JP5164325B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

The present invention includes a capacitor element formed by winding an anode having an oxide film formed on a surface of a metal having a valve action, a cathode provided with a metal having a valve action, and a separator provided between the two electrodes. A structure in which a solid electrolyte is interposed between the two electrodes, an anode lead tab terminal having an oxide film formed on the surface thereof is fixed to the anode, and a cathode lead tab terminal is fixed to the cathode. The present invention relates to a method for manufacturing a solid electrolytic capacitor.

  Electrolytic capacitors using a metal having a valve action such as tantalum or aluminum are widely used because they are small and can obtain a large capacity. Particularly, among electrolytic capacitors, polypyrrole-based, polythiophene-based, A solid electrolytic capacitor using a conductive polymer such as polyaniline or a TCNQ complex salt as an electrolyte has attracted attention.

Here, the solid electrolytic capacitor is manufactured as follows (see Patent Document 1 below).
First, an anode lead tab terminal subjected to chemical conversion treatment on an anode made of an aluminum foil subjected to etching treatment and chemical conversion treatment, and a cathode lead tab terminal fixed to the cathode, respectively, and then the anode and the cathode are connected via a separator paper. Then, the capacitor element is wound up into a cylindrical shape, and the capacitor element is cut and heat-treated. Next, after immersing the capacitor element in a solution containing an oxidizing agent and a monomer, a conductive polymer layer (solid electrolyte layer) is formed between both electrodes of the capacitor element by thermal polymerization. Next, after the capacitor element is housed and fixed in the aluminum case, the opening of the aluminum case is sealed, and further an aging process is performed. Finally, a seat plate is inserted into the curled surface of the capacitor, and the lead wire of the capacitor is pressed and bent to produce an electrode terminal, thereby completing the solid electrolytic capacitor.

JP-A-6-310381

  Here, in the above-mentioned solid electrolytic capacitors, the demand and demand for high voltage products are increasing in the market, but solid electrolytic capacitors are self-healing of leakage current (LC) compared to electrolytic electrolytic capacitors. There is a problem that the function is poor (inferior). In order to increase the breakdown voltage of such a solid electrolytic capacitor, it is necessary to increase the withstand voltage of the dielectric oxide film on the anode foil in advance (in other words, increase the chemical conversion voltage of the anode foil). Furthermore, for the same reason, it is necessary to perform chemical conversion treatment again on the cut portion of the anode foil during the manufacturing process. The formation of the cut end is a process unique to the solid electrolytic capacitor, and is not limited to the case of increasing the breakdown voltage.

  Usually, the chemical conversion voltage for the cut formation performed in the manufacturing process is the same voltage as the chemical conversion voltage for the anode foil. However, when the chemical conversion voltage for the cut formation exceeds 200 V (particularly 230 V), the normal anode When the lead tab terminal for use (chemical conversion voltage of about 160 V) was used, the cut formation was not stable, and many corrosions of the welded portion of the anode lead tab terminal were generated. As a result, there has been a problem that the LC characteristics of the solid electrolytic capacitor are not stabilized.

Therefore, the present invention has been proposed in order to solve the above-described problems, and its purpose is to stabilize the cut formation and stabilize the LC characteristics by suppressing the corrosion of the lead tab terminal weld for the anode. Another object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor that can be made to operate.

To achieve the above object, the invention according to claim 1 of the present invention, chemical conversion treatment with, thereby forming an oxide film on the surface of the anode made of a metal having a valve action, oxidation on the surface of the anode lead tab terminal A first step of forming a coating; a second step of fixing the anode lead tab terminal to the anode; and a cathode lead tab terminal to a cathode provided with a metal having a valve action; the anode; and the cathode; A third step of winding a separator disposed between the two electrodes to produce a capacitor element; a fourth step of forming the capacitor element and forming an oxide film on the end face of the anode; and the capacitor a fifth step of including the solid electrolyte element, the manufacturing method of a solid electrolytic capacitor rated voltage of more than 50V with a first step Wherein the ratio of the voltage conversion treatment to form a surface oxide film of the anode lead tab terminal for chemical conversion voltage to form an oxide film on the surface of the anode is restricted to 75% or more.

  The reason why the cut formation is not stabilized and that the lead tab terminal weld for anode corrodes is that the chemical treatment voltage of the lead tab terminal for anode is too low with respect to the chemical conversion voltage of cut formation. The present inventors have found out. Usually, the chemical conversion voltage of the lead tab terminal for anode used in the solid electrolytic capacitor is 160V. Therefore, if a voltage exceeding 200V (particularly 230V) is applied at the time of the cut formation, the lead tab terminal for the anode itself is greatly formed. The formation is not stabilized and a large current flows through the lead tab terminal for anode due to the formation, and the welded portion of the lead tab terminal for anode corrodes.

  Therefore, in order to stabilize the cut formation (to increase the breakdown voltage of the solid electrolytic capacitor), the lead tab terminal for the anode is subjected to chemical conversion treatment at a voltage of 75% or more of the chemical conversion treatment voltage for anodization. The ratio of the thickness of the oxide film in the lead tab terminal for anode to the thickness of the oxide film is regulated to be 75% or more. This makes it possible to stabilize the cut formation even when the cut formation voltage (set to be equal to the anode chemical conversion voltage) is high, and to make the lead tab terminal for the anode large. Since no current flows, corrosion of the welded portion of the anode lead tab terminal can be suppressed.

In addition, it is desirable that the ratio of the chemical conversion voltage at the time of producing the lead tab terminal for anode to the chemical conversion voltage at the time of producing the anode is less than 100%. This is because when the ratio of the chemical conversion voltage at the time of preparation of the lead tab terminal for anode to the chemical conversion voltage at the time of preparation of the anode becomes 100% or more, the chemical conversion power at the preparation of the oxide film of the lead tab terminal for anode becomes too large, This is because the thickness of the oxide film increases.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, in the fifth step, the capacitor element is impregnated with a monomer and then thermally polymerized to cause the capacitor element to contain a solid electrolyte. .
With such a method, a solid electrolytic capacitor can be easily manufactured. .

According to a third aspect of the present invention, in the first aspect of the present invention, the chemical conversion voltage at the time of producing the anode is 300 V or higher, and the chemical conversion voltage at the time of preparing the lead tab terminal for the anode is 225 V or higher.
With such a method, a high voltage electrolytic capacitor can be easily manufactured.

  According to the present invention, there is an excellent effect that the LC characteristics of the solid electrolytic capacitor can be stabilized by stabilizing the cut formation and suppressing the corrosion of the lead tab terminal weld for anode.

  Hereinafter, the present invention will be described in more detail. However, the present invention is not limited to the following best modes, and can be appropriately modified and implemented without departing from the scope of the present invention.

FIG. 1 is a perspective view of a capacitor element used in a solid electrolytic capacitor as an example of the present invention, and FIG. 2 is a cross-sectional view of the solid electrolytic capacitor as an example of the present invention.
As shown in FIG. 2, the capacitor element 1 is disposed in the aluminum case 9, and a sealing rubber packing 10 is inserted on the capacitor element 1. Moreover, the opening part of the aluminum case 9 is sealed by curling with a lateral diaphragm, and a plastic seat plate 11 is inserted on the sealing part. On the seat plate 11, electrode terminals formed by pressing and bending a cathode lead wire 8 and an anode lead wire 7, which will be described later, electrically connected to the cathode 2 and the anode 3, respectively. 12 is provided.

  On the other hand, as shown in FIG. 1, the capacitor element 1 includes an anode 3 having an oxide film formed on the surface of an aluminum foil having an uneven surface, a cathode 2 made of an aluminum foil having an uneven surface, and both of these electrodes. And a paper separator 4 provided between two and three. The bipolar electrodes 2 and 3 and the separator 4 are wound in a roll shape to form a cylindrical capacitor element 1. A fixing tape 5 is attached to the winding end of the capacitor element 1. Has been. A polythiophene-based conductive polymer layer is formed between the two electrodes 2 and 3.

  Here, in FIG. 1, 6 is an anode lead tab terminal and 7 is an anode lead wire. As shown in FIG. 3, the specific structure is composed of a boss portion 61, a rib portion 62, and a flat portion 63. The anode lead wire terminal 7 is welded to the aluminum anode lead tab terminal 6. In FIG. 3, reference numeral 70 denotes a welded portion. In FIG. 1, 14 is a cathode lead tab terminal, and 8 is a cathode lead wire. The specific structure is the same as the anode lead tab terminal 6 and anode lead wire 7 shown in FIG. Yes. However, the cathode lead tab terminal 7 is different from the anode lead tab terminal 6 in that the chemical conversion treatment is not performed.

A solid electrolytic capacitor having the above structure was produced as follows.
First, the strip-shaped aluminum foil cut out from the aluminum sheet is etched. The etching process is performed in order to roughen the surface of the aluminum foil, increase the surface area, and increase the capacitance. Next, the aluminum foil was immersed in the chemical conversion liquid, and a voltage of 250 V was applied (the chemical conversion treatment voltage was set to 250 V) to oxidize aluminum to form an aluminum oxide film (chemical conversion film). Thereby, the anode 3 is produced. In addition, as a chemical conversion liquid, solutions, such as a phosphate, a borate, an adipate, are known, However, You may use the solution of other acid salts.
Here, the thickness of the aluminum oxide film is 14 × 10 ⁻¹⁰ m per 1 V of the chemical conversion voltage (applied voltage), and is proportional to the chemical conversion voltage. Therefore, the thickness of the aluminum oxide film formed on the anode 3 is as follows. Is expressed by the following equation (1).
250 × 14 × 10 ⁻¹⁰ m = 3.5 × 10 ⁻⁷ m (1)

In parallel with the positive electrode preparation step, an aluminum oxide film (chemical conversion film) was formed by applying a voltage to the aluminum anode lead tab terminal 6 (chemical conversion treatment) under the following conditions. However, since the applied voltage in this case was 200 V, the thickness of the aluminum oxide film formed on the anode lead tab terminal 6 is expressed by the following equation (2).
200 × 14 × 10 ⁻¹⁰ m = 2.8 × 10 ⁻⁷ m (2)

However, part of the anode lead tab terminal 6 (portion on the left side of the two-dot chain line in FIG. 3) 64 comes into contact with the chemical conversion solution at the time of cut formation described later, so that it is the same as the chemical conversion voltage of the anode 3. It is formed again at the time of cut formation performed at a voltage (250 V). As a result, the thickness of the aluminum oxide film in the part 64 of the lead tab terminal 6 for anode is 3.5 × 10 ⁻⁷ m, similar to the thickness of the aluminum oxide film formed on the anode 3.
Next, the anode lead tab terminal 6 was fixed to the anode 3 by spotting, while the cathode lead tab terminal 14 was fixed to the cathode 2 made of aluminum foil by spotting.

  Thereafter, the anode 3 and the cathode 2 were wound in a roll shape through a separator 4 as an insulator, and the winding end was stopped with a tape 5 to produce a capacitor element 1. Here, as described above, since the anode 3 is cut out from the aluminum sheet, an aluminum oxide film (dielectric oxide film) is not formed on the end face of the anode 3. Therefore, cut formation of the capacitor element 1 was performed at a printing voltage of 250 V (a voltage similar to the chemical conversion voltage of the anode 3), and an aluminum oxide film was formed on the end face of the anode. Thereafter, the capacitor element 1 was heat-treated at 280 ° C. to stabilize the characteristics of the aluminum oxide film.

  Next, the capacitor element 1 is immersed in a butyl alcohol solution containing 3,4-ethylenedioxythiophene as a monomer and ferric p-toluenesulfonate as an oxidant solution, and then subjected to thermal polymerization to form both electrodes 2 , 3 to form a conductive polymer layer to complete the capacitor element 1.

  After that, as shown in FIG. 2, the capacitor element 1 manufactured as described above is housed in an aluminum case 9, and a sealing rubber packing 10 is inserted into the aluminum case 9 on the capacitor element 1. After fixing, the opening of the aluminum case 9 was sealed by applying a lateral stop and curling. Finally, after performing the aging process, the plastic seat plate 11 is inserted into the curled surface of the capacitor, and further, the lead wires 7 and 8 of the capacitor are pressed and bent to form the electrode terminals 12. Thus, a solid electrolytic capacitor was produced.

  The solid electrolytic capacitor thus fabricated has a rated voltage of 50 V, and the outer dimensions of the aluminum case 9 are 10.0 mm in diameter and 8.0 mm in height.

Example 1
A solid electrolytic capacitor was produced in the same manner as in the best mode for carrying out the invention.
The solid electrolytic capacitor thus produced is hereinafter referred to as the present invention capacitor A1.

(Example 2)
The applied voltage when the chemical conversion treatment is performed on the anode 3 (including the cut end of the anode, which is the same in the following Example 3 and Comparative Examples 1 to 3) and the lead tab terminal 6 for the anode is 400 V, respectively. A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the voltage was set to 300V.
The solid electrolytic capacitor thus produced is hereinafter referred to as the present invention capacitor A2.

The thickness of the aluminum oxide film formed on the anode 3 is expressed by the following formula (3), and the thickness of the aluminum oxide film formed on the anode lead tab terminal 6 is expressed by the following formula (4).
400 × 14 × 10 ⁻¹⁰ m = 5.6 × 10 ⁻⁷ m (3)
300 × 14 × 10 ⁻¹⁰ m = 4.2 × 10 ⁻⁷ m (4)

(Example 3)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the applied voltage when the chemical conversion treatment was applied to the anode 3 and the lead tab terminal 6 for anode was 450 V and 400 V, respectively.
The solid electrolytic capacitor thus produced is hereinafter referred to as the present invention capacitor A3.

The thickness of the aluminum oxide film formed on the anode 3 is expressed by the following formula (5), and the thickness of the aluminum oxide film formed on the anode lead tab terminal 6 is expressed by the following formula (6).
450 × 14 × 10 ⁻¹⁰ m = 6.3 × 10 ⁻⁷ m (5)
400 × 14 × 10 ⁻¹⁰ m = 5.6 × 10 ⁻⁷ m (6)

(Comparative Example 1)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the applied voltages when the chemical conversion treatment was performed on the anode 3 and the anode lead tab terminal 6 were 250 V and 160 V, respectively.
The solid electrolytic capacitor thus manufactured is hereinafter referred to as a comparative capacitor X1.

The thickness of the aluminum oxide film formed on the anode 3 is expressed by the following formula (7), and the thickness of the aluminum oxide film formed on the anode lead tab terminal 6 is expressed by the following formula (8).
250 × 14 × 10 ⁻¹⁰ m = 3.5 × 10 ⁻⁷ m (7)
160 × 14 × 10 ⁻¹⁰ m = 2.24 × 10 ⁻⁷ m (8)

(Comparative Example 2)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the applied voltage when the chemical conversion treatment was applied to the anode 3 and the lead tab terminal 6 for anode was 400 V and 200 V, respectively.
The solid electrolytic capacitor thus fabricated is hereinafter referred to as a comparative capacitor X2.

The thickness of the aluminum oxide film formed on the anode 3 is expressed by the following formula (9), and the thickness of the aluminum oxide film formed on the anode lead tab terminal 6 is expressed by the following formula (10).
400 × 14 × 10 ⁻¹⁰ m = 5.6 × 10 ⁻⁷ m (9)
200 × 14 × 10 ⁻¹⁰ m = 2.8 × 10 ⁻⁷ m (10)

(Comparative Example 3)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the applied voltage when the chemical conversion treatment was performed on the anode 3 and the lead tab terminal 6 for anode was 450 V and 300 V, respectively.
The solid electrolytic capacitor thus manufactured is hereinafter referred to as a comparative capacitor X3.

The thickness of the aluminum oxide film formed on the anode 3 is expressed by the following equation (11), and the thickness of the aluminum oxide film formed on the anode lead tab terminal 6 is expressed by the following equation (12).
450 × 14 × 10 ⁻¹⁰ m = 6.3 × 10 ⁻⁷ m (11)
300 × 14 × 10 ⁻¹⁰ m = 4.2 × 10 ⁻⁷ m (12)

(Experiment 1)
Table 1 shows the results of the corrosion occurrence rate in the cut formation process in the capacitors A1 to A3 of the present invention and the comparative capacitors X1 to X3. The number of samples was 20 capacitors.

  As is apparent from Table 1 above, it can be seen that many corrosions have occurred in the comparative capacitors X1 to X3, whereas no corrosion has occurred in the capacitors A1 to A3 of the present invention. Therefore, it is necessary to regulate the ratio of the thickness of the aluminum oxide film in the lead tab terminal for the anode (the chemical conversion voltage in the lead tab terminal for the anode to the chemical conversion voltage in the anode) to the thickness of the aluminum oxide film in the anode to 75% or more. I understand that there is.

(Experiment 2)
The initial LC characteristics of the capacitors A1 to A3 of the present invention and the comparative capacitors X1 to X3 were examined, and the results are shown in Table 2. The number of samples was 20 capacitors, and Table 2 shows the average values.

  As is apparent from Table 2 above, it is recognized that the initial LC characteristics of the capacitors A1 to A3 of the present invention are remarkably improved as compared with the comparative capacitors X1 to X3. Therefore, it is necessary to regulate the ratio of the thickness of the aluminum oxide film in the lead tab terminal for the anode (the chemical conversion voltage in the lead tab terminal for the anode to the chemical conversion voltage in the anode) to the thickness of the aluminum oxide film in the anode to 75% or more. I understand that there is.

[Other matters]
(1) In the above embodiment, an etched aluminum foil is used as the base material of the electrode, but it goes without saying that a plain (unetched) aluminum foil may be used.
(2) A polythiophene-based conductive polymer is used as the solid electrolyte. However, the present invention is not limited to this, and a polypyrrole-based or polyaniline-based conductive polymer or a TCNQ complex salt may be used. is there.

(3) The chemical conversion treatment of the lead tab terminal for anode may be performed before or after the production of the lead tab terminal for anode. That is, when manufacturing a lead tab terminal for an anode, it is formed by punching a metal sheet made of aluminum or the like. However, the chemical conversion treatment may be performed before punching or the chemical conversion treatment may be performed after punching. good. In the above-described embodiment, the chemical conversion treatment is performed only on the lead tab terminal for anode, but it is needless to say that the chemical conversion treatment may be performed on the lead tab terminal for cathode. If the lead tab terminal for cathode that has been subjected to chemical conversion treatment is used in this way, both lead tab terminals can be used in common, so that productivity can be improved.

(4) The metal having a valve action is not limited to the above aluminum, but may be tantalum, niobium or the like.
(5) Although the chemical conversion treatment of the anode 3 and the cut end of the anode is not limited to the same voltage, in order to stabilize the cut cut formation and suppress corrosion of the lead tab terminal welded portion for the anode, both chemical conversion treatments are performed. It is desirable to carry out at the same voltage.

  The present invention can be used, for example, as an electronic component for surface mounting on a printed wiring board of an electronic device such as a mobile phone, a notebook computer, or a PDA.

It is a capacitor | condenser element perspective view used for the solid electrolytic capacitor which is an example of this invention. It is sectional drawing of the solid electrolytic capacitor which is an example of this invention. It is a top view of the lead tab terminal for anodes of the solid electrolytic capacitor which is an example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Cathode 3 Anode 6 Lead tab terminal for anode 7 Lead wire 14 Lead tab terminal for cathode 70 Welded part

Claims (3)

A first step of forming an oxide film on the surface of the anode made of a metal having a valve action by chemical conversion;
A second step of forming an oxide film on the surface of the lead tab terminal for anode by chemical conversion;
A third step of fixing the anode lead tab terminal to the anode and the cathode lead tab terminal to the cathode; and
A fourth step in which a capacitor element is manufactured by winding the anode, the cathode, and a separator disposed between the two electrodes;
A fifth step of performing cut formation of the capacitor element and forming an oxide film on the cut portion of the anode;
A sixth step of including a solid electrolyte in the capacitor element;
In a method for manufacturing a solid electrolytic capacitor having a rated voltage of 50 V or more , comprising:
The voltage of the chemical conversion treatment in the second step is regulated to 75% or more with respect to the voltage of chemical conversion treatment in the first step, and is regulated to 75% or more with respect to the voltage of cut formation in the fifth step. A method for producing a solid electrolytic capacitor, comprising:   The method for producing a solid electrolytic capacitor according to claim 1, wherein, in the sixth step, the capacitor element is impregnated with a monomer and then subjected to thermal polymerization, thereby including the solid electrolyte in the capacitor element. The manufacturing method of the solid electrolytic capacitor of Claim 1 or 2 whose voltage of the chemical conversion treatment in the said 1st step is 300V or more, and whose voltage of the chemical conversion treatment in the said 2nd step is 225V or more.