JP5642508B2 - Surface mount thin capacitors - Google Patents

Description

  The present invention relates to a surface-mount thin capacitor formed by laminating a plurality of capacitor elements, and more particularly to an electrical connection structure of capacitor elements for low equivalent series resistance (low ESR).

  As the frequency of semiconductor devices increases, surface mount thin decoupling capacitors mounted on printed wiring boards for electronic components and electrical components are increasingly required to have low ESR from the market. In order to achieve low ESR in a surface-mounted thin capacitor composed of laminated capacitor elements having a plate-like or foil-like expanded valve metal as an anode body, the components of each capacitor element or It is necessary to reduce the specific resistance of the material, and when capacitor elements are stacked and connected in parallel, the cathode part on the outer periphery of each capacitor element must be connected with low resistance over the entire electrode.

  FIG. 3 is a perspective view of a conventional surface-mount thin capacitor element, showing an example of the internal structure. 4 is a cross-sectional view of the conventional surface-mount thin capacitor element shown in FIG. 3. FIG. 4 (a) is a cross-sectional view along the line AA, and FIG. 4 (b) is along the line BB. FIG. In FIG. 3, the portion of the conductive adhesive applied to the side surface is hatched. Such a surface-mount thin capacitor is disclosed in Patent Document 1, for example. 3 and 4, a plate-like or foil-like expanded valve action metal is used as an anode body 1, a dielectric layer formed on the surface of the anode body, and a solid electrolyte layer formed on the dielectric layer. A plurality of capacitor elements each including a conductive polymer layer 3, a graphite layer 4 formed on the surface of the conductive polymer layer 3, and a silver layer 5 which is a conductor layer formed on the surface of the graphite layer 4. It is configured by laminating pieces. A resist layer 2 is formed on both sides of the conductive polymer layer 3 formed on the anode body 1 of the capacitor element, and a metal plate 6 is connected to the end of the anode body 1 to form an anode section 8. ing.

  The manufacturing process of this surface mount thin capacitor will be described with reference to FIG. First, a plate-shaped or foil-shaped expanded valve metal is used as the anode body 1, and an oxide film serving as a dielectric layer is formed on the surface using an anodic oxidation method or the like. A conductive polymer layer 3 is formed on the central portion 1a of the anode body 1 so as to cover the surface oxide film. Thereafter, a graphite layer 4 and a silver layer 5 made of silver paste are sequentially formed on the surface of the conductive polymer layer 3 to form a cathode conductor layer.

  On the other hand, with respect to the portions where the cathode conductor layers at both ends of the anode body 1 are not formed, first, the resist layer 2 mainly composed of an insulating resin is applied to the adjacent portions 1b adjacent to both ends of the conductive polymer layer 3. Form. Thereafter, a metal plate 6 is connected by welding to both end portions 1c of the anode body 1 extending further outward from the portion where the resist layer 2 is formed to form an anode portion 8 to obtain a capacitor element.

  Next, a plurality of capacitor elements are stacked to form a laminated structure, and a conductive adhesive 9 is applied between the silver layers 5 of each capacitor element, and each is electrically connected. At this time, the conductive adhesive 9 is applied not only to the opposing surfaces in the direction in which the silver layers 5 are laminated, but also to the side surfaces to electrically connect the capacitor elements. For the anode portion 8 as well, the laminated body shown in FIG. 4 is completed by connecting the anode body 1 and the metal plate 6 at both ends of each capacitor element overlapped with each other by welding or the like. Each is connected to an external terminal and an exterior case is installed to complete a surface mount thin condenser.

JP 2006-128247 A

  However, as described above, the conventional technique applies a conductive adhesive not only to the opposing surfaces in the stacking direction of the silver layers of each capacitor element, but also to the side surfaces, so that the silver layers of each capacitor element are connected in parallel. There is a problem that it is insufficient for lowering ESR. In this situation, the present invention is to provide a surface mount thin capacitor further reducing ESR.

In order to solve the above-mentioned problems, the surface mount thin capacitor of the present invention has a plate-like or foil-like expanded valve action metal as an anode body, a dielectric layer formed on the surface of the anode body, A conductive polymer layer to be a solid electrolyte layer formed on the surface of the dielectric layer, a graphite layer formed on the surface of the conductive polymer layer, and a silver layer which is a conductor layer formed on the surface of the graphite layer A thin-film surface-mounted capacitor in which capacitor elements are stacked, wherein the stacked silver layers are in a gap state, and at least a part of the outer periphery of the silver layer is covered with a conductive tape, The silver layers are electrically connected to each other.

  In the surface mount thin capacitor of the present invention, when capacitor elements are stacked and the silver layers are electrically connected, at least a part of the outer peripheral portion of the silver layer of the stacked capacitor elements is covered and connected with a strip-shaped conductive member. Thus, the connection resistance of each capacitor element can be reduced, so that a surface mount thin capacitor having a low ESR can be obtained as compared with the surface mount thin capacitor of the prior art.

  Further, since the connection resistance of each capacitor element can be reduced, it is desirable to use a conductive tape provided with a conductive adhesive on a metal foil or a metal foil obtained by applying a conductive adhesive to the conductive member.

  Furthermore, a gap is formed between the laminated silver layers, and at least a part of the outer periphery of the silver layer is covered with the above-described conductive tape, and the silver layers are electrically connected, thereby connecting each capacitor element. The resistance can be reduced, so that a surface mount thin capacitor with low ESR can be obtained as compared to the surface mount thin capacitor of the prior art. Further, by not applying a conductive adhesive between the silver layers, it is possible to reduce materials used and product costs.

1 is a perspective view showing a three-terminal surface-mount thin capacitor element according to a first embodiment of the present invention. 2A and 2B are cross-sectional views of the surface-mount thin capacitor element of FIG. 1, in which FIG. 2A is a cross-sectional view along the line AA, and FIG. 2B is a cross-sectional view along the line BB. The perspective view which showed the conventional surface mount thin capacitor | condenser element. 4A and 4B are cross-sectional views of the surface-mounted thin capacitor element of FIG. 3, in which FIG. 4A is a cross-sectional view along the line AA, and FIG. 4B is a cross-sectional view along the line BB.

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

(Embodiment 1)
FIG. 1 is a perspective view showing a three-terminal surface-mount thin capacitor element according to the first embodiment of the present invention. FIG. 2 (a) is a sectional view taken along the line AA, and FIG. ) Is a cross-sectional view along the line BB. In FIG. 1, the conductive tape 7 is hatched. In FIG. 1 and FIG. 2, a plate-like or foil-like expanded valve action metal is used as an anode body 1 as in a conventional surface-mount thin capacitor, and a dielectric layer formed on the anode body surface, A conductive polymer layer 3 which is a solid electrolyte layer formed on the surface of the body layer, a graphite layer 4 formed on the surface of the conductive polymer layer 3, and a conductor layer formed on the surface of the graphite layer 4. A plurality of capacitor elements composed of a certain silver layer 5 are laminated, and the outer peripheral portion of the silver layer 5 of the laminated capacitor elements is covered with a conductive tape 7 and electrically connected. Note that metal plates 6 are connected to both outer ends of the anode body 1 of each capacitor element.

  The capacitor of the present embodiment is manufactured as follows. First, a plate-like or foil-like valve action metal is chemically or electrochemically etched in a chloride aqueous solution such as hydrochloric acid to form an infinite number of pores to increase the surface area. By the method or by pressing and molding the valve metal processed into a plate or foil shape from both sides with the same metal powder of the same valve action and then sintering in high temperature vacuum, An anode body 1 having a porous layer having a thickness of 10 to 300 μm at the center is formed. Here, aluminum, tantalum, niobium, or the like can be used as the valve metal.

  A capacitor element used in the three-terminal solid electrolytic capacitor of the present invention will be described mainly with reference to FIG. An aluminum foil having a thickness of 100 to 200 μm was put into a hydrochloric acid bath and subjected to electrochemical etching to enlarge the surface area to about 200 times, and a porous layer having a depth of about 40 μm was provided on the surface. A foil-like anode body 1 is formed.

  Next, an oxide film to be a dielectric layer is formed on the surface of the porous layer of the central portion 1a of the anode body 1 by using an anodic oxidation method or the like. For example, a chemical conversion treatment can be performed by using an electrochemical method to form an oxide film serving as a dielectric layer. Next, a resist layer 2 is formed on the surface of the adjacent portion 1b on both sides of the central portion 1a using an insulating resin. For the formation of the resist layer 2, for example, an insulating resin based on an epoxy resin can be used.

  Further, the conductive polymer layer 3 is formed so as to cover the central portion 1a of the anode body 1 on which the oxide film is formed, and the graphite layer 4 is further formed on the surface. For example, the conductive polymer layer 3 made of polypyrrole can be formed by chemical polymerization, and the graphite layer 4 can be formed on the surface by screen printing.

  Subsequently, the silver layer 5 is formed by a method such as printing or transfer using a silver paste so as to cover a portion where the graphite layer 4 is formed.

  Furthermore, the metal plate 6 is connected to both end portions 1c of the anode body 1 by a method such as resistance welding, laser welding, or ultrasonic welding to form the anode portion 8 to obtain a capacitor element. Here, copper, a copper-based alloy, or the like can be used as the metal plate 6, but the metal plate 6 is not limited to this as long as it is a plate material made of a material that can be used as a terminal of an electronic component.

  Thereafter, a plurality of conductive adhesives 9 such as silver paste are applied and laminated on the surface of the silver layer 5 to which each capacitor element is connected, and the outer peripheral portion of the laminated silver layer 5 is used with the conductive tape 7. Cover and electrically connect the silver layer 5. Thereafter, heating is performed at 100 to 300 ° C. while pressing the stacked body in the stacking direction, and the conductive adhesive applied between the silver layers 5 of the stacked capacitor elements is cured.

  In addition, it is desirable to make the ratio which covers the outer peripheral part of the silver layer 5 with the conductive tape 7 as large as possible from the point of contributing to ESR reduction. Here, the conductive tape is obtained by applying a conductive pressure-sensitive adhesive to a metal foil such as copper, silver, and aluminum, and any material can be used as long as it has excellent conductivity and satisfies heating conditions, adhesive strength, and the like. .

  Furthermore, with respect to the anode portion 8, the anode bodies 1 are connected to each other via the metal plate 6 at both ends of the laminated capacitor elements. Here, the connecting method of the anode body 1 and the metal plate 6 includes laser welding, electron beam welding, resistance welding, and the like. Then, an anode terminal and a cathode terminal are connected to an external terminal, and an exterior case is installed.

  As described above, the outer peripheral portion of the silver layer of the laminated capacitor element is covered with a conductive tape, and the silver layer is electrically connected, so that the ESR is further reduced as compared with the conventional laminated capacitor. Is completed.

(Embodiment 2)
Next, a mode in which the outer peripheral portion of the laminated silver layers is covered with a metal foil and the silver layers are electrically connected will be described.

  The same process as in the first embodiment is performed until the anode body is subjected to the above-described treatment to form the cathode portion and the silver layer of the capacitor element is laminated via the conductive adhesive. As the metal foil, a gold foil, silver, copper, aluminum, or the like having good spreadability and excellent conductivity is used.

  The connection between the silver layer and the metal foil is performed in a state where a conductive adhesive in which a conductive filler is dispersed is applied to the connection surface of the metal foil in advance in order to ensure sufficient electrical connection. The metal foil coated with the conductive adhesive is used to cover the outer periphery of the laminated silver layers, the silver layers are electrically connected, and finally fixed by heating. The conductive adhesive may be applied to the outer peripheral surface of the laminated silver layer. As the conductive adhesive, one having a conductive filler such as silver, gold, copper, or carbon is used. Therefore, you may use the same thing as the electroconductive adhesive used for connecting between the laminated | stacked silver layers.

  Subsequently, a metal plate is disposed in the same manner as in the first embodiment, and after forming an anode portion by welding, the anode terminal and the cathode terminal are connected to an external terminal, and an outer case or the like is installed.

  In this way, by covering the outer periphery of the silver layer of the laminated capacitor element with a metal foil coated with a conductive adhesive and electrically connecting the silver layer, the ESR can be further increased than the conventional laminated capacitor. A reduced surface mount thin capacitor is completed.

(Embodiment 3)
Next, a description will be given of a mode in which gaps are formed between the laminated silver layers, and at least a part of the outer peripheral portion of the silver layer is covered with the above-described conductive tape to electrically connect the silver layers.

  The same processes as those in the first embodiment are performed until the anode portion is subjected to the above-described treatment to form a cathode portion and a capacitor element is obtained. After that, the capacitor element is laminated by placing a metal plate at the end of the anode body and forming and fixing the anode part by welding. Between the silver layers to be laminated, there is no gap between the conductive adhesives. Leave as it is.

  Next, the outer peripheral portion of the laminated silver layer 5 is covered with the same conductive tape as in the first embodiment, and the silver layers are electrically connected. Thereafter, the laminated body is pressurized in the laminating direction to enhance and fix the adhesion between the silver layer of the laminated capacitor element and the conductive tape.

  Subsequently, after arranging the metal plate and forming the anode part by welding in the same manner as in the first embodiment, the anode terminal and the cathode terminal are connected to the external terminal, and the exterior case and the like are installed.

  In this way, with the gap between the silver layers of the laminated capacitor elements, the silver layer is electrically connected by covering at least part of the outer periphery of the silver layer with the conductive tape described above. Thus, a surface mount thin capacitor with a further reduced ESR than the capacitor laminated by the conventional technology is completed.

  Up to this point, three forms have been described, but it is possible to replace the conductive tape in the structure of Embodiment 3 with metal foil, and the selection of these structures, conductive tape, and metal foil is required for the product. It is desirable to decide in consideration of the ESR level and cost.

Example 1
The capacitor element used in the three-terminal solid electrolytic capacitor of the present invention will be specifically described mainly with reference to FIG.

An aluminum foil having a length of 15 mm, a width of 10 mm, and a thickness of 150 μm was placed in a hydrochloric acid bath and electrochemically etched to form a foil-like anode body 1 having a porous layer.

  Next, an oxide film serving as a dielectric layer is formed on the surface of the porous layer of the central portion 1a of the anode body 1 by using an anodic oxidation method, and an epoxy resin is used on the surfaces of the adjacent portions 1b on both sides. Layer 2 was formed.

  Then, the conductive polymer layer 3 was formed, and the graphite layer 4 and the silver layer 5 were sequentially formed on the surface.

  Subsequently, a metal plate 6 was connected to both end portions 1c of the anode body 1 by resistance welding to form an anode portion 8 to obtain a capacitor element. Further, a conductive adhesive 9 of silver paste was applied and laminated on the opposing surfaces of the silver layer 5 of each capacitor element.

  And the outer peripheral part of the laminated | stacked silver layer 5 is covered using the electrically conductive tape 7 which consists of a copper foil base material and a conductive adhesive and is 70 micrometers in thickness and 3.0 mm in width, and the silver layer 5 is electrically Connected. Then, it heated at 150 degreeC for 1 hour, pressing in the lamination direction, and the electroconductive adhesive of the silver layer 5 was hardened. In addition, the ratio which covered the outer peripheral part of the silver layer 5 with the conductive tape 7 was 30% of the area of the outer peripheral part.

  Then, each anode body 1 and the metal plate 6 were connected by resistance welding, and finally, the anode terminal and the cathode terminal were connected to external terminals, and an exterior case was installed.

  As described above, the surface mount thin capacitor in which the outer peripheral portion of the silver layer of the laminated capacitor element was covered with the conductive tape, the silver layer was electrically connected, and the ESR was further reduced was completed. The number of samples produced is 50.

(Example 2)
Subsequently, using a copper foil having a thickness of 5 μm, a sample in which the outer peripheral portion of the silver layer of the laminated body was covered and the silver layer was electrically connected was produced. The silver layer and the copper foil were previously coated with a conductive adhesive on the connection surface of the copper foil in order to ensure sufficient electrical connection. Other manufacturing conditions and components were the same as in Example 1. 50 samples were also produced.

Example 3
Subsequently, at least a part of the outer periphery of the silver layer was covered with the same conductive tape as in Example 1 in a state of a gap between the silver layers of the laminated capacitor elements, and the silver layers were electrically connected. A sample was made. Then, the adhesiveness of the laminated | stacked capacitor | condenser element silver layer and an electroconductive tape was improved and fixed by pressing a laminated body in the lamination direction. Other manufacturing conditions and components were the same as in Example 1. 50 samples were also produced.

(Comparative example)
For comparison, 50 solid electrolytic capacitors having a conventional structure in which a conductive adhesive was applied to the side surface of the laminated silver layer were prepared. In addition, it was set as the Example except the outer peripheral part of the laminated | stacked silver layer not connecting with an electroconductive tape or metal foil. 50 samples of comparative examples were produced.

  Table 1 shows the ESR measurement results of the examples according to the present invention and the comparative examples. ESR was measured using a known method. The number of measurements was 50 each.

  When the ESR of the sample of the example and the comparative example prototyped by the above method is compared, the average value of ESR equal to or higher than that of the comparative example is obtained even in the example 3 having the largest ESR in the example, and the ESR is smallest In Example 1, it became possible to reduce the average value of ESR by 10% compared with the comparative example.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to these embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 Anode body 1a Center part 1b Adjacent part 1c Both-ends part 2 Resist layer 3 Conductive polymer layer 4 Graphite layer 5 Silver layer 6 Metal plate 7 Conductive tape 8 Anode part 9 Conductive adhesive

Claims (1)

  A plate-like or foil-like expanded valve metal is used as an anode body, a dielectric layer formed on the surface of the anode body, and a conductive polymer layer serving as a solid electrolyte layer formed on the surface of the dielectric layer A surface mount thin capacitor in which a capacitor element comprising a graphite layer formed on the surface of the conductive polymer layer and a silver layer which is a conductor layer formed on the surface of the graphite layer is laminated. A surface mount thin capacitor characterized in that a gap is formed between the silver layers, and at least a part of the outer peripheral portion of the silver layer is covered with a conductive tape, and the silver layers are electrically connected to each other. .

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