JP3535014B2 - Electrode for electrolytic capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an electrolytic capacitor in which a lead made of valve metal is attached to a molded body of valve metal powder.

[0002]

2. Description of the Related Art Generally, an electrolytic capacitor element used on the secondary side of a power supply smoothing circuit or around a CPU of a personal computer is required to be capable of handling high frequencies and flowing a large current.

FIG. 6 shows a conventional electrode for an electrolytic capacitor. Electrodes 4 for electrolytic capacitors are formed by implanting lead wires 3 made of a valve metal in a molded body 1 made of a metal powder having a valve action such as tantalum, aluminum, titanium, and niobium.

The molded body 1 of the electrode 4 for the electrolytic capacitor is subjected to chemical conversion to form a dielectric oxide film, and a solid electrolyte layer and a cathode electrode layer are formed on the oxide film.
Then, an external anode terminal is joined to the lead wire 3 which is an anode, an external cathode terminal is joined to the cathode electrode layer, and the electrolytic capacitor element is molded by molding with epoxy-based powder resin so as to cover the entire anode. can get.

In order to pass a large current through such an electrolytic capacitor element, the joint area (hereinafter referred to as "apparent surface area") between the lead wire 3 and the valve metal powder forming the molded body 1 is increased. Therefore, various methods for increasing the apparent surface area have been proposed conventionally.

For example, Japanese Utility Model Application Laid-Open No. 57-138330 proposes a method of thinly flattening the embedded portion of the lead wire 3 in the molded body 1. Also, the actual development 58-
Japanese Patent No. 187136 discloses a method of increasing the apparent surface area by limiting not only the flatness of the lead wire 3 but also the embedding length and flatness thereof. Further, Japanese Utility Model 58 -187,129 No. even publication, likewise leads 3
There is disclosed a method in which the embedded portion of is made flat and its thickness is regulated.

[0007]

However, in the above conventional electrolytic capacitor element, although the lead wire 3 is flattened to increase the apparent surface area, the flattening of the lead wire 3 is limited due to problems such as strength. However, there is a problem in that unevenness due to shrinkage during sintering occurs, and ultra-thin high-density mounting cannot be realized.

As a solution to such a problem, Japanese Patent Laid-Open No. 63-283012 proposes a method in which the lead wire 3 is welded to the side surface of the molded body 1 and then formed into a flat shape. The method has a problem that the manufacturing process is complicated.

Further, although the above-mentioned electrolytic capacitor elements have a large apparent surface area, none of them has a sufficient apparent surface area for passing a large current.

The present invention solves the above-mentioned problems and provides an electrode for an electrolytic capacitor which has a large apparent surface area and can flow a large current and is excellent in high frequency characteristics.

[0011]

The electrode for an electrolytic capacitor of the present invention comprises a valve metal powder compact and a lead made of a valve metal.
An electrode for an electrolytic capacitor with a foil attached as
The width of the lead foil is substantially constant,
Embedded part and not embedded in the molded body
Part of the molded body so that the foil width is almost the same as the part
Embedded, and the thickness of the lead foil is 100 μm or less.
It is the lower electrode for the electrolytic capacitor.

According to the present invention, it is possible to obtain an electrode for an electrolytic capacitor which has a large apparent surface area to allow a large current to flow and which has excellent high frequency characteristics.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The electrode for an electrolytic capacitor according to claim 1 of the present invention is an electrode for an electrolytic capacitor in which a foil made of valve metal is attached to a molded body of valve metal powder as a lead, and the lead foil is , The width of which is substantially constant, a part of which is embedded in the molded body, and a part of which is not embedded in the molded body, the foil width being substantially the same, and The thickness of the lead foil is 100
It is characterized by being less than or equal to μm.

According to this structure, the bonding area between the powder of the valve metal forming the molded body and the lead is increased, so that the resistance at the bonding point is reduced, the equivalent series resistance is reduced, and the high frequency characteristics are excellent and large. Ripple current can flow. Further, since the bonding area is increased, the adhesive strength between the lead and the molded body can be improved.

The electrode for an electrolytic capacitor according to claim 2 is
In Claim 1, unevenness is formed on the surface of the valve metal foil,
The unevenness is formed so that the surface area of the contact portion of the foil with the molded body is not less than twice the surface area of the contact area of the foil with the molded body.

With this configuration, the above effect can be further enhanced. An electrode for an electrolytic capacitor according to claim 3 is the electrode metal foil according to claim 1 or 2,
It is characterized by having a through hole.

According to this structure, the foil is more likely to receive the force of shrinking the compact when the compact is sintered, so that the bonding area between the valve metal powder and the foil is further increased, resulting in a low equivalent series resistance. Moreover, the adhesive strength between the lead and the molded body can be increased.

Each embodiment of the present invention will be described below with reference to FIGS. It should be noted that components similar to those in FIG. 1 showing the above-mentioned conventional example will be described with the same reference numerals.

(Embodiment 1) FIGS. 1 to 3 show an electrode for an electrolytic capacitor according to (Embodiment 1) of the present invention. Figure 1
The electrode for an electrolytic capacitor shown in FIG.
However, this (Embodiment 1) is different in that the lead wire 3 which is conventionally linear has a foil shape to increase the apparent surface area.

Specifically, tantalum powder is used as the valve metal, this tantalum powder is molded and vacuum-sintered with the foil 2 also made of tantalum to form the electrode 4 for electrolytic capacitor.

Then, on the electrolytic capacitor electrode 4,
After forming an oxide film and an electrolyte layer in the same manner as in the above-mentioned conventional example, a cathode extraction electrode is provided. After that, an external anode terminal is joined to the foil 2, which is an anode, an external cathode terminal is joined to the cathode electrode layer, and the anode 2 is molded with an epoxy-based powder resin or the like so as to cover the entire anode to form an electrolytic capacitor element.

As described above, by making the shape of the anode lead not the linear shape but the foil 2, the contact area, that is, the apparent surface area, of the tantalum fine powder as the anode and the lead is increased, and the obtained electrolytic capacitor element is The equivalent series resistance is reduced and the high frequency characteristics are excellent.

Further, since the apparent surface area can be increased by using the foil 2 and the buried volume which is a loss in capacitance can be reduced, the capacitance can be increased.

In order to increase the apparent surface area,
Not only adjusting the thickness and width of the foil 2 and the embedding length,
The surface of the foil 2 may be increased by polishing or electroetching.

Further, since the thinner molded body 1 can be prepared by using the foil 2, the electrolytic capacitor electrode 4 is inevitably thin, and a small and large-capacity electrolytic capacitor element can be obtained.

A specific example of this (Embodiment 1) will be shown below. The following Examples 1 to 5 and Comparative Example 1 were performed in order to investigate the relationship between the apparent surface area and the equivalent series resistance and the ripple heat generation temperature.

Example 1 40000 μF · V as valve metal
/ G of tantalum powder was used, and this tantalum powder was added to 1.7.
Formed into a size of mm × 3.5 mm × 6.4 mm,
A molded body 1 was obtained.

As the foil 2, a foil 2 also made of tantalum and having a thickness of 200 μm and a width of 0.3 mm is used, and the depth of the embedded portion in the molded body 1 is 4 mm.
Along with that, vacuum sintering was performed at 1450 ° C. to obtain an electrode 4 for an electrolytic capacitor.

Then, in order to evaluate it as an electrolytic capacitor element, the molded body 1 of the electrode 4 for electrolytic capacitor is provided with 8
Chemical formation was carried out in a phosphoric acid solution at 5 ° C. at an applied voltage of 30 V to form an oxide film. Further, after forming manganese dioxide as an electrolyte, a cathode extraction electrode composed of a carbon layer and a silver conductive resin layer was provided.

After that, an external anode terminal is joined to the foil 2,
An external cathode terminal was joined to the cathode extraction electrode and molded with a resin to produce an electrolytic capacitor element. Using this electrolytic capacitor element, the equivalent series resistance of 100 kHz and the ripple heat generation temperature were measured.

The ripple heat generation temperature was measured as follows. That is, a 100 kHz sine wave with a bias superimposed is applied as a ripple to the external anode and external cathode terminals of the electrolytic capacitor element. Ripple current is 10
The output of the amplifier was adjusted so that 00mAP-P could flow through the electrolytic capacitor element, and the ripple heat temperature was measured.

Table 1 shows the equivalent series resistance and the ripple heat generation temperature of the obtained electrolytic capacitor element.

[0033]

[Table 1]

Examples 2 to 5 In order to investigate the influence of the apparent surface area on the electrolytic capacitor element, the thickness and width of the foil 2 are shown while the embedding depth of the foil 2 in the molded body 1 is fixed at 4 mm. The volume of the lead portion embedded in the molded body 1 was changed as shown in FIG.

Other than that, an electrolytic capacitor element was prepared in the same manner as in Example 1, and the equivalent series resistance and the ripple heat generation temperature of the electrolytic capacitor element were measured. The obtained measurement results are shown in Table 1.

Comparative Example 1 Unlike the above Examples 1 to 5, a lead wire 3 having a circular cross section and a diameter of 280 μm was used as a lead.

The depth of the embedded portion of the lead wire 3 is 4
mm, the capacitance of the obtained electrode is
It was made to be almost equal to 5.

Comparing Example 1 with Comparative Example 1 , the apparent surface area of the anode lead is almost the same, so that the equivalent series resistance and the ripple heat generation temperature are about the same.
However, as shown in Examples 2 to 5, the thickness of the foil 2 is 20
Since the contact area between the tantalum fine powder, which is the anode, and the lead increases as the width of the foil 2 becomes wider and the apparent surface area becomes larger by making the thickness smaller than 0 μm, the obtained electrolytic capacitor element is equivalent. The series resistance is reduced and the high frequency characteristics are excellent.

Further, since the temperature rise of the ripple heat generation can be reduced, an excellent electrolytic capacitor element having an increased allowable ripple current amount in the same temperature rise range can be obtained.

Although the foil 2 as the anode lead is embedded inside the molded body 1 as shown in FIG. 1 in the above (first embodiment), the present invention is not limited to this, and the lead wire is not limited thereto. If the apparent surface area is larger than when using No. 3, the foil 2 is attached to the surface of the molded body 1 as shown in FIG. 2, or the foil 2 is embedded in the molded body 1 as shown in FIG. It may be exposed.

When the surface of the foil 2 is polished or electronically etched to form irregularities to increase the apparent surface area, as is clear from Examples 1 to 5, before the irregularities are formed. If the unevenness is formed so as to be more than twice the apparent surface area of the foil 2, it will be more effective to realize a reduction in the equivalent series resistance value and a reduction in the ripple heat generation temperature.

Further, as is clear from Examples 1 to 5 and Comparative Example 1, the greater effect was obtained when the thickness of the foil 2 was 100 μm or less.

(Embodiment 2) In Examples 1 to 5 and Comparative Example 1 in the above (Embodiment 1), the influence of the apparent surface area on the equivalent series resistance and the ripple heat generation temperature was investigated. Form 1) of the following embodiment 6 to.
8 and Comparative Example 2, the effect of the apparent surface area on the high frequency characteristics was examined.

Examples 6 to 8 Foil 2 having a thickness of 50 μm is used, and its width and the depth of burying in the molded body 1 are shown in Table 2 so that the volume of the buried portion is the same.
It was changed as shown in. Then, an electrolytic capacitor element was produced in the same manner as in Example 1 except the above.

[0045]

[Table 2]

FIG. 4 shows changes in the impedance of the obtained electrolytic capacitor element at 100 Hz to 40 MHz.

Comparative Example 2 Using the same lead wire 3 as in Comparative Example 1, the above-mentioned Examples 6 to 6 were used.
The lead wire 3 was embedded in the molded body 1 so that a capacity substantially equal to that of 8 was obtained. An electrolytic capacitor element was produced in the same manner as in Example 1 except for the above.

FIG. 4 shows changes in impedance of the obtained electrolytic capacitor element in the range of 100 Hz to 40 MHz.

As shown in FIG. 4, 100 Hz to 300,
There is no difference in impedance between Examples 6 to 8 and Comparative Example 2 between 000 Hz, but in the high frequency region above 300,000 Hz, Examples 6 to 8 have smaller impedance than Comparative Example 2 and are favorable. High frequency characteristics were obtained.

This is because the anode leads of Examples 6 to 8 are not the lead wire 3 having a circular cross section but the foil 2 having a quadrangular cross section, so that the cross sectional area becomes large and the equivalent series resistance becomes low at the resonance frequency. It is considered that this is because the width of the foil 2 becomes wider, which results in a low equivalent series induction.

(Embodiment 3) FIG. 5 shows (Embodiment 3) of the present invention. FIG. 1 in the above (Embodiment 1)
The electrolytic capacitor electrode 4 has substantially the same structure as that of the electrolytic capacitor electrode 4 shown in FIG. 3, except that a plurality of through holes 5 are provided in the embedded portion of the foil 2 in the molded body 1.

By providing the through holes 5 in the foil 2 in this way, even if the apparent surface areas are almost the same, the force with which the compact 1 shrinks when the compact 1 and the foil 2 are vacuum-sintered. The foil 2 becomes easy to receive (in the directions of arrows A and B), the bonding area becomes large, and an electrolytic capacitor element having a low equivalent series resistance and high strength can be obtained.

A specific example of this (Embodiment 3) will be shown below.

Example 9 Twenty through holes having a diameter of 0.2 mm were provided in the foil 2 having a thickness of 50 μm, a width of 1.2 mm and an embedding depth of 4 mm. An electrolytic capacitor element was produced in the same manner as in Example 1 except for the above.

100 kH of the obtained electrolytic capacitor element
Table 3 shows the equivalent series resistance at z and the strength ratio when Comparative Example 3 and Example 9 were compared.

[0056]

[Table 3]

Comparative Example 3 A foil 2 having a thickness of 50 μm, a width of 1.2 mm and an embedding depth of 4 mm and having no through hole 5 was used. And otherwise, Example 1
An electrolytic capacitor element was produced in the same manner as in.

100 kH of the obtained electrolytic capacitor element
Table 3 shows the equivalent series resistance and intensity ratio at z.

Although the apparent surface areas of Example 9 and Comparative Example 3 are almost the same, Example 9 is different from Compact 1 in vacuum sintering.
Since the foil 2 is easily subjected to the force of contraction and the bonding area between the powder and the foil 2 is increased, a low equivalent series resistance and a high strength are obtained.

Although a plurality of through holes 5 are provided in the foil 2 in the above (Embodiment 3), the present invention is not limited to this, and as described in the above (Embodiment 1). In addition, unevenness may be formed on the surface of the foil 2 by etching or the like, and a plurality of through holes 5 may be formed in the foil 2 having this unevenness.

Although tantalum is used as the valve metal in the above (first embodiment) to (third embodiment), the present invention is not limited to this, and valve metals other than tantalum may be used. Also has the same effect.

[0062]

As described above, according to the electrode for an electrolytic capacitor of the present invention, the lead foil has a substantially constant width,
By embedding a part in the molded body and setting the thickness of the lead foil to 100 μm or less, so that the foil width of the portion embedded in the molded body and the portion not embedded in the molded body are substantially the same. Since the bonding area between the powder of the valve metal and the lead forming the molded body is increased, the resistance at the bonding point is reduced, the equivalent series resistance is reduced, the high frequency characteristics are excellent, and an electrolysis that allows a large ripple current to flow. A capacitor electrode is obtained.

Further, since the bonding area between the lead and the molded body is increased, the adhesive strength between the lead and the molded body can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an electrode for an electrolytic capacitor according to (Embodiment 1).

FIG. 2 is a perspective view showing the configuration of another electrolytic capacitor electrode according to the first embodiment.

FIG. 3 is a perspective view showing the configuration of another electrolytic capacitor electrode according to the first embodiment.

FIG. 4 is a graph showing frequency characteristics of impedance in (Embodiment 2)

FIG. 5 is a cross-sectional view showing the configuration of an electrolytic capacitor electrode according to (Embodiment 3).

FIG. 6 is a perspective view showing a configuration of a conventional electrode for electrolytic capacitor.

[Explanation of symbols]

1 molded body 2 foil 3 lead wire 4 Electrode for electrolytic capacitor 5 through holes

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masakazu Tanahashi               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Takeshi Nishi               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Kiyoshi Hirota               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Iku Watanabe               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Hiroshi Kita               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Yoshihiro Higuchi               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd. (72) Inventor Yoji Masuda               1006 Kadoma, Kadoma-shi, Osaka Matsushitaden               Instrument industry Co., Ltd.                (56) Reference JP-A-6-97009 (JP, A)                 JP-A-5-275290 (JP, A)                 Actual development Sho 63-188936 (JP, U)

Claims (3)

(57) [Claims] 1. An electrode for an electrolytic capacitor, comprising a valve metal powder molded body and a foil attached as a lead made of valve metal, wherein the lead foil has a substantially constant width and is embedded in the molded body. And a part not embedded in the molded body, the foil width is substantially the same as the foil width, and the lead foil has a thickness of 100 μm or less. 2. A surface of a valve metal foil having irregularities formed thereon, and a surface area of a contact portion of the foil with the molded body is at least twice as large as a surface area of a contact portion of the foil without the irregularity contacting the molded body. The electrode for an electrolytic capacitor according to claim 1, wherein the unevenness is formed as described above. 3. The valve metal foil has a through hole.
Alternatively, the electrode for an electrolytic capacitor according to claim 2.