Capacitor

A capacitor includes a first capacitor element and a second capacitor element laminated on this first capacitor element. The first capacitor element is a solid electrolytic capacitor including a through-hole electrode penetrating a valve metal sheet and having one surface on which cathode and anode terminal portions are taken out. The second capacitor element has first and second electrodes which are provided via a dielectric layer, and second through-hole electrodes penetrating the dielectric layer. The second through-hole electrodes are coupled to the first electrode and insulated from the second electrode. Lead-out portions of the second electrodes are exposed from the dielectric layer. The second through-hole electrodes and the lead-out portions are disposed alternately. The first electrode is electrically coupled to the first through-hole electrode and the second electrode is electrically coupled to the valve metal sheet.

TECHNICAL FIELD

The present invention relates to a capacitor excellent in high-frequency property.

BACKGROUND ART

Recently, as electronic apparatuses have had higher functions, electronic components used therein have been demanded to have performance capable of corresponding to a high frequency range. For example, it is essential that a capacitor used as a bypass capacitor or a decoupling capacitor in a high frequency circuit should have a higher resonance frequency and a larger capacity. In order to obtain a higher resonance frequency, it is essential to reduce the equivalent series inductance (to lower ESL) of a capacitor. In particular, a decoupling capacitor used for CPU with significantly high performance is required to have performance capable of rapidly supplying a large electric power. In order to satisfy the requirement of such a high-speed operation, it is important to lower ESL of the capacitor.

A conventional capacitor excellent in high-frequency property is disclosed in, for example, Japanese Patent Unexamined Publication No. 2002-299152. On both ends of the disclosed ceramic capacitor, positive electrode terminals and negative electrode terminals are arranged alternately, thereby reducing ESL. In addition, a multilayer ceramic capacitor in which respective electrode terminals are arranged alternately in a matrix so as to reduce the inductance to lower ESL, is known. Such a capacitor is disclosed in, for example, Japanese Patent Unexamined Publication No. 2001-189234. Such capacitors have a devised electrode structure so that magnetic fields induced by electric current flowing in the capacitor can cancel each other. Furthermore, electric current path length in each of the electrode is shortened. The synergistic effect thereof reduces ESL.

However, since such a capacitor has a configuration in which the shape of internal electrodes and configuration of terminal electrodes are complicated, the capacity becomes smaller and the productivity is deteriorated.

SUMMARY OF THE INVENTION

A capacitor of the present invention includes a first capacitor element and a second capacitor element laminated on the first capacitor element. The first capacitor element includes a valve metal sheet, a dielectric film, a solid electrolytic layer, a collector layer, and a first through-hole electrode. On one side of the valve metal sheet, a porous layer is provided. The dielectric film is formed on the porous layer. The solid electrolytic layer is formed on the dielectric film. The collector layer is formed on the solid electrolytic layer. The first through-hole electrode conducts with the collector layer, is electrically insulated from the valve metal sheet, and penetrates the valve metal sheet. The second capacitor element includes a dielectric layer, a first electrode, a second electrode, a plurality of second through-hole electrodes and a plurality of lead-out portions of the second electrode. The first electrode and the second electrode are provided in such a manner as to be electrically insulated from each other via the dielectric layer. The first electrode is electrically connected to the first through-hole electrode, and the second electrode is electrically connected to the valve metal sheet. The second through-hole electrode is provided in such a manner as to penetrate the dielectric layer, to be coupled to the first electrode and electrically insulated from the second electrode. The lead-out portions of the second electrode are exposed from the dielectric layer. The second through-hole electrodes and the lead-out portions are arranged alternately. This capacitor is configured by combining the first capacitor element having a large electrostatic capacity and the second capacitor element having a low ESL property. Therefore, it is possible to obtain a capacitor securing a large capacity and having a low ESL property.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

First Exemplary Embodiment

FIG. 1is an outside perspective view showing a capacitor in accordance with a first exemplary embodiment of the present invention.FIG. 2Ais a sectional view showing a structure taken along line2A-2A ofFIG. 1.FIG. 2Bis an enlarged view showing a main part ofFIG. 2A.FIG. 2Cis an enlarged view showing a main part of an upper surface of another capacitor in accordance with the first exemplary embodiment.FIG. 3Ais a sectional view showing a structure of another example of a capacitor in accordance with the first exemplary embodiment.FIG. 3Bis a sectional view showing a structure of a further example of a capacitor.

InFIGS. 1,2A and2B, valve metal sheet (hereinafter, referred to as “sheet”)1has porous layer6, having a large number of pores, at the side of first surface1A. On the surface of porous layer6, dielectric film31is formed. These are formed by subjecting, for example, aluminum (Al) to treatment with a chemical solution and thermal oxidation. As sheet1, in addition to Al, tantalum (Ta) and niobium (Nb) are preferred from the viewpoint of electrostatic capacity.

On the surface of dielectric film31, solid electrolytic layer32is formed. InFIG. 2A, dielectric film31is not shown. On the surface of solid electrolytic layer32, collector layer7is formed. Collector layer7includes carbon layer33and cathode electrode layer9formed on carbon layer33. Cathode electrode layer9is made of silver (Ag) paste, and the like. Solid electrolytic layer32can be formed by a polymerization method of a conductive polymer such as polypyrrole, polythiophene, and the like. Carbon layer33is used in order to reduce the interface resistance between solid electrolytic layer32and cathode electrode layer9.

Furthermore, sheet1is provided with first through-hole electrode2penetrating sheet1from the side of first surface1A to the side of second surface1B opposing first surface1A. Through-hole electrode2electrically conducts with cathode electrode layer9. On the inner wall of a through hole in which through-hole electrode2is made and on the most part of the side of the second surface of sheet1, insulating film3is formed. Insulating film3insulates through-hole electrode2from sheet1electrically. Furthermore, anode-cathode separating portion8formed on the outer peripheral portion of the side of first surface1A of sheet1prevents solid electrolytic layer32and collector layer7from being brought into conduction with sheet1at the end thereof, so as to improve the reliability of the capacitor.

Reinforcing plate10attached to cathode electrode layer9enforces the entire mechanical strength. Anode-cathode separating portion8and reinforcing plate10are not essential components and they may be provided if necessary.

On an exposed surface of through-hole electrode2at the side of second surface1B of sheet1, cathode terminal4is formed. Insulating film3formed on second surface1B of sheet1has an opening in a part thereof. In this opening, anode terminal5conducting with sheet1is provided. Note here that terminals4and5are not necessarily required. However, by providing terminals4and5, the connection reliability is enhanced. With such a configuration, first capacitor element41is formed.

Next, a configuration of second capacitor element42is described. Capacitor element42is provided at the side of second surface1B of sheet1constituting capacitor element41. Firstly, lower electrode14made of a metal having an excellent conductivity, for example, copper (Cu), is formed by using, for example, a thin film process so that lower electrode14is connected to cathode terminal4of capacitor element41. Next, on lower electrode14, dielectric layer16made of a thin film of a dielectric material such as barium titanate, is formed by, for example, a sputtering method. Then, on dielectric layer16, upper electrode15is provided so that it is connected to anode terminal5of capacitor element41. Thus, lower electrode14, dielectric layer16and upper electrode15are laminated. In the case where terminals4and5are not provided, lower electrode14is directly connected to through-hole electrode2, and upper electrode15is directly connected to sheet1, respectively. That is to say, lower electrode14as a first electrode and upper electrode15as a second electrode are provided in such a manner as to be electrically insulated from each other via dielectric layer16. Lower electrode14is electrically coupled to through-hole electrode2and upper electrode15is electrically coupled to sheet1, respectively.

In the parts of dielectric layer16and upper electrode15, a through hole is provided. Second through-hole electrode18connected to lower electrode14is provided in this through hole. Insulating portion17provided on the inner wall of the through hole electrically insulates through-hole electrode18from upper electrode15. That is to say, through-hole electrode18is provided in such a manner as to penetrate dielectric layer16, to be coupled to lower electrode14and insulated from upper electrode15. On through-hole electrode18, first terminal electrode20, which is exposed to outer surface21A and coupled to through-hole electrode18, may be provided if necessary. On upper electrode15, second terminal electrode19, which is exposed to outer surface21A and coupled to a lead-out portion of upper electrode15, may be provided. Thus, capacitor element42is configured.

Capacitor element42is characterized by the arrangement of an electrode lead-out portion from upper electrode15and an electrode lead-out portion from through-hole electrode18coupled to lower electrode14, which are exposed to outer surface21A of insulating protective layer21. InFIG. 1, the electrode lead-out portions correspond to terminal electrodes19and20, respectively. Terminal electrodes19and20are provided so that they alternate with each other as shown inFIG. 1. In the case where terminal electrodes19and20are not provided, through-hole electrode18may be exposed to outer surface21A, and a protrusion integrated with upper electrode15may be provided on a place corresponding to terminal electrode19. With such a configuration, ESL of capacitor element42is extremely reduced.

A capacitor including capacitor elements41and42and having the above-mentioned configuration can be used as a decoupling capacitor for MPU and the like. In such an application of use, power supply ability that plays an important role in a rapid voltage change in MPU at the initial stage is determined depending upon the ESL property.

The capacitor that plays a role in a power supply necessary for the initial stage requires a low ESL property. The necessary electrostatic capacity is about 50 nF. Therefore, it is necessary that the electric current path length in capacitor element42in this exemplary embodiment be made to be as short as possible. Furthermore, designing is needed to be carried out by giving a high priority to the reduction of ESL property by devising the arrangement of terminal electrodes19and20. With the above-mentioned configuration of capacitor element42, such conditions can be satisfied. Designing the electrostatic capacity of capacitor element42to be about 50 nF enables power supply necessary for the initial stage.

On the other hand, for the power supply at the next stage, a large electrostatic capacity is required. To satisfy this requirement, capacitor element41supplies large amount of electric charges. Therefore, capacitor element41is needed to be a capacitor having reduced equivalent series resistance (low ESR) property and a large capacity. Since capacitor element41is a solid electrolyte capacitor, it is suitable for such an application requiring a large capacity.

As mentioned above, in the capacitor in accordance with this exemplary embodiment, capacitor element41has a large capacity and capacitor element42has a low ESL property. When the functions are assigned to each element in this way, it is possible to efficiently obtain a capacitor having a large capacity and a low ESL property without sacrificing electrostatic capacity. Furthermore, with such a configuration, it is possible to obtain an extremely thin capacitor used in the high frequency range. Note here that it is preferable that capacitor element42be formed as a thin film capacitor in which dielectric layer16and electrodes14and15are formed by a thin film formation method as mentioned above. This enables the pitch between terminal electrode19and terminal electrode20to be fine with high precision.

In the above-mentioned description, capacitor element42is directly formed on capacitor element41by using a thin film process. Other than this, another capacitor having the same function as that of capacitor element42has been produced separately, and the formed capacitor may be laminated on capacitor element41. In this case, the respective combinations between cathode terminal4and lower electrode14and between anode terminal5and upper electrode15are electrically connected by using an Ag paste, a Cu paste or an anisotropic conductive paste. At this time, when capacitor element41and capacitor element42are bonded to each other with an adhesive agent, and the like, the reliability is enhanced. In such a production process, since separately produced capacitor elements are laminated and bonded to each other finally, the yield of the final products can be increased.

When capacitor element42is made of an organic film capacitor, a capacitor excellent in stress resistance can be obtained. When capacitor element42is made of a ceramic capacitor, it is possible to obtain a capacitor having both low ESR property and low ESL property. When capacitor element42is made of a solid electrolytic capacitor, capacitor element42can be produced in the similar process to that of capacitor element41, so that it is possible to obtain a capacitor having a large capacity and excellent productivity.

Furthermore, as shown inFIG. 2C, it is preferable that connecting bumps36be provided on terminal electrodes19and20. When terminal electrodes19and20are not provided, connecting bumps36may be provided on through-hole electrode18and the lead-out portion of upper electrode15. Thus, a semiconductor device and capacitor element42can be directly connected to each other with the shortest distance. Consequently, the power supply performance in the high frequency range is enhanced. Furthermore, when the distance between terminal electrodes19and20in capacitor element42is made to be shorter than the distance between anode terminal5and cathode terminal4in capacitor element41, a capacitor excellent in low ESL property can be obtained.

When cathode terminal4and lower electrode14are connected to each other by soldering while anode terminal5and upper electrode15are connected to each other by soldering, the mounting property and reliability are improved. When cathode terminal4and lower electrode14are connected to each other by using a conductive adhesive agent while anode terminal5and upper electrode15are connected to each other by using a conductive adhesive agent, productivity is improved. The respective combinations between anode terminal5and upper electrode15and between cathode terminal4and lower electrode14may be connected by using an anisotropic conductive paste. Thus, terminal electrodes19and20can be arranged at a narrow pitch.

Furthermore, when sheet1is made of any of Al, Ta and Nb, a capacitor having a large capacity can be obtained by using a conventional technology. When anode terminal5, cathode terminal4, and terminal electrodes19and20are formed of a conductive paste containing Ag, Cu, a mixture of Ag and Cu, or an alloy of Ag and Cu, as a main component, productivity is improved. If necessary, they may be made of separate materials.

Next, a configuration of a capacitor of another example in accordance with this exemplary embodiment is described with reference toFIG. 3A. Herein, a capacitor shown inFIG. 3Ais different from the capacitor shown inFIG. 1in that substrate11is provided between capacitor elements41and42. Also inFIG. 3A, the same as inFIG. 2A, a dielectric film is not shown.

Substrate11includes first penetrating electrode12and second penetrating electrode13. Penetrating electrode13is provided so as to be connected to lower electrode14. Dielectric layer16is provided on lower electrode14. Upper electrode15is provided on dielectric layer16, and is connected to penetrating electrode12. Cathode terminal4and anode terminal5are connected to penetrating electrodes13and12, respectively. That is to say, through-hole electrode2and lower electrode14are electrically coupled to each other via penetrating electrode13. Sheet1and upper electrode15are electrically coupled to each other via penetrating electrode12. Terminal electrodes19and20of capacitor element42are arranged in the same way as inFIG. 2A. Thus, by coupling the capacitor elements that satisfy the respective properties, the yield can be improved. When such capacitors are produced, capacitor element42has been formed on substrate11, and then this connected product is coupled to and mounted on capacitor element41.

When an electrically insulating material is used for substrate11, capacitor element42can be formed on substrate11by a thin film formation method. After the properties of capacitor element42are examined, capacitor element42is mounted on capacitor element41while the properties are ascertained. Thus, a capacitor having desired properties can be effectively obtained with high precision. Furthermore, when insulating substrate11is made of an organic material, productive efficiency is improved. The use of an organic material including at least one of polyimide resin, epoxy resin, phenol resin, silicon resin, and the like, improves the reliability and productivity.

Substrate11may be made of an inorganic material. When substrate11is made of an insulating material including any one of alumina, glass, quartz and ceramic, a capacitor having a high reliability such as thermal resistance can be obtained.

On the other hand, as shown inFIG. 3B, substrate11may be made of conductive metallic materials such as Cu, Ag, silicon (Si), and the like. In this case, the expansion coefficient of substrate11becomes similar to that of sheet1in capacitor element41that is similarly made of a metallic material. As a result, not only the reliability but also the heat dissipation property is improved. Also inFIG. 3B, as inFIG. 2A, a dielectric film is not shown.

Furthermore, substrate11is made of a conductive material, one of penetrating electrodes12and13can be omitted. As shown inFIG. 3B, for example, penetrating electrode13becomes unnecessary. However, it is necessary to provide insulating film37so as to prevent upper electrode15and penetrating electrode12from conducting with substrate11. Such a configuration can be obtained as follows. That is to say, for example, Cu substrate is used as substrate11, and substrate11is provided with a through hole by dry etching. Then, lower electrode14and dielectric layer16are formed sequentially on substrate11by a technique such as sputtering, vapor deposition, and the like. At this time, insulating film37is formed by forming a part of dielectric layer16inside the through hole and on the periphery of the through hole. Next, inside the through hole, penetrating electrode12is formed by using an Ag nanopaste, and the like. Finally, upper electrode15is formed by a technique such as sputtering, vapor deposition, and the like. Thus, capacitor element42can be made as a lamination in a form of a uniform thin film. Alternatively, as mentioned below, through holes for forming penetrating electrodes12and13are formed, followed by thermal treatment oxidation. Thereby, an insulating film made of oxide may be formed on the surface of substrate11.

In the capacitors shown inFIGS. 3A and 3B, when substrate11and capacitor element41are bonded to each other with an adhesive agent, productivity is improved.

Hereinafter, one example of a method for manufacturing the capacitor shown inFIG. 3Ais described. Firstly, a method for manufacturing capacitor element41is described with reference toFIGS. 4 and 7.

Firstly, sheet1having porous layer6on first surface1A thereof is prepared. Porous layer6can be obtained by subjecting sheet1made of, for example, Al to acid treatment and thermal oxidation treatment. With such treatments, dielectric layer31is also formed on the surface of porous layer6. Then, sheet1is provided with through hole2A by, for example, a punching process. Next, insulating material3A made of a resin material is applied on sheet1from the side of second surface1B. At this time, resin material3A is also filled in the inside of through hole2A in addition to the surface of sheet1at the side of second surface1B. Then, as shown inFIG. 4, air is injected from the side of first surface1A of sheet1so as to remove an excessive portion of resin material3A in through hole2A. Thereby, through hole2A is made to be thirled again. Then, resin material3A is hardened by heating. Insulating film3inFIG. 3Acan be formed in this way.

Thereafter, as shown inFIG. 5, resin is applied and hardened on the peripheral portion at the side of first surface1A of the sheet1so as to form anode-cathode separating portion8, if necessary. Furthermore, solid electrolytic layer32is formed on dielectric layer31by a chemical polymerization method, an electrolytic polymerization method, or the like for a conductive polymer film such as polythiophene. On solid electrolytic layer32, a carbon paste is coated and hardened so as to form carbon layer33.

Thereafter, as shown inFIG. 6, an Ag paste is coated on carbon layer33and filled in through hole2A. Thus, through-hole electrode2and cathode electrode layer9are formed. At this time, if necessary, conductive reinforcing plate10made of Ag, Cu, or the like, may be attached to cathode electrode layer9with an Ag paste. Thus, the mechanical strength of capacitor element41is improved and the resistance value is reduced, thereby facilitating the extraction of electric charges.

Next, a predetermined position of insulating film3is processed by, for example, laser processing so as to form anode opening5A and allow the surface layer of sheet1to be exposed. Thereafter, as shown inFIG. 7, terminals4and5are formed on the exposed surface of through-hole electrode2and anode opening5A by, for example, plating. As mentioned above, capacitor element41can be formed.

Next, a method for producing capacitor element42on substrate11is described with reference toFIGS. 8 to 13. Firstly, substrate11that is a Si plate is provided with patterned resist (not shown). Then, through holes12A and13A are formed on predetermined sites by, for example, dry etching. Then, substrate11is oxidized by thermal treatment, so that an SiO2insulating film (not shown) is formed on substrate11. Next, as shown inFIG. 8, an Ag nanopaste and the like is filled in through holes12A and13A, and hardened. Thus, penetrating electrodes12and13are formed.

Next, as shown inFIG. 9, lower electrode14made of Cu, dielectric layer16containing barium titanate as a main component, and upper electrode15made of Cu are sequentially formed by, for example, a sputtering method. Each of them is formed in a predetermined shape by limiting a film formation site by using a metal mask, or by forming a film on the entire surface, followed by forming into a predetermined shape by a photolithography method or an etching method.

Thereafter, as shown inFIG. 10, blind via18A is formed in a predetermined position. Blind via18A is formed by laser processing or etching. As shown inFIG. 11, insulating portion17is formed on the inner wall of blind via18A. Insulating portion17can be formed by provisionally hardening photosensitive polyimide or the like, followed by really hardening by carrying out exposing and developing so that the polyimide remains on only a predetermined position.

Next, as shown inFIG. 12, an Ag paste or a Cu paste is filled by printing in blind via18A and hardened so as to form through-hole electrode18. Then, as shown inFIG. 13, terminal electrodes20and19are formed on through-hole electrode18and on the predetermined site of upper electrode15, respectively. Thus, capacitor element42is manufactured. Terminal electrodes19and20can be formed by a sputtering method, a photolithography method, or an etching method.

Capacitor elements41and42mentioned above are laminated and coupled to each other via substrate11. At this time, cathode terminal4and lower electrode14are coupled in such a manner as to conduct with each other via penetrating electrode13, and anode terminal5and upper electrode15are coupled in such a manner as to conduct with each other via penetrating electrode12, respectively with a paste or the like. Thus, the capacitor is completed. Furthermore, if necessary, as shown inFIG. 3A, by forming insulating protective layer21, a capacitor having an improved reliability and validity can be produced.

As mentioned above, in the capacitor in accordance with this exemplary embodiment, capacitor element42realizes a low ESL property and capacitor element41secures a large capacity. Therefore, a capacitor excellent in a high-frequency property can be obtained. In this way, by combining capacitor elements having different properties, a capacitor can be used for various applications. That is to say, each of these capacitor elements has a through-hole electrode inside thereof, so that opposite flows of electrical current are induced. Therefore, magnetic fields generated by electrical currents can cancel by themselves. Thus, the value of ESL caused by magnetic field can be minimized. In particular, since capacitor element42has a plurality of through-hole electrodes18, this effect can be achieved significantly. By combining such a capacitor element42and capacitor element41having a large capacity, the capacitor can be applied to electronic apparatuses requiring highly precise mounting technology.

Second Exemplary Embodiment

FIG. 14is a sectional view showing a capacitor in accordance with a second exemplary embodiment of the present invention. Capacitor element41is the same as in the first exemplary embodiment. Capacitor element43that is a second capacitor element is different from capacitor element42of the first exemplary embodiment in that capacitor element43has a laminated structure. Also inFIG. 14, as inFIG. 2A, a dielectric film is not shown.

In capacitor element43, inner layer electrodes34that are first electrodes and inner layer electrodes35that are second electrodes are provided in an inner layer of dielectric layer16. In other words, inner layer electrodes34and inner layer electrodes35are formed alternately via dielectric layer16. Second through-hole electrodes22conduct with inner layer electrodes34. Third through-hole electrodes (hereinafter, referred to as “through-hole electrodes”)23conduct with inner layer electrodes35and are insulated from inner layer electrodes34. Through-hole electrodes22and23penetrate dielectric layer16macroscopically. Inner layer electrodes34and35are patterned so that they are not short-circuited via through-hole electrodes22and23. InFIG. 14, each of through-hole electrodes22seems to be separated from each other. However, they are electrically coupled with each other via inner layer electrodes34. At the side of outer surface21A of each of inner layer electrodes34and35, terminal electrodes19and20are provided respectively.

Any of through-hole electrodes23is coupled to anode terminal5of capacitor element41, and any of through-hole electrodes22is coupled to cathode terminal4. Therefore, inner layer electrodes34are coupled to anode terminal5of capacitor element41, and inner layer electrodes35are coupled to cathode terminal4.

By laminating and connecting laminated capacitor element43having such a configuration and capacitor element41, a larger capacity and lower ESR can be achieved. Therefore, a capacitor having more excellent properties can be obtained. An example of capacitor element43having such a laminated configuration can include a thin film capacitor, an organic film capacitor, a laminated ceramic capacitor, and the like.

INDUSTRIAL APPLICABILITY

A capacitor of the present invention is excellent in productivity and enables low ESL and a large capacity. Therefore, the capacitor can be applied to electronic apparatuses, for example, a decoupling capacitor for MPU or the like which requires a low impedance property.