JP4900765B2 - Electrolytic capacitor - Google Patents

Description

  The present invention relates to an aluminum electrolytic capacitor used in various electronic devices.

  The electrolytic capacitor is connected to the lead terminal, and the surface of the film-forming metal foil such as aluminum is etched, and the anode foil having the oxide film formed on the surface is connected to the lead terminal, and the film-forming property such as aluminum is formed. A cathode foil made of a metal foil is wound or laminated with a separator made of electrically insulating electrolytic paper between them to form a capacitor element, and this capacitor element is impregnated with a driving electrolyte. In addition, there is known one that is housed in a bottomed cylindrical outer case made of aluminum and has an opening sealed with a sealing member made of rubber or a resin material.

  In such an electrolytic capacitor, there is a corner in the lead terminal connected to the electrode foil and the connection part between the lead terminal and the electrode foil, and the capacitor element is formed by winding or laminating the electrode foil. May damage the separator due to the contact of the corners, and may cause a short circuit defect due to the stress at the time of winding or stacking and breaking through the separator to contact the opposing electrode foil. As a countermeasure, there has been proposed a capacitor element structure in which paper is attached to a portion of the separator corresponding to the lead terminal (Patent Document 1). According to this, the separator portion corresponding to the lead-out terminal has a double structure by the addressed paper, and a short circuit failure due to the tearing of the separator is prevented.

Japanese Utility Model Publication No. 6-86327

  However, there is an increasing demand for miniaturization and high performance of various devices, and electrolytic capacitors are also required to be small and high performance. Particularly in recent years, with the widespread use of servo motors, electrolytic capacitors have been increasingly used for controlling the servo motors. In this servo motor, electrolytic capacitors are often used mainly in the low frequency region. In this low frequency region, the electrolytic capacitor is repeatedly charged and discharged at several Hz to several tens Hz. The attached electrolytic capacitor has a problem that the ESR characteristic deteriorates in a low frequency region.

  Therefore, the present invention has been proposed to solve the above-described conventional problems, and can reliably prevent short-circuit failure due to separator breakage in an electrolytic capacitor and improve reliability by improving ESR in a low frequency region. The purpose is to provide a high electrolytic capacitor.

As a result of investigating and researching the insulating paper and the adhesive material to be attached to the separator, the adhesive material component for attaching the addressed paper to the separator is a factor that deteriorates the ESR characteristic in the conventional electrolytic capacitor. As a result, further research has been conducted, and it has been found that the back surface release material constituting the adhesive material impedes the permeation of ions in the driving electrolyte solution, thereby reducing the ESR characteristics of the electrolytic capacitor. We examined how to reduce the amount of adhesive applied while maintaining the state of insulating paper affixed.

  The electrolytic paper constituting the insulating paper is in a different state on the front and back surfaces by the paper making process, and one is formed in a flat shape and the other is formed in an uneven shape. Conventionally, it is possible to easily form an adhesive material on the surface of the insulating paper on the uneven side of the insulating paper because it can be easily formed on the surface of the insulating paper so as not to cause misalignment in the winding or laminating process when forming the capacitor element. An adhesive material is formed. However, it was found that the pressure-sensitive adhesive material penetrates into the irregularities, so that the amount of coating is relatively large and the ESR characteristics are deteriorated.

Therefore, the electrolytic capacitor of the present invention is an electrolytic capacitor including a capacitor element in which a separator is interposed between a cathode foil and an anode foil each connected to a lead terminal, and the separator is a portion corresponding to the lead terminal. Insulating paper is disposed between the lead terminal and the insulating paper, one of the front and back surfaces is a flat surface, the other is formed on a concavo-convex surface, and the flat surface has a coating area. An adhesive material of 6% to 0.5% with respect to the foil area of the anode foil is intermittently formed on the surface of the insulating paper and adhered to the separator, and the uneven side surface is directly connected to the lead terminal. It is characterized by touching.

According to this, the desired sticking strength was obtained with a small coating amount by forming the adhesive material on the flat surface of the insulating paper. This is because the surface of the uneven surface of the electrolytic paper has a large amount of adhesive applied since the applied adhesive material enters the uneven surface, whereas the surface of the electrolytic paper on the flat side has an adhesive material. Can be thinly formed on a flat surface with a minimum amount of adhesive material applied, so that the inhibition of ion permeation in the electrolyte is reduced and the ESR characteristics are greatly improved.
Especially in the low frequency region, the amount of ions moving in the driving electrolyte is large, so that more ions pass through the insulating paper. Therefore, by changing the formation structure of the adhesive material on the insulating paper, the driving electrolysis is changed. It is considered that ions in the liquid can be smoothly moved without being obstructed, and good ESR characteristics can be obtained in a low frequency region.

  Further, the insulating paper is characterized in that it is disposed between the separator and the lead terminal. According to this, since the corner portion of the lead terminal does not directly touch the separator and is always in contact with the insulating paper, the performance of the separator can be maintained. Further, since the concave and convex surface of the insulating paper is in direct contact with the lead terminal, and the concave and convex portions are easily filled with the driving electrolyte solution, the ESR characteristics of the electrolytic capacitor can be further improved.

  The pressure-sensitive adhesive material is characterized in that the surface of the insulating paper is intermittently formed in a line shape, a wavy line shape, a dot shape, or the like. According to this, the application amount and the application area of the adhesive material are reduced, and the region that inhibits ion permeation in the driving electrolyte solution is reduced, so that the ESR characteristic of the electrolytic capacitor is improved.

As described above, according to the present invention, the insulating paper is disposed at a portion corresponding to the lead-out terminal of the separator, and this insulating paper is attached to the separator via the adhesive material formed on the flat surface of the front and back surfaces. By sticking, the separator can be prevented from being damaged or short-circuited by the lead terminal, the amount of the adhesive material applied can be reduced, and the ESR characteristics in the low frequency region of the electrolytic capacitor can be improved.

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the anode-side electrode foil is made of a valve metal such as aluminum, and the surface is roughened by an etching process, and an oxide film layer is formed on the surface. The cathode foil 3 is made of a valve action metal such as aluminum like the anode foil 2, and the surface thereof is roughened by an etching process. The anode-side lead terminal 4 made of aluminum and the cathode-side lead terminal 5 made of aluminum are electrically connected to these bipolar electrodes, respectively, by a connection method such as stitching, cold welding, or ultrasonic welding. . The lead terminals 4 and 5 have a flat part connected to the electrode foil and a lead part for external connection, or are composed of strips, one of which is connected to the electrode foil and the other a separate sealing body for external lead. Some are connected to external terminals provided in the.

  The separator 6 interposed between the cathode foil 3 and the anode foil 2 is electrically insulating, and is made of Manila hemp paper, kraft paper, esparto paper or a mixed paper thereof, synthetic fiber, non-woven fabric, or a mixed paper thereof. In the wound capacitor element 1, each of the cathode foil 3 and the anode foil 2 to which one or more lead terminals 4 and 5 are connected is constituted by a belt-like body having a predetermined length, and between the cathode foil 3 and the anode foil 2. It is constituted by winding the separator 6 between them. In the multilayer capacitor element 1, the cathode foil 3 and the anode foil 2 to which the lead terminals 4 and 5 are respectively connected are formed of a flat plate having a predetermined length, and the cathode foil 3 and the anode foil 2 are interposed between the cathode foil 3 and the anode foil 2. Are alternately stacked with separators 6 interposed therebetween. These capacitor elements 1 are impregnated with a driving electrolyte and housed in a bottomed cylindrical metal case made of aluminum or the like, and an opening is a sealing member made of an elastic body or a composite member of an elastic body and a hard body. Sealed by the body.

  Here, when the separator 6 is interposed between the anode foil 2 and the cathode foil 3, an insulating paper is provided at a portion corresponding to the anode-side lead terminal 4 and / or the cathode-side lead terminal 5 connected to the electrode foil. 7 is attached via an adhesive material. The insulating paper 7 is electrically insulating, and is selected from Manila hemp paper, kraft paper, esparto paper, sisal hemp paper, hemp paper, cupra, rayon, cotton, or a mixed paper thereof. Examples of the adhesive material to which the insulating paper 7 is attached include phenol-based, epoxy-based, cyanoacrylate-based, polyimide-based, acrylic-based, silicone-based, rubber-based, and hot-melt-based materials. Of these, polypropylene and polyvinyl alcohol are preferably used.

  The adhesive material is formed on the flat surface 9 of the insulating paper 7 by coating or the like, and the doctor blade method is preferable as the forming method. Specifically, as shown in FIG. 3, a concave roller 14 is arbitrarily provided on the surface by etching by immersing the rotating roller 11 in a tank 13 containing an adhesive and rotating the roller. The adhesive material 8 is held and transferred inside, and the doctor blade 12 provided on a part of the rotating roller 11 scrapes off the excess adhesive material 8, and uses the adhesive material 8 as an appropriate amount to rotate the rotating roller 11 and the elastic roller 15. By passing the insulating paper 7 between them, the adhesive material 8 is formed on the flat surface 9 of the insulating paper 7. In addition, another base material is allowed to pass between the rotating roller 11 and the elastic roller 15 instead of the insulating paper 7, the adhesive material 8 is pasted on the surface of the base material, and the base material and the insulating paper 7 are bonded together. Thus, the adhesive material 8 can be transferred onto the surface of the insulating paper 7. The adhesive material 8 formed on the surface of the insulating paper 7 by the concave portion 14 of the rotating roller 11 is intermittently formed, so that the application amount of the adhesive material 8 can be reduced and the penetration of the electrolyte into the insulating paper 7 is good. And The adhesive material 8 can be arbitrarily formed on the insulating paper 7 by arbitrarily forming the concave portion 14 on the surface of the rotating roller 11. As shown in FIGS. 2B and 2C, the shape of the adhesive material 8 formed on the insulating paper 7 can be linear, wavy, or dotted.

  The insulating paper 7 is attached to the separator 6 so as to cover the lead terminals 4 and 5 connected to the electrode foil so that the space between the lead terminals 4 and 5 and the opposite electrode foil is doubled. . The insulating paper 7 may be attached to both sides of the separator 6 or may be attached only to one side. When the rated voltage of the electrolytic capacitor is high, insulating paper 7 may be attached to both surfaces of the separator 6 in order to ensure insulation between the electrode foils. It is preferable to provide the insulating paper 7 only on one side. The insulating paper 7 is preferably attached to the surface of the lead terminals 4 and 5 connected to the electrode foil of the separator 6. This is because the separator 6 is protected by the insulating paper 7, and it is possible to prevent the breakdown voltage characteristics and insulation properties inherent to the separator 6 from being damaged due to damage to the separator 6 or the like. In addition, since the insulating paper 7 has a surface 10 on the concave-convex side in contact with the lead terminals 4, 5, the concave-convex surface 10 is maintained filled with the driving electrolyte solution. The characteristics can be maintained.

Here, the peel strength of the insulating paper 7 attached to the separator 6 will be examined. This examines the adhesive strength that does not cause the displacement of the insulating paper 7 when the separator 6 is wound together with the electrode foil or formed into an element by a laminating device, thereby optimizing the application amount of the adhesive material. It is intended. Conventionally, an adhesive was formed on the surface 10 on the concave and convex side of the insulating paper 7 and applied to the entire surface, and the peel strength was about 70 to 150 g / cm ² . Here, it was found that the peel strength capable of maintaining the necessary adhesive state was 5 to 30 g / cm ² , and it was found preferable to reduce the coating amount of the adhesive material within a range where this strength can be obtained.

  Next, the electrolytic capacitor in the present invention will be specifically described. It should be noted that the scope of the present invention is not limited by these examples, and materials, amounts used, ratios, operations, and the like in the examples can be changed as appropriate without departing from the spirit of the present invention.

Example 1
As the anode foil 2, a strip-shaped metal foil having an etching layer and an oxide film layer formed on the surface by etching and conversion treatment on the surface of the aluminum is etched, and the surface of the metal foil made of aluminum is etched and etched as the cathode foil 3. A band-shaped metal foil having a layer formed thereon was used. One end of strip-shaped lead terminals 4 and 5 is connected to the cathode foil 3 and the anode foil 2 by ultrasonic welding. A separator 6 made of Manila hemp paper is interposed between the cathode foil 3 and the anode foil 2, and a manila hemp paper having a density of 0.5 g / cm 3 at a portion corresponding to the lead-out terminal 4 on the anode side of the separator 6. An insulating paper 7 made of is attached to the surface 9 on the flat side of the insulating paper 7 with an acrylic pressure-sensitive adhesive material applied linearly by a doctor blade method. The application area of the adhesive material is 3% with respect to the foil area of the anode foil 2. The insulating paper 7 is affixed to the surface of the separator 6 on the anode-side lead-out terminal side. The anode foil 2 and the cathode foil 3 are wound to form a capacitor element 1, impregnated with a driving electrolyte, and housed in a bottomed cylindrical outer case made of aluminum, with an opening end made of rubber. Sealed with a sealing body. The electrolytic capacitor of Example 1 has an anode foil area of 880 cm ² and an insulating paper area of 65 cm ^{2 in} total ( ^two anode side lead terminals: 32.5 cm ² × 2, no cathode side lead terminal) The total area of the adhesive 8 is 26 cm ² (insulating paper 4 locations: 13.0 cm ² × 2).

(Comparative Example 1)
In the electrolytic capacitor of Example 1, instead of the flat side of the Manila hemp paper, the acrylic adhesive material 8 is intermittently applied to the surface of the uneven side, and the application area of the acrylic adhesive material 8 is the anode foil 3% with respect to the foil area.

(Conventional example 1)
In the electrolytic capacitor of Example 1, the acrylic adhesive material 8 is applied over almost the entire surface of the uneven side of the Manila hemp paper, and the application area of the acrylic adhesive material 8 is relative to the foil area of the anode foil. 15%.

  Ten pieces of each of Example 1, Comparative Example 1 and Conventional Example 1 of the present invention were prepared, and the ESR characteristics for each frequency under 20 ° C. conditions were measured. FIG. 4 is a graph showing ESR characteristics at 20 ° C. in the frequency domain.

  FIG. 4 shows that the ESR characteristic in the low frequency region of the electrolytic capacitor of Example 1 of the present invention is greatly improved. This is considered that the application amount of the adhesive material could be reduced by intermittently applying the adhesive material to the insulating paper and applying the adhesive material to the flat surface of the insulating paper.

Next, the ESR characteristic was measured by changing the application area of the adhesive material applied to the insulating paper of the electrolytic capacitor and changing the foil area of the anode foil. Here, Manila hemp paper is used as the insulating paper, and an acrylic adhesive material is intermittently applied to the flat surface of the insulating paper. The foil area of the anode foil instead between 10cm ² ~200cm ^2, the area of the insulating paper and 3 cm ^2, and the coating area of the applied adhesive on the surface of the flat side of the insulating sheet and 2 cm ^2. ESR was measured at 20 ° C. and 120 Hz. FIG. 5 is a graph showing the area of the adhesive material and the ESR characteristic with respect to the anode foil area.

  FIG. 5 shows that the ESR in the low frequency region is better as the application area of the adhesive material applied to the insulating paper is smaller. In particular, when the application area of the pressure-sensitive adhesive exceeds 6%, it turns out that it deteriorates rapidly. If it is 6% or less, good results are obtained. The smaller the application area, the better. However, if it is 3% or less, the ESR increases. In view of the adhesive strength of the insulating paper to the separator, the application area of the adhesive material is preferably 0.5% or more.

It is a perspective view which shows the winding state of the electrolytic capacitor in embodiment of this invention. (A) is sectional drawing which shows the arrangement | positioning state of the anode foil in the embodiment of this invention, an anode extraction terminal, a separator, and insulating paper. (B) is drawing which shows the insulating paper affixed on the separator in the form of the Example of this invention. (C) is drawing which shows the insulating paper affixed on the separator in other embodiment of this invention. It is drawing which shows the formation process of the adhesive material to the insulating paper in the Example of this invention. It is a graph which shows the ESR characteristic in 20 degreeC in a frequency domain. It is a graph which shows the area and ESR characteristic of the adhesive material with respect to an anode foil area.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode foil 3 Cathode foil 4 Extraction terminal 5 on the anode side Extraction terminal 6 on the cathode side Separator 7 Insulating paper 8 Adhesive material 9 Surface on the flat side of the insulating paper 11 Surface on the uneven side of the insulating paper 11 Rotating roller 12 Doctor Blade 13 Tank 14 Etching recess 15 Elastic roller

Claims (1)

In an electrolytic capacitor having a capacitor element in which a separator is interposed between a cathode foil and an anode foil each connected to a lead terminal, the separator is a part corresponding to the lead terminal and insulated from the lead terminal. Paper is arranged, and this insulating paper is formed with one of the front and back surfaces being a flat surface and the other being a concavo-convex surface. On the flat surface , the coating area is 6 to the foil area of the anode foil. An electrolytic capacitor characterized in that an adhesive material of% to 0.5% is intermittently formed on the surface of insulating paper and stuck to the separator, and the surface on the uneven side is in direct contact with the lead terminal.