JPH0477451B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a solid electrolytic capacitor. (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 tetracyanoquinodimethane. However, TCNQ salt is usually a powdered crystal, and although the crystal itself exhibits high electrical conductivity and good repairability of the above-mentioned film, it is difficult to process because it is a powdered crystal. 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 is always at risk of deterioration due to alteration during the deposition 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 fine crystals of TCNQ salt are made using a ball mill or the like and 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 adhere 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 achieved by applying 5 to 10 times and drying is at most 30%, assuming the impregnation rate when manganese dioxide is used as the solid electrolyte as 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 that is 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 electrical conductivity of the solid electrolyte is lowered (800 Ω) due to the deterioration of the electrical conductivity described above.
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. In the method (3) above, not only is the vacuum evaporation work complicated, but it is also completely unsuitable for adhesion to porous metals. (c) Problems to be Solved by the Invention The present invention provides a completely new solid electrolytic capacitor, more specifically, when a solid electrolyte made of TCNQ salt is attached to a film-forming metal having an anodized film, TCNQ Creates a liquid consisting only of salt,
The object of the present invention is to provide a solid electrolytic capacitor in which the metal is brought into contact with such a liquid, and then the liquid is cooled and solidified, thereby solving the above problems. The most practical way to obtain a liquid consisting only of TCNQ salt is to liquefy the powdered TCNQ salt in its original form by heating and melting it. However, simply heating and melting the TCNQ salt thermally decomposes the TCNQ salt and turns it into almost an electrical insulator, completely eliminating the function of a solid electrolyte for a capacitor. The present invention provides certain TCNQ salts, specifically:
N-(isopropyl)-quinolinium and 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. It goes without saying that the TCNQ salt used as the electrolyte in the solid electrolytic capacitor of the present invention has a high conductivity that can be used as an electrolyte for a capacitor after being cooled and solidified. (d) Means for Solving the Problems The solid electrolytic capacitor of the present invention is manufactured as follows. That is, (A) store TCNQ salt in a container, melt and liquefy the TCNQ salt by heating the container, and (B) maintain the TCNQ salt at a temperature above the melting point and below 280°C to create a TCNQ salt bath. (C) immersing a capacitor element formed by forming an anodized film on a film-forming metal in the TCNQ salt bath to impregnate the capacitor element with the TCNQ salt; and (D) cooling the container. It is manufactured by cooling and solidifying the TCNQ salt impregnated into the capacitor element, and performing the steps of liquefying and cooling and solidifying the TCNQ salt within 4 minutes (within the time required for thermal decomposition). Furthermore, the present invention provides N-(n
-propyl)-isoquinonium or N-(isopropyl)-isoquinonium has selected TCNQ salt. (e) Effects of 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℃ or higher, or at a temperature lower than that for about 1 minute or more, and at most 4 minutes or more,
If TCNQ salt is kept in a liquid state, it will smoke heavily and become a near-electrical insulator. The solid electrolyte used in the solid electrolytic capacitor of the present invention is TCNQ as in the case of the above conventional methods (1) and (2).
It is not a collection of fine salt crystals, but is almost in an amorphous state. The solid electrolyte used in the capacitor of the present invention also maintains the inherent properties of the TCNQ salt, such as its excellent ability to repair oxide films on film-forming metal surfaces. In the solid electrolytic capacitor of the present invention, a solution containing 100% TCNQ salt is used to coat film-forming metals.
This is the same thing that causes TCNQ salt to adhere.
Completely different from the conventional method (1) above, it is possible to form the required amount of solid electrolyte in almost one deposition operation, not only when the metal is in the form of foil but also when it is porous, improving mass productivity. Not only when drying, but also when drying.
Previous drawbacks such as degradation of TCNQ salts are overcome. Furthermore, in the solid electrolytic capacitor of the present invention, since the solid electrolyte is close to an amorphous state, the adhesion force to the metal is sufficiently large, so there is no need to use a conventional coagulating resin, and the solid electrolyte Undesirable reduction in conductivity can be avoided. Furthermore, like the solid electrolytic capacitor of the present invention, N-
Electrolytic capacitors using TCNQ salts of (n-propyl)-isoquinolinium or N-(isopropyl)-isoquinolinium can be manufactured using other TCNQ salts, namely N
-(isopropyl)-quinolinium or N-(n-
The improvement effect of quinolinium (propyl)-quinolinium is to make the capacitance value (i.e. impregnation rate) larger and to make the rate of capacitance change smaller at high temperature (+85°C) compared to when TCNQ salt is used. shows. (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 simply stated, it is obtained by reacting n-propyliodine and isoquinoline. N-(n-propyl)-isoquinolinium iodine and TCNQ in approximately equimolar ratio in acetonitrile,
For example, the TCNQ salt of N-(n-propyl)-isoquinolinium in powdered crystal form is prepared by reacting at a molar ratio of 1:1.3. From now on, simply add this salt.
It is called 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 to be carried out is to impregnate the capacitor element 1 with a solid electrolyte consisting of TCNQ salt. That is, prepared powder TCNQ salt is stored in an aluminum container 2 as shown in FIG. 2, and a TCNQ salt bath 3 is provided in which the container 2 is heated to melt and liquefy. The temperature of this bath is maintained at 250°C to 260°C. Note that the amount of solid electrolyte to be impregnated is determined depending on the capacitor element. Therefore, the volume of the aluminum container 2 is equivalent to the amount of powder to be impregnated.
If less than the total volume of TCNQ salt, TCNQ
Salt is appropriately pressurized and stored in an aluminum container 2. 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 at room temperature. As a result, the TCNQ salt impregnated into the porous capacitor element 1 is cooled and solidified to become the desired solid electrolyte. The time required from liquefaction to cooling solidification of the TCNQ salt is approximately 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. In addition, in the same table, 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°C 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, by impregnating a wound element with a solid electrolyte made of TCNQ salt and sealing it with resin in the same manner as in the above embodiment, an electrolytic capacitor having almost the same temperature characteristics and high-temperature load characteristics as the powder sintered type can be created. I can do it. 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)
- The case of using TCNQ salt of isoquinolinium will be explained below. First, N-(isopropyl)-isoquinolinium
As mentioned above, TCNQ salt was prepared by J.Am.Chem.Soc.
Created based on the description in Vol. 84, P. 3374-3387 (1962). Briefly, N-(isopropyl)-isoquinolinium iodine obtained by reacting isopropyliodine with isoquinoline and TCNQ are mixed in acetonitrile in an approximately equimolar ratio, e.g. 1:
By reacting at a molar ratio of 1.3, powdered crystalline N-(isopropyl)-isoquinolinium was prepared.
TCNQ salt is made. This TCNQ salt is impregnated into a powder sintered capacitor element in the same process as above, and after cooling and solidifying to obtain a solid electrolyte, the capacitance is
A 2.2μF solid electrolytic capacitor is completed. The temperature characteristics and high temperature load characteristics of this capacitor were good as shown in Tables 3 and 4 below.

【table】

[Table] (G) Effects of the Invention As is clear from the above description, the solid electrolytic capacitor of the present invention is a solid electrolytic capacitor using a solid electrolyte made of an organic semiconductor, and the solid electrolyte has no adhesion to the film-forming metal. can be carried out with simple operations, the solid electrolyte undergoes little deterioration during such operations, and furthermore, a sufficiently practical capacitor having a large capacitance value and excellent temperature characteristics can be obtained. Furthermore, in the solid electrolytic capacitor of the present invention, the container containing the TCNQ salt is heated to melt and liquefy the TCNQ salt, and the capacitor element is impregnated with this molten liquid. Since the container used (i.e., the same container used for heating) is cooled to solidify the TCNQ salt, the following major effects can be obtained. (a) For example, when only a capacitor element impregnated with TCNQ salt solution is lifted out of the TCNQ salt bath into the air and cooled and solidified, the TCNQ salt solution impregnated into the capacitor element will solidify while dripping downward. , a drip-like protrusion of TCNQ salt is formed on the lower outer periphery and bottom of the capacitor element, and in order to house this element in the case, a larger exterior case is required compared to the present invention, which reduces the size of the components. This is inconvenient. Also, for miniaturization
Although there is a drawback that an extra step is required to remove the drooping protrusion of the TCNQ salt, such an extra step is not required in the case of the present invention. (b) Once the size of the capacitor element is determined, the amount of TCNQ salt required can be determined in advance, and by storing that amount in a container, the TCNQ salt can be used without wasting it. Another explanation is that the melting temperature and thermal decomposition temperature range of TCNQ salt is narrow, and the time to thermal decomposition is extremely short, so TCNQ salt is placed in a large TCNQ salt bath.
If the salt is melted, only the capacitor element
When immersed in a TCNQ salt bath and taken up into the air to cool and solidify, the TCNQ salt left in the container changes in quality and can no longer be used as an electrolyte, resulting in a waste of expensive TCNQ salt. However, this is not the case with the present invention. (c) In the case of the configuration of the present invention, after the container is cooled and solidified, it can also be used as it is as an exterior case for a condenser. (d) Compared to the case where only the capacitor element impregnated with the TCNQ salt solution is lifted from the TCNQ salt bath into the air and cooled, it is better to directly cool the container as in the present invention so that the TCNQ salt in the container and the refrigerant come into contact with each other. Since it is easy to avoid this, it is possible to use refrigerants other than gas, resulting in good cooling efficiency. (e) When only the capacitor element impregnated with the TCNQ salt solution is lifted from the TCNQ salt bath into the air and cooled and solidified, the TCNQ salt solution that has been impregnated into the capacitor element drips downward, and a strict comparison shows that the effect of impregnation is However, in the present invention, the TCNQ salt is cooled and solidified while the capacitor element is immersed in the molten TCNQ salt, so the TCNQ salt solidifies while the capacitor element is completely impregnated, and the impregnation is reduced. is complete. (f) Only capacitor elements impregnated with TCNQ salt.
When the TCNQ salt is lifted into the air and cooled and solidified, there is a risk that impurities such as dust and water vapor in the air may adhere to the capacitor element.
There is no such risk when the material is cooled and solidified in a container as in the present invention.

[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)

[Scope of Claims] 1. A capacitor element wound with a separator paper sandwiched between a cathode foil and an anode foil, and a TCNQ salt that is meltable and has a conductivity that can be used as an electrolyte for a capacitor after being cooled and solidified. A solid electrolytic capacitor comprising: a solid electrolyte which is melted and impregnated with a solid electrolyte, and then cooled and solidified. 2. A capacitor element wound with separator paper sandwiched between cathode foil and anode foil, a container for storing TCNQ salt and heating and melting it, and a conductivity that is meltable and can be used as an electrolyte for a capacitor after cooling and solidifying. and a solid electrolyte obtained by melting and impregnating the capacitor element with a TCNQ salt having the following properties and cooling and solidifying the solid electrolyte, the container being used as an outer container for the capacitor element.