JP5289016B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

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

  A conventional solid electrolytic capacitor shown in FIGS. 1 and 2 is known (Patent Document 1).

  As shown in the sectional view of FIG. 1, the solid electrolytic capacitor 1 includes a capacitor element 6 having lead wires 8 </ b> A and 8 </ b> B, a bottomed case 9 that houses the capacitor element 6, and a seal that seals the capacitor element 6. A member 10 is provided. The vicinity of the open end of the bottomed case 9 is subjected to lateral drawing and curling.

  As shown in the perspective view of FIG. 2, the capacitor element 6 is wound around a pair of electrode foils composed of an anode body 2 and a cathode body 3 having a dielectric film formed on the surface thereof, and a separator 12 to prevent winding. It is formed by being stopped with a tape 5. The anode lead wire 8A is connected to the anode body 2 via the anode lead tab 7A, and the cathode lead wire 8B is connected to the cathode body 3 via the cathode lead tab 7B.

  As the electrolyte of the solid electrolytic capacitor 1 having such a structure, a solid electrolyte made of a conductive polymer or the like is used, and the gap between the electrode foils 2 and 3 of the capacitor element 6 is filled.

  With the recent digitalization of electronic devices, the above-described solid electrolytic capacitors are also required to be reduced in size, increased in capacity, and reduced in ESR. Here, ESR means equivalent series resistance.

Furthermore, in the field of in-vehicle equipment and industrial equipment where the usage environment is severe, there is an increasing demand for higher withstand voltage of solid electrolytic capacitors. Conventionally, as means for increasing the withstand voltage of a solid electrolytic capacitor, there is a method of increasing the withstand voltage of the dielectric film by increasing the formation voltage in the chemical conversion treatment when forming the dielectric film on the surface of the anode body. However, when the formation voltage is increased, there are problems such as a decrease in leakage current characteristics and occurrence of a short circuit failure.
JP-A-2-15611

  The present invention provides a method for manufacturing a solid electrolytic capacitor, which can increase a breakdown voltage while preventing deterioration of leakage current characteristics and occurrence of a short circuit failure in a solid electrolytic capacitor using a conductive polymer as a solid electrolyte. .

The present invention relates to a method of manufacturing a solid electrolytic capacitor including a capacitor element having an anode body having a dielectric film formed on a surface and a solid electrolyte made of a conductive polymer, and the dielectric film is formed on the surface. A first step of forming a capacitor element having an anode body, a second step of impregnating the capacitor element with a polymer solution containing a precursor monomer of a conductive polymer and an oxidizing agent, and a silane compound or a silane compound solution. A solid electrolytic capacitor manufacturing method comprising: a third step of impregnating the capacitor element; and a fourth step of forming a conductive polymer in the capacitor element by chemical polymerization.

  Furthermore, it is preferable that the said silane compound solution consists of a silane compound and an organic solvent, and the density | concentration of the silane compound in a silane compound solution is 10 to 100 weight% or more.

  Furthermore, the organic solvent is preferably an organic solvent of alcohols, hydrocarbons, esters and ketones.

  According to the present invention, a solid electrolytic capacitor using a conductive polymer as a solid electrolyte has a high withstand voltage characteristic, and a highly reliable solid electrolytic capacitor in which leakage current and occurrence of a short circuit failure are suppressed is provided.

  The best mode for carrying out the present invention will be described below.

  FIG. 1 is a front sectional view of a solid electrolytic capacitor of the present invention, and FIG. 2 is a perspective view of a capacitor element of the solid electrolytic capacitor of the present invention.

  The solid electrolytic capacitor 1 of the present invention includes a capacitor element 6, lead tabs 7 </ b> A and 7 </ b> B, lead wires 8 </ b> A and 8 </ b> B, a bottomed case 9, a sealing member 10, and a seat plate 11. The capacitor element 6 includes an anode body 2 connected to an anode lead tab 7A, a cathode body 3 connected to a cathode lead tab 7B, and a separator 4. A dielectric film is formed on the surface of at least the anode body among the anode body and the cathode body.

  A solid electrolyte layer made of a conductive polymer is formed in the capacitor element 6. The solid electrolyte layer of the present invention is formed as follows. First, a polymerization liquid containing a monomer that becomes a conductive polymer and an oxidizing agent is prepared, and the capacitor element is impregnated with the polymerization liquid. Then, until the chemical polymerization of the polymer solution impregnated in the capacitor element is completed, the capacitor element is impregnated with a silane compound solution containing a silane compound. Thereafter, the chemical polymerization reaction of the polymerization solution impregnated in the capacitor element is completed to form a conductive polymer.

  Since the silane compound has an effect of improving the molecular weight distribution and crystallinity of the conductive polymer and strengthening the bonding of the conductive polymer chain by the crosslinking effect, the leakage current characteristic and the breakdown voltage characteristic of the solid electrolytic capacitor are improved. However, since the silane compound does not have conductivity, when the capacitor element is impregnated with the polymerization solution and chemically polymerized, the ESR of the capacitor may be increased. If the capacitor element is impregnated with the polymer solution and then chemically polymerized by impregnating the capacitor element as in the present invention, the concentration of the silane compound in the conductive polymer in the vicinity of the dielectric film can be kept low. Therefore, ESR of the capacitor can be reduced. As a result, it is possible to improve both the leakage current characteristics and the breakdown voltage characteristics of the solid electrolytic capacitor and to reduce the ESR.

  Examples of the silane compound used in the present invention include vinyl trickle silane, vinyl trimethoxy silane, vinyl triethoxy silane, β- (3,4 epoxy cyclohexyl) ethyl trimethoxy silane, γ-glycidoxypropyl trimethoxy silane, Methacryloxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, p-styryltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldi Ethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, N-2 (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) γ- Aminopropyltrimethoxysilane, N-2 (aminoethyl) γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-3aminopropyltrimethoxysilane, γ- Chloropropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane and the like are preferable, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ- More preferred are glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycidoxypropyltriethoxysilane. Further, two or more of the silane compounds may be used in combination.

  As the solvent used in the silane compound solution, volatile organic solvents such as alcohols, hydrocarbons, esters, and ketones can be used. The concentration of the silane compound in the silane compound solution is preferably 10 to 100% by weight, and may be used alone without being diluted with the solvent.

  Examples of the method for impregnating the capacitor element with the silane compound solution include a method of immersing the capacitor element in the silane compound solution, a method of applying the silane compound solution to the capacitor element, and spraying the silane compound solution on the capacitor element by spraying or the like. A method or the like can be used.

  The conductive polymer that can be used in the present invention preferably contains at least one aliphatic, aromatic, heterocyclic, and heteroatom-containing conductive polymer, and in particular, polythiophene. Of these, polyaniline-based and polypyrrole-based conductive polymers are preferable.

As the oxidizing agent, conventionally known oxidizing agents such as ferric p-toluenesulfonate can be used. The oxidizing agent can be used by being dissolved in alcohols such as methanol, ethanol and butanol, and is preferably used at a concentration of 35 to 70% by weight.
[Example 1]
First, the surface of the anode body 2 and the cathode body 3 made of aluminum foil was subjected to an etching process. Thereafter, the anode body 2 subjected to the etching treatment was immersed in a chemical conversion solution, and a dielectric film was formed by applying a voltage of 150V.

  An anode lead tab 7A and a cathode lead tab 7B were connected to the anode body 2 and the cathode body 3, respectively. And the said anode body 2 and the said cathode body 3 were wound with the separator, the outermost periphery was stopped with the winding stop tape 5, and the capacitor | condenser element 6 was produced.

  Subsequently, cut formation of the capacitor element 6 was performed. Cut formation was performed by immersing the capacitor element 6 in a chemical conversion solution and applying a voltage.

  Next, the polymerization liquid of the conductive polymer which is a solid electrolyte was adjusted. The polymerization liquid was prepared by mixing 3,4 ethylenedioxythiophene as a monomer and p-toluenesulfonic acid ferric butanol solution as an oxidizing agent. Here, the weight ratios of 3,4 ethylenedioxythiophene and the ferric butanol solution of p-toluenesulfonic acid were 25% by weight and 75% by weight, respectively.

  Then, after the capacitor element was immersed in the polymerization solution, the capacitor element was immersed in a silane compound solution. In the silane compound solution, γ-acryloxypropyltrimethoxysilane was used as the silane compound, butanol was used as the solvent, and the concentration of the silane compound was 10% by weight.

  Thereafter, the capacitor element 6 was thermochemically polymerized to form a solid electrolyte layer made of a conductive polymer inside the capacitor element 6.

Thereafter, the capacitor element 6 was housed in a bottomed case 9 and a sealing member 10 was inserted into the open end of the bottomed case 9 to perform lateral drawing and curling. Then, the seat plate 11 was inserted into the curled surface, and the lead wires 8A and 8B were pressed and bent to complete the solid electrolytic capacitor 1.
[Example 2]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the concentration of the silane compound solution was 20% by weight.
[Example 3]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the concentration of the silane compound solution was 50% by weight.
[Example 4]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the concentration of the silane compound solution was 100% by weight (used without diluting the silane compound).
[Example 5]
An electrolytic capacitor was produced in the same manner as in Example 1 except that γ-glycidoxypropyltrimethoxysilane was used as the silane compound.
[Example 6]
An electrolytic capacitor was produced in the same manner as in Example 2 except that γ-glycidoxypropyltrimethoxysilane was used as the silane compound.
[Example 7]
An electrolytic capacitor was produced in the same manner as in Example 3 except that γ-glycidoxypropyltrimethoxysilane was used as the silane compound.
[Example 8]
An electrolytic capacitor was produced in the same manner as in Example 4 except that γ-glycidoxypropyltrimethoxysilane was used as the silane compound.
[Comparative Example 1]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the concentration of the silane compound solution was 1% by weight.
[Comparative Example 2]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the concentration of the silane compound solution was changed to 5% by weight.
[Comparative Example 3]
An electrolytic capacitor was produced in the same manner as in Comparative Example 1 except that γ-glycidoxypropyltrimethoxysilane was used as the silane compound.
[Comparative Example 4]
An electrolytic capacitor was produced in the same manner as in Example 2 except that γ-glycidoxypropyltrimethoxysilane was used as the silane compound.
[Comparative Example 5]
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the capacitor element was immersed in the polymerization solution and then chemically polymerized without being immersed in the silane compound solution.

  Table 1 shows the measurement results of electrical characteristics of 20 average values for each of the solid electrolytic capacitors of the example and the comparative example. The solid electrolytic capacitor has a rated voltage of 35 V and a capacity of 22 μF, and has dimensions of 10 mm in diameter and 12 mm in height. Here, the short-circuit occurrence rate indicates the short-circuit occurrence rate after aging treatment at 125 ° C. for 5 hours. The capacitance and dielectric loss tangent were measured at a frequency of 120 Hz, and the ESR was measured at a frequency of 100 kHz. The leakage current is a value two minutes after the rated voltage is applied. The BDV value (withstand voltage characteristic) indicates a voltage at which the solid electrolytic capacitor is subjected to dielectric breakdown by boosting the applied voltage at room temperature at a rate of 1 V / s.

  From the results shown in Table 1, the solid electrolytic capacitors of the examples are improved in short-circuit occurrence rate, leakage current, and BDV value as compared with Comparative Example 5. Therefore, by immersing the capacitor element in the polymerization solution and chemical polymerization after immersing in the silane compound solution, it is possible to suppress the short-circuit occurrence rate and the leakage current and to improve the breakdown voltage characteristics.

  Further, comparing the examples and comparative examples 1 to 4, the higher the concentration of the silane compound in the silane compound solution, the more the characteristics of short-circuit occurrence rate, leakage current and BDV value are improved. This is remarkable when the content is 10% by weight or more. Therefore, by increasing the concentration of the silane compound, it is possible to further increase the effect of suppressing the short-circuit occurrence rate and the leakage current and improving the breakdown voltage characteristics.

  The above embodiments are merely illustrative of the present invention and should not be construed as limiting the invention described in the claims. The present invention can be freely modified within the scope of the claims and the scope of equivalent meanings. For example, although one embodiment of the present invention is a wound solid electrolytic capacitor, it may be a chip solid electrolytic capacitor or a stacked solid electrolytic capacitor in which a plurality of capacitor elements are stacked. In addition to aluminum, valve metals such as tantalum, niobium, and titanium may be used for the anode body.

It is sectional drawing of the solid electrolytic capacitor produced with this invention and the conventional manufacturing method. It is a perspective view of the capacitor | condenser element in the solid electrolytic capacitor produced with this invention and the conventional manufacturing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolytic capacitor 2 Anode body 3 Cathode body 4 Separator 5 Winding tape 6 Capacitor element 7 Lead tab 8 Lead wire 9 Bottomed case 10 Sealing member 11 Seat plate 12 Dielectric film 13 Conductive polymer 14 Lead frame 15 Exterior resin 16 Anode lead

Claims (2)

In a method for producing a solid electrolytic capacitor comprising a capacitor element having an anode body having a dielectric film formed on a surface and a solid electrolyte made of a conductive polymer,
First a step, a second step of impregnating a precursor monomer and the oxidizing agent of a conductive polymer prior Symbol capacitor element to form a capacitor element having an anode body with a dielectric film formed on the surface,
After the second step, a third step of impregnating the capacitor element with a silane compound or a silane compound solution;
A fourth step of forming a conductive polymer in the capacitor element by heating and promoting chemical polymerization after the third step;
Only including,
The silane compound solution consists of a silane compound and an organic solvent,
The method for producing a solid electrolytic capacitor, wherein a concentration of the silane compound in the silane compound solution is 10% by weight or more . The method for producing a solid electrolytic capacitor according to claim 1, wherein the organic solvent is an organic solvent of alcohols, hydrocarbons, esters, and ketones.