawing which shows the structure of the solid electrolytic capacitor which concerns on this embodiment, (B) The elements on larger scale near the electrolyte layer in the solid electrolytic capacitor. The schematic diagram which shows the state before and after a thermally expansible graphite expand | swells with a heat load. The elements on larger scale of the electrolyte layer vicinity in the solid electrolytic capacitor of the comparative example 1 and the comparative example 3 are shown. The elements on larger scale of the electrolyte layer vicinity in the solid electrolytic capacitor of the comparative example 2 are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode body, 1a Anode lead wire, 2 Dielectric layer, 3 Electrolyte layer, 3a 1st electrolyte layer, 3b 2nd electrolyte layer, 4 Thermal expansible graphite, 4a Graphite crystal, 4b Interlayer, 5 Cathode layer, 5a conductive carbon layer, 5b silver paste layer, 6 anode terminal, 7 cathode terminal, 8
Mold outer package, 10 capacitor element.

Claims (9)

A solid electrolytic capacitor in which a dielectric layer, an electrolyte layer, and a cathode layer are sequentially formed on the surface of the anode body,
The electrolyte layer includes a first electrolyte layer formed on the dielectric layer, and a second electrolyte layer formed on the first electrolyte layer,
The solid electrolytic capacitor, wherein the second electrolyte layer contains thermally expandable graphite.   The solid electrolytic capacitor according to claim 1, wherein the thermally expandable graphite is contained only in the second electrolyte layer.   The solid electrolytic capacitor according to claim 1, wherein the thermally expandable graphite is distributed over the entire surface of the second electrolyte layer.   The solid electrolytic capacitor according to claim 1, wherein the second electrolyte layer is made of a conductive polymer.   The ratio of the thickness t1 of the first electrolyte layer to the thickness t2 of the second electrolyte layer (t1 / t2) of the electrolyte layer is in the range of 0.1 to 9.0. Solid electrolytic capacitor as described in any one of -4.   The solid electrolytic capacitor according to claim 1, wherein the electrolyte layer has a thickness of the first electrolyte layer of 10 μm or more.   The content of the thermally expandable graphite is in a range of 10 wt% to 50 wt% with respect to the total weight of the second electrolyte layer. Solid electrolytic capacitor.   The solid electrolytic capacitor according to claim 1, wherein the first electrolyte layer is made of a conductive polymer.   The environment according to any one of claims 1 to 8, wherein the thermally expandable graphite expands in an environment of a temperature of 300 ° C, and a current does not flow between the anode body and the cathode layer. Solid electrolytic capacitor.

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