JPS62111413A - 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 the Invention The present invention relates to a solid electrolytic capacitor using an improved organic semiconductor as a solid electrolyte.

BACKGROUND OF THE INVENTION In recent years, with the digitization of electrical equipment circuits, there has been an increasing demand for capacitors used therein that have low impedance in the high frequency range and are small and large in capacity.

Conventionally, plastic film capacitors, mica capacitors, and multilayer ceramic capacitors have been used as capacitors for high frequency ranges, but film condensers and mica capacitors have large shapes, making it difficult to increase capacity, and multilayer Ceramic capacitors have the disadvantage that the smaller and larger the capacitance, the worse the temperature characteristics and the higher the price. On the other hand, known high-capacity type capacitors include aluminum dry electrolytic capacitors and aluminum or Kuntal solid electrolytic capacitors. These capacitors can achieve large capacitance because the anodic oxide film that serves as the dielectric can be made very thin, but on the other hand, the oxide film is easily damaged, so damage must be repaired between the oxide film and the cathode. It is necessary to provide an electrolyte for this purpose. In an aluminum dry electrolytic capacitor, etched positive and negative electrode aluminum foils are wound up with a paper separator in between, and the separator is impregnated with a liquid electrolyte.

For this reason, capacitance decreases and loss (tan δ) increases over time due to electrolyte leakage, evaporation, etc., and at the same time, high-frequency characteristics and low-temperature characteristics deteriorate significantly due to the ionic conductivity of the electrolyte. It has drawbacks. Furthermore, in aluminum and tantalum solid electrolytic capacitors, manganese dioxide is used as the solid electrolyte in order to improve the drawbacks of the above-mentioned aluminum dry electrolytic capacitors. This solid electrolyte is prepared by immersing the anode element in a manganese nitrate aqueous solution.
It is obtained by thermal decomposition at a temperature of around 50°C. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as electrolyte leakage at high temperatures or performance degradation caused by solidification at low temperatures, and it has better frequency and temperature characteristics than capacitors using liquid electrolytes. However, due to damage to the oxide film due to thermal decomposition of manganese nitrate and the high resistivity of manganese dioxide, the impedance or loss in the high frequency range is more than an order of magnitude higher than that of multilayer ceramic capacitors or plastic film capacitors. value.

In order to solve the above problems, organic semiconductors (7, 7, 8
, 8-tetracyanoquinodimethane complex). This organic semiconductor can be applied to the oxide film by dissolving it in an organic solvent or by melting it by heating, and can prevent damage to the oxide film due to thermal decomposition that occurs when impregnating M n O2. be able to. The TCNQ complex has high conductivity and excellent anodic oxidation properties, and has good high frequency characteristics, making it possible to create a large capacity capacitor. For example, by Mr. Shin Niwa, N-n-propyl or N-1st-propylisoquinoline and TC
An application has been filed for an invention in which an organic semiconductor composed of NQ is used as a solid electrolyte (Japanese Unexamined Patent Publication No. 17609/1983).

According to the invention, the TCNQ salt is impregnated into the wound aluminum electrolytic capacitor by heating and melting the 7r CN Q salt, thereby achieving a strong bond between the TCNQ salt and the oxide film, and increasing the Thanks in part to its electrical conductivity, aluminum capacitors with significantly improved frequency and temperature characteristics will be produced. The use of such an organic semiconductor based on TCNQ salt as a solid electrolyte has already been shown in an invention filed by the same applicant (Japanese Patent Publication No. 17609/1983), in which TCNQ salt is more effective than manganese dioxide. Because it has high conductivity and high anodic oxidation ability (restoration effect), it enables superior performance in both frequency and temperature characteristics compared to solid electrolytic capacitors using manganese dioxide. According to the invention, the oxide film is impregnated with a TCNQ salt having a cation of isoquinolium substituted with an alkyl group at the N-position by heating and melting it.

Problems to be Solved by the Invention However, TCNQ salts using isoquinolium substituted with an alkyl group at the N-position have different thermal meltability and thermal stability depending on the alkyl group. Furthermore, since they differ in their impregnation properties into oxide films and their electrical conductivity, there are limits to what can be used as the alkyl group. Those in which the alkyl group is shorter than the ethyl group do not melt under heat. What the inventor mentions in the examples are propyl, isopropyl, and butyl groups. These also undergo oxidative decomposition if left in a hot molten state for a certain period of time.

Furthermore, since the 'r(,'NQ salt is a highly crystalline substance, it must be melted and impregnated and then rapidly cooled to form an amorphous state.

Regarding the capacitor characteristics, when the TCINQ salt undergoes oxidative decomposition or becomes highly crystalline, the conductivity particularly decreases and the loss becomes large. Capacity characteristics also vary depending on the length of the alkyl group, but there are problems such as the capacity achievement rate is about 80% for butyl groups.

The present invention is intended to solve these problems, and aims to improve the thermal melting properties of the electrolyte and the impregnating properties of the electrolyte into the oxide film, thereby improving the capacity characteristics and reliability of the life.

Means for Solving the Problems The present invention has been made to achieve the above object, and includes a first electrode having an oxide film on its surface, and a second electrode provided opposite to the first electrode. and the second electrode.
a solid electrolyte provided between the electrodes, the solid electrolyte having a cation of isoquinolium substituted with isoamyl at the N position and an anion of 7,7.8.8-tetracyanoquinodimethane; Ion radical complex salt and cation of quinoline or inquinoline substituted with decyl group or dodecyl group and 7.7.8
゜The second one with 8-tetracyanoquinodimethane as an anion
The ion radical complex salt of
The object of the present invention is to provide a solid electrolytic capacitor characterized in that the solid electrolytic capacitor is made of a mixture at a ratio of 10 to 100.

Function The present invention produces heat-melting properties by mixing isoquinolium whose N-position is substituted with an isoamyl group and one whose N-position is substituted with a decyl group or todecyl group as cations of TCNQ salt, which is a heat-melting solid electrolyte. In addition, the impregnability into the oxide film has been improved, and the reliability of capacity characteristics and service life has been improved.

The basic t'f/j composition of the solid electrolytic capacitor according to the present invention is that the valve metal (for example, aluminum, tantalum, titanium, and alloys thereof) having a positive oxide film on the surface by anodization (chemical conversion) is first developed. A solid electrolyte made of 'I''CNQ salt is provided between the second electrode (counter electrode) and the first electrode.

The characteristics of the present invention are a complex salt consisting of isoquinoline whose N-position is substituted with an isoamyl group and TCNQ, and a complex salt consisting of quinoline or inoquinoline whose N-position is substituted with a decyl group or dodecyl group and TCNQ. A feature is that a mixture of 100 to 10 to 100 (grain ratio) is used as the solid electrolyte. The material used in solid electrolytic capacitors in practical use is N-butylisoquinolium (TC
NQ)2, but TCNQ can improve the above problems.
Present the salt here.

According to DTA measurement, the melting point of N-n-butylisoquinolium (TCNQ'1.) is 215 to 220 °C,
If the temperature is higher than the melting point, it will be easily oxidized and decomposed, depending on the surrounding environment.

When this salt is melted in the atmosphere in an aluminum professional tank at a constant temperature of 250°C, it takes about 30 seconds to completely melt, and the stable thermal molten state is 1.
It takes about 5 to 60 seconds.

The melting point of N-in-amylisoquinolium (TCNQ) 2 is 225 to 2:30°C from I) T A measurement, and it was melted under the same conditions as in the case of N-n-butylisoquinolium (TCNQ) 2 above. When thermally melted, it takes 30 to 35 seconds to completely melt, and a stable molten liquid state takes 90 to 1.20 seconds.

By changing the N-alkyl group from an n-butyl group to an isoamyl group, the surface state is improved in the impregnating property into the oxide film etched into many micropores and the adhesion with the oxide film. However, in terms of capacity achievement rate, it is still 10%.
Characteristics reaching 0% have not been obtained.

If the N-position of quino or isoquinoline has a long alkyl group, for example, GnH2n + 1-, where n is to, 12
When substituted with 111.16 or the like, as n increases, the melting point decreases, thermal melting becomes easier, and the capacitance characteristics improve as the pores of the oxide film are more easily impregnated. The capacity achievement rate is almost 100% when n=16.

However, when actually substituting the N-position of quinoline or isoquinoline with a substance having a large n value, the larger n is, the worse the δ conversion rate is, and the formation of by-products is more likely.

In terms of capacitor characteristics, as n increases, capacitance improves, but tan δ characteristics deteriorate.

In addition, since the melting point is low (200° C. or less), the heat resistance characteristics as a capacitor deteriorate, and the characteristics deteriorate in the solder dip treatment process.

Here, the alkyl substitution reaction at the N position can be easily carried out, and it is easy to obtain a product with good purity. Therefore, we decided to use TCNQ salts of quinoline or inquinoline where n is 10 and 12, which can improve the fluorescent properties and lifespan.

The mixing ratio is N-isoamylisoquinolium (TCN
Q) 10 parts to 100 parts (weight ratio) is appropriate for 2100 parts.

If the amount is less than 10 parts, it hardly exhibits the characteristics of N-in-amylisoquinolium (TCNQ)2.

On the other hand, if 100 parts or more is mixed, the heat resistance and tan δ properties will deteriorate.

Example Examples of the present invention will be described in detail below.

<Example 1> N-in-amyl isoquinolium ('rCN
Q)2 and N-n-decylisoquinolium (TCNQ)2
The characteristics were compared using a mixture of the following and different mixing ratios. After pulverizing the electrolyte into a fine powder, it is placed in an aluminum can case (diameter 65 cm, height 6 m).
The required amount was filled into the container and melted on a hot plate at 250° C. to form a liquid.

Winding unit for wound aluminum electrolytic capacitors (
After sufficiently impregnating the sample (rated for 3μI'', 5QV), it was quenched using liquid N2 as a coolant.

Impregnation was carried out after placing an aluminum can case filled with electrolyte on a hot plate for 60 seconds.

The aluminum end face of the capacitor winding/taking-up unit was previously chemically treated. Finally, the exterior was treated using epoxy resin.

Next, Table 1 shows the results of measuring the capacitor characteristics at frequencies of 120I-Iz and IKl(z) and the capacitance change after being left at 85℃ and 100OH.The values in the table are the average of 10 capacitors using each electrolyte. It is a value.

Table 1 in the margin below *The number of electrolytes is N-isoamylisoquinolium (TC
This shows the proportion of N-n-decylisoquinolium ("r(,1NQ)2) when NQ)2 is 100 parts. (Weight ratio) <Example 2> Next, N-n-decylisoquinolium ( TCNQ')
Instead of 2, 'N-n-dodecylisoquinolium (
Table 2 shows the results when using ``rCNQ)2.

The same tendency of characteristics as in Example (2) was obtained.

Table 2 The number of electrolytes used was the same as in Example 1.

N-n-decyl (or dodecyl) ichchinolium (
As the mixing ratio of 'TCNQ)2 increases, the melting point of the electrolyte decreases. In both Examples 1 and 2, impregnation was carried out at 250°C, but when the mixing ratio was about 50 parts or more, the temperature was 220°C.
Good impregnation can be achieved even at temperatures around ℃.

Therefore, oxidative deterioration of the electrolyte is also prevented, and the capacitor characteristics (tan δ) are improved accordingly.

More specifically, the present invention achieves this effect by using a mixture of N-inoamylisoquinolium (TCNQ) 2 and N-n-decyl (or dodecyl) inquiturium (TCNQ) 2 as a solid electrolyte. rC, which has been put into practical use up to
The capacitor's characteristics and lifetime reliability were improved compared to capacitors using NQ salt.

Claims (1)

[Claims] a first electrode having an oxide film on its surface; a second electrode provided opposite to the first electrode; and the first and second electrodes.
a solid electrolyte provided between the electrodes, the solid electrolyte having a cation of isoquinolium substituted with isoamyl at the N position and an anion of 7,7,8.8-tetracyanoquinodimethane; Ion radical complex salt, a cation in which the N-position of quinoline or isoquinoline is substituted with a decyl group or dodecyl group, and 7, 7,
and a second ion radical complex salt having 8,8-tetracyanoquinodimethane as an anion in a weight ratio of 10.
A solid electrolytic capacitor comprising a mixture of 0:10 to 100: