JPS60171717A - Solid electrolytic condenser and method of producing same - 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 The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and more particularly to an improvement in a solid electrolyte layer made of an organic semiconductor and a method for forming the same.

Solid electrolytic capacitors use a film-forming metal such as aluminum or tanker for the anode, and in order to expand the anode, it is made porous by etching or sintering, and an oxide film layer that becomes a dielectric is formed on the surface. A solid electrolyte layer is formed on the surface of the solid electrolyte layer, and a conductive cathode extraction layer is further formed on the outside of the solid electrolyte layer.

Conventionally, manganese dioxide has been used as this solid electrolyte layer. The method for forming this manganese dioxide on the dielectric oxide film layer is to impregnate the anode electrode in liquid manganese nitrate and then thermally decompose the manganese nitrate at a temperature of around 300°C to denature it into manganese dioxide. Ta.

However, according to this method, only a small amount of manganese dioxide is deposited in one process, so it is necessary to repeat the same process several to several times.

Therefore, the manufacturing process becomes extremely complicated, and the dielectric oxide film deteriorates due to the high temperature and gas generated during thermal decomposition.

Therefore, recently, it has been proposed to use a conductive organic substance in the electrolyte layer instead of manganese dioxide.

As this organic electrolyte, various complex salts of tetracyanoquinodimethane (hereinafter referred to as TCNQ) are known.

Since TCNQ complex salt is a solid substance at room temperature, a conventional method of attaching it to a capacitor element using it as an electrolyte is to impregnate the anode body in a solution of TCNQ complex salt dissolved in an organic solvent. , then pulled out of the solution, dispersed the organic solvent, and deposited TCN on the surface of the anode body.
The entire Q complex salt layer is made into a salt layer. However, in this method, since the concentration of TCNQ complex salt in the solvent is low, it is not possible to deposit sufficient T'CNQ complex salt in one impregnation, and this step is repeated several times as in the formation of the manganese dioxide layer. It is necessary to repeat the process more than ten times, which also complicates the manufacturing process. Furthermore, since the TCNQ complex salt crystallizes after the solvent evaporates, sufficient contact with the dielectric oxide film on the surface of the anode body cannot be obtained, resulting in the drawback that a predetermined capacitance cannot be obtained.

Recently, a method has been proposed in which only the TCNQ complex salt is heated above its melting point to liquefy, an anode body is impregnated therein, and then the liquefied TCNQ complex salt is pulled up and cooled to adhere the TCNQ complex salt. According to this method, since highly concentrated TCNQCN is deposited on the anode body, sufficient TCN can be obtained in one impregnation process.
A Q complex salt can be attached. However, TCNQ complex salts are sensitive to heat, and many TCNQ complex salts decompose when heated before reaching their melting point, making it virtually impossible to use this method. for example,
An example of this is a complex salt of methylisoquinolinium and TCNQ, which if heated above 200°C will emit smoke and decompose before melting, becoming an insulator.

This invention improves on these drawbacks, and aims to make it possible to heat-melt and impregnate TCNQ complex salts, which were conventionally impossible to heat-melt and impregnate, and also to obtain a solid electrolytic capacitor with excellent characteristics. There is.

This invention provides methylisoquinolinium TCNQ complex salt,
A mixture obtained by adding a lactone compound is added to the TCN
It is characterized by heating to a temperature lower than the melting point or decomposition temperature of the Q complex salt to liquefy it, impregnating the capacitor element in this liquid mixture, and cooling and solidifying it after impregnation.The mixture has a lower melting point than the pure substance. Focusing on the phenomenon that the freezing point (freezing point) falls, a mixture of TCNQ complex salt and additives is heated and melted to impregnate the anode body.

The present invention will be explained in detail based on the following examples.

First, the manufacturing procedure of the solid electrolytic capacitor according to the present invention will be explained.

FIG. 1 shows the capacitor element used in this example.

This capacitor element 1 is formed by winding a band-shaped electrode body, and the anode 2 is made of high-purity aluminum foil. A dielectric oxide film is formed on the surface of this anode 2 by anodizing treatment.

This strip-shaped anode 2 has collector electrodes 3 of approximately the same size disposed opposite each other, and a separator paper 4 slightly wider than these electrodes 2.3 is placed between the anode 2 and the collector electrode 3. The sandwiched material is wound from one end to form a cylindrical capacitor element 1. Note that tabs 5 and 6 for obtaining electrical connection with the outside are connected to each of the anode 2 and the collector electrode 3 by means such as welding, and protrude in parallel from one end surface. Furthermore, external leads 7.8 are connected to the tips of these tabs by welding.

FIG. 2 shows a method of impregnating the capacitor element 1 with a solid electrolyte layer, and a preheating block 10 is placed on the left side of the figure. This preheating block 10 has a heating heater embedded inside and a recess 11 on the top surface.
is provided, and the capacitor element 1 is placed in the recess 11, and the capacitor element 1 is heated in advance to maintain a high temperature state.

Next, an impregnating block 12 is placed on the right side of the figure, and this impregnating block 12 also has a heating heater embedded therein and a recess 13 formed in its upper surface. Then, a powder mixture 14 consisting of TCNQtft salt and additives is injected into the recess 13, and the mixture 14 is melted by heating.

The capacitor element 1, which has been kept on standby in the preheating block 10, is moved here and impregnated for a predetermined period of time, and then the capacitor element 1 is pulled up from the recess 13, and the liquid mixture 14 is solidified by natural cooling to form a solid electrolyte layer. form.

As shown in FIG. 3, the capacitor element 1 with the solid electrolyte layer formed thereon is housed in a cylindrical outer case 20 with a bottom, and the open end of the outer case 20 is sealed with an elastic sealing member 21. Then, the open end of the outer case 20 is rolled up and sealed. Note that the external leads 7.8 drawn out from the capacitor element 1 protrude to the outside from the through hole provided in the elastic sealing body 21, so that an electrical connection between the capacitor element 1 and the outside can be established.

Next, we will present the results of fabricating an actual solid electrolytic capacitor using the procedure described above and measuring its characteristics.

Conventional examples include a normal dry electrolytic capacitor using a liquid electrolyte, a solid electrolytic capacitor made using inpropyl-inquinolinium TCNQ complex salt that can be melted and impregnated with only TCNQ complex salt, and a solid electrolytic capacitor made using methylisoquinolinium TCNQ complex salt. A mixture obtained by heating and melting only the nium TCNQ complex salt,
A conventional example will be shown in comparison with the present invention.

First, the capacitor element used was 2.2 mm wide and 10 mm long.
mm, thickness 80μm high purity aluminum (purity 99.
99%) was prepared as an anode, the surface of this anode was expanded by electrolytic etching using alternating current, and then a dielectric oxide film having a withstand voltage of 9 V was formed on the surface by anodizing treatment. As a current collecting electrode, aluminum (purity 99.94%) of the same size as the anode is arranged oppositely, and an aluminum tab for external extraction is connected to the approximate center of both electrodes by cold welding. It is wound into a cylindrical shape with a fiber-mixed separator paper interposed therebetween.

Next, for Conventional Example 1, this capacitor element was impregnated with an ethylene glycol-ammonium adipate based electrolyte. Regarding Conventional Example 2.3 and Examples 7 to 7 of the present invention, the capacitor element was heated to 190°C in a preheating block using the impregnation apparatus shown in FIG. , TCNQ complex salt or a mixture of it and an additive was injected, heated and melted, and the capacitor element was immersed in this for 10 seconds, and then taken out from the melting tank and allowed to cool naturally to impregnate the solid electrolyte.

Then, the impregnated capacitor element is housed in an aluminum exterior case, the opening is closed with a rubber sealing body, and the opening end of the exterior case is wrapped tightly to seal the rated voltage of 6.3V. We have completed an electrolytic capacitor with a rated capacity of 10μF. At this time, the external dimensions of the capacitor body are:
It had a diameter of 3 mm and a length of 5 mm.

Among these capacitors, the conventional example 1 has 15
For capacitors using a solid electrolyte, aging was performed by applying the rated voltage to each capacitor for 1 hour, and then the electrical characteristics were examined.

The electrical characteristics are the capacitance M (μF), the tangent of the loss angle at 120 Hz, and the equal series resistance value at 100 KHz (
ESR), (Ω), and leakage current value (μA/2 minute value) were measured, and the results shown in the following table were obtained.

(Left space on this page) Shows the cold 7I [I volume ratio] of lactone-based compounds.

Looking at the results of these examples, when conventionally heated and melted,
Methylisoquinolinium TCNQ complex salt, which could not be used as a solid electrolyte due to thermal decomposition before melting, can be liquefied at a temperature that does not cause decomposition by adding and heating a lactone compound, making it possible to impregnate capacitor elements. I understand.

As described above, even if an attempt is made to heat and melt the methylisoquinolinium TCNQ complex salt, it will undergo thermal decomposition before melting. For this reason, T
It cannot be used in a method in which only the CNQ complex salt is heated and melted to impregnate it.

Incidentally, when only the methylisoquinolinium TCNQ complex salt is heated, it is observed that it gradually thermally decomposes while emitting smoke from around 200°C.

However, as can be seen from the examples, the types of additives,
Although there are differences depending on the mixing ratio, it can be seen that in all cases of the present invention examples in which a lactone-based compound is added, it melts and liquefies at a temperature of 190° C. or lower, making it possible to impregnate capacitor elements.

Also, when comparing the characteristics of solid electrolytic capacitors after impregnation,
In the conventional dry electrolytic capacitor using a liquid electrolyte shown in Conventional Example 1, the electrolyte is held in a liquid state inside the solid electrolytic capacitor element, so fine etching holes are formed by etching to enlarge the anode. The electrolyte penetrates into the inside of the pinto (pinto) and makes sufficient contact with the dielectric oxide film, resulting in a high capacitance value. However, the specific resistance of the electrolyte is as high as 200-300Ω・ω, whereas the specific resistance of the TCNQ complex salt is about several tens of Ω・cII+, resulting in product loss or high equal series resistance. ing.

Furthermore, in the solid electrolytic capacitor manufactured by heating and melting only the isopropyl-isoquinolinium TCNQ complex salt and impregnating it into the capacitor element, as shown in Conventional Example 2, the loss and the equal series resistance value are lower than that of the TCNQ complex salt as described above. Since the specific resistance value is lower than that of the electrolytic solution, excellent characteristics are obtained, but sufficient capacitance is not obtained.

The reason for this is not clear, but although the molten isopropyl-isoquinolinium 'pCNQ complex penetrates into the etching bit of the anode, during subsequent cooling and solidification, the isopropyl-isoquinolinium TC
This is thought to be because the NQ complex crystallizes into needle-like crystals and only partially contacts the dielectric oxide film within the etching focus.

On the other hand, all of the solid electrolytic capacitors manufactured by the method of the present invention exhibit larger capacitance values than Conventional Example 2. This means that the solid electrolyte of this invention is TCN
Since it is a mixture of lactone compounds on QCN, crystallization is prevented during cooling after melting and impregnation, and it remains in the etching pin in an amorphous state, so it maintains sufficient contact with the dielectric oxide film. This is thought to be due to the Also, some T.
Even when crystallized on CNQCN, it is thought that the intercrystalline conductivity is obtained due to the presence of the lactone compound between the crystals, and the capacitance is ensured.

Note that in this example, foil-shaped aluminum was used for the anode,
After enlarging the surface, a dielectric oxide film was formed on the surface, and a current collecting electrode was wound around the capacitor element with separator paper interposed between the capacitor elements. Without limitation, the metal constituting the anode may be other film-forming metals such as tantalum, or alloys thereof. Further, the structure is not limited to such a wound structure, but may be a porous body made by sintering film-forming metal powder. Moreover, even if it is a wound structure, a separator paper may be omitted, a metal other than aluminum may be used for the collector electrode, a heat-resistant conductive resin film, etc. may be used.

In addition, regarding the exterior structure, in this example, the case is housed in a metal exterior case, but the exterior body may be a resin case, a resin dipped or molded one, a laminated film exterior, etc. Even if there is, it does not deviate from this invention.

Furthermore, the lactone compound to be added may be a lactone compound other than those exemplified in this example. Furthermore, in the examples, only one type of additive was used, but the same effect can be expected even if two or more types of lactone compounds are mixed and added.

As described above, according to the present invention, it is possible to impregnate a capacitor element by heating and melting methylisoquinolinium TCNQ complex salt, which was previously impossible.

Further, according to the present invention, the impregnation rate of TGNQ complex salt can be improved and the capacitance value per unit volume can be increased, which contributes to miniaturization of solid electrolytic capacitors.

Furthermore, since it becomes liquid at a temperature lower than the decomposition temperature of TCNQCN, 1. Enough time can be secured for thermal decomposition.

In addition, since sufficient characteristics can be obtained with one-time impregnation, the impregnation work becomes easier and expensive TCNQtu salt can be used unnecessarily. It is extremely beneficial for improving sexual performance.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of the structure of a capacitor element used in an embodiment of the present invention, FIG. 2 is a cross-sectional view of a solid electrolyte impregnation device of the present invention, and FIG. FIG. 2 is a cross-sectional view showing a completed state of the solid electrolytic capacitor. ■...Capacitor element, 2...Anode, 3...Collector electrode, 4
Separator paper, 5.6 Tab, 7°8 External lead, 10 Preheating block, 11.13 Recess, 12 Impregnation block, 14 Mixture, 20...
Exterior case, 21... Elastic sealing body. Patent applicant Nippon Chemi-Con Co., Ltd. Figure 1 Figure 2

Claims (4)

[Claims] (1) In a solid electrolytic capacitor in which a dielectric oxide film is formed on the anode metal surface and a solid electrolyte layer is further formed on the upper surface of the solid electrolyte layer, the solid electrolyte layer is made of tetracyanoquinodimethane and methylisoquinolinium. A solid electrolytic capacitor comprising a mixture of a complex salt and a lactone compound. (2) The lactone compound is γ-butyrolactone, γ-
Valerolactone, δ-valerolactone, ε-caprolactone, γ-heptalactone, δ-nonalactone, DL-
The solid electrolytic capacitor according to claim 11, wherein the solid electrolytic capacitor is one or more selected from the group of pantoylactones. (3) In a solid electrolytic capacitor in which a dielectric oxide film is formed on the surface of the anode metal, and a solid electrolyte layer is further formed on the upper surface of the solid electrolyte layer, the solid electrolyte layer is formed with tetracyanoquinodimethane and methyl isochloride. To the complex salt of Norinium,
A mixture formed by adding a lactone compound is heated to a temperature lower than the decomposition temperature of the tetracyanoquinodimethane complex salt to liquefy it, a capacitor element is impregnated into this liquid mixture, and after the impregnation, the capacitor element is cooled and solidified. A method for manufacturing a solid electrolytic capacitor, characterized by: (4) The lactone compound is γ-butyrolactone, γ-
Valerolactone, δ-valerolactone, ε-caprolactone, γ-heptalactone, δ-nonalactone, DL-
The method for producing a solid electrolytic capacitor according to claim (3), wherein the solid electrolytic capacitor is one or more selected from the group of pantoyllactones.