JPH04307918A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide a manufacturing method to get a capacitor excellent in frequency characteristics, temperature characteristics, etc., by forming a conductive base layer on the surface of the valve metal which has a dielectric film where a dielectric nonformation part is provided at one part of the surface or by such a like method thereby forming an electrolytically polymerized high polymer film surely and easily on the surface of the valve metal being insulated by a dielectric film. CONSTITUTION:Using a valve metal which has a dielectric film where a dielectric film nonformation part is provided at one part of the surface, a conductive base layer is made on the surface of the valve metal. Next, with the dielectric film nonformation part provided at one part as the starting point of polymerization, a conductive electrically polymerized polymer film is made through the conductive base layer, and then the section which includes the starting part of polymerization is removed. For example, the shape of the valve metal is made the one which has at least one place of projection 2, and a dielectric film nonformation part is provided inside the projection 2. Moreover, the conductive base layer is made a manganese oxide layer, and the conductive electrolytically polymerized polymer is one which includes a pyrrole ring or a thiophene ring as a repeating unit.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a solid electrolytic capacitor with excellent capacitor characteristics, particularly frequency characteristics, and reliability characteristics under high temperature and high humidity conditions, and more particularly to a method for manufacturing a solid electrolytic capacitor using a conductive polymer as a solid electrolyte. It is something.

0002

[Background Art] In recent years, with the digitalization of electrical equipment,
Capacitors are also required to be small, large in capacity, and have low impedance in the high frequency range. Conventionally, capacitors used in the high frequency range include plastic capacitors, mica capacitors, and multilayer ceramic capacitors, but these capacitors have large shapes and are difficult to increase in capacity.

On the other hand, examples of large capacity capacitors include electrolytic capacitors such as aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. In these capacitors, the oxide film that serves as the dielectric material is extremely thin, making it possible to achieve large capacitance, but the oxide film is easily damaged, so it is necessary to provide an electrolyte between the cathode and the cathode to repair it. be.

[0004] In an aluminum dry capacitor, etched anode and cathode aluminum foils are wound up with a separator in between, and the separator is impregnated with a liquid electrolyte. This liquid electrolyte has ionic conductivity and high specific resistance, so it has large losses and extremely poor impedance frequency characteristics and temperature characteristics.Furthermore, leakage and evaporation are unavoidable, resulting in a decrease in capacity and loss over time. There was a problem with the increase.

Furthermore, tantalum solid electrolytic capacitors use manganese dioxide as an electrolyte, which improves the problems of temperature characteristics, capacitance, loss, and other changes over time; however, since manganese dioxide has a relatively high resistivity, losses and impedance The frequency characteristics of capacitors are inferior to those of multilayer ceramic capacitors or film capacitors.

Furthermore, in recent years, electrolytic oxidation polymerization of heterocyclic monomers such as pyrrole and thiophene using a supporting electrolyte has improved the frequency characteristics and frequency characteristics of a highly conductive polymer containing the anion of the supporting electrolyte as a dopant. Solid electrolytic capacitors with excellent temperature characteristics have been proposed (JP-A-60-37114, JP-A-60
-244017).

[0007]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, since the surface of the valve metal, which becomes the anode of the capacitor, is covered with a dielectric film, it is difficult to form electrolytically polymerized polymers, which become the electrolyte, in that state. The only way to find a starting point was to rely on defects in the dielectric film that occur with uncertain frequency. Furthermore, with this method, it is extremely difficult to reliably grow an electrolytically polymerized polymer film over the entire surface of the capacitor anode, which is insulated from its starting point.

Furthermore, it may be possible to form a dielectric film on the valve metal surface by anodization after forming the conductive polymer film that will serve as the electrolyte, but this method may cause problems such as deterioration or peeling of the conductive polymer film. A problem arises. For the reasons mentioned above, it has been difficult to stably obtain a solid electrolytic capacitor with excellent frequency characteristics and temperature characteristics using an electrolytically polymerized conductive polymer as an electrolyte.

The present invention solves the above-mentioned problems of the prior art by reliably and easily forming an electropolymerized polymer film on the surface of a valve metal insulated by a dielectric film, thereby improving frequency characteristics, temperature characteristics, etc. The purpose of the present invention is to provide a method for manufacturing a solid electrolytic capacitor that realizes an excellent solid electrolytic capacitor.

0010

[Means for Solving the Problems] In order to achieve this object, the present invention uses a valve metal having a dielectric film in which a part of the surface is not formed with the dielectric film, and provides a conductive surface on the surface of the valve metal. A conductive electropolymerized polymer layer is formed on the surface of the valve metal having a dielectric film through the conductive base layer, using the portion without a dielectric film formed on the part as a polymerization initiation point. A solid electrolytic capacitor is obtained by forming and then removing the portion containing the polymerization initiation point.

[0011] Although the part without a dielectric film, which serves as a polymerization initiation point, may be provided at any part, it is preferable to use a valve metal having a shape having at least one protrusion, and to provide a part without a dielectric film in the protrusion. Providing a forming part is desirable from the viewpoint of convenience in removing the polymerization initiation site. The polymerization initiation point only needs to be at least one location, and can be provided at multiple locations in order to shorten the polymer film coating time. The same applies to the protrusions. A part without a dielectric film is formed by covering the part during chemical formation, or after forming a dielectric film on the entire surface.
It can also be formed by removing it by suitable means.

[0012] As the valve metal, aluminum, tantalum,
Niobium, titanium, etc. can be used, but aluminum or tantalum is preferably used.

Manganese oxide is preferable as the conductive underlayer, and it can be formed by any method, but preferably the dielectric film is formed in a solution containing a divalent ion of manganese. It is formed by pyrolysis after impregnation with metal. Any manganese salt can be used as long as it is soluble in a solvent, and examples of such manganese salts include manganese nitrate, manganese acetate, manganese octylate, manganese naphthenate, and the like.

[0014] The electrolytically polymerized polymer can be of any type as long as it has a desired electrical conductivity, but it contains at least one type selected from pyrrole or its derivative monomer or thiophene or its derivative monomer as a repeating unit. Something is desired. The electrolytically polymerized polymer as described above can be easily obtained by providing an anode and a cathode in a solution containing at least the monomer and supporting electrolyte as described above and applying a voltage.

As the supporting electrolyte, any material can be used as long as it is polymerizable and the anion acts as a dopant that provides the desired electrical conductivity, but sulfonate is preferably used, and allyl sulfonate is more preferably used. be done. It is sufficient that at least one sulfone group is contained per molecule, and in addition to the sulfone group, those having other substituents such as an alkyl group can also be used.

Any method can be used to remove the polymerization initiation point as long as the anode valve metal layer and the conductive polymer electrolyte layer do not come into contact across the gap between the dielectric layers in the cross section. In addition to cutting with a cutter, other methods such as tearing may also be used.

[0017]

[Function] The manufacturing method of the present invention uses a valve metal having a dielectric film in which a part of the surface is not formed with a dielectric film, and forms a conductive base layer on the surface of the valve metal. Since the valve metal material and the conductive base layer form an electrically conductive part in the part without a dielectric film formed on the part, the electropolymerized polymer is applied to the entire surface from the conductive part using the valve metal as an anode. It can be grown and coated. Since the portion without the dielectric film, which was the starting point of polymerization, is then removed, a solid electrolytic capacitor with low leakage current can be obtained.

[0018] Note that the portion without the dielectric film can be removed at any stage after the electrolytically polymerized film is formed. For example, the portion without a dielectric film can be removed immediately after forming the electropolymerized polymer, but in this case, the cathode constituent material such as colloidal graphite or silver paint layer must be installed excluding the removed cross section. For example, if it is removed after arranging the cathode structure as described above, the capacitor can be completed by sealing the exterior with an appropriate means in that state.

[0019]

Embodiments (Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a capacitor electrode foil portion of a solid electrolytic capacitor according to an embodiment of the present invention. In FIG. 1, 1 is a capacitor electrode foil main body portion, 2 is a capacitor electrode foil protrusion, 3 is a through hole provided for removing a dielectric film, and 4 is an anode lead.

FIG. 2 is a schematic partial cross-sectional view of electrolytic polymerization, which is a method of manufacturing a solid electrolytic capacitor in one embodiment of the present invention. In FIG. 2, 6 is a capacitor electrode foil, 7 is an anode for electrolytic polymerization, 8 is a cathode for electrolytic polymerization, 9 is an electrolytic solution for polymerization, and 10 is an electrolytic polymerization tank.

[0022] As shown in Fig. 1, the width is 1 mm and the length is 1.5 m.
Capacitor electrode foil body part 1 made of aluminum etched foil with body part dimensions of 4 x 6 mm and having projections 2 of m.
Attach the aluminum anode lead 4 to the
The surface was coated with a 3% ammonium adipate aqueous solution for approx.
After a dielectric film was formed by anodic oxidation by applying 50 V at 0° C., a 0.5 mm through hole 3 was provided in the protrusion 2 and the dielectric film was removed. Thereafter, it was immersed in a 30% manganese nitrate aqueous solution and further heated at 250° C. for 10 minutes to adhere pyrolyzed manganese oxide to the surface, thereby producing a capacitor electrode foil 6.

An anode 7 for electrolytic polymerization was connected to this capacitor electrode foil 6, and pyrrole monomer (0.2M), sodium n-butylnaphthalenesulfonate (0.05M),
When immersed in an electrolytic solution 9 for polymerization consisting of water and applying a voltage of 3V between the anode 7 and the cathode 8 for electrolytic polymerization provided apart from each other, an electrolytic polymer membrane (not shown) consisting of polypyrrole was completely covered after 45 minutes. was formed. After washing the aluminum electrode foil covered with this electrolytic polymer film with water and drying it, colloidal graphite and silver paint are applied to the electrolytic polymer film, the protrusion 2 is broken off, and a cathode lead is attached. , 10 capacitors are sealed with epoxy resin.
Completed.

For this capacitor, after aging at 16.2V, the leakage current (when 13V is applied for 2 minutes) and the average values of capacitance and loss at 120Hz are 0.055 μA, 4.56 μF, and 1.1%, respectively. there were.

For comparison, an attempt was made to fabricate a capacitor in the same manner as in Example 1 except that a through hole was formed in the protrusion and the dielectric film was not removed, but the electropolymerized film did not grow even after 120 minutes. However, I was unable to obtain a capacitor.

As is clear from this, the manufacturing method according to the present example has the advantage that it is possible to easily obtain a solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics using an electrolytically polymerized polymer as an electrolyte. Excellent effects can be obtained.

As described above, according to this embodiment, a valve metal having a dielectric film with a portion without a dielectric film formed on a part of the surface is used, and a conductive material made of manganese oxide is provided on the surface of the valve metal. A base layer is formed, and a conductive electrolytically polymerized polymer layer is formed via the manganese oxide layer using the portion without a dielectric film formed thereon as a polymerization initiation point, and then the conductive electrolytically polymerized polymer layer is formed including the polymerization initiation point. By removing the portion, a solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics can be obtained.

Note that any shape of the protrusion can be used as long as a polymer film can substantially grow from a polymerization initiation point provided in a part of the protrusion. Further, as long as the portion substantially including the polymerization initiation point can be removed, the polymerization initiation point may be provided in the main body portion without necessarily providing the protrusion.

(Embodiment 2) A second embodiment of the present invention will be described below.

Ten capacitors were completed in the same manner as in Example 1, except that the protrusions including the polymerization initiation point were removed after the electropolymerized film was formed, and then the cross section was removed and a colloidal graphite layer and a silver paint layer were sequentially formed. I let it happen.

Leakage current (when 13V is applied for 2 minutes) after aging the capacitor at 16.2V
The average values of capacitance and loss at 120 Hz were 0.046 μA, 4.51 μF, and 1.2%, respectively.

As is clear from this, according to the manufacturing method of this example, it is possible to easily obtain a solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics using an electrolytically polymerized polymer as an electrolyte. Excellent effects can be obtained.

As described above, according to this embodiment, a valve metal having a dielectric film with a portion without a dielectric film formed on a part of the surface is used, and a conductive material made of manganese oxide is provided on the surface of the valve metal. A base layer is formed, and a conductive electrolytically polymerized polymer layer is formed via the manganese oxide layer using the portion without a dielectric film formed thereon as a polymerization initiation point, and then the conductive electrolytically polymerized polymer layer is formed including the polymerization initiation point. By removing the portion, a solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics can be obtained.

(Embodiment 3) A third embodiment of the present invention will be described below.

Ten capacitors were produced in the same manner as in Example 1, except that tantalum foil, which had been embossed and anodized at about 90° C. using a 10% phosphoric acid aqueous solution, was used in place of the aluminum edged foil. . Leakage current (when 13V is applied for 2 minutes) and 1 after aging at 16.2V
The average values of capacity and loss at 20Hz are each 0.0
It was 13 μA, 0.32 μF, and 0.9%.

For comparison, an attempt was made to fabricate a capacitor in the same manner as in Example 3 except that a through hole was provided in the protrusion and the dielectric film was not removed, but the electrolytic polymer film did not grow even after 120 minutes. However, I was unable to purchase a capacitor.

As is clear from this, the manufacturing method according to this example has the advantage that it is possible to easily obtain a solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics using an electrolytically polymerized polymer as an electrolyte. Excellent effects can be obtained.

As described above, according to this embodiment, a valve metal having a dielectric film formed on a part of the surface where no dielectric film is formed is used, and a conductive material made of manganese oxide is used on the valve metal surface. A conductive electropolymerized polymer layer is formed via the manganese oxide layer using a part of the non-dielectric film-formed part as a polymerization initiation point, and then the polymerization initiation point is formed. A solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics can be obtained by removing the portion containing the metal.

(Embodiment 4) A fourth embodiment of the present invention will be described below.

A capacitor was prepared in the same manner as in Example 1 except that thiophene monomer was used instead of pyrrole monomer, tetraethylammonium p-toluenesulfonate was used instead of sodium n-butylnaphthalenesulfonate, and acetonitrile was used instead of water. was created. 1
Leakage current (13V) after aging at 6.2V
The average values of capacitance and loss at 2 minutes application) and 120 Hz are 0.066 μA, 4.35 μF, and 1.4%, respectively.
Met.

For comparison, a capacitor was fabricated in the same manner as in Example 4 except that a through hole was formed in the protrusion and the dielectric film was not removed, but the electropolymerized film did not grow even after 120 minutes. However, I was unable to purchase a capacitor.

As is clear from this, the manufacturing method of this example is advantageous in that it is possible to easily obtain a solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics using an electrolytically polymerized polymer as an electrolyte. Excellent effects can be obtained.

As described above, according to this embodiment, a valve metal having a dielectric film formed thereon with a portion on the surface where no dielectric film is formed is used, and a manganese oxide is applied to the surface of the valve metal. forming a conductive base layer consisting of a conductive base layer, and forming a conductive electrolytically polymerized polymer layer via the manganese oxide layer using a portion without a dielectric film as a polymerization initiation point;
Thereafter, by removing the portion containing the polymerization initiation point, a solid electrolytic capacitor with extremely excellent leakage current characteristics and loss characteristics can be obtained.

[0044] In the above embodiment, a case has been described in which the dielectric film is formed on the entire surface and then removed in a portion by making a through hole, but it may also be removed by scraping only the surface. In addition to removal by mechanical means such as, for example, physical means such as sputter etching, or chemical means such as dielectric film dissolution, the present invention provides a method for such removal. It is not limited to. Further, when forming the dielectric film, some portions where the dielectric film is not formed can be provided in advance by means such as resist.

Further, in the above embodiment, only the case where one protrusion is provided and a portion without a dielectric film formed therein is described, but in order to shorten the polymerization time, a plurality of protrusions to be used as polymerization starting points are provided. However, the present invention is not limited to this number. In addition, especially when a foil electrode is used, a part where a dielectric film is not formed, which becomes a polymerization initiation point, is provided at an arbitrary location without providing any protrusions, and after forming an electropolymerized film, the polymerization initiation point part is included. It is also possible to produce a capacitor by removing a part of the main body part.Furthermore, in the above example, only the case where the manganese oxide of the conductive underlayer for electrolytic polymerization was formed by thermal decomposition of manganese nitrate was described. It can also be formed using other manganese salts such as manganese acetate and manganese octylate.

In addition, in the above example, only the case where electrolytic polymerization was carried out using pyrrole monomer and thiophene monomer was described, but derivatives of these may be used as long as the desired electrical conductivity can be obtained. Alternatively, these can be mixed and used if necessary.

[0047]

As described above, the manufacturing method of the present invention uses a valve metal having a dielectric film in which a part of the surface is not formed with a dielectric film, and forms a conductive base layer on the surface of the valve metal. A conductive electrolytically polymerized polymer layer is formed through the conductive underlayer using the portion without a dielectric film formed thereon as a polymerization initiation point, and then the portion including the polymerization initiation point is removed. This method has the advantage that it is possible to realize a solid electrolytic capacitor with excellent leakage current characteristics and loss characteristics using a conductive electrolytically polymerized polymer as an electrolyte.

[Brief explanation of drawings]

[Fig. 1] A plan view of a capacitor electrode portion in an embodiment of the method for manufacturing a solid electrolytic capacitor of the present invention.

[Fig. 2] A partial cross-sectional schematic diagram showing an electrolytic polymerization method in one embodiment of the method for producing a solid electrolytic capacitor of the present invention.

[Explanation of symbols]

1 Capacitor electrode foil body part 2 Capacitor electrode foil protrusion 3 Through hole 4 Anode lead 6 Capacitor electrode foil 7 Anode for electrolytic polymerization 8 Cathode for electrolytic polymerization 9 Electrolyte for polymerization 10 Electrolytic polymerization tank

Claims (6)

[Claims] [Claim 1] A valve metal having a dielectric film with a portion without the dielectric film formed on a part of the surface, a conductive base layer being formed on the valve metal surface, and a dielectric film provided on a part of the valve metal. A method for manufacturing a solid electrolytic capacitor, comprising forming a conductive electrolytically polymerized polymer layer through the conductive underlayer using the film-free portion as a polymerization initiation point, and then removing the portion containing the polymerization initiation point. 2. The method of manufacturing a solid electrolytic capacitor according to claim 1, wherein the valve metal shape has at least one protrusion, and a portion without a dielectric film is provided within the protrusion. 3. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the valve metal is one selected from aluminum and tantalum. 4. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the conductive underlayer is a manganese oxide layer. 5. The method for manufacturing a solid electrolytic capacitor according to claim 4, wherein the manganese oxide layer is formed by thermal decomposition. 6. The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive electrolytically polymerized polymer contains a pyrrole ring or a thiophene ring as a repeating unit.