JP2009289833A - Method for manufacturingcapacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing of a solid electrolytic capacitor can suppress deterioration of an oxide coating of anode foil while using a conductive polymer dispersion element solution. <P>SOLUTION: This method for manufacturing of a solid electrolytic capacitor includes: an arrangement process of arranging a separator (30) between the anode foil (10) formed of aluminum with a chemical conversion treatment applied to a surface thereof, and cathode foil (20) with carbide particles held to a surface thereof; and a formation process of forming solid electrolyte layers between the anode foil (10) and the separator (30) and between the cathode foil (20) and the separator (30) by impregnating and drying the conductive polymer dispersion element solution (60) of pH5-pH8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  A solid electrolytic capacitor using a conductive polymer for a cathode layer has a drawback that a high voltage product, particularly a rated voltage product of 16 V or more, has a large leakage current. In order to solve this defect, a technique for improving pressure resistance and heat resistance by adding glycerin or sulfolane to a monomer and an oxidizing agent for forming a conductive polymer has been disclosed (for example, see Patent Document 1).

JP 2004-128092 A

  However, in a solid electrolytic capacitor in which an oxide film is formed on an anode foil made of aluminum, the leakage current may increase due to the deterioration of the oxide film due to the acidic effect caused by the oxidizing agent.

  Therefore, it is conceivable to form a solid electrolyte layer by impregnating a separator with a solution in which a conductive polymer having a small particle size is dispersed without using an oxidizing agent. For example, it is conceivable to use a conductive polymer dispersion solution manufactured by Starck. However, when a conductive polymer dispersion solution manufactured by Starck Co. is used, the oxide film may be deteriorated.

  The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a solid electrolytic capacitor capable of suppressing deterioration of an oxide film of an anode foil while using a conductive polymer dispersion solution. And

  A method for producing a solid electrolytic capacitor according to the present invention includes a disposing step of disposing a separator between an anode foil made of aluminum and subjected to chemical conversion treatment on the surface, and a cathode foil holding carbide particles on the surface; And a step of forming a solid electrolyte layer by impregnating a conductive polymer dispersion solution having a pH of 5 to 8 and drying between the separator foil and the cathode foil and the separator. Is. In the method for producing a solid electrolytic capacitor according to the present invention, since a conductive polymer dispersion solution having a pH of 5 to 8 is used, deterioration of the aluminum oxide film on the anode foil can be suppressed.

  The said manufacturing method may further include the adjustment process which adjusts pH of a conductive polymer dispersion solution to 5-8 by adding a pH adjuster to a conductive polymer dispersion solution.

  The conductive polymer dispersion may contain at least one of polythiophene and polystyrene.

  The separator may be made of fibers mainly composed of cellulose. The OH group contained in cellulose has water repellency with respect to an acidic solution containing a conductive polymer. Thereby, when a separator contains a cellulose, the impregnation to the separator of the electroconductive polymer dispersion solution which has acidity is suppressed. Therefore, when the separator contains cellulose, a solid electrolyte layer can be efficiently formed by using a conductive polymer dispersion solution having a pH of 5 to 8.

  The arranging step may be a step of winding the anode foil and the cathode foil through the separator. The pH of the conductive polymer dispersion solution may be 6.1 to 6.9.

  According to the present invention, deterioration of the oxide film of the anode foil can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described.

(Embodiment)
1-4 is a figure for demonstrating the manufacturing method of the solid electrolytic capacitor which concerns on one embodiment of this invention. First, as shown in FIG. 1A, an anode foil 10 and a cathode foil 20 are prepared. The anode foil 10 is made of a valve metal having a dielectric oxide film (not shown) formed on the surface thereof. Examples of the valve metal used for the anode foil 10 include metals such as aluminum, tantalum, niobium, and titanium. In the present embodiment, aluminum is used as anode foil 10. The dielectric oxide film can be formed by performing etching treatment and chemical oxidation treatment on the surface of the valve metal. In the present embodiment, the dielectric oxide film is an aluminum oxide film. The cathode foil 20 is made of a metal foil such as aluminum having carbide particles (not shown) held on the surface. The anode foil 10 and the cathode foil 20 have substantially the same dimensions.

  Next, as shown in FIG. 1B, the anode terminal 11 is joined to the anode foil 10, and the cathode terminal 21 is joined to the cathode foil 20. Next, as shown in FIG. 1C, the anode foil 10 and the cathode foil 20 are wound through the separator 30. Thereby, the winding element 100 is completed. The separator 30 is made of natural fibers (cellulose) and / or chemical fibers. Natural fibers (cellulose) and / or chemical fibers that can be used for the separator 30 are not particularly limited. As the chemical fiber, for example, a synthetic fiber such as a polyamide fiber, an acrylic fiber, a vinylon fiber, a polyimide fiber, an aramid fiber, or a nylon fiber can be used.

  Next, as shown in FIG. 1D, the anode terminal 11 and the cathode terminal 21 are inserted into the through holes of the sealing member 40. The sealing member 40 is made of an elastic member such as rubber. A plurality of winding elements 100 are created by repeating the steps of FIGS. Next, as shown in FIG. 2A, the anode terminal 11 or the cathode terminal 21 of each winding element 100 is fixed to the bar 50.

  Next, as shown in FIG. 2B, each winding element 100 is immersed in a chemical conversion liquid in a chemical conversion liquid container, and the anode foil 10 is subjected to chemical conversion treatment using the chemical conversion liquid container as a cathode. The solute used in the chemical conversion liquid is a solute such as an organic acid salt having a carboxylic acid group or an inorganic acid salt such as phosphoric acid. In the present embodiment, ammonium adipate is used as the chemical conversion liquid. This chemical conversion treatment is performed at a voltage (for example, 80 V) approximate to the chemical conversion voltage value of the dielectric oxide film using a chemical conversion liquid mainly composed of ammonium adipate concentration of 0.5 wt% to 3 wt%.

  Next, the winding element 100 is taken out from the chemical conversion solution, and each winding element 100 is subjected to heat treatment as shown in FIG. The heat treatment is performed at a temperature range of 200 ° C. to 300 ° C. for about several minutes to several tens of minutes. Thereafter, the steps of FIG. 2B and FIG. 2C are further performed several times. Thereby, a stronger dielectric oxide film can be formed. By this chemical conversion treatment, an oxide film is formed on the exposed metal surface due to the valve metal exposed on the end surface (edge portion) of the anode foil 10 or the damage due to the terminal connection.

  Next, as shown in FIG. 3A, each winding element 100 is immersed in the conductive polymer dispersion solution 60. Accordingly, the separator 30 can be impregnated with the conductive polymer dispersion solution 60. The conductive polymer dispersion solution 60 is a solution in which conductive polymer particles are dispersed in water. The particle size of the conductive polymer is, for example, at the nano level. As the conductive polymer, polythiophene, polystyrene, polypyrrole, polyaniline, polyfuran, or the like can be used. The concentration of the conductive polymer in the conductive polymer dispersion solution 60 is about 0.1 wt% to 5 wt%. The pH of the conductive polymer dispersion solution 60 is 5-8. The conductive polymer exhibits acidity when dispersed in water. Therefore, the pH of the conductive polymer dispersion solution 60 can be adjusted to 5 to 8 using a pH adjuster. As the pH adjuster, for example, amine compounds such as trimethylamine and tetramethylamine can be used.

  Next, as shown in FIG. 3B, each winding element 100 is accommodated in a drying furnace, and the conductive polymer dispersion solution 60 impregnated in the separator 30 is dried. Thereafter, the steps of FIGS. 3A and 3B are repeated several times. Thereby, as shown in FIG. 3C, a solid electrolyte layer 70 made of the conductive polymer can be formed between the anode foil 10 and the separator 30 and between the cathode foil 20 and the separator 30. . Thereby, the capacitor element 200 is completed.

  In addition, it is preferable that the immersion speed and pulling-up speed at the time of impregnating the separator 30 with the conductive polymer dispersion solution 60 are about 0.1 mm / sec to 1 mm / sec. This is because if the immersion speed and the pulling speed are large, the conductive polymer dispersion solution 60 cannot be sufficiently penetrated into the etching pits, and even if the soaking speed and the pulling speed are reduced, the influence on the permeability is small. .

  The impregnation time of the conductive polymer dispersion solution 60 is preferably about 10 min to 20 min. This is because if the impregnation time is short, the conductive polymer dispersion solution 60 is not sufficiently impregnated, and even if the impregnation time is long, the influence on the impregnation property is small. Moreover, it is preferable that the temperature at the time of drying of FIG.3 (b) is about 85 to 125 degreeC.

  Next, as shown in FIG. 4A, the capacitor element 200 is housed in the metal case 80. Next, the sealing member 40 is pushed into the opening of the metal case 80. Next, as shown in FIG. 4B, the opening of the metal case 80 is crimped. Subsequently, an aging process for applying a rated voltage to the capacitor element 200 under a temperature condition of about 150 ° C. is performed to insulate the defective portions of the anode foil 10 and the cathode foil 20, thereby completing the solid electrolytic capacitor 300.

  FIG. 5A is an external view of the solid electrolytic capacitor 300 after the aging process. FIG. 5B is a partially cutaway sectional view of the solid electrolytic capacitor 300. The seat plate 90 is brought into close contact with the sealing member 40 side of the solid electrolytic capacitor 300, the seat plate 90 is passed through the anode terminal 11 and the cathode terminal 21, and the anode terminal 11 and the cathode terminal 21 are routed from the root of the through hole of the seat plate 90. By bending 90 degrees, the surface mount type solid electrolytic capacitor 300a shown in FIG. 5C is completed.

  Here, when an acidic conductive polymer dispersion solution is used, the aluminum oxide film covering the surface of the anode foil 10 may be deteriorated. On the other hand, when an alkaline conductive polymer dispersion solution is used, the conductive polymer dispersion aggregates and the viscosity of the conductive polymer dispersion solution increases. As a result, it becomes difficult to impregnate the separator 30 with the conductive polymer. Since the conductive polymer dispersion solution 60 having a pH of 5 to 8 is used in the present embodiment, the deterioration of the aluminum oxide film in the anode foil 10 can be suppressed, and the conductive polymer dispersion Aggregation can be suppressed.

  Moreover, the OH group contained in cellulose has water repellency with respect to the conductive polymer dispersion solution having acidity. Thereby, when the separator 30 contains a cellulose, the impregnation to the separator 30 of the electroconductive polymer dispersion solution having an acidity of about pH 2 to pH 3, for example, is suppressed. Therefore, when separator 30 contains cellulose, solid electrolyte layer 70 can be efficiently formed by using conductive polymer dispersion solution 60 according to the present embodiment. In particular, the solid electrolyte layer 70 can be efficiently formed with respect to the separator 30 mainly composed of cellulose (the mixing ratio of cellulose is 50 wt% or more). In addition, since cellulose is cheaper than synthetic fiber, if a separator mainly composed of cellulose can be used, manufacturing cost can be reduced.

  The conductive polymer dispersion solution 60 can also be applied to a stacked solid electrolytic capacitor. FIG. 6 is a schematic cross-sectional view of a multilayer solid electrolytic capacitor 300b. As shown in FIG. 6, the solid electrolytic capacitor 300b has a structure in which a plurality of unit elements 301 are laminated on a substrate 302 via a conductive adhesive 303 made of silver paste or the like.

  The unit element 301 has a structure in which a solid electrolyte layer 305, a carbon paste layer 306, and a cathode layer 307 are sequentially formed on the entire surface of the anode foil 304. A material similar to that of the anode foil 10 can be used for the anode foil 304. For the solid electrolyte layer 305, the same material as that of the solid electrolyte layer 70 can be used. A material similar to that of the cathode foil 20 can be used for the cathode layer 307.

  When forming the solid electrolyte layer 305 of the multilayer solid electrolytic capacitor 300b having such a structure, the aluminum oxide film of the anode foil 304 is deteriorated by using a conductive polymer dispersion solution of pH 5 to pH 8. Can be suppressed.

  Hereinafter, the solid electrolytic capacitor 300 according to the above embodiment was manufactured and the characteristics thereof were examined.

(Example 1)
In Example 1, the solid electrolytic capacitor 300 of FIG. 4B was produced. First, as the anode foil 10, an aluminum chemical conversion foil subjected to etching treatment and chemical conversion treatment was used. As the cathode foil 20, an aluminum foil having the same width as that of the anode foil 10 and having carbide particles held on the surface thereof was used. The anode foil 10 and the cathode foil 20 were wound through a separator 30 to produce a winding element 100. As the separator 30, a fiber mainly composed of cellulose was used.

  Thereafter, the winding element 100 was immersed in the chemical conversion liquid, and a voltage (80 V) in the vicinity of the chemical conversion voltage of the dielectric coating of the anode foil 10 was applied to the anode foil 10. As a chemical conversion liquid in this case, a solution containing 2.0 wt% of adipic acid ammonium salt was used. Thereafter, the chemical conversion liquid was removed from the winding element 100 in pure water, and then heat treatment was performed at 270 ° C. for 10 minutes.

  Thereafter, the wound element 100 was immersed in the conductive polymer dispersion solution 5 for 5 minutes, pulled up, and then heated to 105 ° C. to dry the conductive polymer dispersion solution 60. This operation was repeated three times to form the solid electrolyte layer 70, and the capacitor element 200 was completed. As the conductive polymer dispersion solution 60, one having a pH of 6.5 containing a mixed dispersion of polyethylene dioxythiophene and polystyrene sulfonic acid was used. The dipping speed and the pulling speed were 0.3 mm / sec. In addition, since pH can change about +/- 0.4 with a slight environmental change, pH 6.5 +/- 0.4 is considered equivalent to pH 6.5.

  Thereafter, the capacitor element 200 is housed in a metal case 80 made of aluminum, the opening of the metal case 80 is crimped by a sealing member 40 made of rubber, and an aging process is performed in which a rated voltage is applied under a temperature condition of 125 ° C. . In addition, the capacity | capacitance of the solid electrolytic capacitor 300 which concerns on Example 1 is 25V47 micro F, and a dimension is (phi) 8 mm x 11.5 mmL.

(Comparative Example 1)
In Comparative Example 1, a solid electrolytic capacitor was produced by the same method as in the example. However, the solid electrolyte layer was formed by the following method. First, the separator was immersed in a monomer solution in which a monomer stock solution of 3,4 ethylenedioxythiophene was diluted with a dilute solvent made of ethanol for 1 minute. The concentration of the monomer solution was 25 wt%. Next, ethanol was removed by drying under a temperature condition of 50 ° C. Next, the wound element was immersed in a 55 wt% butanol solution of p-toluenesulfonic acid iron salt and impregnated under reduced pressure. Next, the winding element was heated stepwise from 30 ° C. to 180 ° C. to form a solid electrolyte layer.

(Comparative Example 2)
In Comparative Example 2, a solid electrolytic capacitor was produced by the same method as in the example. However, the pH of the conductive polymer dispersion solution was set to 2-3.

(Analysis 1)
Table 1 shows capacitance values at a frequency of 120 Hz, tan δ, ESR at a frequency of 100 kHz, short-circuit occurrence rate, and leakage current at 2 minutes after application of the rated voltage of the solid electrolytic capacitors according to Examples and Comparative Examples 1 and 2. . 50 solid electrolytic capacitors according to Examples and Comparative Examples 1 and 2 were manufactured, and each value in Table 1 represents an average value thereof.

  As shown in Table 1, in the example, a high capacitance was obtained, and Tan δ, leakage current, and ESR were reduced. Moreover, no short circuit occurred. In Comparative Example 1, the leakage current increased and the occurrence rate of short circuit increased. This is presumably because the oxide film deteriorated due to the influence of acidity caused by the oxidizing agent when forming the solid electrolyte layer. When the appearance of the solid electrolytic capacitor according to Comparative Example 2 was confirmed, the solid electrolyte layer was not formed. Therefore, it was found that when an acidic conductive polymer dispersion solution was used, the immersion of the conductive polymer in cellulose was suppressed.

(Analysis 2)
Next, the leakage current with respect to the applied voltage was measured for the solid electrolytic capacitors according to the example and the comparative example 1. FIG. 7 shows the result. In FIG. 7, the horizontal axis indicates the applied voltage, and the vertical axis indicates the leakage current. As shown in FIG. 7, in the solid electrolytic capacitor according to the example, no significant change was observed in the leakage current up to the vicinity of the coating withstand voltage of the anode foil 10. Compared with this, in the solid electrolytic capacitor according to Comparative Example 1, the leakage current increased from around 25V. When compared at a leakage current of 10 mA, the withstand voltage of the solid electrolytic capacitor according to Comparative Example 1 was less than half that of the solid electrolytic capacitor according to the example. Therefore, it was found that the solid electrolytic capacitor according to Comparative Example 1 has a low withstand voltage. This is presumably because the oxide film deteriorated due to the influence of acidity caused by the oxidizing agent when forming the solid electrolyte layer.

(Analysis 3)
Next, the heat resistance of the solid electrolytic capacitors according to Examples and Comparative Examples 1 and 2 was examined. Each solid electrolytic capacitor was immersed in a solder bath at 260 ° C. for 60 seconds, and after checking the electrical characteristics and appearance, solder immersion was further performed three times in total to check the electrical characteristics and appearance. The results are shown in Table 2. Each value represents an average value of 50 pieces. However, the electrical characteristic value of Comparative Example 1 shows the average value of the solid electrolytic capacitor excluding the shorted product in Table 1.

  As shown in Table 2, in the solid electrolytic capacitor according to the example, the change in leakage current was smaller than that of the solid electrolytic capacitor according to Comparative Example 1. As for the appearance, the solid electrolytic capacitor according to Comparative Example 1 was abnormal (swelled). This is presumably because p-toluenesulfonic acid caused an oxidation reaction with cellulose to generate moisture and the internal pressure increased. Compared with this, no abnormality was found in the solid electrolytic capacitor according to the example.

  From the above, it has been found that the deterioration of the oxide film of the anode foil is suppressed by forming the solid electrolyte layer using the conductive polymer dispersion solution of pH 5 to pH 8. It has been found that when a separator mainly composed of cellulose is used, a solid electrolyte can be efficiently formed by using a conductive polymer dispersion solution having a pH of 5 to 8. Moreover, the swelling was suppressed by using the conductive polymer dispersion solution.

It is a figure for demonstrating the manufacturing method of the solid electrolytic capacitor which concerns on one embodiment of this invention. It is a figure for demonstrating the manufacturing method of the solid electrolytic capacitor which concerns on one embodiment of this invention. It is a figure for demonstrating the manufacturing method of the solid electrolytic capacitor which concerns on one embodiment of this invention. It is a figure for demonstrating the manufacturing method of the solid electrolytic capacitor which concerns on one embodiment of this invention. It is the external view of a solid electrolytic capacitor, and a partially cutaway sectional view. It is a typical sectional view of a lamination type solid electrolytic capacitor. It is a figure which shows the result of a leakage current test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Anode foil 11 Anode terminal 20 Cathode foil 21 Cathode terminal 30 Separator 40 Sealing member 50 Bar 60 Conductive polymer dispersion solution 70 Solid electrolyte layer 100 Winding element 200 Capacitor element 300 Solid electrolytic capacitor

Claims (6)

An arrangement step of arranging a separator between an anode foil made of aluminum and subjected to chemical conversion treatment on the surface and a cathode foil holding carbide particles on the surface;
Forming a solid electrolyte layer by impregnating and drying a conductive polymer dispersion solution having a pH of 5 to 8 between the anode foil and the separator and between the cathode foil and the separator; A method for producing a solid electrolytic capacitor, comprising:   The solid electrolysis according to claim 1, further comprising an adjustment step of adjusting the pH of the conductive polymer dispersion solution to 5 to 8 by adding a pH adjuster to the conductive polymer dispersion solution. Capacitor manufacturing method.   The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive polymer dispersion solution contains at least one of polythiophene and polystyrene.   The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the separator is made of a fiber mainly composed of cellulose.   The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the arranging step is a step of winding the anode foil and the cathode foil through the separator. The method for producing a solid electrolytic capacitor according to claim 1, wherein the pH of the conductive polymer dispersion solution is 6.1 to 6.9.

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