JPH03284818A - Solid electrolytic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent damage during a manufacturing process even in an electrolytic layer having sufficient rigidity and mechanically fragile strength by successively forming a dielectric layer, the electrolytic layer and a conductive layer into a recessed section and arranging anode bodies, in which oxide film layers are formed in one part or the whole of outer surfaces, on both surfaces of cathode bodies. CONSTITUTION:Mechanically fragile electrolytic layers 3 are formed into recessed sections 6 formed to one parts of an anode body 1 together with conductive layers 4, and surrounded by relative projecting sections 7. The anode bodies 1 are disposed on both surfaces of a beltlike cathode body 5. Consequently, the electrolytic layers 3 are interrupted from the outside by the anode bodies 1, and the electrolytic layers 3 need not be hermetically sealed from the outside air. Oxide film layers as a rigid insulator are formed onto surfaces except surfaces in the recessed sections 6 of the anode bodies 1, and the mechanical strength of the anode bodies 1 is increased, thus inhibiting the damage of the electrolytic layers 3 even in a manufacturing process and a mounting process to a printed board. The outer surfaces of the anode bodies 1 need not be insulated, and the cathode bodies 5 as cathode terminals and anode terminals 2 can be fast stuck along the outer surfaces of the anode bodies 1.

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]

BACKGROUND OF THE INVENTION In recent years, electronic components have been made smaller due to demands for smaller electronic devices and more efficient mounting on printed circuit boards. Along with this, the demand for chip-based electrolytic capacitors has increased, and various proposals have been made.

However, in the case of an electrolytic capacitor, particularly an electrolytic capacitor that uses an electrolytic solution as an electrolyte, it is necessary to seal the electrolytic solution in a certain storage space. - In boat fishing, such sealing is performed by attaching a sealing body made of elastic rubber to the opening of a bottomed cylindrical exterior case that houses a capacitor element.

When miniaturizing an electrolytic capacitor with such a sealed structure, it is necessary to simultaneously downsize this sealed structure, but in order to maintain a sufficient degree of sealing, it is necessary to have a certain space for installing the sealing body, and to It is essential to provide a means, which makes it difficult to miniaturize electrolytic capacitors. For this reason, various proposals have been made for chip-type electrolytic capacitors that are based on the premise of reducing the size of the electrolytic capacitor body.
The limit is about 11 to 4 capacitors, and it has been extremely difficult to realize a chip-type electrolytic capacitor with an external dimension of about 1 mm to 3 m, which is equivalent to the external dimensions of a ceramic capacitor.

On the other hand, solid electrolytic capacitors that do not use electrolyte are made by forming a solid electrolyte layer made of manganese dioxide, etc. on an anode body made of tantalum or the like with an oxide film layer formed on the surface, and then carbon paste. and a conductive layer made of silver paste or the like.

Since the electrolyte of such a solid electrolytic capacitor is solid, it is relatively easy to downsize and can be made into a chip.

However, the capacitance range of conventional solid electrolytic capacitors is limited to about 0.1 to 10 μF. In addition, although its impedance characteristics are superior to electrolytic capacitors using electrolyte, they are still insufficient compared to ceramic capacitors and the like, and if tantalum is used for the anode body, the cost will be high.

[Problem to be solved by the invention]

By the way, in recent years tetracyanoquinodimethane (TCNQ)
, solid electrolytic capacitors using organic conductive compounds such as polypyrrole have been proposed. For example, solid electrolytic capacitors using polypyrrole are disclosed in Japanese Patent Application Laid-open Nos. 158829-1982, 173313-1983, 228122-1992, and 232712-1999.
No., JP-A No. 1-231605, JP-A No. 1-24351
No. 0, JP-A No. 1-260809, JP-A No. 1-2681
No. 11 etc. are mentioned.

These solid electrolytic capacitors have higher conductivity than conventional solid electrolytes made of metal oxide semiconductors, so they have particularly excellent impedance characteristics at high frequencies, and there is no need to seal liquid inside 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 due to the temperature during soldering, which is normally heated to around 260°C. It was unsuitable for chipping.

Polypyrrole has high conductivity, and solid electrolytic capacitors using polypyrrole as the electrolyte are said to be ideal for chipping because the electrolyte is polymerized and has excellent heat resistance.

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

Furthermore, the properties of polypyrrole vary depending on moisture. Therefore, an exterior structure with improved moisture resistance is required.

Such a requirement can be met by forming a polypyrrole layer on a strong block-shaped anode body and covering the exterior with a thick exterior resin, as in conventional solid electrolytic capacitors.

However, this hinders miniaturization of the entire component, and as mentioned above, it has been difficult to make the external dimensions comparable to those of the ceramic capacitor.

The purpose of this invention is to provide a highly reliable solid electrolytic capacitor that has sufficient rigidity as a chip-shaped electronic component and will not be damaged during the manufacturing process even if the electrolyte layer has weak mechanical strength. It is about providing.

[Means to solve the problem]

This invention provides a solid electrolytic capacitor including a dielectric layer,
It is characterized by having a concave portion in which an electrolyte layer and a conductive layer are sequentially formed, and an anode body having an oxide film layer formed on part or all of its outer surface is placed on the rain surface of a strip-shaped cathode body.

As a manufacturing method, selective recesses are provided in a flat anode body made of a valve metal, and a part or all of the outer surface including the recesses is subjected to a chemical conversion treatment to form an oxide film layer. It is characterized in that an electrolyte layer and a conductive layer are subsequently formed in the recess.

[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 1, and is formed in a relative protrusion 7. It will be surrounded. The anode body 1 is placed on the rain surface of the strip-shaped cathode body 5. Therefore, the electrolyte N3 is blocked from the outside by the anode body 1 on which the electrolyte layer 3 is formed, and there is no need to seal the electrolyte layer 3 itself from the outside air. Furthermore, by placing the anode body 1 on the rain surface of the cathode body 5, it is possible to electrically connect the electrolyte layer 3 and the cathode body 5, which simplifies the connection structure and allows the cathode body 5 to It can be used as a terminal for external connection as it is.

Further, on the surface of the anode body 1 which is the outer surface of the solid electrolytic capacitor, that is, on the surface other than the surface inside the recess 6 of the anode body 1,
An oxide film layer, which is a hard insulator, is formed, and the mechanical strength of the anode body 1 itself is improved. Therefore, during the manufacturing process and the mounting process on the printed circuit board, the electrolyte layer can be easily removed by pressure from a transfer nozzle, etc. In addition to being able to suppress damage to the anode body 1, there is no need to insulate the outer surface of the anode body 1, and the cathode body 5, which becomes the cathode terminal, and the anode terminal 2 are brought into close contact along the outer surface of the anode body 1. You will be able to do this.

Further, although the anode body 1 made of aluminum is exposed to the outside, if an oxide film layer is formed on the outer surface of the anode body 1, there is no need to insulate the anode body 1.

〔Example〕

Next, embodiments of the invention will be described with reference to the drawings.

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

The anode body 1 formed in a band shape is made of a valve metal such as aluminum, and as shown in FIG. 1(a), selective recesses 6 with a depth of about 100 μm are formed at regular intervals in a part of the anode body 1. has been done. The recess 6 may be formed by mechanical processing such as pressing or cutting, or chemical processing such as chemical etching. In order to enlarge the surface area within this recess 6, etching treatment, for example electrolytic etching treatment, is performed to roughen the surface.

Next, the outer surface of the anode body 1 including the recess 6, that is, the front surface 9a and the back surface 9b of the anode body 1, is subjected to a chemical conversion treatment to form an oxide film layer on the front surface 9a and the back surface 9b of the anode body 1. This oxide film layer is made of aluminum oxide obtained by oxidizing the surface layer of the anode body 1 made of aluminum, and exhibits insulating properties and is harder than aluminum.

Note that this oxide film layer becomes a dielectric layer within the recess 6 of the anode body 1. Further, the chemical conversion treatment is carried out according to the conditions commonly used. For example, the anode body 1 was immersed in an aqueous solution of about 5% boric acid with ammonia added thereto and adjusted to 6 to 7 pl+, and a direct current voltage was applied to perform the chemical conversion treatment.

Further, the anode body 1 subjected to the chemical conversion treatment is immersed in a pyrrole solution containing an oxidizing agent to form a pyrrole thin film by chemical polymerization in the recesses 6, and then immersed in an electrolytic solution for electrolytic polymerization in which pyrrole is dissolved. At the same time, a voltage is applied to form an electrolyte layer 3 consisting of a polypyrrole layer having a thickness of several μm to several tens of μm as shown in FIG.

Next, a conductive layer 4 is screen printed on the surface of the electrolyte layer 3 (FIG. 1(b)). As a result, as shown in FIG. 2, the electrolyte layer 3 and the conductive layer 4
will be generated sequentially.

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, as shown in FIG. 1(b), this anode body 1 is cut along cutting lines Y, , Y in the width direction of the anode body 10, and cutting lines X in the longitudinal direction. A single anode body 1a as shown in C) is obtained.

If necessary, it is also possible to obtain a smaller solid electrolytic capacitor by cutting the anode body 1, for example, along the cutting line Xi near the approximate center of the anode body 1.

As shown in FIG. 3, the cathode body 5 is made of a strip-shaped aluminum or an alloy thereof. A plurality of anode bodies 1a and 1b are arranged and bonded to the rain surface of this cathode body 5 so that their conductive layers 4 face each other. Further, an anode terminal 2 for drawing out the anode is connected to the end face opposite to the end face from which the cathode body 5 is led out by ultrasonic welding, laser welding, or the like. Further, a sealing portion 8 made of heat-resistant synthetic resin is formed on the lead-out portion of the cathode body 5 to obtain a solid electrolytic capacitor as shown in FIG. The sealing portion 8 may be formed by sandwiching heat-resistant elastic rubber.

Although not shown, since the back surfaces 9b of the anode bodies 1a, 1b are made of insulating aluminum oxide, the anode bodies 1a, 1b
The tips of the anode terminal 2 and the cathode body 5 connected to the anode bodies 1a and 1b may be bent along the side surfaces of the anode bodies 1a and 1b to bring them into close contact.

In the solid electrolytic capacitor obtained by the above manufacturing method, as shown in FIG.
Since the electrolyte layer 3 and the cathode body 5 are placed on the rain surface and connected to the cathode body 5 via the conductive layer 4 in a sandwiching manner, the electrical connection structure between the electrolyte layer 3 and the cathode body 5 is simplified.

In addition, the electrolyte layer 3 is shielded from the outside by the anode bodies 1a and 1b, which have an oxide film layer made of hard aluminum oxide formed on the back surface 9b, and is thus strongly resistant to mechanical stress from the outside. Become.

In addition, in this embodiment, the cathode body 5 and the anode terminal 2
Although a material made of a metal such as copper that can be soldered is used in the above, a cladding material of aluminum and a metal that can be soldered such as copper may also be used.

Further, the oxide film layer formed on the surface of the anode body 1 may be formed by cutting the band-shaped anode body 1 at a desired location and then performing a chemical conversion treatment. In this case, an oxide film layer is also formed on the cut end surface of the anode body 1, and the mechanical strength and insulation of the anode body 1 become stronger.

〔Effect of the invention〕

As described above, the present invention provides a solid electrolytic capacitor that includes a concave portion in which a dielectric layer, an electrolyte layer, and a conductive layer are sequentially formed, and an anode body that has an oxide film layer formed on part or all of the outer surface. Since it is characterized in that it is placed on the rain surface of the strip-shaped cathode body, the anode body that will be placed on the outer surface of the solid electrolytic capacitor is made stronger by the oxide film layer. Therefore, the mechanical strength of the solid electrolytic capacitor itself is improved, and the internal electrolyte layer can be easily protected from external mechanical stress.

Further, the cathode body with the anode body disposed on the rain surface directly serves as a cathode terminal for external connection. Therefore, when the cathode body is bent along the outer surface of the anode body, it is necessary to insulate the cathode body and anode body. When covered with a layer, there is no need to insulate the cathode body and the anode body, which are cathode terminals, and insulation from the wiring pattern of the printed circuit board can be achieved at the same time.

In addition, as a manufacturing method for this solid electrolytic capacitor, selective recesses are provided in a flat anode body made of a valve metal, and a part or all of the outer surface including the recesses is chemically treated to form an oxide film. It is characterized in that after forming a layer, an electrolyte layer and a conductive layer are sequentially formed in the recessed part, so that in the normal process of forming an oxide film layer to serve as a dielectric in the recessed part of the anode body, at the same time, an electrolyte layer and a conductive layer are formed on the surface of the anode body. An oxide film layer can be formed, and a solid electrolytic capacitor in which an oxide film layer is partially formed as described above can be manufactured without changing the manufacturing method.

In addition, in the process of forming an electrolyte layer and a conductive layer in the recesses of the anode body, a hard oxide film layer has already been formed on a part of the surface of the anode body, so during these processes, the anode body is mechanically Even when stress is applied, there is no fear that the fragile electrolyte layer will be damaged, and a highly reliable solid electrolytic capacitor can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional perspective view illustrating the manufacturing process according to an embodiment of the present invention, and FIG. 2 is a partial cross-sectional view showing the conceptual structure of a solid electrolytic capacitor formed according to an embodiment of the present invention. FIG. 3 is a perspective view showing a solid electrolytic capacitor according to an embodiment. 1... Anode body, 2... Anode terminal, 3... Electrolyte layer, 4... Conductive layer, 5... Cathode body, 6... Concave part, 7... Convex part, butt.・Sealing part.

Claims (2)

[Claims] (1) An anode body having a concave portion in which a dielectric layer, an electrolyte layer, and a conductive layer are sequentially formed, and an oxide film layer formed on part or all of the outer surface is placed on the rain surface of a strip-shaped cathode body. A solid electrolytic capacitor characterized by: (2) Selective recesses are provided in a flat plate-shaped anode body made of a valve metal, and a part or all of the outer surface including the recesses is subjected to chemical conversion treatment to form an oxide film layer, and then the recesses are A method for manufacturing a solid electrolytic capacitor, characterized in that an electrolyte layer and a conductive layer are sequentially formed.