JP2006108188A - Solid electrolytic capacitor manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the electrostatic capacity of a solid-state electrolytic capacitor. <P>SOLUTION: A ring body 3 comprises a resin having repellency as well as heat-shrinkable properties and has a larger internal diameter than that of an anode leading wire. The ring body is attached to the anode leading line 2 of a capacitor element 1 that comprises sintered tantalum powder or the like. Then, the capacitor element 1 with the ring body 3 attached thereto is immersed in chemical liquid 11 such that at least the entire sintered body is below the fluid level, and a dielectric oxide film is formed by anodization. At this time, the ring body 3 floats on the surface of the chemical liquid. Additionally, after the capacitor element 1 is brought up from the chemical liquid 11, the ring body 3 is caused to heat-shrink for close adhesion to the anode leading wire. Then, the capacitor element is sequentially immersed in polymer-monomer liquid and oxidant liquid, and a solid-state electrolytic layer is formed on the dielectric oxide film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In this invention, a dielectric oxide film is formed on the surface of a capacitor element composed of a sintered body obtained by sintering a powder of a valve action metal and an anode lead-out line derived from one end face of the sintered body. The present invention relates to a method for producing a solid electrolytic capacitor in which a solid electrolyte layer and a cathode layer are sequentially formed on a film and further covered with an exterior resin.

  FIG. 4 is a cross-sectional view showing the structure of a conventional solid electrolytic capacitor. In FIG. 4, 1 is a capacitor element. This capacitor element 1 is formed by pressing a tantalum metal powder, which is one of valve action metals, into a press mold. It is formed by press forming into a desired shape. The capacitor element 1 has an anode lead wire 2 made of a tantalum wire, which is embedded in the capacitor element 1 during press molding. The capacitor element 1 has a dielectric oxide film layer formed on the outer surface thereof, a solid electrolyte layer 4 formed on the dielectric oxide film layer, a carbon layer 5 formed on the solid electrolyte layer 4 and silver. This is a paste layer 6, and a cathode layer is formed by the carbon layer 4 and the silver paste layer 5. Furthermore, an anode lead wire 7 is welded to the anode lead-out wire 2, and a cathode lead wire 8 is connected to the cathode layer. A resin sheath is provided so as to embed the entire capacitor element 1 and the anode lead wire 2 and a part of each of the anode lead wire 7 and the cathode lead wire 8.

  Next, a method for manufacturing a conventional solid electrolytic capacitor having the above-described configuration will be described. First, tantalum metal powder is put into a press mold formed in a desired shape and size, and an anode made of tantalum wire. The lead-out line 2 is embedded so that one end thereof is exposed, and this is pressed to produce a molded body. Subsequently, the molded body is sintered under a high temperature vacuum to produce a porous capacitor element 1. Subsequently, the capacitor element 1 is immersed in an electrolyte such as an aqueous solution of phosphoric acid or nitric acid, and anodized at a voltage corresponding to the rated voltage of the solid electrolytic capacitor to form a dielectric oxide film layer on the outer surface. To do. Subsequently, a solid electrolyte layer 4 made of manganese dioxide or a conductive polymer is formed on the dielectric oxide film layer, and a carbon layer 5 and a silver paste layer 6 are sequentially formed on the solid electrolyte layer 4, Further, the anode lead wire 7 is welded to the anode lead-out wire 2, and the cathode lead wire 8 is connected to the cathode layer. Then, a resin sheath 8 is applied by transfer molding so as to embed a part of the entire capacitor element 1 and the anode lead wire 2 and each of the anode lead wire 7 and the cathode lead wire 8, and along the side surface of the resin sheath 8, The anode lead wire 7 and the cathode lead wire 8 are bent to obtain a solid electrolytic capacitor.

  When forming this solid electrolyte layer, the capacitor element is immersed in a manganese nitrate solution and then fired to form a solid electrolyte layer made of manganese dioxide, or by polymerizing the conductive polymer. In many cases, a solid electrolyte made of a conductive polymer is formed by sequentially immersing in a polymerizable monomer solution and an oxidant solution to polymerize the polymerizable monomer to form a solid electrolyte. When the capacitor element is dipped in the solution, the solution rises along the anode lead-out line, and the solid electrolyte layer may be formed up to the portion of the anode lead-out line where the dielectric oxide film is not formed. Since the portion where the dielectric oxide film is not formed does not have a function as an insulator, a short circuit occurs between the solid electrolyte and the metal.

  In order to prevent such a solution from rising, a heat shrinkable ring body is inserted into the anode lead wire, and the ring body is thermally shrunk to fix it to the anode lead wire, so that the solid electrolyte solution is sealed. It is done to prevent the rise. For example, in Japanese Patent Laid-Open No. 7-201662, a block material is formed at the lead-out portion of the positive lead-out line for the purpose of preventing the reaction solution from creeping up into the tantalum wire due to capillary action when forming the conductive polymer. What has been proposed.

Japanese Unexamined Patent Publication No. 7-201662

  In the conventional solid electrolytic capacitor, the ring body is inserted into the anode lead wire and contracted and fixed, and then the capacitor element is anodized. Therefore, in a state where the ring body is fixed to the lead-out portion of the anode lead-out line, the distance between the ring body and the lead-out surface of the anode lead-out line is narrow, the chemical conversion liquid does not reach sufficiently, and the dielectric oxide film is not formed. There is a case.

  If a solid electrolyte layer is formed where a dielectric oxide film is not formed, a short circuit will occur at that portion. Conventionally, a solid electrolyte layer may be formed up to the end face from which the anode lead-out line is derived. could not. However, in order to obtain a solid electrolytic capacitor having a larger capacitance, it is necessary to form a solid electrolyte layer up to the end face from which the anode lead-out line is derived.

  Therefore, the ring body is attached to the anode lead-out line while being separated from the end face from which the anode lead-out line of the capacitor element is led, and the process from the anodic oxidation of the anode body to the formation of the solid electrolyte layer is also performed. If the body is attached to be separated from the lead-out end face of the anode lead-out line, it is difficult to control the position of the body, resulting in a complicated process.

  Therefore, in the invention according to claim 1, as a method of manufacturing a solid electrolytic capacitor, the surface of a capacitor element comprising a sintered body obtained by sintering a powder of valve action metal and an anode lead-out line derived from one end face of the sintered body. In the method of manufacturing a solid electrolytic capacitor, in which a dielectric oxide film is formed on the dielectric oxide film, a solid electrolyte layer and a cathode layer are sequentially formed on the dielectric oxide film, and further coated with an exterior resin. The step of inserting a ring body made of a resin having shrinkage and having an inner diameter larger than the outer diameter of the anode lead-out line into the anode lead-out line, and the capacitor element into which the ring body is inserted, at least all of the sintered body below the liquid level So that the dielectric oxide film is formed by anodic oxidation and the capacitor element is pulled up from the chemical conversion solution, and the ring body is thermally contracted to form the anode lead-out line. A step of wearing, by the manufacturing method of solid electrolytic capacitor comprising the steps of sequentially forming a solid electrolyte layer and the cathode layer on the dielectric oxide film to prepare a solid electrolytic capacitor.

  A ring body made of a resin having water repellency and heat shrinkability and having an inner diameter larger than the outer diameter of the anode lead-out line is inserted into the anode lead-out line. When a dielectric oxide film is formed by anodic oxidation by dipping in the chemical conversion solution so that it is below the surface, dielectric is applied to the part where the capacitor element is immersed in the chemical conversion solution, that is, the entire surface of the capacitor element and part of the anode lead-out line. A body oxide film is formed. After that, the capacitor element is pulled up from the chemical conversion solution, and the ring body is thermally contracted and brought into close contact with the anode lead wire, thereby fixing the ring body to the root portion of the anode lead wire.

  As described above, in the capacitor element formation step, the ring body floats on the liquid surface, so that the portion where the dielectric oxide film is formed can be widened.

  Therefore, the end surface from which the anode lead-out line of the capacitor element is derived can be immersed in a solution that forms the solid electrolyte, and the solid electrolyte layer can be formed on the end face from which the anode lead-out line of the capacitor element is derived. Moreover, in the subsequent solid electrolyte formation step, the ring body is fixed to the anode lead-out line, so that the rising of the solution forming the solid electrolyte is inhibited by the ring body, so that a dielectric oxide film is formed. A solid electrolyte layer is not formed in the part which does not exist.

  According to a second aspect of the present invention, in the method of manufacturing a solid electrolytic capacitor according to the first aspect, after the step of inserting the ring body into the anode lead-out line, the tip of the anode lead-out line is welded to the frame, and then the anodic oxidation is performed. It is characterized by undergoing a step of forming a film.

  After the step of inserting the ring body into the anode lead-out line, if the tip of the anode lead-out line is welded to the frame, the anodic oxidation treatment of a plurality of capacitor elements and the formation of the solid electrolyte layer remain connected to the metal plate frame The operation can be performed continuously and simultaneously on a plurality of capacitor elements, so that the working efficiency can be improved.

  If an attempt is made to insert a ring body after anodizing the capacitor element, the anodizing process is performed by anodizing the capacitor element by connecting it to a metal plate frame for power supply or holding it with a chuck or the like. After that, it is necessary to detach the capacitor element from the metal plate frame or chuck and insert the ring body. In the process of forming the solid electrolyte, it is necessary to work again by attaching the capacitor element to the metal plate frame or the chuck, resulting in a deterioration in work efficiency.

  In the solid electrolytic capacitor manufactured by the manufacturing method of the present invention, the solid electrolyte can be formed up to the end surface from which the anode lead-out line of the capacitor element is derived, and the capacitance of the solid electrolytic capacitor can be increased.

  Further, according to the manufacturing method of the present invention, the anodizing treatment of the capacitor element, and the formation of the solid electrolyte layer can be performed continuously with respect to the plurality of capacitor elements while being connected to the metal plate frame, Work efficiency can be improved.

  Next, the best mode for carrying out the present invention will be described with reference to FIG.

  First, a binder obtained by dissolving camphor, acrylic resin or the like with an organic solvent is added to and mixed with fine powder of valve action metal such as tantalum, aluminum, niobium or the like. After mixing, the organic solvent is volatilized and removed by heating. Next, the valve action metal powder is compression-molded into a cylindrical shape or a square shape by a press or the like. At this time, the anode lead wire made of a valve metal such as tantalum is inserted into the powder and the other end is drawn. After the compression molding, the capacitor element 1 is formed as shown in FIG. 1A by firing at a high temperature in an atmosphere such as a vacuum.

  After firing, a ring body 3 having an inner diameter larger than the outer diameter of the anode lead-out line is inserted into the anode lead-out line 2 of the capacitor element 1. The ring body 3 is made of heat-shrinkable tetrafluoroethylene, silicone rubber, silicone resin or the like, and has a lighter specific gravity than water and also has water repellency.

  And as shown in FIG.1 (b), it connects with the elongate metal plate frame 10 made from stainless steel etc. in the location of the anode derivation | leading-out line 2 of this capacitor | condenser element 1. FIG. A plurality of capacitor elements 1 are connected to the metal plate frame 10.

  Further, after the capacitor element 1 is connected to the metal plate frame 4, as shown in FIG. 1 (c), the capacitor element 1 is immersed in a chemical conversion solution 11 such as nitric acid or phosphoric acid to perform anodization.

  When the anodizing treatment is performed, the depth is such that the end surface from which the anode lead-out line 2 of the capacitor element 1 is led is completely immersed below the liquid level. When the capacitor element 1 is immersed to such a depth, the ring body 3 inserted into the anode lead-out wire 2 comes to float on the liquid surface. In this state, a direct current is supplied from the metal plate frame 10 to the capacitor element 1 to form a dielectric oxide film on the surface of the capacitor element 1. Since the dielectric oxide film is formed at the portion in contact with the chemical conversion liquid 11, the dielectric oxide film forms the entire surface of the sintered body portion obtained by sintering the tantalum powder of the capacitor element 1 and the formation of the anode lead wire 2. It comes to be formed in the part immersed in the liquid.

  And the capacitor | condenser element 1 in which the dielectric oxide film was formed is pulled up from the chemical conversion liquid 11, and the capacitor | condenser element 1 is wash | cleaned and dried.

  Next, as shown in FIG. 1D, the ring body is thermally contracted in a state where the capacitor element 1 is suspended from the metal plate frame 10, and the ring body 3 is fixed to the anode lead wire 2. The heat shrinking method can be achieved by a method of heating the capacitor element 1 in a heating furnace or a method of blowing hot air on the capacitor element 1. When the capacitor element 1 is suspended from the metal plate frame 10, the ring body 3 is in contact with the lead-out end face of the anode lead-out line 2 of the capacitor element 1. In this state, the ring body 3 is thermally contracted to fix the ring body 3 to the root portion of the anode lead-out line 2.

  Next, as shown in FIG. 2A, the capacitor element 1 connected to the metal plate frame 10 is immersed in a polymerizable monomer solution and an oxidant solution, and is made of a conductive polymer on the dielectric oxide film. The solid electrolyte layer 4 is formed.

  Also in the step of forming the solid electrolyte layer 4, the immersion depth of the capacitor element in the polymerizable monomer solution and the oxidant solution is such that the end surface from which the anode lead-out line 2 is led is completely immersed below the liquid surface. Then, it is assumed that the ring body 3 is attached. In this case, since the ring body 3 is fixed to the anode lead-out line, the ring body 3 does not move. The polymerizable monomer solution and the oxidizing agent solution are prevented from rising onto the ring body 3 due to the water repellent function of the ring body 3. Further, since the polymerizable monomer solution and the oxidant solution enter the gap between the ring body and the lead-out end face of the anode lead-out line of the capacitor element, as shown in FIG. An electrolyte layer is formed. Thus, the capacitance of the solid electrolytic capacitor can be increased by increasing the area of the solid electrolyte layer formed on the dielectric oxide film.

  Further, as shown in FIG. 3, a cathode layer comprising a carbon layer 5 and a silver paste layer 6 is formed on the solid electrolyte layer 4, and an anode lead frame 7 and a cathode lead frame 8 are provided on the anode lead-out line and the cathode layer. A solid electrolytic capacitor is completed by applying a resin sheathing 9 so as to cover the whole anode body and part of the electrode lead frame and the cathode lead frame.

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing showing the manufacturing method of the solid electrolytic capacitor of this invention, (a)-(d) represents each process. BRIEF DESCRIPTION OF THE DRAWINGS It is drawing showing the manufacturing method of the solid electrolytic capacitor of this invention, (a)-(b) represents each process which continues from (d) of FIG. It is sectional drawing which shows the structure of the solid electrolytic capacitor manufactured by the manufacturing method of this invention. It is sectional drawing which shows the structure of the solid electrolytic capacitor manufactured by the manufacturing method of the conventional solid electrolytic capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode lead wire 3 Ring body 4 Solid electrolyte layer 5 Carbon layer 6 Silver paste layer 7 Anode lead wire 8 Cathode lead wire 9 Resin sheath 10 Metal plate frame 11 Chemical conversion liquid

Claims (2)

A dielectric oxide film is formed on the surface of the capacitor element consisting of a sintered body obtained by sintering the valve action metal powder and an anode lead-out line derived from one end face of the sintered body, and the dielectric oxide film is formed on the dielectric oxide film. In the method for producing a solid electrolytic capacitor in which a solid electrolyte layer and a cathode layer are sequentially formed and further coated with an exterior resin,
A step of inserting a ring body having an inner diameter larger than the outer diameter of the anode lead-out line into the anode lead-out line, made of a resin having water repellency and heat shrinkability;
A step of immersing the capacitor element in which the ring body is inserted in a chemical conversion solution so that at least the sintered body is all below the liquid surface, and forming a dielectric oxide film by anodic oxidation;
A step of pulling up the capacitor element from the chemical conversion liquid, causing the ring body to thermally contract, and closely contacting the anode lead wire;
A method for producing a solid electrolytic capacitor comprising a step of sequentially forming a solid electrolyte layer and a cathode layer on a dielectric oxide film. 2. The solid electrolytic capacitor according to claim 1, wherein after the step of inserting the ring body into the anode lead-out line, a step of welding the tip of the anode lead-out line to the frame and then forming an anodic oxide film is performed. Production method.