JP3098244B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor, and more particularly to an improvement of a chip type solid electrolytic capacitor using an organic conductive compound.

[Conventional technology]

In recent years, there has been a demand for miniaturization of electronic devices and more efficient mounting on a printed circuit board, etc., so that electronic components have been formed into chips. Along with this, there has been an increasing demand for chipping of electrolytic capacitors, and various proposals have been made.

However, in the case of an electrolytic capacitor, particularly an electrolytic capacitor using an electrolytic solution as an electrolyte, it is necessary to seal the electrolytic solution in a certain storage space. Therefore, the sealing means hinders the miniaturization of the electrolytic capacitor, and various proposals have been made for chip-type electrolytic capacitors on the premise of miniaturization of the main body of the electrolytic capacitor. Is limited to about 10 mm to 4 mm, and it has been extremely difficult to realize a chip type electrolytic capacitor of about 1 mm to 3 mm which is equivalent to the external dimensions of the ceramic capacitor.

On the other hand, a solid electrolytic capacitor that does not use an electrolyte generally has a solid electrolyte layer made of, for example, manganese dioxide or the like formed on an anode body made of tantalum or the like having an oxide film layer formed on its surface, and further has a carbon paste and It has a configuration in which a conductive layer made of silver paste or the like is formed. Such a solid electrolytic capacitor is relatively easy to miniaturize because the electrolyte is solid, and can be made into a chip.

However, the capacitance range of the conventional solid electrolytic capacitor is limited to about 0.1 to 10 μF. Further, although its impedance characteristic is superior to that of an electrolytic capacitor using an electrolytic solution, it is still insufficient compared with a ceramic capacitor or the like, and the cost increases when tantalum is used for the anode body.

[Problems to be solved by the invention]

By the way, recently, tetracyanoquinodimethane (TCNQ),
There has been proposed one in which an organic conductive compound such as polypyrrole is applied to a solid electrolytic capacitor.

These solid electrolytic capacitors have higher electrical conductivity than conventional solid electrolytes made of metal oxide semiconductors, so they excel especially in high-frequency impedance characteristics and do not require liquid to be sealed in the electrolytic capacitor body. Therefore, miniaturization is easy.

In particular, polypyrrole has high conductivity, and a solid electrolytic capacitor using the same as an electrolyte is said to be most suitable for chip formation because the electrolyte is polymerized and has excellent heat resistance.

This polypyrrole is formed on the surface of the anode body by chemical polymerization, electrolytic polymerization or gas phase polymerization of pyrrole. However, the mechanical strength of the polypyrrole itself is weak, and the electrolyte layer may be damaged by mechanical stress such as twisting of the anode body.

In addition, the characteristics of polypyrrole change due to moisture. Therefore, an exterior structure with improved moisture resistance is required.

Such a demand can be satisfied by forming a polypyrrole layer on a strong block-shaped anode body and coating the exterior with a thick exterior resin as in a conventional solid electrolytic capacitor. However, miniaturization of the entire component is hindered, and as described above, it is difficult to make the external dimensions approximately the same as the ceramic capacitor.

An object of the present invention is to provide a highly reliable solid electrolytic capacitor that has sufficient rigidity as a chip-type electronic component and is not damaged even if the electrolyte layer has weak mechanical strength. .

[Means for solving the problem]

The present invention provides a solid electrolytic capacitor in which a plurality of anode bodies each having a recess in which an oxide film layer, an electrolyte layer, and a conductive layer are sequentially formed are bonded to both sides of a strip-shaped cathode body such that the conductive layers face each other. A plurality of anode bodies are joined via a resin layer disposed on a part of the surface of at least one anode body or a resin layer made of a conductive synthetic resin.

As another means, the resin layer is made of a sheet-like resin film covering the surface of the anode body excluding the concave portions. Further, the manufacturing method is characterized in that after a sheet-like resin film covering the surface of the anode body excluding the concave portions is disposed in the gap between the plurality of anode bodies, heat treatment is performed and the anode body is pressed.

(Operation)

As shown in the drawings, in the present invention, a mechanically fragile electrolyte layer 3, for example, a polypyrrole layer is formed in a recess 6 formed in a part of the anode body 1 together with a conductive layer 4. Therefore, the electrolyte layer 3 is surrounded by the outer periphery that becomes the convex portion 7 relatively to the concave portion 6, and the anode body 1
The mechanical strength of itself is also improved by forming the convex portion 7 on a part thereof. Therefore, it is possible to prevent the electrolyte layer 3 from being damaged due to the twist of the anode body 1 and the like, and the electrolyte layer 3 is isolated from the outside air by the anode body 5 and the anode body 1.

The concave portion 6 of the anode body 1 is formed by, for example, press working. However, the strain of the anode body 1 due to the press working appears on the surface of the anode body 1, and the plurality of anode bodies 1 a and 1 b are connected to the anode body 5. When bonding to both surfaces, there may be a gap between anode body 1a and anode body 1b. Alternatively, in order to solve such inconvenience, a step of pressing the anode body 1 with a roller or the like to form the surface of the projection 7 flat is required.

However, in the present invention, the plurality of anode bodies 1a and 1b are
Therefore, the gap due to the distortion of the anode bodies 1a and 1b is closed by the resin layer 9, so that the bonding failure can be prevented.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing a solid electrolytic capacitor according to an embodiment of the present invention, and FIG. 2 is a partial sectional view showing a conceptual structure thereof. FIG. 3 is a perspective view showing an anode body of the solid electrolytic capacitor according to the embodiment of the present invention, and FIG. 4 is an exploded perspective view illustrating the structure of the solid electrolytic capacitor according to the embodiment and a method of manufacturing the same.

The anode body 1 is made of a valve metal such as aluminum.
As shown in FIG. 3, it is formed in a plate shape, and a concave portion 6 having a depth of about 100 μm is formed on a part of its surface by means such as a press. The recess 6 may be provided by other means such as a chemical etching process. The recess 6 is composed of a bottom surface 6a and an inner side surface 6b. As described above, since the recess 6 is formed in a part of the anode body, the protrusion 7 that relatively surrounds the recess 6 is formed.

Then, the surface of the bottom portion 6a of the concave portion 6 is roughened by performing an etching process for enlarging its surface area, for example, an electrolytic etching process, and then a chemical conversion process is performed to oxidize the surface of the bottom portion 6a of the concave portion 6. Form a coating layer. The oxide film layer is made of aluminum oxide obtained by oxidizing the surface layer of anode body 1, which is aluminum, and becomes a dielectric. Note that the etching process and the chemical conversion process may be performed on the inner side surface 6b of the recess 6 as necessary, for example, for adjusting the capacitance.

Further, in the recess 6 formed in the anode body 1, a resist layer 8 covering a part of the surface on which the oxide film layer is formed is formed.
Is coated. The resist layer 8 is made of a heat-resistant synthetic resin,
For example, it is made of an epoxy resin and is formed by means such as screen printing. Similarly, a resist layer 8 is formed on the surface of the recess 6 where the oxide film layer is not formed.

Then, the electrolyte layer 3 made of polypyrrole or the like is formed on the non-coated surface of the resist layer 8. The electrolyte layer 3 is formed by immersing the anode body 1 in a pyrrole solution containing an oxidizing agent, forming a pyrrole thin film by chemical polymerization, and further immersing the electrolyte in an electrolytic solution in which pyrrole is dissolved and applying a voltage. As a result, a thickness of several μm to several tens μm is formed. It should be noted that no polypyrrole layer is generated on the surface of the resist layer 8 where the resist layer 8 is formed, of the surface of the bottom surface 6a and the surface of the inner side surface 6b of the recess 6 because no voltage is applied to the resist layer 8. The resist layer 8 also has a function of preventing a short circuit due to direct contact between the anode body and the polypyrrole layer.

Further, a conductive layer 4 is screen-printed on the surface of the electrolyte layer 3. As a result, as shown in the conceptual structure diagram of FIG. 2, the electrolyte layer 3 and the conductive layer 4 are sequentially formed in the concave portions 6 of the anode bodies 1a and 1b. The conductive layer 4 may have either a multilayer structure made of a carbon paste and a silver paste, or a single layer structure made of a conductive adhesive containing a metal powder having good conductivity.

The plurality of anode bodies 1a and 1b thus formed are arranged on both sides of a strip-shaped cathode body 5 made of copper or its alloy as shown in FIG. 4 so that the respective conductive layers 4 face each other. .

At this time, a sheet-like resin film 10 that covers the surfaces of the anode members 1a and 1b excluding the concave portions 6, that is, the convex portions 7, is disposed between the anode members 1a and 1b. The resin film 10 was made of, for example, an uncured solid epoxy resin composed of an epoxy resin and a curing agent, and used as a sheet-like material which was thermally melted and then solidified and bonded.

Then, in this state, the anode bodies 1a and 1b are joined together and subjected to a heat treatment, while being pressed from above and below the anode bodies 1a and 1b. As a result, the resin film 10 is melted and solidified, and a plurality of anode bodies are formed.
The resin layer 9 is formed in the gap between 1a and 1b. In addition, anode body 1
An anode terminal 2 made of a solderable metal such as copper is welded to the end surfaces of a and 1b by means such as laser welding, and a resin is inserted into a gap between the plurality of anode bodies 1a and 1b as shown in FIG. A solid electrolytic capacitor having the layer 9 is obtained.

In the solid electrolytic capacitor obtained in this way, as shown in FIG. 2, the electrolyte layers 3 are arranged on both surfaces of the cathode body 5 and connected so as to sandwich the cathode body 5 via the conductive layer 4. Therefore, the connection structure between the electrolyte layer 3 and the cathode body 5 is simplified, and at the same time, the electrolyte layer 3 is cut off from the outside by the anode bodies 1a and 1b, and becomes strong against external mechanical stress. .

The plurality of anode bodies 1a and 1b are joined together via the cathode body 5 in the conductive layer 4 and at the same time, the outer periphery thereof, that is, in the relative convex portion 7 formed by the concave portion 6, the anode body 1a, 1b is formed.
The bonding is performed via a resin layer 9 covering the surfaces of the protrusions 1a and 1b. Therefore, the internal electrolyte layer 3 can be sealed from the outside air regardless of the molding accuracy of the anode bodies 1a and 1b. That is, irregularities generated on the surface of the projections 7 of the anode bodies 1a, 1b, distortions of the anode bodies 1a, 1b themselves, and the like are absorbed by the resin layer 9, and the joined state of the anode bodies 1a, 1b can be maintained well. it can.

Further, the lead-out portion of the cathode body 5 is covered with a resist layer 8 covering a part of the concave portion 6, and the end of the electrolyte layer 3 is shielded from the outside by the resist layer 8.

In this embodiment, the cathode body 5 and the anode terminal 2 are made of a solderable metal such as copper. However, a clad material in which aluminum and a solderable metal such as copper are joined is used. You may. Further, one surface of the cathode body 5, in particular, a surface facing the anode body 1 may be subjected to insulation treatment such as coating with a resin, and the folded cathode body 5 may be brought into close contact with the anode body 1.

Further, as another embodiment, the resin layer 9 may be a resin layer 9 made of a thermoplastic synthetic resin such as polypropylene in addition to a thermosetting synthetic resin such as an epoxy resin.

As still another embodiment, the resin layer 9 may be a resin layer made of a conductive synthetic resin. In this case, multiple anode bodies
In addition to a good sealing state of 1a and 1b, a good electrical connection state is also achieved. As in the previous embodiment, a solid electrolytic device in which a plurality of anode bodies 1a and 1b are electrically connected only by the connection terminal 2 is used. Reliability is improved as compared with a capacitor.

〔The invention's effect〕

As described above, the present invention provides a solid body in which a plurality of anode bodies each having a recess in which an oxide film layer, an electrolyte layer, and a conductive layer are sequentially formed are bonded to both sides of a strip-shaped cathode body such that the conductive layers face each other. The electrolytic capacitor is characterized in that a plurality of anode bodies are joined via a resin layer arranged on at least a part of the surface of at least one anode body. Even when the surface roughness occurs, the irregularities and the like are covered by the resin layer. Therefore, it is easy to seal the internal electrolyte layer from the outside air, and it is possible to prevent the electrical characteristics of the electrolyte layer from fluctuating due to moisture or the like, so that it is possible to maintain stable electrical characteristics for a long time. it can.

When a plurality of anode bodies are joined via a resin layer made of a conductive synthetic resin as a resin layer, the electrical connection between the anode bodies is improved, and the reliability is improved.

As still another means, the resin layer is formed of a sheet-like resin film covering the surface of the anode body excluding the concave portions. The resin layer can be formed by being disposed in a gap between the bodies.

Further, as a method of manufacturing a solid electrolytic capacitor according to the present invention, after a sheet-like resin film covering a surface excluding a concave portion of the anode body is disposed in a gap between the plurality of anode bodies, heat treatment is performed and the anode body is pressed. As a result, the resin film melted by the heat treatment can be solidified to form a resin layer in the gap between the plurality of anode bodies, and a strong bonding state can be obtained by pressure welding, further improving the sealing performance. I do.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a solid electrolytic capacitor according to an embodiment of the present invention, and FIG. 2 is a partial sectional view showing a conceptual structure thereof. FIG. 3 is a perspective view showing an anode body of the solid electrolytic capacitor according to the embodiment of the present invention, and FIG. 4 is an exploded perspective view illustrating the structure of the solid electrolytic capacitor according to the embodiment and a method of manufacturing the same. 1 ... Anode body, 2 ... Anode terminal, 3 ... Electrolyte layer, 4 ...
... Conductive layer 5... Cathode, 6... Recess, 6 a... Bottom surface, 6 b.
Resin film

Claims (4)

(57) [Claims] 1. A solid electrolytic capacitor in which a plurality of anode bodies each having a concave portion in which an oxide film layer, an electrolyte layer and a conductive layer are sequentially formed are joined to both sides of a strip-shaped cathode body so that the conductive layers face each other. A solid electrolytic capacitor, wherein a plurality of anode bodies are joined via a resin layer disposed on a part of the surface of at least one anode body. 2. The solid electrolytic capacitor according to claim 1, wherein a conductive synthetic resin is disposed as the resin layer. 3. The solid electrolytic capacitor according to claim 1, wherein the resin layer is formed of a sheet-like resin film covering the surface of the anode body excluding the concave portions. 4. A method according to claim 3, wherein a sheet-like resin film covering the surface of the anode body excluding the concave portions is disposed in the gap between the plurality of anode bodies, and then heat treatment is performed and the anode body is pressed. Method for manufacturing solid electrolytic capacitor.