JP6965970B2 - Manufacturing method of solid electrolytic capacitor and solid electrolytic capacitor - Google Patents

Description

The present invention relates to a solid electrolytic capacitor and a method for producing the same, and more particularly to a solid electrolytic capacitor suitable for high voltage applications of 80 WV or higher and a method for producing the same.

In recent years, there is a strong demand for miniaturization and large capacity of solid electrolytic capacitors used for power supply to digitized electric devices. A solid electrolytic capacitor using a metal having a valve action such as aluminum can obtain a small size and a large capacity by forming the valve action metal as an anode foil into a shape such as an etching foil and expanding the dielectric surface. It is widely used because it can be used.

A solid electrolytic capacitor for small and large capacity applications generally has a capacitor element formed by winding an anode foil and a cathode foil made of a valve acting metal such as aluminum with a separator interposed therebetween. The solid electrolytic capacitor has a structure in which the capacitor element is impregnated with a driving electrolytic solution, the capacitor element is housed in a metal case such as aluminum or a synthetic resin case, and the capacitor element is sealed. As the anode material, tantalum, niobium, titanium and the like are used, including aluminum, and as the cathode material, a metal of the same type as the anode material is used.

Further, as a solid electrolyte used for a solid electrolytic capacitor, manganese dioxide and a 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex are known, but in recent years, the reaction rate is slow and the anode is an anode. There is a technique (Patent Document 1) focusing on a conductive polymer such as polyethylenedioxythiophene (hereinafter referred to as PEDOT), which has excellent adhesion to the oxide film layer of the foil.

Japanese Unexamined Patent Publication No. 2-15511

By the way, as a solid electrolytic capacitor for an automobile or a general power supply circuit, a capacitor for a low voltage of about 25 WV or 63 WV is used. However, in recent years, there has been a demand for solid electrolytic capacitors having good ESR characteristics at high temperatures for use in high voltage applications of 80 WV or higher.

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a solid electrolytic capacitor having excellent characteristics in high voltage applications of 80 WV or more and a method for manufacturing the same.

As a result of various studies to solve the above problems, the present inventors have improved ESR characteristics by using an aliphatic carboxylic acid as a solute of the electrolytic solution to be filled in the capacitor element in a high pressure region exceeding 80 WV. Based on this finding, the present invention has been completed.

That is, the solid electrolytic capacitor of the present invention has a capacitor element in which an anode foil and a cathode foil are wound via a separator, and the capacitor element has a solid electrolyte layer containing a conductive polymer. the void portion in the capacitor element, the electrolytic solution is filled, the electrolyte may include ammonium salts of aliphatic carboxylic acids as a solute, and a polyhydric alcohol as a solvent, the acid of the solute in front Symbol solvent der the amount is 0.6 mol / kg or less of is, the electrolyte solution, wherein the electrolyte der Rukoto without addition of water as the solvent.

The polyhydric alcohol may be ethylene glycol. The electrolytic solution may be a non-aqueous electrolytic solution that does not contain water as the solvent. The electrolytic solution may further contain boric acid and mannitol.

Further, the method for manufacturing the solid electrolytic capacitor as described above is also one aspect of the present invention.

According to the present invention, it is possible to provide a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor having excellent characteristics in high voltage applications of 80 WV or more.

It is a perspective view which shows an example of the structure of the solid electrolytic capacitor of 1st Embodiment.

[1. composition]
Hereinafter, the solid electrolytic capacitor of the present embodiment will be described in detail with reference to FIG. As shown in FIG. 1, the solid electrolytic capacitor has a capacitor element 10 in which an anode foil 1 and a cathode foil 2 are wound around a separator 3. The solid electrolytic capacitor is manufactured by storing the capacitor element 10 together with the electrolytic solution in a bottomed cylindrical outer case (not shown) and sealing the capacitor element 10.

The anode foil 1 is made of a valve metal foil having a dielectric film on its surface. As the valve metal foil, aluminum, tantalum, niobium, titanium and the like can be used. The surface area of the valve metal foil may be expanded by roughening the surface by performing an electrochemical etching treatment in an aqueous chloride solution. Further, the dielectric film can be formed by performing a chemical conversion treatment using, for example, ammonium oxide, ammonium borate, or the like. The cathode foil 2 is made of a valve metal foil similar to the anode foil 1. The surface of the cathode foil may also be roughened by etching. Further, a thin dielectric film (about 1 to 10 V) may be formed on the cathode foil 2 by chemical conversion treatment, if necessary. Hereinafter, the anode foil 1 and the cathode foil 2 may be collectively referred to as an electrode foil. The dimensions of the electrode foil can be arbitrarily set according to the specifications of the solid electrolytic capacitor to be manufactured.

As shown in FIG. 1, lead wires 4 and 5 for connecting the electrodes to the outside are connected to the anode foil 1 and the cathode foil 2 by, for example, stitching or ultrasonic welding. The lead wires 4 and 5 are formed of aluminum or the like. The lead wires 4 and 5 are electrode drawing means for electrically connecting the anode foil 1 and the cathode foil 2 to the outside, and are derived from the end faces of the wound capacitor elements.

As the separator 3, a non-woven fabric mainly composed of synthetic fibers or glass fibers can be used. Examples of the synthetic fiber include polyester fiber, nylon fiber, rayon fiber and the like, and these fibers may be used alone or in combination. Further, a separator made of natural fiber may be used. The separator 3 may have a width slightly larger than that depending on the dimensions of the anode foil 1 and the cathode foil 2.

The capacitor element 10 formed as described above may be repaired and formed. Mechanical stress is applied to the electrode foil when winding the capacitor element, which may cause damage such as cracks in the dielectric film. In the restoration chemical formation, the capacitor element 10 is immersed in the chemical conversion liquid to be formed, so that a dielectric film is formed on the cracked portion, and the damage can be repaired. As the chemical conversion solution, a phosphoric acid-based chemical conversion solution such as ammonium dihydrogen phosphate or diammonium hydrogen phosphate, a boric acid-based chemical conversion solution such as ammonium borate, or an adipic acid-based chemical conversion solution such as ammonium adipate is used. be able to. Among these, it is particularly preferable to use ammonium dihydrogen phosphate.

A solid electrolyte layer is formed on the capacitor element 10. Specifically, the solid electrolyte layer is formed on the separator 3 and the electrode foil. The solid electrolyte layer can be formed by immersing the capacitor element 10 in the conductive polymer dispersion and then drying it. The steps of dipping and drying in the conductive polymer dispersion may be repeated a plurality of times. The conductive polymer dispersion is a solution in which particles of the conductive polymer are dispersed in a solvent. As the conductive polymer, for example, PEDOT powder can be used. Further, the solvent may contain a solid content of polystyrene sulfonic acid as a dopant.

The solvent of the conductive polymer dispersion may be any one in which particles or powders of the conductive polymer are dissolved, and water is mainly used. However, ethylene glycol may be used alone or in combination as a solvent for the dispersion, if necessary. It has been found that the use of ethylene glycol as the solvent for the dispersion can reduce ESR in particular among the electrical properties of the product. In order to improve the impregnation property and conductivity of the conductive polymer dispersion, various additives may be added to the conductive polymer dispersion, or neutralization may be performed by adding a cation. In particular, when sorbitol or sorbitol and a polyhydric alcohol are used as additives, ESR can be reduced and deterioration of withstand voltage characteristics due to lead-free reflow or the like can be prevented.

The concentration of the conductive polymer can be 1 to 10 wt% with respect to the aqueous solution. The particles of the conductive polymer include primary particles of the conductive polymer, agglomerates (secondary particles) in which the conductive polymer compound and the dopant are aggregated, and powders thereof.

Specifically, as the conductive polymer, it is preferable to use a mixture of particles of thiophene or a derivative thereof and a solid content of a dopant composed of high molecular weight sulfonic acid. The conductive polymer dispersion is obtained by oxidatively polymerizing thiophene, which is a polymerizable monomer, or a derivative thereof in water or an aqueous solution in the presence of a polymer sulfonic acid as a dopant. Examples of the thiophene derivative in the conductive polymer thiophene or its derivative include 3,4-ethylenedioxythiophene, 3-alkylthiophene, 3-alkoxythiophene, 3-alkyl-4-alkoxythiophene, 3,4. -Alkylthiophene, 3,4-alkoxythiophene and the like can be mentioned. The alkyl group and the alkoxy group preferably have 1 to 16 carbon atoms, but 3,4-ethylenedioxythiophene is particularly preferable. Moreover, not only thiophene but also pyrrole and its derivative may be used. Particularly preferable conductive polymers obtained from these polymerizable monomers include polythiophene, polyethylenedioxythiophene, and polypyrrole.

The capacitor element 10 on which the solid electrolyte layer is formed is immersed in the electrolytic solution, and the voids in the capacitor element 10 are filled with the electrolytic solution. When the electrolytic solution is filled in the capacitor element 10, the filling amount is arbitrary as long as the electrolytic solution can be filled in the voids in the capacitor element 10, but it is preferably 3 to 100% of the voids in the capacitor element 10.

As the electrolytic solution of the present embodiment, a non-aqueous electrolytic solution containing no water is used as the solvent. In the present specification, the non-aqueous electrolytic solution is an electrolytic solution to which water is not added at the time of preparing the electrolytic solution. When a non-aqueous electrolyte solution is used, an increase in ESR can be suppressed as compared with the case where an aqueous electrolyte solution containing water is used as the solvent. However, although the moisture contained in the air or the separator is mixed in the solid electrolytic capacitor in the manufacturing process, if the amount of moisture contained in the solid electrolytic capacitor can be controlled to 3 wt% or less, there is no possibility that the ESR will increase.

As the solvent that can be used in the electrolytic solution, it is preferable to use a solvent having a boiling point of 120 ° C. or higher because the electrolytic solution does not easily volatilize. Examples of the solvent include polyhydric alcohols such as γ-butyrolactone and ethylene glycol, sulfolanes, dimethylformamide and the like. Polyhydric alcohols include ethylene glycol, diethylene glycol, dipropylene glycol, 1,2-propanediol, glycerin, 1,3-propanediol, 1,3-butanediol, 2-methyl-2,4-pentanediol and the like. Low molecular weight polyhydric alcohol is preferable. In particular, when a solvent containing ethylene glycol is used, the initial ESR characteristics are improved, and the high temperature characteristics are also improved. The amount of ethylene glycol added in the mixed solvent is preferably 5 wt% or more, more preferably 40 wt% or more, and most preferably 60 wt% or more.

Further, by adding a predetermined amount of γ-butyrolactone as a solvent, the impregnation property of the electrolytic solution into the capacitor element 10 can be improved. By using ethylene glycol having a relatively high viscosity and γ-butyrolactone having a low viscosity, the impregnation property of the capacitor element 10 can be enhanced. Therefore, the initial characteristics and good characteristics after long-term use are maintained, and the charge / discharge characteristics at low temperature are good. The amount of γ-butyrolactone added in the mixed solvent is preferably 40 wt% or less.

Further, at least one solvent selected from sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane may be additionally used as the ethylene glycol solvent of the ionic conductive substance. Since these sulfolane-based solvents have a high boiling point, the volatilization of the electrolytic solution is suppressed and the high temperature characteristics are improved. The amount of these sulfolane-based solvents added to the mixed solvent is preferably 40 wt% or less.

The solute of the electrolytic solution contains an ammonium salt of an aliphatic carboxylic acid. It is preferable to use an ammonium salt of an aliphatic carboxylic acid because the pressure resistance characteristics are improved. Examples of the aliphatic carboxylic acid include azelaic acid, adipic acid, 1,6-decandicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-methoxycarbonyl-1,9-decandicarboxylic acid, 7,9. Aliphatic dicarboxylic acids such as −dimethyl-7,9-dimethoxycarbonyl-1,11-dodecanedicarboxylic acid, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid, and other aliphatic acids. An aliphatic polyvalent carboxylic acid such as a monocarboxylic acid or an aliphatic tricarboxylic acid can be used. These aliphatic carboxylic acids may be used alone or in combination. Further, it is preferable to use an aliphatic carboxylic acid having a molecular weight of 150 or more. As the molecular weight of the aliphatic carboxylic acid increases, the withstand voltage characteristics of the solid electrolytic capacitor are further improved. Further, the solute may contain a solute other than the ammonium salt of the aliphatic carboxylic acid, but it is preferable to use the ammonium salt of the aliphatic carboxylic acid as the main solute. Here, the main solute means that it occupies 50 wt% or more with respect to the total solute.

In the above electrolytic solution, as is clear from the results of Examples described later, the amount of solute acid added to the solvent is preferably 0.6 mol / kg or less. By setting the addition amount of the solute acid to the solvent to 0.6 mol / kg or less, changes in capacitance and ESR in the load test can be suppressed at a high pressure of 80 WV or more.

Furthermore, as additives for the electrolytic solution, polyoxyethylene glycol, a complex compound of boric acid and polysaccharides (mannit, sorbit, etc.), a complex compound of boric acid and polyhydric alcohol, and a nitro compound (o-nitrobenzoic acid) , M-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, etc.), phosphate esters and the like. Among these, the addition of boric acid and mannitol is particularly preferable because changes in capacitance and ESR can be further suppressed in the load test.

[2. Manufacturing method of solid electrolytic capacitor]
The method for manufacturing a solid electrolytic capacitor of the present embodiment as described above includes the following steps.
(1) Step of forming a capacitor element (2) Step of forming a solid electrolyte layer on a capacitor element (3) Step of filling a void in a capacitor element with an electrolytic solution (4) Step of forming a solid electrolytic capacitor

Hereinafter, each step will be described in detail.
(1) Step of Forming a Capacitor Element In the step of forming a capacitor element 10, an anode foil 1 and a cathode foil 2 are wound around a separator 3 to form a capacitor element 10. The anode foil 1 is formed of, for example, an etching foil obtained by etching a flat plate-shaped valve acting metal foil such as aluminum and further forming a dielectric film by a chemical conversion treatment. The cathode foil 2 is formed of, for example, an etching foil obtained by etching a flat metal foil in the same manner as the anode foil 1. Lead wires 4 and 5 are connected to the anode foil 1 and the cathode foil 2, respectively. The capacitor element 10 is formed by winding the anode foil 1 and the cathode foil 2 as described above so as to sandwich the separator 3 in between. The formed capacitor element 10 may be immersed in a repair liquid for repair chemical formation. The immersion time is preferably 5 to 120 minutes.

(2) Step of Forming a Solid Electrolyte Layer on the Capacitor Element The capacitor element 10 is immersed in a conductive polymer dispersion and then dried to form the solid electrolyte layer 7. The time for immersing the capacitor element 10 in the conductive polymer dispersion is determined by the size of the capacitor element 10, but for a capacitor element having a diameter of 5 mm × height of about 3 mm, it takes 5 seconds or more, and a capacitor having a diameter of 9 mm × height of about 5 mm. The element is preferably immersed for 10 seconds or longer, and is required to be immersed for at least 5 seconds. Even if it is immersed for a long time, there is no adverse effect on its characteristics. Further, it is preferable to hold the product in a reduced pressure state after immersing it in this way. The reason is considered to be that the residual amount of the volatile solvent is reduced. The impregnation and drying of the conductive polymer dispersion may be performed a plurality of times, if necessary.

After immersing the conductive polymer dispersion in the capacitor element 10, the capacitor element 10 is dried at a predetermined temperature. The drying temperature is preferably 100 to 160 ° C., and the drying time is preferably 0.5 to 3 hours. Through this drying step, a solid electrolyte layer containing a conductive polymer is formed in the capacitor element 10, particularly on the dielectric film in the etching pit of the etching foil.

(3) Step of Filling the Voids in the Capacitor Element with the Electrolyte The capacitor element 10 on which the solid electrolyte layer 7 is formed is immersed in the electrolytic solution, and the voids in the capacitor 10 are filled with the electrolytic solution.

(4) Step of Forming a Solid Electrolytic Capacitor The capacitor element 10 is inserted into the outer case together with the electrolytic solution, a sealing rubber is attached to the end of the opening, and the capacitor element 10 is sealed by crimping. Then, aging is performed to prepare a solid electrolytic capacitor. In addition to the outer case, the capacitor element 10 can be covered with an insulating resin such as an epoxy resin and aged to produce a solid electrolytic capacitor.

[3. Action effect]
(1) The solid electrolytic capacitor of the present embodiment has a capacitor element 10 in which an anode foil 1 and a cathode foil 2 are wound around a separator 3, and the capacitor element 10 has a solid electrolyte layer. The voids in the condenser element 10 are filled with an electrolytic solution, and the electrolytic solution contains an ammonium salt of an aliphatic carboxylic acid as a solute and a polyhydric alcohol as a solvent, and the amount of the solute acid added to the solvent is large. It is 0.6 mol / kg or less.

As described above, the electrolytic solution contains an ammonium salt of an aliphatic carboxylic acid as a solute and a polyhydric alcohol as a solvent. When an ammonium salt of an aliphatic carboxylic acid is used as the solute, the pressure resistance property is improved at a high pressure of 80 WV or more. Further, by setting the addition amount of the solute acid to the solvent to 0.6 mol / kg or less, changes in capacitance and ESR can be suppressed at a high pressure of 80 WV or more.

When a solvent containing a polyhydric alcohol such as ethylene glycol is used, the initial ESR is lowered and the rate of change in capacitance during long-term use (compared to the case where a solvent not containing ethylene glycol is used. ΔCap) has been found to be small. The reason is that a polyhydric alcohol such as ethylene glycol has an effect of promoting the elongation of the polymer chain of the conductive polymer, so that it is considered that the conductivity is improved and the ESR is lowered.

In particular, in an electrolytic solution using an ammonium salt of an aliphatic carboxylic acid as a solute and a polyhydric alcohol such as ethylene glycol as a solvent, the solid electrolytic capacitor is exposed to a hot atmosphere to cause an esterification reaction in the electrolytic solution. Produces esters of polyhydric alcohols and carboxylic acids. In amine salts and the like, the aminium ion loses protons and is gasified by this esterification reaction, but since it has a high boiling point, it remains in the capacitor case, and as a result, the pH of the electrolytic solution changes excessively. , Deterioration of the conductive polymer is likely to occur. However, in the ammonium salt of an aliphatic carboxylic acid used as a solute as in the present invention, ammonium ions lose protons due to esterification and gasify and evaporate, so that the electrolyte solution is exposed to a hot atmosphere. It is considered that excessive change in pH of the above is unlikely to occur, and deterioration of the conductive polymer is reduced.

In addition, as a result of evaluating various solutes, the ammonium salt of the aliphatic carboxylic acid not only improves the chemical conversion property as an electrolytic solution, but also has good compatibility with a conductive polymer, and deteriorates the solid electrolyte layer in the high temperature durability test. It is considered that it is difficult, and it is considered that the lower the solute concentration, the more the deterioration of the solid electrolyte layer is suppressed. As described above, according to the present embodiment, it is possible to provide a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor having excellent characteristics in high voltage applications of 80 WV or more.

(2) The polyhydric alcohol may be ethylene glycol.
Protic and aprotic solvents with hydroxyl groups, such as ethylene glycol, have higher affinity for separators, electrode foils, and conductive polymers than γ-butyrolactone and sulfolane. Therefore, in the process of volatilizing the electrolytic solution when using a solid electrolytic capacitor, electric charges are easily transferred between the separator, the electrode foil, the conductive polymer and the electrolytic solution, and the capacitance change rate (ΔCap) is small. It is considered to be.

(3) The electrolytic solution may be a non-aqueous electrolytic solution that does not contain water as a solvent.
If an aqueous electrolytic solution containing water is used as the solvent, the conductive polymer of the electrode foil and the solid electrolyte layer may be deteriorated and the ESR may increase. In the present embodiment, since a non-aqueous electrolyte solution containing no water is used as the solvent, an increase in ESR can be suppressed as compared with the case where the aqueous electrolyte solution is used.

(4) The electrolytic solution may further contain boric acid and mannitol.
By adding boric acid and mannitol to the electrolytic solution, changes in capacitance and ESR can be further suppressed in the load test.

(5) The molecular weight of the aliphatic carboxylic acid may be 150 or more.
By using an aliphatic carboxylic acid having a molecular weight of 150 or more, the pressure resistance property at a high pressure exceeding 80 WV can be further improved.

Hereinafter, the present invention will be described in more detail based on Examples. The present invention is not limited to the following examples.

(1) Withstand voltage test of solid electrolytic capacitor (rated voltage 80WV)
First, in order to perform a withstand voltage test of a solid electrolytic capacitor having a rated voltage of 80 WV, the following solid electrolytic capacitor was produced.

<Manufacturing of Solid Electrolytic Capacitor of Example 1>
A lead wire, which is an electrode drawing means, is connected to an anode foil having a dielectric film layer formed on its surface and a cathode foil, and both electrode foils are wound via a Manila separator, and the element shape is 8 mm in diameter x high. A 10 mm capacitor element was formed. Then, this capacitor element was immersed in an aqueous ammonium dihydrogen phosphate solution for 40 minutes to carry out restoration and chemical formation.

Then, a conductive polymer dispersion in which PEDOT particles and polystyrene sulfonic acid were dispersed in an aqueous solution was prepared. The capacitor element was immersed in a conductive polymer dispersion, and the capacitor element was pulled up and dried at 150 ° C. for 30 minutes. The capacitor element was repeatedly immersed and dried in the conductive polymer dispersion a plurality of times to form a solid electrolyte layer made of the conductive polymer on the capacitor element.

Next, an ammonium salt of azelaic acid was added to ethylene glycol to prepare an electrolytic solution. The breakdown of the amount of ammonium azelaic acid added was 0.09 mol / kg of azelaic acid and 0.09 mol / kg of ammonium ion with respect to the solvent. Moreover, as an additive, a total of 2 wt% of phosphoric acid ester and p-nitrobenzoic acid was added to the electrolytic solution. After immersing the capacitor element in the prepared electrolytic solution, it was inserted into a bottomed cylindrical outer case, a sealing rubber was attached to the end of the opening, and the capacitor element was sealed by crimping. Then, aging was performed by applying a voltage to form a solid electrolytic capacitor. The rated capacity of this solid electrolytic capacitor is 39 μF.

<Manufacturing of Solid Electrolytic Capacitor of Example 2>
Azelaic acid was prepared in the same manner as in Example 1 except that the amount of ammonium azelaic acid added was 0.26 mol / kg for azelaic acid and 0.26 mol / kg for ammonium ions.

<Manufacturing of Solid Electrolytic Capacitor of Example 3>
Azelaic acid was prepared in the same manner as in Example 1 except that the amount of ammonium salt added was 0.37 mol / kg for azelaic acid and 0.37 mol / kg for ammonium ions.

<Manufacturing of Solid Electrolytic Capacitor of Example 4>
Azelaic acid was prepared in the same manner as in Example 1 except that the amount of ammonium azelaic acid added was 0.60 mol / kg for azelaic acid and 0.60 mol / kg for ammonium ions.

<Preparation of Solid Electrolytic Capacitor of Example 5>
It was prepared in the same manner as in Example 1 except that a total of 2.8 wt% of phosphoric acid ester, p-nitrobenzoic acid, boric acid, and mannit was added as an additive for the electrolytic solution.

<Preparation of Solid Electrolytic Capacitor of Example 6>
The ammonium azelaic acid salt was designated as an ammonium adipic acid salt. The breakdown of the amount of ammonium adipic acid added was 0.06 mol / kg for adipic acid and 0.06 mol / kg for ammonium ions. Other than that, it was prepared in the same manner as in Example 1.

<Preparation of Solid Electrolytic Capacitor of Example 7>
Adipic acid was prepared in the same manner as in Example 6 except that the amount of ammonium adipate added was 0.10 mol / kg for adipic acid and 0.10 mol / kg for ammonium ions.

<Preparation of Solid Electrolytic Capacitor of Example 8>
Adipic acid was prepared in the same manner as in Example 6 except that the amount of ammonium adipic acid added was 0.16 mol / kg for adipic acid and 0.16 mol / kg for ammonium ions.

<Preparation of Solid Electrolytic Capacitor of Example 9>
The preparation was carried out in the same manner as in Example 6 except that the addition amount of the ammonium adipic acid salt was 0.20 mol / kg for adipic acid and 0.20 mol / kg for ammonium ions.

<Preparation of Solid Electrolytic Capacitor of Example 10>
The ammonium azelaic acid salt was designated as an ammonium 1,6-decandicarboxylic acid salt. The breakdown of the amount of 1,6-decandicarboxylic acid ammonium salt added was 0.09 mol / kg for 1,6-decandicarboxylic acid and 0.09 mol / kg for ammonium ions. Other than that, it was prepared in the same manner as in Example 1. The rated capacity of this solid electrolytic capacitor is 22 μF.

<Preparation of Solid Electrolytic Capacitor of Example 11>
Amseline acid ammonium salt, 1,7-octanedicarboxylic acid ammonium salt, 7-methyl-7-methoxycarbonyl-1,9-decandicarboxylic acid ammonium salt, 7,9-dimethyl-7,9-dimethoxycarbonyl-1, The 11-dodecanedicarboxylic acid ammonium salt and the 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid ammonium salt were used. The breakdown of the amount of solute added is 0.05 mol / kg for 1,7-octanedicarboxylic acid, 0.01 mol / kg for 7-methyl-7-methoxycarbonyl-1,9-decandicarboxylic acid, and 7,9-dimethyl. -7,9-dimethoxycarbonyl-1,11-dodecanedicarboxylic acid 0.01 mol / kg, 7,8-dimethyl-7,8-dimethoxycarbonyl-1,14-tetradecanedicarboxylic acid 0.02 mol / kg, ammonium The ion was 0.09 mol / kg. Other than that, it was prepared in the same manner as in Example 1. The rated capacity of this solid electrolytic capacitor is 22 μF.

<Manufacturing of Solid Electrolytic Capacitor of Comparative Example 1>
The ammonium azelaic acid salt was used as a triethylamine phthalate salt. The breakdown of the amount of triethylamine phthalate added was 0.60 mol / kg for phthalic acid and 0.47 mol / kg for triethylamine. Other than that, it was prepared in the same manner as in Example 1.

<Manufacturing of Solid Electrolytic Capacitor of Comparative Example 2>
The ammonium azelaic acid salt was used as a triethylamine azelaic acid salt. The breakdown of the amount of azelaic acid triethylamine salt added was 0.60 mol / kg for azelaic acid and 0.47 mol / kg for triethylamine. Other than that, it was prepared in the same manner as in Example 1.

<Manufacturing of Solid Electrolytic Capacitor of Comparative Example 3>
Azelaic acid was prepared in the same manner as in Example 1 except that the amount of ammonium salt added was 0.81 mol / kg for azelaic acid and 0.81 mol / kg for ammonium ions.

Table 1 shows the results of applying a voltage to the solid electrolytic capacitor produced as described above and confirming whether the voltage rises to the withstand voltage of the dielectric film required for the 80 WV solid electrolytic capacitor. In Table 1, the circle marks are solid electrolytic capacitors whose voltage has risen to the withstand voltage of the electrode foil film. Further, the cross mark is a solid electrolytic capacitor shorted without the voltage rising to the film withstand voltage of the electrode foil.

As is clear from Table 1, Examples 1 to 5 using azelaic acid, Examples 6 to 9 using adipic acid, Example 10 using 1,6-decanedicarboxylic acid, and a plurality of aliphatic carboxylic acids. In all of Examples 11 using the mixed solute of the acid, the voltage increased to the film pressure resistance of the electrode foil. Further, similarly to Examples 1 to 11, the voltage of Comparative Examples 2 and 3 using the aliphatic carboxylic acid increased to the pressure resistance of the electrode foil film. However, in Comparative Example 1 in which phthalic acid, which is an aromatic carboxylic acid, was used, the voltage did not rise to the film withstand voltage of the electrode foil and short-circuited.

(2) Withstand voltage test of solid electrolytic capacitor (rated voltage 100WV)
Next, in order to perform a withstand voltage test of a solid electrolytic capacitor having a rated voltage of 100 WV, the following solid electrolytic capacitor was further manufactured.

<Preparation of Solid Electrolytic Capacitor of Example 12>
It was produced in the same manner as in Example 4 except that the rated capacity of the solid electrolytic capacitor was set to 18 μF.

<Preparation of Solid Electrolytic Capacitor of Example 13>
The ammonium azelaic acid salt was designated as an ammonium adipic acid salt. The breakdown of the amount of ammonium adipic acid added was 0.60 mol / kg for adipic acid and 0.60 mol / kg for ammonium ions. Other than that, it was prepared in the same manner as in Example 12.

Table 2 shows the results of applying a voltage to the solid electrolytic capacitor produced as described above and confirming whether the voltage rises to the withstand voltage of the dielectric film required for the solid electrolytic capacitor of 100 WV. In Table 2, the circle marks are solid electrolytic capacitors whose voltage has risen to the withstand voltage of the electrode foil film. Further, the cross mark is a solid electrolytic capacitor shorted without the voltage rising to the film withstand voltage of the electrode foil.

As is clear from Table 2, in the withstand voltage test of 100 WV, in Example 12 using azelaic acid, the voltage increased to the film withstand voltage of the electrode foil. On the other hand, in Example 13 using adipic acid, the voltage did not rise to the withstand voltage of the electrode foil film and short-circuited. In the solid electrolytic capacitor using adipic acid, the voltage increased to the film withstand voltage in the withstand voltage test of 80 WV, but the voltage did not increase at 100 WV and short-circuited. This is considered to be due to the molecular weight of adipic acid being 146.1. The molecular weight of azelaic acid, which was good even in the pressure resistance test of 100 WV, is 188.22. Therefore, it can be seen that as the molecular weight of the aliphatic carboxylic acid increases, the withstand voltage characteristic of the solid electrolytic capacitor improves. In particular, it was found that the pressure resistance characteristic was improved when the molecular weight was 150 or more.

(3) Capacitor Characteristics after Initial and Load Test The initial ESR and dielectric loss (tan δ) of the solid electrolytic capacitors of Examples 1 to 11 and Comparative Examples 2 and 3 were measured. The dielectric loss shows a value at 120 kHz (20 ° C.), and the ESR characteristic shows a value at 100 kHz (20 ° C.). Further, as described above, the volumes of Examples 1 to 9 and Comparative Examples 2 and 3 are 39 μF, and the volumes of Examples 10 and 11 are 22 μF.

Further, each solid electrolytic capacitor was subjected to a high temperature load test at a rated voltage of 80 WV at 125 ° C., and the ESR change rate (ΔESR) and the dielectric loss change rate (Δtanδ) after 500 hours and 1500 hours were calculated. Table 3 shows the results after 500 hours have passed.

As is clear from Table 3, in the results after 500 hours of the load test, the ESR change rate and the dielectric loss change rate were the lowest values in Example 5 in which boric acid and mannitol were added. From Examples 1 to 4, it was found that the rate of change in dielectric loss and the rate of change in ESR increased as the amount of acid added to the solute increased. Further, in Comparative Example 3 in which 0.81 mol / kg of azelaic acid was added, the rate of change in ESR was high. On the other hand, in Examples 1 to 11 and Comparative Example 2 in which the amount of solute acid added was 0.6 mol / kg or less, the ESR change rate was smaller than that in Comparative Example 3.

Next, Table 4 shows the results after 1500 hours have passed.

As is clear from Table 4, even in the results after 1500 hours of the load test, the rate of change in ESR and the dielectric loss in Example 5 to which boric acid and mannitol were added were compared with those in other Examples and Comparative Examples. The rate of change was the lowest. Furthermore, from Examples 1 to 4, it was found that the rate of change in dielectric loss and the rate of change in ESR increased as the amount of solute acid added increased. Further, in Comparative Example 2 in which the ammonium salt of the aliphatic carboxylic acid was not used and the triethylamine salt was used, the values of the rate of change in dielectric loss and the rate of change in ESR were remarkably increased. On the other hand, in Examples 1 to 9 using the ammonium salt of the aliphatic carboxylic acid, the ESR change rate and the dielectric loss change rate were smaller than those in Comparative Example 2.

Further, in Comparative Example 3 in which 0.81 mol / kg of azelaic acid was added, the rate of change in dielectric loss was high in addition to the rate of change in ESR. On the other hand, in Examples 1 to 9 in which the ammonium salt of the aliphatic carboxylic acid was added and the amount of the solute acid added was 0.6 mol / kg or less, the ESR change rate and the dielectric loss change rate were higher than those in Comparative Example 3. It became a small value.

1 Anode foil 2 Cathode foil 3 Separator 4, 5 Lead wire 10 Capacitor element

Claims (5)

The anode foil and the cathode foil have a condenser element wound around the separator.
The capacitor element has a solid electrolyte layer containing a conductive polymer and has a solid electrolyte layer.
The voids in the capacitor element are filled with an electrolytic solution, and the space is filled with an electrolytic solution.
The electrolytic solution contains an ammonium salt of an aliphatic carboxylic acid as a solute and a polyhydric alcohol as a solvent.
Addition amount 0.6 mol / kg der following acids of the solute in front Symbol solvent is,
The electrolyte solution, the solid electrolytic capacitor, wherein the electrolyte der Rukoto without addition of water as the solvent. The solid electrolytic capacitor according to claim 1, wherein the multivalent alcohol is ethylene glycol. The solid electrolytic capacitor according to claim 1 or 2 , wherein the electrolytic solution further contains boric acid and mannitol. The solid electrolytic capacitor according to any one of claims 1 to 3, wherein the amount of water contained in the solid electrolytic capacitor is 3 wt% or less. A process of forming a capacitor element in which an anode foil and a cathode foil are wound via a separator, and
A step of immersing the capacitor element in a dispersion of a conductive polymer and then drying it to form a solid electrolyte layer containing the conductive polymer.
The capacitor element wherein the solid electrolyte layer is formed, and ammonium salts of fat aliphatic carboxylic acids, viewed contains a polyhydric alcohol as a solvent, and the aqueous was immersed not in an electrolytic solution added as a solvent, in the capacitor element The process of filling the voids with the electrolyte and
Including
A method for producing a solid electrolytic capacitor, characterized in that the amount of the acid of the solute added to the solvent is 0.6 mol / kg or less.

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