JP2007305898A - Impregnation method and impregnation apparatus of electrolyte in electrolytic capacitor manufacture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impregnation method of electrolytic capacitor electrolyte by which a dispersion of impregnation amount is small and an element is certainly impregnated. <P>SOLUTION: A method of performing an impregnation is carried out by inserting a capacitor element 3 into a case 1 filled up with electrolyte 2 of specific amount. The impregnation is performed in a process of partially immersing the capacitor element 3 in the electrolyte 2 (Drawings (d) and (e)), and a process of immersing the capacitor element 3 in the residual electrolyte 2 (Drawing (f)). In at least one of these processes there is included a pressure reduction process of decompressing a treatment atmosphere at the time of impregnating, and thereafter of returning the decompressed atmosphere to an atmospheric pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for impregnating a capacitor element with an electrolytic solution in the production of an electrolytic capacitor and an apparatus for carrying out this method.

  An electrolytic capacitor is made by etching a high-purity aluminum foil to enlarge its surface area, and anodic oxidation of the surface to form a dielectric, and an etched cathode foil disposed opposite to the anode foil. A capacitor element having a structure in which a separator (electrolytic paper, separator paper, etc.) is wound around is impregnated with an electrolytic solution and enclosed in a case.

  Since the impregnation with the electrolytic solution has a great influence on the electrical characteristics and reliability of the electrolytic capacitor to be manufactured, it is one of the most important processes in manufacturing the electrolytic capacitor. It can be said that the larger the amount of electrolyte impregnated in the capacitor element, the longer the life of the electrolytic capacitor, which is desirable. However, if the amount is too large, problems such as electrolyte leakage and expansion of the element enclosing case may occur in actual use of the manufactured capacitor. In extreme cases, a safety valve provided in advance in the element enclosing case is activated. Problem arises. In addition to the problem of variations in the impregnation amount of the electrolyte, there will be variations in the life of capacitor products of the same type that are manufactured, as well as variations in heat resistance. The problem of expansion of the capacitor case may occur.

  As important as the amount of the electrolyte to be impregnated, it is important whether the electrolyte is sufficiently penetrated into fine irregularities formed on the surface of the electrode foil by etching, that is, pits. This greatly affects the electrical performance of the capacitor. If the electrolyte does not penetrate sufficiently into the pits of the electrode foil, the electrode surface is not in contact with the electrolyte, and voids are formed, increasing the tan δ and equivalent series resistance (ESR) of the electrolytic capacitor. No good electrical characteristics were obtained.

  Currently, the vacuum impregnation method is widely used as an impregnation method of the electrolytic solution having the above technical significance. The vacuum impregnation method is a method in which a capacitor element is put in a container and evacuated, and an electrolytic solution is put therein to completely cover the element, and then the container is returned to atmospheric pressure. As a specific example of this method, for example, the lead wires of a plurality of capacitor elements are clamped or taped and attached, and the capacitor elements are transported into an impregnation tank, and the impregnation tank is evacuated. There is a method in which an electrolytic solution is supplied into an impregnation tank to impregnate a capacitor element (for example, see Patent Document 1).

  Such a vacuum impregnation method has a feature that it is excellent in mass production effect in industrial production because an element can be rapidly impregnated with an electrolytic solution. In addition, since the vacuum impregnation method reduces pressure and then returns to atmospheric pressure to perform impregnation, the electrolytic solution penetrates deep into the pits of the electrode foil, and has an excellent electrical characteristic compared to the quantitative impregnation method described later. It has the feature that can be made. On the other hand, in this method, it is difficult to control the amount of the electrolyte to be impregnated at a constant level. Moreover, although the amount of electrolyte solution can be controlled to some extent by a liquid removal process, since it is difficult to make the amount of liquid removal constant, the amount of electrolyte solution will vary. For this reason, there is a problem that the amount of electrolytic solution impregnated in the capacitor element and taken into the element enclosing case is greatly varied, and the product life varies among the same type of electrolytic capacitor products manufactured. Also, the vacuum impregnation method tends to have an excessive amount of electrolyte solution impregnated in the device in an actual industrial production, and problems such as the described liquid leakage and case expansion tend to be inherent.

  There is also a method for making the amount of electrolytic solution to be impregnated constant called a quantitative impregnation method. In this method, a specified amount of electrolytic solution is placed in an element enclosing case, a capacitor element is inserted and immersed therein, and the element is waited to be impregnated with the electrolytic solution. However, in this method, when a capacitor element is inserted into an element enclosing case containing an electrolyte, the electrolyte may jump out of the gap between the case and the element due to a pumping phenomenon or the like, and the specified amount of electrolyte in the case is not guaranteed. There is a problem that the element is not impregnated. In addition, the overflow of the electrolyte also causes cost and environmental problems in manufacturing the capacitor. As a solution to this problem, a method has been proposed in which the volume of the element enclosing case is made larger than the sum of the volume of the electrolytic solution, the volume of the capacitor element, and the volume of the sealing body (see Patent Document 2). However, it does not satisfy the recent demand for miniaturization of electrolytic capacitors.

  Furthermore, since this method leaves the impregnation of the electrolyte solution naturally, there is a problem that it takes time for the impregnation. In addition, it is difficult for the electrolyte to sufficiently penetrate into the pits on the surface of the electrode foil as compared with the vacuum impregnation method, and even if the same amount of electrolyte is used, superiority or inferiority in electrical characteristics is likely to occur between manufactured capacitors. There is a problem. In particular, this phenomenon becomes remarkable in an electrolyte solution having a high viscosity.

JP 2000-357639 A Japanese Patent Laid-Open No. 9-213591

  The present invention seeks to provide an improved electrolytic solution impregnation method and apparatus that solves the above-mentioned various problems of the conventional quantitative impregnation method and vacuum impregnation method.

  That is, an object of the present invention is to provide a method for reliably impregnating a capacitor element with a specified amount of electrolyte without excess or deficiency without increasing the size of the element enclosure case. As a result, the electrolyte to be taken into the case is not excessive, and there is little variation in the amount of electrolyte to be impregnated into the device, and it is excellent in reliability, and the electrical characteristics are equivalent to those obtained by the conventional vacuum impregnation method. It is an object of the present invention to provide an electrolytic capacitor having

  In order to solve the above-mentioned problems, the method for impregnating an electrolytic solution in the production of an electrolytic capacitor according to claim 1 includes a capacitor element wound with an anode foil, a cathode foil, and a separator interposed therebetween, and a specified amount of the electrolyte solution. A method for impregnating an electrolytic solution in manufacturing an electrolytic capacitor in which an element is impregnated with an electrolytic solution by inserting the device into an encapsulated device case, and electrolyzing a part of the capacitor element to the extent that the electrolytic solution in the case does not overflow. A first impregnation step in which the element is immersed in the solution and the element absorbs the electrolyte; and a second impregnation step in which the element is completely accommodated in the case and the remaining electrolyte is absorbed in the element. In addition, at least one of the two impregnation steps includes a pressure reduction step in which the impregnation is performed in a reduced pressure atmosphere and then returned to the atmospheric pressure atmosphere.

  In the impregnation method according to claim 2, before the first impregnation step in the method according to claim 1, the capacitor element and the case containing the specified amount of electrolytic solution are placed in a reduced pressure atmosphere. Features.

  The impregnation method according to claim 3 is characterized in that in the impregnation method according to claim 1 or claim 2, the decompression step is performed in the first impregnation step.

  The impregnation method according to claim 4 is characterized in that in the impregnation method according to claim 1 or claim 2, the decompression step is performed in the second impregnation step.

  The impregnation method according to claim 5 is characterized in that in the impregnation method according to claim 1 or claim 2, the decompression step is performed in the first impregnation step and the second impregnation step.

  The impregnation method according to claim 6 is the impregnation method according to any one of claims 1 to 5, wherein the pressure reduction step is repeatedly performed a plurality of times.

  According to a seventh aspect of the present invention, there is provided an apparatus for impregnating an electrolytic solution in the production of an electrolytic capacitor, comprising means for carrying out the impregnation method according to any one of the first to sixth aspects.

  According to the impregnation method of the present invention, the impregnation of the electrolytic solution into the capacitor element is performed by a preliminary impregnation step (first step) in which a part of the capacitor element is immersed to the extent that the electrolytic solution does not overflow from the element enclosure case. Since the impregnation step is performed, the liquid level of the electrolytic solution in the case can be lowered by the preliminary impregnation. Therefore, even if the capacitor element is completely accommodated in the case in this state, it is possible to prevent the electrolyte from overflowing. Furthermore, since the electrolytic solution can be prevented from overflowing outside the case, it is possible to solve the cost and environmental problems in manufacturing the capacitor.

  Thus, according to the impregnation method of the present invention, the capacitor element can be reliably impregnated with the entire amount of the electrolyte contained in the element enclosing case without overflowing. Without increasing the size, an electrolytic capacitor with little variation in the amount of electrolyte impregnation can be produced.

  In addition, since the method of the present invention includes a pressure reducing step in which the impregnation step of the electrolytic solution is performed in an atmosphere in a reduced pressure state and then returned to the atmospheric pressure atmosphere, the impregnation of the electrolytic solution is performed rapidly and Electrolyte can be penetrated deep into the pits of the electrode foil. As a result, it is possible to produce an electrolytic capacitor having the same electrical characteristics as those obtained by the vacuum impregnation method while taking advantage of the quantitative impregnation method.

  Embodiments of an electrolytic solution impregnation method in the production of an electrolytic capacitor according to the present invention will be described below with reference to the drawings. (A) thru | or (f) of FIG. 1 is a conceptual diagram which shows the impregnation method of this invention.

  In this figure, reference numeral 1 denotes a case for enclosing a capacitor element, and the case 1 is fitted into a holder 8 having a concave section fixed to the base 7 and installed (FIG. A). The element enclosing case 1 is made of aluminum or aluminum alloy that is usually used in an electrolytic capacitor, and has a bottomed cylindrical shape.

  A prescribed amount of the electrolytic solution 2 is injected into the case 1 and the capacitor element 3 is arranged so as not to be immersed in the electrolytic solution 2 (FIG. B).

  When the electrolyte solution has a high viscosity, it is possible to attach the heater to the electrolyte injection device when injecting the electrolyte solution or to heat the holder 8 with a heater in order to perform smooth impregnation.

  Capacitor element 3 is surface-treated by etching aluminum foil, and further, natural fiber or synthetic material between anode foil formed with a dielectric film by anodic oxidation and cathode foil subjected to surface-expansion treatment by etching aluminum foil. It is constituted by winding through a fiber separator. Lead terminals 4 and 5 for external lead are attached to the anode foil and the cathode foil, respectively. Further, a sealing body 6 is attached to the capacitor element 3. The sealing body is attached through lead terminals 4 and 5 through a pair of holes formed in the sealing body 6. The timing of mounting the sealing body may be after the impregnation work of the electrolytic solution is completed. As the lead terminals and sealing bodies used in the present invention, those normally used in the production of electrolytic capacitors can be used as they are.

  The capacitor element 3 can be arranged by holding a pair of lead terminals 4 and 5 on, for example, a chuck attached to a carrying holder of the element or by adhering it to a taping material.

  Next, the container 9 is covered (FIG. C), and the inside of the container is evacuated and decompressed. Exhaust is performed using a vacuum pump from an exhaust port 10 provided in the container. By reducing the pressure, the water contained in the capacitor element and the water in the electrolyte easily evaporate. As a result, the moisture contained in the capacitor element and the moisture in the electrolytic solution can be reduced, so that the influence on the electrical characteristics due to the moisture entering the capacitor can be reduced. As described above, the purpose of reducing the pressure inside the container 9 is to remove moisture, and it is desirable that the degree of decompression is as low as possible for rapid moisture removal. Considering efficient production, it is preferably 10 to 50 mmHg, more preferably 10 to 30 mmHg.

  Next, the capacitor element is immersed in an electrolytic solution for impregnation. In the method of the present invention, the impregnation with the electrolytic solution is performed in two steps. First, in the first step of performing the preliminary impregnation, a part of the capacitor element 3 is immersed in the electrolytic solution 2 to the extent that the electrolytic solution 2 in the case 1 does not overflow to absorb the electrolytic solution (FIG. D). And e). Next, in the second impregnation step, the capacitor element 3 is completely inserted until it contacts the bottom surface of the case 1, and the remaining electrolyte 2 is absorbed by the element 3 (FIG. F).

  In the method of the present invention, at least one of the first impregnation step and the second impregnation step described above is performed by evacuating the inside of the container 9 and performing impregnation in a reduced pressure atmosphere, and then returning the atmosphere to atmospheric pressure. It is comprised including the process of the decompression process. By so doing, the impregnation rate of the electrolytic solution into the element can be increased, and the electrolytic solution can be penetrated deep into the pits of the electrode foil. Therefore, it is more preferable to perform the above-described decompression process in each of the first and second impregnation steps.

  The degree of pressure reduction is appropriately selected depending on the viscosity of the electrolytic solution. Considering the efficiency of the impregnation step, the degree of decompression is preferably 5 to 100 mmHg, more preferably 5 to 40 mmHg.

  After completion of the impregnation process, the container 9 is removed, and the portion corresponding to the sealing body 6 on the upper part of the case 1 is drawn to seal the opening of the case 1.

A wound-structure aluminum electrolytic capacitor (35 WV, 200 μF, φ8 × 10 L) was prepared by the following procedure, which was usually performed, and the electrical performance and the amount of impregnation of the electrolytic solution were measured. For comparison, the same measurement was performed on an electrolytic capacitor prepared by a conventional impregnation method.
[Capacitor element]
A high-purity aluminum foil was electrochemically etched and subjected to chemical conversion treatment to form an oxide film on the surface to produce an anode foil. In addition, another aluminum foil was similarly subjected to an etching process to produce a cathode foil. Electrode lead wires were attached to the positive electrode and the negative electrode, respectively, and then wound with a separator sandwiched between both electrode foils to produce a capacitor element.
[Electrolyte]
An electrolytic solution having the composition shown in Table 1 was used.

[Removal of water from capacitor element and electrolyte]
As a case for encapsulating a capacitor element, an electrolytic solution having a target value of 160 mg is injected into a cylindrical bottomed aluminum case, and the lead terminal portion of the capacitor element is fixed with a chuck and inserted into the above-described element enclosing case. It was held at a position where it was not immersed. The container was covered from above, the case containing the element and the electrolyte was placed in a sealed space, and evacuated using a vacuum pump to remove moisture by reducing the pressure in the container to 30 mmHg.
(Impregnation treatment)
The impregnation method of Example 1 The lower part of the capacitor element is immersed in the electrolytic solution to the extent that the electrolytic solution does not overflow from the case while maintaining the above-described reduced pressure state, and the atmosphere in the container is returned to atmospheric pressure in this state. The element was made to absorb the electrolytic solution. Next, the capacitor element was completely inserted to the bottom of the case, and the remaining electrolyte solution was absorbed naturally.

The impregnation method of Example 2 Capacitor element and electrolytic solution were subjected to the above depressurization and water removal, and the pressure in the container was once returned to the atmospheric pressure, and then the capacitor element was limited to the extent that the electrolytic solution did not overflow from the case The lower part of was immersed in an electrolytic solution. Next, the container was evacuated, the inside of the container was decompressed to 40 mmHg, the capacitor element was completely inserted to the bottom of the case while maintaining this decompressed state, and the pressure inside the container was returned to atmospheric pressure to complete the impregnation.

The impregnation method of Comparative Example 1 The lead terminal was fixed by taping, the capacitor element was placed in the impregnation tank, and the inside of the impregnation tank was decompressed to 30 mmHg using a vacuum pump. Next, the electrolytic solution was injected from the electrolytic solution tank into the impregnation tank, the decompression was released, the interior of the impregnation tank was returned to atmospheric pressure, and the electrolytic solution was impregnated. Next, the amount of the electrolytic solution was adjusted to 160 mg by liquid removal treatment, and the element impregnated with the electrolytic solution was placed in an enclosing case.

Impregnation method of Comparative Example 2 An electrolyte solution having a target value of 160 mg was injected into the element enclosing case, the lead terminal was fixed with a chuck, the capacitor element was inserted into the container, and the electrolyte solution was naturally impregnated.
[Sealing of element enclosure]
A capacitor element was attached to the sealing body through a lead terminal in each of a pair of through holes provided in the sealing body, and the upper part of the case where the sealing body was located was drawn to seal the case.

As described above, a 35 WV, 200 μF winding structure aluminum electrolytic capacitor (φ8 × 10 L) was prepared.
[Electrical performance comparison test]
Electrolytic capacitors (Examples 1 and 2) prepared by the electrolytic solution impregnation method according to the present invention were tested, and the electrolytic capacitors (Comparative Examples 1 and 2) prepared by the conventional impregnation method were used. Compared with. The measurement was performed in two ways before loading and after loading at high temperature voltage (105 ° C., 35 V, time 1000 hours). All capacitor characteristics were measured at 25 ° C. The capacity and Tan δ value were measured at 120 Hz, and the ESR value was measured at 10 KHz. LC (leakage current) was measured as a current value 1 minute after application of 35V. The results are shown in Table 2.

As can be seen from the data shown in Table 2, the electrolytic capacitors (Example 1 and Example 2) prepared by the impregnation method of the present invention are compared with the electrolytic capacitor (Comparative Example 1) prepared by the conventional vacuum impregnation method. The electrostatic capacity, Tan δ, leakage current, and ESR value are equivalent or better before and after loading. Compared with the electrolytic capacitor prepared by the quantitative impregnation method of Comparative Example 2, the Tan δ and ESR values are low. In particular, changes in Tan δ and ESR values in Comparative Example 2 after high-temperature voltage loading are larger than those in Examples 1 and 2.
[Variation test of electrolyte impregnation amount]
The amount of electrolytic solution impregnated in the electrolytic capacitors (Example 1 and Example 2) prepared by the method of the present invention was measured and compared with those of electrolytic capacitors (Comparative Example 1 and Comparative Example 2) prepared by the conventional method. The results are shown in Table 3. In addition, the amount of electrolyte impregnation was measured as follows.

  The weights of individual capacitor elements, aluminum cases, and sealing rubbers were measured in advance and then put into an impregnation apparatus, and the individual capacitor weights were measured. The amount of the electrolyte was obtained by subtracting the weight of each material from the weight of each capacitor.

  From the results shown in Table 3, it can be seen that the electrolytic capacitor produced by the conventional vacuum impregnation method has a large variation in the amount of impregnation of the electrolytic solution. Variations in the amount of the electrolytic solution appear as variations in the life characteristics of the electrolytic capacitor. Further, in the case of a surface mount type electrolytic capacitor, variation in heat resistance is caused, which causes appearance defects (case expansion). In the electrolytic capacitors of Example 1 and Example 2 according to the present invention, the variation in the amount of the electrolytic solution is small, so that stable life characteristics and heat resistance can be obtained.

It is a conceptual diagram for demonstrating the impregnation method of the electrolyte solution of this invention.

Explanation of symbols

1 Capacitor element enclosing case 2 Electrolyte 3 Capacitor element 9 Container 10 Exhaust port

Claims (7)

  Electrolytic solution in electrolytic capacitor production in which a capacitor element wound with an anode foil and a cathode foil and a separator interposed between them is inserted into a case for encapsulating the element containing a specified amount of electrolyte and the element is impregnated with the electrolyte A first impregnation step of immersing a part of the capacitor element in the electrolyte solution as long as the electrolyte solution in the case does not overflow, and absorbing the electrolyte solution in the device; and the element in the case A second impregnation step in which the element is completely accommodated and the remaining electrolyte is absorbed by the device, and after at least one of the two impregnation steps, impregnation is performed in a reduced-pressure atmosphere, A method for impregnating an electrolytic solution in the production of an electrolytic capacitor, comprising the step of reducing the pressure to return to 1.   The method according to claim 1, wherein the capacitor element and the case containing the specified amount of electrolytic solution are placed in a reduced-pressure atmosphere before the first impregnation step.   The method according to claim 1 or 2, wherein the decompression step is performed in the first impregnation step.   The method according to claim 1 or 2, wherein the decompression step is performed in the second impregnation step.   The method according to claim 1 or 2, wherein the decompression step is performed in the first impregnation step and the second impregnation step.   The method according to any one of claims 1 to 5, wherein the decompression step is repeatedly performed a plurality of times.   An apparatus for impregnating an electrolytic solution in the production of an electrolytic capacitor, comprising means for implementing the impregnation method according to any one of claims 1 to 6.

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