JP3978822B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor with improved resin sealing and aging of a capacitor element.
[0002]
[Prior art]
Electrolytic capacitors consist of valve action metals such as tantalum and aluminum, and an oxide film layer that forms a dielectric on the surface of the anode electrode with micropores and etching pits. The electrode is drawn from this oxide film layer. Has been.
[0003]
And extraction of the electrode from an oxide film layer is performed by the electrolyte layer which has electroconductivity. Therefore, in the electrolytic capacitor, the electrolyte layer serves as a true cathode. For example, in an aluminum electrolytic capacitor, a liquid electrolyte is used as a true electrode, and the cathode electrode is merely responsible for electrical connection between the liquid electrolyte and an external terminal.
[0004]
The electrolyte layer that functions as a true cathode is required to have adhesiveness, denseness, and uniformity with the oxide film layer. In particular, the adhesion within the fine holes of the anode electrode and the etching pits has a great influence on the electrical characteristics, and a number of electrolyte layers have been proposed in the past.
[0005]
A solid electrolytic capacitor uses a solid electrolyte having conductivity instead of a liquid electrolyte lacking in impedance characteristics in a high frequency region because of ionic conduction. Among them, manganese dioxide, 7, 7, 8, 8- Tetracyanoquinodimethane (TCNQ) complexes are known. On the other hand, various conductive polymers have been studied, and the technology focused on polyethylenedioxythiophene (PEDT), which has a slow reaction rate and excellent adhesion to the oxide film layer of the anode electrode. (Japanese Patent Laid-Open No. 2-15611) exists.
[0006]
For example, as shown in FIG. 4, a solid electrolytic capacitor having a solid electrolyte layer is manufactured by a manufacturing process of chemical conversion → element formation → solid electrolyte layer formation → resin sealing → aging. Hereinafter, as an example of such a solid electrolytic capacitor, a manufacturing process of a solid electrolytic capacitor of a type in which a solid electrolyte layer made of polyethylenedioxythiophene is formed on a wound capacitor element will be described with reference to FIGS. And explain briefly.
[0007]
First, as shown in FIG. 6, after the surface of the anode foil 1 made of a valve metal such as aluminum is roughened by electrochemical etching treatment in an aqueous chloride solution to form a large number of etching pits 8 Then, a voltage is applied in an aqueous solution of ammonium borate or the like to form an oxide film layer 4 serving as a dielectric (chemical conversion). As with the anode foil 1, the cathode foil 2 as shown in FIG. 5 is made of a valve metal such as aluminum, but the surface is only subjected to an etching process. Further, as shown in FIG. 5, lead wires 6 and 7 for connecting the respective electrodes to the outside are connected to the anode foil 1 and the cathode foil 2 by known means such as stitching or ultrasonic welding.
[0008]
Next, the anode foil 1 and the cathode foil 2 having the oxide film layer 4 formed on the surface as described above are wound through the separator 3 as shown in FIG. 5 to form the capacitor element 10. (Element formation). Then, the capacitor element 10 is impregnated with ethylenedioxythiophene and an oxidizing agent to produce a solid electrolyte layer 5 made of polyethylenedioxythiophene as shown in FIG. 6 (solid electrolyte layer formation).
[0009]
Thereafter, a thermosetting resin such as an epoxy resin is attached to the surface of the capacitor element 10 and thermally cured to coat the outer periphery of the capacitor element 10 (resin sealing), thereby completing a solid electrolytic capacitor. . If resin sealing is performed in this way, the oxide film layer 4 is damaged and leakage current characteristics are lowered. Therefore, after resin sealing, a voltage corresponding to the capacitor rated voltage is applied to perform high-temperature aging. Thus, the oxide film layer 4 is repaired to improve the characteristics.
[0010]
By the way, when an epoxy resin is used as the exterior resin, it is necessary to perform the resin main curing after the resin temporary curing from the viewpoint of stress prevention. There are two typical procedures as shown in FIGS. Here, the procedure shown in FIG. 7 and FIG. 8 is a specific procedure when an epoxy resin using an acid anhydride curing agent is used.
[0011]
That is, the first procedure shown in FIG. 7 is “resin temporary curing (100 to 140 ° C. × 1 to 2 hr) → resin main curing (130 to 180 ° C. × 2 to 3 hr) → high temperature aging (80 to 120 ° C. × 1 hr) ) ", And is performed once after the resin is completely cured. Further, the second procedure shown in FIG. 8 is “resin temporary curing (100 to 140 ° C. × 1 to 2 hr) → high temperature aging (80 to 120 ° C. × 1 hr) → resin main curing (130 to 180 ° C. × 2 to 3 hr) ) → High temperature aging (80 to 120 ° C. × 1 hr) ”, and aging is performed not only after the resin main curing but also at the time after the resin temporary curing before the resin main curing.
[0012]
[Problems to be solved by the invention]
However, when using the procedures shown in FIGS. 7 and 8 for resin sealing and aging of the solid electrolytic capacitor, the process is complicated and the productivity tends to decrease, and the leakage current is reduced. It is difficult and a short circuit may occur. In this case, according to the second procedure (FIG. 8) in which aging is performed twice, the leakage current can be reduced to some extent as compared with the first procedure (FIG. 7) in which aging is performed once. The required time is about 5 to 7 hours longer than that of the first procedure is about 4 to 6 hours, and the productivity is low. In addition, since the jig for curing used at the time of resin curing is different from the jig for voltage application used at the time of aging, in the second procedure in which resin curing and aging are alternately performed, jig replacement is performed three times. From this point, productivity is further reduced.
[0013]
The present invention has been proposed in order to solve such problems of the prior art, and its purpose is to efficiently carry out resin sealing and aging after the formation of the solid electrolyte layer, and to provide electrical current such as leakage current. An object of the present invention is to provide a production method with excellent productivity capable of producing a solid electrolytic capacitor having excellent characteristics.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method for producing a solid electrolytic capacitor according to the present invention comprises forming an oxide film layer on the surface of an anode body made of a valve metal as described in claim 1, and using the anode body. After forming a capacitor element and forming a solid electrolyte layer on the surface of the oxide film layer, a liquid resin is attached to the capacitor element and resin sealing is applied to cure the resin. the method of manufacturing a solid electrolytic capacitor which performs the aging voltage is applied to the capacitor element during curing of the liquid resin during the resin encapsulation to repair damage to the oxide film layer, as a curing of the liquid resin, the first After the resin is temporarily cured to cure the resin to some extent at the temperature of the resin, the resin is completely cured at a second temperature higher than the first temperature, and at least the resin temporary cure is performed. A voltage is applied to the capacitor element to perform the aging, a voltage is applied to the capacitor element during the temporary resin curing, and the first aging is performed, and the aging is not performed during the resin main curing. A characteristic is that after the curing is completed, a voltage is applied to the capacitor element to perform the second aging.
[0015]
According to the manufacturing method of claim 1 having the above-described configuration, the aging voltage is not applied after the resin is cured, but by applying an aging voltage to the capacitor element during the resin curing, the withstand voltage of the capacitor is reduced. Secures and reduces leakage current. The reason is considered as follows.
[0016]
First, in order to ensure sufficient characteristics such as withstand voltage and leakage current in a solid electrolytic capacitor, it is necessary to retain a certain amount of moisture in the capacitor element. Since moisture is removed, the withstand voltage of the element after resin curing decreases. In contrast, in the present invention, by applying an aging voltage before or after the capacitor element is exposed to a high temperature for resin curing, an electric field forcing force that overcomes the evaporation force of moisture is applied. Since the moisture in the capacitor element can be retained by acting, it is considered that the breakdown voltage of the capacitor can be secured and the leakage current can be reduced. Furthermore, since water is also necessary for repairing the oxide film layer during aging, it is considered that the oxide film layer can be repaired satisfactorily by performing aging from the time when sufficient moisture exists in the capacitor element. It is done.
[0018]
Further , when the resin curing is performed in two stages of the resin temporary curing and the resin main curing, by performing aging at least during the resin temporary curing, the withstand voltage of the capacitor can be secured and the leakage current can be reduced. This is considered to be because the oxide film layer can be satisfactorily repaired using moisture from the time when sufficient moisture is present in the capacitor element, and evaporation of moisture can be effectively prevented.
[0022]
In addition , by performing the first aging during resin temporary curing and performing the second aging after resin main curing, aging is not performed during resin main curing at a much higher temperature than normal aging. It is easy to select a jig to be used, and the cost for the jig can be suppressed low.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a method for producing a solid electrolytic capacitor according to the present invention will be specifically described below with reference to the drawings. For convenience of explanation, a solid electrolytic capacitor of a type in which a solid electrolyte layer made of polyethylenedioxythiophene is formed on a wound capacitor element will be described as in the conventional technique described above.
[0024]
First, in the present embodiment, the procedure from chemical conversion to solid electrolyte layer formation is the same as that of the prior art described above, and the oxide film layer 4 is formed on the surface of the anode foil 1 as shown in FIG. Then, as shown in FIG. 5, the anode foil 1 and the cathode foil 2 are wound through the separator 3 to form a winding type capacitor element 10, and then the oxide film layer 4 of the anode foil 1 as shown in FIG. A solid electrolyte layer 5 is formed thereon.
[0025]
And in this Embodiment, it has the characteristics in the procedure of resin sealing and aging after forming a solid electrolyte layer in this way. That is, aging is not performed after resin sealing, but is performed during curing of the liquid resin during resin sealing. 1 and 2 show the resin sealing and aging procedures according to the present invention, as in the prior art shown in FIGS. 7 and 8, the resin sealing resin is an acid anhydride curing agent. The two specific procedures in the case of an epoxy resin using the above are shown.
[0026]
That is, the first procedure shown in FIG. 1 is to perform “resin temporary curing (100 to 140 ° C. × 1 to 2 hours) → resin main curing (130 to 180 ° C. × 2 to 3 hours)” and at the same time, this resin temporary curing. And continuous high-temperature aging (100 to 140 ° C. × 1 to 2 hours + 130 to 180 ° C. × 2 to 3 hours) are performed over both the main curing of the resin and the resin. The second procedure shown in FIG. 2 is “high temperature aging during resin temporary curing (100 to 140 ° C. × 1 to 2 hours) → main resin curing (130 to 180 ° C. × 2 to 3 hours) → high temperature aging (80 to 120 ° C. × 1 hr) ”, and the first aging is performed during the temporary resin curing, and the second aging is performed after the main resin curing.
[0027]
The operation of the present embodiment having the above-described configuration is as follows.
That is, instead of performing aging after resin curing as in the prior art, by applying a voltage for aging to the capacitor element during resin curing, the oxide film layer is formed with sufficient moisture in the capacitor element 10 secured. Since it can be repaired satisfactorily, the withstand voltage of the capacitor can be secured and the leakage current can be reduced. The reason is considered as follows.
[0028]
First, in order to sufficiently secure characteristics such as withstand voltage and leakage current in a solid electrolytic capacitor, it is necessary to retain a certain amount of moisture (adsorbed water, crystal water, etc.) in the capacitor element. That is, if a voltage is applied at room temperature with a certain amount of moisture adsorbed on the capacitor element, the leakage current decreases. However, when a voltage is applied at a high temperature, the moisture evaporates from the capacitor element, so that the withstand voltage may rapidly decrease and a short circuit may occur. Further, if the capacitor element is dried to remove moisture, the withstand voltage may decrease even at room temperature.
[0029]
Exposing such a capacitor element to a high temperature for curing the resin means removing the necessary moisture, and if the resin used at that time is an acid anhydride-based curing agent, the capacitor is used by this resin. There is also a possibility that moisture in the element is deprived. Therefore, the withstand voltage of the element after resin curing decreases.
[0030]
On the other hand, in the present invention, the moisture from the capacitor element 10 is applied by applying an aging voltage before or after the capacitor element 10 is exposed to a high temperature of about 100 to 180 ° C. for resin curing. It is considered that the forcible force of the electric field that overcomes the evaporating power of the capacitor can be applied to sufficiently retain the moisture in the capacitor element 10, so that the withstand voltage of the capacitor can be secured and the leakage current can be reduced. Furthermore, since water is necessary for repairing the oxide film layer 4 in aging, the oxide film layer 4 can be repaired satisfactorily by performing aging from the time when sufficient moisture exists in the capacitor element 10. It is considered a thing.
[0031]
In addition, in this embodiment, in any procedure, by performing aging during the resin temporary curing, the oxide film layer is satisfactorily utilized from the time when the moisture is sufficiently present in the capacitor element. It is considered that the water can be effectively repaired and the evaporation of moisture can be effectively prevented.
[0032]
In particular, in the first procedure shown in FIG. 1, by performing aging over both the resin temporary curing and the resin main curing, the oxide film is effectively utilized by fully utilizing the resin curing time of about 3 to 5 hours. Since the repair of the layer 4 can be completed, the conventional procedure of FIG. 7 in which the aging is performed only once after the resin main curing, or the first aging after the resin temporary curing and the second aging after the resin main curing is performed. Compared with the conventional procedure of FIG. 8 which has been carried out, it is possible to ensure remarkably superior characteristics.
[0033]
And since aging can be completed within a resin curing time of about 3 to 5 hours, the time required for resin sealing and aging can be shortened to about 3 to 5 hours as compared with the prior art in which aging is performed after resin sealing. . That is, a time reduction of 2 to 3 hours can be realized as compared with the prior art procedure in which the resin sealing and aging took 5 to 8 hours.
[0034]
In addition, as described above, since continuous aging is performed only once during resin curing, the process can be simplified as compared with the conventional technique in which aging is performed after resin curing. There is no need to replace the jig for voltage application. In the case of an epoxy resin, since the main curing of the resin is performed at a high temperature of about 130 to 180 ° C. compared to the normal aging of about 80 to 120 ° C., a conventionally used voltage application jig is used. It is necessary to select a jig having better heat resistance.
[0035]
On the other hand, in the second procedure shown in FIG. 2, the first aging is performed during the temporary resin curing, and the second aging is performed after the main resin curing, so that the epoxy resin has a high temperature of about 130 to 180 ° C. Since aging is not performed during the main curing of the resin, it is easy to select a jig to be used, and the cost for the jig can be suppressed lower than that in the first procedure. On the other hand, when aging is performed after the resin is fully cured, the time is longer than that of the first procedure by 1 hour which is the second aging time, and the required time is 4 to 6 hours.
[0036]
This second procedure is the same as the conventional procedure of FIG. 7 in which the aging is performed only once after the resin main curing for the required time, but since the aging is performed during the resin temporary curing, the conventional procedure of FIG. Compared with the procedure, it is possible to ensure dramatically superior characteristics. Further, when the second procedure is compared with the conventional procedure of FIG. 8 in which the first aging is performed after the resin temporary curing and the second aging is performed after the resin main curing, the required time is 1-2 hours. In addition to shortening, it is possible to ensure dramatically superior characteristics.
[0037]
As a modification of the first and second procedures as described above, aging may be performed only during temporary resin curing. The characteristics obtained in this case are lower than those in the above procedures, but sufficiently superior characteristics can be ensured as compared with the prior art. Further, depending on the selection of the resin, the temporary curing may not be performed, and the aging may be performed only during the resin main curing.
[0038]
【Example】
Next, a method for producing a solid electrolytic capacitor according to the present invention and examples of the solid electrolytic capacitor obtained thereby will be described in detail in comparison with comparative examples.
First, in the same manner as in the prior art and the embodiment described above, among solid electrolytic capacitors of a type in which a solid electrolyte layer made of polyethylene dioxythiophene is formed on a wound capacitor element, particularly a solid electrolytic capacitor having a rating of 10 WV22 μF. Three types of solid electrolytic capacitors differing only in resin sealing and aging procedures were produced. That is, the Example which applied the said 1st procedure (FIG. 1) as a manufacturing method which concerns on this invention, the comparative example 1 which applied the procedure shown in FIG. 8 as a manufacturing method which concerns on a prior art, and resin main curing time Three types of solid electrolytic capacitors, that is, Comparative Example 2 in which only a voltage was applied, were produced. In addition, the resin sealing and aging procedures of Comparative Example 2 are “resin temporary curing (100 to 140 ° C. × 1 to 2 hours) → high temperature aging during resin main curing (130 to 180 ° C. × 2 to 3 hours)”. . As for the voltage value at the time of aging, an arbitrary value within a range of 1.0 to 1.5 times the capacitor rating was selected as a common applied voltage in the three methods.
[0039]
And about the solid electrolytic capacitor of the Example produced as mentioned above and Comparative Examples 1 and 2, the voltage of 10V was applied for 2 minutes at room temperature, and when leakage current (LC) was measured, as shown in FIG. Results were obtained. As apparent from the results shown in FIG. 3, the leakage current of the example according to the present invention has a remarkably low value as compared with Comparative Example 1 and Comparative Example 2. This result demonstrates the operation and effect of the embodiment according to the present invention as described above. Moreover, although the breakdown voltage is not described, the characteristics according to the present invention were remarkably improved.
[0040]
The present invention is not limited to the above-described embodiments and examples, and various other modifications can be implemented. For example, the present invention is not limited to the case where resin sealing is performed with an epoxy resin, but can be similarly applied to various solid electrolytic capacitors that perform resin sealing and aging using various resins.
[0041]
In addition, the solid electrolyte layer is not limited to a solid electrolyte layer made of polyethylenedioxythiophene, but various solids such as a solid electrolyte layer made of manganese dioxide or a TCNQ complex, or a solid electrolyte layer made of a conductive polymer such as polypyrrole. The present invention can be similarly applied to a solid electrolytic capacitor that forms an electrolyte layer. Further, the present invention is not limited to the winding type capacitor element, but can be similarly applied to a multilayer type capacitor element.
[0042]
【The invention's effect】
As described above, according to the method for manufacturing a solid electrolytic capacitor according to the present invention, the solid electrolyte is not aged after resin sealing but by aging during curing of the liquid resin at the time of resin sealing. A solid electrolytic capacitor having excellent electrical characteristics such as leakage current can be manufactured by efficiently performing resin sealing and aging after layer formation. In addition, this manufacturing method according to the present invention can reduce the time required for resin sealing and aging as compared with the conventional manufacturing method, and thus is excellent in productivity and is an extremely practical manufacturing method.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an example of resin sealing and aging procedures according to the present invention.
FIG. 2 is a flowchart showing another example of resin sealing and aging procedures according to the present invention.
FIG. 3 is a distribution diagram showing a result of measuring leakage current of each solid electrolytic capacitor of an example according to the present invention and a comparative example.
FIG. 4 is a flowchart showing an outline of a manufacturing process of a solid electrolytic capacitor.
FIG. 5 is an exploded perspective view showing an example of a capacitor element targeted by the present invention.
6 is an enlarged cross-sectional view showing an anode foil of the capacitor element of FIG.
FIG. 7 is a flowchart showing an example of a resin sealing and aging procedure according to the prior art.
FIG. 8 is a flowchart showing another example of the resin sealing and aging procedures according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Anode foil 2 ... Cathode foil 3 ... Separator 4 ... Oxide film layer 5 ... Solid electrolyte layer 6, 7 ... Lead wire 8 ... Etching pit 10 ... Capacitor element

Claims (1)

An oxide film layer is formed on the surface of an anode body made of a valve metal, a capacitor element is formed using the anode body, a solid electrolyte layer is formed on the surface of the oxide film layer, and then liquid to the capacitor element. Resin is applied to harden the resin, and a voltage is applied to the capacitor element during the curing of the liquid resin during the resin sealing in order to repair the oxide film layer damaged by the resin sealing. In the manufacturing method of the solid electrolytic capacitor that performs aging by applying,
As the curing of the liquid resin, after performing the resin temporary curing that cures the resin to some extent at the first temperature, the resin main curing is performed to completely cure the resin at the second temperature higher than the first temperature,
Applying voltage to the capacitor element during at least the resin temporary curing to perform the aging,
A voltage is applied to the capacitor element during the pre-curing of the resin to perform the first aging, and the aging is not performed during the main curing of the resin. A method for producing a solid electrolytic capacitor, wherein the second aging is performed.

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