JP2011009683A - Capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor functioning as a noise filter to remove noise in a wideband.SOLUTION: A quadrangular mounting board is prepared where a mounting surface to be surface-mounted on a printed board, and an element mounting surface for mounting a capacitor element are formed on one side surface and the other side surface, respectively, positive electrode terminals and a negative electrode terminal are arranged at four corners of the mounting surface and the center part thereof, respectively, and positive electrode conductors electrically connected to the positive electrode terminals and a negative electrode conductor electrically connected to the negative electrode terminal are arranged at the four corners of the element mounting surface and at the center part thereof, respectively. A capacitor element where a capacitance formation part, an negative electrode layer and a negative electrode extraction part are sequentially laminated at the center part of a conductive body, and a positive electrode extraction part comprising four conductive bodies projecting from the circumference of the negative electrode extraction part is formed is mounted on the mounting board; the positive electrode extraction parts of the capacitor element and the negative electrode extraction part of the capacitor element are connected to the positive electrode conductors of the mounting board and the negative electrode conductor, respectively; and a transmission line structure is formed by the conductive bodies of the capacitor element located at opposing corners of the mounting board.

Description

  The present invention relates to a capacitor, and more particularly to a capacitor that can function as a distributed constant noise filter.

  As a capacitor, for example, a solid electrolytic capacitor using a conductive polymer compound as a solid electrolyte, that is, a cathode electrode layer, the one shown in FIG. 7 is known. FIG. 7 is a cross-sectional view showing a conventional solid electrolytic capacitor. A dielectric layer made of an oxide film is formed on the anode body 304 made of a valve metal, and then a solid electrolyte layer (cathode electrode layer) 305 made of a conductive polymer is formed on the dielectric layer, and further around that After the graphite layer 306 is formed and the cathode layer composed of the silver paste layer 307 is sequentially formed, the anode lead 309 is connected to the other end side of the anode body 304, and the cathode lead 310 is connected to the lower surface of the silver paste layer 307. It is connected and pulled out and molded with exterior resin 308.

  FIG. 8 is a cross-sectional view showing a conventional distributed constant noise filter. A solid electrolyte (cathode electrode layer) 405 made of a conductive polymer, a graphite layer 406, and a silver paste layer 407 are sequentially formed on the surface of the central portion of the dielectric layer formed on the valve metal anode body 404 to form a cathode. Both ends of the body 404 are a pair of anodes, anode leads 409 are connected to both ends thereof, cathode leads 410 are connected to the central silver paste layer 407, and molded with exterior resin 408. This distributed constant type noise filter utilizes the structure of a three-terminal type solid electrolytic capacitor and can also function as a solid electrolytic capacitor.

  Such a solid electrolytic capacitor is disclosed in Patent Document 1, and a three-terminal capacitor type distributed constant noise filter having a distributed constant noise filter structure is disclosed in Patent Document 2.

JP-A-9-260215 JP 2002-164760 A

  The solid electrolytic capacitors or distributed constant noise filters described in the above documents are devices having a single function, and are not devices that simultaneously function as a solid electrolytic capacitor and a noise filter. Capacitors are arranged in the vicinity of the CPU. Capacitors having a function with excellent transient response characteristics for quickly supplying power to an instantaneous voltage drop of the CPU are required, and a noise filter is also arranged in the vicinity of the CPU. It is required to remove the high frequency noise of the power supplied to the CPU and stabilize the operation of the CPU. For this reason, it is desirable that the capacitor and the noise filter are respectively disposed in the vicinity of the CPU, but there are restrictions on disposing them all in the vicinity of the CPU due to the limitation of the mounting area.

  Therefore, a device that has both of these functions and can be used as a capacitor alone or as a distributed constant noise filter alone and further as a capacitor and a distributed constant noise filter is required.

  An object of the present invention is to provide a capacitor that can be used as a capacitor, a distributed constant noise filter, and a composite component having two functions of a capacitor and a distributed constant noise filter in one device.

In order to solve the above problems, the present invention provides a rectangular mounting board in which a mounting surface that is surface-mounted on a printed circuit board on one surface and an element mounting surface on which a capacitor element is mounted on the other surface; A capacitor element, wherein the mounting substrate has anode terminals at the four corners of the mounting surface and cathode terminals at the center, and an anode conductor that is electrically connected to the anode terminals at the four corners of the element mounting surface. In addition, a cathode conductor that is electrically connected to the cathode terminal is disposed in the central portion, and the capacitor element has a capacitance forming portion, a cathode electrode layer, and a cathode leading portion sequentially stacked in the central portion of the conductor. An anode lead portion made of four conductors protruding from the periphery is formed. The anode lead portion of the capacitor element is placed on the anode conductor of the mounting substrate, and the cathode lead portion of the capacitor element is placed on the cathode conductor. And respectively connected, characterized in that the transmission line structure of a conductive material of the capacitor element located at the opposing corners of the mounting substrate.
In addition, the capacitor element is made of a rectangular conductor, and the anode lead part is formed by stacking a plurality of capacitor element pieces protruding from both ends of the cathode lead part in a cross shape, or the capacitor element is a cross-shaped conductive element. It consists of a body, and the anode extraction part protruded from the circumference | surroundings of the cathode extraction part.

  According to the present invention, the anode terminal is led out in four directions, and the cathode terminal functions as a five-terminal capacitor having a central portion. Furthermore, the capacitor element is formed by sequentially laminating a capacitance forming portion, a cathode electrode layer, and a cathode lead portion at the center of the conductor, and an anode lead portion comprising four conductors protruding from the periphery of the cathode lead portion is formed. The diagonally located anode terminals constitute a transmission line structure with a conductor. Since the dielectric layer and the cathode electrode layer serving as the capacitance forming portion of the capacitor element can function as a distributed constant circuit, it can function as a three-terminal noise filter using the distributed constant circuit portion as a filter portion. That is, when this capacitor is mounted on a circuit board, an electrical signal input from one of the opposing anode terminals arranged diagonally is filtered by the distributed constant circuit section, and the electrical signal is output to the other anode terminal Will be

  The transmission line structure of the capacitor element is a crossed structure. Therefore, the crossed transmission line structures can be regarded as independent transmission lines in terms of electrical circuits. When the capacitor according to the present invention is viewed as a distributed constant type noise filter, the transmission line structure is orthogonal, and the phase of the induction magnetic field generated from each transmission line is shifted, so that there is little mutual influence.

  And if it is set as the transmission line structure which consists of the anode terminals arrange | positioned diagonally, the length of the transmission line in the square fixed mounting surface can be made into the longest thing. As a result, the distributed constant circuit portion formed on the transmission line can be formed longer. In general, in order to function as a noise filter with high efficiency, it is desirable that the length of the distributed constant circuit unit is ¼λ or more when the wavelength λ of the input noise wave is used. Therefore, in order to function as a noise filter that can cope with a wideband frequency, the longer the distributed constant circuit portion, the better.

  For this reason, in the capacitor of the present invention, the transmission line length is the longest among the capacitors having a fixed mounting area, and the length of the distributed constant circuit portion on the transmission line can be increased. It becomes possible to reduce the size of the noise filter.

  When viewed as a capacitor, it is a five-terminal capacitor having a cathode terminal in the center and four anode terminals around it. By using a five-terminal capacitor in this way, the current path can be divided into four, and the substantial ESL of the capacitor can be reduced to ¼.

  Further, it is possible to use one of the crossed transmission line structures as a capacitor and the other as a distributed constant noise filter.

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows embodiment of this invention, (a) is a top view of a capacitor | condenser, (b) shows sectional drawing cut | disconnected by the AA line in Fig.1 (a). It is drawing which shows another embodiment of this invention. It is drawing which shows the mounting substrate used for the solid electrolytic capacitor of this invention, (a) is a figure which shows an element mounting surface, (b) is drawing which shows a mounting surface. It is drawing which shows one form of the capacitor | condenser element of this invention. It is drawing which shows one form of the capacitor | condenser element of this invention. It is drawing which shows one form of the capacitor | condenser element of this invention. It is sectional drawing which shows the internal structure of the conventional solid electrolytic capacitor. It is sectional drawing which shows the internal structure of the conventional distributed constant type noise filter.

  Next, embodiments for carrying out the present invention will be described in detail.

  The capacitor of the present invention has a capacitance forming portion, a cathode electrode layer, and a cathode lead portion at the central portion of the conductor, and an anode composed of four conductors protruding from the periphery of the cathode lead portion in four directions from the cathode lead portion. The capacitor element having the lead portion is mounted on a mounting substrate.

First, the present invention will be described by taking a capacitor element used for a solid electrolytic capacitor as an example. The capacitor element has a dielectric layer, a cathode electrode layer, and a cathode lead portion as a capacitance forming portion at the center of the conductor, and has a cathode lead portion. As long as it is a capacitor element in which an anode lead part made of four conductors protruding from the periphery of the cathode lead part is formed in four directions, a capacitor element used for a ceramic capacitor or an electric double layer capacitor may be used.
The capacitor element used for the solid electrolytic capacitor has the following forms.
(1) Capacitor element pieces in which both ends of a rectangular conductor made of a valve metal are used as anode lead portions, and a capacitor forming portion, a cathode electrode layer, and a cathode lead portion are sequentially stacked in the center between the anode lead portions. Capacitor element pieces are overlapped so that the cathode lead portions overlap and the anode lead portions are oriented at a right angle, and the central portion becomes the cathode lead portion, and the anode lead is drawn in four directions from the cathode lead portion. Form in which the part is formed.
(2) A configuration in which a capacitance forming portion, a cathode electrode layer, and a cathode lead portion are sequentially laminated at the center of a conductor made of a valve metal formed in a cross shape, and the end portion is an anode lead portion.

First, the form of the capacitor element described in (1) will be described with reference to FIGS.
As shown in FIG. 4, the capacitor element piece 21 uses a rectangular conductive plate or conductive foil (hereinafter referred to as an anode body) made of a valve metal such as aluminum, and the central portion of the anode body is enlarged by etching. The porous etching layer 25 is formed on both sides of the aluminum foil. At this time, the inside of the anode body is not etched and the aluminum ingot remains, and this aluminum ingot becomes the remaining core layer (FIG. 4A). A dielectric layer made of an oxide film is formed on the surface of the etching layer 25 by anodic oxidation. In this case, both end portions of the anode body are unetched portions and become anode lead portions 22.

  More specifically, the etching treatment is a step of forming a porous etching layer by dissolving both surfaces of the anode body with hydrochloric acid or the like. For example, an anode body made of high-purity aluminum foil having a thickness of 120 μm is used, and a resist protective film (not shown) is formed by applying a resist material from both ends of the anode body to a predetermined distance. After forming the resist protective film, an etching layer is formed in the central part of the anode body at a depth of 40 μm from both sides. In this case, the thickness of the remaining core layer is 40 μm.

  A separation layer 24 is formed on the capacitor element piece, and the anode lead portion 22 and the cathode lead portion 23 of the capacitor element piece 21 are divided. After the etching is completed, the separation layer 24 is coated with an insulating resin and penetrated into the etching layer 25 to insulate the anode lead portion 22 and the etching layer 25.

  Then, the etched anode body is subjected to chemical conversion treatment by anodic oxidation to form a dielectric layer made of aluminum oxide. In the anodic oxidation, a predetermined voltage is applied in a state where the etching foil is immersed in an aqueous solution such as boric acid or adipic acid to form a dielectric layer (not shown) serving as a capacitance forming portion.

  Further, a solid electrolyte layer (not shown) which is a cathode electrode layer is formed on the dielectric layer. The solid electrolyte layer is sequentially immersed in a solution containing a polymerizable monomer that becomes a conductive polymer by polymerization and an oxidizer solution, and is pulled up from each solution to advance the polymerization reaction. These solid electrolyte layers may be formed by a method of applying or discharging a solution containing a polymerizable monomer and an oxidant solution. Moreover, the method of immersing and apply | coating to the mixed solution which mixed the polymerizable monomer solution and the oxidizing agent may be used.

  Further, the solid electrolyte layer can also be formed by an electrolytic polymerization method used in the field of solid electrolytic capacitors or a method of applying and drying a conductive polymer solution. Furthermore, it is also possible to form a solid electrolyte layer by combining these solid electrolyte layer forming methods.

  As described above, thiophene, pyrrole or their derivatives can be suitably used as the polymerizable monomer used for forming the solid electrolyte layer. In particular, the monomer is preferably thiophene or a derivative thereof.

  Examples of thiophene derivatives can be exemplified by the following structures: thiophene or its derivatives have higher electrical conductivity and particularly better thermal stability than polypyrrole or polyaniline. An excellent solid electrolytic capacitor can be obtained.

X is O or S
When X is O, A is alkylene, or when at least one of polyoxyalkylene X is S,
A is alkylene, polyoxyalkylene, substituted alkylene, substituted polyoxyalkylene: wherein the substituent is an alkyl group, alkenyl group, alkoxy group

  Among the thiophene derivatives, 3,4-ethylenedioxythiophene is preferably used.

  As the oxidizing agent used for the polymerization of the polymerizable monomer, an aqueous solution of ferric paratoluenesulfonate, periodic acid or iodic acid dissolved in ethanol can be used.

  Further, as shown in FIG. 4B, a cathode layer 26 composed of a graphite layer and a silver paste layer is sequentially formed on the solid electrolyte layer of the capacitor element piece to form a cathode lead portion 23.

  When the preparation up to the cathode lead-out portion 23 is completed, the resist protective film previously formed on the anode body is removed, and the aluminum at both ends of the anode body is exposed to form the anode lead-out portion 22 and the capacitor element piece 21.

  The capacitor element pieces 21 formed as described above are laminated so that the cathode lead portions 23 overlap with each other and the anode lead portions 22 and 22 form a right angle to each other, so that the center is the cathode lead portion 23 and the cathode lead portion. A capacitor element 20 having a cross-shaped top view in which the anode lead portions 22 are radially arranged in four directions from the lead portion 23 is created.

Next, the form of the second capacitor element described in (2) will be described with reference to FIG.
As shown in FIG. 6 (c), the capacitor element 30 has a valve metal foil or a valve metal plate made of aluminum or the like formed in advance in a cross shape as a starting material, and the ends of the protruding portions protruding in four directions are anodes. The lead portion 32 is formed, and the central portion thereof is formed as the cathode lead portion 32. As shown in FIGS. 6A and 6B, the manufacturing method from the formation of the etching layer 35 to the formation of the cathode layer 36 until the formation of the cathode lead-out portion 33 is the same as the method described above.

  The capacitor element as described above has a structure in which the anode lead portions arranged opposite to each other are electrically connected inside the capacitor element, and further includes a cathode lead portion sandwiched between the anode lead portions. Configure the structure. And since the solid electrolyte layer which is a cathode electrode layer is formed through the dielectric material layer, the part of this solid electrolyte layer forms a distributed constant circuit. For this reason, the capacitor element used in the solid electrolytic capacitor of the present invention can also function as a three-terminal noise filter. That is, when this solid electrolytic capacitor is mounted on a circuit board, an electric signal input from one of the opposing anode lead portions is filtered, and the electric signal is output to the other anode lead portion.

  Next, a mounting substrate on which the capacitor element used in the present invention is mounted will be described with reference to FIG. The mounting substrate 41 is based on an insulating substrate such as a rectangular glass epoxy substrate, and includes an anode terminal 42 and a cathode terminal 43 on the bottom surface, and an anode connected to the anode lead portion and the cathode lead portion of the capacitor element on the top surface, respectively. The conductor 44 and the cathode conductor 45 are provided, and the anode conductor 46 and the anode terminal 44 on the upper surface and the back surface are electrically connected to each other.

  Anode conductors 44 are disposed at the four corners of the capacitor element mounting surface of the mounting substrate 41. In the center portion, a cathode conductor 45 joined to the cathode lead portion of the capacitor element is formed in a square shape. On the other hand, on the mounting surface of the mounting substrate 41, four anode terminals 42 are formed at four corners, and cathode terminals 43 are arranged at the center. The anode conductor and anode terminal formed on both surfaces of the mounting substrate 41, and the cathode conductor and cathode terminal are electrically joined via electrodes 48 penetrating front and back such as via holes or through holes, respectively.

  The cathode terminal 46 of the mounting substrate 41 is preferably formed up to the end of the mounting surface of the mounting substrate 41. If the cathode terminal is formed up to the end of the mounting surface of the mounting board 41, when the capacitor is mounted on the printed board or the like by soldering, the conductive pattern of the printed board or the like, the anode terminal 42, and the cathode terminal 46 A solder fillet is formed between them, and the visibility of whether or not the soldering connection is surely made is improved. FIG. 3 shows an example in which such a cathode terminal 46 is formed up to the end of the mounting surface of the mounting substrate 41. The cathode terminal 46 formed at the end portion of the mounting substrate only needs to be electrically connected to the cathode terminal 46 formed at the center, and may have an apparently separated shape on the mounting surface.

  In such a mounting board, the length of the diagonal line is about 1.4 times the length of the vertical dimension or the horizontal dimension of the mounting board. If the transmission line is formed on the diagonal line, a transmission line having a length of about 1.4 times can be theoretically formed compared to the case where the transmission line is formed in parallel to the vertical and horizontal directions of the mounting substrate. However, even if the transmission line is formed, it is necessary to electrically connect the entrance and the exit of the transmission line. Considering the space for forming the anode conductor for connecting this transmission line, the length of the transmission line is 1.1 to 1.3 times the vertical dimension of the mounting substrate.

  When the distributed constant circuit is formed on the transmission line, the length of the distributed constant circuit is 1.0 to 1.2 times that in the case where the transmission line parallel to the two sides of the mounting substrate is formed. It is possible to form a distributed constant circuit having a length of.

  Here, the transmission line is constituted between the anode lead portions facing each other of the capacitor element, and the distributed constant circuit is constituted by a dielectric layer and a cathode electrode layer (solid electrolyte layer) serving as a capacitance forming portion of the capacitor element. . The length of the transmission line and the length of the distributed constant circuit can be changed depending on the shape and width of the capacitor element, and can be arbitrarily designed in consideration of the required capacitance and transmission line length.

  FIG. 11 shows an example in which the length of the transmission line and the length of the distributed constant circuit are made as long as possible by using the same mounting board. If the anode lead-out portion of the capacitor element is formed in a substantially triangular shape so as to match the corner of the element mounting surface of the mounting substrate, the length of the distributed constant circuit (the cathode electrode layer of the capacitor element (solid electrolyte layer) ) Can be formed longer.

  As the glass epoxy substrate serving as the base of such a mounting substrate, a substrate having a thickness of about 200 μm is suitable in terms of strength, but a substrate having a thickness of about 80 μm can also be used. And the conductor formed on a glass epoxy board | substrate should just have a small electrical resistance and can be soldered, and it is preferable to use copper and the conductor which plated gold on nickel. The thickness of this conductor can be 3 to 5 μm on one side. Further, the conductors and electrodes on both surfaces of the mounting substrate 41 and the through holes for electrically joining them can be formed by a method for producing a double-sided printed board that is frequently used in printed circuit boards. The arrangement of the through holes, the inner diameter, etc. at this time can be arbitrarily set.

  When viewed as a capacitor using such a mounting board, first, the distance from the anode lead part and cathode lead part of the capacitor element to the anode terminal and cathode terminal of the mounting board that is the outlet of current is the mounting board. This can be achieved with a distance of only the thickness of the current path, and the current path can be shortened. In particular, the thickness of the mounting substrate is preferably about 200 μm, and a thickness of about 80 μm can be manufactured. Therefore, the capacitor element has a capacitor element that is attached to the lead frame and is resin-molded. The distance from the cathode lead portion to the cathode terminal can be extremely shortened. Furthermore, by forming the anode terminal at four locations, the current path can be divided into four, and the substantial ESL can be reduced to ¼.

  That is, the capacitor of the present invention uses a method of reducing the length of the current path as much as possible and dividing the current path into n pieces to reduce the effective ESL to 1 / n. The effect is enhanced.

  Furthermore, since the cathode terminals 46 are formed on the four sides of the mounting surface of the mounting substrate 41, the degree of freedom of conduction with the GND line of the printed circuit board to be mounted can be increased. In addition, in the conventional solid electrolytic capacitor having a five-terminal structure, it was difficult to visually confirm whether the cathode terminal is securely soldered. A solder fillet is formed between the cathode terminal 46 and the visibility of whether it is securely connected by soldering is improved.

  Next, a process for mounting the capacitor element on the mounting substrate will be described. Here, an example in which the capacitor element 20 of the first embodiment is used as the capacitor element will be described.

  As shown in FIG. 2, the capacitor element 20 is mounted on the mounting substrate 41, and the cathode lead portion 22 of the capacitor element 20 and the cathode conductor 45 of the mounting substrate are joined by a conductive adhesive. Further, the anode lead portion 21 of the capacitor element 20 and the anode conductor 44 are connected. At this time, the anode lead portion 21 of the capacitor element 20 is aluminum, and the wettability with the silver paste or the like is not good, and adhesion with the silver paste may be difficult. In such a case, a connecting member 27 such as a copper material is connected to the anode lead portion 21 of the capacitor element 20 by laser welding, ultrasonic welding or the like, and this connecting member 27 is electrically conductive such as silver paste. It is preferable to join the anode conductor 44 of the mounting substrate 41 with an adhesive.

  Further, the number of capacitor elements mounted on the mounting substrate 41 is not limited to one. When a large capacitance is required, capacitor elements can be further stacked to achieve the required capacitance.

  Then, for the purpose of mechanical protection of the capacitor element mounted on the mounting substrate and shielding from the outside air, the exterior is formed by molding with an exterior resin. In addition, you may package an exterior by sticking to a board | substrate using a resin case.

20 Capacitor element 21 Capacitor element piece 22 Anode lead part 23 Cathode lead part 24 Separation part 25 Etching layer 26 Cathode layer 27 Connection member 30 Capacitor element 32 Anode lead part 33 Cathode lead part 34 Separation part 35 Etch layer 36 Cathode layer 41 Mounting Substrate 42 Anode terminal 43 Cathode terminal 44 Anode conductor 45 Cathode conductor 48 Through hole (electrode)

Claims (3)

A capacitor comprising a mounting surface that is surface-mounted on a printed circuit board on one side and an element mounting surface on which the capacitor element is mounted on the other side, and a capacitor element,
The mounting board has anode terminals at the four corners of the mounting surface and cathode terminals at the center, and an anode conductor that is electrically connected to the anode terminal at the four corners of the element mounting surface, and a cathode conductor that is electrically connected to the cathode terminal at the center. Are placed,
In the capacitor element, a capacitance forming portion, a cathode electrode layer, and a cathode lead portion are sequentially stacked at the center of the conductor, and an anode lead portion made of four conductors protruding from the periphery of the cathode lead portion is formed. ,
A capacitor having a transmission line structure formed by connecting the anode lead portion of the capacitor element to the anode conductor of the mounting substrate and the cathode lead portion of the capacitor element to the cathode conductor, and the conductor of the capacitor element located at the diagonal of the mounting substrate.   2. The capacitor according to claim 1, wherein the capacitor element is made of a rectangular conductor, and a plurality of capacitor element pieces each having an anode lead portion protruding from both ends of the cathode lead portion are stacked in a cross shape. The capacitor according to claim 1, wherein the capacitor element is made of a cross-shaped conductor, and the anode lead portion protrudes from the periphery of the cathode lead portion.