JP2958040B2 - Method for manufacturing solid electrolytic capacitor - 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 in a chip type solid electrolytic capacitor using an organic conductive compound as an electrolyte.

[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. Generally, such sealing is performed by attaching a sealing body made of elastic rubber to an opening of a bottomed cylindrical outer case containing a capacitor element.

When reducing the size of an electrolytic capacitor having such a sealed structure, it is necessary to simultaneously reduce the size of the sealed structure.However, in order to maintain a sufficient degree of sealing, a certain space for mounting a sealing body, and It is essential to provide a means, which makes it difficult to reduce the size of the electrolytic capacitor. Therefore, although various proposals have been made for chip type electrolytic capacitors on the premise of miniaturization of the electrolytic capacitor body, for example, the height dimension from the printed circuit board is 10 mm.
The limit is about 4 to 4 mm, and it has been extremely difficult to realize a chip-type electrolytic capacitor of about 1 to 3 mm, which is equivalent to the external dimensions of a ceramic capacitor.

On the other hand, a solid electrolytic capacitor that does not use an electrolytic solution 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. For example, a solid electrolytic capacitor using polypyrrole is disclosed in
-158829, JP-A-63-173313, JP-A-1-228122
JP-A-1-232712, JP-A-1-231605, JP-A-1-243510, JP-A-1-260809, JP-A-1-268111
And the like.

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.

However, TCNQ complexes tend to lack chemical stability, and are particularly poor in heat resistance. Therefore, in the case of a solid electrolytic capacitor in which an electrolyte layer made of a TCNQ complex is formed on the surface of an anode body made of aluminum, the electrolyte layer may be denatured by the soldering temperature that usually rises to around 260 ° C, and the chip Was unsuitable for

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 low, and the electrolyte layer may be damaged by mechanical stress applied to the anode body during the manufacturing process.

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 during the manufacturing process even if the electrolyte layer has weak mechanical strength. Is to do.

[Means for solving the problem]

According to the present invention, in a method of manufacturing a solid electrolytic capacitor, a surface of an anode body made of a valve metal is subjected to selective chemical etching to form a concave portion, and an oxide film layer and an electrolyte layer are sequentially formed in the concave portion. It is characterized by:

Further, after cutting the anode body in which the oxide film layer and the electrolyte layer are sequentially formed in the concave portion together with the electrolyte layer, the anode body is disposed on at least one surface of the strip-shaped cathode body, and the cathode body is cut from the cut end face of the anode body. Is derived.

[Action]

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 mechanical strength of the anode body 1 itself is partially increased. It is improved by being formed. Therefore, damage to the electrolyte layer 3 during the manufacturing process can be suppressed, and the electrolyte layer 3 is shielded from the outside air by the surface of the cathode body 5 and the projections 7 of the anode body 1.

The anode body 1 is made of a valve metal and has a selectively exposed portion 2 on the surface, and the exposed portion 2 is etched in a concave shape by a chemical etching process. Therefore, the depth is several tens μm
It is easy to form a fine concave portion 6 having a diameter of one hundred and several tens of μm, and the processing accuracy is improved as compared with a process of forming a concave portion by pressing, cutting, or the like. It does not affect other parts.

Further, the anode body 1 is cut together with the electrolyte layer 3 formed on the exposed portion 2 and then placed on the surface of the strip-shaped cathode body 5. Therefore, the cut end face of the anode body 1 is processed into a notch shape, and while the electrolyte layer 3 formed in the concave portion 6 of the anode body 1 and the cathode body 5 are electrically contacted, the anode body 1 is cut. The cathode body 5 can be led to the outside in a state in which the cathode body 5 is insulated.

Further, the electrolyte layer 3 needs to be formed so as not to come into direct contact with the anode body 1. For this reason, usually, a means for covering a part of the anode body 1 with a resin or the like and forming the electrolyte layer 3 and then removing the resin layer is taken. However, in the present invention, since the electrolyte layer 3 is cut together with the anode body 1 after the formation of the electrolyte layer 3, the electrolyte layer 3 and the anode body 1 also have an oxide film layer which is an insulator on the cut surface of the anode body 1. Thus, there is no need to previously cover a part of the anode body 1 with a resin or the like.

〔Example〕

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

FIG. 1 is a perspective view illustrating a manufacturing process according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing a conceptual structure of a solid electrolytic capacitor formed according to the embodiment of the present invention, and FIG. FIG. 3 is a perspective view showing a solid electrolytic capacitor according to an example. FIG. 4 is a perspective view of a solid electrolytic capacitor according to another embodiment of the present invention.

The anode body 1 is made of a valve metal such as aluminum. A resist layer 8 made of resin or the like is formed on a part of the surface of the flat anode body 1 as shown in FIG. An exposed portion 2 is provided (FIG. 1 (b)). Next, the exposed portion 2 is etched by subjecting the anode body 1 to a chemical etching treatment and has a depth of about
A recess 6 of about 100 μm is formed (FIG. 1 (c)). In this embodiment, the chemical etching treatment is performed by maintaining 1 mol / l of caustic soda at a solution temperature of 50 to 60 ° C., and immersing the anode body provided with the selective exposed portion 2 in the solution for about 1 hour. A concave portion 6 having a depth of 100 μm was provided. In this chemical etching treatment, it is sufficient that the concave portion 6 can be formed on the selective surface of the anode body 1. Other etching treatments include: caustic soda 0.1 to 1 mol / l potassium ferricyanide [K ₃ Fe (CN) ₆ 0.5-1.5 mol / l ・ Trisodium phosphate [Na ₃ PO ₄ .12H ₂ O] A mixed solution consisting of 20-50 g / l is set to a solution temperature of 50-60 ° C. You may soak for 1 hour.

Alternatively, as another example, ・ Ammon fluoride [NH ₄ F] 10 to 30 g / l ・ Ammon sulfate [(NH ₄ ) SO ₄ ] 10 to 30 g / l 1 is immersed for about 5 to 10 minutes.

Various conditions in these chemical etching processes are determined by the depth of the concave portion 6 to be formed. However, other conditions for the secondary etching process for increasing the surface area of the concave portion 6 such as generation of a crystal plane on the surface of the concave portion 6 are also used. May have an effect.

Then, the bottom 6a of the recess 6 is subjected to a secondary etching process, for example, an electrolytic etching process to increase its surface area to roughen the surface thereof, and then subjected to a chemical conversion process to perform a chemical conversion process. An oxide film layer serving as a dielectric is formed on the surface of the substrate. The secondary etching process and the chemical conversion process may be performed on the inner side surface 6b of the concave portion 6 as necessary, for example, for adjusting the capacity.

Next, the anode body 1 is immersed in a pyrrole solution containing an oxidizing agent, a pyrrole thin film is formed by chemical polymerization, and further immersed in an electrolytic solution for electrolytic polymerization in which pyrrole is dissolved, and a voltage is applied. As shown in the conceptual structure diagram of FIG. 2, the concave portion 6 of the anode body 1 has a thickness of several μm to several tens μm.
To produce an electrolyte layer 3 composed of a polypyrrole layer (first)
Figure (d).

Further, a conductive layer 4 is screen-printed on the surface of the electrolyte layer 3. As a result, the electrolyte layer 3 and the conductive layer 4 are sequentially formed in the concave portions 6 of the anode body 1. The conductive layer 4
Multilayer structure consisting of carbon paste and silver paste,
Alternatively, it may have a single-layer structure made of a conductive adhesive containing a metal powder having good conductivity.

Then, the anode body 1 is cut along a cutting line X shown in FIG. 1 (d) to obtain a single anode body 1a as shown in FIG. 1 (e). The cutting line X is substantially at the center of the anode body 1 in this embodiment, and each separated anode body 1a is
On both sides. If necessary, for example, the cutting line is set to Y, and a large-capacity electrolytic capacitor can be obtained.

As shown in FIG. 3, the cathode body 5 is made of strip aluminum or an alloy thereof. On both sides of this cathode body 5,
A plurality of anode bodies 1a and 1b are arranged and stacked such that the conductive layers 4 are in contact with each other. A terminal 9 for extracting an anode is provided on an end surface facing the end surface from which the cathode body 4 is led out.
Are connected by means such as ultrasonic welding and laser welding. Furthermore,
A sealing portion 10 made of a heat-resistant synthetic resin is formed at the lead-out portion of the cathode body 5 to obtain a solid electrolytic capacitor as shown in FIG. The sealing portion 10 may be made of heat-resistant elastic rubber.

Although not shown, the surface of the anode bodies 1a and 1b is covered with a thermosetting heat-resistant resin, and the anode terminals 9 connected to the anode bodies 1a and 1b are connected.
Alternatively, the tip of cathode body 5 may be bent along the side surfaces of anode bodies 1a and 1b.

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

Further, since the concave portion 6 of the anode body 1 in which the electrolyte layer 3 is formed is formed in a concave shape by a chemical etching process,
Even fine processing of about 100 μm can be easily performed by adjusting the concentration of the etching solution, immersion time, and the like.

In this embodiment, the cathode member 5 and the anode lead-out terminal 9 are made of a metal such as copper which can be soldered, but a clad material of aluminum and a solderable metal such as copper is used. May be used. In addition, the cathode body 5
One surface, especially the surface facing the anode body 1 may be subjected to an 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 shown in FIG. 4, only one anode body 1c is subjected to the chemical etching treatment as described in the previous embodiment to form a concave portion 6, and the electrolyte layer 3 and the anode layer 1c are formed on both anode bodies 1c and 1d, respectively. The conductive layer 4 may be formed. In this case, one anode body 1d
Will be formed in a plate shape, it will be possible to obtain a thinner product than the solid electrolytic capacitor by the manufacturing method described in the previous embodiment, and omit the chemical etching treatment of one anode body 1d , The process time is shortened.

〔The invention's effect〕

As described above, the present invention provides a method for manufacturing a solid electrolytic capacitor, in which a concave portion is formed by performing selective chemical etching on the surface of an anode body made of a valve action metal, and an oxide film layer and an electrolyte layer are formed in the concave portion. Are sequentially generated, so that an adverse effect of external mechanical stress on the electrolyte layer of the anode body can be suppressed. Therefore, for example, the electrolyte layer is not damaged even by the pressing of the suction nozzle in the manufacturing process, and a highly reliable solid electrolytic capacitor can be obtained, and the anode body having the electrolyte layer formed on both surfaces of the cathode body As a result, the capacity can be increased.

Further, the cathode body is sandwiched via an electrolyte layer formed on the anode body, and is drawn out as it is. Therefore, a solid electrolytic capacitor that can be surface-mounted on a printed circuit board can be manufactured by simply bending the projecting cathode body along the outer surface of the anode body without connecting it to other external connection terminals, etc. can do.

Further, after cutting the anode body in which the oxide film layer and the electrolyte layer are sequentially formed in the recesses together with the electrolyte layer, the anode body is disposed on at least one surface of the strip-shaped cathode body, and the cathode body is cut from the cut end face of the anode body. Thus, the cathode body can be led out while the cathode body and the electrolyte layer formed in the concave portion of the anode body are in electrical contact with each other.

Also, the electrolyte layer and the anode body are in contact with each other via the oxide film layer which is an insulator also on the cut surface of the anode body, and a part of the anode body is previously covered with a resin or the like, or a step of removing the resin. Is no longer necessary.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a manufacturing process according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing a conceptual structure of a solid electrolytic capacitor formed according to the embodiment of the present invention, and FIG. 1 is a perspective view showing a solid electrolytic capacitor according to the present invention. FIG. 4 is a perspective view of a solid electrolytic capacitor according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Anode body, 2 ... Exposed part, 3 ... Electrolyte layer, 4 ... Conductive layer,
5 Cathode body, 6 recess, 6a bottom (of recess), 6b inner surface of recess, 7 protrusion, 8 resist part, 9 anode terminal

Claims (2)

(57) [Claims] 1. A solid electrolyte, characterized in that a surface of an anode body made of a valve metal is subjected to selective chemical etching to form a concave portion, and an oxide film layer and an electrolyte layer are sequentially formed in the concave portion. Manufacturing method of capacitor. 2. An anode body in which an oxide film layer and an electrolyte layer are sequentially formed in a concave portion is cut together with an electrolyte layer, and this anode body is arranged on at least one surface of a strip-shaped cathode body, and a cut end face of the anode body is cut. A method for manufacturing a solid electrolytic capacitor, wherein a cathode body is derived from the method.