JP2013131514A - Solid electrolytic capacitor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which can be improved in ESR characteristics under a high-temperature atmosphere and ESR characteristics during reflow.SOLUTION: The solid electrolytic capacitor includes a dielectric oxide film formed on a surface of an anode body having an expanded layer, a first conductive polymer layer formed on the oxide film, a second conductive polymer layer formed on the first conductive polymer layer, and a cathode conductor layer formed on the second conductive polymer layer. A mixed solution obtained by dispersing a conductive polymer compound in a solution containing water, ethylene glycol, and a nitro compound is applied to the first conductive polymer layer and then is dried to form the second conductive polymer layer.

Description

  The present invention relates to a solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte and a method for manufacturing the same.

  Conventionally, a solid electrolytic capacitor using a conductive polymer as a solid electrolyte is known. Recently, a capacitor in which two layers of a conductive polymer are formed has been proposed. This type of solid electrolytic capacitor is formed by, for example, forming a first conductive polymer layer by chemical polymerization on the inside in order to compensate for the drawbacks of conventional conductive polymers produced by chemical oxidation polymerization or electrolytic oxidation polymerization. Further, a second conductive polymer layer is formed by immersing and drying an aqueous suspension of the conductive polymer compound on the outside (see Patent Document 1).

  However, in the above solid electrolytic capacitor, the conductive polymer layer formed on the outer surface of the element has a constant thickness. Therefore, when the second conductive polymer layer is formed, the conductive polymer compound is suspended. The viscosity of the aqueous solution may be increased. In this case, since the aqueous suspension of the conductive polymer compound does not sufficiently penetrate into the etching pit, the connection state between the first conductive polymer layer and the second conductive polymer layer is deteriorated, and ESR. There was a problem that it was not possible to reduce this.

  In order to solve the above problems, a method for producing a solid electrolytic capacitor by applying a dispersion of a conductive polymer compound to which a glycol solvent is added to form an outer conductive polymer layer has been proposed. Yes. In this method, by adding a glycol-based solvent to the dispersion, adhesion with the underlying polymer layer is improved, and an increase in ESR is suppressed (see Patent Document 2).

Japanese Patent Laid-Open No. 11-121281 Japanese Patent Laid-Open No. 2007-299856

  Currently, solid electrolytic capacitors using a conductive polymer as a solid electrolyte are required to improve not only initial ESR characteristics but also ESR characteristics in a high temperature atmosphere and ESR characteristics during reflow. However, the above-described solid electrolytic capacitor is not always satisfactory in these characteristics.

  The present invention has been made to solve the above-described problems, and its object is to provide a solid electrolytic capacitor capable of improving ESR characteristics under a high temperature atmosphere and ESR characteristics during reflow, and a method for manufacturing the same. It is to provide.

  As a result of intensive studies on solid electrolytic capacitors to solve the above-mentioned problems, the present inventors have found that a conductive polymer using a mixed solution in which a conductive polymer compound is dispersed in a solution containing water, ethylene glycol and a nitro compound. By forming the layer, it was found that ESR under high-temperature atmosphere and reflow can be reduced, and the present invention has been completed.

  That is, the present invention provides a dielectric oxide film formed on the surface of an anode body having a surface-enlarging layer, a conductive polymer layer formed on the oxide film, and formed on the conductive polymer layer. In the solid electrolytic capacitor comprising the cathode body, the conductive polymer layer is obtained using a mixed solution in which the conductive polymer compound is dispersed in a solution containing at least ethylene glycol and a nitro compound. It is characterized by.

  The present invention also includes a step of forming a dielectric oxide film on the surface of an anode body having a surface-enlarging layer, a step of forming a conductive polymer layer on the oxide film, and a step on the conductive polymer layer. Forming a cathode body on a solid electrolytic capacitor, wherein the step of forming the conductive polymer layer comprises dispersing the conductive polymer compound in a solution containing water, ethylene glycol, and a nitro compound. It is characterized by forming using the mixed solution.

  ADVANTAGE OF THE INVENTION According to this invention, the solid electrolytic capacitor which can improve the ESR characteristic in a high temperature atmosphere and the ESR characteristic at the time of reflow, and its manufacturing method can be provided.

  Hereinafter, the solid electrolytic capacitor according to the present invention will be described in order according to an example of the manufacturing method.

(Formation of dielectric oxide film)
First, a surface of a flat aluminum etched foil (anode body) having a size of 10 × 10 mm or the like is subjected to a chemical conversion treatment, for example, in an aqueous solution of ammonium adipate at 5 V for about 30 minutes, thereby producing an aluminum dielectric. An oxide film is formed. Next, this anode body is immersed in a predetermined chemical conversion solution, and a voltage is applied to perform restoration conversion.

  As the chemical solution for restoration chemical conversion, phosphoric acid type chemicals such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate, boric acid type chemicals such as ammonium borate, and adipic acid type chemicals such as ammonium adipate, etc. Although a liquid can be used, it is preferable to use ammonium dihydrogen phosphate. Further, it is desirable that the time for repairing and forming by immersing the capacitor element in the chemical liquid and applying voltage is 5 to 120 minutes.

(Formation of first conductive polymer layer)
Next, a dispersion liquid in which a conductive polymer compound is dispersed is applied, for example, five times on the aluminum dielectric oxide film, and then heated at 150 ° C. for 60 minutes to form a first conductive polymer layer. .

  Examples of the dispersion in which the conductive polymer compound is dispersed include, for example, a conductive polymer compound powder made of poly- (3,4-ethylenedioxythiophene) (hereinafter referred to as PEDOT) and a dopant made of polystyrene sulfonic acid. A solution in which a solid content is mixed in a solvent water can be used. Moreover, the density | concentration of a conductive polymer compound can be 1-10% with respect to aqueous solution. In addition, the solvent of the dispersion liquid of the conductive polymer compound may be other than water as long as the conductive polymer compound can be dissolved.

(Formation of second conductive polymer layer)
Next, a mixed solution composed of a dispersion in which the same or different conductive polymer compound as the conductive polymer compound is dispersed and ethylene glycol and a nitro compound is applied on the first conductive polymer layer, for example, five times. After that, the second conductive polymer layer is formed by heating at 150 ° C. for 60 minutes.

  As the dispersion liquid in which the conductive polymer compound is dispersed, a conductive material composed of PEDOT having a concentration of 1 to 10% with respect to the aqueous solution is used in the same manner as the dispersion liquid used for forming the first conductive polymer layer. A dispersion containing a functional polymer compound can be used. Ethylene glycol and a nitro compound are further added to this dispersion. As is apparent from the results of Examples described later, the amount added is 50 parts by weight of the dispersion, 35 to 49 parts by weight of ethylene glycol, and 1 to less than 15 parts by weight of the nitro compound when the entire mixed solution is 100 parts by weight. It is preferable that

  Moreover, examples of the nitro compound include aliphatic nitro compounds and aromatic nitro compounds. Among these, as is apparent from the results of Examples described later, m-nitrophenol (mNPh), p-nitrophenol (pNPh) or m-Nitroacetophenone (mNAc) is preferred.

  When the second conductive polymer layer is formed using the mixed solution in the above ratio, the content of the nitro compound in the entire second conductive polymer layer after drying is determined by the weight ratio of the conductive polymer. When 1 is 1, the range of nitro compounds is less than 10.

(Formation of cathode conductor layer)
Furthermore, a carbon layer is applied on the second conductive polymer layer and dried at 150 ° C. for 30 minutes, and then a silver paste layer is applied and dried at 180 ° C. for 60 minutes to thereby form a cathode conductor layer. Form.

  The first conductive polymer layer is formed by applying and drying a dispersion liquid in which a conductive polymer compound is dispersed on a dielectric oxide film. The formed anode body is immersed in an oxidizing agent (ferric toluene sulfonate) and 3,4-ethylenedioxythiophene (ethanol solution), and subjected to heat polymerization at 60 ° C. for 30 minutes and at 150 ° C. for 60 minutes. It can also be formed by performing.

(Action / Effect)
By forming a conductive polymer layer using a mixed solution in which a conductive polymer compound is dispersed in a solution containing water, ethylene glycol, and a nitro compound, the ESR characteristics of the obtained solid electrolytic capacitor are improved. ESR characteristics at high temperatures were also good. This is because ethylene glycol contained in the mixed solution can improve the orientation of the conductive polymer compound to form a good conductive polymer layer, and further, the conductive polymer with improved orientation. It is presumed that the nitro compound incorporated in the layer suppresses the thermal deterioration of the conductive polymer layer and improves the ESR characteristics at high temperatures. In addition, a conductive polymer layer formed by using a mixed polymer solution in which a conductive polymer compound is dispersed in a solution containing water, ethylene glycol, and a nitro compound is formed on the outside using a two-layer conductive polymer layer. This is considered to be more effective in suppressing thermal degradation and improving ESR characteristics at higher temperatures.

Hereinafter, the effect of the present invention will be demonstrated by examples.
[Experiment 1] (Examination of various additives)
A flat aluminum etched foil having a size of 10 × 10 mm was formed in an aqueous solution of ammonium adipate at 5 V for 30 minutes to form an aluminum dielectric oxide film on the surface. Subsequently, it was immersed in an aqueous solution of ammonium dihydrogen phosphate, and restoration was performed for 40 minutes by applying a voltage. Next, a conductive polymer compound powder made of PEDOT and a solid content of a dopant made of polystyrene sulfonic acid are mixed with water to produce a dispersion liquid having a concentration of 3% of the conductive polymer compound in the aqueous solution. did. The dispersion was applied five times on the aluminum dielectric oxide film, and then heated at 150 ° C. for 60 minutes to form a first conductive polymer layer.

  Next, using the above dispersion having a conductive polymer compound concentration of 3% with respect to the aqueous solution, a mixed solution (conventional example 1) containing 50 parts by weight of this dispersion and 50 parts by weight of ethylene glycol, dispersion 50 Part by weight, 49 parts by weight of water, 1 part by weight of p-nitrophenol (pNPh) mixed solution (conventional example 2), 50 parts by weight of dispersion, 49 parts by weight of ethylene glycol, 1 part by weight of p-nitrophenol (pNPh) Mixed solution (Example 1), dispersion 50 parts by weight, ethylene glycol 49 parts by weight, m-nitroacetophenone (mNAc) 1 part by weight, mixed solution (Example 2), dispersion 50 parts by weight, ethylene glycol 49 parts by weight, mixed solution (Example 3) containing 1 part by weight of m-nitrophenol (mNPh), 50 parts by weight of dispersion, 49 parts by weight of ethylene glycol, p-aminopheno A mixed solution (Comparative Example 1) containing 1 part by weight of p (pAmPh) was applied once on the first conductive polymer layer and heated at 150 ° C. for 60 minutes to thereby form the second conductive polymer. A layer was formed. Further, a carbon layer is applied on the second conductive polymer layer and dried at 150 ° C. for 30 minutes, and then a silver paste layer is applied and dried at 180 ° C. for 60 minutes to form a cathode conductor layer. Formed.

For the solid electrolytic capacitors of Conventional Examples 1 and 2 and Examples 1 to 3 and Comparative Example 1 thus manufactured, the initial capacity, ESR after reflow (100 kHz), and ESR (100 kHz) after 170 hours at 170 ° C. were measured. did. The measurement results are shown in Table 1.

  From the results of Table 1, it was confirmed that Examples 1 to 3 can reduce ESR after reflow compared to Conventional Examples 1 and 2. Further, ESR after 66 hours at 170 ° C. is also suppressed in Examples 1 to 3 as compared with Conventional Examples 1 and 2. On the other hand, in Comparative Example 1, the initial capacity was reduced as compared with Conventional Examples 1 and 2, and ESR after 170 hours at 170 ° C. was greatly deteriorated. From this, it was found that the addition of p-nitrophenol (pNPh), m-nitroacetophenone (mNAc) or m-nitrophenol (mNPh) was effective in reducing ESR after reflow and after 170 hours at 170 ° C. .

[Experimental example 2] (Comparison of added solvents)
As in Example 1, as a mixed solution for forming the second conductive polymer layer, a solid electrolytic capacitor was prepared using 50 parts by weight of the dispersion, 49 parts by weight of ethylene glycol, and 1 part by weight of p-nitrophenol (pNPh). Created (Example 4). Further, as a mixed solution for forming the second conductive polymer layer, a dispersion solution of 50 parts by weight, diethylene glycol 49 parts by weight, p-nitrophenol (pNPh) 1 part by weight (Comparative Example 2), dispersion liquid A solid electrolytic capacitor was produced in the same manner as in Example 1 except that 50 parts by weight, 49 parts by weight of glycerin and 1 part by weight of p-nitrophenol (pNPh) were used (Comparative Example 3). Table 2 shows the results of measuring ESR (100 kHz) after reflow and ESR (100 kHz) after 170 hours at 170 ° C. for these solid electrolytic capacitors.

  From the results in Table 2, the ESR after 66 hours at 170 ° C. increased in Comparative Examples 2 and 3 as compared with Example 4. From this, it was found that ethylene glycol is preferable as the additive solvent.

[Experimental Example 3] (Change in the amount of p-nitrophenol added)
As in Conventional Example 1, a solid electrolytic capacitor was prepared as a mixed solution for forming the second conductive polymer layer by using 50 parts by weight of the dispersion and 50 parts by weight of ethylene glycol (Conventional Example 3). As in Example 1, as a mixed solution for forming the second conductive polymer layer, a solid electrolytic capacitor was prepared using 50 parts by weight of the dispersion, 49 parts by weight of ethylene glycol, and 1 part by weight of p-nitrophenol (pNPh). Created (Example 5). Further, as a mixed solution for forming the second conductive polymer layer, a dispersion solution of 50 parts by weight, ethylene glycol 45 parts by weight, p-nitrophenol (pNPh) 5 parts by weight (Example 6), 50 parts by weight of dispersion, 40 parts by weight of ethylene glycol, 10 parts by weight of p-nitrophenol (pNPh) (Example 7), 50 parts by weight of dispersion, 35 parts by weight of ethylene glycol, p-nitrophenol (pNPh) A solid electrolytic capacitor was produced in the same manner as in Example 1 except that 15 parts by weight (Comparative Example 4) was used. Table 3 shows the results of measuring the initial capacity, ESR after reflow (100 kHz), and ESR (100 kHz) after 170 hours at 170 ° C. for these solid electrolytic capacitors.

  From the results of Table 3, in Examples 5 to 7, both ESR after reflow and ESR after 170 hours at 170 ° C. were good. In contrast, in Conventional Example 3, the ESR after reflow was good, but the ESR after 170 hours at 170 ° C. was greatly deteriorated. In Comparative Example 4, both the ESR after reflow and the ESR after 170 hours at 170 ° C. were deteriorated. From this, it is considered that the addition amount of p-nitrophenol is preferably 1 part by weight or more and less than 15 parts by weight. Further, when these conductive polymer layers were analyzed, the weight ratio of the conductive polymer and p-nitrophenol contained in the conductive polymer layer was determined as follows. It has been found that less than 10, particularly 7 or less is preferable.

Claims (8)

A dielectric oxide film formed on the surface of an anode body having a surface-enlarging layer; a conductive polymer layer formed on the oxide film; a cathode body formed on the conductive polymer layer; In a solid electrolytic capacitor with
A solid electrolytic capacitor, wherein the conductive polymer layer is obtained using a mixed solution in which a conductive polymer compound is dispersed in a solution containing at least ethylene glycol and a nitro compound.   The weight ratio of the conductive polymer compound and the nitro compound in the conductive polymer layer is such that the amount of the nitro compound is less than 10 when the amount of the conductive polymer compound is 1. The solid electrolytic capacitor according to claim 1.   The solid electrolytic capacitor according to claim 1, wherein the nitro compound is m-nitrophenol, p-nitrophenol, or m-nitroacetophenone.   The conductive polymer layer includes a first conductive polymer layer formed on the oxide film and a second conductive polymer layer formed on the outside thereof, and the second conductive polymer layer. The solid electrolytic capacitor according to claim 1, wherein a molecular layer is formed using the mixed solution. Forming a dielectric oxide film on the surface of the anode body having a surface-enlarging layer;
Forming a conductive polymer layer on the oxide film;
Forming a cathode body on the conductive polymer layer;
In a method for producing a solid electrolytic capacitor comprising:
The step of forming the conductive polymer layer is formed using a mixed solution in which a conductive polymer compound is dispersed in a solution containing water, ethylene glycol and a nitro compound.   6. The method for producing a solid electrolytic capacitor according to claim 5, wherein the nitro compound is 1 part by weight or more and less than 15 parts by weight when the entire mixed solution is 100 parts by weight.   The method for producing a solid electrolytic capacitor according to claim 5 or 6, wherein the nitro compound is m-nitrophenol, p-nitrophenol or m-nitroacetophenone.   The step of forming the conductive polymer layer includes a step of forming a first conductive polymer layer on the oxide film, and a second conductive polymer layer on the first conductive polymer layer. The step of forming the second conductive polymer layer includes forming the second conductive polymer layer by applying the mixed solution to the first conductive polymer layer. The method for producing a solid electrolytic capacitor according to any one of claims 1 to 7.