JP5376134B2 - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly supply power in transient response by turning a solid electrolytic capacitor into a low ESL. <P>SOLUTION: The solid electrolytic capacitor includes: a capacitor element in which a dielectric oxidized coating layer, a solid electrolytic layer and a cathode portion are successively formed on the inner surface of a concave portion formed on the center of an anode made of a valve action metal, and anodes around the concave portion are formed as an anode portion; a mounting surface for mounting the capacitor element; and a mounting surface facing the wiring substrate. Conductors corresponding to the anode portion and the cathode portion of the capacitor element, respectively, are formed on the surface for mounting the capacitor element; a cathode electrode is formed and anode electrodes are formed on the surrounding of the cathode electrode on the mounting surface facing a wiring board; and the conductors penetrate through the inside and are electrically connected to the anode electrode and the cathode electrode. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a surface mount type solid electrolytic capacitor that uses a conductive polymer as a solid electrolyte and is surface mountable among capacitors used in various electronic devices.

  Along with the higher frequency of electronic equipment, capacitors that are one of the electronic components have been required to have better impedance characteristics in the high frequency range than before, and electrical conductivity has been increased to meet these requirements. Various solid electrolytic capacitors using a highly conductive polymer as a solid electrolyte have been studied.

  In recent years, LSIs such as CPUs typified by computers, LSIs for image processing of televisions, and memories that exchange data with these LSIs have been placed around these devices for power supply applications. A solid electrolytic capacitor to be used is strongly demanded to be small in size and large in capacity. Further, in addition to low ESR (equivalent series resistance) corresponding to high frequency, low ESL (excellent noise removal and transient response) ( Equivalent series inductance) is strongly demanded, and various studies have been made to meet such a demand.

  In order to reduce the ESL of the solid electrolytic capacitor, generally, as a method of reducing the ESL, first, a method of shortening the length of the current path as much as possible, and secondly, a method of forming the current electrolytic path by the current path. A method is known in which the magnetic field is canceled by a magnetic field formed by another current path, and third, a method in which the current path is divided into n and the effective ESL is reduced to 1 / n.

  A solid electrolytic capacitor disclosed in the following patent document is known as a solid electrolytic capacitor that achieves low ESR and low ESL of such a solid electrolytic capacitor.

JP 2008-135425 A JP 2008-294012 A

  As described above, in order to reduce the ESL of this solid electrolytic capacitor, it is effective to make the length of the current path as short as possible as the structure of the solid electrolytic capacitor. That is, the capacitance part of the solid electrolytic capacitor is the interface of the dielectric oxide film, and the distance from the interface of the dielectric oxide film to the anode electrode and the cathode electrode, which are current extraction ports, is Short is preferred.

  In addition, in order to use the method of canceling the magnetic field formed by the current path with the magnetic field formed by another current path, it is effective to increase the canceling effect of the induced magnetic field by bringing the anode electrode and the cathode electrode close to each other. It becomes.

  An object of the present invention is to provide a solid electrolytic capacitor that can supply power quickly during a transient response by using these two ESL reduction elements to achieve low ESL.

  In order to solve the above-mentioned problems, the invention according to claim 1 is that a dielectric oxide film layer, a solid electrolyte layer, and a cathode portion are sequentially formed on the inner surface of a recess formed in the center of an anode body made of a valve metal. A capacitor element having an anode body around the recess as an anode part; a surface on which the capacitor element is mounted; and a mounting surface facing the wiring board. In addition, a conductor corresponding to each of the cathode portions is formed, and on the mounting surface facing the wiring board, a cathode electrode and an anode electrode are formed around the cathode electrode, and the conductor penetrates through the inside and the anode electrode and It is characterized by a solid electrolytic capacitor comprising a mounting substrate electrically connected to each cathode electrode.

  According to the invention described in claim 1 of this application, the distance from the dielectric oxide film of the capacitor element to the anode electrode and the cathode electrode which are power outlets can be shortened. The dielectric oxide film of the capacitor element is formed in a concave portion of the capacitor element, and a power outlet is formed outside the capacitor element through the solid electrolyte layer and the cathode portion. The capacitor element has a cathode electrode drawn out of the solid electrolytic capacitor through the mounting substrate. Thus, the distance from the dielectric oxide film of the capacitor element to the external terminal of the solid electrolytic capacitor is extremely short. The anode body on which the dielectric oxide film is formed is drawn out as an anode electrode through the anode portion of the capacitor element and the conductor of the mounting substrate. Thus, since both the anode and the cathode have a short conductive path inside the solid electrolytic capacitor, the ESL of the solid electrolytic capacitor can be reduced.

  Further, since the anode electrode is arranged around the cathode electrode, the induction magnetic field is canceled out between the anode and the cathode, and in this respect, the ESL of the solid electrolytic capacitor can be reduced.

  In addition, the dielectric oxide film layer, the solid electrolyte layer, and the cathode portion, which are mechanically fragile portions in the solid electrolytic capacitor, are formed in the concave portion of the capacitor element, and are surrounded by the aluminum material and the mounting substrate around the concave portion. Because of the protection, even when mechanical stress is applied to the solid electrolytic capacitor, the mechanical stress applied to the dielectric oxide film layer, solid electrolyte layer, and cathode part is alleviated, and characteristics such as an increase in leakage current Deterioration can be prevented.

  As described above, the structure of the solid electrolytic capacitor can be maintained while maintaining the mechanical strength of the solid electrolytic capacitor, and the ESL of the solid electrolytic capacitor can be reduced.

It is sectional drawing which shows the structure of the solid electrolytic capacitor of this invention. It is a perspective view which shows the mounting substrate of the solid electrolytic capacitor of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  The present invention provides a capacitor in which a dielectric oxide film layer, a solid electrolyte layer, and a cathode portion are sequentially formed on the inner surface of a recess formed in the center of an anode body made of a valve action metal, and the anode body around the recess is an anode portion. An element, a surface for mounting the capacitor element, and a mounting surface facing the wiring board. Conductors corresponding to the anode part and the cathode part of the capacitor element are formed on the surface on which the capacitor element is mounted. The mounting surface facing the substrate includes a cathode electrode and an anode electrode formed around the cathode electrode, and the conductor penetrates through the inside and is electrically connected to the anode electrode and the cathode electrode, respectively. It is a solid electrolytic capacitor provided with.

  1A shows a cross-sectional view of the solid electrolytic capacitor of the present invention, and FIG. 1B shows a cross-sectional view of the solid electrolytic capacitor disassembled into a capacitor element and a mounting substrate.

  A capacitor element 1 used in the present invention will be described with reference to FIG. First, a recess having a predetermined size is formed in the center of the aluminum material 11 by cutting, pressing, etching, or the like on the thin plate-like aluminum material 11. Further, the inner surface of the recess is subjected to a surface enlargement process by etching and further anodized to form the dielectric oxide film 12. Next, a solid electrolyte layer 13 made of a conductive polymer is formed on the dielectric oxide film 12 on the inner surface of the concave portion serving as the cathode, and then graphite and silver paste are formed on the solid electrolyte layer 13 to form the cathode portion. 14 and capacitor element 1. In the capacitor element 1, the aluminum material 11 around the recess serves as the anode portion 15.

  In such a capacitor element 1, the aluminum material 11 as a starting material has a thickness of about 100 to 500 μm, the thickness of the etching layer is 20 to 30 μm, and the depth of the recess from the top of the etching layer is 15 to 50 μm. By setting the thickness, a thin capacitor element can be created.

  By forming the depth of the concave portion of the capacitor element 1 to be shallow, the conductive distance from the dielectric oxide film layer 12 to the cathode portion 14 which is a power outlet of the capacitor element is short, which is suitable for the effect of reducing ESL. It is. However, a dielectric oxide film layer 12 is formed on the inner surface of the recess, and a solid electrolyte layer 13 and a cathode portion 14 are sequentially formed on the dielectric oxide film layer 12. The solid electrolyte layer 13 and the cathode portion 14 are formed in this order. Must not protrude from the respective recesses. Therefore, even if the solid electrolyte layer 13 is formed to have a thickness of about 5 to 10 μm and the cathode portion 14 is formed to have a thickness of about 10 to 15 μm, they do not protrude from the recess. The depth of the recess is required to be about 15 to 50 μm.

  In addition, in order to form the recesses to a depth of about 15 to 50 μm, the thickness of the starting aluminum material 11 needs to be about 100 μm. If it is thinner than this, the aluminum material 11 itself is deformed when the recess is formed, or the strength of the anode body after forming the recess becomes extremely weak.

  However, even when the capacitor element is formed using the aluminum material 1 having a thickness of 100 μm, the strength is not necessarily strong. Therefore, in order to reinforce the strength of such a capacitor element, a steel material having a strength higher than that of aluminum can be attached to the opposite surface of the concave portion of the capacitor element for reinforcement. Also, the strength can be increased by anodizing one surface of the aluminum material in advance.

  If the thickness of the aluminum material 11 is about 500 μm and sufficient strength can be maintained even when the recess is formed, it is not necessary to attach the steel material or improve the strength by anodizing.

  Incidentally, in the capacitor element, it is necessary to avoid applying mechanical stress to the dielectric oxide film layer and the solid electrolyte layer. If mechanical stress is applied to the dielectric oxide film layer and the solid electrolyte layer, the dielectric oxide film may be damaged, leading to an increase in leakage current, and if mechanical stress is applied to the solid electrolyte layer, There is a possibility that the electrical conductivity is lowered. However, in this capacitor element, the dielectric oxide film layer and the solid electrolyte layer are formed inside the concave portion of the anode body, and are protected by being surrounded by the aluminum material 11.

  Next, the mounting substrate 2 will be described. The mounting substrate is based on an insulating substrate 21 such as a glass epoxy substrate, and has an anode electrode 22 and a cathode electrode 23 on the lower surface, and an anode conductor 24 and a cathode conductor connected to the anode and cathode portions of the capacitor element on the upper surface, respectively. 25, and the anode conductor 26 and the anode electrode 24, and the cathode conductor 25 and the cathode electrode 23 on the top surface and the back surface are respectively conducted.

  Further, the configuration of the electrodes on the lower surface of the mounting substrate 2 can be formed in any shape in accordance with the specifications of the CPU and the like to be connected, but as in the shapes of the anode and cathode portions of the capacitor element, FIG. As shown in (b), it is preferable to form the cathode electrode 23 in the shape of an electrode surrounding the anode electrode 22.

  The anode conductor 24 and the cathode conductor 25 formed on the upper surface of the mounting substrate 2 may have shapes matching the anode portion 15 and the cathode portion 14 of the capacitor element 1, respectively. FIG. 2A shows a perspective view as seen from the top surface of the mounting substrate 2. The cathode conductor 25 of the mounting substrate 2 is formed so as to match the shape of the capacitor element 1 in which the cathode portion 14 is formed in the recess and the periphery of the recess is the anode portion 15 as in the structure of the capacitor element 1 described above. An anode conductor 24 is arranged so as to surround it.

  By making the thicknesses of the anode electrode 22 and the cathode electrode 23 all the same, the mounting surfaces of the anode electrode 22 and the cathode electrode 23 become the same plane, and the solid electrolytic capacitor can be stably mounted when mounted on a printed circuit board. Can be installed.

  In addition, since the anode electrode 22 and the cathode electrode 23 are placed close to each other, the currents flowing through the anode electrode 22 and the cathode electrode 23 are in opposite directions, so that the magnetic fields generated by the currents flowing through the respective electrodes cancel each other. As a result, the ESL can be reduced.

  An insulating substrate serving as a base for such a mounting substrate is preferably about 200 μm thick in terms of strength, but can also be about 80 μm thick. The anode electrode, the cathode electrode, and the conductor formed on the insulating substrate are only required to have low electrical resistance and can be soldered, and it is preferable to use a conductor in which gold is plated on copper or nickel. The electrodes and conductors can be formed with a thickness of 30 to 100 μm on one side.

  As a method of conducting the conductors 24 and 25 on the upper surface of the mounting substrate 2 and the electrodes 22 and 23 on the lower surface, a predetermined portion of the mounting substrate 2 is drilled with a laser, and the inner surface of the hole is plated by through-hole plating. Can be planned. The position, the number, etc. of the through holes for this conduction can be arbitrarily designed according to the characteristics such as the current capacity required for the solid electrolytic capacitor.

  In such a mounting board, the distance from the anode part and the cathode part of the capacitor element to the anode electrode part and the cathode electrode part of the mounting board, which is the outlet of current, can be achieved by a distance that is only the thickness of the mounting board. Thus, the current path can be shortened. In particular, the thickness of the mounting substrate is preferably about 200 μm, but a thickness of about 80 μm can be manufactured, and the conductor and electrode are formed on the mounting substrate with a thickness of 30 μm. Therefore, the distance from the cathode portion of the capacitor element to the cathode electrode of the mounting substrate can be made extremely shorter than when the capacitor element is attached to the lead frame and resin molded. For this reason, the ESL of the solid electrolytic capacitor can be reduced, and power can be quickly supplied to the CPU or the like during a transient response.

  The capacitor element 1 as described above is mounted on the mounting substrate 2, and the anode portion 15 and the cathode portion 14 of the capacitor element 1 are joined to the anode conductor 24 and the cathode conductor 24 of the mounting substrate by a conductive adhesive or the like, respectively. Use a capacitor. In this way, when the capacitor element and the mounting substrate are joined by the conductive adhesive or the like, the mechanical stress applied to the cathode portion of the capacitor element can be minimized. In the method of forming an extraction electrode on the cathode portion 14, mechanical stress is applied to the cathode portion 14, and consequently the solid electrolyte layer 13, and the dielectric oxide film 12.

  In addition, the dielectric film layer, solid electrolyte layer, and cathode part of the solid electrolytic capacitor are protected by the mounting substrate, so that not only mechanical stress during manufacturing, but also when stress is applied to the solid electrolytic capacitor during mounting, The stress is relieved and the stress applied to the inside of the capacitor element is also relieved.

  In addition, the capacitor element can be molded with a mold resin as necessary.

  As described above, the capacitor element has a thickness of about 100 μm, and the mounting board has a thickness of about 140 μm including the thickness of the electrodes on both sides and the conductor layer. A solid electrolytic capacitor can be obtained.

C Solid Electrolytic Capacitor 1 Capacitor Element 11 Aluminum Material 12 Oxide Film Layer 13 Solid Electrolyte Layer 14 Cathode Part 15 Anode Part 2 Mounting Substrate 21 Insulating Base Material 22 Anode Electrode 23 Cathode Electrode 24 Anode Conductor 25 Cathode Conductor

Claims (1)

A dielectric oxide film layer, a solid electrolyte layer, and a cathode portion are sequentially formed on the inner surface of the recess formed in the center of the anode body made of a valve metal, and a capacitor element having the anode body around the recess as an anode portion;
A surface on which the capacitor element is mounted and a mounting surface facing the wiring board are provided. Conductors corresponding to the anode part and the cathode part of the capacitor element are formed on the surface on which the capacitor element is mounted. The mounting surface is formed with a cathode electrode and an anode electrode around the cathode electrode, and the conductor penetrates through the inside and is electrically connected to the anode electrode and the cathode electrode, respectively,
Solid electrolytic capacitor consisting of