JPS602769B2 - solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid electrolytic capacitor having an anode substrate made of a valve metal such as tantalum (Ta) or aluminum (A), and particularly relates to the solid electrolyte of this solid electrolytic capacitor. .

Generally, in solid electrolytic capacitors, Ta is often used in the base of the anode body, and the anode body is constructed by forming a tantalum oxide (Ta205) film, which is a concessionary oxide film, on the surface of the Ta base body. A solid electrolyte layer is formed on the Ta205 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, is extremely thin with a thickness of 50 to 2000 A, and has a high dielectric constant of 20 to 30, forming the capacitance portion of the capacitor. By the way, the Ta205 film produced in this way also has many defective points within the film, and when used as a capacitor, the leakage current increases due to the defective points. A problem arises in which the current flows in a concentrated manner. At this time, Ta205
The solid electrolyte layer formed on the film allows the collective electrolyte layer to thermally or electrochemically remove defects from the Ta205 film.
2-ions are supplied to repair the defective points in the Ta2Q film, and the leakage current in the Ta205 film becomes low.
This kind of action is generally called "self-repairing action." That is, the solid electrolyte layer formed on the Ta205 film is T
By supplying oxygen to the 05 film, the leakage current of the capacitor is lowered and the withstand voltage is increased. Therefore,
The solid electrolyte of the solid electrolytic capacitor must firstly be a metal oxide that has a large ability to supply oxygen to 05, that is, it must be a metal oxide with strong oxidizing power, and secondly, it must be a metal oxide that has a strong oxidizing power, and secondly, it must be used to reduce tan6, which is the resistance component of the capacitor. The capacitor is required to have low electrical resistance, and is required to be able to maintain good capacitor characteristics, n6, and leakage current (LC). Currently, manganese dioxide (MnQ) and lead dioxide (Pb02) are commonly used as solid electrolytes because they satisfy the above-mentioned conditions and are inexpensive.

The suitability of MN02 and Pb02 as this solid electrolyte will be explained using FIGS. 1 to 3. The equivalent circuit of an electrolytic capacitor is generally expressed as shown in Figure 1,
C is the capacitance of the T05 film, R is the resistance of the Ta2Q film which is also a dielectric oxide film, R2 is the resistance caused by the solid electrolyte and other lead wire extraction parts, and n6 is as shown in the following formula. can be expressed. tan6 ni CR ni C
(RI+R2)CR2 of CRI+CR2 in this formula,
Since is the resistance of the Ta205 film, it is related to the anodization conditions and other conditions, and CR2 is due to the physical properties of the solid electrolyte and is greatly influenced by its thickness, thermal decomposition, adhesion state, and electrical resistance.

That is, using Mn02 or Pb02, which have low electrical resistance, as the solid electrolyte reduces the CR2 and the tan6 of the capacitor. In addition, in order to confirm the oxygen supply ability of Mn02, a Mn02 layer 2 was formed on the Ta substrate 1 as shown in FIG.
A sample 4 with a gold electrode 3 formed by vapor deposition on the n02 film 2 is connected to a Ta substrate 1 in a closed circuit between a constant voltage DC power source 5 and an ammeter 6.
was inserted and connected to the gold electrode 3 as an anode and as a cathode, and a constant voltage was applied to the sample 4 to examine the chemical formation current.

In addition, in FIG. 2, 7 is a recorder for recording the numerical value of the ammeter 6. The result of this experiment is shown in the chemical formation current curve diagram of FIG. 3, from which it can be seen that a Ta205 layer is formed at the interface between the Ta substrate 1 and the Mn02 film 2.

In this way, Mn is used as a solid electrolyte in solid electrolytic capacitors.
02 indicates suitability. By the way, if a substance that has an oxygen supply capacity equal to or greater than Mh02 and has better electrical conductivity than Mn02, that is, has lower electrical resistance, is used as the solid electrolyte, a solid electrolytic capacitor with even higher performance can be obtained. It is conceivable that this can be done.

Focusing on this point, Mn02 (P=10-1~1#○ skin)
Ruthenium oxide (Ru02) with lower resistance (P=10
The present inventors have previously proposed a solid electrolytic capacitor using Mm02 as an electrolyte either alone or in a mixed form with Mm02. As can be seen from the above, solid electrolytic capacitors using this R mountain 02 alone or mixed with Mn02 as a solid electrolyte have a low tar16, LC by using Ru02, which has low resistance and high oxygen supply ability. Furthermore, when a sintered body is used as the anode substrate, the resistance loss due to the solid electrolyte inside the pores of the competitive body is reduced, so the cathode current collection ability of the capacitor is superior to that of MN02, which has a high resistance, and the capacity is achieved. The number of pyrolysis cycles required to form electrolytes can be drastically reduced. The present invention relates to a solid electrolytic capacitor using such a Mn02-Ru02 solid electrolyte.
The present invention provides a solid electrolytic capacitor that is inexpensive and has a high capacity achievement rate.

Hereinafter, explanation will be given using the drawings of FIGS. 4 to 6.

FIG. 4 is an enlarged cross-sectional view of the Ta compact body which is the anode base body, and shows the inside of the compact body 10 with the anode internal lead 9.
There are about 0 to 50 pongee holes 11 that communicate with each other, and the ends of these pongee holes 11 are all connected to the surface 12 of the kyobond body 10.
is familiar with

In addition, a part of the solid electrolyte layer 13 made of MnQ, Ru02, etc. is impregnated with a thermally decomposable mother liquor containing these metals such as nitrates and chlorides, and is subjected to repeated thermal decomposition. Can be packed. By the way, Mn02,
After forming a solid electrolyte layer 13 such as Ru02, a cathode layer 14, which is a current collecting electrode, is formed on the solid electrolyte layer 13 using colloidal carbon or the like. In order to make the current collection of the Yuka body more reliable,
When Mh02 is used as the solid electrolyte, thermal decomposition of Mn(N03)2 is required multiple times in order to improve the above-mentioned capacity extraction effect. This required number of times is
The diameter varies depending on the shape, size, etc. of the
When using a candle and a cylindrical bran aggregate 10 with a height of 1 mound, at least 5 to 7 times are required. That is, when considering the equivalent circuit of the competitive body 10 shown in FIG. 5, in order to extract the capacitance C3 of the dielectric oxide film inside the pores 11, the resistance of the cathode lead up to the surface of the solid electrolyte layer 13 is reduced. Therefore, it is necessary to form a sufficient amount of solid electrolyte inside the pongee hole 11, and the number of times of thermal decomposition must be increased. However, if a substance with low electrical resistance is used as the solid electrolyte packed inside the pores 11, even if it adheres to the inside of the pores 11,
The internal capacity can be taken out more effectively. In other words, when R2 is used alone or added to Mh02 as a collective electrolyte, an electrolyte with low electrical resistance
1, and due to a small number of thermal decompositions, the oxidized film inside the tsumugi hole 11, which is far from the surface, and the dielectric oxide film on the surface 12 of the Akatsuki compact 10 become electrically equivalent. be.

To explain this using the equivalent circuit shown in FIG. 5, since the cathode extraction resistance R, 3 near the center of the stripe-resistant body 10 is very small, the cathode extraction resistance R, . and the cathode extraction resistance R at the intermediate portion between the surface 12 and the center of the Akatsuki compact 10.
, 2 and the cathode extraction resistance R, 3 near the center of the anti-consolidation 10
are almost equal to each other, and the number of operations for filling the solid electrolyte into the pores 11 of the Akatsuki compact 10 can be reduced compared to the conventional solid electrolyte using MN02 alone. In the equivalent circuit shown in FIG. 5, C is the capacitance of the dielectric oxide film near the surface 12 of the dawning body 10, and C2 is the capacitance of the dielectric oxide film in the intermediate area between the surface 12 and the center of the sintered body 10. capacity. Also,
For reference, in the case of a solid electrolyte using Mn02 alone, the cathode lead resistances R, . ,R,2,R,3 is R,. <
R,2<R,3. When the capacity extraction efficiency described above is expressed quantitatively, it is considered that the solid electrolyte with a larger capacity achievement rate solidified capacity (wet capacity x 100) at the same number of thermal decompositions has a higher capacity extraction efficiency.

・Figure 6 shows the relationship between the capacity extraction efficiency (capacity achievement rate) calculated in this way and the atomic ratio of Ru and Mn in the solid electrolyte, and the capacity extraction efficiency increases as the Ru ratio increases. However, when the Ru/Mn atomic ratio is 1 or more, it is almost saturated.

In other words, as for the optimum composition of Ru and Mn, based on the price of Ru and the results shown in Figure 6, the appropriate upper limit is a composition in which the atomic ratio of Ru/Mn is 1 or less, and the lower limit is a composition in which the atomic ratio of Ru/Mn is 1 or less. The capacity extraction effect due to the use of Ru as the solid electrolyte must be confirmed, and as shown in FIG. 6, a composition in which the Ru/Mn atomic ratio is 10-6 or more is appropriate.

Therefore, 2 of R may be used alone, but from the above, Ru
If the atomic ratio of Ru02 and Mn is set to a composition of 1 to 10x6, the capacity extraction efficiency can be increased to the same degree as when Ru02 is used alone, and the amount of expensive Ru metal can be reduced. It can be made cheap. In addition, RW0
When obtaining a 2-Mh02 solid electrolyte, Mn(N03)
Mn(N03)2 produced by adding 〆3 to R in 2
, RuC 3. The anode substrate with a dielectric oxide film formed on the surface may be immersed in a mixed solution and thermally decomposed. However, in this case, only R2 is not necessarily generated, and Mm02 contains R and Y3. Intermediate products are also produced. However, this R
A mixed oxide containing 10 R and 40 Ru, which is an intermediate product of uC3, can also be used because it has the ability to form solids.
As is clear from the above description, the solid electrolytic capacitor of the present invention uses a solid electrolyte layer that is basically composed of Mn02 containing Ru and has a composition in which the atomic ratio of Ru and Mn is 10-6 to 1. If Mm02 is used alone as a solid electrolyte, the resistivity of Md02 is relatively high, so if a large sintered striped body is used as the anode substrate, Mn02 will be added to the pores of the sintered body. Thermal decomposition is performed to form a low concentration of Mn (N03
)2 had to be thermally decomposed 5 to 7 times, but in the case of the Ru02-M 2 system of the present invention, since Ru02 has low resistance, thermal decomposition can be performed only about 3 times, and moreover, R
Since the composition is such that the atomic ratio of u and Mn is 10-6 to 1, the capacitance extraction effect required for a solid electrolytic capacitor of 0 can be obtained without increasing the price too much.

Furthermore, since the resistance of the solid electrolyte is lowered, it becomes possible to use a thermally decomposable mother liquor with a relatively high concentration, thereby making it possible to obtain a high-performance solid electrolytic capacitor with a low tan6, LC.

As described above, the solid electrolytic capacitor of the present invention can provide very excellent effects and is of high industrial value.

0 Brief explanation of drawings Figure 1 is an equivalent circuit diagram of a general solid electrolytic capacitor, Figure 2 is an equivalent circuit diagram of a general solid electrolytic capacitor.
The figure is an electric circuit diagram for measuring the chemical conversion ability of manganese dioxide, Figure 3 is a chemical conversion current curve diagram of manganese dioxide, and Figure 4 is a chemical conversion current curve diagram of manganese dioxide.
The figure is an enlarged cross-sectional view of a burnt body used in a general solid electrolytic capacitor, Figure 5 is an equivalent circuit diagram of a capacitor using the same burnt stripe, and Figure 6 is the relationship between the atomic ratio of ruthenium and manganese and the capacity extraction efficiency. It is a characteristic diagram showing a relationship.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1 A dielectric oxide film is formed on the surface of a valve metal base to constitute an anode body, and on the dielectric oxide film of the anode body, the ruthenium and manganese are basically composed of manganese dioxide containing ruthenium. The atomic ratio of is 10^
- A solid electrolytic capacitor characterized in that a cathode layer and a cathode conductor layer are sequentially laminated on a solid electrolyte layer having a composition of 6 to 1.