Method for manufacturing solid electrolytic capacitor, and solid electrolytic capacitor

0001The present invention relates to a method for manufacturing a solid electrolytic capacitor and a solid electrolytic capacitor.

0002Conventionally, a method for manufacturing a solid electrolytic capacitor using only manganese dioxide as a solid electrolyte, a method for manufacturing a solid electrolytic capacitor using only a conductive polymer for a solid electrolyte, and manganese dioxide and a conductive polymer for a solid electrolyte have been used. A method for manufacturing a solid electrolytic capacitor using the above (see, for example, Patent Documents 1 to 3) is known.

0003Patent Document 1 describes solid electrolysis in which a conductive polymer is formed in an island shape on the surface of a dielectric oxide film, and then a manganese dioxide layer is formed on the entire surface of the dielectric oxide film so as to cover the conductive polymer. A method for manufacturing a capacitor is disclosed.

0004According to this manufacturing method, a conductive polymer having a higher conductivity than manganese dioxide is formed on the surface of the dielectric oxide film, so that the ESR characteristics are superior to those of a solid electrolytic capacitor using only manganese dioxide as a solid electrolyte. A solid electrolytic capacitor can be obtained. Further, according to this manufacturing method, a manganese dioxide layer having good adhesion to the dielectric oxide film is formed on the entire surface of the dielectric oxide film so as to cover the island-shaped conductive polymer, so that it is conductive. The adhesion between the polymer and the dielectric oxide film can be improved.

0005Patent Document 2 describes a solid in which a manganese dioxide layer having a thickness of 1 μm or more is formed on the entire surface of a dielectric oxide film, and then a conductive polymer layer is formed on the surface of the manganese dioxide layer by chemical polymerization using an oxidizing agent. A method for manufacturing an electrolytic capacitor is disclosed.

0006According to this production method, since the manganese dioxide layer is formed on the entire surface of the dielectric oxide film, the dielectric oxide film is directly exposed to the acid during chemical polymerization, and the dielectric oxide film is damaged. Can be prevented.

0007Further, in Patent Document 3, an anode having a manganese dioxide layer formed on the entire surface of a dielectric oxide film is immersed in a suspension aqueous solution in which a powder of a conductive polymer is suspended to form a manganese dioxide layer. A method for manufacturing a solid electrolytic capacitor that forms a conductive polymer layer on the surface is disclosed.

0008According to this production method, a conductive polymer layer having a uniform and sufficient thickness can be formed on the surface of the manganese dioxide layer by immersing it in a suspended aqueous solution. Therefore, the manganese dioxide layer can be formed due to thermal stress during mounting or the like. It is possible to prevent the ESR characteristics and the leakage current characteristics from being deteriorated due to damage to the dielectric oxide film.

<p num="0009"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2008-263167</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 6-69082</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2006-147900</text></patcit></p>

<p num="0010"> However, the solid electrolytic capacitor manufactured by the manufacturing method described in Patent Document 1 is solid because the manganese dioxide layer is formed on the entire surface of the dielectric oxide film so as to cover the island-shaped conductive polymer. Compared with a solid electrolytic capacitor that uses only a conductive polymer as the electrolyte, the ESR characteristics will be inferior. Moreover, in this production method, since the manganese dioxide layer is formed after forming the island-shaped conductive polymer, the island-shaped conductive polymer is deteriorated by the heat treatment performed at the time of forming the manganese dioxide layer, and the island-shaped conductive polymer is further deteriorated. ESR characteristics deteriorate.</p><p num="0011"> Further, in the solid electrolytic capacitor manufactured by the manufacturing method described in Patent Document 2, since a manganese dioxide layer having a thickness of 1 μm or more is formed between the dielectric oxide film and the conductive polymer layer, it is a solid electrolyte. Compared to a solid electrolytic capacitor that uses only a conductive polymer, the ESR characteristics will be inferior.</p><p num="0012"> The solid electrolytic capacitor manufactured by the manufacturing method described in Patent Document 3 also has a manganese dioxide layer formed on the entire surface of the dielectric oxide film, so that the solid electrolytic capacitor uses only a conductive polymer as the solid electrolyte. Compared with, the ESR characteristics will be inferior. Further, in general, since the conductive polymer of the suspended aqueous solution has a relatively large particle size, the conductive polymer may not reach the inside of the anode. Therefore, in this manufacturing method, the contact portion between the conductive polymer layer and the manganese dioxide layer is reduced, and the ESR characteristics may be further deteriorated.</p><p num="0013"> That is, all of the solid electrolytic capacitors manufactured by the manufacturing methods described in Patent Documents 1 to 3 have the merit of forming the manganese dioxide layer, while only the conductive polymer is used as the solid electrolyte. There was a problem that the ESR characteristics were inferior to those of solid electrolytic capacitors.</p><p num="0014"> The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor having excellent ESR characteristics and a solid electrolytic capacitor.</p>

<p num="0015"> In order to solve the above problems, the method for manufacturing a solid electrolytic capacitor according to the present invention is as follows: (1) A surface of a sintered body obtained by sintering a molded body made of a valve acting metal powder, or a roughened valve. A method for manufacturing a solid electrolytic capacitor in which a dielectric oxide film is formed on the surface of a working metal foil to form an anode and a solid electrolyte layer is formed on the surface of the anode. As a step of forming a solid electrolyte layer, a dielectric is used. A protrusion forming step of forming island-like protrusions made of manganese dioxide having an average diameter of 10 to 102 nm on the surface of the oxide film so that the coverage is 1 to 20%, and the protrusions and the dielectric It is characterized in that a conductive polymer layer forming step of forming a conductive polymer layer on the surface of the oxide film is performed.</p><p num="0016"> According to this configuration, protrusions made of manganese dioxide are scattered on the surface of the dielectric oxide film in an island shape, so that the conductive polymer layer can be brought into contact with the dielectric oxide film between the protrusions. .. Therefore, according to this configuration, deterioration of ESR characteristics due to the use of manganese dioxide can be suppressed.</p><p num="0017"> Further, according to this configuration, the conductive high since a plurality of protrusions formed on the surface of the dielectric oxide film at the time of the molecular layer formation is in a state where biting the conductive polymer layer, the dielectric oxide film and the conductive Adhesion with the conductive polymer layer can be improved. Therefore, according to this configuration, the ESR characteristics can be improved, and it is possible to prevent the conductive polymer layer from peeling from the dielectric oxide film due to heat stress or the like and deteriorating the ESR characteristics and the leakage current characteristics. be able to.</p><p num="0018"> Further, according to this configuration, when the conductive polymer layer is formed by chemical polymerization, the retention amount of the polymer solution is increased by the plurality of protrusions, so that the capacity appearance rate (internal impregnation property) can be improved. Therefore, according to this configuration, it is possible to easily manufacture a large-capacity solid electrolytic capacitor and reduce the number of times of immersion in the polymer solution.</p><p num="0019"> The "average diameter" in the present invention means the average value of the major axis (maximum diameter) of the protrusions when viewed in a plan view.</p><p num="0020"> In the manufacturing method of (1) above, for example, in the step of forming the protrusion, the humidity of the anode is 8 g / m.³The pretreatment step of leaving in the above humidified environment, the dipping treatment step of immersing the anode body after the pretreatment step in the manganese nitrate aqueous solution, and the humidity of the anode body after the dipping treatment step of 8 g / m.³It can be configured to include an intermediate treatment step of leaving the anode in the above humidified environment and a heat treatment step of causing the anode body after the intermediate treatment step to undergo a thermal decomposition reaction in an atmosphere of a predetermined relative humidity.</p><p num="0021"> In the production method of (2) above, it is more preferable that a surfactant is added to the aqueous solution of (3) manganese nitrate.</p><p num="0022"> According to this configuration, the surface tension can be lowered by the surfactant, so that the internal impregnation property of the manganese nitrate aqueous solution into the anode body can be improved.</p><p num="0023"> In the production method of (2) or (3) above, for example, (4) the predetermined relative humidity can be set to 50 to 80%.</p><p num="0024"> In the above-mentioned production methods (1) to (4), a rechemical formation step of regenerating the dielectric oxide film may be further performed between the (5) protrusion forming step and the conductive polymer layer forming step. ..</p><p num="0025"> According to this configuration, the defect of the dielectric oxide film is repaired by the rechemical formation step, so that the leakage current characteristic can be improved.</p><p num="0026"> In the production methods (1) to (5) above, it is preferable to form the conductive polymer layer by chemical polymerization in the step (6) for forming the conductive polymer layer.</p><p num="0027"> Further, in order to solve the above problems, the solid electrolytic capacitor according to the present invention has (7) a valve action on the surface of a sintered body obtained by sintering a molded body made of a metal powder or a roughened valve action. A solid electrolytic capacitor in which a dielectric oxide film is formed on the surface of a metal foil and a solid electrolyte layer is formed on the surface of the dielectric oxide film. The solid electrolyte layer has a coverage of 1 on the surface of the dielectric oxide film. A plurality of protrusions made of manganese dioxide having an average diameter of 10 to 102 nm, which are scattered in an island shape so as to be ~ 20%, and a conductive polymer formed on the protrusions and the surface of the dielectric oxide film. It is characterized by being composed of layers.</p><p num="0028"> According to this configuration, since the conductive polymer layer is in contact with the dielectric oxide film between the protrusions made of manganese dioxide, it is possible to prevent deterioration of the ESR characteristics due to the use of manganese dioxide.</p><p num="0029"> Further, according to this configuration, a plurality of protrusions formed on the surface of the dielectric oxide film bite into the conductive polymer layer, and the adhesion between the dielectric oxide film and the conductive polymer layer is improved. Therefore, the ESR characteristics can be improved, and it is possible to prevent the conductive polymer layer from peeling from the dielectric oxide film due to thermal stress or the like and deteriorating the ESR characteristics and the leakage current characteristics.</p><p num="0030"> Further, according to this configuration, when the conductive polymer layer is formed by chemical polymerization, the retention amount of the polymer solution can be increased by the plurality of protrusions, so that the capacity appearance rate (internal impregnation property) is improved. As a result, the capacitance can be improved.</p>

<p num="0031"> According to the present invention, it is possible to provide a method for manufacturing a solid electrolytic capacitor having excellent ESR characteristics and a solid electrolytic capacitor.</p>

0032<figref num="1">It is a flow chart of the manufacturing method of the solid electrolytic capacitor which concerns on one Example of this invention.</figref><figref num="2">It is a flow chart of the protrusion formation process in this invention.</figref>

0033Hereinafter, a method for manufacturing a solid electrolytic capacitor and a preferred embodiment of the solid electrolytic capacitor according to the present invention will be described with reference to the accompanying drawings.

0034[Example 1] FIG. 1 shows a method for manufacturing a solid electrolytic capacitor according to a first embodiment of the present invention. As shown in the figure, in this example, the porous body preparation step (S1) and the oxide film forming step (S2) were first performed.

0035In the porous body preparation step (S1), an anode lead was embedded in tantalum powder, press-molded, and then sintered to prepare a rectangular parallelepiped porous body (sintered body) of 1.0 mm × 1.5 mm × 0.5 mm. ..

0036In the oxide film forming step (S2), the porous body prepared in the porous body manufacturing step (S1) is anodized in an aqueous phosphoric acid solution at an applied voltage of 10 V to form a dielectric oxide film on the surface of the porous body. did. As a result, an anode body was obtained.

0037Next, as a step of forming the solid electrolyte layer (solid electrolyte forming step), a protrusion forming step (S3) in which protrusions made of manganese dioxide are interspersed on the surface of the dielectric oxide film and a protrusion are formed. Then, a conductive polymer layer forming step (S4) was performed in which a conductive polymer layer was formed on the surface of the dielectric oxide film. The plurality of protrusions and the conductive polymer layer made of manganese dioxide correspond to the "solid electrolyte layer" of the present invention.

0038In the protrusion forming step (S3), as shown in FIG. 2, a pretreatment step (S3-1), a dipping treatment step (S3-2), an intermediate treatment step (S3-3), and a heat treatment step (S3-4) Was performed in this order.

0039In the pretreatment step (S3-1), the anode body obtained in the oxide film forming step (S2) is subjected to a temperature of 30 ° C and a humidity of 8 g / m.³It was left in a humidified environment for 30 minutes.

0040In the dipping treatment step (S3-2), the anode body after the pretreatment step (S3-1) was immersed in a manganese nitrate aqueous solution having a manganese nitrate concentration of 20 wt%. To the aqueous manganese nitrate solution, 1 wt% of a surfactant composed of polyoxyethylene alkyl ether was added.

0041In the intermediate treatment step (S3-3), the anode body after the immersion treatment step (S3-2) is again subjected to a temperature of 30 ° C and a humidity of 8 g / m.³It was left in a humidified environment for 30 minutes.

0042In the heat treatment step (S3-4), the anode body after the intermediate treatment step (S3-3) was heat-treated in an atmosphere of a temperature of 250 ° C. and a relative humidity of 80% to adhere to the surface of the dielectric oxide film. Manganese nitrate was thermally decomposed to form island-shaped protrusions made of manganese dioxide. Specifically, the coverage of all the protrusions on the surface of the dielectric oxide film was 10%, and the average diameter of the protrusions was 10 nm.

0043Here, the coverage rate indicates the ratio of the coating of the protrusions made of manganese dioxide formed on the surface of the dielectric oxide film to the dielectric oxide film. Specifically, the capacitance value after the conductive solution is sufficiently contained in the capacitor element after forming the protrusion made of manganese dioxide (capacitor value originally possessed by the capacitor element: capacitance value A) and the above-mentioned capacitor element. It was calculated from the capacitance value after the conductive solution was washed from the inside and the water was sufficiently dried (capacitor value actually possessed by the capacitor element after forming the protrusion made of manganese dioxide: capacitance value B). The formula for calculating the coverage is shown below.

0044<maths num="1"><img id="000002" he="24" wi="156" file="JP5933397B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>

0045In the conductive polymer layer forming step (S4), a monomer solution containing 3,4-ethylenedioxythiophene and an oxidizing agent solution containing ferric p-toluenesulfonate are mixed and kept at a temperature of -5 ° C. The anode body after the protrusion forming step (S3) was immersed in the mixed solution (polymerization solution), pulled up, and then chemically polymerized at a temperature of 25 ° C. In this example, the conductive polymer layer forming step (S4) was repeated a total of 7 times to form the conductive polymer layer.

0046In the conductive polymer layer forming step (S4), as the oxidizing agent contained in the oxidizing agent solution, one having a stronger oxidizing power than manganese dioxide (in this example, ferric p-toluenesulfonate) is used. Therefore, it can be said that manganese dioxide in the protrusions was not substantially consumed as an oxidizing agent during chemical polymerization.

0047Next, a carbon paste and a silver paste are applied to the surface of the conductive polymer layer formed in the conductive polymer layer forming step (S4) and dried to form a cathode layer composed of the carbon layer and the silver layer. A layer forming step (S5) was performed.

0048Finally, by connecting the cathode terminal to the surface of the cathode layer and connecting the anode terminal to the anode lead protruding from the anode body, and then applying the exterior resin by transfer molding, a solid with a rating of 4V-100μF (2012 size). The assembly process (S6) for manufacturing the electrolytic capacitor was performed.

0049[Example 2] The method for manufacturing the solid electrolytic capacitor according to Example 2 of the present invention is that (1) the manganese nitrate concentration of the manganese nitrate aqueous solution used in the immersion treatment step (S3-2) is 5 wt%, and (2) the heat treatment step (2). It is common to the method for manufacturing a solid electrolytic capacitor according to Example 1 except that the relative humidity of S3-4) is 70%. In this example, the coverage of all the protrusions on the surface of the dielectric oxide film was 1%, and the average diameter of the protrusions was 48 nm.

0050[Example 3] The method for manufacturing a solid electrolytic capacitor according to Example 3 of the present invention is common to the method for manufacturing a solid electrolytic capacitor according to Example 1 except that the relative humidity in the heat treatment step (S3-4) is 70%. doing. In this example, the coverage of all the protrusions on the surface of the dielectric oxide film was 10%, and the average diameter of the protrusions was 51 nm.

0051[Example 4] The method for producing the solid electrolytic capacitor according to Example 4 of the present invention is as follows: (1) No surfactant is added to the manganese nitrate aqueous solution used in the immersion treatment step (S3-2), and (2) Heat treatment step (2) It is common to the method for manufacturing a solid electrolytic capacitor according to Example 1 except that the relative humidity of S3-4) is 70%. In this example, the coverage of all the protrusions on the surface of the dielectric oxide film was 9%, and the average diameter of the protrusions was 50 nm.

0052[Example 5] The method for manufacturing a solid electrolytic capacitor according to Example 5 of the present invention is as follows: (1) the relative humidity of the heat treatment step (S3-4) is 70%, and (2) the protrusion forming step (S3) and high conductivity. It is common to the method for manufacturing a solid electrolytic capacitor according to Example 1 except that one re-formulation step was performed between the process and the molecular layer forming step (S4). In the rechemical formation step, anodizing was performed in an aqueous phosphoric acid solution at an applied voltage of 8 V to regenerate the dielectric oxide film. In this example, the coverage of all the protrusions on the surface of the dielectric oxide film was 10%, and the average diameter of the protrusions was 51 nm.

0053[Example 6] In the method for manufacturing a solid electrolytic capacitor according to Example 6 of the present invention, (1) the relative humidity in the heat treatment step (S3-4) is 70%, and (2) the protrusion forming step (S3) is performed twice in total. Other than what was done, it is common to the method for manufacturing a solid electrolytic capacitor according to Example 1. In this example, the coverage of all the protrusions on the surface of the dielectric oxide film was 20%, and the average diameter of the protrusions was 54 nm.

0054[Example 7] The method for manufacturing a solid electrolytic capacitor according to Example 7 of the present invention is common to the method for manufacturing a solid electrolytic capacitor according to Example 1 except that the relative humidity in the heat treatment step (S3-4) is 50%. doing. In this example, the coverage of all the protrusions on the surface of the dielectric oxide film was 11%, and the average diameter of the protrusions was 102 nm.

0055[Conventional example] The manufacturing method of the solid electrolytic capacitor in the conventional example is other than (1) the step of forming the protrusion (S3) was not performed, and (2) the step of forming the conductive polymer layer (S4) was performed 10 times in total. The points are common to the method for manufacturing the solid electrolytic capacitor according to the first embodiment.

0056[Comparative example 1] The method for manufacturing the solid electrolytic capacitor in Comparative Example 1 is common to the method for manufacturing the solid electrolytic capacitor according to Example 1 except that the protrusion forming step (S3) was not performed. In other words, the method for manufacturing the solid electrolytic capacitor in Comparative Example 1 is common to the method for manufacturing the solid electrolytic capacitor in the conventional example except that the conductive polymer layer forming step (S4) was performed a total of 7 times. ing.

0057[Comparative example 2] The method for manufacturing the solid electrolytic capacitor in Comparative Example 2 is common to the method for manufacturing the solid electrolytic capacitor according to Example 1 except that the relative humidity in the heat treatment step (S3-4) is 90%. In Comparative Example 2, the coverage of all the protrusions on the surface of the dielectric oxide film was 10%, and the average diameter of the protrusions was 5 nm.

0058[Comparative example 3] The manufacturing method of the solid electrolytic capacitor in Comparative Example 3 was that (1) the relative humidity of the heat treatment step (S3-4) was 70%, and (2) the protrusion forming step (S3) was performed a total of three times. The points other than the above are common to the method for manufacturing the solid electrolytic capacitor according to the first embodiment. In Comparative Example 3, the coverage of all the protrusions on the surface of the dielectric oxide film was 29%, and the average diameter of the protrusions was 57 nm.

0059[Comparative example 4] The method for manufacturing the solid electrolytic capacitor in Comparative Example 4 is common to the method for manufacturing the solid electrolytic capacitor according to Example 1 except that the relative humidity in the heat treatment step (S3-4) is 20%. In Comparative Example 4, the coverage of all the protrusions on the surface of the dielectric oxide film was 11%, and the average diameter of the protrusions was 160 nm.

0060Table 1 summarizes the main manufacturing conditions of the solid electrolytic capacitor manufacturing methods in Examples 1 to 7, Conventional Examples and Comparative Examples 1 to 4.

0061<tables num="1"><img id="000003" he="88" wi="156" file="JP5933397B2_D0001.tif" img-format="tif" img-content="drawing" /></tables>

0062Average diameter of protrusions, coverage of protrusions, capacitance, ESR, leakage current of each solid electrolytic capacitor manufactured by the methods for manufacturing solid electrolytic capacitors in Examples 1 to 7, Conventional Examples and Comparative Examples 1 to 4. Table 2 shows the ESR values after the heat resistance test and the leakage current values after the heat resistance test. The values shown in Table 2 are the average values of 12 solid electrolytic capacitors. In the heat resistance test shown in Table 2, reflow was performed at a temperature of 240 ° C for 10 seconds.

0063<tables num="2"><img id="000004" he="94" wi="156" file="JP5933397B2_D0001.tif" img-format="tif" img-content="drawing" /></tables>

0064(Presence or absence of protrusions) From Table 2, the solid electrolytic capacitors in Examples 1 to 7 have ESR characteristics, capacitance, and leakage as compared with the solid electrolytic capacitors in the conventional example and Comparative Example 1 in which a plurality of protrusions made of manganese dioxide are not formed. It can be seen that the current characteristics, the ESR characteristics after the heat resistance test, and the leakage current characteristics after the heat resistance test are excellent.

0065It is considered that the excellent ESR characteristics are due to the contact between the dielectric oxide film and the conductive polymer layer and the high adhesion between the dielectric oxide film and the conductive polymer layer. Specifically, in the production methods of Examples 1 to 7, protrusions made of manganese dioxide are scattered on the surface of the dielectric oxide film in an island shape, so that the dielectric oxide film is conductive between the protrusions. It is considered that the polymer layers can be brought into contact with each other and the deterioration of ESR characteristics due to the use of manganese dioxide can be suppressed. Further, in the production methods of Examples 1 to 7, a plurality of protrusions formed on the surface of the dielectric oxide film are in a state of being bitten into the conductive polymer layer when the conductive polymer layer is formed, so that the dielectric material is formed. It is considered that the adhesion between the oxide film and the conductive polymer layer can be improved, and the ESR characteristics can be improved.

0066The excellent capacitance is due to the large contact area between the dielectric oxide film and the conductive polymer layer. Specifically, in the production methods of Examples 1 to 7, since the amount of the polymer solution retained is increased by the plurality of protrusions, the capacity appearance rate (internal impregnation property) can be improved. As a result, the contact area between the dielectric oxide film and the conductive polymer layer can be increased, so that the capacitance can be improved.

0067It is considered that the excellent leakage current characteristics are due to the formation of a plurality of protrusions made of manganese dioxide. Manganese dioxide has higher strength than conductive polymers and is resistant to external stress, so it has better leakage current characteristics than conductive polymers. Therefore, in the manufacturing methods of Examples 1 to 7, the leakage current characteristics can be improved.

0068The excellent ESR after the heat resistance test and the leakage current after the heat resistance test are due to the increased adhesion between the dielectric oxide film and the conductive polymer layer as described above, and the conductive polymer layer against thermal stress. It is considered that this is because it became difficult to peel off from the dielectric oxide film.

0069Further, the solid electrolytic capacitor in Comparative Example 1 is inferior in capacitance, ESR characteristics, ESR characteristics after heat resistance test, and leakage current characteristics after heat resistance test as compared with the solid electrolytic capacitor in the conventional example. It is considered that this is because in the production method in Comparative Example 1, the conductive polymer layer forming step (S4) is performed only 7 times in total, and a good conductive polymer layer cannot be formed.

0070On the other hand, the solid electrolytic capacitors in Examples 1 to 7 are superior in capacitance, ESR characteristics, ESR characteristics after heat resistance test, and leakage current characteristics after heat resistance test as compared with the solid electrolytic capacitors in the conventional examples. From this, it can be seen that in the production methods of Examples 1 to 7, a good conductive polymer layer can be formed even if the conductive polymer layer forming step (S4) is performed only 7 times in total. I understand. This is because, as described above, the amount of the polymer solution retained is increased by the plurality of protrusions, and the internal impregnation property is improved.

0071(Average diameter of protrusion) Although the solid electrolytic capacitor in Comparative Example 2 has a plurality of protrusions (average diameter of 5 nm) formed, the capacitance, ESR characteristics, and heat resistance test of the solid electrolytic capacitor in Comparative Example 2 are higher than those in the conventional solid electrolytic capacitor. The ESR characteristics and the leakage current characteristics after the heat resistance test are almost unchanged. It is considered that this is because the average diameter of the protrusions is as small as 5 nm, and the protrusions have almost no effect on the adhesion between the dielectric oxide film and the conductive polymer layer and the internal impregnation property.

0072In Comparative Example 2, the average diameter of the protrusions is very small at 5 nm because the relative humidity during the heat treatment step (S3-4) is as high as 90%, so the thermal decomposition reaction of manganese dioxide due to the presence of water vapor. It is considered that this is because the manganese dioxide was dispersed and formed.

0073Further, the solid electrolytic capacitor in Comparative Example 4 also has a capacitance, ESR characteristics, and ESR characteristics as compared with the solid electrolytic capacitor in the conventional example, although a plurality of protrusions (average diameter of 160 nm) are formed. The ESR characteristics after the heat resistance test have hardly changed. The reason why the capacitance does not change is that the average diameter of the protrusions is as large as 160 nm, and the internal impregnation property does not improve even if the retention amount of the polymer solution increases due to the protrusions. It is considered that the reason why the ESR characteristics of the above do not change is that the average diameter of the protrusions is too large and the adhesion between the dielectric oxide film and the conductive polymer layer is not improved (or decreased).

0074On the other hand, the solid electrolytic capacitor (average diameter of protrusions is 10 nm) in Example 1 and the solid electrolytic capacitor (average diameter of protrusions is 102 nm) in Example 7 have ESR characteristics as compared with the solid electrolytic capacitor in the conventional example. , Capacitance, leakage current characteristics, ESR characteristics after heat resistance test, and leakage current characteristics after heat resistance test are excellent. From this, it can be seen that the average diameter of the protrusions is preferably 10 to 102 nm.

0075(Coverage of protrusions) The solid electrolytic capacitor in Comparative Example 3 (the coverage of the protrusion is 29%) is inferior in ESR characteristics and ESR characteristics after the heat resistance test as compared with the solid electrolytic capacitor in the conventional example. This is because the contact area between the dielectric oxide film and the conductive polymer layer has decreased, and the contact area between the dielectric oxide film and the plurality of protrusions made of manganese dioxide has increased. This is because the effect of deterioration of characteristics has increased.

0076On the other hand, the solid electrolytic capacitor in Example 2 (coverage of protrusions is 1%) and the solid electrolytic capacitor in Example 6 (coverage of protrusions is 20%) are compared with the solid electrolytic capacitor in the conventional example. Excellent ESR characteristics and ESR characteristics after heat resistance test. From this, it can be seen that the coverage of the protrusions is preferably 1 to 20%.

0077(Other) The solid electrolytic capacitor in Example 4 is superior in ESR characteristics, capacitance, leakage current characteristics, ESR characteristics after heat resistance test, and leakage current characteristics after heat resistance test as compared with the solid electrolytic capacitor in the conventional example. From this, it can be seen that the manganese nitrate aqueous solution containing no surfactant may be used in the dipping treatment step (S3-2).

0078Further, since the solid electrolytic capacitor in Example 3 has a slightly higher coverage of the protrusions than the solid electrolytic capacitor in Example 4, the immersion treatment step (S3-2) contains a surfactant. It can be seen that the coverage of the protrusions increases when an aqueous solution of manganese nitrate is used. This is because the surface tension is lowered by the surfactant and the internal impregnation property of the manganese nitrate aqueous solution is improved.

0079Further, since the solid electrolytic capacitor in Example 5 is superior in leakage current characteristics and leakage current characteristics after the heat resistance test as compared with the solid electrolytic capacitors in Examples 1 to 4, 6 and 7, the protrusion forming step. The leakage current characteristics and the leakage current characteristics after the heat resistance test are improved by performing a regeneration step of reforming the dielectric oxide film between (S3) and the conductive polymer layer forming step (S4). I understand. It is considered that this is because the defects of the dielectric oxide film and the like were repaired by the rechemical formation step.

0080Although the method for manufacturing the solid electrolytic capacitor and the preferable examples of the solid electrolytic capacitor according to the present invention have been described above, the present invention is not limited to each of the above examples.

0081For example, the manufacturing conditions such as the relative humidity shown in Table 1 and the number of protrusion forming steps (S3) can be arbitrarily changed. The relative humidity in the above embodiment is a parameter for increasing or decreasing the average diameter of the protrusions, and the number of protrusion forming steps (S3) is a parameter for increasing or decreasing the coverage of the protrusions. If protrusions made of manganese dioxide having an average diameter of 10 to 102 nm can be interspersed on the surface of the surface in an island shape so that the coverage is 1 to 20%, the same effect can be obtained under any manufacturing conditions. ..

0082Further, in each of the above examples, the chemical polymerization is performed in the conductive polymer layer forming step (S4), but a known method other than the chemical polymerization, for example, a conductive polymer solution or a conductive polymer is dispersed. The conductive polymer layer may be formed by a method of removing the solvent after immersing the solution in the above solution. However, since these methods have a larger molecular weight of the conductive polymer from the beginning than chemical polymerization, a plurality of protrusions formed on the surface of the dielectric oxide film at the time of forming the conductive polymer layer are the conductive polymer. The effect of the present invention in a state of being bitten into the layer can be maximized when chemical polymerization is carried out. Further, in each of the above examples, 3,4-ethylenedioxythiophene was used as the conductive polymer, but the present invention is not limited to this, and is generally known as a conductive polymer used for solid electrolytic capacitors. Any of the polythiophene, polypyrrole, polyaniline or derivatives thereof can be used.

0083Further, in each of the above examples, a tantalum sintered body was used as the material of the anode body, but a valve-acting metal sintered body such as niobium or aluminum or a roughened foil-shaped valve-acting metal may be used. .. In the case of a foil-shaped valve acting metal, for example, an aluminum foil having a thickness of 0.1 mm obtained by electrochemically etching the surface can be used.