JPS61248514A - 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 This invention relates to a solid electrolytic capacitor using an electrolyte having a complex salt of 7,7,8,8-tetracyanoquinodimethane (hereinafter abbreviated as TCNQ) as the main component of an organic semiconductor. It is something.

2. Description of the Related Art In recent years, with the digitization of electronic devices, it has been desired to reduce the high frequency impedance of the capacitors used. In addition, electrolytic capacitors have traditionally been used as bypass capacitors due to their small size and large capacity.
With the recent development of electronic devices, improvements are desired, especially in terms of high-frequency impedance at low temperatures, stability at high temperatures, and long-term life stability. Conventionally, plastic film capacitors have been used as high-frequency capacitors.

Mica capacitors, multilayer ceramic capacitors, etc. are used. Film capacitors and mica capacitors are large in size, so it is difficult to increase their capacitance, and multilayer ceramic capacitors have drawbacks such as extremely poor temperature characteristics and high price when it comes to large-capacity products. On the other hand, aluminum dry electrolytic capacitors or tantalum solid electrolytic capacitors use a very thin anodic oxide film as a dielectric material to achieve large capacity, but on the other hand, the oxide film is easily damaged. In addition, it is necessary to provide an electrolyte layer between the oxide film and the cathode to repair damage from time to time. For example, in an aluminum electrolytic capacitor, an anode/cathode aluminum foil whose surface area has been increased by etching is wound up with a paper separator in between and impregnated with a liquid electrolyte to form an element. For this reason, disadvantages such as an increase in impedance at high frequencies and low temperatures due to the ionic conductivity of the electrolyte, and a decrease in capacitance over time and an increase in loss due to leakage of the electrolyte occur, making it difficult to use as an industrial capacitor. is restricted. In this sense, aluminum and mental solid electrolytic capacitors are
Although these are small, large-capacity capacitors that have improved the drawbacks of the aluminum electrolytic capacitors mentioned above, these also have some drawbacks.

In manufacturing these solid electrolytic capacitors, an anode is immersed in an aqueous solution of manganese nitrate and thermally decomposed in a high temperature furnace at around 350'C to produce a solid electrolyte made of manganese dioxide. In this case, it shows far superior frequency characteristics, temperature characteristics, and life characteristics compared to liquid electrolytes, but
Damage to the anodic oxide film due to thermal decomposition several times at high temperatures,
Also, because manganese dioxide has a high specific resistance and exhibits a semiconductor-like electrical conduction pattern, the impedance or loss in high frequency and low temperature regions remains at a considerably higher value than the above-mentioned film capacitor. Here, in order to improve the drawbacks of these capacitors, it has been proposed to use an organic semiconductor with high conductivity and excellent anodic oxidability as a solid electrolyte. In particular, organic semiconductors made of TONQ complex salts can be impregnated onto oxide films by dissolving them in organic solvents or melting them by heating, and can be applied to oxide films by thermal decomposition that occurs when impregnating manganese dioxide. The applicant's invention (Japanese Patent Publication No. 58, 1983) shows good high frequency characteristics and large capacity by using TCNQ salt which can reduce damage and has metallic conductivity.
-10777 Publication) and the invention by Shin Niwa et al.
JP-A-68-17609 or JP-A-68-1
91414) etc., quinoline, inquinoline, and pyridine substituted with an alkyl group at the N position are used as cations,
A complex salt containing two molecules of TCNQ is known. These salts have a clear melting point when the number of carbon atoms in the alkyl group is 3 or more, so they are impregnated into the capacitor by heating and melting, making it possible to form a uniform solid electrolyte layer on the oxide film. . However, when the above-mentioned materials are used alone as solid electrolytes, several drawbacks occur and fundamental improvements are required.

A disadvantage is the generation of toxic gases due to thermal decomposition of the TCNQ salt. In the event of a fire or some form of overheating, the TCNQ salt decomposes and releases toxic nitrile compound gases. In the method of impregnating a capacitor unit by thermal melting, if the TCNQ salt decomposes without melting, or if the retention time in a stable liquid state is short even after melting, TCNQ salt (the composition of the NQ salt has changed) In addition, if the hot molten liquid state decomposes within the time period of one impregnation operation, TC
This means that some of the NQ salt is wasted, which is a disadvantage from a cost standpoint.

SUMMARY OF THE INVENTION The present invention aims to eliminate such drawbacks, and aims to provide a solid electrolytic capacitor with a large capacity, low loss, and excellent high frequency characteristics, which suppresses the generation of toxic gas and improves the efficiency of electrolyte impregnation work. That is.

Means for Solving the Problems The present invention achieves the above object, and the basic structure of the solid electrolytic capacitor of the present invention is that a valve metal having an oxide film formed by anodizing is used as the first electrode. A complex salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ complex salt) and yohypentaerythritol tetrapromide is connected between the second electrode (called cathode or counter electrode) and this first electrode. It has a mixture as a solid electrolyte.

Effect of the present invention By mixing TONQ complex salt with pentaerythritol tetrabromide, TCNQ complex salt, which is difficult to melt by itself, can be melted, and a stable molten liquid state can be obtained. As a result, the impregnation properties of the capacitor unit can be improved and high performance solid electrolytic capacitors can be replaced. Furthermore, due to improved thermal stability, toxic gases caused by thermal decomposition can be largely suppressed.

The electrolyte used here does not necessarily have to be thermally molten; instead, it may be one that dissolves in the thermally molten liquid of pentaerythritol tetrabromide ((j(CH2Br)4).The melting point of this substance is 158- 16
It is 0°C.

TO)fQ complex salts may be a mixture of two or more types, if necessary, in order to improve both capacity value and loss.

In addition, pentaerythritol is added to pentaerythritol, which is impregnated by hot melting with a complex salt containing two molecules of TCNQ per molecule of quinoline or inquinoline whose N-position is substituted with normal alkyl, such as butyl, hexyl, or pentyl, which is longer than propyl. By adding tetrabromide,
The capacitor unit can be impregnated at a temperature lower than the melting point of the TCNQ salt itself. Furthermore, thermal decomposition of the TCNQ salt is suppressed even at temperatures above the melting point of the TCNQ salt itself.

The conductivity of the electrolyte of TcNQ salt varies depending on the material, but until now there have been some that have excellent conductivity but are prone to thermal decomposition and cannot be used in capacitors because they cannot be returned to a stable molten state, but pentaerythritol It can be used by making an electrolyte mixed with bromide. Even in the case where the N-position described above is substituted with an alkyl group, the stain conductivity differs depending on the length of the alkyl group. Furthermore, the impregnability of the capacitor unit also varies depending on the length of the alkyl. Therefore, by combining TCNQ salts with excellent conductivity and impregnating properties, it is possible to obtain excellent capacitor characteristics. The maximum amount of pentaerythritol tetrabromide to be added is about 60 parts by weight, at which deterioration of capacitor characteristics is seen, but it cannot be uniformly specified because it varies depending on the material. The minimum amount is about 6 parts by weight.
A clear effect can be seen in the melting phenomenon.

Examples (Example 1) n-Butylisoquinolinium (T
1 to 100 parts by weight of pentaerythritol tetrabromide was added to CNQ)2 and mixed well. This powder was placed in an aluminum case and melted at 250°C. It became a molten liquid state within 6 seconds, and remained stably in a liquid state even after about 3 minutes. A rolled-up aluminum electrolytic capacitor unit was immersed in this molten liquid and rapidly cooled to room temperature in about 10 seconds after immersion. At this time, the capacitor unit used was one in which the aluminum end face was chemically treated, and a comparison was made between cases where preheating was performed before impregnation with the organic semiconductor and cases where preheating was not performed. Table 1 shows the initial characteristics of the solid electrolytic capacitor obtained.

Table 1 ■ As described above, there was no significant change in capacitor characteristics up to about 76 parts of penteerythritol tetrabromide. It has also been found that by adding penteerythritol tetrabromide, when impregnating the unit with electrolyte, the unit can be impregnated without preheating the unit, and good capacitor characteristics can be obtained.

<Example 2> n-hexylisoquinolium (T
When CNQ) 2 was heated to 250'C and the unit was preheated and impregnated, the capacitor had a high conductivity, so a good capacitance value was obtained, but the loss was poor.

For example, the capacitance value is 2.85MF.

The loss is 8% (120H2). By mixing this with n-butylisoquinolium (rcNQ), which has good conductivity, it is expected that a capacitor with excellent capacitance and loss can be produced, but the composition changes due to thermal decomposition during heating and melting. The capacitor characteristic values vary, probably due to the influence of Therefore, 60 parts by weight of n-hexyl inquiturium (TCNQ) 2 and n-butylisoquinolium (TCNQ) z were mixed, and 10 parts by weight of pentaerythritol tetrabromide were added and mixed well. 26 to the capacitor unit.
Impregnation was performed by heating and melting at 0°C. Preheating the unit is 1
Impregnation was carried out in the same manner as in Example 1 for those with and without impregnation, and the capacitor characteristics were measured.
Capacity was 2.8MF, loss was about 2% (120Hz), and excellent capacitor characteristics were achieved.

<Example 3> When impregnating a capacitor unit by heating and melting n-butylisoquinolium (TCNQ), when heated to 250° C., a stable molten liquid state takes about 1 minute. n-butylisoquinolium (TCNQ) 2100
An electrolyte to which 10 parts by weight of pentaerythritol tetrabromide was added could maintain a stable molten liquid state for about 6 minutes even when heated to 250°C.

When the heating temperature is further lowered, it takes longer to melt, but even when heated at 210° C., it melts in about 1.5 to 2 minutes, making it possible to impregnate the capacitor unit. As for the capacitor characteristics, a unit similar to that in Example 1 was used, and the capacitance was 2.5 MF and the loss was 1.
8% (120H2) was obtained.

<Example 4> It was shown that adding petaerythritol tetrabromide to the electrolyte used in Examples 1 and 2.3 stabilized the liquid state during hot melting, but after impregnating the capacitor, Thermal stability of electrolytic capacitors is also improved.

First, the operating temperature range is also determined by the thermal characteristics of the exterior material. If a resin with good heat resistance is used, the operating temperature can be 100℃.
It exhibits sufficiently stable characteristics up to a certain point.

When one person applied a reverse current to the electrolytic capacitors made in Examples 1 and 2.3 without the outer packaging material and examined the generation of decomposed gas, the amount of HCH generated was lower than that of the capacitors without pentaerythritol tetrabromide. The amount of 1%/β added was 20 ppm/J or less, and it was found that it has a wide range of toxic gas suppression effects.

Effects of the Invention The present invention provides a capacitor using a TCNQ complex salt to which pentaerythritol tetrabromide is added as an electrolyte for a solid electrolytic capacitor.

Claims (3)

[Claims] (1) A mixture of a complex salt of 7,7,8,8-tetracyanoquinodimethane and pentaerythritol tetrabromide is placed between an anodized valve metal as an anode and a cathode placed opposite thereto. A solid electrolytic capacitor characterized by having as a solid electrolyte. (2) The solid electrolytic capacitor according to claim 1, comprising two or more types of complex salts of 7,7,8,8-tetracyanoquinodimethane. (3) Use a complex salt consisting of one molecule in which the N-position of quinoline or isoquinoline is substituted with an alkyl group -C_nH_2_n_+_1 (n=0 to 18) and two molecules of 7,7,8,8-tetracyanoquinodimethane. A solid electrolytic capacitor according to claim 1 or 2.