JP5219631B2 - Electrolytic capacitor manufacturing method - Google Patents

Description

  The present invention relates to an electrolytic capacitor in which an electrode foil whose surface has been subjected to surface expansion treatment and a tab terminal whose surface has been subjected to surface expansion treatment are joined by a joint formed by cold pressing, and such an electrolytic capacitor. The present invention relates to a manufacturing method for manufacturing.

  The electrolytic capacitor is configured such that a capacitor element formed by winding a separator paper between an anode foil and a cathode foil is housed in a case. From the sealing body that seals the opening of the case, an anode terminal and a cathode terminal connected to the anode foil and the cathode foil of the capacitor element via tab terminals respectively protrude.

  The surfaces of the anode foil and the cathode foil are etched for a surface expansion treatment for increasing the surface area. By performing the etching, the surface of each electrode foil is roughened and widened, and the capacitance of the capacitor can be increased.

  Each tab foil connected to each of the anode terminal and the cathode terminal is attached to each electrode foil subjected to the surface enlargement treatment. Each tab terminal is generally fixed by cold pressing (cold weld method) (see, for example, Patent Document 1).

In addition, the conventional tab terminal is generally not subjected to the surface expansion process by etching, and the portion where the tab terminal is attached is a portion that does not contribute much to the capacitance. Thus, it has been proposed to use a tab terminal that has been subjected to surface enlargement processing (see, for example, Patent Document 2 and Patent Document 3).
Thus, by using the tab terminal subjected to the surface expansion treatment, the capacitance of the tab terminal with respect to the electrode foil can be added, so that the capacity of the entire electrolytic capacitor can be increased.

Here, FIG. 7 shows a conventional convex type and flat type configuration used for cold pressure bonding in which a tab terminal is joined to an electrode foil.
Each of the convex mold 10 and the flat mold 11 is made of a press workable metal, and is provided in a press apparatus (not shown).
The shape of the convex mold 10 is an ellipse when viewed in plan, and is formed in a trapezoidal shape that gradually narrows toward the tip when viewed from the side. Further, the tip portion 10 a of the convex mold 10 is formed in a planar shape, and the tip portion 10 a formed in the planar shape comes into contact with the electrode foil 9.

  The electrode foil 9 and the tab terminal 8 are overlapped and arranged between the convex mold 10 and the flat mold 11. Here, the electrode foil 9 is disposed on the convex mold 10 side, and the tab terminal 8 is disposed on the flat mold 11 side. When the pressing device operates and the convex mold 10 moves in the direction of the flat mold 11, the electrode foil 9 and the tab terminal 8 are pressed and pressure-bonded by the convex mold 10.

JP 2007-273645 A Japanese Patent No. 2773217 Japanese Patent No. 3457222

When a tab terminal subjected to surface expansion treatment as described above is attached to the electrode foil by cold pressing, the tab terminal subjected to surface expansion treatment itself becomes an electrode, and an electrostatic capacity is generated between the opposing electrode foils as a whole. An electrolytic capacitor having a large capacity can be obtained.
However, a charge / discharge test was performed using the electrolytic capacitor using the tab terminals subjected to the surface expansion treatment in this manner, and after repeating the charge / discharge 50 million times, the electrolytic capacitor was disassembled. As a result, the cathode tab terminal turned brown. It became clear that In addition, it was confirmed that there was a spark trace in which a large current flowed suddenly in the discolored portion.
Thus, the occurrence of sparks is considered to be caused by a short circuit between the anode foil and the cathode tab terminal. If a short circuit cannot be prevented between the anode foil and the cathode tab terminal, there is a problem that the electrolytic capacitor may be damaged.

The principle of occurrence of a short circuit is assumed to be due to the following reason.
FIG. 8 shows a conventional configuration after cold-bonding the tab terminal subjected to the surface expansion treatment to the electrode foil.
The tab terminal 8 and the electrode foil 9 pressed by the convex mold 10 are fixed by forming a joint portion 12 in a welded state.
In the joint portion 12, the internal portion of the tab terminal 8 is pushed out to the surface of the tab terminal 8 by plastic flow, and a non-surface expansion processing portion 14 that is not subjected to surface expansion processing is formed on the surface of the tab terminal 8. That is, when the tab terminal 8 subjected to the surface expansion process is cold-bonded, a non-surface expansion processing unit 14 that has not been subjected to the surface expansion process is generated. The fluctuation tends to concentrate the current, which may cause a short circuit.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrolytic capacitor having a tab terminal that has been subjected to surface expansion treatment, and an electrolytic capacitor that does not cause a short-circuit in the tab terminal even after repeated charging and discharging. It is to provide a manufacturing method.

According to the electrolytic capacitor manufacturing method of the present invention, the electrode foil whose surface is enlarged and the tab terminal whose surface is enlarged are overlapped, and the overlapped electrode foil and the tab terminal are overlapped. A convex shape having a convex portion to be pressed and disposed on one side of the electrode foil or the tab terminal, and disposed on either side of the electrode foil or the tab terminal so as to face the convex shape In the manufacturing method of manufacturing the electrolytic capacitor by joining the electrode foil and the tab terminal by cold pressure bonding by relatively moving the convex type or the flat type using the flat type The convex portion is a quadrangular pyramid, and is configured to have a curved shape in which the edge of the cross section of the top portion of the convex portion that contacts the electrode foil or the tab terminal is convex upward, and the inclined surface of the convex portion At the part rising from the base of the convex part That, used as the edges of the cross section of the skirt is formed in a curved shape that is convex downward, surface formed at the junction of the tab terminal to surface enlargement treated electrode foil and the surface is subjected to surface enlargement treatment It is characterized in that it is cold-bonded so as to reduce the area of the non-surface-enlarged processing portion.
According to this method, the tab terminal and the electrode foil are securely fixed, and the area of the non-surface-enlarging processing portion can be reduced, so that the tab terminal is prevented from being short-circuited even after repeated charging and discharging. it can. The tab terminal of the present invention is formed in a foil shape.
Moreover, since the edge of the cross section of the skirt is curved, the plastic deformation of the electrode foil is moderated during the cold press bonding, and the foil breakage can be suppressed.

Further, the top of the convex portion may be characterized in that the cross-sectional edge is arcuate.
Furthermore, the said convex part is good also as a square shape when planarly viewed. By using such a convex shape, the area of the joint portion can be reduced, and consequently the area of the non-surface-enlarged processing portion can be reduced. In addition, it is possible to prevent the convex mold from sticking to the electrode foil and the tab terminal after pressing, to improve the releasability and to prevent the electrode foil from being cut (so-called foil cutting).

Also, the skirt portion of the protruding portion may be characterized in that edges of the cross-section is arcuate.

  In addition, the said convex type is arrange | positioned at the said electrode foil side, and may press the electrode foil and tab terminal which were piled up from the electrode foil side. According to such a method, it is possible to increase the peel strength and to improve the releasability.

  According to the electrolytic capacitor manufacturing method and the electrolytic capacitor of the present invention, it is possible to prevent a short circuit from occurring in a tab terminal even when charging and discharging are repeated.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.
FIG. 1 shows the overall configuration of the electrolytic capacitor of this embodiment.
In the electrolytic capacitor 30 of this embodiment, a capacitor element 32 is disposed inside a bottomed cylindrical outer case 31 formed of a metal such as aluminum, and the opening of the outer case 31 is sealed with a rubber-laminated laminated resin plate. 34 is closed.
The outer case 31 is covered with a sleeve 35 on which a performance indication of the capacitor is printed.

FIG. 2 shows the structure of the capacitor element.
The capacitor element 32 is configured by winding an anode foil 38, a cathode foil 39, and a separator paper 37 impregnated with an electrolytic solution, disposed between the anode foil 38 and the cathode foil 39.

  Anode terminal 42 and cathode terminal 43 are connected to anode foil 38 and cathode foil 39 via anode tab terminal 40 and cathode tab terminal 41, respectively. The anode terminal 42 and the cathode terminal 43 are disposed so as to protrude from the opening of the outer case 31.

As the anode foil 38, an aluminum foil whose surface has been enlarged by etching is used. Further, the etched anode foil 38 is further subjected to a chemical conversion treatment to form an oxide film on the surface subjected to the surface expansion treatment.
Similarly to the anode foil 38, the cathode foil 39 is made of an aluminum foil that has been subjected to a surface expansion treatment by etching, but the surface that has been subjected to the surface expansion treatment need not be subjected to a chemical conversion treatment to form an oxide film.

The tab terminal 40 for anode fixed to the anode foil 38 may also use an aluminum plate material subjected to surface expansion treatment by etching. The etched anode tab terminal 40 is subjected to a chemical conversion treatment to form an oxide film on the surface-enlarged surface.
The tab terminal 41 for the cathode fixed to the cathode foil 39 is also made of an aluminum plate material that has been subjected to surface expansion treatment by etching, but the surface that has been subjected to surface expansion treatment need not be subjected to chemical conversion treatment to form an oxide film. Good.
Thus, by performing the surface enlargement process by etching the cathode tab terminal, the cathode tab terminal 41 can also have a sufficient capacitance with respect to the opposing anode foil 38.

A structure for attaching the cathode tab terminal 41 to the cathode foil 39 in this embodiment will be described with reference to FIG.
The cathode tab terminal 41 and the cathode foil 39 are attached by a joint 44 formed by cold pressure bonding. The joining portions 44 are formed at a plurality of locations, and are joined using a convex mold having a plurality of convex portions as will be described later. In the joining portion 44, the cathode tab terminal 41 and the cathode foil 39 are joined in a pressure-bonded state, and the non-surface-enhanced processing portion that is a portion that is not subjected to the surface-enlarging treatment in each of the locations that are in the crimped state. 46 is formed.

  The non-surface-enlarging portion 46 is a portion formed by extruding an internal portion of the cathode tab terminal 41 that has not been subjected to surface expansion treatment to the surface of the cathode tab terminal 41 by plastic flow. Since it is not processed, it is a part which does not have sufficient capacitance as an electrode.

A method for attaching the cathode tab terminal to the cathode foil will be described with reference to FIG.
As described above, the cathode tab terminal 41 and the cathode foil 39 are attached by cold pressure bonding. Cold pressure bonding is performed by relatively moving a convex mold 50 and a flat mold 51 provided in a pressing device (not shown).
In the present embodiment, the convex mold 50 is disposed on the lower side and the flat mold 51 is disposed on the upper side. The convex mold 50 is raised with respect to the flat mold 51, and press working is performed.

In the present embodiment, only one convex portion 52 is formed on the convex mold 50, but a plurality of convex portions 52 may be formed on one convex mold 50.
As for the convex part 52, when joining the cathode foil 39 and the cathode tab terminal 41 like this embodiment, it is good to use that whose inclination | tilt angle (alpha) is 40 degrees-50 degrees. In particular, the inclination angle α is preferably 45 °. By doing in this way, it can respond to the cathode foil 39 of various thickness, maintaining the predetermined peeling strength for the cathode foil 39 and the tab terminal 41 for cathodes.
In addition, the inclination angle α of the convex portion 52 refers to the maximum angle formed by the inclined surface 52b of the convex portion 52 and the base surface 52c of the convex portion 52.

  On the other hand, if it is the convex part 52 used when joining the anode foil 38 and the tab terminal 40 for anodes, it is good to use that whose inclination | tilt angle (alpha) is 55 degrees-65 degrees. In particular, the inclination angle α is preferably 60 °. Since the anode foil 38 is thicker than the cathode foil 39, the inclination angle α of the convex portion 52 needs to be larger than when the cathode foil 39 and the cathode tab terminal 41 are joined. is there. Then, by using the convex mold 50 having such a convex portion 52, it is possible to cope with anode foils 38 having various thicknesses while maintaining a predetermined peel strength.

A cathode foil 39 and a cathode tab terminal 41 are disposed between the convex mold 50 and the flat mold 51. The cathode tab terminal 41 is overlaid on the cathode foil 39.
Thus, in this embodiment, the convex mold 50, the cathode foil 39, the cathode tab terminal 41, and the flat mold 51 are arranged in this order from the bottom. When the convex mold 50 is raised, the convex portion 52 of the convex mold 50 presses the cathode foil 39 toward the cathode tab terminal 41 and cold-compresses the cathode foil 39 and the cathode tab terminal 41. By doing in this way, while being able to raise peeling strength, the mold release property at the time of manufacture can also be made favorable.

The top portion 52a of the convex portion 52 is formed in a curved shape in which the edge of the cross section is convex upward. Specifically, the top portion 52a of the convex portion 52 has an arc shape in which the edge of the cross section has a predetermined radius of curvature.
Furthermore, the skirt portion 52d of the convex portion 52 (the portion where the inclined surface 52b of the convex portion 52 rises from the base surface 52c of the convex portion 52) is formed in a curved shape in which the edge of the cross section is convex downward. Specifically, the skirt portion 52d of the convex portion 52 has an arc shape in which the edge of the cross section has a predetermined radius of curvature.

FIG. 5 shows a plan view of the convex portion 52.
Thus, the convex part 52 is formed in the square shape when planarly viewed. Specifically, it is good to form in a square. In this way, by forming the convex portion 52 in a square shape in plan view, the area of the joint portion 44 can be made as small as possible, and the area of the non-surface-enlarging processing portion can be reduced as much as possible. Further, it is possible to prevent the convex mold from sticking to the electrode foil and the tab terminal after pressing, to improve the releasability and to prevent foil breakage.

FIG. 6 shows a cross-sectional shape of a joint formed using such a convex mold.
Since the convex portion 52 is formed by pressing the cathode foil 39 toward the cathode tab terminal 41 side of the bonding portion 44 in the present embodiment, the concave portion 55 is recessed from the cathode foil 39 side toward the cathode tab terminal 41 side. Is formed. The bottom 55a (tip in the width direction) of the recess 55 is formed so that the edge of the cross section is curved. In addition, by forming the edge of the cross section of the top portion 52a of the convex portion 52 in an arc shape having a predetermined radius of curvature, the edge of the cross section of the bottom portion 55a of the concave portion 55 is also formed in an arc shape having a predetermined radius of curvature.
And the non-surface-enlargement process part 46 formed in the tab terminal 41 side for cathodes is formed very small compared with the case where it presses with the planar convex part like the past.

  As described above, by making the cross-section of the top portion 52a of the convex portion 52 into a curved surface shape, the area of the non-surface expansion processing portion 46 having a smaller electrostatic capacity than the peripheral portion subjected to the surface expansion processing can be reduced. it can. As a result, voltage fluctuations with the surrounding area subjected to the surface enlargement process can be reduced, current concentration can be prevented, and short-circuiting of the tab terminal can be prevented even when charging and discharging are repeated.

  In addition, it is guessed that the reason why the area of the non-surface-enlargement processing unit 46 is small is as follows. That is, when pressed at the flat portion as in the prior art, the pressed portion of the cathode foil 39 flows to the cathode tab terminal 41 side as it is. However, when pressed at the curved surface portion as in the present invention, the pressed portion of the cathode foil 39 flows laterally inside the cathode foil 39 rather than the cathode tab terminal 41 side (arrow in FIG. 7). ) And the amount pushed out to the cathode tab terminal 41 side is reduced. Therefore, it is considered that the non-surface-expansion processing portion 46 formed on the cathode tab terminal 41 side can be reduced.

An experiment was conducted in which a cathode tab terminal having a thickness of 200 μm was joined to a cathode foil having a thickness of 20 μm, with the tip of the convex portion having a curvature radius of 0.25 mm and a pressing pressure in the range of 1.9 MPa to 2.7 MPa.
As a result, it was confirmed that the present standard for the peel strength was satisfied, and that the area of the non-surface-expanded portion could be made extremely small compared to the conventional one.

  In the embodiment described above, only the structure of the cathode tab terminal has been described. However, the present invention is not limited to the cathode tab terminal, and the structure of the above-described embodiment may be applied to the structure of the anode tab terminal.

  Note that either the convex mold or the flat mold used for cold pressure bonding may be disposed above or below, and either may be provided so as to be movable.

  While the present invention has been described above with reference to a preferred embodiment, the present invention is not limited to this embodiment, and it goes without saying that many modifications can be made without departing from the spirit of the invention. .

It is sectional drawing from the side of the electrolytic capacitor concerning this invention. It is a perspective view of a capacitor element. It is explanatory drawing which shows the attachment structure of the tab terminal for cathodes, and cathode foil. It is a side view which shows the convex type and flat type which are used for cold press bonding. It is a top view of a convex type. It is sectional drawing of the junction part after cold-pressing. It is a side view which shows the conventional convex type and a flat type. It is sectional drawing of the conventional junction part.

Explanation of symbols

30 Electrolytic Capacitor 31 Outer Case 32 Capacitor Element 34 Sealing Body 35 Sleeve 37 Separator Paper 38 Anode Foil 39 Cathode Foil 40 Anode Tab Terminal 41 Cathode Tab Terminal 42 Anode Terminal 43 Cathode Terminal 44 Joint Portion 46 Non-Expanded Surface Treatment Portion 50 Convex type 51 Flat type 52 Convex part 52a Top part 52b Inclined surface 52c Base surface 55 Concave part

Claims (6)

The electrode foil whose surface is expanded and the tab terminal whose surface is expanded are superimposed,
A convex shape that has a convex portion that presses the electrode foil and the tab terminal that are overlaid, and is disposed on one side of the electrode foil or the tab terminal, and either the electrode foil or the tab terminal. The electrode foil and the tab terminal are cold-removed by using a flat mold disposed opposite to the convex mold on the other side and moving the convex mold or the flat mold relative to each other. In a manufacturing method of manufacturing an electrolytic capacitor by joining by crimping,
As the convex part,
A quadrangular pyramid,
The edge of the cross section of the top portion that contacts the electrode foil or the tab terminal of the convex portion is configured in a curved shape that is convex upward ,
The slope of the convex part is a part that rises from the base surface of the convex part, and the edge of the cross section of the bottom part is formed in a curved shape that is convex downward,
An electrolytic capacitor characterized in that it is cold-bonded so as to reduce the area of a non-surface-enlarging portion formed at a joint between an electrode foil whose surface is expanded and a tab terminal whose surface is expanded. Manufacturing method.   The method for manufacturing an electrolytic capacitor according to claim 1, wherein an edge of a cross section of the top of the convex portion has an arc shape.   The method for manufacturing an electrolytic capacitor according to claim 1, wherein the convex portion has a square shape when seen in a plan view. 4. The method for manufacturing an electrolytic capacitor according to claim 1, wherein the skirt of the convex portion has an arcuate cross section. 5. The said convex type is arrange | positioned at the said electrode foil side, and presses the electrode foil and tab terminal which were piled up from the electrode foil side, The any one of Claims 1-4 characterized by the above-mentioned. Manufacturing method of the electrolytic capacitor. Inclination angle of the convex portion to be used when bonding the tab terminals for the anode foil and the anode, wherein, characterized in that the larger than the inclination angle of the convex portion to be used when joining and the cathode tab terminal cathode foil The manufacturing method of the electrolytic capacitor of any one of Claims 1-5 .

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