JP2022040754A - Electrolytic capacitor - Google Patents

Abstract

To suppress the occurrence of corrosion in a lead tab of an electrolytic capacitor.SOLUTION: An electrolytic capacitor includes: a capacitor element obtained by laminating, via a separator, an anode foil which is made of valve metal and to which a first lead tab is connected and a cathode foil to which a second lead tab is connected and winding the laminated anode and cathode foils; protective paper covering at least a portion of the first lead tab, the portion protruding from the anode foil; a bottomed cylindrical exterior case storing the capacitor element therein; and a sealing body sealing an opening of the exterior case.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrolytic capacitor and to an electrolytic capacitor in which a lead tab is connected to an electrode foil.

Conventionally, as an electrolytic capacitor, a capacitor element in which an anode foil and a cathode foil are wound via a separator, a bottomed tubular capacitor case for accommodating the capacitor element, and a sealing body for closing the open end side of the capacitor case. Those with and are known. Anode terminals and cathode terminals are drawn out from the outer end surface of the sealing body, and anode lead tabs and cathode lead tabs as anode internal terminals and cathode internal terminals are connected to the anode foil and the cathode foil, respectively, at the base ends of these terminals. (See Patent Document 1).

Further, as a conventional electrolytic capacitor, an insulating paper is attached to the connection portion between the lead tab and the anode foil to protect the connection portion of the lead tab (see Patent Document 2). This makes it possible to prevent short-circuit defects due to tearing of the separator.

Japanese Unexamined Patent Publication No. 04-352313 Japanese Unexamined Patent Publication No. 2006-286959

However, in the conventional electrolytic capacitor, there is a problem that leakage current is generated due to the presence of the condensed liquid generated by the evaporation of the electrolytic liquid, and the lead tab on the anode side is corroded.

An object of the present invention is to provide an electrolytic capacitor capable of suppressing the occurrence of corrosion in a lead tab.

The electrolytic capacitor of the present invention comprises a capacitor element formed by superimposing and winding an anode foil of a valve metal to which a first lead tab is connected and a cathode foil to which a second lead tab is connected via a separator. A protective paper covering at least a portion of the first lead tab protruding from the anode foil, a bottomed cylindrical outer case for accommodating the capacitor element, and a sealing body for sealing the opening of the outer case. It is characterized by having.

According to this configuration, by covering at least the portion of the first lead tab protruding from the anode foil with a protective paper, it is possible to suppress the occurrence of corrosion caused by the adhesion of the condensed liquid generated by the evaporation of the electrolytic solution. ..

Further, in the electrolytic capacitor of the present invention, in the above configuration, the protective paper covers the first protective paper covering the front surface side on which the first lead tab of the anode foil is stacked and the back surface side of the anode foil. It is characterized by being composed of a second protective paper.

According to this configuration, the first lead tab is covered with the first protective paper covering the front surface side on which the first lead tab of the anode foil is stacked and the second protective paper covering the back surface side of the anode foil. Therefore, the occurrence of corrosion can be suppressed more effectively.

Further, in the electrolytic capacitor of the present invention, in the above configuration, the first lead tab has a flat portion connected to the anode foil and a round bar portion inserted into an insertion hole provided in the sealing body. The round bar portion is characterized in that the lead wire is welded to the round bar portion, and the protective paper covers the lead wire in a range of at least 0.5 times the length of the round bar portion and the round bar portion. do.

According to this configuration, it is possible to suppress the occurrence of corrosion without causing any trouble when the round bar portion is inserted into the insertion hole of the sealing body.

According to the electrolytic capacitor of the present invention, the occurrence of corrosion in the lead tab can be suppressed.

It is sectional drawing which shows the structure of the electrolytic capacitor which concerns on embodiment of this invention. It is a perspective view which shows the capacitor element which concerns on embodiment of this invention. It is a side view which shows the sticking range of the protective paper which concerns on embodiment of this invention. It is a schematic diagram provided for the explanation of the chemical conversion treatment of the lead tab which concerns on embodiment of this invention. It is sectional drawing which provides the explanation of the sticking method of the protective paper which concerns on embodiment of this invention. It is a perspective view which shows the sticking state of the protective paper which concerns on embodiment of this invention. It is a perspective view provided for the explanation of the method of sticking the protective paper which concerns on other embodiment of this invention. It is a perspective view which shows the sticking state of the protective paper which concerns on other embodiment of this invention. It is a perspective view which shows the sticking state of the protective paper which concerns on other embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, the wound electrolytic capacitor 1 in the present embodiment is mainly composed of a capacitor element 2, an exterior case 12, and a sealing body 11.

As shown in FIG. 2, in the capacitor element 2, the anode foil (anodic aluminum foil) 3a and the cathode foil (cathode aluminum foil) 3b, which have been subjected to the etching treatment and the dielectric oxide film forming treatment, are wound via the separator 4. It is turned and fixed with the element stop tape 9 (FIG. 1). The capacitor element 2 is housed in a bottomed cylindrical outer case 12 (FIG. 1).

A sealing body 11 made of resin, rubber, or the like is attached to the opening of the outer case 12, and the opening has a structure sealed by drawing.

Lead wires 6 and 16 are welded to the lead tabs 5 and 15 drawn out from the capacitor element 2, and are drawn out to the outside through the sealing body 11. The outer case 12 is covered with a sleeve 13.

The lead tab 5 is a lead tab on the anode side connected to the anode foil 3a by a method such as crimping or welding, and the lead tab 15 is a cathode connected to the cathode foil 3b by a method such as crimping or welding. The lead tab on the side.

The lead tab 5 connected to the anode foil 3a is covered with protective papers 41 and 42 to suppress the occurrence of corrosion. Specifically, as shown in FIG. 3, the lead tab 5 on the anode side has a round bar portion 5a protruding from the end face on the sealing body side of the capacitor element 2 (FIG. 2) (that is, protruding from the anode foil 3a) and the round bar portion 5a. It is formed at one end of the round bar portion 5a and is composed of a flat portion 5b to which the anode foil 3a is connected.

As described above, the lead tab 5 is formed by pressing one end of a round bar-shaped member made of aluminum by a predetermined length to form a flat portion 5b, and the remaining portion being a round bar portion 5a. ..

A lead wire 6 is welded to the tip of the round bar portion 5a (the end opposite to the flat portion 5b).

Further, the lead tab 15 on the cathode side also has a round bar portion 15a (FIG. 2) protruding from the end face on the sealing body side of the capacitor element 2 (that is, protruding from the anode foil 3a) and this circle, similarly to the lead tab 5 on the anode side. It is formed at one end of the rod portion 15a, and is composed of a flat portion (not shown) to which the cathode foil 3b is connected by crimping.

As described above, the lead tab 15 is formed by pressing one end of a round bar-shaped member made of aluminum by a predetermined length to form a flat portion, and forming the remaining portion as the round bar portion 15a.

A lead wire 16 is welded to the tip of the round bar portion 15a (the end opposite to the flat portion 15b).

In the present embodiment, the lead tab 5 on the anode side having such a configuration is covered with a protective paper to prevent corrosion of the lead tab 5 from occurring. Specifically, a protective paper 41 having a predetermined size is adhered to the surface (hereinafter referred to as the surface) to which the lead tab 5 of the anode foil 3a is connected so as to cover the round bar portion 5a and the flat portion 5b. Further, a protective paper 42 having a predetermined size is attached to the back surface side (hereinafter referred to as the back surface) of the side surface to which the lead tab 5 of the anode foil 3a is connected by an adhesive.

The protective paper is a paper made by alone or by blending Manila paper, kraft paper, esparto paper, recycled cellulose and the like, and may be made of the same material as the separator or a different material.

As shown in FIG. 4, the size of the protective paper 41 is such that it covers the round bar portion 5a and the flat portion 5b of the lead tab 5 and a part of the lead wire 6, and is round with respect to the lead wire 6. The size is such that the lead wire 6 can be covered within a range of up to 0.5 times the length L1 of the rod portion 5a (length L2 in FIG. 4).

In this way, by setting the size so that at least the entire round bar portion 5a (length L1) can be covered, it is possible to prevent a portion of the round bar portion 5a that is not covered by the protective paper 41 from being generated. That is, since the round bar portion 5a protrudes from the anode foil 3a, assuming that the entire round bar portion 5a is not covered with the protective paper 41, the exposed portion is condensed due to the evaporation of the electrolytic solution. Liquid accumulates and causes corrosion. Therefore, by setting the size of the protective paper 41 to be such that it can cover at least the entire round bar portion 5a (length L1), corrosion of the round bar portion 5a is suppressed. be able to.

Further, as the upper limit of the size of the protective paper 41, the size of the round bar portion 5a is set so as to cover the lead wire 6 with a length L2 that is 0.5 times the length L1 of the round bar portion 5a. This is because it is necessary to keep the size of the portion of the lead wire 6 covered by the protective paper 41 so as not to hinder the insertion through the insertion hole provided in the sealing body 11.

In this embodiment, a part of the flat portion 5b of the lead tab 5 protrudes from the anode foil 3a, and this part is also covered with the protective papers 41 and 42.

Further, in the case of the present embodiment, the size of the protective paper 42 attached to the back surface side is the same as the size of the protective paper 41 attached to the front surface side, and at least the entire round bar portion 5a may be covered. You can do it.

By attaching protective papers 41 and 42 having such sizes to the front surface and the back surface of the anode foil 3a to which the lead tab 5 is connected (FIG. 5A), the anode foil 3a and the lead tab 5 are covered so as to be sandwiched between them. Can be done (Fig. 5 (b)).

Thus, as shown in FIG. 6, the anode foil 3a and the lead tab 5 are covered with the protective papers 41 and 42. In this state, the round bar portion 5a can be inserted through the insertion hole of the sealing body 11. Since it is difficult, the protective papers 41 and 42 around the round bar portion 5a and the lead wire 6 are rolled along the shape of the round bar portion 5a and the lead wire 6 or cut along the shape to be shown in FIG. As shown, the coated state can be formed along the shapes of the round bar portion 5a and the lead wire 6, and this can be easily inserted into the insertion hole of the sealing body 11.

Next, the manufacturing process of the electrolytic capacitor 1 will be described.
Lead tabs 5 and 15 (made of aluminum) for external lead-out electrodes are crimped and connected to the anode foil 3a (anode aluminum foil) and the cathode foil 3b (cathode aluminum foil) cut to a predetermined width. As the anode foil 3a, an aluminum foil is used as the valve metal, and a dielectric oxide film formed by subjecting the surface of the valve metal to an etching treatment and a chemical conversion treatment is used. Further, as the cathode foil 3b, an aluminum foil is used as in the anode foil 3a, and the surface of the aluminum foil is etched and a natural oxide film is formed. The cathode foil 3b may also be formed with a dielectric oxide film, or carbon, titanium, titanium nitride, titanium carbide or the like may be formed on the surface thereof. The anode foil 3a and the cathode foil 3b to which the above-mentioned protective papers 41 and 42 are attached in FIGS. 3 to 6 are wound around the separator 4 mainly made of cellulose to produce a capacitor element 2.

Then, the capacitor element 2 impregnated with the electrolyte was housed in an aluminum metal case (exterior case 12), and the opening of the outer case 12 was curled and sealed. The electrolyte includes both an electrolytic solution containing ethylene glycol, γ-butyrolactone, etc. as the main solvent and dissolving the electrolyte, and a solid electrolyte containing a conductive polymer such as polyethylene dioxythiophene / polystyrene sulfonic acid as the main component and an electrolytic solution. Can be used. After that, in a constant temperature bath set to a predetermined temperature, a rated voltage is applied to an aluminum electrolytic capacitor (electrolytic capacitor 1) in which a capacitor element 2 is housed in an outer case 12, and an aging process is performed to manufacture the electrolytic capacitor 1. End the process.

Hereinafter, the present invention will be described in more detail with reference to examples.

The aluminum lead tab is crimped and connected to the anode aluminum foil, and the aluminum lead tab is crimped and connected to the cathode aluminum foil. Then, the protective paper is attached to the lead tab on the anode side and the anode foil, the anode aluminum foil and the cathode aluminum foil are overlapped with each other via the separator, and the wound aluminum electrolytic capacitor element is impregnated with the electrolytic solution. Then, after inserting the round bar portions of the lead tab on the anode side and the lead tab on the cathode side drawn out from the aluminum electrolytic capacitor element through the insertion holes of the sealing body, the aluminum electrolytic capacitor element is inserted into the outer case together with the sealing body. do. Next, the opening of the outer case is curled and the outer peripheral surface is drawn and sealed. As a result, an aluminum electrolytic capacitor with a rating of 400V / 150μF (external dimensions: diameter φ18mm x length 40mm aluminum electrolytic capacitor) was manufactured, and the rated voltage (400V) was applied in an environment of 115 ° C, which exceeds the category upper limit temperature. In this case, the time until corrosion occurred on the lead tabs on the anode side (flat portion 5b and round bar portion 5a protruding from the anode foil) was measured. The occurrence of corrosion means a state in which adhesion of corrosion products or dissolution of aluminum is observed. The measurement results are shown in Table 1.

(Example 1)
In the first embodiment, when the protective paper is attached only to the surface of the anode foil 3a (that is, only the protective paper 41 on the front surface side of the anode foil 3a in FIG. 3 is used as the flat portion 5b, the round bar portion 5a, and the lead wire of the lead tab 5. It is the result of measuring the corrosion occurrence time in the case where it is attached to the anode foil 3a so as to cover a part of No. 6 (L1 is 4.0 mm, L2 is 0.5 mm), and the lead tab 5 is corroded in 4000 to 4500 hours. Occurred.

(Example 2)
In the second embodiment, when the protective paper is attached only to the back surface of the anode foil 3a (that is, only the protective paper 42 on the back surface side of the anode foil 3a in FIG. 3 is used for the crimping connection portion of the lead tab 5, the round bar portion 5a, and the lead. It is the result of measuring the corrosion occurrence time in the case where it is attached to the anode foil 3a so as to cover a part of the wire 6 (L1 is 4.0 mm, L2 is 0.5 mm), and it corrodes to the lead tab 5 in 3000 to 3500 hours. There has occurred.

(Example 3)
In the third embodiment, when the protective paper is attached to both the front surface and the back surface of the anode foil 3a (that is, the protective paper 41 on the front surface side in FIG. 3 is an anode so as to cover the flat portion 5b and the round bar portion 5a of the lead tab 5. It is the result of measuring the corrosion occurrence time in the case where the protective paper 42 is attached to the back surface side of the anode foil 3a while being attached to the foil 3a (L1 is 4.0 mm, L2 is 0 mm), and even if it exceeds 9000 hours. No corrosion occurred on the lead tab 5.

(Comparative Example 1)
Comparative Example 1 is a result of measuring the corrosion occurrence time when the protective paper is not used (that is, when neither the front or back protective papers 41 and 42 are attached in FIG. 3), and the corrosion occurrence time is measured on the lead tab 5 in 1500 to 1700 hours. Corrosion has occurred.

(Comparative Example 2)
In Comparative Example 2, when the protective paper is attached only to the surface of the anode foil 3a and only to the connection portion between the lead tab and the anode foil 3a (that is, only the protective paper 41 on the front surface side in FIG. 3 is attached to the flat portion of the lead tab 5). It is the result of measuring the corrosion occurrence time in the case where it is attached to the anode foil 3a only through 5b and the round bar portion 5a is not covered with the protective paper 41), and the lead tab 5 is corroded in 1500 to 1700 hours. ..

As described above, when the protective paper is not used (Comparative Example 1) and when the protective paper is used but does not cover the round bar portion 5a of the lead tab 5 but only the flat portion 5b (Comparative Example 2), corrosion occurs. Whereas the time until the occurrence was 1500 to 1700 hours, at least when the round bar portion 5a was covered with the protective paper (Examples 1 to 3), the time until the corrosion occurred was extended. I was able to.

Further, when the round bar portion 5a is covered with the protective paper, when the protective paper 42 is attached only to the back surface side of the anode foil 3a, when the protective paper 41 is attached only to the front surface side of the anode foil 3a, the anode foil 3a It was found that the effect of suppressing corrosion increases in the order of covering from both the front and back sides with protective paper.

The following can be seen from the above measurement results.
At least, it can be seen that the time until corrosion occurs can be extended by covering the round bar portion 5a of the lead tab 5 on the anode side with a protective paper (Examples 1 to 3).

In the above-described embodiment, as shown in FIG. 3, a case where protective papers 41 and 42 having the same size are attached to both the front and back surfaces of the anode foil 3a has been described, but the present invention is not limited to this. For example, as shown in FIGS. 7 and 8, even if the protective paper 42 on the back surface side is large enough to cover at least the round bar portion 5a of the lead tab 5, the corrosion occurrence time is extended. be able to.

Further, in the above-described embodiment, as shown in FIG. 3, the protective paper 41 having a size sufficient to cover the round bar portion 5a and the flat portion 5b of the lead tab 5 on both the front and back surfaces of the anode foil 3a. Although the case where 42 is used is described, the present invention is not limited to this, and as shown in FIG. 9, for example, as the protective papers 41 and 42, a part of the end face on the sealing body side of the anode foil 3a and the flat portion 5b of the lead tab 5 are used. Even if a paper having a size sufficient to cover a part of the rod and the round bar portion 5a is used, the corrosion occurrence time can be extended.

Further, in the above-described embodiment, the case where at least the round bar portion 5a of the lead tab 5 is attached to the anode foil 3a so as to be covered with the protective papers 41 and 42 has been described, but the present invention is not limited to this, and the anode foil 3a is not limited to this. By covering the portion of the lead tab connected to the above (a part of the flat portion 5b and the round bar portion 5a in the present embodiment) protruding from the electrode foil (anode foil 3a), the time until corrosion occurs is increased. Can be extended.

Further, in the above-described embodiment, the case where the lead tab 5 is covered only on the anode foil side with the protective papers 41 and 42 has been described, but the present invention is not limited to this, and the same applies to the cathode foil side in addition to the anode foil side. The lead tab 15 may be covered with the protective papers 41 and 42.

Further, in the above-described embodiment, an aluminum electrolytic capacitor having a rating of 400 V / 150 μF (external dimensions: aluminum electrolytic capacitor having a diameter of φ18 mm and a length of 40 mm) has been described, but the present invention is not limited to this, and various other types of electrolysis are described. It can be widely applied to capacitors.

1 Electrolytic capacitor 2 Capacitor element 3a Anode foil 3b Cathode foil 4 Separator 5, 15 Lead tab 5a Round bar 5b Flat part 11 Sealing body 12 Exterior case 13 Sleeve 41, 42 Protective paper

Claims (3)

A capacitor element formed by superimposing and winding a valve metal anode foil to which a first lead tab is connected and a cathode foil to which a second lead tab is connected via a separator, and
A protective paper covering at least a portion of the first lead tab protruding from the anode foil,
A bottomed cylindrical exterior case for accommodating the capacitor element,
A sealing body that seals the opening of the outer case and
An electrolytic capacitor characterized by being equipped with. The protective paper is characterized by comprising a first protective paper that covers the front surface side on which the first lead tab of the anode foil is overlapped, and a second protective paper that covers the back surface side of the anode foil. The electrolytic capacitor according to claim 1. The first lead tab is
The flat portion connected to the anode foil and
A round bar portion to be inserted into the insertion hole provided in the sealing body is provided.
The lead wire is welded to the round bar portion, and the lead wire is welded to the round bar portion.
The electrolytic capacitor according to claim 1 or 2, wherein the protective paper covers at least the round bar portion and the lead wire in a range of up to 0.5 times the length of the round bar portion.

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