JP2001126960A - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To provide a structure of a solid electrolytic capacitor and a method of manufacturing the same, and to provide a capacitor with less leakage current defect. SOLUTION: The anode lead is subjected to a surface roughening treatment to suppress the occurrence of slip at the interface between the valve metal and the oxide film. Further, a reinforcing resin is formed at a joint between the anode lead subjected to the surface roughening treatment and the internal element of the solid electrolytic capacitor. as a result,
It is possible to prevent a large defect from being generated in the oxide film and to reduce a leakage current defect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a solid electrolytic capacitor and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional method for manufacturing a solid electrolytic capacitor will be described.

First, a dielectric made of an oxide film is formed on the surface of a porous anode body made of a valve metal. A solid electrolyte is formed on the oxide film. Thereafter, a cathode layer composed of a carbon layer and a silver layer is formed to form an internal element of the solid electrolytic capacitor. On the anode side, the lead of the anode body and the anode lead-out terminal are joined, and on the cathode side, the internal element of the solid electrolytic capacitor and the cathode lead-out terminal are connected with a silver adhesive, and the whole is molded with an exterior resin to form a solid electrolytic capacitor. Was composed.

[0004] The solid electrolytic capacitor having such a configuration has an anode lead for joining an anode body having an increased area to take out more capacitance and an anode terminal electrode to be drawn out.

In a solid electrolytic capacitor having an anode lead as described above, when a solid electrolyte, a carbon layer, a silver layer, or the like comes in contact with the anode lead, the leakage current increases. An oxide film is also formed on the lead.

[0006]

However, in a conventional solid electrolytic capacitor having an anode lead, a mechanical stress when joining the anode lead and the anode terminal electrode is reduced.
After joining the terminal electrode and the internal element, the oxide film at the base of the anode lead where the anode lead and the anode body were joined was likely to have defects due to mechanical and thermal stress when molding the whole with the exterior resin. .

In the case of a solid electrolytic capacitor, even if a defect occurs in an oxide film, a short circuit does not occur unless a conductive substance adheres to a defective portion of the oxide film, and the leakage current does not increase.

Therefore, in a conventional solid electrolytic capacitor having an anode lead, a water-repellent resin or the like is formed at a junction between the anode lead and the internal element in order to suppress a leakage current defect caused by the anode lead. In addition, an attempt was made to prevent the solid electrolyte from adhering to the anode lead. However, in the process of forming the solid electrolyte, the water-repellent resin gradually loses its water-repellency, and the attachment of the solid electrolyte cannot be completely prevented.

After the solid electrolyte is formed on the internal element, an epoxy resin or the like is formed on the base of the anode lead, the base of the anode lead is reinforced so as not to receive stress, and the generation of defects in the oxide film is suppressed. Attempts have been made to do so. However, even in this case, the leakage current defect could not be completely prevented.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to suppress an increase in leakage current by subjecting an anode lead to a surface roughening treatment. The present invention provides a configuration of a solid electrolytic capacitor and a method of manufacturing the same.

When an oxide film is formed on an anode lead that has not been subjected to a surface roughening treatment, when stress is applied to the anode lead, a slip occurs at the interface between the valve metal 21 and the oxide film 22 as shown in FIG. A large oxide film defect 23 is generated in the film 22. However, when an oxide film is formed on the roughened anode lead, even if stress is applied to the anode lead, the anode lead is roughened.
As shown in FIG. 1, it is possible to prevent a slip from occurring at the interface between the valve metal 11 and the oxide film 12. Therefore, a large oxide film defect portion 13 does not occur in the oxide film 12 of the anode lead.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 3 and 4 show an example of a tantalum solid electrolytic capacitor having a lead roughened surface according to the present invention, and are schematic sectional views of the tantalum solid electrolytic capacitor.

The outline of the manufacturing method will be described below with reference to the drawings.

First, tantalum powder is supplied to the anode leads 31 and 41.
After forming into a predetermined shape (1.0 mm x 3.2 mm x 4.4 mm) together with a tantalum metal wire (diameter 0.3 mm), the powder is bonded by high-temperature sintering in a vacuum, and tantalum metal with submicron pores Is formed and anodized in an electrolyte to form a dielectric oxide film on the surface of the tantalum metal. Next, after forming a solid electrolyte on the inside and outside surface of the pores of the sintered body with polypyrrole which is a conductive polymer,
A carbon layer serving as a cathode layer and a silver layer are formed in this order, and the solid electrolytic capacitor internal elements 32 and 42 are formed.

Thereafter, on the anode side, the anode lead and the anode lead-out terminals 33 and 43 are joined by welding, and on the cathode side, the solid electrolytic capacitor internal elements 32 and 42 and the cathode lead-out terminals 34 and 44 are joined.
After connecting with silver adhesive 35, 45, the whole is exterior resin 36, 46
Mold with. Thereafter, aging was performed to produce a solid electrolytic capacitor.

[0017]

(Example 1) A tantalum anode lead was made of NaO
After applying a direct current of 1 A in an H aqueous solution for 10 seconds and performing direct current etching of the anode lead, a surface roughened by chemical etching in an HF aqueous solution was used as the anode lead. The surface-treated anode lead was molded together with tantalum powder, and then a solid electrolytic capacitor was produced as described above.

(Embodiment 2) A solid electrolytic capacitor internal element 42 similar to that of Embodiment 1 was manufactured using an anode lead roughened under the same conditions as in Embodiment 1, and then an anode lead 41 and an internal element 42 were manufactured. A reinforcing resin 47 was formed at the base of the anode lead at the joint of (1).

After using epoxy resin as a reinforcing resin and applying resin to the joint between the anode lead 41 and the internal element 42,
It was heated at 150 ° C. for 30 minutes to cure. Thereafter, a solid electrolytic capacitor was manufactured as described above.

(Conventional Example 1) For comparison with the conventional example, a solid electrolytic capacitor was manufactured as described above using an anode lead not subjected to surface roughening treatment.

The leakage currents of the solid electrolytic capacitors obtained in Examples 1 and 2 and Conventional Example 1 were measured. The leakage current was measured by measuring a current value when a rated DC voltage was applied for 3 minutes, and counting the number of measured values exceeding a specified value (20 μA). The number of samples was 100 for each condition. The results are shown in (Table 1).

[0022]

[Table 1]

FIG. 5 shows an SEM photograph of the anode lead subjected to the surface roughening treatment in Examples 1 and 2, and FIG. 6 shows an SEM photograph of the anode lead not subjected to the surface treatment treatment in Conventional Example 1. Show.

As is clear from Table 1, Example 1,
It can be seen that the solid electrolytic capacitor of No. 2 has less leakage current failure than Conventional Example 1. This is because the surface roughening treatment of the anode lead reduces defects in the oxide film of the lead. In addition, when the first embodiment is compared with the second embodiment, the second embodiment has a further reduced leakage current defect. This is considered to be because in Example 2, the base of the anode lead subjected to the surface roughening treatment was reinforced with epoxy resin.

A comparison between FIG. 5 and FIG. 6 shows that fine irregularities are formed by etching on the anode lead subjected to the surface roughening treatment. For tantalum,
Since it is more corrosive than aluminum, it is difficult to form fine irregularities only by electrolytic etching or chemical etching. However, it has been found that by performing electrolytic etching to form very small irregularities on the surface and then dissolving the irregularities by chemical etching, it is possible to easily form appropriate irregularities that can prevent leakage current defects.

In this embodiment, after the anode lead is subjected to a surface roughening treatment, it is molded together with a tantalum powder and then sintered to form an anode body having an anode lead. May be before the step of forming a dielectric oxide film, an anode lead not subjected to surface roughening treatment is molded together with tantalum powder and then sintered to form an anode body having an anode lead. The same effect can be obtained by selectively performing the surface roughening treatment or by performing the surface roughening treatment on the entire anode lead and anode body.

In this embodiment, the reinforcing resin is formed at the junction between the anode lead of the internal element of the solid electrolytic capacitor formed up to the cathode layer and the internal element. It suffices if it is before the step of connecting to the electrode, after forming an oxide film on the anode body having the anode lead, forming a reinforcing resin at the junction between the anode lead and the internal element, and then forming a solid electrolyte Has the same effect.

In this embodiment, an epoxy resin is used as the reinforcing resin. However, the present invention is not limited to this.
Similar effects can be obtained by using a silicone resin or another resin as the reinforcing resin.

In this embodiment, tantalum is used as the valve metal of the anode body. However, the present invention is not limited to this, and the same effect can be obtained by using etched aluminum or the like as the anode body.

In this embodiment, polypyrrole, which is a conductive polymer, is used as the solid electrolyte. However, the present invention is not limited to this, and another conductive polymer, manganese dioxide, or the like may be used.

[0031]

As described above, according to the present invention, leakage current defects are reduced by subjecting the anode lead to a surface roughening treatment. Furthermore, by forming a reinforcing resin at the joint between the anode lead having been subjected to the surface roughening treatment and the internal element of the solid electrolytic capacitor, it is possible to provide a solid electrolytic capacitor capable of further reducing defective leakage current and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic view of a surface layer portion of an anode lead according to the present invention.

FIG. 2 is an enlarged schematic view of a surface layer portion of a conventional anode lead.

FIG. 3 is a schematic view of a solid electrolytic capacitor according to a configuration of the present invention and a conventional example.

FIG. 4 is a schematic view of a solid electrolytic capacitor according to the configuration of the present invention.

FIG. 5 is a view showing a SEM photograph of an anode lead of the present invention.

FIG. 6 is a view showing a SEM photograph of a conventional anode lead.

[Explanation of symbols]

 11, 21 Valve metal 12, 22 Oxide film 13, 23 Oxide film defect 31, 41 Anode lead 32, 42 Internal element of solid electrolytic capacitor 33, 43 Anode lead terminal 34, 44 Cathode lead terminal 35, 45 Silver adhesive 36, 46 exterior resin 47 reinforcement resin

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasunobu Tsuji 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Masakazu Tanahashi 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A solid electrolytic capacitor having an anode lead and a dielectric oxide film, a solid electrolyte, and a cathode layer formed on the surface of an anode body made of a valve metal, wherein the anode lead is roughened. A solid electrolytic capacitor characterized by being treated. 2. A solid electrolytic capacitor having an anode lead and a dielectric oxide film, a solid electrolyte, and a cathode layer formed on the surface of an anode body made of a valve metal, wherein the anode lead has a roughened surface. A solid electrolytic capacitor which has been treated and has a reinforcing resin formed at a joint between the anode lead having been subjected to the surface roughening treatment and the anode body. 3. The solid electrolytic capacitor according to claim 1, wherein the solid electrolyte is a conductive polymer. 4. A method for manufacturing a solid electrolytic capacitor having an anode lead and having a dielectric oxide film, a solid electrolyte, and a cathode layer formed on the surface of an anode body made of a valve metal, the method comprising: After performing the surface-roughening treatment, an anode body is integrally formed with the surface-treated anode lead, or the solidified anode body and the previously formed anode body are joined together. Manufacturing method of electrolytic capacitor. 5. A method for manufacturing a solid electrolytic capacitor having an anode lead and having a dielectric oxide film, a solid electrolyte, and a cathode layer formed on the surface of an anode body made of a valve metal, the method comprising: After performing the surface roughening treatment, the anode body is integrally formed together with the surface-treated anode lead, or the anode lead that has been subjected to the surface roughening and the previously formed anode body are joined, and then the roughened surface is A method for manufacturing a solid electrolytic capacitor, characterized in that a reinforcing resin is formed at the joint between the anode lead and the anode body that have been subjected to the chemical treatment. 6. The method for manufacturing a solid electrolytic capacitor according to claim 4, wherein said surface roughening treatment is electrolytic etching. 7. The method for manufacturing a solid electrolytic capacitor according to claim 4, wherein said surface roughening treatment is chemical etching. 8. The method for manufacturing a solid electrolytic capacitor according to claim 4, wherein the surface roughening is blasting. 9. The method for manufacturing a solid electrolytic capacitor according to claim 4, wherein chemical etching is performed after the surface roughening treatment is performed by electrolytic etching.