JPS602768B2 - solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid electrolytic capacitor whose anode body is made of a valve metal such as tantalum (Ta) or aluminum (AZ), and in particular improves this solid electrolyte to reduce dielectric loss (tan
6) A solid electrolytic capacitor with low leakage current (LC) is obtained.

Generally, in solid electrolytic capacitors that use Ta as the base of the anode body, the anode body is formed by forming a tantalum oxide (Ta2Q) film, which is a dielectric oxide film, on the surface of the Ta base body. Also, a solid electrolyte layer is formed on the Q film, and a cathode layer and a cathode conductor layer are sequentially laminated on this solid electrolyte layer.

The Ta205 film is produced by anodization, has a rectifying effect, has a very thin film thickness of 50 to 2000 A, and has a high yield ratio of 20 to 30, and constitutes the capacitance portion of the capacitor. However, the Ta205 film produced in this way also has many defect points within the film, and when used as a capacitor, the leakage current increases due to the defect points, and excessive A problem arises in which the current flows in a concentrated manner. At this time, as shown in FIG. 1, T on the Ta substrate 1 is thermally or electrochemically applied to the defective point of the 05 film 2 from the solid electrolyte layer 3 using the solid electrolyte layer formed on the 05 film. - Ions are supplied to repair the defects in T05 film 2, and Ta20
5 The leakage current in the film 2 becomes low. This kind of action is generally called "self-repairing action." That is, T is 05
The solid electrolyte layer formed on the film supplies oxygen to the Ta205 film, lowering the leakage current of the capacitor and increasing its breakdown voltage.

Therefore, as a solid electrolyte for a solid electrolytic capacitor, firstly, it must be a metal oxide with a large ability to supply oxygen to Ta205, that is, a metal oxide with strong oxidizing power, and secondly, it must be used to reduce tan6, which is the resistance component of the capacitor. requires low electrical resistance.

Currently, manganese dioxide (Mn02) and lead dioxide (Pb02) are commonly used as solid electrolytes because they satisfy the above-mentioned conditions and are inexpensive.

The present invention uses ruthenium oxide (Rpi02) and iridium oxide (1 of 2), which exhibit more favorable performance than Mn02 and Pb02, which are currently widely used as solid electrolytes.
, rhenium oxide (Re02), rhodium oxide (Rh02)
), osmium oxide (0s02) is used, and low tan6
, to obtain a low LC solid electrolytic capacitor.

Hereinafter, the superiority of Ru02 over Mn02 and its suitability as an electrolyte for capacitors will be explained in detail using Ru02 as a representative example.

First, to explain the electrical resistance of both, the electrical resistance of MnQ varies depending on the manufacturing method such as thermal decomposition of Mn(N03)2, electrolysis of Mn salt solution, vapor deposition, sputtering, etc., but it is approximately = 10- 1 to 1 pi○, and belong to the semiconductor domain, and in practice, Mn02 behaves as an n-type semiconductor, and Mn203 behaves as a p-type semiconductor.

On the other hand, the following metal oxides have lower electrical resistance than Mn02, as shown below, although there are various differences depending on the manufacturing method. RJ02 10
-5~10-2Q, Guy Ir.

2 5×10-5Q.

佽Re.

2 1XI.

-4Q.佽Rh.

2 <10-4Q・C O.S.

2 6×10-5Q, suppression Here, tan8 of the capacitor will be explained.

The equivalent circuit of an electrolytic capacitor is generally expressed as shown in Figure 2, and the resistance components include resistance R caused by Ta205, and resistance R2 caused by the solid electrolyte and other lead wires. tan6 can be expressed as shown in the following equation.

tan6 ni CR's C (RI 10 R2) ni's CRI 10's C
R2 CR in this formula is the resistance of Ta205, so
Regarding the anodization conditions and other conditions, the enemy CR2 is caused by the physical properties of the solid electrolyte and is greatly influenced by its thickness, thermal decomposition adhesion state, and electrical resistance. That is, if a substance with low electrical resistance is used as the solid electrolyte, the CR2 of the capacitor will also be reduced, and the capacitor's current n6 will also be reduced. Therefore, R
When the aforementioned metal oxides such as Mt. 02 are used as the solid electrolyte, they have a lower electrical resistance than MnQ, and are therefore very effective in obtaining a capacitor with a low n6 value.

Next, various characteristics of R2 as a representative example of the metal oxide mentioned above will be described.

First, the chemical formation performance of R2 will be explained. The following experiment was conducted to confirm that R-2 has chemical formation performance.

As shown in Fig. 3, a film of about 50 mm thick is formed by thermal decomposition of ruthenium chloride (R) on a capacitor-grade Ta substrate 4.
In addition to forming the Ru02 film 5 with zero peaks, this R
A sample 7 with an electrode 6 formed by vapor deposition of gold (Au) on the J02 film 5 is connected to a DC power source 8 and an ammeter 9 as shown in FIG.
The Ta substrate 4 was inserted and connected as an anode and the electrode 6 as a cathode into the open circuit of the sample 7, and a constant voltage was applied to the sample 7 to examine the chemical formation current.

In addition, in FIG. 4, one river is a decoder that records the numerical value of the ammeter 9. The result of this experiment is shown in the chemical current curve diagram in Figure 5. By applying a constant DC voltage of 10 V, a rapid rise in current can be seen immediately after application, but after a few seconds, the current begins to fall, and the voltage If you continue to apply , it will gradually approach a constant value.

Even when the applied voltage is increased to 20V and 30V, the same current curve as when the applied voltage is 10V is shown. This phenomenon occurs because the Ta205 dielectric film force is generated between the Ta205 dielectric film 4 and the RuQ film 5 due to the application of a constant DC voltage, and the current value approaches a constant value as time passes. corresponds to the leakage current of the Ta2Q film.

That is, by applying a voltage, 02-ions are supplied from the Ru02 film 5 to the Ta substrate 4, and ``02-ions are also formed on the Ta substrate 4''.
5 anodic oxide film is formed, and it can be interpreted that the RA phase anodic oxidation is occurring due to the R mountain 02. As described above, the above experiment shows that Ru02 has the ability to supply oxygen and has the ability to self-repair as a solid electrolyte in a capacitor. As mentioned above, R's 2
has an oxygen supply ability and has a lower electrical resistance than Mh02, so when used as a solid electrolyte in a solid electrolytic capacitor, it can be made into a solid electrolytic capacitor with low tan6 and low LC. In addition, oxides other than MN02, namely lrQ, Ryama02, Rh02, and 0s02, are also metal oxides with lower air resistance than MnQ, like Ru02, and also have oxygen supply ability, and are also free from self-induced reactions to capacitors. Because it has low tan6, similar to R2,
A solid electrolytic capacitor with low LC can be obtained.

Next, the usage and production method when Ru02 is actually used as a solid electrolyte of a capacitor will be explained. Generally, Ru02 is obtained by thermal decomposition of Riso3, and this thermal decomposition method is most suitable for producing Ru02 used in solid electrolytes of capacitors.

Methods for using Ru02 as a solid electrolyte include mixing Ru02 in mMn02 in a random manner;
'2) Method of using only 2 of R, '3} 2 of R and Mn
Method of stacking and using 02, '4) R2 and Mn0
A method in which MnQ and MnQ in which Ru02 is mixed in a random manner are used in a layered manner; ■ A method in which MnQ and MnQ in which R2 is mixed in a random manner are laminated. There is.

Method m is a method in which a Ta substrate with a Ta205 film formed on the surface is immersed in a mixed solution of Mm(N03)2 and RuCZ3 produced by adding RuC etc. to Mm(N03)2 and thermally decomposed. A structure as shown in FIG. 6 is obtained.

In addition, in FIG. 6, 11 is a Ta substrate, 12 is a Ta20
5 film, 13 is Mn02 layer mixed with Ru0214. In addition, the method '2} is a method in which a Ta substrate with a Ta205 film formed on the surface is immersed in RuC solution and thermally decomposed, and a solid electrolyte layer of only Ru02 is obtained on the Ta2Q film.

'3} method involves thermal decomposition of RuC3 and Mn(N03)
By carrying out the thermal decomposition of 2 and 2 appropriately alternately, a laminated structure of Ru02 and Mh02 is obtained as shown in FIG.

In addition, in FIG. 7, 15 is a Ta substrate, 16 is a Ta2
4 films, 17 is two layers of R, and 18 is Mn02 layer. Furthermore, the method of '41, ■, RuC〆3 or Mn(
Mh(N03)2, RuCso3 produced by thermal decomposition of NQ)2 and adding RuCso3 to Mn(N03)2
The thermal decomposition of the mixed solution is carried out alternately, and R
A laminated structure of Mn02 or Mh02 mixed with Ru02 is obtained.

Here, the thermal decomposition reaction of R and E3 will be explained.

When RuC〆3 is thermally decomposed, RJ02 is obtained as shown in the following formula.
and C so2.

Wave JC So3 1202 Primary V02 Juchi So2 ↑The thermal decomposition temperature of this R is 32 as measured by a thermobalance.
The temperature is 0°C or higher.

However, at a temperature of about 250q○ to 300qo
Even a mixed oxide containing 10 and 10 R, which is a thermal decomposition intermediate product of R and 3, has the above-mentioned solid formation ability. Furthermore, when thermal decomposition is performed by adding RuC〆3 to Mn(N03)2, the generated MN02
Due to the catalytic action of (the thermal decomposition temperature of Mn(NQ)2 130°C), the thermal decomposition temperature of R is lowered, and as measured by a thermobalance, RuQ is produced at 250 to 300°C. Note that, at this time, not only Ru02 is necessarily generated, but an intermediate product of R-3 is also generated in MnQ. In this way, no matter which method of {11 to [51] is used, Ta205 can be heated at temperatures from 200°C to less affected by thermal deterioration.
R2 or its intermediate products can be obtained at a thermal decomposition temperature of 300° C., and both R2 and its intermediate products are suitable as solid electrolytes.

In addition, when using a porous anode body such as a twill body, M
One cycle of immersion pyrolysis of b(N03)2 is insufficient and it is necessary to return the circuit two to one times, but R
The addition of Mn(N03)2 to Mn(N03)2 does not necessarily have to be applied to all pyrolysis processes.

That is, as shown in the above-mentioned method [3' to
It is sufficient to use n(N03)2. Also, Ru0
Method 2, in which only 2 is used as a solid electrolyte, is not economical because 3 is expensive, and 2 is not economical.
It is more economical to use methods 3' to {5). R mountain 0
Regarding the effect when using 2, there is not much difference in any of the methods '1' to t5}, but the above-mentioned (
Methods 3' to 5) are slightly superior in terms of economy and properties.

Here, RMC Yu3 is added to Mn(N03)2.
This is noticeable when RuC3 is added to 2.

This is thought to be due to the good permeability of R into the lepidomeniform pores of Part 3. Also, Mn(N03)
2 instead of Mh(OH)2-Mn(N03)2-
A slurry mixed solution based on NH4N03-day20 may be used, and in this case, the number of times of thermal decomposition can be reduced and the thermal decomposition operation can be made extremely easy.

Moreover, in this case, a uniform solid electrolyte layer with fine particle size can be formed, as is clear from the scanning electron micrograph of FIG.

In addition, Fig. 8 shows Mn(OH)2 - Mn(N03)2
This is a 3000x scanning electron micrograph of a solid electrolyte formed by pyrolyzing a slurry-like pyrolyzable solution made by adding R core 3 to NH4N03-day20. In addition, in the above explanation, we described the case where R-mount 02 or its intermediate products are obtained by thermal decomposition of RuCZ3, but it can also be obtained by thermal decomposition of Ru nitrates, sulfates, and carbonates, and lr , Re, Rh, and melon can also obtain similar results*.

Next, we will discuss the results of specific experiments conducted to support the above.

(Example 1) A 18V, T05 film was formed using phosphoric acid on the surface of a cylindrical Ta compact having a diameter of 2.3 ribs and a height of 3 ribs to constitute an anode body.

This anode body was immersed in a mixed solution of Mn(N03)2 with a specific gravity of 1.6 and RuCso3 of 10% by weight added.
After this, thermal decomposition is performed at 250 qo. After repeating this operation five times, colloidal carbon, silver paint, and solder were successively laminated thereon to construct a solid electrolytic capacitor. The performance of this solid electrolytic capacitor (product of the present invention) is Mh0
Solid electrolytic capacitor using only 2 as solid electrolyte (
Table 1 shows a comparison with the performance of the conventional product. In Table 1, method A is the case where 3 is added to R for all the Mn(N03)2 in the thermal decomposition, and method B is the case where Mn(N03)2 at the initial stage of thermal decomposition is added.
This is the case where RuC〆3 is added only to the above. Table 1 (Example 2) On the surface of the cylindrical Ta adjacent silk body on the diameter 2.3 side and height 3 side,
A 18V Ta24 film is formed using phosphoric acid to constitute an anode body.

This anode body was immersed in a solution of R with a concentration of 10%,
After this, thermal decomposition is performed. After repeating this operation five times, colloidal carbon, silver paint, and solder are successively laminated thereon to form a solid electrolytic capacitor. In addition to solid electrolytic capacitors in which the solid electrolyte is composed only of Ru02, Mn(NQ)2 is appropriately added during the thermal decomposition of the R core
A solid electrolytic capacitor having a solid electrolyte with a structure in which Ru02 and Mn02 are laminated was also fabricated as a sample by thermal decomposition.

The performance of these two types of solid electrolytic capacitors (products of the present invention) is M
Table 2 shows a comparison of the performance of a solid electrolytic capacitor whose solid electrolyte consists of only 2. Table 2 As is clear from Experimental Examples 1 and 2, Ru0 is used as a solid electrolyte for capacitors.
By using a mixture of Ru02 or Ru02 and Mn02, the capacity and capacity achievement rate are increased, and the
6. LC becomes stable and low, and the frequency characteristics of the capacitance also become very good.

Although omitted in the above explanation, Ru, lr, Re, R
It is also possible to use a mixture of various combinations of h and 0s oxides, and it is not limited to using them alone, such as only Ru oxide or only lr oxide.

As is clear from the above description, the solid electrolytic capacitor according to the present invention uses Ru, lr, Re, Rh as solid electrolytes.
, MN02 or their oxides (RO02, lr02, Re02,
Rh02, 0s02), which basically consists of at least one of the following: This has a high capacity achievement rate, stable low tan6 and LC, and also has very good capacitance frequency characteristics. A solid electrolytic capacitor with excellent electrical characteristics can be obtained.

In addition, R, etc. are expensive, but as mentioned above, Mn (
When used in combination with NQ)2, high performance can be obtained at low cost, and it is very effective in terms of manufacturing and performance improvement. As described above, the present invention provides a completely new solid electrolyte for solid electrolytic capacitors, and greatly contributes to the technological development of solid electrolytic capacitors.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram to explain the formation ability of the manganese dioxide layer in a general solid electrolytic capacitor, Figure 2 is an electrical equivalent circuit diagram of a general solid electrolytic capacitor, and Figure 3 shows the formation ability of ruthenium oxide. Fig. 4 is an electric circuit diagram for measuring the chemical formation ability of ruthenium oxide using the sample shown in Fig. 3, Fig. 5 is a chemical formation current curve diagram of ruthenium oxide, and Fig. 6 is a front view of the sample prepared for investigation. 7 is a schematic cross-sectional view showing the main structure of a solid electrolytic capacitor according to another embodiment of the present invention. FIG. 8 is a schematic cross-sectional view showing the main structure of a solid electrolytic capacitor according to another embodiment of the present invention. is Mn(O
H)2-Mn(N03)2NN03-300% of the solid electrolyte layer produced by thermally decomposing a slurry-like pyrolyzable solution produced by adding So3 to R on 20 days.
This is a scanning electron micrograph of Piao. 0 11,16...Tantalum (Ta) substrate (valve metal base), 12,16...Tantalum oxide (Ta)
205) Film (dielectric oxide film), 13, 18...
Manganese dioxide (Mn02) layer (solid electrolyte layer), 14
...Ruthenium oxide (Ru02), 17...Ruthenium oxide (R2) layer. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. An anode body is formed by forming a dielectric oxide film on the surface of a valve metal base, and a solid electrolyte layer, a cathode layer, and a cathode conductor layer are formed on the dielectric oxide film of the anode body. The solid electrolyte layer is manganese dioxide containing at least one selected from the metal group consisting of ruthenium, iridium, rhenium, rhodium, and osmium, or at least one selected from the above metal group. A solid electrolytic capacitor characterized by being basically composed of oxides. 2. The solid electrolyte layer is formed by laminating manganese dioxide containing at least one selected from the metal group consisting of ruthenium, iridium, rhenium, rhodium, and osmium and at least one oxide selected from the metal group. A solid electrolytic capacitor according to claim 1.