JP2001203128A - Method of manufacturing solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid electrolytic capacitor superior in leakage current and ESR characteristics by preventing generation of cracks in a dielectric oxide coating film layer and sheath resin. SOLUTION: In this manufacturing method of a solid electrolytic capacitor, the dielectric oxide coating film layer 3, a solid electrolyte layer 4 and a cathode layer 5 are formed in the order on a surface of an anode member 2. A part, from which an anode lead-out line 1 of the anode member 2 is exposed, is fixed with a thermosetting resin 6, and a capacitor element 7 is formed. Covering and forming are performed with the insulating sheath resin 11 in such a manner, that at least a part of an anode terminal 8 connected with the anode lead-out line 1 of the capacitor element 7 and a cathode terminal 10 connected with the cathode layer 5 is exposed on the outer surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer solid electrolyte layer.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become more portable and faster, solid-state electrolytic capacitors, which are electronic components, have been required to be smaller and have higher performance.

In order to meet the demands of this market, various conditions such as the surface condition of the anode constituting the solid electrolytic capacitor, the method of forming the dielectric oxide film, the development and improvement of the solid electrolyte layer, the surface condition of the cathode, the structure of the capacitor element, etc. It is being studied from various angles.

FIG. 2 is a sectional view showing a configuration of a typical solid electrolytic capacitor. A dielectric oxide film layer 23 formed by an anodizing method is provided on the surface of an anode body 22 made of a sintered body of a valve metal such as aluminum or tantalum in which a part of the anode lead wire 21 is exposed. Is formed.
An insulator 2 such as a fluororesin is used for a part of the anode lead wire 21.
7, a solid electrolyte layer 24 using a transition metal oxide such as Mn and Pb, and a cathode layer 25 made of a carbon layer and a silver paste layer are sequentially formed on the surface of the anode body 22 to form a capacitor element 26. The anode terminal 28 connected to the anode lead-out line 21 of the capacitor element 26 and the cathode layer 25
A solid electrolytic capacitor is formed by covering the capacitor element 26 with an insulating exterior resin 31 so that at least a part of the cathode terminal 30 connected via a conductive adhesive 29 is exposed to the outer surface. .

As the characteristics of the solid electrolyte layer 24, organic semiconductor capacitors using a TCNQ salt as a charge transfer complex, pyrrole as a heterocyclic compound,
2. Description of the Related Art Solid electrolytic capacitors using a conductive polymer obtained by polymerizing thiophene, aniline or the like to make it conductive have been put into practical use.

[0006] Such a solid electrolytic capacitor has the characteristic that the specific resistance of the conductive polymer is extremely low, and therefore, the equivalent series resistance (hereinafter referred to as ESR) of the solid electrolytic capacitor.
It is described that characteristics can be reduced.

Further, the conductive polymer solid electrolyte layer 2
For example, US Pat.
As disclosed in the specification 1 and the drawings, a porous capacitor element is repeatedly immersed in a monomer solution containing a monomer and an oxidizing solution containing an oxidizing agent, so that a conductive material is formed inside the porous body. Polymer solid electrolyte layer 24
Have been proposed.

A method for forming an insulator 27 on a part of the anode lead wire 21 is disclosed in JP-A-1-105523.
As disclosed in Japanese Patent Application Laid-Open No. HEI 3-78222, it is intended to facilitate the formation of electrolytic oxidative polymerization after chemical oxidative polymerization and to reduce the contact problem between the anode lead and the solid electrolyte serving as the cathode. After forming a dielectric oxide film on the surface of the sintered element connected to the anode lead, a part of the dielectric oxide film formed on the anode lead is covered with an insulator such as an insulating polymer and then conductive. It has been proposed to form a solid electrolyte layer by chemically oxidative polymerization and electrolytic oxidative polymerization of a conductive polymer.

[0009]

However, the capacitor element 26 in which the dielectric oxide film layer 23, the solid electrolyte layer 24, and the cathode layer 25 are formed on the surface of the anode body 22,
When the exterior is formed by molding with an insulating resin or the like so that at least a part of the anode terminal 28 and the cathode terminal 30 are exposed on the outer surface, the capacitor and the capacitor are passed through the anode terminal 28 by the pressure and heat during the molding. There has been a problem that a defect occurs in the dielectric oxide film layer 23 inside the element 26 and a gap is formed in a contact portion between the anode lead wire 21 and the anode body 22.

The defects generated in the dielectric oxide film layer 23 inside the capacitor element 26 are exposed to a high temperature and a high humidity for a long time to infiltrate the water by diffusion and then apply a voltage higher than the rated voltage. Can be repaired by performing aging, but there is a problem in the method of removing moisture after the repair, and cracks may occur in the dielectric oxide film layer 23 and a part of the exterior resin 31 during the removal of moisture. On the contrary, there is a problem that the ESR characteristic and the leakage current increase.

There is no complete countermeasure against the problem that a gap is formed at the contact portion between the anode lead-out portion 21 and the anode body 22, and a countermeasure is taken by optimizing conditions at the time of molding. is the current situation.

On the other hand, the techniques disclosed in JP-A-1-105523 and JP-A-3-78222 do not disclose fixing the lead wire of the anode. If only a part is covered with an insulator such as an insulating polymer, there will be a defect in the dielectric oxide film layer due to the pressure and heat when molding the exterior resin, and a gap will be formed at the contact between the anode lead wire and the sintered body. The problem of getting lost could not be solved.

The present invention solves such a conventional problem,
It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor that prevents cracks in a dielectric oxide film layer and an exterior resin and has excellent leakage current and ESR characteristics.

[0014]

According to the present invention, there is provided a method for fixing an anode lead wire exposed from an anode body with a thermosetting resin after forming a cathode layer.

According to this method, cracks in the dielectric oxide film and the exterior resin can be prevented, and leakage current and ESR characteristics can be improved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, a dielectric oxide film layer, a solid electrolyte layer,
This is a method for manufacturing a solid electrolytic capacitor in which a cathode layer is sequentially formed, and a portion of the anode body where an anode lead-out line is exposed is fixed with a thermosetting resin to form a capacitor element. According to this method, the anode lead wire is fixed with the thermosetting resin to increase the fixing strength, so that the anode lead wire can withstand the molding pressure of the exterior resin, so that the dielectric oxide film layer and the exterior resin crack. And a solid electrolytic capacitor having excellent leakage current and ESR characteristics can be obtained.

According to a second aspect of the present invention, the solid electrolyte layer is a conductive polymer solid electrolyte layer formed by chemically oxidizing and polymerizing a heterocyclic monomer. In particular, a solid electrolyte layer of a conductive polymer having high conductivity can be formed.
A solid electrolytic capacitor having excellent characteristics can be obtained.

The invention according to claim 3 is characterized in that Na and Cl
It is made of a highly insulating epoxy resin having a total ion content of 10 ppm or less. This forming method uses a thermosetting resin having a viscosity of 100 to 500 poise and a coating amount of 15 to
A method of applying and drying in the range of 50 mg / cm ² to prevent the deterioration of the solid electrolyte layer and the corrosion of the anode lead-out portion, and to securely fix the portion of the anode body where the anode lead-out line appears. Therefore, the yield in the manufacturing process can be significantly improved.

According to a fifth aspect of the present invention, when the anode lead wire is connected to the anode terminal, the thermosetting resin coated on the portion where the anode lead wire is connected to the anode terminal is removed, and the removed portion is removed. Is connected to the anode terminal.When the thermosetting resin is applied, it may be applied even to the connection between the anode lead wire and the anode terminal, increasing the contact resistance. By removing the curable resin, the contact resistance can be reliably reduced.

According to a sixth aspect of the present invention, a part of the thermosetting resin is removed by using laser irradiation, and the removal can be reliably performed with high productivity.

Hereinafter, embodiments of the present invention will be described in detail.

(Embodiment 1) FIG. 1 is a sectional view showing a configuration of a solid electrolytic capacitor obtained according to Embodiment 1 of the present invention. In the figure, first, a molded body of tantalum powder in which an anode lead wire 1 is embedded so that one end thereof is exposed is sintered to obtain an anode body 2. Next, on the surface of the anode body 2, a dielectric oxide film layer 3, a solid electrolyte layer 4 made of a conductive polymer, and a cathode layer 5 made of a carbon layer and a silver paste layer are sequentially formed. Thereafter, the surface portion of the anode body 2 where the anode lead-out line 1 is exposed is fixed with a thermosetting resin 6 to obtain a capacitor element 7. Next, the anode terminal 8 is connected to the anode lead wire 1, and the cathode terminal 10 is connected to the cathode layer 5 of the capacitor element 7 via the conductive adhesive 9. A solid electrolytic capacitor is obtained by forming a coating with an exterior resin 11 so that a part of the terminal 10 is exposed.

In order to further improve the performance of the obtained solid electrolytic capacitor, the capacitor is exposed to a high temperature and a high humidity for a long time, moisture is infiltrated into the capacitor by diffusion, and a voltage higher than the rated voltage is applied. Aging is performed, and then moisture is removed by drying to obtain a finished product.

Solid electrolyte layer 4 made of the above conductive polymer
Is formed by individually impregnating the surface of the anode body 2 on which the dielectric oxide film layer 3 is formed with a polymerization solution containing a heterocyclic monomer and an oxidation solution containing an oxidizing agent, and then cleaning and repairing the surface. The step of chemical formation is repeated a plurality of times to form the solid electrolyte layer 4, or the step of impregnating with a mixed solution containing a heterocyclic monomer and an oxidizing agent is performed a plurality of times to form the solid electrolyte layer 4. Alternatively, the polymerization solution containing the heterocyclic monomer and the oxidizing solution containing the oxidizing agent are individually impregnated with each other, and the steps of washing and repair formation are repeated a plurality of times. The solid electrolyte layer 4 can also be formed by repeatedly performing the step of impregnating the mixed solution to be performed a plurality of times.

The heterocyclic monomer is, for example, any one of pyrrole, thiophene, aniline and furan, preferably pyrrole and 3.4-ethylenedioxythiophene. The highly conductive solid electrolyte layer 4 can be easily obtained.

As the oxidizing agent, for example, ferric salt, persulfate, permanganate, hydrogen peroxide and the like are used, and iron sulfate and ferric p-toluenesulfonate are preferably used.

As a method for forming the thermosetting resin 6, for example, a paste-like epoxy resin is
Is applied with a dispenser or the like to a portion where the anode lead-out line 1 is exposed, dried and cured. Since the thermosetting resin 6 comes into contact with the anode lead wire 1 and the solid electrolyte layer 4, it is preferable that the thermosetting resin 6 has high insulating properties and contains as little corrosive substance as possible. Therefore, the thermosetting resin 6 preferably has a total content of Na and Cl ions of 10 ppm or less. 10p
If it exceeds pm, corrosion of the anode lead wire 1 and leakage current and ESR characteristics as a capacitor become high.

In the application of the thermosetting resin 6, a resin having a viscosity of 100 to 500 poise is used.
It is applied in a range of 50 mg / cm ² . By setting the application amount, the coating can be uniformly applied to the surface portion of the anode body 2 where the anode lead-out wire 1 is exposed, and the fixing strength of the cured anode lead-out wire 1 can be increased.

In the above application amount, the viscosity is 100
If it deviates from ~ 500 poise, the amount of application is 15 ~ 50mg /
cm^TwoIt is difficult to control in the range of
The fixing strength of the pole lead wire 1 cannot be increased. Ma
The application amount is 15 mg / cm ^TwoIf less than, the anode body 2
The fixing strength of the part where the pole lead wire 1 appears becomes insufficient,
Due to the molding pressure of the exterior resin 11, the dielectric oxide film layer 3 and
And the exterior resin 11 is cracked. In addition,
Cloth amount 50mg / cm^TwoIs exceeded, the capacitor element 7
Adheres to the peripheral part of
Therefore, it does not fit within the prescribed external dimensions.

As described above, according to the first embodiment, the anode lead wire 1 is fixed to the anode body 2 by the thermosetting resin 6 to increase the fixing strength. 11 can withstand the molding pressure of 11 and eliminate cracks in the dielectric oxide film layer 3 and the exterior resin 11, thereby obtaining a solid electrolytic capacitor having low leakage current and ESR characteristics.

(Second Embodiment) In the first embodiment, the connection between the anode lead wire 1 and the anode terminal 8 is made by setting the thermosetting resin 6 previously attached to the portion where the anode lead wire 1 is connected to the anode terminal 8. After removing and exposing the surface of the anode lead wire 1, a solid electrolytic capacitor was obtained in the same manner as in the first embodiment except that the exposed anode lead wire 1 and the anode terminal 8 were connected.

As the removal method, removal by heating is preferable, and removal by laser irradiation, hot air heating, or the like can be used.

According to the second embodiment, the contact resistance between the anode lead wire 1 and the anode terminal 8 becomes smaller, and the ESR characteristic of the solid electrolytic capacitor can be further reduced.

Hereinafter, specific embodiments of the present invention will be described.

Example 1 First, a tantalum powder was formed so that a part of an anode lead wire formed of a tantalum lead wire was exposed, and then sintered to a thickness of 1.4 mm and a width of 3.0 mm.
An anode body having a length of 3.8 mm was obtained. The surface of the anode body was formed with a phosphoric acid aqueous solution at a formation voltage of 20 V to form a dielectric oxide film.

Next, the anode body was added to an aqueous solution containing 10 wt% of ethylene glycol by adding 1.0 mol / l of pyrrole as a heterocyclic monomer and 0.25 mol / l of sodium alkylnaphthalenesulfonate as a dopant.
The polymer was immersed in a polymerization solution adjusted to be 5 minutes and pulled up. Immediately, an aqueous solution containing 10% by weight of ethylene glycol was added with 0.75 mol /
After being immersed in an oxidizing solution adjusted to 1 l for 10 minutes and pulled up, the anode body was washed, repaired and dried (1).
00 ° C.). This series of operations was repeated 10 times to form a conductive polymer solid electrolyte layer.

Next, a carbon layer and a silver layer were sequentially formed on the surface of the solid electrolyte layer to obtain a capacitor element.

Next, an epoxy resin having a viscosity of 100 poise (Na ion content 1 ppm, Cl ion content 5
ppm) using a dispenser with a syringe.
5 mg / cm ² was applied, dried and cured. Then, connect the anode lead wire and the anode terminal, and connect the cathode terminal to the cathode layer of the capacitor element via a conductive adhesive, so that the exterior resin is exposed so that part of the anode terminal and the cathode terminal are exposed. To form a coating. Finally, after being exposed to high temperature and high humidity for 24 hours to infiltrate moisture into the interior by diffusion,
Aging is performed by applying a voltage of V
And gradually dried to 150 ° C. to remove water to produce a tantalum solid electrolytic capacitor (D size:
7.3 × 4.3 × 2.8 mm).

Example 2 A tantalum solid electrolytic capacitor was manufactured in the same manner as in Example 1 except that the amount of the epoxy resin applied was changed to 50 mg / cm ² .

(Example 3) In Example 1, the viscosity of the epoxy resin was 500 poise and the coating amount was 15 mg / c.
except that the m ² was produced tantalum solid electrolytic capacitor in the same manner as in Example 1.

Example 4 In Example 1, the viscosity of the epoxy resin was 500 poise and the coating amount was 50 mg / c.
except that the m ² was produced tantalum solid electrolytic capacitor in the same manner as in Example 1.

Example 5 Tantalum solid electrolysis was carried out in the same manner as in Example 1 except that the epoxy resin had a Na ion content and a Cl ion content of 5 ppm and 5 ppm, respectively. A capacitor was manufactured.

(Example 6) In Example 1, the connection between the anode lead wire and the anode terminal was performed by irradiating the epoxy resin, which had been previously attached to the portion of the anode lead wire connecting the anode terminal, with laser (condition: ON time 8 msec- OFF time 300mse
c was repeated several times to make the total amount of heat 10 W). Thereafter, a tantalum solid electrolytic capacitor was produced in the same manner as in Example 1, except that the portion of the anode lead wire irradiated with the laser was connected to the anode terminal.

Comparative Example 1 A tantalum solid electrolytic capacitor was manufactured in the same manner as in Example 1 except that the step of applying the epoxy resin was omitted.

Comparative Example 2 A tantalum solid electrolytic capacitor was produced in the same manner as in Example 1 except that the amount of the epoxy resin applied was changed to 10 mg / cm ² .

Comparative Example 3 A tantalum solid electrolytic capacitor was produced in the same manner as in Example 1 except that the amount of the epoxy resin applied was changed to 55 mg / cm ² .

Comparative Example 4 Tantalum solid electrolyte was prepared in the same manner as in Example 1 except that the epoxy resin had a Na ion content and a Cl ion content of 5 ppm and 10 ppm, respectively. A capacitor was manufactured.

Examples 1 to 3 of the present invention produced as described above
6 and the tantalum solid electrolytic capacitors of Comparative Examples 1-4, the capacitance at 120 Hz and the ESR at 100 kHz
Table 1 shows the results of comparison of the characteristics, the leakage current value (30 seconds after application of the rated voltage), the number of short circuits after aging, and the contact resistance between the anode lead wire and the anode terminal.

[0049]

[Table 1]

The number of test pieces is 50 each, and ES
The values of R, leakage current, and contact resistance are shown as average values for samples excluding short-circuited products.

As is clear from Table 1, the tantalum solid electrolytic capacitors of Examples 1 to 5 of the present invention were compared with Comparative Example 1
Compared to the tantalum solid electrolytic capacitors, the ESR characteristics and the leakage current characteristics are improved by applying epoxy resin to the part where the tantalum lead wire of the capacitor element is exposed, drying and curing it. The number of short circuits after aging can be drastically reduced.

The tantalum solid electrolytic capacitors of Examples 1 and 5 of the present invention and Comparative Example 4 differ in the content of Na ion and Cl ion in the epoxy resin. Total content of 1
If it exceeds 0 ppm, the ESR characteristics and the leakage current characteristics will be high, the number of short circuits after aging will increase, and the capacitance will be low.

The tantalum solid electrolytic capacitors of Examples 1 to 4 of the present invention and Comparative Examples 2 and 3 differ in the amount of epoxy resin applied.
Outside the range of 50 mg / cm ² , the ESR characteristics and the leakage current characteristics are increased, the number of short circuits after aging is increased, and the capacitance is low.

Further, in the tantalum solid electrolytic capacitor according to the sixth embodiment of the present invention, the contact resistance is reduced by previously irradiating the epoxy resin adhered to the portion of the anode lead wire to which the anode terminal is connected by laser irradiation, Examples 1 to 5
Compared with the tantalum solid electrolytic capacitor described above, the capacitance is higher, and the ESR characteristics and the leakage current characteristics can be improved.

[0055]

As described above, according to the present invention, a dielectric oxide film layer, a solid electrolyte layer, and a cathode layer are sequentially formed on the surface of an anode body, and a portion of the anode body where an anode lead-out line appears is thermally cured. This is a method for manufacturing a solid electrolytic capacitor that is fixed with a thermosetting resin to form a capacitor element.This method increases the fixing strength by fixing the anode lead wire with a thermosetting resin. Since it can withstand molding pressure, cracks in the dielectric oxide film layer and the exterior resin are eliminated, and a solid electrolytic capacitor having excellent leakage current and ESR characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a solid electrolytic capacitor according to Embodiments 1 and 2 of the present invention.

FIG. 2 is a sectional view showing a configuration of a conventional solid electrolytic capacitor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 anode lead wire 2 anode body 3 dielectric oxide film layer 4 solid electrolyte layer made of conductive polymer 5 cathode layer (carbon layer + silver paste layer) 6 thermosetting resin 7 capacitor element 8 anode terminal 9 conductive adhesive 10 Cathode terminal 11 Exterior resin

Claims (6)

[Claims] 1. A dielectric oxide film layer, a solid electrolyte layer, and a cathode layer are sequentially formed on the surface of an anode body obtained by sintering a molded body of tantalum powder in which an anode lead wire is embedded so that one end thereof is exposed. Then, a portion of the anode body where the anode lead-out line is exposed is fixed with a thermosetting resin to form a capacitor element, and then an anode terminal connected to the anode lead-out line of the capacitor element and a cathode connected to the cathode layer. A method for manufacturing a solid electrolytic capacitor, wherein at least a part of a terminal is covered with an insulating exterior resin so as to be exposed on an outer surface. 2. The method according to claim 1, wherein the solid electrolyte layer is a conductive polymer solid electrolyte layer formed by chemically oxidizing and polymerizing a heterocyclic monomer. 3. The method according to claim 1, wherein the thermosetting resin is an epoxy resin having a total content of Na and Cl ions of 10 ppm or less. 4. The method for producing a solid electrolytic capacitor according to claim 1, wherein the thermosetting resin having a viscosity of 100 to 500 poise is applied in a coating amount of 15 to 50 mg / cm ² and dried. 5. The method according to claim 1, wherein the connection of the anode lead to the anode terminal removes a part of the thermosetting resin attached to the anode lead, and connects the removed part of the anode lead to the anode terminal. 3. The method for manufacturing a solid electrolytic capacitor according to item 1. 6. The method for manufacturing a solid electrolytic capacitor according to claim 5, wherein a part of the thermosetting resin is removed by using laser irradiation.