JP2005353705A - Method of manufacturing solid-state electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a solid-state electrolytic capacitor having no deterioration in electric characteristics such as a decline in electrostatic capacitance and an increase in dielectric loss and leakage current, by preventing the creeping up or attachment of manganese contained in a semiconductor mother liquor or a graphite solution onto an anode lead wire. <P>SOLUTION: Valve action metal powder is press-molded and then is sintered to fabricate a capacitor element. Thereafter, the anode lead wire coated with a water-repellent insulation resin is cut into a length of 10 mm, and the cutting face is welded to the element, and thereby the creeping up of manganese onto the anode lead wire and the penetration of an insulating material into the inside of the capacitor element can be surely prevented, resulting in fabrication of the capacitor element with no deterioration in electric characteristics. Furthermore, since the size of a space between a portion where the insulating material is formed and the entire capacitor element can be minimized, the volumetric efficiency of the capacitor element is increased and thereby a solid-state electrolytic capacitor can be provided with a large capacitance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid electrolytic capacitor, and more particularly to a method of manufacturing a capacitor element capable of preventing the electrolyte from creeping up into a lead wire embedded in a metal powder sintered body having a valve action.

Conventionally, a method for producing a solid electrolytic capacitor includes first forming a capacitor element by pressure forming metal powder having a valve action such as tantalum or niobium, and sintering the element to form a sintered body. A lead wire to be an anode is welded to form an anodic oxide film to be a dielectric.
Next, after impregnating the capacitor element on which the anodized film is formed with an aqueous manganese nitrate solution, a process of thermally decomposing the manganese nitrate by heat treatment is repeated a plurality of times to form a manganese dioxide layer.

  When this manganese dioxide layer is formed, if the manganese nitrate aqueous solution crawls up on the surface of the lead wire and the manganese dioxide layer is formed on the surface of the lead wire on which the dielectric oxide film is not formed, The electrical insulation between them is impaired, causing leakage current characteristics failure and short circuit failure.

Therefore, a manganese dioxide layer is not formed on the surface of the anode lead wire by applying a water-repellent liquid insulating agent 4b to the root portion of the lead wire welded to the capacitor element and then solidifying or inserting the insulating ring 4c. Ingenuity is taken (for example, refer to Patent Documents 1 and 2).
JP 2002-270468 Japanese Patent Laid-Open No. 10-116753

However, in the conventional method shown in FIG. 6, since the insulating material (water repellent liquid insulating agent 4b) is applied to the surface of the lead wire, the insulating portion cannot be accurately formed in a narrow range of the lead wire.
In addition, since the insulating material (water repellent liquid insulating agent 4b) is applied to the root portion of the lead wire, the insulating material penetrates into the capacitor element, increasing the dielectric loss of the solid electrolytic capacitor and reducing the capacitance. There is a problem that a decrease occurs.

  Then, in the method of inserting the insulating material (insulating ring 4c) as shown in FIG. 7, the variation in the mounting position of the insulating ring 4c with respect to the lead wire becomes large, and further, when the capacitor element is assembled to the solid electrolytic capacitor, the insulating ring Since the volume of the capacitor element is increased by 4c, there is a problem that the volume efficiency of the capacitor element housed in the solid electrolytic capacitor cannot be improved.

  Further, the manganese nitrate aqueous solution rises from the gap between the lead wire and the insulating ring 4c, and a manganese dioxide layer is formed on the surface of the lead wire on which the dielectric oxide film is not formed, resulting in an increase in leakage current and short circuit failure. There is also.

  The present invention solves the above-described problems, and it is an object of the present invention to provide a method for manufacturing a capacitor element that does not deteriorate electrical characteristics such as a decrease in capacitance of a solid electrolytic capacitor, dielectric loss, and increase in leakage current. It is what.

  That is, the present invention is a method in which a valve-acting metal powder is pressure-molded and sintered to form a capacitor element, and a lead wire coated with the water-repellent insulating resin 4a is cut, and the cut surface is used as the capacitor element. And a step of welding.

  The water-repellent insulating resin is a tetrafluoroethylene resin, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin, or a tetrafluoroethylene / hexafluoropropylene copolymer resin. This is a method of manufacturing an electrolytic capacitor.

  Further, in the above-described lead wire welding method, the welding electrode is brought into contact with one side of the lead wire cut surface, the capacitor element is brought into contact with the opposite cut surface, and welding is performed by electric resistance welding. This is a method of manufacturing an electrolytic capacitor.

  Since the present invention uses a lead wire pre-coated with a water-repellent insulating resin, the water-repellent insulating resin does not penetrate into the capacitor element and can reliably prevent the manganese nitrate from creeping into the lead wire. In addition, it is possible to manufacture a capacitor element that does not cause deterioration of electrical characteristics such as a decrease in electrostatic capacitance, dielectric loss, and increase in leakage current of the solid electrolytic capacitor.

  Furthermore, since the gap dimension between the insulating material forming portion and the capacitor element body can be minimized, the capacitor element total length W with respect to the solid electrolytic capacitor total length L shown in FIG. 5 can be increased without increasing the dielectric loss of the solid electrolytic capacitor. Since the volume efficiency of the capacitor element can be maximized, the capacity of the solid electrolytic capacitor can be increased.

Embodiments of the present invention will be described below with reference to the drawings.
First, a capacitor element in which tantalum powder was pressure-molded was vacuum-sintered at a high temperature, and then a reel-like tantalum lead wire previously coated with a tetrafluoroethylene resin was cut into a length of 10 mm, as shown in FIG. A welding electrode is brought into contact with one side of the cut surface of the lead wire where the tantalum metal is exposed, the capacitor element is pressed against the opposite cut surface, and the lead wire is welded to the capacitor element by electric resistance welding (FIGS. 1 and 2). .
Then, an anodization is performed by applying a formation voltage of 30 V in an aqueous phosphoric acid solution to form a tantalum dielectric oxide film on the surface of the capacitor element.

  Next, after impregnating the capacitor element with an aqueous manganese nitrate solution, the process of thermally decomposing the manganese nitrate by heat treatment at 200 to 400 ° C. for 10 minutes is repeated a plurality of times to sufficiently form a manganese dioxide layer on the dielectric oxide film. . Next, it is immersed in a graphite liquid in which graphite powder is suspended, dried in a thermostatic chamber, and then a metal layer such as a cathode silver layer is formed to form a capacitor element.

  Thereafter, the insulating material on the surface of the lead wire connected to the anode terminal is removed (FIG. 4), the lead wire and the anode terminal are connected by welding, and the cathode terminal is connected to the cathode silver layer forming the capacitor element by the conductive adhesive. Then, transfer molding is performed to obtain a chip-type tantalum solid electrolytic capacitor.

  Next, a characteristic comparison between the embodiment of the present invention and the conventional example will be described. After the lead wire was welded to the capacitor element obtained by press-molding and sintering tantalum powder after applying the above-described manufacturing method, a water-repellent liquid insulating agent 4b was applied and cured on the surface of the lead wire. Except for the point that the insulating part was formed on the surface, the conventional example 1 manufactured by the same means as the example and after welding the lead wire to the capacitor element, the insulating ring 4c was inserted into the lead wire of the capacitor element, and the insulating part was Except for the points formed, the conventional example 2 manufactured by the same means as the example, the ratio W of the total length of the capacitor element to the total length L of each solid electrolytic capacitor [%], and the capacitance, dielectric loss, leakage current after manufacture Table 1 shows the results of the comparison of the values, and Table 2 shows the results of comparison of the values of the electrical characteristics after 1000 cycles of each temperature cycle (−55 ° C. for 30 minutes / + 125 ° C. for 30 minutes).

As is apparent from Table 1, the capacitance and the dielectric loss are improved in the example as compared with the conventional example 1. In addition, the embodiment can increase the capacitor element total length W with respect to the solid electrolytic capacitor total length L compared to the conventional example 2, and as a result, the volume efficiency of the element is improved and the leakage current is also improved. .
Further, as is apparent from Table 2, the example has improved dielectric loss and leakage current after the temperature cycle test as compared with the conventional example 1. In addition, the leakage current of the example is greatly improved as compared with the conventional example 2.
This method was effective not only for products using manganese dioxide but also for products using polymers.

  In the embodiment, a tetrafluoroethylene resin is used as the water-repellent insulating resin coated on the lead wire, but this method is also effective for other water-repellent insulating resin agents.

It is a front view of the state which welded the lead wire coated with the water repellent insulating resin to the capacitor | condenser element by this invention. FIG. 2 is a perspective view when the capacitor element of FIG. 1 is placed horizontally. It is a state diagram when welding a lead wire coated with a water repellent insulating resin to a capacitor element according to the present invention. FIG. 2 is a state diagram after forming the oxide film and the solid electrolyte on the surface of the capacitor element of FIG. 1 and then removing the water-repellent insulating resin from the lead wire connected to the anode terminal. It is a longitudinal cross-sectional view of the solid electrolytic capacitor using the capacitor | condenser element by this invention. It is a front view of the capacitor | condenser element which apply | coated the liquid insulating material to the lead wire by a prior art example. It is a front view of the capacitor | condenser element which inserted the insulating ring into the lead wire by a prior art example. It is a longitudinal cross-sectional view of the solid electrolytic capacitor using a capacitor | condenser element by the prior art example of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Sintered body 3 Lead wire 4a Insulation material (water-repellent insulating resin)
4b Insulation material (liquid insulation)
4c Insulation material (insulation ring)
5 Conductive Adhesive 6 Exterior Resin Layer 7 Anode Terminal 8 Cathode Terminal 9 Lead Wire Welding Power Supply L Total Length of Solid Electrolytic Capacitor W Total Length of Solid Electrolytic Capacitor Element S Distance between Insulating Ring and Capacitor Element End Face T Anode Element and Capacitor Element Distance from end face

Claims (3)

  Pressure forming metal powder and sintering to form a capacitor element, and cutting a lead wire coated with a water-repellent insulating resin and welding the cut surface to the capacitor element. A method for producing a solid electrolytic capacitor characterized by the above.   The water-repellent insulating resin according to claim 1 is a tetrafluoroethylene resin, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin, or a tetrafluoroethylene / hexafluoropropylene copolymer resin. A method for producing a solid electrolytic capacitor.   The lead wire welding method according to claim 1, wherein the welding electrode is brought into contact with one side of the lead wire cut surface, the capacitor element is brought into contact with the opposite cut surface, and welding is performed by electric resistance welding. A method for manufacturing a solid electrolytic capacitor.

Images