JP2972304B2 - Solid electrolytic capacitors - 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, demands for chipping of electrolytic capacitors are increasing.

A solid electrolytic capacitor generally has a configuration in which a solid electrolyte layer made of, for example, manganese dioxide or the like is formed on an anode body made of tantalum or the like having an oxide film layer formed on the surface, and is easily reduced in size. Therefore, chipping is progressing. However, in the conventional solid electrolytic capacitor, the capacitance range is limited to about 0.1 to 10 μF.

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. Solid electrolytic capacitors using these organic conductive compounds have a higher conductivity than conventional solid electrolytes made of metal oxide semiconductors such as manganese dioxide.Polypyrrole is particularly resistant to heat because the electrolyte is polymerized. Is also said to be the best for chipping.

[Problems to be solved by the invention]

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 depending on the lead-out structure of the electrode, a lead wire or the like may break the electrolyte layer during the connection process. Alternatively, mechanical stress applied to the lead wire after the connection step affects the electrolyte layer, and it may be difficult to obtain desired characteristics.

Therefore, it is conceivable to arrange a plurality of anode bodies on which the electrolyte layers are formed on both surfaces of the cathode terminal to form a capacitor body. In such a structure, the electrolyte layer is covered with a strong anode body, and there is no external stress.

On the other hand, the electrical characteristics of polypyrrole tend to fluctuate due to moisture. Therefore, it is necessary to seal the electrolyte layer made of polypyrrole from the outside air. However, as described above, when the anode body is arranged on both surfaces of the cathode terminal, a slight distortion occurs in the anode body depending on the processing accuracy of the anode body, or irregularities occur on the anode body surface, and a plurality of Even when the anode body was welded by means such as ultrasonic welding, a gap was sometimes formed. for that reason. In some cases, a desired sealed state cannot be obtained, and it may be difficult to maintain stable electrical characteristics for a long period of time.

Such a problem can be solved by covering the outer surface of the capacitor body with a synthetic resin layer by means such as molding and injection molding. However, miniaturization of the solid electrolytic capacitor is hindered by this exterior resin layer, and pinholes may be formed in the exterior resin layer, so that it is not always possible to obtain high sealing accuracy, that is, a desired moisture resistance performance. could not.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable solid electrolytic capacitor having a fine chip type solid electrolytic capacitor with good sealing performance of an electrolyte layer.

[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 arranged on both sides of a flat cathode terminal so that the conductive layers face each other. In, on the outer surface of the anode body,
A film made of a heat-resistant synthetic resin is wound, and a resin layer is formed in a recess formed by the end of the film to form a capacitor body. Is characterized by being bent at a plurality of locations.

Further, the anode terminal and the cathode terminal which are connected to the anode body and are bent along the bottom surface from the end face of the capacitor body are led out from at least an upper half of the end face of the capacitor body.

(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 concave portion 6 formed in a part of the anode body 1 together with a conductive layer 4, and is formed in a relative convex portion 7. Surrounded. Since the anode body 1 is disposed on both sides of the strip-shaped cathode terminal 5, the electrolyte layer 3 is shut off from the outside by the strong anode body 1. Further, the cathode terminal 5 serving as a cathode body electrically connected to the electrolyte layer 3 can be used as it is as a terminal for external connection.

A film 10 is disposed on the outer surfaces of the anode bodies 1a and 1b, and the electrolyte layer 3 is sealed from the outside air by the film 10 and the resin layer 11 at the end thereof. Therefore, the anode body 1
The gap between a and 1b is closed by the film 10 and the resin layer 11 to maintain the sealing property.

Further, the cathode terminal 5 that is bent from the end face to the bottom face of the capacitor body 9 is bent at a plurality of positions inside the resin layer 11, and the contact portion between the cathode terminal 5 and the resin layer 11 is enlarged. Therefore, it is possible to make it more difficult for outside air to enter from the outside.

Further, when the anode terminal 2 and the cathode terminal 5 are led out from at least the upper half of the end face of the capacitor main body 9, the portion exposed to the outside becomes wider as compared with the case where the anode terminal 2 and the cathode terminal 5 are led out almost from the center part. Be able to expand.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a partial sectional view showing a solid electrolytic capacitor according to an embodiment of the present invention, and FIG. 2 is a perspective view thereof. Also,
FIG. 3 is a partial sectional view showing a conceptual structure of the capacitor body in the embodiment, FIG. 4 is a perspective view thereof, and FIG. 5 is an exploded perspective view of the capacitor body.

The anode body 1 is made of a valve metal such as aluminum.
As shown in FIG. 5, a selective concave portion 6 having a depth of about 100 μm is formed in a part thereof. The concave portion 6 may be formed by using any means of mechanical processing such as press working, cutting processing, or chemical processing such as chemical etching. The interior of the recess 6 is subjected to an etching process, for example, an electrolytic etching process, in order to increase the surface area.

Further, the surface of the concave portion 6 subjected to the etching treatment is subjected to a chemical conversion treatment to form an oxide film layer. This oxide film layer is made of aluminum oxide in which the surface layer of anode body 1 made of aluminum is oxidized, and becomes a dielectric.

A part of the concave portion 6 near the end is coated with a resist layer 8 by means such as screen printing. The resist layer 8 is made of a heat-resistant synthetic resin such as a phenol resin.

Then, on the non-covered surface of the resist layer 8, as shown in FIG. 3, an electrolyte layer 3 made of polypyrrole is generated. The polypyrrole layer serving as the electrolyte layer 3 is formed by immersing the anode body 1 in a pyrrole solution containing an oxidizing agent,
After forming a pyrrole thin film by chemical polymerization, the film is immersed in an electrolytic solution for electrolytic polymerization in which pyrrole is dissolved and a voltage is applied to generate a thin film having a thickness of several μm to several tens μm.

Further, a conductive layer 4 is screen-printed on the surface of the electrolyte layer 3. As a result, the concave portion 6 of the anode body 1 has the third
As shown in the drawing, the electrolyte layer 3 and the conductive layer 4 are sequentially generated. 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.

Then, a plurality of anode bodies 1a on which the conductor layers 4 and the like are generated,
As shown in FIG. 5, 1b is joined to both surfaces of a strip-shaped cathode terminal 5 made of aluminum or an alloy thereof such that the conductive layers 4 are arranged so as to face each other, and if necessary, ultrasonically welded. Thus, the capacitor body 9 shown in FIG. 4 is configured.

A film 10 is wound on the outer surface of the capacitor body 9 as shown in FIG. In this embodiment, a so-called prepreg made of an aromatic polyamide resin having an epoxy resin applied to the surface is used for the film 10. Then, the film 10 is wound around the outer surface of the capacitor body 9 and the ends of the film 10 are slightly protruded from both end faces of the capacitor body 9, as shown in FIG. The resin layer 11 was formed. Resin layer
Numeral 11 is made of a thermosetting synthetic resin such as an epoxy resin, and is filled in a concave portion of the film 10 by means such as potting and then solidified.

One end face of the capacitor body 9, that is, an end face opposite to the end face from which the cathode terminal 2 is led out is made of solderable copper, tin or the like, or an alloy thereof, or can be soldered such as aluminum and copper. Anode terminal 2 made of a clad material with a suitable metal is fixed by means of, for example, ultrasonic welding, laser welding or the like.

As shown in FIGS. 1 and 2, the cathode terminal 5 and the anode terminal 2 led out to both end surfaces of the capacitor body 9 are connected to the end surface of the resin layer 11 formed in the concave portion of the film 10, in particular, on the end surface. It protrudes from the half. Then, at least the cathode terminal 5 is bent upward along the end surface of the capacitor body 9 inside the resin layer 11 and then again horizontally in the resin layer 11, as shown in FIG.

In the solid electrolytic capacitor as described above, the outer surface of the capacitor body 9 is covered with the film 10 and the resin layer 11 and is shielded from the outside air. Therefore, in a solid electrolytic capacitor in which a plurality of anode bodies 1a and 1b are arranged on both surfaces of cathode terminal 5, even if a gap is formed between anode bodies 1a and 1b, this can be closed. Further, for example, the entire volume can be reduced as compared with a sealing structure in which the capacitor body 9 is covered with a mold resin.

Further, the electrode terminal, particularly the cathode terminal 5, led out of the capacitor body 9 is bent at a plurality of positions inside the resin layer 11. Therefore, this cathode terminal 5
Along the bonding surface between the resin layer 11 and the resist layer 8 and the electrolyte layer 3 inside the anode bodies 1a, 1b can be formed long, making it difficult for outside air to enter, that is, entry of moisture and the like. be able to.

Next, the moisture resistance of the solid electrolytic capacitor obtained according to the present invention and the conventional solid electrolytic capacitor will be compared.

Generally, it is known that characteristics of organic conductive compounds such as polypyrrole deteriorate due to moisture absorption, or that desired characteristics as a capacitor cannot be obtained. This is thought to be due to the fact that the conductivity decreases due to the oxidation of polypyrrole, and the moisture and the anions undoped from the polypyrrole deteriorate the oxide film on the anode, so that the capacitance rapidly decreases and the loss increases. Have been.

Therefore, here, each sample having a rated voltage of 10 V and a rated capacitance of 8.2 μF is left unloaded for 1000 hours in a state of 60 ° C. and 95% humidity, and the tangent (tan) of its capacitance (Cap) and loss angle
δ) was measured.

As a sample, a capacitor body in which an anode body having an electrolyte layer and the like shown in the previous embodiment was disposed on both surfaces of a cathode terminal was prepared. (A) Conventional example 1: No film and no resin layer. The terminal shape was bent from the lead-out portion along the end face and the bottom face of the capacitor body.

(B) Conventional example 2: A prepreg [aromatic polyamide + epoxy] is wound, and a resin layer [epoxy] is formed in the opening. The shape of the cathode terminal is the same as that of the conventional example 1.

(C) Example: A prepreg and a resin layer are arranged. The terminal shape is the same as in the previous embodiment.

And The average value of 30 samples is shown below.

As is clear from these results, the solid electrolytic capacitors obtained according to the present invention correspond to the first and second embodiments.
It is understood that the electrical characteristics have less change with time and are superior in humidity resistance characteristics as compared with those of Comparative Example 1.

〔The invention's effect〕

As described above, the present invention arranges 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 on both surfaces of a flat cathode terminal so that the conductive layers face each other. In the solid electrolytic capacitor, a film made of a heat-resistant synthetic resin is wound around the outer surface of the anode body, and a resin layer is formed in a concave portion formed by the end of the film to form a capacitor body. It is characterized in that the cathode terminal bent along the bottom surface is bent at a plurality of positions in the resin layer. Therefore, the cathode electrode can be pulled out only by arranging the anode body on both surfaces of the cathode terminal, the connection structure of both electrodes is simple, and a stable connection state can be maintained for a long time. Further, external stress applied to the anode terminal does not affect the internal electrolyte layer since the anode terminal is connected only to the anode body.

In addition, since the outer surface of the capacitor body is covered with a film made of heat-resistant synthetic resin and a resin layer at the opening end thereof, the gap between the anode bodies is closed by the film regardless of the bonding state. . Since the cathode terminal is bent at a plurality of locations inside the resin layer, a long creepage distance from the outside to the electrolyte layer inside the anode body along the joining surface between the cathode terminal and the resin layer or the like should be formed. This makes it difficult for outside air such as moisture to enter. Therefore, deterioration of the electrolyte layer due to moisture can be reduced, and the life characteristics of the solid electrolytic capacitor can be improved.

Further, when the anode terminal and the cathode terminal which are connected to the anode body and are bent along the bottom face from the end face of the capacitor body are led out from at least the upper half of the end face of the capacitor body, the area of the bipolar terminal exposed to the outside is enlarged. Is done. Therefore, when the solid electrolytic capacitor is mounted on a printed circuit board and soldered, the contact area with the molten solder can be increased, so that a secure fixing state can be obtained.

[Brief description of the drawings]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view showing a solid electrolytic capacitor according to an embodiment of the present invention, and FIG. 2 is a perspective view thereof. FIG. 3 is a partial sectional view showing a conceptual structure of the capacitor body in the embodiment, FIG. 4 is a perspective view thereof, and FIG. 5 is an exploded perspective view of the capacitor body. 1 ... Anode body, 2 ... Anode terminal, 3 ... Electrolyte layer, 4 ...
... conductive layer, 5 ... cathode terminal, 6 ... concave part, 7 ... convex part,
8: resist layer, 9: capacitor body, 10: film, 11: resin layer.

Claims (2)

(57) [Claims] A solid electrolyte comprising 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, and arranged on both sides of a flat cathode terminal such that the conductive layers face each other. In the capacitor, a film made of heat-resistant synthetic resin is wound around the outer surface of the anode body,
A solid electrolytic capacitor in which a resin layer is formed in a concave portion formed by an end of a film to form a capacitor body, and a cathode terminal bent from an end face to a bottom face of the capacitor body at a plurality of positions in the resin layer. 2. An anode terminal connected to an anode body and bent from the end face of the capacitor body along the bottom surface and the cathode terminal are led out from at least an upper half of the end face of the capacitor body. Solid electrolytic capacitors.