JPH07283087A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a solid electrolytic capacitor employing a TCNQ complex having low low variation rate in capacitance as an electrolyte in which the hermetic sealing properties are enhanced. CONSTITUTION:A capacitor element 3 comprising an anode foil, a cathode foil, a spacer paper, and an electrolytic layer principally comprising a complex salt containing TCNQ is set in a metal case 4. The opening of the case 4 is then sealed with polyphenylene sulfide resin 6 or the entire surface of the case 4 is coated with polyphenylene sulfide resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing and exterior structure for a solid electrolytic capacitor made of an organic semiconductor.

[0002]

2. Description of the Related Art In recent years, with the sophistication of electronic information devices, there has been a demand for downsizing and high performance of electronic parts. Even in electrolytic capacitors, conventional electrolytic capacitors impregnated with a driving electrolytic solution have been demanded. A solid electrolytic capacitor using a tetracyanoquinodimethane (hereinafter referred to as TCNQ) complex, which can be miniaturized, as a solid electrolyte has been put into practical use.

Conventionally, in a solid electrolytic capacitor using a TCNQ complex as a solid electrolyte, a lead wire is fixed to a pair of valve action metal foils of aluminum, tantalum, niobium, etc., which are first roughened by etching, and a manila paper, etc. The capacitor element is formed by winding it through the spacer paper. Next, the TCNQ complex is put into a metal case such as aluminum and heated to melt and liquefy, and the capacitor element preheated to a temperature near the melting point of the TCNQ complex is housed therein and impregnated with the TCNQ complex, and immediately. After cooling and solidification, the opening of the metal case is sealed with epoxy resin and aged to repair the damage to the dielectric oxide film that occurred during the manufacturing process, resulting in a finished product. It is a product that meets the demand of.

The TCNQ complex has a conductivity of about 10 S /
cm and the electrolytic solution of a conventional electrolytic capacitor (0.01 S /
cm), and by using this TCNQ complex as a solid electrolyte, it is possible to obtain a solid electrolytic capacitor excellent in various characteristics such as impedance frequency characteristics, leakage current characteristics, and temperature characteristics.

However, since the metal case opening of the solid electrolytic capacitor having the above-mentioned structure is sealed by injecting a thermosetting resin having a high hardness such as an epoxy resin, the shrinkage at the time of curing or the heat at the time of heating is cured. As a result of the large shear stress acting due to the difference in expansion coefficient, a crack is generated between the sealing resin and the metal case, the TCNQ complex inside is exposed to the outside air, and the TCNQ complex reacts with oxygen and water vapor in the outside air.
The CNQ complex deteriorates and the capacitance decreases rapidly, tan δ
It has a drawback of poor reliability such that the capacitor function deteriorates with the lapse of time due to the increase of the capacitor.

Therefore, it is conceivable to coat the capacitor element impregnated with the TCNQ complex with a thermosetting resin such as epoxy or phenol by transfer molding.
The resin temperature and mold temperature in transfer molding are 20
0 to 300 ° C is reached, and in addition, since transfer molding takes a long time to complete the molding, the capacitor element stays at a high temperature for a long time. Therefore, the capacitor element is thermally deteriorated or impregnated into the capacitor element. The solid electrolyte deteriorates. That is, especially TCN
The Q complex may be melted at 200 to 260 ° C. and may be insulated in a few tens of seconds. Therefore, when the TCNQ complex is used as the main component as the solid electrolyte, the electrical characteristics are adversely affected in transfer molding and the electrolytic capacitor is used. It was difficult to commercialize.

It is also important that the epoxy resin is TCN
To react with the Q complex. Therefore, the TCNQ complex that comes into contact with the epoxy resin filled to seal the opening of the metal case reacts and dissolves and dissolves into the epoxy resin, which causes a problem of degrading the ESR and tan δ of the capacitor. The epoxy resin is
It is a resin that is not suitable as a filling resin for the case opening of a capacitor using a TCNQ complex.

[0008]

As described above, in the above-mentioned prior art, there is a problem that the cracking occurs between the sealing resin and the metal case to deteriorate the capacitor characteristics and the reliability is poor, and the sealing resin has a thermosetting property. Since the resin is used, it takes several hours to cure the resin, the time balance between the respective steps is easily lost, and there is a problem that a smooth flow is obstructed.

Further, in the epoxy resin as a resin for sealing the opening of the case, the TCNQ complex in contact reacts with the epoxy resin and melts into the epoxy resin to produce ESR or tanδ of the capacitor.
Had the drawback of deteriorating.

The present invention solves the above-mentioned problems, and by improving the sealing resin and the sealing method, the factors that cause deterioration of the capacitor characteristics are eliminated, and a smooth process flow is constituted. An object is to provide an inexpensive and highly reliable solid electrolytic capacitor using a TCNQ complex as an electrolyte.

[0011]

A solid electrolytic capacitor according to the present invention comprises an anode foil, a cathode foil and spacer paper.
A structure comprising a capacitor element formed with an electrolyte layer containing a complex salt containing CNQ as a main component, a metal case housing the capacitor element, and a polyphenylene sulfide resin in which at least the opening of the metal case is sealed. Is.

[0012]

According to the solid electrolytic capacitor having the above-described structure, the capacitor element and at least the opening of the metal case for housing the capacitor element are externally molded by injection molding with polyphenylene sulfide resin. Even if the sulfide resin peels off, there is no possibility that the capacitor element will come into contact with the outside air,
Therefore, it is possible to obtain a capacitor element with dramatically improved reliability.

Further, by performing the outer packaging by injection molding using a polyphenylene sulfide resin which is a thermoplastic resin, the time required for the outer packaging can be shortened to about 1 second per element, and the rationalization of the line and the cost reduction can be achieved. Is something that can be done.

[0014]

EXAMPLES Examples of the present invention will be described below. That is, as shown in FIG. 1, an anode foil made of aluminum roughened by a known means and having a dielectric oxide film formed thereon and a cathode foil similarly roughened are drawn by ultrasonic welding or the like. The lead wires 1 and 2 were fixed. A capacitor paper was formed by interposing a spacer paper between the anode foil and the cathode foil so that the lead wires 1 and 2 were positioned in the same direction. This capacitor element was immersed in a 3% aqueous solution of ammonium adipate and re-formed by applying a voltage to repair the damaged portion of the dielectric oxide film generated during the winding process. Next, the TCNQ complex is put in an aluminum case 4 and placed on a flat heater of about 300 ° C. to melt and liquefy, and the capacitor element 3 preheated to about 300 ° C. is put therein, and the TCNQ complex is put into the TCNQ complex.
Immerse the Q complex 5 and immediately put the capacitor element 3 together with the aluminum case 4 in cooling water to cool the TCNQ complex 5
Was solidified. Next, the capacitor element 3 together with the case 4 is set in a mold of 130 ° C., a polyphenylene sulfide resin is injected at a cylinder temperature of 290 ° C. to form an exterior resin layer 6, and then the lead-out lead is put in an atmosphere of 125 ° C. A rated voltage was applied between the wires 1 and 2 for 90 min to perform aging treatment, and then the cathode, rating, etc. were marked to complete the product.

Next, the results of an investigation of the characteristics of the solid electrolytic capacitor according to the present invention thus obtained and the solid electrolytic capacitor obtained by the prior art will be described. That is, the capacitance and tan of the following examples and conventional examples
Table 1 shows the initial values of δ, leakage current, and ESR at 100 kHz, and Table 2 shows the rate of change in capacitance with respect to each elapsed time when each of them was subjected to a life test by applying a rated voltage in an atmosphere of 105 ° C. Show.

The samples are rated at 20 V-3.3 μF, the number of each is 100, and the numerical values are average values.

In the conventional example, a capacitor element was constructed by the same means as in the example, impregnated with the TCNQ complex, and then the opening of the aluminum case was filled with epoxy resin.
It was pre-cured at 0 ° C. for 2 hours, then at 105 ° C. for 2 hours, and naturally cooled. Subsequent aging treatment was performed in the same manner as in the example to obtain a capacitor.

[0018]

[Table 1]

[0019]

[Table 2]

As is clear from Table 1 above, there is no difference in the initial characteristics between the embodiment and the conventional example, but looking at the capacitance change rate shown in Table 2, the capacitance change rate of the conventional example is shown. Shows a much larger value than in the examples. This is due to incomplete adhesion between the aluminum case and the epoxy resin. As a result of observing the element after the test, it was found that the aluminum case and the epoxy resin were peeled off and cracked. On the other hand, the example shows that the rate of change in capacitance is small and the hermeticity is significantly improved, as is clear from Table 2.

The present invention is limited to the polyphenylene sulfide resin as the exterior resin (including the sealing), but instead of this, injection molding is possible and the heat resistant temperature is high,
Aromatic polyethylene and the like exist as a resin that does not react with the TCNQ complex, but aromatic polyethylene has poor moisture resistance, and thus the rate of change in capacitance is large.

Although the spiral type capacitor element has been described in the above embodiment, the same effect can be obtained in the case of the laminated type in which the anode foil and the cathode foil are laminated via the spacer. Further, in the examples, the case where the entire surface of the case is covered with the polyphenylene sulfide resin and is described as the outer case is described, but at least the case opening or the vicinity of the opening is sealed with the polyphenylene sulfide resin, and the configuration in which the hermeticity is improved is also within the scope of the present patent include.

Although the lead wires to the outside are drawn out from the same direction by way of example, the present invention is not limited to this, and the lead wires to the outside may be drawn from opposite directions. Of course good things.

[0024]

As described above, according to the present invention, it is possible to provide a solid electrolytic capacitor which is excellent in hermeticity, has a small capacitance change rate, is highly reliable, and has a high practical value.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of a solid electrolytic capacitor according to the present invention.

[Explanation of symbols]

 1 Lead Out Lead Wire 2 Lead Out Lead Wire 3 Capacitor Element 4 Aluminum Case 5 TCNQ Complex 6 Polyphenylene Sulfide Resin

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Claims (3)

[Claims] 1. A capacitor element formed of an anode foil, a cathode foil and a spacer paper, on which an electrolyte layer containing a complex salt containing tetracyanoquinodimethane as a main component is formed, a metal case containing the capacitor element, and at least the capacitor element. A solid electrolytic capacitor comprising a polyphenylene sulfide resin in which an opening of a metal case is sealed. 2. The solid electrolytic capacitor according to claim 1, wherein the polyphenylene sulfide resin covers the entire surface of the metal case. 3. The solid electrolytic capacitor according to claim 1 or 2, wherein the capacitor element is a wound type or a laminated type.