JPH03227511A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To quickly obtain a capacitor excellent in a withstand voltage characteristic by performing lamination formation of a dielectric film, a manganese oxide material and a conductive high-polymer layer for a solid electrolyte on the metal foil surface. CONSTITUTION:A dielectric film 3 is formed on a metal foil (valve acting metal) 2 surface, further, a manganese oxide layer 4 is laminated to make a base material and immersed into electrolyte 8 of an electrolytic polymer treatment tank 9. The electrolyte 8 is electrolyte which contains a polymeric monomer and a supporting electrolytic layer and adjusted to pH 1 to 5. Then, the tip of an electrode 5 for an anode is made to contact with the surface of the manganese oxide layer 4. On the other hand, a cathode 7 is arranged on the bottom of the electrolytic polymer treatment layer 9 and voltage is impressed between the electrode for an anode and the cathode 7 to advance an electrolytic polymer reaction and to laminate and form a conductive high-polymer film 6 for a solid electrolyte. Thereby, a solid electrolytic capacitor having a full withstand voltage characteristic can be quickly manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer layer as a solid electrolyte.

BACKGROUND OF THE INVENTION In recent years, with the digitization of circuits in electrical equipment, etc., there has been a strong demand for capacitors used in circuits to have low impedance in a high frequency range, be small in size, and have a large capacity.

Conventionally, there are plastic film capacitors as high frequency capacitors. However, the first two types, plastic film capacitors and mica capacitors, were created in response to demands for large capacity and miniaturization, but are extremely expensive and have poor temperature characteristics.

In addition to the above capacitors, there are also aluminum dry electrolytic capacitors, aluminum solid electrolytic capacitors, and tantalum solid electrolytic capacitors.

In aluminum dry electrolytic capacitors, etched positive and negative electrode aluminum foils are wound up with a paper separator in between, and are impregnated with liquid electrolyte.

However, aluminum dry electrolytic capacitors have a major problem of characteristic deterioration due to electrolyte leakage, evaporation, and the like. In order to improve this point, the latter two q aluminum and tantalum solid electrolytic capacitors have a solid electrolyte.

For aluminum solid electrolytic capacitors and mental solid electrolytic capacitors, anode foil (metal foil) such as aluminum foil or tantalum foil, which has a dielectric film on its surface by anodizing or anodizing, is soaked in manganese nitrate solution. , 35
It is thermally decomposed in a high-temperature furnace at around 0℃, and a manganese dioxide layer (
A solid electrolyte consisting of a manganese oxide layer) is formed. Since these capacitors use a solid electrolyte, there is no problem of electrolyte loss at high temperatures or deterioration of characteristics due to electrolyte coagulation at low temperatures, and they have better frequency and temperature characteristics than capacitors using liquid electrolytes. Moreover, since the thickness of the oxide film serving as the dielectric can be made extremely thin, it is suitable for increasing the capacity.

As a solid electrolytic capacitor, in addition to the above, in place of the manganese dioxide layer, 7. 7.8. Those using solid electrolytes with organic semiconductors such as 8-tetracyanoquinodimethane (TCNQ) salt (Japanese Patent Application Laid-Open No. 17609), and conductive materials formed by electrolytically polymerizing polymerizable monomers such as pyrrole and furan. There is a method (Japanese Unexamined Patent Publication No. 60-244017) that uses a polymer layer as a solid electrolyte.

Problems to be Solved by the Invention However, in capacitors using a manganese dioxide layer as a solid electrolyte, damage to the dielectric film occurs due to multiple thermal decomposition treatments during the manufacturing process, and the specific resistance of the manganese dioxide layer is high, making it difficult to operate at high frequencies. There is a problem that it cannot be said that the loss is sufficiently small.

Capacitors that use an organic semiconductor such as TCNQ salt as a solid electrolyte have problems such as an increase in resistivity when applying the organic semiconductor and weak adhesion to the anode metal foil. do not have.

On the other hand, in capacitors that use an electrolytically polymerized conductive polymer layer (electrolytically polymerized conductive polymer membrane) as a solid electrolyte, the polymer layer is formed by an electrolytic polymerization reaction. In this case, the electrolytic polymerization reaction is called electrolytic oxidation of monomers. Because of the reaction process involved, it is extremely difficult to form a conductive polymer layer without damaging the dielectric film on the surface of the metal foil. It is possible to form an electropolymerized conductive polymer layer before forming a dielectric film, and then form a dielectric film through a chemical conversion reaction. It is of little practical use because of the deterioration of the adhesion between the molecular layer and the metal foil.

However, a dielectric film is first formed on the metal foil, and a manganese oxide layer is laminated on the conductive polymer layer film, and the anode electrode is brought into contact with the manganese oxide layer from the outside to cause polymerization. If a monomer is electrolytically polymerized and a conductive polymer layer is laminated on a manganese oxide layer, a solid electrolytic capacitor with good electrical characteristics can be obtained, which has a solid electrolyte made of the same polymer layer and a manganese oxide layer. The applicant has found that.

This solid electrolytic capacitor has excellent frequency characteristics, temperature characteristics, and life characteristics. However, there are problems in that the voltage resistance characteristics are insufficient and the manufacturing time is long. The reason why the withstand voltage characteristics are insufficient is that the electropolymerized conductive polymer film itself has a low ability to form an anode. The reason for the long manufacturing time is that it takes time to form a conductive polymer film.

In view of the above-mentioned circumstances, an object of this invention is to provide a method capable of rapidly manufacturing a solid electrolytic capacitor having sufficient withstand voltage characteristics while using an electrolytically polymerized conductive bacterial molecular layer as a solid electrolyte. shall be.

Means for Solving the Problems In order to solve the problems, in the method for manufacturing a solid electrolytic capacitor according to claims 1 to 4, in an electrolytic solution containing a polymerizable monomer and a supporting electrolyte and adjusted to I) H1 to 5. By electrolytic polymerization, a dielectric film is formed on the surface of the metal foil, and a manganese oxide layer is formed on the film.A conductive polymer layer for solid electrolyte is formed on the manganese oxide layer of the base material. are formed in layers.

In order to adjust the electrolytic solution to pH 1 to 5, for example, claim 2
As in the solid electrolytic capacitor manufacturing method described, sulfuric acid,
At least one of phosphoric acid, boric acid, carboxylic acid, nitric acid, and phenol should be used in an appropriate amount.

As the polymerizable monomer contained in the electrolytic solution, for example, as in the method for manufacturing a solid electrolytic capacitor according to claim 3,
Pyrrole, thiophene, furan At least one of these dielectrics is mentioned.

Examples of the supporting electrolyte contained in the electrolytic solution include at least one of monoisopropylnaphthalene sulfonate, diimpropylnaphthalene sulfonate, and triisopropylnaphthalene sulfonate.

Examples of the metal of the metal foil include at least one of aluminum and tantalum, as in the method for manufacturing a solid electrolytic capacitor according to claim 4.

Function: In this invention, electrolytic polymerization for forming a conductive polymer film is carried out using an electrolyte solution adjusted to a pH range of 1 to 5, so that a conductive polymer film for solid electrolyte having chemical formation properties can be formed quickly. . Therefore, a capacitor can be manufactured quickly, and the withstand voltage characteristics of the obtained capacitor are improved.

1) An electrolytic solution with a pH lower than H1' or an electrolytic solution with a pH higher than 5 cannot quickly form a conductive polymer film for a solid electrolyte that has chemical formation properties.

This is because if the electrolytic solution has a pH lower than 1, the dielectric film may dissolve. This is because, in the case of an electrolytic solution with a pH higher than 5, ``ions that impart chemical formation properties are insufficient, and the electrolytic solution becomes almost the same as one without additives.''

EXAMPLES Hereinafter, specific examples of the method for manufacturing a solid electrolytic capacitor according to the present invention will be described.

First, aluminum, tantalum foil, titanium foil,
Using a metal foil such as the metal alloy foil mentioned above, as shown in FIG. 1, a dielectric film 3 is formed on the surface of the metal foil (valve action all pole) 2 by anodizing or anodizing, Furthermore, a manganese oxide layer 4 is laminated on the same film 3 to make a base material,
The base material is immersed in the electrolytic solution 8 of the electrolytic polymerization treatment tank 9. The electrolytic solution 8 contains a polymerizable monomer and a supporting electrolyte and has a pH of 1 to 5.
It is a liquid adjusted to Then, the tip of the anode electrode 5 is brought into contact with the surface of the manganese oxide layer 4.

The base of this anode electrode 5 is made of metal, but its tip is covered with a conductive polymer film 16. bring into contact.

On the other hand, a cathode 7 is disposed at the bottom of the electrolytic polymerization treatment layer 9, and a voltage is applied between the anode electrode 5 and the cathode 7 to advance the electrolytic polymerization reaction, and as shown in FIG. A solid electrolytic capacitor is completed by laminating a conductive polymer film 6 for electrolyte, then laminating a graphite layer 10 made of carbon paste and a silver paste layer 11, and then attaching a cathode lead 3 with solder 12. . Note that 1 is an anode lead.

Of course, the method for manufacturing a solid electrolytic capacitor according to the present invention is not limited to using the compounds and processing steps exemplified above. It goes without saying that alternative compounds and treatment steps other than those exemplified above may be used.

I will explain in more detail.

Example 1 An aluminum etched foil (valve metal foil) with 8 vertical blades and 15 horizontal blades with an anode lead was heated at approximately 70°C for 40 minutes at an applied voltage of 10 using a 3% ammonium adipate aqueous solution.
A dielectric film was formed on the surface of the etched foil by anodic oxidation under the condition of 6V. Next, a manganese nitrate aqueous solution was applied onto the film and thermally decomposed at 200° C. for 30 minutes, and a manganese oxide layer was laminated to obtain a base material.

On the other hand, attach the tip of the stainless steel electrode base to pyrrole (0,
5M), IJ inglobilnaphthalene sulfone)
(0,15M) and water, sulfuric acid (H2SO4)
Immerse it in an electrolytic solution adjusted to pH 2 with a current of 2 mA at 60 mA.
The electrode substrate tip was covered with a conductive polymer film.

Then, in the electrolytic solution, the tip of the anode electrode was brought into contact with the surface of the manganese oxide layer 9, and a constant current of 2 mA was passed between the anode and the cathode to form a conductive polymer film. The time required to form this conductive polymer film was only 20 minutes.

Then, it was washed with water and then with ethanol, and then dried. After drying, carbon paste and silver paste were applied and the cathode lead was taken out to obtain a solid electrolytic capacitor.

The withstand voltage of each of the 10 solid electrolytic capacitors obtained was measured, and the average was 60.71V.

For comparison, an electrolytic solution with a pH of 8 was used without adjusting the pH.
A solid electrolytic capacitor was obtained in the same manner as in Example 1, except that the conductive polymer film was formed in separate steps. When the withstand voltage of each of the 10 capacitors obtained was measured, the average was 53. It was very inferior to the capacitor of I4V and Example 1.

Also, after aging at an applied voltage of 33 V, ■ initial capacity and loss (120 Hz) and ■ impedance (I
MHz) were measured. The results are as follows.

■ Initial capacity (120Hz) -2,37pF
■ Loss (120Hz)...14% ■ Impedance (I MHz)...13mΩ Example 2 The electrolyte was made of pyrrole (0.5M), triisopropylnaphthalene sulfonate (0.15M) and water. A solid electrolytic capacitor was obtained in the same manner as in Example 1, except that an electrolytic solution adjusted to pH 1 or pH 5 with sulfuric acid (H2SO4) was used.

In the case of pH 1, it took 24 minutes to form a conductive polymer film, and when the withstand voltage of each of the 10 capacitors obtained was measured, the average was 599V.

In the case of pH 5, it took 24 minutes to form a conductive polymer film, and when the withstand voltage of each of the 10 capacitors obtained was measured, the average was 57.61V.

For comparison, solid electrolytic capacitors were obtained in the same manner as in Example 2, except that an electrolytic solution adjusted to pH 6 or pH 8 was used.

In the case of pH 6, it took 27 minutes to form a conductive polymer film, and when the withstand voltage of each of the 10 capacitors obtained was measured, the average was 54.22V.

In the case of pH 8, it took 30 minutes to form a conductive polymer film, and when the withstand voltage of each of the 10 capacitors obtained was measured, the average was 53.14V.

From the above results, it is clear that when the pH exceeds 5, it takes time to form a conductive polymer film and the withstand voltage deteriorates significantly.

However, after aging at an applied voltage of 33 V, ■ initial capacity and loss (120 Hz) and ■ impedance (I
MHz) were measured. The results are as follows.

- In the case of pH 1 ■ Initial capacity (120Hz) ・= 2.35
pF■Loss (120Hz) ・-1.4%■
Impedance (I MHz)...l1mΩ=1
) For H5■ Initial capacity (120Hz) □-2,39p
F■ Loss (1201-Iz) ・A, 5%■
Impedance (IMHz)...12mΩ1]H
In case of 6■ Initial capacity (120Hz)...243μF
■ Peak loss (120Hz)...1.9%■
Impedance (I MHz)...14mΩ-I
) For H8■ Initial capacity (120 output) -...2.55μF ■Loss (120Hz) -2.0%■ Impedance (IMH7) ...16mΩ Example 3 The electrolyte was mixed with pyrrole (0.5M ), triimpropyl naphthalene sulfonate (0.15M) and water, and prepared in the same manner as in Example 1 except that an electrolytic solution prepared with p) (3,9) with sulfuric acid (H2S04) was used. I got it.

It took 24 minutes to form the conductive polymer film, and the withstand voltage of each of the 10 capacitors obtained was measured, and the average was 57.6.
It was 1V.

For comparison, I) Using an electrolytic solution with pH 8 without adjusting H, 3
Other than forming the conductive polymer film in 0 minutes,
A solid electrolytic capacitor was obtained in the same manner as in Example 3. The withstand voltage of each of the 10 capacitors obtained was measured and found to be an average of 53.14V.

In addition, after aging at an applied voltage of 33 V, ■ initial capacity and loss (1,20 Hz) and ■ impedance (
IMHz) were measured. The results are as follows.

■ Initial capacity (120Hz) -2,58pF
■Loss (120Hz)...1.6%■Impedance (IMHz)...12mΩExample 4 The electrolyte was mixed with pyrrole (0.5M), triimpropylnaphthalene sulfonate (0.15M) and water. A solid electrolytic capacitor was obtained in the same manner as in Example 1, except that an electrolytic solution adjusted to I)H2,57 with sulfuric acid (H2SO4) was used.

It took 27 minutes to form the conductive polymer film, and the withstand voltage of each of the 10 capacitors obtained was measured, and the average was 56.8.
It was 5V.

Also, after aging at an applied voltage of 33 V, ■ initial capacity and loss (120 Hz) and ■ impedance (I
MH2) was measured respectively. The results are as follows.

■ Initial capacity (120Hz)...235μ
F ■ Loss (120 Hz) ... 1.4% ■ Impedance (IMHz) ... 12 mΩ Example 5 After embossing, use a 10% phosphoric acid aqueous solution to approximately 90°
8 vertical x 10 horizontal units anodized under C135V conditions to form a dielectric film! ) A solid electrolytic capacitor was obtained in the same manner as in Example 1, except that the tantalum foil of I was used.

It took 17 minutes to form the conductive polymer film), and the withstand voltage of each of the 10 capacitors obtained was measured, and the average was 20.6.
It was v.

For comparison, without pH adjustment, using I) H8 electrolyte, 2
Other than forming a conductive polymer film over 3 minutes,
A solid electrolytic capacitor was obtained in the same manner as in Example 5. The withstand voltage of each of the 10 capacitors obtained was measured and found to be an average of 17.14V.

In addition, after aging at an applied voltage of 13 V, ■ initial capacity and loss (120 Hz) and ■ impedance (I
MHz) were measured. The results are as follows.

■ Initial capacity (120Hz)...1.03μ
F ■ Loss (120 Hz) -0.8% ■ Impedance (I MH2)...95 mΩ Example 6 An aluminum etched foil measuring 8 m II in length x 15 mm in width with an anode lead was used with a 3% ammonium adipate aqueous solution. A dielectric film was formed on the surface of the etched foil by anodic oxidation at about 70° C. for 40 minutes and an applied voltage of 67 V. Next, a manganese nitrate aqueous solution was applied onto the film and thermally decomposed at 200° C. for 30 minutes, and a manganese oxide layer was laminated to obtain a base material.

On the other hand, attach the tip of the stainless steel electrode base to pyrrole (0,
5M)-, To'J isoflovir naphthalene sulfonate (0,15M) and water, phosphoric acid (H3PO4
), the tip of the electrode base was covered with a conductive polymer film by immersing it in an electrolytic solution adjusted to H2 and passing a current of 2 mA for 60 seconds.

Then, in the electrolytic solution, the tip of the anode electrode was brought into contact with the surface of the manganese oxide layer, and a constant current of 2 mA was passed between the anode and the cathode to form a laminated conductive polymer film. The time required to form this conductive polymer film was only 24 minutes.

Thereafter, a solid electrolytic capacitor was obtained in the same manner as in Example 1.

When the withstand voltage of each of the 10 solid electrolytic capacitors obtained was measured, the average was 49. It was OV.

For comparison l) Using an electrolytic solution with pH 8 without adjusting H, 3
Other than forming the conductive polymer film in 0 minutes,
A solid electrolytic capacitor was obtained in the same manner as in Example 6. When the dielectric strength of each of the ten obtained capacitors was measured, the average voltage was 43.14V, which was very inferior to the capacitor of Example 6.

Still, after aging at an applied voltage of 20 V, ■ initial capacity and loss (120 Hz) and ■ impedance (I
MHz) f: Each was measured. The results are as follows.

■ Initial capacity (120Hz) ・5.45 pF
■Loss (120Hz)...1.1%■Impedance (IMHz)...L5mΩExample 7 As the electrolyte, pyrrole (0.5M), monoisoprobylnaphthalene sulfonate (0.15M) A solid electrolytic capacitor was obtained in the same manner as in Example 6, except that an electrolytic solution consisting of 100% and water and adjusted to pH 2 with phosphoric acid (H3PO4) was used.

The time required to form the conductive polymer film was 23 minutes, and the withstand voltage of each of the 10 capacitors obtained was measured.
The average voltage was 47.3V.

A solid electrolytic capacitor was obtained in the same manner as in Example 7, except that the pH was not adjusted and an electrolytic solution of pH 8 was used for comparison. When the withstand voltage of each of the 10 capacitors obtained was measured,
The average value is 40.52V, which is very inferior to the capacitor of Example 7.

Furthermore, after aging at an applied voltage of 20 V, (1) initial capacity and loss (120 Hz) and (2) impedance (IMHz) were measured, respectively. The results are as follows.

■ Initial capacity (120Hz),': -5,30μ
F ■ Loss (120 Hz) -1,0% ■ Impedance (I MHz)...16 mΩ Example 8 The electrolyte consisted of pyrrole (0.5 M), diisopropylnaphthalene sulfonate (0.15 M) and water. A solid electrolytic capacitor was obtained in the same manner as in Example 6, except that an electrolytic solution adjusted to pH 2 with phosphoric acid (H3PO4) was used.

The time required to form the conductive polymer film was 24 minutes, and the withstand voltage of each of the 10 solid electrolytic capacitors obtained was measured, and the average was 48.2V.

For comparison, a solid electrolytic capacitor was obtained in the same manner as in Example 8, except that the pH was not adjusted and an electrolytic solution of pH 8 was used. After measuring the withstand voltage of each of the 10 capacitors obtained,
The average value was 41.4V, which was very inferior to the capacitor of Example 8.

In addition, after aging at an applied voltage of 20 V, ■ initial capacity and loss (120 Hz) and ■ impedance (I
MHz) were measured. The results are as follows.

■ Initial capacity (120Hz) -5, 4, 6p
F ■ Loss (120 Hz) = 4.2% ■ Impedance (IMHz) ... 15 mΩ The solid electrolytic capacitor of the example obtained in this way has excellent electrical characteristics as seen from the above practical data. are doing. In addition, it has been confirmed that the capacitance change over time and LC characteristics are good, and the temperature change of each characteristic such as capacity is also good.

Effects of the Invention As described above, in the method for manufacturing a solid electrolytic capacitor according to claims 1 to 4, since the electrolytic solution is adjusted to pH 1 to 5, it is possible to quickly obtain a capacitor with excellent withstand voltage characteristics. Moreover, since the obtained capacitor includes a conductive polymer film for solid electrolyte laminated on a manganese oxide layer, it has excellent frequency characteristics, temperature characteristics, and life characteristics.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing the formation of a conductive polymer layer for a solid electrolyte according to an example of the method for manufacturing a solid electrolytic capacitor according to the present invention, and FIG. It is a schematic sectional view of hail. ■... Anode lead, 2... Metal foil, 3... Dielectric film, 4... Manganese oxide layer, 5... Anode, 6...
・Conductive polymer membrane, 7... land bridge, 8. electrolyte solution, 10.
...Graphite layer, 11... Silver paste layer, 13.
・・Anode.

Claims (4)

[Claims] (1) A dielectric film is formed on the surface of the metal foil by electrolytic polymerization in an electrolytic solution containing a polymerizable monomer and a supporting electrolyte and adjusted to pH 1 to 5, and a manganese oxide layer is formed on the film. A method for manufacturing a solid electrolytic capacitor, comprising laminating a conductive polymer layer for a solid electrolyte on the manganese oxide layer of the base material. (2) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the pH of the electrolytic solution is adjusted by including an appropriate amount of at least one of sulfuric acid, phosphoric acid, boric acid, carboxylic acid, nitric acid, and phenol. (3) The method for manufacturing a solid electrolytic capacitor according to claim 1 or 2, wherein the polymerizable monomer is at least one of pyrrole, thiophene, and a dielectric thereof. (4) The method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 3, wherein the metal of the metal foil is at least one of aluminum and tantalum.