JP5822099B2 - Electrolytic capacitor - Google Patents

Description

  The present invention relates to a structure of an electrolytic capacitor in which a capacitor element in which an anode foil and a cathode foil are wound via a separator is housed in a bottomed cylindrical outer case.

  In recent years, there is an increasing demand for downsizing, in particular, thinning of electronic devices. In such a trend of thinning, switching power supplies mounted on electronic devices are also required to be thin. As a smoothing capacitor for a switching power supply, an electrolytic capacitor is frequently used. For such a smoothing capacitor, an electrolytic capacitor having a rated voltage of 200 V or more is used, and a capacitance corresponding to an output current is required.

Against this background, in order to reduce the thickness of electrolytic capacitors, the outer diameter of electrolytic capacitors should be reduced, and such electrolytic capacitors can be placed horizontally to meet the demand for thinning. Yes. As a result, the length dimension of the electrolytic capacitor to realize the electrostatic capacitance required for the smoothing capacitor becomes large. Chi I sand, electrolytic capacitors have come to the rated voltage 200～450V, diameter 6～10.5Mm, it is of about the length 25~60mm used.

With such an electrolytic capacitor having a small diameter and a long length, problems that have not been regarded as problems in the conventional electrolytic capacitor have become apparent. That is, assuming that the electrolytic capacitor is a simple cylindrical part, in order to secure a certain capacitance, the space volume of the capacitor element housed in the outer case also requires a considerable space volume. In order to obtain a certain space volume, an electrolytic capacitor having an outer diameter of about 20 mm to 35 mm used as a normal smoothing capacitor has no significant effect on the length dimension, and depends on the required capacitance. The ratio of the outer diameter to the length dimension can be realized by outer diameter: length dimension outer diameter = 1: 1-2. However, when the outer diameter is less than 10.5 mm, the length dimension increases exponentially in order to obtain a constant space volume in the outer case. For this reason, in an electrolytic capacitor having an outer diameter of less than 10.5 mm, outer diameter: length dimension outer diameter = 1: 3 to about 10, and the electrolytic capacitor has an extremely elongated external shape.

Thus, long have electrolytic capacitors of length at a small diameter, to realize a large capacitance required is generated utilizing a storage space of the exterior case more efficiently. The largest factor that determines the capacitance of an electrolytic capacitor is the anode foil. In order to maximize the capacitance of the anode foil, the anode foil must have an opposing cathode foil, and the cathode foil is the anode foil. It becomes the structure which covers the outer periphery of foil.

  The normal smoothing capacitor employs the above structure, but in addition to the above structure, the normal smoothing capacitor has a separator around the outer periphery of the cathode foil and is wound with a resin tape such as polypropylene or polystyrene sulfide. A structure that stops is used.

On the other hand, an electrolytic capacitor having a small diameter and a long length cannot adopt the same structure as a normal smoothing capacitor. As described above, when the diameter is less than 10.5 mm, the length dimension increases exponentially in order to obtain a constant space volume in the outer case, so that the separator and the coil are fixed around the outer periphery of the capacitor element. By interposing both of the tapes, the storage space is not efficiently used, and the length dimension is significantly increased.

  In particular, when a resin-made tape is used as the winding tape, the adhesive between the resin-based tape base and the adhesive is often not good, and the winding tape is placed on the outer circumference of the capacitor element for about one and a half to two rounds. Otherwise, the anti-winding tape is easily peeled off and the shape of the capacitor element cannot be maintained. There is a problem that the outer diameter of the capacitor element becomes larger and the outer case needs to have a larger diameter as the winding tape is rotated.

  For this reason, a separator is not interposed on the outer periphery of the capacitor element, and the capacitor element is wound around the entire surface of the capacitor element with a winding tape and stored in an outer case (Patent Document 1), or the separator is placed on the outer periphery of the cathode foil. It has been practiced to wind and fix with an adhesive or the like to efficiently use the storage space of the outer case (Patent Document 2).

Japanese Patent Laid-Open No. 03-96211 JP-A-60-163422

  By the way, in the electrolytic capacitor having a small outer diameter, the distance between the lead of the anode lead and the cathode lead is also narrowed. For example, in an electrolytic capacitor having a diameter of 10.5 mm, the distance between leads is about 5.0 mm, and in an electrolytic capacitor having a diameter of 8 mm, the distance between leads is about 3.5 mm.

  In addition, the distance between the outer case and the bipolar terminal on the lead wire lead-out end surface is also reduced. For example, in an electrolytic capacitor having a diameter of 10.5 mm, the distance between the leads of both electrodes and the outer case is about 1.5 mm, and in an electrolytic capacitor having a diameter of 8 mm, the distance between the leads of both electrodes and the outer case is about 0.8 mm.

As a result, in a small-diameter electrolytic capacitor having an outer diameter of less than 10.5 mm, a short circuit between the anode lead and the cathode lead or a short circuit between the anode lead and the outer case is likely to occur. This tendency further increases the possibility of short-circuiting when the outer diameter is reduced. Note that the cause of these short-circuits is due to the solder flow when the electrolytic capacitor is mounted on the printed board.

  Among these, a short circuit between the two electrode leads is provided with a partition wall on the sealing member of the electrolytic capacitor, and a structure is devised so that the two electrode leads are not close to each other, thereby preventing a short circuit.

  In addition, in order to insulate the anode lead from the outer case, an insulating outer sleeve is coated on the outside of the electrolytic capacitor to insulate the outer case, including the curling part, and to insulate the lead wire from the outer case. ing.

Such an insulation measure is extremely effective for an electrolytic capacitor having a large diameter exceeding 10.5 mm, but for an electrolytic capacitor having an outer diameter of less than 10.5 mm, the accuracy of curling of the outer case, The influence of the accuracy of the sleeve covering position control increases.

  In particular, the outer sleeve is coated with a heat-shrinkable resin material on the outer case of the electrolytic capacitor and heated to adhere closely to the outer case of the electrolytic capacitor. Is big. In small-diameter electrolytic capacitors, the margin of the portion to be covered with the outer sleeve on the lead wire lead-out surface is extremely small, so the dimensional accuracy after coating of the outer sleeve is strictly controlled by temperature during the manufacturing process. Needed.

In addition, as a small-diameter electrolytic capacitor, one having a minimum outer diameter of about 4 mm has been conventionally used. Therefore, although there is a variation in the accuracy of the covering position of the outer sleeve as described above, it has not been regarded as a problem. The reason is that an electrolytic capacitor having an outer diameter of about 4 mm has a length of about 5 to 7 mm. In such an electrolytic capacitor, the CV product (product of the capacitance and the rated voltage of the electrolytic capacitor), that is, This is because the amount of charge accumulated in the electrolytic capacitor is small. For example, the CV product of an electrolytic capacitor having an outer diameter of 4 mm, a length dimension of 7 mm, and a rated voltage of 4 to 100 V is approximately 0.0140 × 10 −2 C. The electrolytic capacitor having an outer diameter of less than 10.5 mm is a so-called low voltage electrolytic capacitor having a rated voltage of 100 V or less.

  In such an electrolytic capacitor having an outer diameter of less than 10.5 mm, the amount of charge accumulated in the electrolytic capacitor is small and the rated voltage is low. This is because the possibility that the lead wire and the outer case are short-circuited is low.

On the other hand, electrolytic capacitors having an outer diameter of 10.5 mm or more are in practical use as electrolytic capacitors having a rating of 200 V or more used as high-voltage electrolytic capacitors. Such an electrolytic capacitor having an outer diameter of 10.5 mm and a length dimension of 25 mm and a rated voltage of 4 to 100 V has a CV product of about 1.5 × 10 −2 to 2.5 × 10 −2 C. Is 10.5 mm, the length is 25 mm, and the CV product of an electrolytic capacitor having a rated voltage of 200 to 450 V is 0.7 × 10 −2 to 1.0 × 10 −2 C.

As described above, in the electrolytic capacitor having a diameter of 10.5 mm, the distance between the leads is about 5.0 mm, and the distance between the leads of both electrodes and the outer case is about 2.0 mm. However, insulation between the lead wires and between the lead wires and the outer case was maintained.
However, when an electrolytic capacitor having a rated voltage of 200 V or more is to be realized with an electrolytic capacitor having a diameter of less than 10.5 mm, the problem of insulation between the lead wires and between the lead wires and the outer case becomes significant. In particular, an electrolytic capacitor that is an object of the present invention has a rated voltage of 200 to 450 V, a diameter of 6 to 10.5 mm, and a length dimension of 25 mm or more. Even in such an electrolytic capacitor, the CV product is 0.7 × 10 ⁻² to It is necessary to realize 1.0 × 10 ⁻² C.
In such an electrolytic capacitor having an outer diameter of less than 10.5 mm, a rated voltage of 200 V or more, and a CV product exceeding 0.7 × 10 ⁻² , there is an increased risk of contact between the anode lead wire and the outer case. .

  And the problem when an anode lead wire and an exterior case contact is described. The outer case of the electrolytic capacitor is made of aluminum. When the outer case and the anode lead wire are electrically connected, an oxide film grows on the inner surface of the outer case due to anodic oxidation. That is, the electrolytic solution used for the electrolytic capacitor has a chemical conversion ability, and when a positive charge is applied to the metal aluminum in a state where the electrolytic solution is in contact, an oxide film is formed. Since the growth of the oxide film grows in proportion to the applied voltage, a thick oxide film is formed in an electrolytic capacitor having a rated voltage of 200 V or more. When the oxide film is formed, heat is generated. In particular, when the applied voltage is high, the heat generation state continues for a long time. This heat generation may shrink or melt the resin winding tape, causing a short circuit between the positive potential outer case and the negative potential cathode foil.

  On the other hand, such a problem of short between the outer case and the cathode foil is less likely to occur in an electrolytic capacitor in which a separator is wound around the outer periphery and fixed with an adhesive.

  However, an electrolytic capacitor in which the separator is wound around the outer periphery of the capacitor element and fixed with an adhesive has a problem in that volumetric efficiency is deteriorated.

  Kraft paper, Manila hemp paper, etc. are generally used as separators for electrolytic capacitors. The characteristics required for this separator include a sufficient thickness for insulating the anode foil and the cathode foil, a holding capacity for holding the electrolytic solution, and a density at which ions can easily move in the electrolytic solution. From such a viewpoint, an electrolytic capacitor having a rated voltage of 200 V or more uses a separator having a thickness of about 40 μm and a relatively low density.

  However, when the outer periphery of the capacitor element is wound using such a separator, the outer diameter of the capacitor element is increased. When a separator having a thickness of 40 μm as described above is wound around the outer periphery, a large diameter of 80 μm is caused.

  The characteristics required for the anti-winding tape used on the outer periphery of the capacitor element are high insulation and heat resistance, and the electrolyte holding ability is not required. For this reason, the characteristics required of the capacitor element separator and the characteristics required of the capacitor element winding tape are different.

The present invention has been made under the background as described above. In an electrolytic capacitor having an outer diameter of less than 10.5 mm, a small diameter of 30 mm or more and a long diameter, the electrolytic capacitor is miniaturized and the outer case is provided. It is an object of the present invention to provide an electrolytic capacitor with high safety without short-circuiting the electrolytic capacitor even when the anode lead wire is short-circuited.

In the invention according to claim 1 of this application, a capacitor element formed by winding an anode foil and a cathode foil through a separator is housed in a bottomed outer case made of aluminum, and the opening end of the outer case is sealed with a sealing body. In the electrolytic capacitor formed by sealing, the ratio of the outer diameter and the length dimension of the electrolytic capacitor is 1: 3 to 10, the cathode foil is disposed on the outermost periphery of the capacitor element, and the adhesive is provided on one side. The electrolytic capacitor is characterized in that the element is wound with a paper tape.
According to this, even when the anode lead wire and the outer case are in contact with each other in an electrolytic capacitor having a small diameter and a long length (the outer diameter is less than 10.5 mm and the height and length are 30 mm or more). However, due to the heat generated during the generation of the anodized film of the outer case, the conventional resin-made anti-winding tape may be melted by the heat generation, causing the cathode foil and the outer case to come into contact with each other. In the invention, since a paper tape is used, the paper tape does not have a possibility of fusing or the like with respect to the heat generation, and the insulation between the cathode foil and the outer case can be reliably ensured, and a highly safe electrolytic capacitor is provided. Can do.

The invention according to claim 2 of this application is characterized in that, in the electrolytic capacitor according to claim 1, the electrolytic capacitor is a high-voltage electrolytic capacitor having a rated voltage of 200 V or more. According to this, although the electrolytic capacitor has a small diameter and a long length, the electrolytic capacitor that can be used as a primary smoothing capacitor of a switching power supply with a rated voltage of 200 V can be realized.

  The invention according to claim 3 of this application is the electrolytic capacitor according to claim 1 or 2, wherein the paper tape is a paper tape having a thickness smaller than that of the separator, and the paper tape is 1 / of the outer peripheral length of the capacitor element. It is characterized by overlapping at a length of 3 or less. According to this, the thickness of the paper tape is thinner than the thickness of the separator, and the overlap length of the paper tape is 1/3 or less of the outer peripheral length of the capacitor element, so that the capacitor element can be reduced in size and applied to the outer case. Storage efficiency can be increased.

As described above, according to the present invention, in an electrolytic capacitor having a small diameter and a long length , the electrolytic capacitor is not short-circuited even when the outer case and the anode lead wire are short-circuited along with downsizing of the electrolytic capacitor. It is possible to provide a highly safe electrolytic capacitor.

  The electrolytic capacitor of the present invention will be described in detail below.

  As an electrolytic capacitor used in the present invention, an anode foil obtained by subjecting a metal foil such as a valve action metal, such as aluminum or tantalum, to an etching treatment and an anodizing treatment, and a cathode foil obtained by carrying out an etching treatment are used for kraft paper, manila. Capacitor elements that are wound with a separator made of paper or the like sandwiched between them are housed in a metal or resin outer case made of bottomed cylindrical aluminum or the like, and the opening end of the outer case is made of rubber or the like Seal with your body. A lead terminal is connected in advance to the anode foil and the cathode foil, and the lead foil is drawn to the outside through a through hole provided in the sealing body.

  In this capacitor element, a cathode foil and an anode foil are laminated and wound via a separator, and the cathode foil is exposed at the outermost periphery of the capacitor element. The outermost cathode foil is attached with a paper tape coated with an adhesive on one side to prevent the capacitor element from being wound. This paper tape is set to a size that covers the entire exposed portion of the outermost cathode foil, so that the cathode foil and the outer case are not in direct contact with each other. The separator has a sufficient thickness for insulating the anode foil and the cathode foil, a holding capacity for holding the electrolytic solution, and a density such that ions can easily move in the electrolytic solution. From such a viewpoint, an electrolytic capacitor having a rated voltage of 200 V or more uses a separator having a thickness of about 40 μm and a relatively low density. On the other hand, the paper tape for winding is different from the characteristics required for the separator, and has high insulating properties and heat resistance, and does not require electrolyte holding ability. For this reason, the thickness of the paper tape for winding can be made thinner than the thickness of the separator, the thickness of the paper tape excluding the adhesive can be made 15 to 35 μm, and the capacitor element can be miniaturized. . The width of the paper tape (the width in the vertical direction of the capacitor element) is preferably shorter than the width of the separator and longer than the width of the cathode foil. As a result, the paper tape can be prevented from protruding from the end face of the capacitor element, and contact between the cathode foil and the outer case can be prevented.

  The paper tape is attached to the outermost cathode foil of the capacitor element. However, the paper tape is attached so as to be wound one or more times along the outer periphery of the capacitor element so that the paper tape partially overlaps. Good. This is because the fixing strength is higher when the paper tape is applied to the paper tape of the same material than when the paper tape is applied to the cathode foil. However, if the overlapping portion of the paper tape is large, the outer diameter of the capacitor element becomes large. Therefore, the overlapping portion is preferably set to 1/3 or less of the outer peripheral length of the capacitor element.

  An adhesive is applied to one side of the paper tape (on the side attached to the cathode foil). As this adhesive, those having high heat resistance are suitable, and examples thereof include acrylic adhesives, rubber adhesives, and silicone adhesives. These adhesives are formed on one side of a paper tape by a known technique such as known coating. A paper tape may be in a surface state where the front and back surfaces of the paper tape are different depending on the material, papermaking conditions, and the like. The adhesive can obtain desired adhesive strength with a small coating amount by forming the adhesive on the flat surface of the front and back of the paper tape. This is because the surface of the uneven side of the separator is coated with the applied adhesive, and the amount of adhesive applied increases, whereas on the flat side of the separator, the adhesive is This is because it can be thinly formed on a flat surface with a minimum amount of adhesive. In some cases, a double paper composed of a plurality of separators is used as the separator. In this case, it is preferable to form an adhesive on the surface of the high-density separator and attach it to the cathode foil. This is because the surface of the high-density separator is flat compared to the surface of the low-density separator and can be formed thin with a minimum amount of adhesive applied. In addition, as for the thickness of an adhesive agent, 10-30 micrometers is preferable. Further, the adhesive may be formed on the entire surface of one side of the separator, or may be formed partially (dots or the like).

Next, the specifications of the electrolytic capacitor of the present invention will be described.
The electrolytic capacitor of the present invention is mainly used as a smoothing capacitor mounted on a switching power supply mounted on an electronic device. Therefore, the outer diameter of the outer case is less than 10.5 mm from the viewpoint of a rated voltage of 200 V or more and reduction in thickness. Thus, in order to obtain a certain space volume in the exterior case, the length dimension is an outer diameter: length dimension outer diameter = 1: 3 to about 10, that is, an electrolytic capacitor of 30 mm or more.

  As described above, the present invention is used as a smoothing capacitor, and as the switching power supply is thinned, the electrolytic capacitor is reduced in size. This has been made to solve the short circuit failure due to a short circuit.

  Hereinafter, further detailed description will be made using examples.

Example 1
A 110 μm-thick anode foil subjected to etching treatment and anodizing treatment was used as the anode foil, and a 20 μm-thick cathode foil subjected to etching treatment was used as the cathode foil. As the separator, electrolytic paper mainly composed of kraft paper having a thickness of 60 μm was used, and these were wound to form a capacitor element. A separator and a cathode foil were disposed so that the winding end portion of the capacitor element was opposed to the anode foil, so that the cathode foil became the outermost periphery. At this time, the winding end positions of the separator and the cathode foil were made the same.
Then, a kraft paper having a thickness of 30 μm was cut into 30 mm to prepare a paper tape, and an acrylic adhesive was applied to the tip of one side of the paper tape. And it was made to wrap around the outer periphery of a capacitor | condenser, the paper tapes were adhere | attached so that the paper tape might overlap 7 mm, and the capacitor | condenser element was stopped. The outer periphery of the capacitor element is 23 mm.
The capacitor element formed as described above is housed in an aluminum bottomed cylindrical case having an outer diameter of 8 mm and a length of 50 mm together with a sealing rubber, and the opening end of the outer case is curled to seal the electrolytic capacitor. Went. Further, an exterior sleeve made of polyethylene terephthalate was coated on the exterior case and thermally contracted to insulate the exterior case of the electrolytic capacitor.

(Conventional example 1)
An anode foil having a thickness of 110 μm subjected to etching treatment and anodizing treatment was used as the anode foil, and a cathode foil having a thickness of 20 μm subjected to etching treatment was used as the cathode foil. As the separator, electrolytic paper mainly composed of kraft paper having a thickness of 60 μm was used, and these were wound to form a capacitor element. A separator and a cathode foil were disposed so that the winding end portion of the capacitor element was opposed to the anode foil, so that the cathode foil became the outermost periphery. At this time, the winding end positions of the separator and the cathode foil were made the same.
Then, prepared taped winding is cut polyphenylene sulfide tape having a thickness of 30μm to 30 mm, was coated with an acrylic adhesive on one surface of the distal end portion of the winding stop tape. And allowed to orbit the outer circumference of the capacitor winding stop tape to adhere the winding stop tape together as overlapping 7 mm, it stopped up the capacitor element. The outer periphery of the capacitor element is 23 mm.
The capacitor element formed as described above is housed in an aluminum bottomed cylindrical case having an outer diameter of 8 mm and a length of 50 mm together with a sealing rubber, and the opening end of the outer case is curled to seal the electrolytic capacitor. Went. Further, an exterior sleeve made of polyethylene terephthalate was coated on the exterior case and thermally contracted to insulate the exterior case of the electrolytic capacitor.

(Conventional example 2)
An anode foil having a thickness of 110 μm subjected to etching treatment and anodizing treatment was used as the anode foil, and a cathode foil having a thickness of 20 μm subjected to etching treatment was used as the cathode foil. As the separator, electrolytic paper mainly composed of kraft paper having a thickness of 60 μm was used, and these were wound to form a capacitor element. A separator and a cathode foil were disposed so that the winding end portion of the capacitor element was opposed to the anode foil, so that the cathode foil became the outermost periphery. At this time, the winding end positions of the separator and the cathode foil were made the same.
And the 30-micrometer-thick polypropylene tape was cut | disconnected to 30 mm, the anti- winding tape was prepared, and the acrylic adhesive was apply | coated to the front-end | tip part of the single side | surface of the anti- winding tape . And allowed to orbit the outer circumference of the capacitor winding stop tape to adhere the winding stop tape together as overlapping 7 mm, it stopped up the capacitor element. The outer periphery of the capacitor element is 23 mm.
The capacitor element formed as described above is housed in an aluminum bottomed cylindrical case having an outer diameter of 8 mm and a length of 50 mm together with a sealing rubber, and the opening end of the outer case is curled to seal the electrolytic capacitor. Went. Further, an exterior sleeve made of polyethylene terephthalate was coated on the exterior case and thermally contracted to insulate the exterior case of the electrolytic capacitor.

(Conventional example 3)
Similarly to the example, an anode foil having a thickness of 110 μm subjected to etching treatment and anodizing treatment was used as the anode foil, and a cathode foil having a thickness of 20 μm subjected to the etching treatment was used as the cathode foil. These anode foil and cathode foil had the same width and length as in the examples. As in the example, electrolytic paper mainly composed of kraft paper having a thickness of 60 μm was used as the separator, and these were wound to form a capacitor element. The cathode foil was disposed so that the winding end portion of the capacitor element was opposed to the anode foil. Furthermore, only the separator was circulated around the outer periphery of the capacitor element, the separators were bonded together with an acrylic adhesive, and the capacitor element was unwound. The outer periphery of the capacitor element is 25 mm.
The capacitor element formed as described above, together with the sealing rubber, is housed in an aluminum bottomed cylindrical outer case having an outer diameter of 8 mm and a length of 50 mm, and the opening end of the outer case is curled to obtain an electrolytic capacitor. Sealed. Further, an exterior sleeve made of polyethylene terephthalate was coated on the exterior case and thermally contracted to insulate the exterior case of the electrolytic capacitor.

  In the electrolytic capacitors of the completed Example 1 and Conventional Examples 1 to 3, a predetermined voltage is applied to the cathode terminal and the anode terminal in a state where the exterior case and the anode terminal are in contact, and the cathode foil and the exterior case are short-circuited. The number of electrolytic capacitors reached was confirmed. Each electrolytic capacitor has a rated voltage of 450 wv and a capacitance of 21 μF. Moreover, it was set as the evaluation by three each.

(Table 1)

As shown in the evaluation results (Table 1), it was found that in the conventional examples 1 and 2, a short circuit occurs when a voltage of 495v is applied. On the other hand, in Example 1 of this invention, it turns out that a short circuit does not arise even if 585v is applied. Further, in the conventional example 3, since the winding is stopped by the separator, a short circuit does not occur even when 540v is applied as in the first embodiment, but the size of the capacitor element is the same as that of the first embodiment. Therefore, the exterior case swells in several tens of minutes after applying each voltage.

Claims (2)

Capacitor element with an anode foil and a cathode foil formed by winding via a separator is housed in a bottomed outer case comprising aluminum Rutotomoni, open end of the outer case are sealed with a sealing member, and the outer of the electrolytic capacitor The diameter is less than 10.5 mm, the ratio of the outer diameter to the length dimension is 1: 3 to 10, the cathode foil is arranged on the outermost periphery of the capacitor element, and the element is made of a paper tape provided with an adhesive on one side. in winding unstoppable electrolytic capacitor,
Electrolytic capacitor wherein the paper tape, together with the a small thickness paper tape than the separator, characterized in that the paper tape're I Kasanaria at 1/3 or less of the length portion of the outer peripheral length of the capacitor element. 2. The electrolytic capacitor according to claim 1, wherein the electrolytic capacitor is a high-voltage electrolytic capacitor having a rated voltage of 200 V or more.