JP2006024607A - Solid electrolytic capacitor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which can reduce ESR (Equivalent Series Resistance) and improve heat resistance, and to provide its manufacturing method. <P>SOLUTION: The capacitor is manufactured through a step wherein a U-shaped molding die, a side die having a lead wire hole, and a press upper punch and a press lower punch are used to form a part of a lead wire made of a valve-action metal into a shape like wave, a coil spring, a hook, or a slantly bent object, to bury it in the valve-action metallic powder, to erect it, and to form it by pressing; and a step wherein a porous anode body is manufactured by sintering. Thus, the surface area of the buried part of the lead wire is made large and an anchor effect is generated, resulting in improved drawing strength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid electrolytic capacitor using a sintered body of valve action metal, and more particularly to a solid electrolytic capacitor capable of improving solder heat resistance and reducing ESR (equivalent series resistance) and a method for manufacturing the same.

  Conventionally, in order to manufacture an anode element of a chip-type solid electrolytic capacitor, first, when a valve action metal powder such as Ta (tantalum) or Nb (niobium) is pressure-formed into a predetermined shape, a wire shape made of the same metal is used. A lead wire such as a foil is embedded and planted, and then sintered to obtain a porous anode body. After an oxide film is formed on the porous portion of the anode body, a cathode layer is formed on the outer periphery of the oxide film to produce a capacitor element. At this time, for example, Patent Document 1 discloses a technique of forming an anodized film on a base end portion of a portion protruding from a tantalum sintered body of an anode lead wire as a technology capable of reducing leakage current and downsizing. Has been.

  Further, in the conventional anode body molding process of a chip-type solid electrolytic capacitor, the pressure molding direction of the valve metal may be parallel to the anode lead wire or perpendicular to the anode lead wire. In any case, it is possible to reduce the ESR in proportion to the surface area of the anode lead wire in the anode body. For this reason, the length of the lead wire embedded in the lead wire direction is adjusted to be large and the ESR is reduced, but there is a limit only by adjusting the length.

JP 2000-195757 A

  2. Description of the Related Art In recent years, with the increasing mobility and functionality of electronic devices, a capacitor having a small size, a large capacity, and a low impedance in a high frequency band is required. There is a miniaturization of the valve action metal powder (powder high-CV) to increase the size and capacity, but there is a tendency for the sintering temperature of the anode body to decrease, thereby reducing the adhesion between the anode body and the lead wire. As a result, the ESR increases, and as a result, there is a high possibility that the leakage current characteristics will be deteriorated due to the deterioration of the solder heat resistance characteristics (heat resistance in the soldering process) of the chip solid electrolytic capacitor.

  Accordingly, it is an object of the present invention to provide a solid electrolytic capacitor that can reduce ESR and improve solder heat resistance, and a method for manufacturing the same.

  In order to solve the above problems, the present invention has been made by paying attention to the adhesion and contact area between a porous sintered body of a valve action metal and a lead wire and establishing a manufacturing method thereof.

  That is, the solid electrolytic capacitor according to the first aspect of the present invention is a powder of valve action metal, one end of a lead wire made of the same kind of metal as the valve action metal is exposed and the other part is embedded, and then pressure-molded and sintered. In a solid electrolytic capacitor using a capacitor element in which a porous anode body is formed, an oxide film is formed on the anode body, and a cathode layer is provided, a portion of the lead wire embedded in the anode body is a coil spring. It is characterized by being a shape, a wave shape, a hook shape, or a shape bent diagonally.

  According to a second aspect of the present invention, there is provided a method for producing a solid electrolytic capacitor comprising: a U-shaped molding die; a side die having a lead wire hole; an upper punch and a lower punch; Forming a corrugated portion into a wave shape, coil spring shape, saddle shape or obliquely bent shape, embedding it in a valve metal powder, planting and pressure forming, and sintering to produce a porous anode body A step of forming an oxide film on the anode body, a step of forming a cathode layer to form a capacitor element, a step of connecting an anode terminal and a cathode terminal to the capacitor element, and a step of sheathing with an insulating resin It is characterized by including.

  As described above, in the present invention, since the shape of the embedded portion of the lead wire in the anode body is a coil spring shape, a wavy shape, a saddle shape, or an obliquely bent shape, it acts as an anchor, and the lead wire installation direction By improving the lead pull-out strength, the internal physical stress in the soldering process is reduced, the solder heat resistance is improved, and the leakage current failure can be reduced.

  In addition, according to the present invention, the contact area between the lead wire and the powder is increased and the contact resistance is decreased, so that a solid electrolytic capacitor with reduced ESR can be provided.

  In order to manufacture an anode element in a chip-type solid electrolytic capacitor, first, valve action metal powder such as Ta (tantalum), Nb (niobium) or the like, together with a binder or the like, is formed into a mold having a predetermined shape such as a corner or a circle. Put in. At that time, the lead wire made of the same metal is pressed into a wave shape, a coil spring shape, a hook shape, or a diagonally bent shape, and is subjected to a drawing process, a folding process, or the like to be embedded and planted. Thereafter, pressure forming is performed and sintering is performed to form an anode body. The actual process up to the pressure molding will be described with reference to FIGS.

  As shown in a perspective view in FIG. 4, a volume surrounded by a U-shaped molding die 1, a side die having a lead wire hole 3, and a punch 6 under the press is approximately the volume after pressing. An amount of powder 2 that is supposed to be halved is charged.

  Next, as shown in a perspective view in FIG. 5, the lead wire 4 before processing is pulled out through the lead wire hole 3 of the side mold 5, and the lead wire 4 is processed to a size that fits in the space. In that case, the lead wire 4 is processed into a wave shape, a coil spring shape, a hook shape, and an obliquely bent shape.

  Further, as shown in a perspective view in FIG. 6, the side mold 5 is lowered to such an extent that the lead wire 4 is buried in the powder 2. Thereafter, as shown in a perspective view in FIG. 7, a prescribed amount of powder is supplied from above the lead wire 4 and buried. After supplying the powder, pressing is performed by an upper press punch 7 and a lower press punch 6 above and below the molding die 1 and molding is performed. Thereafter, sintering is performed.

  Next, an oxide film is formed on the porous surface of the sintered body by a known technique, and a cathode layer is provided to obtain a capacitor element. Further, an anode terminal and a cathode terminal are connected to the capacitor element, molded with an exterior resin, and diced to obtain the solid electrolytic capacitor of the present invention.

  Next, the shape of the lead wire will be described in detail with examples.

  FIG. 8 is a perspective view showing the capacitor element of Example 1 with wavy lead wires, 4 is a lead wire, and 8 is a porous sintered body as an anode body. The anode body is formed by embedding a valve lead metal powder such as Ta (tantalum), Nb (niobium), etc., which has been previously processed into a corrugated lead wire for anode extraction, by pressure molding. Sintering was performed. There is no directionality of wave processing, and the width is taken so that the bent portion does not protrude from the width of the sintered body, and the number of times of bending is one or more.

  FIG. 9 is a perspective view showing the capacitor element of Example 2 using a coil spring-shaped lead wire. Like the case of Example 1, the lead wire for pulling out the anode is processed into a coil spring shape, embedded, pressed, and sintered. The result is a result. The coil spring diameter has a width so that it does not protrude from the lateral width of the sintered body, and the vertical gap of the coil spring winding can be selected from 0 mm (none) to a length that does not protrude from the sintered body. is there.

  FIG. 10 is a perspective view showing the capacitor element of Example 3 using a hook-shaped lead wire, in which the lead wire for pulling out the anode is processed into a needle shape and then embedded, pressure-molded, and sintered. . This needle shape is a shape that is once inserted from the outside to the inside of the sintered body and folded back inside the sintered body. The embedding depth and the dimension of the folding are widths that do not protrude from the outside of the sintered body. Further, the folding direction is not necessarily parallel to the embedding direction of the main part.

  FIG. 11 is a perspective view showing the capacitor element of Example 4 with bent lead wires, and bending the lead wire for anode lead out obliquely with respect to the direction of the external lead wire as in Example 1. Thereafter, embedding, pressure molding, and sintering were performed. In this case, the embedded oblique portion can be straight or curved, the bending width shall not protrude from the width of the sintered body, and if the bending direction is the outer peripheral portion direction of the sintered body, in particular Not specified. In Examples 1 to 4, the thickness of the wire is not limited.

  The characteristics of the capacitor elements obtained in Examples 1 to 4 will be described by focusing on the surface area of the embedded portion of the lead wire. That is, a description will be given from the viewpoint of how the product of the lead wire embedded portion and the surface area of the embedded portion of the lead wire and the ESR depend on the pulling strength, the leakage current related to the solder heat resistance, and the product of the ESR.

  FIG. 1 shows the relationship between the buried portion surface area of the lead wire and the pull-out strength. From FIG. 1, it can be seen that the pullout strength increases as the surface area of the buried portion of the lead wire increases.

  FIG. 2 shows the relationship between the surface area of the buried portion of the lead wire and the leakage current failure. As shown in FIG. 2, the leakage current failure decreases as the surface area of the buried portion of the lead wire increases. That is, the solder heat resistance is improved.

  FIG. 3 shows the relationship between the buried portion surface area of the lead wire and the product of the buried portion surface area and ESR of the lead wire. As shown in FIG. 3, the product of the buried wire surface area of the lead wire and the ESR also decreases as the lead wire buried portion surface area increases.

  As described above, since the shape of the embedded portion of the lead wire in the anode body is a coil shape, a wave shape, a saddle shape, or a bent shape, it acts as an anchor, and as shown in FIG. By improving the lead pull-out strength, the internal physical stress in the soldering process is reduced, the solder heat resistance is improved, and the leakage current failure is reduced as shown in FIG.

  Further, since the contact area between the lead wire and the valve action metal powder increases and the contact resistance decreases, a solid electrolytic capacitor capable of reducing ESR as shown in FIG. 3 is obtained.

  As mentioned above, although embodiment and the Example of this invention were described, this invention is not restricted to the form shown in FIGS. 1-11, There exists a design change of the range which does not deviate from the summary of this invention. Are also included in the present invention. That is, it goes without saying that various modifications and corrections that can be made by those skilled in the art are included.

The figure which shows the relationship between the embedded part surface area of a lead wire, and drawing strength. The figure which shows the relationship between the embedded part surface area of a lead wire, and a leakage current defect. The figure which shows the relationship between the buried part surface area of a lead wire, and the product of the buried part surface area and ESR of a lead wire. The perspective view which shows a mode that powder was supplied to the space formed by the U-shaped shaping | molding metal mold | die, the side metal mold | die, and the punch under a press. The perspective view which shows a mode that the lead wire was processed after supplying a lead wire from the side metal mold | die. The perspective view which shows a mode that the side metal mold | die was lowered | hung and the lead wire was embed | buried under powder. The figure which shows a mode that powder is further supplied and it presses with an up-and-down punch. FIG. 3 is a perspective view showing a capacitor element according to the first embodiment. FIG. 6 is a perspective view showing a capacitor element of Example 2. FIG. 6 is a perspective view showing a capacitor element of Example 3. FIG. 6 is a perspective view showing a capacitor element of Example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding die 2 Powder 3 Lead wire hole 4 Lead wire 5 Side die 6 Lower punch 7 Press upper punch 8 Porous sintered body

Claims (2)

  One end of a lead wire made of the same kind of metal as the valve action metal is exposed in the powder of the valve action metal, the other part is embedded and pressure-molded, sintered to form a porous anode body, and the anode In a solid electrolytic capacitor using a capacitor element in which an oxide film is formed on a body and a cathode layer is provided, a portion of the lead wire embedded in the anode body is a coil spring shape, a wavy shape, a saddle shape, or an obliquely bent shape A solid electrolytic capacitor characterized in that   Using a U-shaped molding die, a side die with lead wire holes, a punch on the press and a punch on the press, part of the lead wire of the valve metal is wave-like, coil spring-like, saddle-like or slanted A step of forming into a bent shape, embedding in valve action metal powder, planting and pressure forming, a step of sintering to produce a porous anode body, and a step of forming an oxide film on the anode body; A method for producing a solid electrolytic capacitor comprising: a step of forming a cathode layer to produce a capacitor element; a step of connecting an anode terminal and a cathode terminal to the capacitor element; and a step of sheathing with an insulating resin. .

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