JP2010219128A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thinned solid electrolytic capacitor of low self inductance and excellent reliability in moisture resistance. <P>SOLUTION: A capacitor element 14 and an electrode substrate 15 are electrically connected together through a conductive bond 16. A sealing layer 13 is formed in the exposed portion of an insulating layer 10 on the outside terminal side of the electrode substrate 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolytic capacitor, and more particularly to a three-terminal type and a two-terminal type solid electrolytic capacitor having a chip shape.

  In recent years, there has been a tendency to increase the operating frequency of electric signals flowing in circuit boards mounted on digital devices, and with the increase in operating frequency, the supply current in power supply circuits for driving electric signals increases. There is a tendency. On the other hand, output voltages of power supply circuits tend to decrease due to high integration of ICs (integrated circuits) and LSIs (large scale integrated circuits) mounted on circuit boards. As a result, the margin on the circuit board side with respect to noise (power supply noise) such as drive power supplied from the power supply circuit has been reduced, and therefore noise countermeasures have been emphasized. In general, it is effective to use a capacitor to remove power supply noise and the like, and a method using a capacitor as a noise removing device is known.

  In order to cope with an increase in operating frequency, a low impedance capacitor is desired in the high frequency region, but in general, a solid electrolytic capacitor tends to have a large increase in impedance in the high frequency region. The impedance of the solid electrolytic capacitor in the high frequency region is mostly due to its self-inductance, and this increase in impedance is mostly due to the self-inductance of the terminal portion of the solid electrolytic capacitor. This self-inductance in the high frequency region is expressed as an equivalent series inductance (hereinafter referred to as ESL), and the impedance in the high frequency region decreases as the value of ESL decreases.

  Under such circumstances, the capacitors described in Patent Document 1 and Patent Document 2 have been proposed as methods for reducing the self-inductance by shortening the distance between the capacitor element and the external terminal.

  In Patent Document 1, a double-sided copper-clad plate is used, and plating is performed by forming a through hole in order to electrically connect the element-side cathode terminal and the external cathode terminal. As a result, restrictions due to the thickness of the plating layers on both sides and the copper foil are added, and there is a limit in reducing self-inductance.

  On the other hand, in the example of Patent Document 2, since the capacitor element is directly joined to the external terminal through the through hole of the second insulating layer, the connection distance between the capacitor element and the external terminal is shortened, and the self-inductance is further reduced. It is possible. However, because of the structure, the first insulating layer is formed outside the external terminal, and it is necessary to make the solder thicker when mounting, so that it is difficult to mount and thinning is also difficult.

JP 2002-134359 A JP 2003-158042 A

  In order to reduce the self-inductance in the high-frequency region and improve the mountability and thinning, the present inventors previously described an electrode substrate as shown in the sectional view of the solid electrolytic capacitor in FIG. 7 in Japanese Patent Application No. 2008-106367. The insulation layer and the metal layer are made one layer at a time, and the capacitor element and the external cathode terminal are directly conductively bonded through the opening of the insulation layer, so that the distance between the capacitor element and the external terminal is shortened, and the self-inductance is low. We have proposed a thin solid electrolytic capacitor with excellent properties.

  Here, in the solid electrolytic capacitor shown in FIG. 7, the thinner the insulating layer, the shorter the distance between the capacitor element and the external terminal, and the thinner the capacitor becomes. However, by making the insulating layer thin, oxygen, water vapor, and the like are likely to permeate, and in particular, moisture resistance reliability may be easily lowered.

  An object of the present invention is to provide a thin solid electrolytic capacitor having a low self-inductance in a high frequency region and higher moisture resistance reliability.

  In the present invention, the metal layer of the electrode substrate with the metal layer attached only to the lower surface is used as the external electrode terminal, and the insulating layer portion is formed by forming the sealing layer in the portion where the insulating layer on the external electrode terminal side is exposed. It was found that a solid electrolytic capacitor excellent in moisture resistance reliability can be obtained by suppressing the intrusion of moisture from water.

  That is, the solid electrolytic capacitor of the present invention comprises a base material made of a plate-like or foil-like valve action metal having an enlarged surface, and a dielectric made of an oxide formed on the enlarged surface of the base material. An anode body composed of a body layer, a cathode conductor portion connected to the central portion of the anode body, and a capacitor element having anode leads connected to both end portions of the anode body, and a central portion and both end portions An insulating layer provided with an opening, an external cathode terminal formed of a metal layer covering the lower surface of the opening, formed at the center of the lower surface of the insulating layer, and formed at both ends of the lower surface of the insulating layer. And an electrode substrate having an external anode terminal made of a metal layer covering the lower surface of the opening, via the conductive adhesive formed in the opening, the cathode conductor portion, the external cathode terminal, and the Anode lead, external anode terminal, and Each is electrically connected, and having a sealing layer on the exposed portion of the lower surface of the insulating layer.

  The solid electrolytic capacitor of the present invention comprises a base material made of a plate-like or foil-like valve action metal having an enlarged surface, and an oxide formed on the surface of the base material that has been enlarged. An anode body composed of a dielectric layer; a capacitor element connected to one end of the anode body to form a cathode conductor portion; and a capacitor element connected to the other end of the anode body to form an anode lead; and one end An insulating layer having openings at the first and second ends, an external cathode terminal formed at one end of the lower surface of the insulating layer and covering the lower surface of the opening, and a lower surface of the insulating layer. An electrode substrate having an external anode terminal formed of a metal layer covering the lower surface of the opening is formed on the other end portion, and the cathode conductor portion and the electrode substrate via a conductive adhesive formed on the opening An external cathode terminal, and the anode lead and the external anode terminal, respectively It is electrically connected, and having a sealing layer on the exposed portion of the lower surface of the insulating layer.

  Further, the insulating layer is made of polyimide. Further, the opening is formed by chemical etching.

  According to the present invention, the insulating layer and the metal layer of the electrode substrate are formed one layer at a time, and the capacitor element and the external cathode terminal are directly conductively bonded through the opening of the insulating layer, thereby reducing the distance between the capacitor element and the external terminal. Shortening and self-inductance can be reduced. In addition, by forming a sealing layer in the part where the insulating layer on the external terminal side is exposed, moisture intrusion from the insulating layer part is suppressed without increasing the product thickness, and the moisture resistance reliability is excellent. It can be a structure.

1 is a cross-sectional view of a three-terminal solid electrolytic capacitor according to a first embodiment of the present invention. The figure which shows the capacitor | condenser element of the three terminal type solid electrolytic capacitor in the 1st Embodiment of this invention, Fig.2 (a) is a top view, FIG.2 (b) is the sectional view on the AA line in Fig.2 (a). Figure. Sectional drawing of the electrode substrate used for the three-terminal type solid electrolytic capacitor in the 1st Embodiment of this invention. Sectional drawing of the two-terminal type solid electrolytic capacitor in the 2nd Embodiment of this invention. The figure which shows the capacitor | condenser element of the two-terminal type solid electrolytic capacitor in the 2nd Embodiment of this invention, Fig.5 (a) is a top view, FIG.5 (b) is the sectional view on the AA line in Fig.5 (a). Figure. Sectional drawing of the electrode substrate used for the two-terminal type solid electrolytic capacitor in the 2nd Embodiment of this invention. Sectional drawing of a solid electrolytic capacitor.

  Hereinafter, embodiments of the solid electrolytic capacitor of the present invention will be described in detail with reference to the drawings.

  A method for producing a capacitor element used in the solid electrolytic capacitor of the present invention will be described with reference to FIG. First, a base material 1 made of an aluminum foil having both surfaces enlarged by an etching process and having a dielectric layer 2 made of an anodized oxide formed on the surface is cut into a target element size. Next, an insulating resin such as an epoxy resin is applied to a predetermined position on the dielectric layer 2 to form an insulating portion 3, and the base material 1 made of aluminum foil is divided into a plurality of regions. Thereafter, anodic oxidation is performed again, and a dielectric layer is re-formed at a portion where the aluminum core is exposed, such as a cut surface. Subsequently, a solid electrolyte layer 4 made of a conductive polymer, a graphite layer 5 and a metal electrode layer 6 made of a conductive paste or the like are formed in a region where the central cathode conductor portion of the plurality of regions is formed. The cathode conductor portion 9 is used. Next, of the plurality of regions, the aluminum base material 1 is exposed by excluding the dielectric layer 2 and the surface-enlarging layer in the end region other than the cathode conductor portion 9. Furthermore, Cu foil plated with Ni, Cu, Ag, or the like is connected as an anode lead 7 by ultrasonic welding or the like to form an anode portion 8.

  Next, the electrode substrate of the solid electrolytic capacitor of the present invention will be described with reference to FIG. Using a single-sided copper-clad plate with copper foil affixed to an insulating layer 10 such as polyimide resin, glass epoxy, or liquid crystal polymer, and etching the copper foil, external anode terminals 11 at both ends and external cathode terminals at the center 12 is formed. As the insulating layer 10, it is preferable to use a polyimide resin because it can be easily thinned and can be processed by chemical etching. On the other hand, the insulating layer 10 is provided with a plurality of openings, and the capacitor element 14 and the external terminal can be electrically connected by filling the openings with the conductive adhesive 16. Examples of the method of forming the opening include laser processing, drilling with a drill, etching, and the like. Among these, chemical etching is preferable in that only the insulating layer 10 can be processed over a wide range without affecting the external terminals. Further, a sealing layer 13 is formed in a portion where the insulating layer 10 is exposed on the external terminal side on the lower surface. The sealing layer 13 is made of an epoxy resin, an acrylic resin, a phenol resin, a polyamideimide resin, or the like, and may be mixed with a filler such as silica. In order to ensure mountability, the sealing layer 13 is made thinner than the external terminal, and care is taken so that the insulating layer 10 is not exposed and does not protrude to the external cathode terminal.

  Next, a method for producing a solid electrolytic capacitor of the present invention will be described with reference to FIG. The opening of the electrode substrate 15 is filled with a conductive adhesive 16 containing silver or the like, and the capacitor element 14 manufactured as described above is electrically connected to the external anode terminal 11 and the external cathode terminal 12 of the electrode substrate 15. After that, it is packaged with an exterior resin 17 such as an epoxy resin to obtain a solid electrolytic capacitor. Although a three-terminal solid electrolytic capacitor has been described here, a two-terminal solid electrolytic capacitor can be similarly manufactured as described in the following examples.

  A capacitor element used in the three-terminal solid electrolytic capacitor of the present invention will be specifically described with reference to FIG. First, an aluminum foil whose surfaces on both sides were enlarged was prepared and anodized to form the dielectric layer 2 on both sides. This aluminum foil is commercially available as an electrode for an aluminum electrolytic capacitor, and has a nominal formation voltage of 5 V and a thickness of 105 μm. This aluminum foil was cut into a rectangular shape having a width of 2.5 mm and a length of 6.0 mm to obtain a base material 1. Next, a total of four insulating portions 3 were formed on the front and back of the base material 1, leaving regions of 1.3 mm from the both end surfaces in the length direction of the base material 1 produced. The insulating part 3 is formed by applying an insulating resin mainly composed of an epoxy resin on both surfaces of the base material in a width direction in a linear shape having a thickness of 0.5 mm and a height of 100 μm, and impregnating and curing the base material 1. It is formed by.

  Here, the central part of the base material surrounded on both sides by the insulating part 3 is a cathode region, and the solid electrolyte layer 4 made of polypyrrole, which is a conductive polymer, is formed on both sides of this region. Next, the graphite layer 5 is applied by screen printing to a thickness of 15 μm and dried and solidified. Further, a conductive paste containing silver is applied to the graphite layer 5 to a thickness of 25 μm and dried and solidified to form a metal electrode. Layer 6 was formed as cathode conductor portion 9. The size of the cathode conductor is 2.5 mm in the width direction of the base material and 2.4 mm in the length direction.

  On the other hand, in the respective anode regions on both outer sides of the insulating portion 3, the dielectric layer is removed, and a Ni foil, a Cu foil having a width of 2.5 mm, a length of 1.0 mm, and a thickness of 80 μm is plated. As an anode lead 7, ultrasonic welding was performed on one surface of the anode region to form an anode portion 8. The three-terminal capacitor element 14 was manufactured by the above method.

  Next, the electrode substrate 15 used for the three-terminal solid electrolytic capacitor of the present invention will be described with reference to FIG. A resin plate made of polyimide resin having a thickness of 30 μm was prepared, and a single-sided copper-clad plate in which a copper foil having a thickness of 30 μm was bonded only to one side thereof. The copper foil portion of this single-sided copper-coated plate is chemically etched to form external terminals that are the external cathode terminal 12 and the external anode terminal 11, and the polyimide resin in each region where these external terminals are formed is removed by chemical etching. As a result, a total of three openings were formed in the respective regions corresponding to the cathode conductor portion 9 and the anode portion 8. The shape of this opening is 2.5 mm in width and 2.4 mm in length in the cathode region, and 2.5 mm in width and 1.3 mm in length in the two anode regions, respectively. Subsequently, an epoxy resin containing a filler was applied to a portion where the polyimide resin was exposed on the external terminal side, and the sealing layer 13 was formed by drying and solidifying. Here, the thickness is set to 25 μm so that the sealing layer 13 does not rise above the external terminals.

  Next, the opening was filled with a conductive adhesive 16 containing silver, and the capacitor element 14 was thermocompression bonded. At this time, the conductive adhesive 16 is filled so as to swell about several tens of μm from the edge of the opening of the polyimide resin, and the silver paste layer of the cathode conductor 9 of the main body and the copper foil of the anode 8 are The conductive adhesive 16 was securely bonded to make electrical connection.

  Then, the exterior was carried out by transfer molding using a mold resin containing epoxy resin as a main component, and the three-terminal solid electrolytic capacitor of the present embodiment was obtained. The external dimensions of the manufactured solid electrolytic capacitor are a chip shape having a width of 2.8 mm, a length of 6.3 mm, and a height of 0.46 mm.

  The two-terminal solid electrolytic capacitor of the present invention will be described with reference to FIGS. The material, dimensions, surface treatment method, dimensions of the copper foil, and the structures of the solid electrolyte layer 4, the graphite layer 5, and the metal electrode layer 6 formed are the same as in the case of Example 1. Since it is a two-terminal type solid electrolytic capacitor, there is only one anode portion 8 of the main body portion, and the insulating portion 3 is provided on both surfaces at a position of 1.3 mm from one end surface in the length direction of the base material. Only. The insulating part 3 is the same as the case of Example 1 in that the insulating resin is applied to the base material in a linear shape having a thickness of 0.5 mm and a height of 100 μm. Of the length of the base material of 6.0 mm, the length of the anode portion 8 is 1.3 mm, which is the same as in the first embodiment, but the length of the cathode conductor portion 9 is 4.2 mm. Also, the printed wiring board is a single-sided copper-clad board, the material of the resin, the point that the epoxy resin containing filler is applied to the exposed part of the polyimide resin on the external terminal side, and solidified, etc. The same as the case of 1. However, the opening is one each corresponding to the cathode conductor portion 9 and the anode portion 8 of the capacitor element 14, and the dimensions of the cathode conductor portion 9 are 2.5 mm in width, 4.2 mm in length, and the anode portion 8. Then, the width is 2.5 mm and the length is 1.3 mm. Next, the conductive adhesive 16 containing silver was filled in these openings and the capacitor element 14 was thermocompression bonded, and then a transfer mold was applied to obtain a two-terminal solid electrolytic capacitor. The outer dimensions of the manufactured solid electrolytic capacitor are the same as in the case of Example 1 in the form of a chip having a width of 2.8 mm, a length of 6.3 mm, and a height of 0.46 mm, but there are only two external terminals.

(Comparative Example 1)
For comparison with the three-terminal type solid electrolytic capacitor of Example 1 to which the present invention is applied, a sealing layer such as an epoxy resin containing a filler is not provided in a portion where the polyimide resin on the external terminal side is exposed. A solid electrolytic capacitor was produced using the electrode substrate 15 (see FIG. 7).

  The capacitor element 14 used in Comparative Example 1 is the same as that in Example 1 in terms of the dimensions and manufacturing method of each part. The adhesion of the electrode substrate 15 and the exterior by transfer molding were performed in the same manner as in Example 1 to obtain a three-terminal solid electrolytic capacitor of Comparative Example 1.

(Comparative Example 2)
For comparison with the two-terminal solid electrolytic capacitor of Example 2 to which the present invention is applied, a sealing layer such as an epoxy resin containing a filler is not provided on the portion where the polyimide resin on the external terminal side is exposed. A solid electrolytic capacitor was produced using the electrode substrate.

  The capacitor element 14 used in Comparative Example 2 is the same as that of Example 2 in all dimensions and manufacturing methods. The adhesion of the electrode substrate and the exterior by transfer molding were performed in the same manner as in Example 2 to obtain a two-terminal solid electrolytic capacitor of Comparative Example 2.

(Evaluation)
Prepare 10p each of the solid electrolytic capacitors of Examples 1 and 2 and Comparative Examples 1 and 2 prepared by the above method, put them in a constant temperature and humidity chamber of 65 ° C-95% RH, and conduct a standing test for 500 hours. The humidity resistance reliability was compared. The results are shown in Table 1. Here, the average value of the equivalent series resistance (ESR) at 100 kHz before the standing test is 1.00, and the ESR after 500 hours is expressed by relative evaluation. ESR was measured by a four-terminal method using an LCR meter (manufactured by Agilent Technologies).

  It can be seen that in the solid electrolytic capacitors of Examples 1 and 2 to which the present invention is applied, the ESR change before and after the standing test is small and the moisture resistance reliability is improved as compared with the solid electrolytic capacitors of Comparative Examples 1 and 2.

DESCRIPTION OF SYMBOLS 1 Base material 2 Dielectric layer 3 Insulating part 4 Solid electrolyte layer 5 Graphite layer 6 Metal electrode layer 7 Anode lead 8 Anode part 9 Cathode conductor part 10 Insulating layer 11 External anode terminal 12 External cathode terminal 13 Sealing layer 14 Capacitor element 15 Electrode substrate 16 Conductive adhesive 17 Exterior resin

Claims (4)

An anode body comprising a base material made of a plate-like or foil-like valve action metal having an enlarged surface, and a dielectric layer made of an oxide formed on the surface of the base material that has been enlarged, A cathode conductor portion is formed by connecting to the central portion of the anode body, and a capacitor element having anode leads connected to both ends of the anode body, and
An insulating layer having openings at the center and both ends, an external cathode terminal formed at the center of the lower surface of the insulating layer and covering a lower surface of the opening, and a lower surface of the insulating layer An electrode substrate having an external anode terminal formed of a metal layer that is formed on both ends and covers the lower surface of the opening,
Via the conductive adhesive formed in the opening, the cathode conductor portion and the external cathode terminal, and the anode lead and the external anode terminal are electrically connected, respectively, and the lower surface of the insulating layer is exposed. A solid electrolytic capacitor having a sealing layer in the part. An anode body comprising a base material made of a plate-like or foil-like valve action metal having an enlarged surface, and a dielectric layer made of an oxide formed on the surface of the base material that has been enlarged, A capacitor element in which a cathode conductor portion is formed connected to one end side of the anode body, and an anode lead is formed connected to the other end side of the anode body;
An insulating layer provided with an opening at one end and the other end; an external cathode terminal formed at one end of the lower surface of the insulating layer and covering the lower surface of the opening; and a lower surface of the insulating layer An electrode substrate having an external anode terminal formed of a metal layer that covers the lower surface of the opening,
Via the conductive adhesive formed in the opening, the cathode conductor portion and the external cathode terminal, and the anode lead and the external anode terminal are electrically connected, respectively, and the lower surface of the insulating layer is exposed. A solid electrolytic capacitor having a sealing layer in the part.   The solid electrolytic capacitor according to claim 1, wherein the insulating layer is made of a polyimide resin.   The solid electrolytic capacitor according to claim 1, wherein the opening is formed by chemical etching.

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