JPH04113610A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve the hermetically sealing property of an electrolyte layer and to enhance reliability by a method wherein a film composed of a heat- resistant synthetic resin is wound on the outer surface of an anode body, a resin layer is formed inside a recessed part formed at its end part to form a capacitor main body and a cathode terminal which has been. bent along the bottom face from the edge of the capacitor main body is bent in a plurality of parts inside the resin layer. CONSTITUTION:The outer surface of a capacitor main body 9 is covered with a film 10 and a resin layer 11 and is shut off from the outside air. As a result, even when, at a solid electrolytic capacitor in which a plurality of anode bodies 1a, 1b have been arranged on both faces of a cathode terminal 5, a gap is produced between the anode bodies 1a, 1b, it can be blocked up. In addition, an electrode terminal extracted from the capacitor main body 9, especially the cathode terminal 5, is bent in a plurality of parts at the inside of the resin layer 11. Consequently, a long creeping distance can be formed from the outside up to an electrolyte layer 3 at the inside of the anode bodies 1a, 1b along the bonded face of the cathode terminal 5 to the resin layer 11 and a resist layer 8; it is made difficult that the outside air creeps, i.e., moisture or the like creeps.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to solid electrolytic capacitors, and particularly to improvements in chip-type solid electrolytic capacitors using organic conductive compounds.

[Conventional technology]

2. Description of the Related Art In recent years, electronic components have been made into chips due to demands for smaller electronic devices and more efficient mounting on printed circuit boards.

Along with this, there is an increasing demand for electrolytic capacitors to be made into chips.

Solid electrolytic capacitors generally consist of an anode body made of tantalum or the like with an oxide film layer formed on its surface, and a solid electrolyte layer made of manganese dioxide, etc., and are relatively easy to miniaturize. For this reason, the use of chips is progressing. However, in conventional solid electrolytic capacitors, the capacitance range is limited to about 0.1 to 10 μF.

By the way, in recent years tetracyanoquinodimethane (TCNQ)
, it has been proposed to apply organic conductive compounds such as polypyrrole to solid electrolytic capacitors. Solid electrolytic capacitors using these organic conductive compounds have higher conductivity than conventional solid electrolytes made of metal oxide semiconductors such as manganese dioxide, and polypyrrole in particular has poor heat resistance because it is either an electrolyte or a polymer. Because it is also excellent,
It is said to be ideal for making chips.

[Problem to be solved by the invention]

This polypyrrole is produced on the surface of the anode body by chemical polymerization, electrolytic polymerization, gas phase polymerization, etc. of pyrrole.

However, the mechanical strength of this polypyrrole itself is weak,
Depending on the electrode lead-out structure, the electrolyte layer may be destroyed by lead wires or the like during the connection process. Alternatively, mechanical stress applied to the lead wire after the connection process may affect the electrolyte layer, making it difficult to obtain desired characteristics.

Therefore, it is conceivable to arrange a plurality of anode bodies each having an electrolyte layer on both sides of a cathode terminal to form a capacitor body. In such a structure, the electrolyte layer is covered by a strong anode body and is not exposed to external stress.

On the other hand, the electrical properties of polypyrrole tend to change easily due to moisture. Therefore, the electrolyte layer made of polypyrrole needs to be sealed from the outside air. However, as mentioned above, if the anode body is placed on both sides of the cathode terminal, depending on the processing precision of the anode body, a slight distortion may occur in the anode body, or unevenness may occur on the surface of the anode body. Even when multiple anode bodies were welded together by means such as ultrasonic welding, gaps were sometimes created. As a result, it may not be possible to obtain a desired sealed state, and it may be difficult to maintain stable electrical characteristics over a long period of time.

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

An object of the present invention is to improve the sealing performance of an electrolyte layer in a fine chip-shaped solid electrolytic capacitor and to realize a highly reliable solid electrolytic capacitor.

[Failure to solve the problem]

This invention provides 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 arranged on both sides of a flat cathode terminal so that the conductive layers face each other. In addition to wrapping a film made of heat-resistant synthetic resin around the outer surface of the anode body,
The capacitor body is formed by forming a resin layer in the recess formed by the edge of the film, and the cathode terminal is bent from the end face to the bottom face of the capacitor body, and the cathode terminal is bent at multiple locations within the resin layer.

Further, the present invention is characterized in that the anode terminal and the cathode terminal connected to the anode body and bent along the bottom surface 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.

[For production]

As shown in the drawings, in the present invention, a mechanically fragile electrolyte layer 3, such as a polypyrrole layer, is formed together with a conductive layer 4 in a recess 6 formed in a part of an anode body l, and is formed in a relative protrusion 7. surrounded. Since the anode body 1 is disposed on both sides of the strip-shaped cathode terminal 5, the electrolyte layer 3 is shielded from the outside by the strong anode body 1. Further, the cathode terminal 5, which serves as a cathode body electrically connected to the electrolyte layer 3, can be used as it is as a terminal for external connection.

Further, a film 10 is disposed on the outer surface of the anode bodies 1a and 1b, and this film 10 and a resin layer 11 at the end thereof are arranged.
The electrolyte layer 3 is sealed from the outside air.

Therefore, the gap between the anode bodies 1a and lb is closed by the film 1o and the resin layer 11 to maintain sealing performance.

Furthermore, the cathode terminal 5, which is bent from the end surface to the bottom surface of the capacitor body 9, is bent at a plurality of locations 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 even more difficult for outside air to enter from the outside.

In addition, the anode terminal 2 and the cathode terminal 5 are connected to the capacitor body 9.
When it is led out from at least the upper half of the end face of the dowel, the exposed part becomes wider than when it is led out from the center of the dome, and the contact area with the solder can be expanded.

〔Example〕

Next, embodiments of the present invention will be explained 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. Further, FIG. 3 is a partial sectional view showing the conceptual structure of the capacitor main body in the embodiment, FIG. 4 is a perspective view thereof, and FIG. 5 is an exploded perspective view of the capacitor main body.

The anode body 1 is made of a valve metal such as aluminum, and as shown in FIG. 5, a selective recess 6 having a depth of about 100 μm is formed in a part thereof.

The recess 6 may be formed by mechanical processing such as pressing or cutting, or chemical processing such as chemical etching.

The inside of this recess 6 is subjected to etching treatment, for example electrolytic etching treatment, in order to enlarge the surface area.

Further, the etched surface of the recess 6 is subjected to a chemical conversion treatment to form an oxide film layer. This oxide film layer is made of aluminum oxide obtained by oxidizing the surface layer of the anode body 1 made of aluminum, and serves as a dielectric.

Further, a portion near the end of the recess 6 is coated with a resist layer 8 by means such as screen printing.

This resist layer 8 is made of a heat-resistant synthetic resin, such as a phenol resin.

Then, as shown in FIG. 3, an electrolyte layer 3 made of polypyrrole is formed on the uncoated surface of the resist layer 8. This polypyrrole layer, which is the electrolyte layer 3, is the anode body 1.
is immersed in a pyrrole solution containing an oxidizing agent to form a virol thin film in the recess 6 by chemical polymerization, and then immersed in an electrolytic solution for electrolytic polymerization in which pyrrole is dissolved, and a voltage is applied to generate the pyrrole. The thickness thereof is from several μm to several tens of μm.

Furthermore, a conductive layer 4 is screen printed on the surface of this electrolyte layer 3. As a result, an electrolyte layer 3 and a conductive layer 4 are sequentially formed in the recess 6 of the anode body 1, as shown in FIG. This conductive layer 4 may have either a multilayer structure made of carbon paste and silver paste, or a single layer structure made of a conductive adhesive containing metal powder with good conductivity.

Then, a plurality of anode bodies 1a in which conductor layers 4 etc. are generated,
As shown in FIG. 5, the conductive layers 4 are arranged and bonded to both sides of a cathode terminal 5 made of a strip of aluminum or its alloy so that the conductive layers 4 face each other, and ultrasonic welding is performed as necessary. This constitutes the capacitor main body 9 shown in FIG.

A film 10 is wound around the outer surface of the capacitor body 9, as shown in FIG. In this example, the film 10 used is a so-called prepreg made of an aromatic polyamide resin or the like whose surface is coated with an epoxy resin. Then, this film IO is wound around the outer surface of the capacitor body 9, and the ends of the film IO are made to slightly protrude from both end faces of the capacitor body 9, so that the concave portions formed by these ends are filled as shown in FIG. A resin layer 11 was formed. The resin layer 11 is made of a thermosetting synthetic resin such as an epoxy resin, which is filled into the recesses of the film 10 by potting or the like and then solidified.

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

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 surfaces of the resin layer 11 formed in the recesses of the film 10, especially on the end surfaces. It protrudes outward from the half. As shown in FIG. 1, 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 bent horizontally again.

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

Furthermore, the electrode terminals led out from the capacitor body 9, particularly the cathode terminals 5, are bent at a plurality of locations inside the resin layer 11. Therefore, this cathode terminal 5 can be accessed from the outside.
The creepage distance extending to the electrolyte layer 3 inside the anode bodies 1a and 1b can be formed long along the bonding surface between the resin layer 11 and the resist layer 8, making it difficult for outside air to enter, that is, moisture, etc. I can do it.

Next, the moisture resistance characteristics of the solid electrolytic capacitor obtained by the present invention and a conventional solid electrolytic capacitor will be compared.

It is generally known that the properties of organic conductive compounds such as polypyrrole deteriorate due to moisture absorption, or that desired properties as a capacitor cannot be obtained. This is thought to be because conductivity decreases due to oxidation of polypyrrole, and water and anions detopped from polypyrrole deteriorate the oxide film on the anode, resulting in a rapid decrease in capacitance and increased loss. It is being

Therefore, here, the rated voltage is 10V, and the rated capacitance is 8.2μ.
Each sample of F was heated at 60°C and 95% humidity for 10
The capacitance (Cap) and the tangent of the loss angle (t an δ) were measured after being left unloaded for 00 hours.

As a sample, a capacitor main body in which an anode body with an electrolyte layer etc. formed thereon as shown in the previous example was arranged on both sides of a cathode terminal was prepared. (a) Conventional Example 1 No film, no resin layer. The terminal shape was bent from the lead-out part along the end face and bottom face of the capacitor body.

(b) Conventional Example 2: 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 in conventional example 1.

(C) Example nibri preg, resin layer placed. The terminal shape is the same as in the previous example.

And so. The average value of each 30 samples is shown below.

As is clear from these results, it is understood that the solid electrolytic capacitor obtained according to the present invention shows less change in electrical characteristics over time and has excellent moisture resistance compared to Example 1 and Example 2. be done.

〔Effect of the invention〕

As described above, the present invention provides a plurality of anode bodies each having recesses formed sequentially from an oxide film layer, an electrolyte layer, and a conductive layer.
In a solid electrolytic capacitor in which the conductive layers are arranged on both sides of a flat cathode terminal so as to face each other, a film made of heat-resistant synthetic resin is wound around the outer surface of the anode body, and the edges of the film are The capacitor body is formed by forming a resin layer in the recess, and the cathode terminal is bent along the bottom surface of the end face of the capacitor body, and the cathode terminal is bent at multiple locations within the resin layer. Therefore, the cathode electrode can be drawn out by simply placing the anode body on both sides of the cathode terminal, the connection structure of the picture electrode is simple, and a stable connection state can be maintained for a long period of time.

Further, external stress on the anode terminal does not affect the internal electrolyte layer because the anode terminal is connected only to the anode body.

In addition, the outer surface of the capacitor body is covered with a film made of heat-resistant synthetic resin, and the open end of the film is covered with a resin layer, so the gap between the anode bodies is closed by the film regardless of the bonding state. . Since the cathode terminal is bent at multiple points inside this resin layer, the creepage distance from the outside to the electrolyte layer inside the anode body is formed to be long along the bonding surface between the cathode terminal and the resin layer, etc. This can make it difficult for outside air such as humidity 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.

In addition, when 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 the upper half of the end face of the capacitor body, the area of the two electrode terminals exposed to the outside increases. be done. Therefore, when this 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 reliable fixed state can be obtained.

[Brief explanation of drawings]

Next, embodiments 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. Further, FIG. 3 is a partial sectional view showing the conceptual structure of the capacitor main body in the embodiment, FIG. 4 is a perspective view thereof, and FIG. 5 is an exploded perspective view of the capacitor main body. DESCRIPTION OF SYMBOLS 1... Anode body, 2... Anode terminal, 3... Electrolyte layer, 4... Conductive layer, 5... Cathode terminal, 6...
・Concave portion, 7...Convex portion, 8...Resist layer, 9.
... Capacitor body, ]0... Film, 11...
resin layer. Patent application Nippon Chemi-Con Co., Ltd. Figure 1 Figure 1

Claims (2)

[Claims] (1) In a solid electrolytic capacitor in which a plurality of anode bodies each having recesses 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. , a film made of heat-resistant synthetic resin is wound around the outer surface of the anode body, a resin layer is formed in the recess formed by the edge of the film to form the capacitor body, and the capacitor body is bent from the end face to the bottom face. A solid electrolytic capacitor with a cathode terminal bent at multiple points within the resin layer. (2) The solid body according to claim 1, wherein the anode terminal connected to the anode body and bent along the bottom surface from the end face of the capacitor body and the cathode terminal are led out from at least the upper half of the end face of the capacitor body. Electrolytic capacitor.