JPH0466373B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a solid electrolytic capacitor using TCNQ salt as a solid electrolyte. (b) Prior Art A solid electrolytic capacitor has a structure in which a solid electrolyte is attached to a film-forming metal such as aluminum having an anodized film. In this type of capacitor, which has traditionally been mass-produced, the solid electrolyte that makes up the capacitor is mostly manganese dioxide, but in recent years, the weak points of manganese dioxide, namely, the anodization of the film-forming metal during thermal decomposition to form manganese dioxide, have been discovered. Organic semiconductors, mainly used as solid electrolytes to improve the damage to the film and the poor repairability of the anodic oxide film with manganese dioxide.
It was proposed to use TCNQ salt. Here,
TCNQ means 7,7,8,8 tetracyanodimethane. However, TCNQ salt is usually in the form of powder crystals, and although the crystals themselves have high conductivity and exhibit good repairability for the above-mentioned film, because they are powder crystals, they have difficulty in processability. That is, film-forming metals
The problem is how to attach TCNQ salt crystals. In particular, film-forming metals used in solid electrolytic capacitors are often porous, but it is extremely difficult to uniformly impregnate TCNQ salt onto such porous metals. What is more important is that TCNQ salt itself always carries the risk of deterioration due to alteration during the adhesion process. Conventionally proposed methods for attaching TCNQ salt can be classified into the following three types. (1) In solvents such as DMF (dimethylformamide)
Apply a solution of TCNQ salt to the above metal,
The method is then dried to remove the solvent by scattering. (2) A method in which TCNQ salt is made into fine crystals using a ball mill, etc., dispersed in alcohol, etc., and then applied to the above metal and dried. (3) A method of vacuum evaporating TCNQ salt onto the above metal. In method (1) above, DMF, which has high solubility for TCNQ salt, is used as a solvent, and such a solvent is
Even when heated to ℃, its solubility is limited to 10%. This means that it is necessary to apply and dry the solid electrolyte many times in order to adhere the necessary thickness of solid electrolyte to the foil-shaped metal, or to apply the solid electrolyte to the porous metal in a sufficient impregnation manner. It means something. For example, in the case of a porous metal with a rating of 1 μF, the impregnation rate that can be achieved by applying 5 to 10 times and drying is at most 30%, assuming that the impregnation rate when manganese dioxide is used as the solid electrolyte is 100%. At such a low impregnation rate, the capacitance value of the capacitor cannot be increased even though the metal is porous. Furthermore, the metal coated with a solvent is left in a high temperature during each drying process, and at this time more or less TCNQ
Deterioration of the salt occurs, leading to deterioration of the conductivity of the solid electrolyte. In addition, since the solid electrolyte formed on the metal in this way consists of fine crystals of TCNQ salt, a coagulating resin such as polyvinylpyrrolidone is actually added to the coating solution to increase the adhesion strength of the fine crystals. However, since the coagulating resin is an electrical insulator, the conductivity of the solid electrolyte is lowered (800 Ω cm
(25℃)). In method (2) above, there is a limit to the miniaturization of the TCNQ salt, and the adhesion strength to the above metal is particularly weak, so the solid electrolyte made of TCNQ salt may peel off from the above metal during the capacitor life test. , deterioration of characteristics, such as an increase in tanδ and a decrease in capacity, is observed. Although the reinforcement of the adhesion strength can be improved to some extent by employing the coagulating resin as described above, it also causes a decrease in the electrical conductivity of the solid electrolyte.
Furthermore, since a dispersion solution of microcrystals made of TCNQ salt is used, the impregnation rate is particularly poor for porous metals, and even if an ultrasonic diffusion impregnation method is used, the impregnation rate is at most the same as method (1) above. It is. The method (3) above has a problem in that the vacuum evaporation work is complicated. (c) Problems to be solved by the invention The present invention solves the problems of the prior art described above, namely
This solution solves the problems of poor adhesion workability of TCNQ salt, deterioration of conductivity of solid electrolyte due to alteration of TCNQ salt, low adhesion strength, and complexity of vacuum evaporation work. (d) Means for solving the problems The present invention provides a solid electrolytic capacitor having a winding element and using TCNQ salt as a solid electrolyte.
A container for melting and liquefying TCNQ salt at a temperature above the melting point and below 280°C also serves as a capacitor outer case. The present invention provides certain TCNQ salts, specifically:
N-(isopropyl)-quinolinium, N-(n-
propyl)-quinolinium, N-(n-propyl)
-Isoquinolinium, N-(isopropyl)-Although it takes a short time for the TCNQ salt of isoquinolinium to thermally decompose even when it is heated and melted, it provides sufficient time for the adhesion process; Maintains high conductivity when cooled and solidified
This is based on the completely new knowledge that a solid electrolyte made of TCNQ salt can be obtained. Furthermore, the present invention provides examples of N-(n-propyl)-isoquinolinium or N-(isopropyl)-isoquinolinium among the above TCNQ salts.
It is characterized by the selection of TCNQ salt. That is, N-(n-propyl)-isoquinolinium and N-(isopropyl)-isoquinolinium
The melting point of TCNQ salt is 210 to 220°C, but if it is liquefied and maintained at a temperature above the melting point and below about 280°C, and cooling is started before thermal decomposition, that is, within about 4 minutes after the completion of liquefaction, it will crystallize again. Forms a solid electrolyte with high conductivity of ~30Ωcm (25°C). At a temperature of about 280°C or higher, or at a temperature lower than that, for at least 1 minute, or at most 4 minutes,
If TCNQ salt is kept in a liquid state, it will smoke heavily and become a near-electrical insulator. The solid electrolyte obtained by the present invention can be obtained by the conventional method described above.
The solid electrolyte obtained by the present invention is not a collection of fine crystals of TCNQ salt as in cases (1) and (2), but is almost in an amorphous state.
For example, it maintains excellent repairability against oxide films on film-forming metal surfaces. According to the present invention, it is the same as attaching TCNQ salt to a film-forming metal using a solution containing 100% TCNQ salt. During the adhesion process, the required amount of solid electrolyte can be formed not only when the metal is in the form of a foil but also when it is porous, which not only improves mass productivity but also eliminates the conventional problem of TCNQ salt deteriorating each time it is dried. disadvantages are overcome. Furthermore, according to the present invention, since the solid electrolyte is close to an amorphous state, the adhesion force to the metal is sufficiently large, and therefore,
There is no need to use a coagulating resin as in the prior art, and an undesirable decrease in the electrical conductivity of the solid electrolyte can be avoided. Further, as in the present invention, an electrolytic capacitor using N-(n-propyl)-isoquinolinium or a TCNQ salt of N-(isopropyl)-isoquinolinium,
Higher capacitance values (i.e., impregnation rate) and higher (+85
The improvement effect is to further reduce the rate of change in capacitance at temperatures (°C). (e) Function Since the container is also used as a capacitor outer case, operations such as melting and liquefying the TCNQ salt, impregnating the winding element, cooling and solidifying the TCNQ salt, and sealing with resin can be performed efficiently and smoothly in this container. . (f) Example An example of the present invention will be described below. First, N-(n-propyl)-isoquinolinium
TCNQ salt is prepared. The preparation of such TCNQ salt itself is described in J.Am.Chem.Soc., Vol.84, P.3374-3387.
(1962), but briefly, N-(n-propyl)-isoquinolinium iodine obtained by reacting n-propyliodine with isoquinoline and TCNQ are reacted in acetonitrile. By reacting in an equimolar ratio, for example, a molar ratio of 1:1.3, powdered crystalline N-(n-propyl) is produced.
- TCNQ salt of isoquinolinium is made. Hereinafter, this salt will be simply referred to as TCNQ salt. On the other hand, as shown in Fig. 1, a porous capacitor as a film-forming metal having an oxide film is produced by anodizing a sintered body of aluminum powder according to the usual manufacturing method of an aluminum sintered solid electrolytic capacitor. Element 1 is created. After the above preparation, the step performed is to impregnate the capacitor element 1 with a solid electrolyte consisting of TCNQ salt. That is, as shown in FIG. 2, the prepared powder TCNQ salt is stored in an aluminum container 2 under moderate pressure, and the container 2 is heated to provide a TCNQ salt bath 3 in which the TCNQ salt is melted and liquefied. The temperature of this bath is maintained at 250°C to 260°C. Note that pressurizing the aluminum container 2 when storing TCNQ salt is not essential. In the following process, as shown in Figure 3, the temperature is set at 250℃ in advance.
Capacitor element 1 heated and maintained at ~260℃
is immersed in the TCNQ salt bath 3, and the entire container 2 is immediately cooled naturally to room temperature. As a result, the TCNQ salt impregnated into the porous capacitor element 1 is cooled and solidified.
It becomes the desired solid electrolyte. The time required from the liquefaction of the TCNQ salt to the start of cooling is about 5 seconds. The time required from the start of cooling until the temperature drops below the melting point is within several seconds (for example, 4 seconds). In the remaining steps, the container 2 is peeled off from the capacitor element 1 impregnated with the solid electrolyte, and then a graphite layer 4 and a silver layer are deposited on the surface of the impregnated capacitor element 1', as shown in FIG. Paint layers 5 are sequentially applied, and finally the element 1 is housed together with the cathode lead wire 6 in an aluminum container 7 and fixed with solder 8 and epoxy resin 9. As the element 1, a conventional capacitor having a capacitance of 1 μF using manganese dioxide as a solid electrolyte was used, and the capacitance of the completed capacitor was approximately 1 μF. This means an impregnation rate comparable to that of manganese dioxide, which is 100%. Tables 1 and 2 show the temperature characteristics and high temperature load characteristics of the capacitor of this example. Similarly, as a reference example for comparison, only the solid electrolyte of the above example was replaced with N-(n-propyl)-quinolinium.
The characteristics of the capacitor obtained by changing to TCNQ salt are also shown. Note that the TCNQ salt of N-(n-propyl)-quinolinium is prepared in the same manner.
The liquefaction holding temperature is 260 to 270°C, and the time from liquefaction to cooling is about 10 seconds.

【table】

[Table] From the table above, in the case of the reference example, the capacitance value is approximately
Since it is 0.8 μF (20° C.), the impregnation rate is 80%, assuming that the impregnation rate with manganese dioxide is 100%, and it can be seen that the impregnation rate (100%) of this example is excellent.
Also, in terms of temperature characteristics, the superiority of this example is clear on the high temperature side. The present invention provides a powder sintered element 1 as shown in the above embodiment.
Instead of using etched aluminum foil as a cathode, the same chemically formed foil as an anode, and a winding element in which these are wound with separator paper sandwiched therebetween can be effectively applied. That is, the prepared powdered TCNQ salt is stored in an aluminum container, the container is heated, and the TCNQ salt is heated.
Salt is melted and liquefied at a temperature above the melting point and below 280℃.
A TCNQ salt bath is provided. Next, preheat to 250℃~260℃
The winding element heated and maintained at °C is immersed in a TCNQ salt bath, and the entire container is immediately allowed to cool naturally at room temperature. By subsequently sealing with resin, an electrolytic capacitor having almost the same temperature characteristics and high-temperature load characteristics as the powder sintered type can be produced. In this case, it is necessary to chemically convert the cut portion of the chemically formed foil, the anode lead, etc. before impregnation, but the container 2 can be used as it is as a capacitor outer case, and graphite layer or silver paint layer is no longer necessary. The above winding element (conventional dry electrolytic capacitor)
TCNQ (equivalent to that used for 50V, 2.2μF)
The characteristics of the completed capacitor impregnated with salt are
1.45μF, tanδ1.8%, LC/30″0.04μA (25V applied)
It is. In the above embodiment, the metal of element 1 was aluminum, but other film-forming metals such as tantalum or niobium may be used. Furthermore, as a solid electrolyte,
N-(isopropyl)-isoquinolinium
A capacitor can be manufactured using TCNQ salt in the same manner as in the example. (G) Effects of the Invention As is clear from the above explanation, according to the present invention, in a solid electrolytic capacitor using a solid electrolyte made of an organic semiconductor, the solid electrolyte can be attached to the film-forming metal with a simple operation. , and the solid electrolyte undergoes little deterioration during such work, and furthermore, a sufficiently practical capacitor having a large capacitance value and excellent temperature characteristics can be obtained. Moreover, since the container is also used as a capacitor outer case, each process can be carried out efficiently and smoothly.

[Brief explanation of the drawing]

Figures 1 to 4 are step-by-step diagrams illustrating one embodiment of the present invention. Figure 1 is a side view of a capacitor element, Figure 2 is a sectional view showing a TCNQ salt bath, and Figure 3 is a TCNQ salt bath. A cross-sectional view showing a capacitor element immersed in a bath, and FIG. 4 is a cross-sectional view of a completed capacitor element. 1...Capacitor element, 3...TCNQ salt bath.

Claims (1)

[Claims] 1. A solid electrolytic capacitor having a winding element and using TCNQ salt as a solid electrolyte, characterized in that a container for melting and liquefying the TCNQ salt at a temperature above the melting point and below 280°C also serves as the capacitor outer case. Electrolytic capacitor.