Electrolytic capacitor and method for manufacturing same

Abstract

An electrolytic capacitor is provided with a capacitor element having a wound body formed by winding an etched anode foil and cathode foil with a separator holding a conductive polymer therebetween, and a pair of lead-out electrodes connected to the anode foil and the cathode foil, the pair of lead-out electrodes being electrically connected to the anode foil and the cathode foil, and the pair of lead-out electrodes being electrically connected to the anode foil and the cathode foil. The electrolytic capacitor is characterized in that the ratio of the weight of the conductive polymer and the liquid organic material in the capacitor element to the weight of the capacitor element excluding the lead portions of the pair of extraction electrodes is 2.0-20.1 wt%.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor and a method for manufacturing the same. Background Art

[0002] For example, Patent Document 1 describes an electrolytic capacitor, which is manufactured by roughening an anode foil by etching to form a dielectric layer, forming a conductive polymer film on the surface, and immersing the obtained winding body in an electrolyte having a dielectric layer repairing ability. This type of electrolytic capacitor is called a hybrid electrolytic capacitor, etc., which is small, has a large capacity, and has a low ESR (Equivalent Series Resistance), and is widely used as an electronic component for automotive parts, for example.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 090241 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] Numerous small holes called pits are formed on the surface of the anode foil by etching. A dielectric layer is formed on the inner wall of the pit, and minute defects of the dielectric layer can be repaired by the electrolyte filled in the pit.

[0008] However, in the manufacturing process of electrolytic capacitors, when the winding body is immersed in a dispersion or solution of a conductive polymer, if too much conductive polymer infiltrates into the separator of the winding body, a large amount of conductive polymer may aggregate and block the entrance of the pit after the winding body is dried. If the entrance of the pit is blocked, the pit will not be filled with electrolyte, so the electrostatic capacitance will decrease.

[0009] In addition, when there is no electrolyte filling in the pit, the ability to repair the tiny defects of the dielectric layer is reduced, resulting in an increase in tiny defects in the dielectric layer, which may cause leakage current and increase ESR. In this regard, by reducing the conductive polymer, the filling property of the electrolyte in the pit can be improved, but the reduction of the conductive polymer may cause an increase in ESR. In addition, by performing etching in a manner that expands the entrance of the pit, the filling property of the electrolyte in the pit can be improved, but the number of pits will decrease, so the electrostatic capacitance may decrease.

[0010] Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a low-ESR electrolytic capacitor capable of increasing electrostatic capacitance and a method for manufacturing the same.

[0011] Technical solutions to technical problems

[0012] The electrolytic capacitor of the present invention includes a capacitor element having a winding body and a pair of lead electrodes, wherein the winding body is formed by winding an anode foil and a cathode foil with a diaphragm holding a conductive polymer therebetween, and the pair of lead electrodes are connected to the anode foil and the cathode foil. The electrolytic capacitor is characterized in that the weight of the conductive polymer and the liquid organic matter in the capacitor element is 2.0 to 20.1 wt % relative to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes.

[0013] In the electrolytic capacitor, the ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes may be 9.1 wt % or less.

[0014] In the electrolytic capacitor, the ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes may be 8.6 wt % or less.

[0015] In the electrolytic capacitor, the ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes may be 2.9 wt % or more.

[0016] In the electrolytic capacitor, the ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes may be 3.2 wt % or more.

[0017] In the above electrolytic capacitor, the thickness of the separator may be 1 to 100 μm.

[0018] In the above electrolytic capacitor, the anode foil may have a thickness of 5 to 200 μm.

[0019] The manufacturing method of the electrolytic capacitor of the present invention is characterized in that it includes: a step of making a capacitor element, wherein the capacitor element has a winding body formed by winding an anode foil and a cathode foil with a separator therebetween and a pair of lead electrodes; a step of immersing the winding body in a dispersion or solution containing a conductive polymer and a liquid organic matter; and a step of drying the winding body, wherein the amount of the dispersion or the solution is adjusted in the step of immersing the winding body so that: after the step of drying the winding body, the weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is 2.0 to 20.1 wt%.

[0020] In the above-mentioned manufacturing method, the amount of the dispersion or the solution in the step of impregnating the winding body may be adjusted so that: after the step of drying the winding body, the ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is less than 9.1wt%.

[0021] In the above-mentioned manufacturing method, the amount of the dispersion or the solution in the step of impregnating the winding body may be adjusted so that: after the step of drying the winding body, the ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is less than 8.6wt%.

[0022] In the above-mentioned manufacturing method, the amount of the dispersion or the solution in the step of impregnating the winding body may be adjusted so that: after the step of drying the winding body, the weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is greater than 2.9wt%.

[0023] In the above-mentioned manufacturing method, the amount of the dispersion or the solution in the step of impregnating the winding body may be adjusted so that: after the step of drying the winding body, the ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is greater than 3.2wt%.

[0024] In the above production method, the concentration of the dispersion or the solution may be 0.1 to 5.0 wt %.

[0025] In the above manufacturing method, the separator may have a thickness of 1 to 100 μm.

[0026] In the above manufacturing method, the anode foil may have a thickness of 5 to 200 μm.

[0027] Effects of the Invention

[0028] According to the present invention, it is possible to increase the electrostatic capacitance while suppressing the ESR of the capacitor element. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a side view showing an example of an aluminum electrolytic capacitor.

[0030] Figure 2 This is a perspective view showing an example of a capacitor element.

[0031] Figure 3 It means along Figure 2A cross-sectional view of a portion of the cross section taken along line AA.

[0032] Figure 4 This is a cross-sectional view schematically showing a portion of the boundary between the etching layer and the diaphragm when the amount of the conductive polymer is appropriate.

[0033] Figure 5 This is a cross-sectional view schematically showing a portion of the boundary between the etching layer and the diaphragm when the conductive polymer is excessive.

[0034] Figure 6 It is a top view showing an example of extraction electrodes.

[0035] Figure 7 This is a flowchart showing an example of a manufacturing process of an aluminum electrolytic capacitor. DETAILED DESCRIPTION

[0036] [Implementation Method]

[0037] (Structure of aluminum electrolytic capacitor)

[0038] Figure 1 FIG. 1 is a side view showing an example of an aluminum electrolytic capacitor 1. Figure 1 , the internal cross section of the aluminum electrolytic capacitor 1 is shown in the right half of the center line L thereof.

[0039] The aluminum electrolytic capacitor 1 is an example of an electrolytic capacitor, and more specifically, a conductive polymer hybrid aluminum electrolytic capacitor. The aluminum electrolytic capacitor 1 can be mounted on an electronic circuit board and used for coupling, decoupling, smoothing, and the like.

[0040] The aluminum electrolytic capacitor 1 includes a capacitor element 10, a case 11, a sealing body 12, a seat plate 13, a pair of round rods 111, and a pair of lead parts 110. The round rods 111 and the lead parts 110 are lead electrodes of the capacitor element 10, and the lead parts 110 extend from the front ends of the round rods 111. Figure 1 Only one round bar portion 111 is shown in the figure, but another round bar portion 111 is provided at a symmetrical position with respect to the center line L.

[0041] Case 11 is made of aluminum and has a cylindrical shape with an upper opening closed. Case 11 covers capacitor element 10 and sealing body 12 and functions as an outer package of aluminum electrolytic capacitor 1. The shape of case 11 is not limited to a cylindrical shape, but may also be a square cylinder shape.

[0042] Sealing body 12 is a substantially circular member formed of an elastic member such as butyl rubber, etc. Sealing body 12 is adjacent to capacitor element 10 and closes the opening at the bottom of case 11 .

[0043] As described later, capacitor element 10 has a structure in which anode foil, cathode foil, and separator (electrolytic paper) are stacked and wound. A pair of round rod portions 111 extend from the bottom of capacitor element 10 .

[0044] The round rod portion 111 and the lead portion 110 are rod-shaped components formed of aluminum or the like. The pair of round rod portions 111 are respectively joined to the anode foil and the cathode foil by riveting or other joining methods, and function as the anode terminal and the cathode terminal of the aluminum electrolytic capacitor 1. Each round rod portion 111 is respectively inserted into a pair of through holes 120 formed in the sealing body 12. In addition, Figure 1 Only one through hole 120 is shown in the figure, but another through hole 120 is provided at a symmetrical position with respect to the center line L.

[0045] The lead portion 110 has a flat plate shape and is bent into an L shape, and a portion on the front end side thereof extends along the plate surface of the seat plate 13. A portion on one side of the round bar portion 111 of the lead portion 110 is inserted into the through hole 130 of the seat plate 13. The lead portion 110 can be soldered to a pad on the electronic circuit board during a reflow soldering step of the electronic circuit board.

[0046] The seat plate 13 is a plate-shaped member formed of resin or the like, and is disposed at the lower portion of the housing 11 and the sealing body 12. The seat plate 13 supports the housing 11 and the sealing body 12 relative to the electronic circuit board to be installed. The seat plate 13 is provided with a through hole 130 for the lead portion 110 and a groove 131 for accommodating the curved front end portion of the lead portion 110. The groove 131 extends from near the center to the outside along the bottom surface of the seat plate 13. The bottom surface of the seat plate 13 becomes the mounting surface for mounting the aluminum electrolytic capacitor 1 on the electronic circuit board, so that the plate-shaped lead portion 110 can be soldered to the pad on the electronic circuit board. In addition, a surface-mounted aluminum electrolytic capacitor 1 is cited in this embodiment, but the embodiments described later can also be applied to lead-type electrolytic capacitors without a seat plate 13.

[0047] (Structure of capacitor element)

[0048] Figure 2 1 is a perspective view showing an example of capacitor element 10. Figure 2 In, with Figure 1 The same components are denoted by the same reference numerals, and their description is omitted. Capacitor element 10 includes a wound body 100 including anode foil 101 , cathode foil 102 , and separator (electrolytic paper) 103 , and a pair of extraction electrodes 19 connected to anode foil 101 and cathode foil 102 .

[0049] A pair of extraction electrodes 19 extend downwardly from the wound body 100. The round rod portion 111 of each extraction electrode 19 is connected to the anode foil 101 and the cathode foil 102, respectively. Figure 2 2 shows a state of the lead portion 110 before being bent.

[0050] Anode foil 101 and cathode foil 102 are formed of valve metals such as aluminum, tantalum, titanium and niobium, and alloy foils thereof, as well as vapor-deposited foils, for example. Etching treatment is applied to the surface of anode foil 101 in such a manner as to increase the electrode area. As a result, capacitor element 10 can ensure a specified electrostatic capacitance. Furthermore, an extremely thin oxide film is formed on the surface of anode foil 101. Therefore, anode foil 101 is insulated from other components. The oxide film functions as a dielectric, and capacitor element 10 can function as a capacitor. The thickness of anode foil 101 is, for example, 5 to 200 (μm). By adopting this thickness range, an appropriate balance can be achieved between the strength of anode foil 101 and the amount of capacitance displayed, so it is preferred.

[0051] On the other hand, no oxide film is formed on the surface of cathode foil 102. Alternatively, etching may be performed on the surface of cathode foil 102. Alternatively, an oxide film may be formed on the surface of cathode foil 102, or an inorganic layer or a carbon layer may be formed.

[0052] The separator 103 is wound in a state of being sandwiched between the anode foil 101 and the cathode foil 102. The separator 103 is made of at least one material selected from cellulose, rayon, glass fiber, etc. The winding body 100 formed by winding the anode foil 101, the cathode foil 102 and the separator 103 is immersed in an electrolyte and a dispersion or solution of a conductive polymer in the manufacturing step of the aluminum electrolytic capacitor 1. The thickness of the separator 103 is, for example, 1 to 100 (μm). Using this thickness range, the strength, insulation, porosity and conductive material of the separator 103 can be well maintained, so it is preferred.

[0053] The electrolyte solution can contain polyols, sulfone compounds, lactone compounds, carbonate compounds, diether compounds of polyols, monohydric alcohols, etc. These may be used alone or in combination of two or more.

[0054] The polyol preferably contains at least one of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, polyalkylene glycol, and glycerol. As the polyalkylene glycol, polyethylene glycol having an average molecular weight of 200 to 1000 and polypropylene glycol having an average molecular weight of 200 to 5000 are preferably used.

[0055] As the lactone compound, γ-butyrolactone, γ-valerolactone, etc. can be used. As the carbonate compound, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, etc. can be included as solvents. Ethylene glycol, polyalkylene glycol, γ-butyrolactone, cyclopentane sulfone are particularly preferably used. The electrolyte may contain a solute. As the solute, an acid component, an alkali component, a salt composed of an acid component and an alkali component, a nitro compound, a phenolic compound, etc. can be used.

[0056] The acid component can use organic acids, inorganic acids, and composite compounds of organic acids and inorganic acids. As organic acids, carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, maleic acid, succinic acid, glutaric acid, adipic acid, benzoic acid, 4-hydroxybenzoic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, and azelaic acid can be used. As inorganic acids, boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, phosphoric acid esters, and phosphoric acid diesters can be used.

[0057] As the composite compound of an organic acid and an inorganic acid, disalicylic acid boric acid, dioxalyl boric acid, diethanol boric acid, and the like can be used.

[0058] As the base component, primary to tertiary amines, quaternary ammonium, quaternized amidinium, etc. can be used. As primary to tertiary amines, for example, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, N,N-diisopropylethylamine, tetramethylethylenediamine, hexylenediamine, aniline, etc. can be used. As quaternary ammonium, for example, tetramethylammonium, triethylmethylammonium, tetraethylammonium, etc. can be used. As quaternized amidinium, for example, ethyldimethylimidazolinium, tetramethylimidazolinium, etc. can be used.

[0059] The conductive polymer is not particularly limited as long as it is a polymer having conductivity. For example, as the conductive polymer, at least one polymer selected from polythiophene, polypyrrole, polyaniline and their derivatives is used. As the conductive polymer, polyethylene dioxythiophene (PEDOT) with at least one acid selected from p-toluenesulfonic acid and polystyrenesulfonic acid (PSS) as a dopant is generally used.

[0060] Figure 3 It means along Figure 2 A cross-sectional view of a portion of the cross section along the AA line of FIG. The separator 103 is sandwiched between the anode foil 101 and the cathode foil 102. The anode foil 101 has an etching layer 31 adjacent to the separator 103 on both sides and an aluminum layer 30 between each etching layer 31. In this example, the cathode foil 102 is thinner than the anode foil 101.

[0061] Separator 103 functions as a holding layer of the conductive polymer. As described below, the electrical characteristics of aluminum electrolytic capacitor 1 are affected by the amount of the conductive polymer in separator 103 .

[0062] Figure 4 This is a cross-sectional view schematically showing a portion of the boundary between the etching layer 31 and the diaphragm 103 when the amount of the conductive polymer is appropriate. Figure 4 The left side of the paper shows the state after the capacitor element 10 is immersed in the dispersion or solution of the conductive polymer and before it is immersed in the electrolyte in the manufacturing method of the aluminum electrolytic capacitor 1. On the other hand, Figure 4 The right side of the paper shows a state after capacitor element 10 is immersed in the electrolyte in the method for manufacturing aluminum electrolytic capacitor 1 .

[0063] A large number of pits 33 are formed by etching on the surface of the etching layer 31. In addition, a dielectric layer 32 as an oxide film is formed on the surface of the etching layer 31 including the inner wall of the pit 33. In the dielectric layer 32, as shown by the dotted circle, there are minute defects generated by the manufacturing process and the use after the manufacturing.

[0064] Furthermore, by immersing capacitor element 10 in a conductive polymer dispersion or solution, a large number of conductive polymer nanoparticles 4 are retained in separator 103. After capacitor element 10 is immersed in a conductive polymer dispersion or solution, capacitor element 10 is dried, whereby nanoparticles 4 aggregate to form conductive polymer layer 40.

[0065] Here, a part of the nanoparticles 4 enters the pit 33 and adheres to the etching layer 31 and the like in the pit 33 . In addition, another part of the nanoparticles 4 adheres near the entrance of the pit 33 .

[0066] When the capacitor element 10 is immersed in the electrolyte (see the shaded portion), the electrolyte is filled not only in the diaphragm 103 but also in the pits 33. When a voltage is applied to the aluminum electrolytic capacitor 1, the electrolyte can repair the minute defects of the dielectric layer 32. Specifically, the exposed aluminum of the minute defect portion contacts the electrolyte, and when a voltage is applied, the chemical conversion is promoted, and the oxide film is re-formed.

[0067] Figure 5 This is a cross-sectional view schematically showing a portion of the boundary between the etching layer 31 and the diaphragm 103 when the conductive polymer is excessive. Figure 5 The left side of the paper shows the state of the capacitor element 10 after being immersed in the dispersion or solution of the conductive polymer and before being immersed in the electrolyte in the manufacturing process of the aluminum electrolytic capacitor 1. On the other hand, Figure 5 The right side of the paper shows the state after the capacitor element 10 is immersed in the electrolyte in the manufacturing step of the aluminum electrolytic capacitor 1. Figure 5 In, with Figure 4 The same reference numerals are used to designate common structures, and description thereof will be omitted.

[0068] In this example, capacitor element 10 is immersed in Figure 4 Therefore, the number of the conductive polymer nanoparticles 4 in the diaphragm 103 increases, and the density thereof increases, so that the conductive polymer layer 40 becomes thicker, and the entrances of some of the pits 33 are blocked by the adhesion of the nanoparticles 4. Therefore, even if the capacitor element 10 is immersed in the electrolyte, the electrolyte has difficulty passing through the conductive polymer layer 40, and pits 33 that are not filled with the electrolyte are generated.

[0069] Since there is no electrolyte in the pit 33, the dielectric layer 32 is not electrically connected to the cathode foil 102, and thus the electrostatic capacitance of the aluminum electrolytic capacitor 1 is reduced. In addition, since no oxide film is formed at the micro defect portion of the dielectric layer 32, leakage current (LC) is generated, and the LC of the aluminum electrolytic capacitor 1 may increase. In addition, by performing etching in a manner that enlarges the entrance of the pit, the filling property of the electrolyte in the pit 33 can be improved, but the number of the pits 33 is reduced, and thus the electrostatic capacitance may be reduced.

[0070] For this purpose, the aluminum electrolytic capacitor 1 is manufactured in such a manner that the weight ratio of the conductive polymer and the liquid organic matter in the capacitor element 10 to the weight of the capacitor element 10 excluding the lead portion 110 (hereinafter referred to as the polymer weight ratio) is 2.0 to 20.1 (wt%). Here, the liquid organic matter is a high boiling point solvent contained in a dispersion or solution of the conductive polymer, and is a high boiling point solvent remaining in the diaphragm 103 after the capacitor element is immersed in the dispersion or solution of the conductive polymer and dried in the manufacturing step of the aluminum electrolytic capacitor 1. Examples of the high boiling point solvent include diethylene glycol, triethylene glycol, polyethylene glycol, polyethylene glycol monoalkyl ether, polyethylene glycol dialkyl ether, etc., which are solvents having a boiling point of 220° C. or above, but are not limited thereto. Among them, the dispersion or solution of the conductive polymer sometimes contains water, but the water evaporates by drying after the immersion.

[0071] The polymer weight ratio is preferably 9.1 (wt%) or less, and more preferably 8.6 (wt%) or less. By adopting this range, the wetting efficiency of the electrolyte after the conductive polymer is infiltrated can be improved. In addition, the polymer weight ratio is preferably 2.9 (wt%) or more, and more preferably 3.2 (wt%) or more. By adopting this range, the low ESR in the aluminum electrolytic capacitor 1 brought about by forming the conductive polymer layer can be maintained.

[0072] The reason why the polymer weight ratio is defined by the weight of capacitor element 10 excluding lead portion 110 is as follows.

[0073] Figure 61 is a plan view showing an example of the extraction electrode 19. The extraction electrode 19 includes a flat portion 112, a round rod portion 111, and a lead portion 110.

[0074] The flat portion 112 is a flat plate-shaped portion provided at one end of the round rod portion 111 on the opposite side of the lead portion 110, and is formed, for example, by pressing one end of the round rod portion 111. The flat portion 112 is a portion connected to the anode foil 101 and the cathode foil 102 by riveting, and is located inside the wound body 100, so it is not exposed to the outside.

[0075] The weight of the capacitor element 10 is defined as a value in a state where the lead portion 110 is cut off from the end of the round rod portion 111 along the cutting line C. The length of the lead portion 110 is determined according to the type of product, etc. Therefore, by cutting the lead portion 110 off from the capacitor element 10, the influence of the length of the lead portion 110 on the weight of the capacitor element 10 can be excluded from the calculation of the polymer weight ratio.

[0076] (Electrolytic Capacitor Manufacturing Steps)

[0077] Figure 7 This is a flowchart showing an example of the manufacturing steps of the aluminum electrolytic capacitor 1. When manufacturing the aluminum electrolytic capacitor 1, the anode foil 101, the cathode foil 102, and the diaphragm 103 are prepared. For example, the thickness of the anode foil 101 is 5 to 200 (μm), and the thickness of the diaphragm is 1 to 100 (μm). Pits 33 are formed on each surface of the anode foil 101 and the cathode foil 102 by etching. The anode foil 101 is subjected to a chemical conversion treatment, and a dielectric layer 32 with an oxide film is formed on the etched surface. In addition, a pair of lead electrodes 19 are connected to the anode foil 101 and the cathode foil 102, respectively. As a connection method for the lead electrodes 19, riveting can be cited as an example, but it is not limited to this.

[0078] First, the anode foil 101, the separator 103, the cathode foil 102, and the separator 103 are stacked and wound in sequence, and the outer surface is fixed with a winding fixing tape, thereby forming a winding body 100 (step St1). Step St1 is an example of a step of forming the capacitor element 10. Next, the winding body 100 is immersed in, for example, an ammonium phosphate aqueous solution, and a rechemical conversion treatment is performed while applying a predetermined voltage to the anode foil 101, the oxide film is repaired, and a dielectric layer 32 is formed on the surface of the cut of the anode foil 101 (step St2).

[0079] Next, under a reduced pressure atmosphere, the wound body 100 is immersed in a dispersion of a conductive polymer, so that the dispersion soaks the wound body 100 (step St3). Alternatively, the wound body 100 may be immersed in a solution containing a conductive polymer instead of the dispersion of the conductive polymer. Next, the wound body 100 is dried (step St4). At this time, in the capacitor element 10, the liquid organic matter contained in the dispersion or solution is retained as a residue.

[0080] In the step St4, the amount of the conductive polymer dispersion or solution is adjusted in advance so that the polymer weight ratio measured after the end of this step is 2.0 to 20.1 (wt%). Therefore, it is possible to increase the electrostatic capacitance while suppressing the increase in the ESR of the aluminum electrolytic capacitor 1. Here, the polymer weight ratio is preferably 9.1 (wt%) or less, and more preferably 8.6 (wt%) or less. Furthermore, the polymer weight ratio is preferably 2.9 (wt%) or more, and more preferably 3.2 (wt%) or more. In addition, the concentration of the conductive polymer dispersion or solution is 0.1 to 5.0 (wt%).

[0081] Next, the capacitor element 10 is infiltrated with the electrolyte under a reduced pressure atmosphere (step St5). Next, the capacitor element 10 is housed in the housing 11 and sealed by the sealing body 12 (step St6). At this time, the lead electrode 19 extending from the capacitor element 10 is inserted into the through hole 120 of the sealing body 12. After that, the aluminum electrolytic capacitor 1 can be aged while applying the rated voltage. In this way, the manufacturing steps of the aluminum electrolytic capacitor 1 are performed.

[0082] Example

[0083] Samples No. 1 to 38 of aluminum electrolytic capacitors 1 were made according to the above-mentioned manufacturing method. Samples No. 1 to 19 are aluminum electrolytic capacitors 1 with a rated voltage and a rated electrostatic capacity of 25V and 470μF, respectively, and samples No. 20 to 38 are aluminum electrolytic capacitors 1 with a rated voltage and a rated electrostatic capacity of 63V and 56μF, respectively. The dimensions of the shells of samples No. 1 to 38 are diameter 10 (mm) × length 10 (mm). In addition, the voltage applied in the rechemical conversion treatment of the capacitor element 10 is 56 (V) in the case of samples No. 1 to 19 and 143 (V) in the case of samples No. 20 to 38.

[0084] When capacitor element 10 is immersed in the conductive polymer dispersion, the amount of the dispersion is adjusted so that the polymer weight ratio is 1.7 to 21.5 (wt%). The polymer weight ratio varies among samples No. 1 to No. 38. In addition, capacitor element 10 is impregnated with a predetermined amount of electrolyte in a reduced pressure atmosphere.

[0085] (evaluate)

[0086] The capacitance and ESR of each of Sample No. 1 to 38 of the aluminum electrolytic capacitor 1 were measured. The capacitance (initial capacitance) (μF) of the electrolytic capacitor at a frequency of 120 Hz and the ESR (initial ESR) (mΩ) of the electrolytic capacitor at a frequency of 100 kHz were measured using a four-terminal LCR tester.

[0087] [Table 1]

[0088]

[0089] Table 1 shows the evaluation results of samples No. 1 to 15 of the aluminum electrolytic capacitor 1 with a rated voltage and a rated electrostatic capacitance of 25V and 470μF, respectively. Table 1 shows the polymer weight ratio (wt%), electrostatic capacitance (μF), ESR (Ω) and judgment results of samples No. 1 to 15. The polymer weight ratio is calculated using the weight of the conductive polymer and organic matter in the capacitor element 10 except for the lead portion 110 of a pair of lead electrodes 19. In addition, regarding the judgment criteria, for example, samples with an electrostatic capacitance of 430 (μF) or more and an ESR of 0.020 (Ω) or less are defined as OK, and samples that do not meet these conditions are defined as NG. These reference values ​​are determined by prescribed standards.

[0090] The polymer weight ratio of sample No. 19 is greater than that of other samples No. 2 to 18. Therefore, it is expected that the amount of conductive polymer retained in the separator is too large, as shown in FIG. Figure 5 As described above, many of the pits 33 were blocked by the conductive polymer nanoparticles 4, so that the electrolyte could not be fully filled in the pits 33, and the electrostatic capacity was lower than that of other samples No. 2 to 18. Therefore, the judgment result of sample No. 19 was NG.

[0091] In addition, the polymer weight ratio of sample No. 1 is smaller than that of other samples No. 2 to 19. Therefore, the amount of conductive polymer retained in the separator is small, so the number of pits 33 whose entrances are blocked by the conductive polymer nanoparticles 4 is small, and a sufficient amount of electrolyte is filled in the pits 33, thereby ensuring sufficient electrostatic capacitance. However, since the amount of conductive polymer is too small, the ESR increases. Therefore, the judgment result of sample No. 1 is NG.

[0092] In addition, the polymer weight ratio of samples No. 2 to 18 is 2.0 to 20.1 (wt%), which is greater than the polymer weight ratio of 1.8 (wt%) of sample No. 1, and less than the polymer weight ratio of 21.5 (wt%) of sample No. 19. Therefore, compared with sample No. 19, since the conductive polymer retained in the diaphragm is reduced, the conductive polymer layer 40 has an appropriate thickness. As a result, there are fewer pits 33 whose entrances are blocked by the conductive polymer nanoparticles 4, and the pits 33 are filled with a sufficient amount of electrolyte, thereby ensuring sufficient electrostatic capacitance. On the other hand, the amount of conductive polymer is larger than that of sample No. 1, so low ESR can be achieved. Therefore, the judgment results of samples No. 2 to 18 are OK.

[0093] [Table 2]

[0094]

[0095] Table 2 shows the evaluation results of samples No. 20 to 38 of the aluminum electrolytic capacitor 1 with a rated voltage and a rated electrostatic capacitance of 63V and 56μF, respectively. Table 2 shows the polymer weight ratio (wt%), electrostatic capacitance (μF), ESR (Ω) and judgment results of samples No. 20 to 38. The polymer weight ratio is calculated using the weight of the conductive polymer and organic matter in the capacitor element 10 except for the lead portion 110 of a pair of lead electrodes 19. In addition, regarding the judgment criteria, for example, samples with an electrostatic capacitance of 50 (μF) or more and an ESR of 0.02 (Ω) or less are defined as OK, and samples that do not meet these conditions are defined as NG. These reference values ​​are determined by prescribed standards.

[0096] The polymer weight ratio of sample No. 38 is greater than that of other samples No. 20 to 37. Therefore, it is expected that the amount of conductive polymer retained in the separator is too much, as shown in the reference Figure 5 As described above, many of the pits 33 were blocked by the conductive polymer nanoparticles 4, so that the electrolyte could not be fully filled in the pits 33, and the electrostatic capacity was lower than that of other samples No. 20 to 37. Therefore, the judgment result of sample No. 38 was NG.

[0097] In addition, the polymer weight ratio of sample No. 20 is smaller than that of other samples No. 21 to 38. Therefore, the amount of conductive polymer retained in the separator is small, so the number of pits 33 whose entrances are blocked by the conductive polymer nanoparticles 4 is small, and a sufficient amount of electrolyte is filled in the pits 33, thereby ensuring sufficient electrostatic capacitance. However, since the amount of conductive polymer is too small, the ESR increases. Therefore, the judgment result of sample No. 20 is NG.

[0098] In addition, the polymer weight ratio of samples No. 21 to 37 is 2.1 to 19.9 (wt%), which is greater than the polymer weight ratio of 1.7 (wt%) of sample No. 20, and less than the polymer weight ratio of 20.7 (wt%) of sample No. 38. Therefore, compared with sample No. 38, since the conductive polymer retained in the diaphragm is reduced, the conductive polymer layer 40 has an appropriate thickness. As a result, there are fewer pits 33 whose entrances are blocked by the conductive polymer nanoparticles 4, and the pits 33 are filled with a sufficient amount of electrolyte, thereby ensuring sufficient electrostatic capacitance. On the other hand, the amount of conductive polymer is larger than that of sample No. 20, so low ESR can be achieved. Therefore, the judgment results of samples No. 21 to 37 are OK.

[0099] Thus, according to the embodiment, by making the polymer weight ratio relative to the weight of the capacitor element 10 other than the lead portion 110 of the pair of lead electrodes 19 2.0 to 20.1 (wt%), it is possible to increase the electrostatic capacitance while suppressing the increase in the ESR of the aluminum electrolytic capacitor 1. In order to further reduce the ESR, the polymer weight ratio is preferably 9.1 (wt%) or less, and more preferably 8.6 (wt%) or less. In addition, the polymer weight ratio is preferably 2.9 (wt%) or more, and more preferably 3.2 (wt%) or less. In addition, a dispersion of a conductive polymer is used in this embodiment, but the same result as above can be obtained when a solution of a conductive polymer is used.

[0100] (Calculation method of polymer weight ratio)

[0101] Next, the method for calculating the polymer weight ratio is described. Remove the case from the aluminum electrolytic capacitor 1 and take out the capacitor element 10. Cut the lead portion 110 of the pair of lead electrodes 19 of the capacitor element 10 from the base of the round rod portion 111 using pliers or the like. Figure 7 The cutting line C is shown.

[0102] The capacitor element 10 was immersed in distilled water at 40°C for 1 hour. In this way, the electrolyte in the capacitor element 10 was extracted into the distilled water to remove the electrolyte. The capacitor element 10 from which the electrolyte was removed was dried at 100°C for 1 hour to evaporate the distilled water, and the weight of the entire capacitor element 10 at this time was measured.

[0103] The dried capacitor element 10 is decomposed into the anode foil 101, the cathode foil 102, the two diaphragms 103, the lead electrodes 19 of the anode and cathode after the lead part 110 is cut off, and the respective parts of the element fixing tape (not shown). The anode foil 101, the cathode foil 102, the two diaphragms 103, the lead electrodes 19 of the anode and cathode, and the element fixing tape are thermally analyzed in an oxygen atmosphere using a thermal analysis device (Tg-DTA: Thermogravimetry Differential Thermal Analysis). At this time, the conductive polymer is thermally decomposed into gases such as SO2 at a specific temperature, and the weight is reduced, so the weight of the conductive polymer contained in the capacitor element 10 can be measured.

[0104] In addition, since the high boiling point solvent of the conductive polymer dispersion also evaporates at a specific temperature and produces a weight loss, the weight of the high boiling point solvent contained in the capacitor element 10 can also be measured. The total weight reduction of the conductive polymer and the high boiling point solvent in each part of the capacitor element 10 obtained in this way is the weight of the conductive polymer dispersion. The ratio of the weight of the conductive polymer dispersion to the overall weight of the capacitor element 10 after the electrolyte cleaning and drying is calculated and used as the polymer weight ratio.

[0105] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. An electrolytic capacitor comprising a capacitor element having a winding body and a pair of lead electrodes, wherein: The winding body is formed by winding an anode foil and a cathode foil through a separator holding a conductive polymer, the pair of lead electrodes are connected to the anode foil and the cathode foil, and the electrolytic capacitor is characterized in that: The weight ratio of the conductive polymer and the liquid organic matter in the capacitor element to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is 2.0 to 20.1 wt %.

2. The electrolytic capacitor according to claim 1, characterized in that: The ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is 9.1 wt % or less.

3. The electrolytic capacitor according to claim 1, characterized in that: The ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is 8.6 wt % or less.

4. The electrolytic capacitor according to claim 1, characterized in that: The ratio of the weight of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is 2.9 wt % or more.

5. The electrolytic capacitor according to claim 1, characterized in that: The weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is 3.2 wt % or more.

6. The electrolytic capacitor according to any one of claims 1 to 5, characterized in that: The thickness of the separator is 1 to 100 μm.

7. The electrolytic capacitor according to any one of claims 1 to 5, characterized in that: The thickness of the anode foil is 5-200 μm.

8. A method for manufacturing an electrolytic capacitor, characterized in that: include: The step of manufacturing a capacitor element, wherein the capacitor element comprises a winding body formed by winding an anode foil and a cathode foil with a separator interposed therebetween, and a pair of lead electrodes; A step of immersing the wound body in a dispersion or solution containing a conductive polymer and a liquid organic substance; and The step of drying the wound body, In which, in the step of impregnating the wound body, the amount of the dispersion or the solution is adjusted so that: after the step of drying the wound body, the weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is 2.0 to 20.1 wt%.

9. The method for manufacturing an electrolytic capacitor according to claim 8, wherein: The amount of the dispersion or the solution in the step of impregnating the wound body is adjusted so that: after the step of drying the wound body, the weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is less than 9.1wt%.

10. The method for manufacturing an electrolytic capacitor according to claim 8, wherein: The amount of the dispersion or the solution in the step of impregnating the wound body is adjusted so that: after the step of drying the wound body, the weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is less than 8.6wt%.

11. The method for manufacturing an electrolytic capacitor according to claim 8, wherein: The amount of the dispersion or the solution in the step of impregnating the wound body is adjusted so that: after the step of drying the wound body, the weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is greater than 2.9wt%.

12. The method for manufacturing an electrolytic capacitor according to claim 8, wherein: The amount of the dispersion or the solution in the step of impregnating the wound body is adjusted so that: after the step of drying the wound body, the weight ratio of the conductive polymer and the liquid organic matter to the weight of the capacitor element excluding the lead portion of the pair of lead electrodes is greater than 3.2wt%.

13. The method for manufacturing an electrolytic capacitor according to any one of claims 8 to 12, characterized in that: The concentration of the dispersion or the solution is 0.1 to 5.0 wt %.

14. The method for manufacturing an electrolytic capacitor according to any one of claims 8 to 12, characterized in that: The thickness of the separator is 1 to 100 μm.

15. The method for manufacturing an electrolytic capacitor according to any one of claims 8 to 12, characterized in that: The thickness of the anode foil is 5-200 μm.

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