JP2007095815A - Solid electrolytic capacitor element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize efficient suppression of defects of a dielectric oxide film which has been difficult in a conventional method, thereby efficiently providing a solid electrolytic capacitor having excellent quality in a manufacturing method of a solid electrolytic capacitor element. <P>SOLUTION: A method of manufacturing a solid electrolytic capacitor element has processes of forming a solid electrolytic layer on a valve action metal base material having an oxide film by chemical polymerization, and then, cleaning the solid electrolytic layer. In this method, a leaving process of 0.1-48 hours is provided before the cleaning process after a final process of forming the solid electrolytic layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a solid electrolytic capacitor element, a solid electrolytic capacitor element produced by the method, and a solid electrolytic capacitor using the same. In particular, the present invention relates to a method for producing a solid electrolytic capacitor element having a solid electrolyte layer by a chemical polymerization method, a solid electrolytic capacitor element produced by the method, and a solid electrolytic capacitor using the same.

  As shown in FIG. 1, a basic element of a solid electrolytic capacitor is generally formed by forming a dielectric oxide film layer (2) on an anode substrate (1) made of a metal foil having a large specific surface area that has been subjected to etching treatment. A solid semiconductor layer (hereinafter referred to as a solid electrolyte) (3) is formed as an opposing electrode, and a conductor layer (4) such as a conductive paste is preferably formed. Preferably, the anode part made of the anode base and the cathode part made of the solid electrolyte and the conductor layer are separated by the masking material (5). Such an element (6) is singly or laminated (FIG. 2), the lead wires (7, 8) are joined, and the whole is completely sealed with an epoxy resin (9) etc. Used in products.

  In recent years, with the digitization of electrical equipment and the speeding up of personal computers, small and large-capacitance capacitors and low-impedance capacitors in the high-frequency region are required. Recently, it has been proposed to use a conductive polymer having electronic conductivity as a solid electrolyte.

  In general, an electrolytic oxidation polymerization method or a chemical oxidation polymerization method is known as a method for forming a conductive polymer on a dielectric oxide film. Among these, the chemical polymerization methods (Patent Document 1: Japanese Patent No. 3187380, Patent Document 2: Japanese Patent Laid-Open No. 2003-188052, etc.) have a simple solid electrolyte forming operation, and a large amount of solid electrolysis in a short time. Since the capacitor element can be manufactured, it is economical. However, when there is a defect in the dielectric oxide film, the chemical polymerization film may directly contact the metal in the defective portion, which may cause problems such as an increase in leakage current (LC) in the capacitor product.

  In addition, various improved methods have been proposed for the formation of a chemically polymerized film (Patent Document 3: Japanese Patent Laid-Open No. 11-251193, Patent Document 4: Japanese Patent Laid-Open No. 2000-21686, etc.). Even if the film formation conditions were changed variously, there was a limit in improving the product quality or the yield.

Japanese Patent No. 3187380 JP 2003-188052 A Japanese Patent Laid-Open No. 11-251193 JP 2000-21686 A

  An object of the present invention is to effectively suppress the formation of defects in an oxide film in a method for producing a solid electrolytic capacitor element, thereby efficiently providing a solid electrolytic capacitor having excellent quality.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made a remarkable improvement in product quality by providing a certain amount of standing time instead of performing cleaning immediately after formation of the solid electrolyte layer by the chemical polymerization method. Alternatively, the present inventors have found that it is possible to efficiently sort out inappropriate products and improve product yield, and the present invention has been completed.
That is, according to the present invention, the following method for producing a solid electrolytic capacitor element, a solid electrolytic capacitor element, and a solid electrolytic capacitor using the same are provided.

1. In the method of manufacturing a solid electrolytic capacitor element, which includes a step of cleaning the solid electrolyte layer after forming the solid electrolyte layer by chemical polymerization on the valve metal substrate having an oxide film, the final step of forming the solid electrolyte layer Thereafter, a method for producing a solid electrolytic capacitor element is provided, wherein a standing step of 0.1 to 48 hours is provided before the cleaning step.
2. 2. The method for producing a solid electrolytic capacitor element as described in 1 above, wherein the valve metal substrate has a porous layer on the surface.
3. 3. The method for producing a solid electrolytic capacitor element as described in 1 or 2 above, wherein the valve metal substrate is aluminum.
4). 4. The method for producing a solid electrolytic capacitor element as described in any one of 1 to 3, wherein the washing is performed with an aqueous medium.
5. 5. The method for producing a solid electrolytic capacitor element as described in any one of 1 to 4 above, wherein the aqueous medium is warm water having a boiling point of 20 ° C. or higher and a boiling point or lower.
6). The step of forming a solid electrolyte layer by chemical polymerization on a valve action metal substrate having an oxide film is a step of attaching a polymerizable compound to the surface of the substrate and then causing an oxidant to act to perform chemical polymerization. The manufacturing method of the solid electrolytic capacitor element in any one of 1-5.
7). The step of forming a solid electrolyte layer by chemical polymerization on a valve action metal substrate having an oxide film is a step of attaching an oxidizing agent to the surface of the substrate and then allowing a polymerizable compound to act to perform chemical polymerization. The manufacturing method of the solid electrolytic capacitor element in any one of 1-5.
8). 8. The method for producing a solid electrolytic capacitor element according to 6 or 7, wherein the step 6 or 7 is repeated a plurality of times to form a solid electrolyte layer.
9. The solid electrolytic capacitor element manufactured by the manufacturing method of the solid electrolytic capacitor element in any one of said 1-8.
10. 10. A solid electrolytic capacitor using the solid electrolytic capacitor element as described in 9 above.
11. 10. A multilayer solid electrolytic capacitor obtained by laminating the solid electrolytic capacitor elements described in 9 above.

  ADVANTAGE OF THE INVENTION According to this invention, the defect of a dielectric oxide film can be suppressed effectively, an electrical property is improved, and the improvement of a product yield is implement | achieved. In addition, as a result of the polymerization of the monomer and the oxidizing agent introduced in the latter stage of the polymerization process more effectively, the use efficiency of the monomer is increased.

Hereinafter, the manufacturing method of the solid electrolytic capacitor element of the present invention will be described.
As described above, in the present invention, after the solid electrolyte layer is formed, the solid electrolyte layer is washed after being allowed to stand for 0.1 to 48 hours, more preferably 1 to 30 hours before washing. It is characterized by.
The reason why the product quality is improved by the present invention is not clear in detail, but by providing a standing step after forming the solid electrolyte layer, the oxidizing agent, unreacted monomer, oligomer, etc. contained in the solid electrolyte layer are polymerized. However, it is thought that defects in the oxide film are suppressed by covering a stronger film. On the other hand, if the standing time is set excessively, the drying proceeds with the oxidant solution, and as a result, the concentration of the oxidant or its derivative increases in the solid electrolyte layer or in the vicinity of the interface between the solid electrolyte layer and the oxide film layer, As a result, it is considered that the acidic film is damaged by acidity (for example, about pH 2) that cannot be sufficiently repaired in the subsequent process. However, this is a mechanism estimated from the effects of the present invention, and the present invention is not limited to this mechanism. In any case, by allowing the substrate to stand for a time within the above range, it is possible to simultaneously achieve the formation of a good solid electrolyte layer and the suppression of defects in the oxide film.

The leaving step in the present invention may be left as it is, and does not require any special operation, but preferably has a relative humidity of 20 to 80%, more preferably about 30 to 70%, and a temperature of 20 to 60. It is allowed to stand in an environment of ° C, more preferably 30-50 ° C.
The polymerization performed before standing is performed by attaching a polymerizable compound to the substrate surface and then allowing an oxidizing agent to act, or by attaching an oxidizing agent-containing liquid to the substrate surface and then allowing the polymerizable compound to act. Do. Any of these steps may be repeated a plurality of times, or in some cases in combination. In the present invention, the type of the polymerizable compound and the oxidizing agent is not particularly limited, but suitable compounds will be described later.
For the adhesion or action of these compounds, a method by immersing the base material in a liquid containing each compound is simple and desirable, but spraying, coating and other methods are also possible. In the present invention, the “final step of forming a solid electrolyte layer in the production method” refers to a step of finally attaching a solution or suspension containing a polymerizable compound or an oxidizing agent.
Although the washing conditions performed after being left are not particularly limited, warm water washing is preferable. The temperature of warm water used for warm water cleaning is 20 ° C. or higher, preferably 30 ° C. or higher, more preferably 40 ° C. or higher. The upper limit of temperature is not specifically limited, What is necessary is just to be below a boiling point. In the present invention, the temperature range is preferably 20 to 60 ° C.

  The cleaning may be spray cleaning as long as it has a cleaning effect on the solid electrolyte layer, but shower cleaning or cleaning by immersion is preferable. The immersion may be performed only once, or may be performed a plurality of times by changing the liquid. The washing (immersion) time is usually 1 minute or longer, preferably 2 minutes or longer, more preferably 3 minutes or longer. Although depending on the cleaning (immersion) temperature, the effect is more noticeable by continuing for a long time. However, even if it continues for an excessively long time, the effect is saturated and the production efficiency is lowered. For this reason, it is usually 10 hours or less, preferably 5 hours or less, more preferably 3 hours or less. Typically, the treatment is performed for about 10 minutes to 2 hours. It is preferable to use high purity water for the final cleaning.

The solid electrolytic capacitor element obtained as described above can be further dried as necessary, and used for the production of a solid electrolytic capacitor according to a conventional method. Accordingly, the present invention provides a solid electrolytic capacitor element manufactured by the above method for manufacturing a solid electrolytic capacitor element, a solid electrolytic capacitor using the solid electrolytic capacitor element, and a stacked solid electrolytic capacitor formed by stacking solid electrolytic capacitor elements including.
The solid electrolytic capacitor element material may be any material in which a solid electrolyte layer is formed by chemical polymerization on a metal substrate having an oxide film. Details are as follows.

  That is, the solid electrolytic capacitor element material is preferably based on a valve action metal having a porous layer on the surface. The valve action metal having such a porous layer is not particularly limited as long as it can be suitably used in a solid electrolytic capacitor. For example, the valve action metal is aluminum, tantalum, niobium, titanium, zirconium, or these as a substrate. It is selected from metals having an alloy-based valve action. Or it selects from the sintered compact etc. which have these as a main component. The shape is not particularly limited, and examples thereof include a thin plate, a foil, and a rod, and a thin plate or a foil is particularly preferable. These metals have a dielectric oxide film as a result of oxidation of the surface by oxygen in the air, but usually a roughening treatment and a chemical conversion treatment were performed to form a dielectric oxide film on the surface. Is.

As the metal base material having a valve action, it is preferable to use a metal base material that has been cut into a size that matches the shape of the solid electrolytic capacitor after roughening.
The dimension of the metal having a valve action may vary depending on the purpose of use. For example, a thin plate or foil generally has a thickness of about 40 to 150 μm. Further, although the shape varies depending on the application, a rectangular element having a width of about 1 to 50 mm and a length of about 1 to 50 mm is preferable as a flat element unit, more preferably about 2 to 20 mm in width and about 2 to 20 mm in length. The width is preferably about 2 to 5 mm and the length is about 2 to 6 mm.

As the solid electrolyte, there is a conductive polymer containing as a repeating unit a structure represented by a compound having a thiophene skeleton, a compound having a polycyclic sulfide skeleton, a compound having a pyrrole skeleton, a compound having a furan skeleton, a compound having an aniline skeleton, etc. Can be mentioned.
Examples of the compound having a thiophene skeleton include 3-methylthiophene, 3-ethyloffene, 3-propylthiophene, 3-butylthiophene, 3-pentylthiophene, 3-hexylthiophene, 3-heptylthiophene, 3-octylthiophene, 3- Nonylthiophene, 3-decylthiophene, 3-fluorothiophene, 3-chlorothiophene, 3-bromothiophene, 3-cyanothiophene, 3,4-dimethylthiophene, 3,4-diethylthiophene, 3,4-butylenethiophene, 3 , 4-methylenedioxythiophene, 3,4-ethylenedioxythiophene and the like. These compounds can be generally prepared by commercially available compounds or by known methods (for example, Synthetic Metals, 1986, Vol. 15, p. 169), but the present invention is not limited thereto.

  In addition, for example, as a compound having a polycyclic sulfide skeleton, specifically, a compound having a 1,3-dihydropolycyclic sulfide (also known as 1,3-dihydrobenzo [c] thiophene) skeleton, 1,3-dihydro A compound having a naphtho [2,3-c] thiophene skeleton can be used. Furthermore, a compound having a 1,3-dihydroanthra [2,3-c] thiophene skeleton and a compound having a 1,3-dihydronaphthaceno [2,3-c] thiophene skeleton can be exemplified, and a known method, For example, it can be prepared by the method described in JP-A-8-3156.

  In addition, for example, a compound having a 1,3-dihydronaphtho [1,2-c] thiophene skeleton is a 1,3-dihydrophenanthra [2,3-c] thiophene derivative or 1,3-dihydrotriphenylo. The compound having a [2,3-c] thiophene skeleton may be a 1,3-dihydrobenzo [a] anthraceno [7,8-c] thiophene derivative.

  The condensed ring may optionally contain nitrogen or N-oxide, such as 1,3-dihydrothieno [3,4-b] quinoxaline and 1,3-dihydrothieno [3,4-b] quinoxaline-4-oxide 1,3-dihydrothieno [3,4-b] quinoxaline-4,9-dioxide, and the like, but are not limited thereto.

  Examples of the compound having a pyrrole skeleton include 3-methylpyrrole, 3-ethylpyrrole, 3-propylpyrrole, 3-butylpyrrole, 3-pentylpyrrole, 3-hexylpyrrole, 3-heptylpyrrole, 3-octylpyrrole, 3-nonylpyrrole, 3-decylpyrrole, 3-fluoropyrrole, 3-chloropyrrole, 3-bromopyrrole, 3-cyanopyrrole, 3,4-dimethylpyrrole, 3,4-diethylpyrrole, 3,4-butylenepyrrole , Derivatives of 3,4-methylenedioxypyrrole, 3,4-ethylenedioxypyrrole, and the like.

  Examples of the compound having a furan skeleton include 3-methyl furan, 3-ethyl furan, 3-propyl furan, 3-butyl furan, 3-pentyl furan, 3-hexyl furan, 3-heptyl furan, 3-octyl furan, 3-nonylfuran, 3-decylfuran, 3-fluorofuran, 3-chlorofuran, 3-bromofuran, 3-cyanofuran, 3,4-dimethylfuran, 3,4-diethylfuran, 3,4-butylenefuran, 3,4 -Derivatives such as methylenedioxyfuran and 3,4-ethylenedioxyfuran can be mentioned.

Examples of the compound having an aniline skeleton include 2-methylaniline, 2-ethylaniline, 2-propylaniline, 2-butylaniline, 2-pentylaniline, 2-hexylaniline, 2-heptylaniline, 2-octylaniline, 2-nonylaniline, 2-decylaniline, 2-fluoroaniline, 2-chloroaniline, 2-bromoaniline, 2-cyanoaniline, 2,5-dimethylaniline, 2,5-diethylaniline, 3,4-butyleneaniline , Derivatives of 3,4-methylenedioxyaniline, 3,4-ethylenedioxyaniline, and the like.
These compounds can be obtained commercially or by known methods. In addition, the above is an illustration and the conductive polymer which forms a solid electrolyte in this invention is not restricted to this.

  Moreover, you may use the compound chosen from the said compound group together, and may use it as a ternary system copolymer. In this case, the composition ratio of the polymerizable monomer depends on the polymerization conditions, and the preferred composition ratio and polymerization conditions can be confirmed by a simple test.

The monomer is oxidatively polymerized, for example, by bringing it into contact with an oxidant on a metal substrate having an oxide film to obtain a solid electrolyte. The oxidizing agent used for the production of the conductive polymer used as the solid electrolyte may be any oxidizing agent that can sufficiently perform the oxidation reaction or the two-electron oxidation reaction of the four-electron oxidation reaction accompanied by dehydrogenation. Specifically, a compound that is industrially inexpensive and easy to handle in production is preferred. Specifically, for example, FeCl ₃ , FeClO ₄ , Fe (III) -based compounds such as Fe (organic acid anion) salt, anhydrous aluminum chloride / cuprous chloride, alkali metal persulfates, ammonium persulfates, peroxidation Products, manganese such as potassium permanganate, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetrachloro-1,4-benzoquinone, tetracyano-1,4-benzoquinone, etc. Quinones, halogens such as iodine and bromine, peracid, sulfuric acid, fuming sulfuric acid, sulfur trioxide, sulfonic acid such as chlorosulfuric acid, fluorosulfuric acid and amidosulfuric acid, ozone and the like, and combinations of these oxidizing agents. .

For example, the solid electrolytic capacitor element is provided with a conductor layer and electrodes as shown in FIG. Alternatively, the resin sealing is performed after laminating by a conventional mode and method.
Further, for example, as shown in FIG. 2, each cathode part (solid electrolyte layer) and the anode part are laminated so as to overlap each other, and the whole is sealed with resin. A solid electrolytic capacitor element having a cathode part and an anode part is laminated on a lead frame corresponding to the cathode and anode so that the cathode and anode correspond to each other and the anode part and cathode part correspond to each other, and the whole is sealed with resin. Also good.
The sealant is not particularly limited, and examples thereof include an insulating resin such as an epoxy resin.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, these are illustrations and this invention is not limited to these examples.
Example 1
A 110 mm thick conversion aluminum foil (3V conversion product) cut to 3.5 mm width was cut to a length of 13 mm, and one short side of this foil piece was fixed to a metal guide by welding. In order to form a cut surface, a polyimide resin solution (manufactured by Ube Industries) was drawn in a line shape of 0.8 mm width at a location 7 mm from the unfixed end and dried at about 180 ° C. for 30 minutes. The portion from the tip of the unfixed aluminum foil to the applied polyimide resin is used as the first chemical conversion (cutting chemical conversion) in a 5% by mass aqueous oxalic acid solution at a current density of 5 mA / cm ² , a chemical conversion voltage of 3 V, and a temperature of 25 ° C. After chemical conversion treatment for 2 minutes, it was washed with water and dried.
Next, as a second chemical conversion step, chemical conversion was carried out in a 1% by mass sodium silicate aqueous solution at a current density of 1 mA / cm ² , a chemical conversion voltage of 3 V, and a temperature of 65 ° C. for 7 minutes, followed by washing with water and drying. Then, 300 degreeC heat processing was performed for 30 minutes.
Further, as a third chemical conversion, a chemical conversion treatment was performed in a 9% by mass ammonium adipate aqueous solution at a current density of 3 mA / cm ² , a chemical conversion voltage of 3 V, and a temperature of 65 ° C. for 10 minutes, followed by washing with water and drying.

Next, a polyimide resin for separating the anode part and the cathode part was applied linearly to a width of 0.8 mm centering on a part 5 mm from the tip of the aluminum foil, and dried at 180 ° C. for 1 hour. A solid electrolyte as a cathode layer was formed as follows.
That is, the cathode part (3.5 mm × 4.6 mm) was immersed in an isopropanol solution (solution 1) containing 3,4-ethylenedioxythiophene, pulled up and left to stand. Next, it was immersed in an aqueous solution containing ammonium persulfate (solution 2), dried, and subjected to oxidative polymerization. The operation of immersing in solution 1 and then immersing in solution 2 and performing oxidative polymerization was repeated.
After standing at room temperature for 3 hours, it was washed with warm water at 50 ° C. and dried at 100 ° C. to form a solid electrolyte layer. Further, an electrode was formed with a carbon paste and a silver paste at the cathode portion, thereby completing a capacitor element.

Two parts, including the applied masking material, are overlapped on the lead frame while being joined with Ag paste, and the anode lead terminal is connected to the part without the solid electrolyte by welding, and the whole is sealed with epoxy resin, at 135 ° C. A total of 30 chip-type solid electrolytic capacitors were produced by applying a voltage of 2 V and aging.
For these 30 capacitors, the initial characteristics were measured for capacity and loss factor (tan δ) at 120 Hz, equivalent series resistance (hereinafter referred to as ESR) at 100 kHz, and leakage current. The leakage current was measured 1 minute after applying the rated voltage of 16V. The measurement results were as follows.

Capacity (average value): 94.2 μF
tan δ (average value): 1.2%
ESR (average value): 11.4 mΩ
Leakage current (average value): 0.27 μA
The defective rate when a leakage current of 1 μA (0.005 CV) or more was regarded as a defective product was 5%.
Further, the results of a reflow test and a subsequent moisture resistance test are shown. The reflow test (also called solder heat resistance test) was evaluated by the following method. That is, 20 capacitor elements were prepared, and the elements were passed for 10 seconds at a temperature of 255 ° C., this operation was repeated three times, the leakage current after 1 minute application of the rated voltage was measured, and the value was 8 μA ( 0.04 CV) or higher was regarded as defective. The moisture resistance test was left for 500 hours in a high temperature and high humidity environment of 60 ° C. and 90% RH, and a leakage current value of 80 μA (0.4 CV) or higher after 1 minute application of the rated voltage was regarded as a defective product.

Leakage current after reflow test: 0.35 μA
Leakage current after moisture resistance test: 12.6 μA
In all cases, the defect rate was zero.

Example 2
A capacitor was produced and evaluated in the same manner as in Example 1 except that the time of standing at room temperature was 45 hours.

Comparative Example 1
A capacitor was produced and evaluated in the same manner as in Example 1 except that the standing time was 50 hours.

Comparative Example 2
A capacitor was produced and evaluated in the same manner as in Example 1 except that the standing time was 0 hour.
The results of these Examples and Comparative Examples are shown in Tables 1 and 2 together with the results of other examples.

  According to the present invention, the polymerization of the monomer and the oxidizing agent introduced in the latter stage of the polymerization process proceeds more favorably, the use efficiency of the monomer is increased, and the yield can be improved. Therefore, the present invention is effective as a solid electrolytic capacitor element that realizes an improvement in product quality and an improvement in product yield over a wide range of withstand voltages ranging from low to high, and a method for manufacturing a solid electrolytic capacitor using the same.

It is a typical sectional view of a general solid electrolytic capacitor element. It is typical sectional drawing which shows the state which laminated | stacked the solid electrolytic capacitor element according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode base body 2 Oxide film layer 3 Solid electrolyte layer 4 Conductor 5 Masking material 6 Solid electrolytic capacitor 7 Anode lead 8 Cathode lead 9 Sealing material

Claims (11)

  In the method of manufacturing a solid electrolytic capacitor element, which includes a step of cleaning the solid electrolyte layer after forming the solid electrolyte layer by chemical polymerization on the valve metal substrate having an oxide film, the final step of forming the solid electrolyte layer Thereafter, a method for producing a solid electrolytic capacitor element is provided, wherein a standing step of 0.1 to 48 hours is provided before the cleaning step.   The method for producing a solid electrolytic capacitor element according to claim 1, wherein the valve metal substrate has a porous layer on the surface.   The method for producing a solid electrolytic capacitor element according to claim 1 or 2, wherein the valve metal substrate is aluminum.   The method for producing a solid electrolytic capacitor element according to any one of claims 1 to 3, wherein cleaning is performed with an aqueous medium.   The method for producing a solid electrolytic capacitor element according to claim 1, wherein the aqueous medium is warm water having a boiling point of 20 ° C. or higher and a boiling point or lower.   The step of forming a solid electrolyte layer by chemical polymerization on a valve-acting metal substrate having an oxide film is a step of attaching a polymerizable compound to the surface of the substrate and then allowing an oxidant to act to perform chemical polymerization. Item 6. A method for producing a solid electrolytic capacitor element according to any one of Items 1 to 5.   The step of forming a solid electrolyte layer by chemical polymerization on a valve metal substrate having an oxide film is a step of attaching an oxidizing agent to the surface of the base material and then allowing a polymerizable compound to act to perform chemical polymerization. Item 6. A method for producing a solid electrolytic capacitor element according to any one of Items 1 to 5.   The method for producing a solid electrolytic capacitor element according to claim 6 or 7, wherein the step of claim 6 or 7 is repeated a plurality of times to form a solid electrolyte layer.   The solid electrolytic capacitor element manufactured by the manufacturing method of the solid electrolytic capacitor element in any one of Claims 1-8.   A solid electrolytic capacitor using the solid electrolytic capacitor element according to claim 9. A multilayer solid electrolytic capacitor obtained by laminating the solid electrolytic capacitor element according to claim 9.

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