JPH0377649B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to solid electrolytic capacitors. A solid electrolytic capacitor has a structure in which a solid electrolyte is attached to a metal such as aluminum having an anodized film. In this type of capacitor, which has been mass-produced for a long time, the solid electrolyte that makes up the capacitor is mostly manganese dioxide, but in recent years, the weak point of manganese dioxide has been discovered. Organic semiconductors, mainly organic semiconductors, are used as solid electrolytes to improve damage to the anodic oxide 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. In other words, metals with valve action
The problem is how to attach TCNQ salt crystals. In particular, valve-acting 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. In view of the above points, the present inventors have already proposed a completely new solid electrolytic capacitor using TCNQ salt. Its structure is explained in detail in Japanese Patent Application No. 58816/1982, but in summary, it is characterized by comprising a capacitor element and a solid electrolyte consisting of TCNQ salt impregnated into the element in a liquefied state. There is. According to this new solid electrolytic capacitor,
The impregnation rate of TCNQ salt into the capacitor element increases,
Moreover, it is possible to take advantage of the original excellent properties of TCNQ salt, and improve capacitor characteristics. In conventional general solid electrolytic capacitors, a powdered valve metal is sintered and subjected to chemical conversion treatment to form a capacitor element, and the element is impregnated with a solid electrolyte. FIG. 1 shows a typical conventional solid electrolytic capacitor, in which 1 is a porous capacitor element made by sintering aluminum powder into a cylindrical shape and undergoing chemical conversion treatment;
2 is a solid electrolyte made of manganese dioxide impregnated into the element; 3 and 4 are a graphite layer and a silver paint layer which are successively deposited on the outer periphery of the solid electrolyte 2; 5
6 is an aluminum case, 6 is solder filled in the bottom of the case 5, 7 is a resin for sealing the case opening, and 8 and 9 are an anode lead and a cathode lead electrically connected to the element 1 and the solder 6, respectively. The present invention aims to simplify the structure of the conventional capacitor by utilizing the above-described novel technique of impregnating a capacitor element with TCNQ salt in a liquefied state. That is, according to the present invention, as shown in FIG.
The graphite layer 3, silver paint layer 4 and solder 6, which were conventionally necessary, are no longer necessary. Furthermore, the present invention
This is an attempt to solve the undesirable decrease in capacitance that occurs when realizing such a simple structure. The structural features of the solid electrolytic capacitor of the present invention are as follows:
A porous capacitor element made by sintering a powdered metal with a valve action and subjected to chemical conversion treatment; a case made of a metal without a valve action and accommodating the capacitor element; After being heated and melted to impregnate the capacitor element, the solid electrolyte is cooled and solidified to provide a solid electrolyte made of TCNQ salt filled inside the capacitor element and between the element and the inner surface of the case. As described above, according to the present invention, only the solid electrolyte is present between the capacitor element and the metal case, so the structure is extremely simple. In this case, it is important that the material of the metal case is selected to have no valve action. If the metal case is made of aluminum according to the prior art, an undesirable reduction in capacitance is observed due to the valve action of aluminum. That is, in the configuration according to the present invention, the cathode lead is attached to the metal case, but if the case has a valve action, additional static will be generated on the inside of the case due to the coating formed on the inner surface of the case due to natural oxidation. A capacitance is formed.
This additional capacitance is in a series relationship with the original capacitance formed in the capacitor element, and since it is not sufficiently large compared to the original capacitance, it can be expressed as a series combination of both capacitances. This results in a decrease in the capacitance of the capacitor itself. When the case is made of a metal without valve action as in the present invention, the case and the solid electrolyte are almost short-circuited through a small resistance, and the effect of the additional capacitance is not a substantial problem. The above-mentioned minute resistance includes contact resistance on the inner surface of the case and the like. The metal without valve action for the case used in the present invention can withstand the temperature at which TCNQ salt is liquefied (approximately 300° C. or less). That is, the melting point is 300
℃ or higher, specifically, gold, platinum, silver, copper, iron, nickel, zinc, alloys thereof such as brass, bronze, stainless steel, or metals coated with these metals. Preferably, copper and brass are used because they are resistant to oxidation, have good rollability, and are inexpensive. As the metal for the capacitor element used in the present invention, common metals exhibiting valve action, such as aluminum, tantalum, and niobium, are used. TCNQ and its various salts, as well as its production process, are described in, for example, J. Am. Chem. Soc., Vol. 84,
P3374-3387 (1962). TCNQ
Salts include a single salt represented by M ⁿ⁺ (TCNQ ^- )n and a complex salt represented by M ⁿ⁺ (TCNQ ^- )n (TCNQ)m. In addition, the above M is an organic cation, n is the value of the cation, and m is the neutrality contained in 1 mol of the complex salt.
Each term means a positive number corresponding to the number of moles of TCNQ. In the present invention, however, the use of complex salts is more preferred for capacitor properties. The above m of the complex salt is preferably 0.5 to 1.5, more preferably about 1. Examples of TCNQ salts used in the present invention include:
Quinoline and isoquinoline substituted at N-position
TCNQ salt is mentioned. In addition, the substituent at the N position is
_C2 - _C18 (2-18 carbon atoms) alkyl (e.g. ethyl, propyl, butyl, pentyl, octyl, decyl, octadecyl), _C5 - _C8 cycloalkyl (e.g. cyclopentyl, cyclohexyl), _C3
~ _C18 alkene (e.g. allyl), phenyl or phenyl( _C1 - _C18 )alkyl (e.g. phenethyl)
It is a hydrocarbon group such as. More preferred examples of the TCNQ salt used in the present invention include TCNQ salt of N-n-propylquinoline,
TCNQ salt of N-ethylisoquinoline, TCNQ salt of N-isopropylquinoline, TCNQ salt of N-hexylquinoline, TCNQ salt of N-n-propylisoquinoline, TCNQ salt of N-isopropylisoquinoline, N-n-butylisoquinoline of TCNQ salt. Even if these TCNQ salts are heated and melted to liquefy, it takes a short time to thermally decompose.
It is possible to obtain a solid electrolyte made of TCNQ salt that provides sufficient time for impregnation and adhesion to capacitor elements, and that maintains high conductivity if the above-mentioned work is not performed within such time and is cooled and solidified. I can do it. Examples of the electrical conductivity of TCNQ salt obtained by cooling and solidifying before decomposition and the time required to insulate after complete melting are shown in the table below.

[Table] P1: N-n-propylquinoline ⁺ (TCNQ ^- )
(TCNQ) P2: N-isopropylquinoline ⁺ (TCNQ ^- )
(TCNQ) P3: N-n-propylisoquinoline ⁺
(TCNQ ^- ) (TCNQ) P4: N-isopropylisoquinoline ⁺
(TCNQ ^- ) (TCNQ) P5: N-n-butylisoquinoline ⁺ (TCNQ ^- )
(TCNQ) The production of each of the above salts is, for example, as follows. N-
Alkyl iodo and quinoline (or isoquinoline)
A TCNQ salt is prepared by reacting N-alkylquinoline (or isoquinoline) iodide obtained by reacting with TCNQ in a suitable solvent (for example, acetonitrile) at a suitable molar ratio (for example, 3:4). Since this salt contains many impurities, the purity of the salt can be increased by repeating a recrystallization operation consisting of heating dissolution, cooling, and crystallization in an appropriate solvent (for example, acetonitrile at a temperature of 82° C. or lower). The resulting crystals are needle-shaped or rod-shaped powders. Examples of the present invention will be described below. FIG. 2 shows the structure of the solid electrolytic capacitor of this embodiment, where 10 is a porous capacitor element made by sintering aluminum powder into a cylindrical shape and subjected to chemical conversion treatment, and 11 is a part of the element. 12 is a solderable anode lead wire such as a CP wire that is welded to the aluminum wire, and 13 is a case made of copper or brass, in which the capacitor element 10 is housed. , 14
15 is a solid electrolyte made of TCNQ salt that is filled inside the capacitor element 10 and between the element and the inner surface of the case 13; 15 is a resin that seals the opening of the case 13; and 16 is a solid electrolyte that is welded to the outer periphery of the case 13. The cathode lead wire is made of CP wire. The method for filling the above TCNQ salt is as follows. Powdered TCNQ salt prepared by the method described above (in this example, the above P5 salt was used) was used in Case 1.
3 and place the case on a metal plate heated to approximately 290°C.
Melt and liquefy TCNQ salt. As a subsequent step, immediately after the melting and liquefaction, the preheated capacitor element 10, which has the aluminum wire 11 and the anode lead wire 12, is inserted into the liquefied TCNQ salt in the case 13, and then the case 13 is heated. immersed in water and cooled rapidly. This solidifies the TCNQ salt impregnated inside the capacitor element 10, and the TCNQ salt forms a solid electrolyte exhibiting high conductivity. At the same time, the solid electrolyte fills the space between the element 10 and the inner surface of the case 13. The table below shows the characteristics of each solid electrolytic capacitor of this example and a reference example for comparison. The reference example differs in that the case 13 is made of aluminum, and all other configurations are the same as the example. or,
In both Examples and Reference Examples, the capacitor elements used were conventional solid electrolytic capacitors using manganese dioxide as a solid electrolyte and exhibiting a capacitance of 1.0 μF.

[Table] In the table, cap and tanδ are the capacitance at 120Hz, respectively.
Loss, LC means the leakage current 30 seconds after applying the rated voltage (10V), and ESR means the equivalent series resistance at 100KHz. As is clear from the above description, according to the present invention, in a solid electrolytic capacitor in which a solid electrolyte is impregnated into a capacitor element made by sintering a powdered valve metal and subjected to a chemical conversion treatment, the capacitor element and the case are bonded together. The structure is extremely simple because the solid electrolyte made of TCNQ salt is filled between the capacitor element and the capacitor element and the inside of the case. Since these steps can be carried out simultaneously, the number of steps can be reduced, and furthermore, an undesirable decrease in capacitance does not occur even though the case and the solid electrolyte are in contact with each other.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional example, and FIG. 2 is a sectional view showing an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. A porous capacitor element obtained by sintering and chemically treating a powdered metal with a valve action, a case made of a metal without a valve action and accommodating the capacitor element, and the case. a solid electrolyte made of TCNQ salt that is sealed in the capacitor element and heated and melted to impregnate the capacitor element, and then cooled and solidified to fill the inside of the capacitor element and between the element and the inner surface of the case. solid electrolytic capacitor. 2 In claim 1, the above-mentioned
A solid electrolytic capacitor characterized in that TCNQ salt takes a substantial amount of time to thermally decompose in a liquefied state. 3 In claim 1 or 2,
A solid electrolytic capacitor characterized in that the metal constituting the case is copper or brass.