JPS63160221A - Aluminum solid electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an aluminum solid electrolytic capacitor, and more specifically, an aluminum solid electrolytic capacitor which is composed of two solid electrolytes, manganese dioxide and lead dioxide, and has improved performance. It is related to capacitors.

(Prior Art) Conventionally, it is generally known that manganese dioxide is used as a constituent of a solid electrolyte layer. Techniques that use lead dioxide in addition to manganese dioxide are known, for example,
According to Japanese Patent Publication No. 29374, it is disclosed that the use of lead dioxide provides a superior improvement in frequency vs. loss coefficient over capacitors using manganese dioxide.

(Problems to be Solved by the Invention) The present inventors have investigated the characteristics of manganese dioxide and lead dioxide as solid electrolytes for aluminum solid electrolytic capacitors.
In addition to the frequency vs. loss coefficient, other important characteristics of capacitors were also considered. The results show that manganese dioxide has a capacity ratio of almost 100%, while lead dioxide has a capacity ratio of 100%, as shown in Figure 1. It can be seen that as the pit diameter decreases, the capacity ratio decreases significantly.

Further, as shown in Table 1, the initial leakage current is quite large for manganese dioxide, but in the case of lead dioxide, it is about Iθ% of the value for manganese dioxide. However, it was discovered that by first forming a manganese dioxide layer on the aluminum oxide film and then forming a lead dioxide layer, the above-mentioned drawbacks could be significantly improved and the performance of the capacitor could be improved, and the present invention was completed. It is.

Therefore, an object of the present invention is to provide an aluminum solid electrolytic capacitor whose performance is improved by using a combination of manganese dioxide and lead dioxide as the solid electrolyte of the aluminum solid electrolytic capacitor.

(Means for Solving the Problems) In order to achieve the above object, the aluminum solid electrolytic capacitor according to the present invention uses manganese dioxide, which is in contact with the aluminum oxide film and accounts for 5 to 60% of the thickness of the solid electrolyte, as the solid electrolyte. 2FJ layer and a lead dioxide layer in contact with the manganese dioxide layer. It is characterized by

The manganese dioxide layer is formed by applying manganese nitrate by a conventional method and heating and decomposing it at a high temperature to form a manganese dioxide layer several times.

The lead dioxide layer is formed by the above-mentioned known method, that is, the manganese dioxide M is immersed in a mixed solution of a lead acetate solution, an ammonium persulfate solution, and an ammonium acetate solution and heated to precipitate the lead dioxide layer.

(Function) Since manganese dioxide is formed by high-temperature decomposition, it is thought that stress etc. are applied to the aluminum oxide film, increasing the initial leakage current.

However, lead dioxide precipitates as a colloid under relatively mild conditions, and a lead dioxide layer grows using this colloid as a core, which compensates for the damage to the aluminum oxide film and improves the initial JgJ leakage current. I think that the. on the other hand,
The precipitation mechanism of the lead dioxide layer is that when the aluminum etching pit becomes small, narrow, and complicated, the lead dioxide layer cannot be formed deep into the bit, so as the pit diameter becomes smaller, the capacity ratio decreases significantly. It is thought that compensation can be achieved by first forming a manganese dioxide layer and then forming a lead dioxide layer thereon. In the end, it seems that the effects of the present invention can be obtained by compensating for each other's shortcomings.

(Effects of the Invention) According to the aluminum solid electrolytic capacitor according to the present invention, the tan
Provides an aluminum solid electrolytic capacitor with significantly improved capacitor performance, with better δ, BSR, lower initial leakage current, and higher foil capacity ratio than lead dioxide alone solid electrolyte. I can do it.

(Example) Next, the present invention will be explained with reference to Examples and Experimental Examples.

Experimental Example 1 The relationship between pit diameter (μm) and capacity ratio (%) was measured. When using manganese dioxide alone as 100, when using lead dioxide alone and manganese dioxide, lead dioxide = 20:8
The value in the case of 0 is shown in the graph of FIG.

In the case of manganese dioxide, the capacity ratio decreases significantly as the pit diameter becomes smaller, and this drawback is shown to be significantly improved by the combination of manganese dioxide and lead dioxide.

Experimental Example 2 The X-axis is the thickness of the manganese dioxide layer and the thickness of the lead dioxide layer relative to the total thickness of the solid electrolyte that uses both manganese dioxide and lead dioxide. (Rated as 100 for manganese alone)
, the result of taking ta mouth δ on the right Y axis is shown in the graph of FIG. In this case, the aluminum foil used was electrochemically etched with a pit diameter of 0.3 μm.

This graph shows that a manganese dioxide layer of 5 to 60% is suitable as an example. Three types of solid electrolytes were used: manganese oxide alone, lead dioxide alone, and manganese dioxide layer thickness and lead dioxide alone = 30:70. Assemble standard aluminum solid electrolytic capacitors with the same thickness rating 10V-2, 2μF to calculate the capacitance (μF),
tan δ (tangent of loss angle) and leakage current (μA) were measured. The results are shown in Table 1.

Table 1

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between pit diameter and capacity ratio when lead dioxide alone and manganese dioxide/lead dioxide are used together as a solid electrolyte. Figure 2 is a graph showing the relationship between manganese dioxide/lead dioxide thickness ratio and capacitor characteristics (capacity ratio, It is a graph showing the relationship between tan δ). Patent applicant Nippon Chemi-Con Co., Ltd. FIG, 1 FIG, 2

Claims (1)

[Claims] (1) In an aluminum solid electrolytic capacitor, the solid electrolyte is composed of two layers: a manganese dioxide layer in contact with an aluminum oxide film and accounting for 5 to 60% of the thickness of the solid electrolyte, and a lead dioxide layer in contact with the manganese dioxide layer. An aluminum solid electrolytic capacitor characterized by: