JP2010080560A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor of printed wiring board type, which maintains a conventional distance between external terminals, i.e., a positive electrode terminal and a negative electrode terminal and has excellent high-frequency characteristic while considering a short-circuit failure incidence rate at the time of mounting on a substrate. <P>SOLUTION: A printed wiring board type solid electrolytic capacitor is electrically connected to a substrate such as a printed wiring board, thereby using the electrolytic capacitor as an external terminal. The interval between a positive electrode conductor layer 41 and a negative electrode conductor layer 42 on an element mounting surface of a printed board is made narrower than the interval between a positive electrode terminal 43 and a negative electrode terminal 44 for external terminals. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor mainly used in a power circuit, and more particularly to a solid electrolytic capacitor in which a printed wiring board is electrically connected to a capacitor element and used as an external terminal.

  In recent years, signals in digital consumer devices have become faster, the power supply current of logic circuits tends to increase with the increase in operating frequency, and the drive voltage of LSIs has further decreased. For this reason, the margin for power supply noise is becoming smaller, and noise countermeasures are urgently needed. A capacitor is effective as a device for removing power supply noise and the like, and a capacitor having a low impedance in the high frequency region is also strongly demanded in the field of such a capacitor. A three-terminal capacitor type distributed constant noise filter has been proposed as one of the capacitors that can meet such requirements. Examples of the three-terminal capacitor include capacitors described in Patent Documents 1 and 2 and the like. FIG. 5 shows a cross-sectional view of a conventional three-terminal solid electrolytic capacitor. A base material made of a plate-like or foil-like valve action metal having an enlarged surface is used as the anode body 5, and the center of the dielectric layer made of an oxide of the valve action metal formed on the surface of the anode body 5 of the base material. A conductive polymer layer 6, a graphite layer 7, and a silver layer 8 are sequentially formed on the surface of the part to form a cathode part, and both end parts of the anode body 5 are used as anode parts. The anode leads 12 are connected to the anode portions at both ends, the cathode leads 13 are connected to the central silver layer 8, and the exterior is molded with the exterior resin 9. The anode lead 12 and the cathode lead 13 also function as external terminals as they are.

  Such a three-terminal type solid electrolytic capacitor is equivalent to a distributed constant type noise filter in the high frequency region in the capacitor element part and has a low impedance in a wide frequency band. However, when considering even external terminals, the self-inductance of the anode lead and cathode lead For this reason, there is a problem that the high frequency characteristics deteriorate. The self-inductance depends on the distance from the external terminal to the element, and increases as the length increases. Therefore, the longer the anode lead and the thicker the cathode lead, the worse the high frequency characteristics. The above-mentioned three-terminal solid electrolytic capacitor has a structure in which the anode lead is drawn from the side of the exterior and then bent to the bottom, so the anode lead becomes longer, and the independent cathode lead takes into consideration the handling characteristics during the manufacturing process. Then, since a thickness of 0.2 mm or more is required, it has been difficult to shorten between the external terminal and the element by shortening the anode lead length and reducing the thickness of the cathode lead.

  As a method for shortening the distance between the external terminal and the element, a capacitor using a printed wiring board described in Patent Document 3 has been proposed. The printed wiring board is composed of a double-sided copper-clad laminate, and an anode conductor layer (described as an anode conductor layer in Patent Document 3) and a cathode conductor layer (in Patent Document 3 as a cathode conductor layer) on one surface of the element mounting surface. Is provided on the external terminal surface that is the other component mounting surface, and both are electrically connected through through-holes (described as through-connection holes in Patent Document 3). By using a printed wiring board in this way, it is not necessary to pull out the anode part to the exterior side surface, and the anode terminal can be arranged directly below, and the external anode terminal and cathode terminal are integrated with an insulating resin substrate. Thinning is possible. Therefore, by applying the printed wiring board, the distance between the external terminal and the element is shortened, the self-inductance is reduced, and the high frequency characteristics are improved. Further, the printed wiring board type solid electrolytic capacitor has a current between the anode terminal and the cathode terminal reduced by shortening the distance between the anode conductor layer and the cathode conductor layer on the element mounting surface and the anode terminal and the cathode terminal serving as external terminals. The loop can be shortened, and further improvement in high frequency characteristics is expected.

JP 2002-164760 A JP 2007-42932 A JP 2002-134359 A

  However, when applied to a printed wiring board type solid electrolytic capacitor with a shortened current loop as described above, when the solid electrolytic capacitor is solder-mounted, the positive / cathode mounting land on the board (motherboard etc.) side and the distance between the solder are also Shorter. Therefore, if the distance between the positive and negative electrodes is shortened, the frequency of occurrence of short-circuit defects increases when the solid electrolytic capacitor is mounted on a substrate (such as a mother board), and there is a limit to shortening the distance between the anode terminal and the cathode terminal.

  The present invention provides a printed circuit board type solid electrolytic capacitor having excellent high-frequency characteristics while keeping the distance between the external terminal, that is, the anode terminal and the cathode terminal at a conventional distance in consideration of the occurrence rate of short-circuit defects during board mounting. The purpose is to do.

  The solid electrolytic capacitor of the present invention has one or a plurality of anode bodies each including a dielectric made of a valve metal oxide formed on the surface of a plate-like or foil-like valve metal having an enlarged surface. A capacitor element in which an anode metal layer is connected to an area of one anode part separated by an insulating part and a cathode conductor layer is formed in the area of the other cathode part, an anode conductor layer for mounting the capacitor element on the surface of the insulating resin, and A solid electrolytic capacitor connected to a printed wiring board on which a cathode conductor layer is formed and an anode terminal and a cathode terminal for external terminals electrically connected to the anode conductor layer and the cathode conductor layer on the back surface, respectively, The distance between the anode conductor layer for mounting an element and the cathode conductor layer is narrower than the distance between the anode terminal and the cathode terminal. The distance between the element mounting anode conductor layer and cathode conductor layer of the printed wiring board is the minimum creepage distance of the printed wiring board, and is preferably 0.3 mm or less (excluding 0). Moreover, you may provide an insulating layer between the anode conductor layer for element mounting of the said printed wiring board, and a cathode conductor layer, and a part on the said anode conductor layer and a cathode conductor layer. Moreover, it is preferable to increase the capacitance between the lands by making the shape of the opposing sides of the anode conductor layer and the cathode conductor layer for mounting elements on the printed wiring board into wavy curves. The anode conductor layer and the cathode conductor layer for mounting elements on the printed wiring board may be thicker than the anode terminal and cathode terminal for the external terminal.

  The solid electrolytic capacitor of the present invention has only the interval between the anode conductor layer and the cathode conductor layer on the element mounting surface side without changing the distance between the external terminal of the printed wiring board on which the capacitor element is mounted, that is, the anode terminal and the cathode terminal. Therefore, the distance between the anode conductor layer and the cathode conductor layer on the element mounting surface can be shortened to the minimum creepage distance. Therefore, the capacitance generated between the anode conductor layer and the cathode conductor layer on the element mounting surface is larger than that of the conventional one, and the capacitance has a function as a filter. As a result, high frequency characteristics can be improved by applying the present invention. Further, when the shape of the opposing sides of the anode conductor layer and the cathode conductor layer forming the wiring layer on the element mounting surface is a wavy curved shape, the capacity is further increased and the high frequency characteristics can be improved.

  A solid electrolytic capacitor according to an embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present invention. Solid electrolytic capacitors are roughly classified into a capacitor element portion and a printed wiring board.

  First, the capacitor element portion will be described. The anode body 5 is cut into a target element shape, for example, a flat plate shape. The anode body 5 is made of aluminum, niobium, tantalum, or an alloy thereof, and both surfaces thereof are enlarged by etching, and an anodic oxide film is formed on the surface by anodic oxidation. Next, the insulating body 1 is formed by using an epoxy resin or the like at predetermined positions of the anode body 5, for example, at a certain distance from the end face, and the anode body 5 is divided into three regions. , Second and third regions. The anode metal layer 2 having a predetermined thickness is welded to the first and third regions by ultrasonic welding or the like to form the anode portion of the capacitor element. The anode metal layer 2 is made of a metal foil such as copper, aluminum, or nickel. Next, a conductive polymer layer 6, a graphite layer 7, and a silver layer 8 are sequentially laminated on the second region in the center to form a cathode layer of the capacitor element.

  Next, the printed wiring board will be described. The printed wiring board is composed of a double-sided copper-clad laminate in which a copper plate is stretched on an insulating resin layer 3 such as glass epoxy or polyimide, and has an anode conductor layer 41 and a cathode conductor layer 42 for mounting a capacitor element on the front surface and an external terminal on the back surface. A printed wiring board having external terminals in which the anode terminal 43 and the cathode terminal 44 are formed by wiring etching, and then the respective anode conductor layers, anode terminals, and cathode conductor layers and cathode terminals are electrically connected through through holes 45. . In the printed wiring board used in the present invention, the creepage distance between the anode conductor layer 41 and the cathode conductor layer 42 on the capacitor element mounting side is preferably as short as possible.

  In the solid electrolytic capacitor according to the embodiment of the present invention, the conductive adhesive 11 such as silver paste is printed on the anode conductor layer 41 and the cathode conductor layer 42 for mounting the element on the printed wiring board, and the capacitor element portion is electrically connected. Printed circuit board type solid electrolytic capacitor in contact with

  The printed wiring board type solid electrolytic capacitor of the present invention will be described below with reference to some three-terminal examples, but the same effect can be obtained with respect to the two-terminal type printed wiring board type solid electrolytic capacitor. It is done.

Example 1
A method for producing a capacitor element portion used in a printed wiring board type solid electrolytic capacitor according to Example 1 will be described with reference to FIG. 1 used in the description of the embodiment of the present invention. First, an aluminum foil having a surface-enlarging layer as the anode body 5 and having an anodized surface was used. The aluminum foil is commercially available for aluminum electrolytic capacitors, and a foil with a nominal formation voltage of 5 V and a thickness of 105 μm was used. This foil was cut into a rectangular shape having a width of 2.5 mm and a length of 5.0 mm, which is the size of the element portion. Next, the insulating part 1 is formed by applying and curing an insulating resin mainly composed of epoxy at a thickness of 0.5 mm on both sides of the cut end face of the aluminum foil from 0.8 to 1.3 mm. Formed. At this time, the region surrounded by the insulating portion 1 is used as the region of the cathode portion of the capacitor element, and the conductive polymer layer 6 made of polypyrrole, which is a conductive polymer, is further provided thereon with the graphite 7 and the silver layer 8. The formed cathode conductor layer was 2.5 mm wide and 2.4 mm long. On the other hand, a copper foil having a width of 2.5 mm, a length of 1.3 mm, and a thickness of 0.05 mm is ultrasonically welded to a region of the anode portion of the capacitor element outside the insulating portion 1 to form an anode metal layer 2 and anodes at both ends of the cathode portion. A capacitor element part for a three-terminal solid electrolytic capacitor having a part was obtained.

  Next, the printed wiring board will be described. The printed wiring board uses a double-sided copper-clad laminate in which a 18 μm-thick copper plate is pasted on a 60 μm-thick polyimide resin layer. In addition, an anode terminal 43 and a cathode terminal 44 for external terminals were obtained. At this time, the dimensions of the cathode terminal 44 on the external terminal side are 2.5 mm in width and 1.8 mm in length, and the dimensions of the anode terminal 43 on both sides thereof are 2.5 mm in width and 0.8 mm in length, the anode terminal 43 and the cathode terminal. The distance between 44 was 0.6 mm. On the other hand, on the capacitor element mounting side, the cathode conductor layer 42 has a width of 2.5 mm and a length of 2.8 mm, and the anode conductor layer 41 on both sides thereof has a width of 2.5 mm and a length of 0.8 mm. The creepage distance between 41 and the cathode conductor layer 42 was 0.1 mm. Further, the anode conductor layer 41 and the cathode conductor layer 42 on the element mounting surface are electrically connected to the anode terminal 43 and the cathode terminal 44 for external terminals, which are the mounting surfaces, respectively, through through holes 45 having a diameter of 0.1 mm, and external terminals are provided. A printed wiring board was obtained. The plating thickness was 30 μm. Subsequently, a conductive adhesive 11 made of silver paste is screen-printed on the element mounting surface of the printed wiring board to the anode conductor layer and the cathode conductor layer, respectively, with a width of 2.3 mm, a length of 0.6 mm, and a width of 2.3 mm. After the pattern printing with a length of 1.8 mm, the capacitor element part is adhered, and further, the exterior is molded with an exterior resin 9 so as to cover the capacitor element part, and the width is 2.8 mm, the length is 5.3 mm, and the height is 0. A .46 mm three-terminal printed wiring board type solid electrolytic capacitor was obtained. The insertion loss of Example 1 is described in the item of Example 1 in Table 1.

(Example 2)
FIG. 2 is a schematic cross-sectional view of a solid electrolytic capacitor according to Example 2 of the present invention. Example 2 is the same as Example 1 except that the solder resist layer 10 made of an epoxy resin is formed between the anode conductor layer 41 and the cathode conductor layer 42 in the wiring layer formed on the element mounting surface of the printed wiring board of Example 1. A three-terminal printed wiring board type solid electrolytic capacitor was obtained by the same manufacturing method. However, on the element mounting side, the dimensions of the cathode conductor layer 42 are 2.5 mm in width and 2.9 mm in length, and the dimensions of the anode land on both sides are 2.5 mm in width and 0.8 mm in length, the anode conductor layer 41 and the cathode The creepage distance between the conductor layers 42 was 0.05 mm. Further, the printed pattern of the conductive adhesive 11 made of silver paste on the element mounting surface is 2.3 mm wide and 0.6 mm long on the anode conductor layer, 2.3 mm wide and 2.7 mm long on the cathode conductor layer. It was. The insertion loss of this example is described in the item of Example 2 in Table 1.

(Example 3)
FIG. 3 is a plan view showing a capacitor element mounting surface of a printed wiring board used for a solid electrolytic capacitor according to Example 3 of the present invention. In the third embodiment, in the wiring layer formed on the element mounting surface of the printed wiring board of the first embodiment, the center of the side where the anode conductor layer 41 and the cathode conductor layer face each other is a square wave having a wavelength of 0.4 mm and an amplitude of 0.4 mm. A three-terminal printed wiring board type solid electrolytic capacitor was obtained by the same manufacturing method as in Example 1 except that the capacity due to the gap between the lands was increased. However, the creepage distance between the anode conductor layer 41 and the cathode conductor layer 42 was 0.1 mm. The insertion loss of this example is described in the item of Example 3 in Table 1. In addition to the square wave, a sine wave, a triangular wave, or the like can be used as the wave shape.

Example 4
In this Example 4, a three-terminal manufacturing method is used in the same manner as in Example 1 except that the wiring thickness of the anode conductor layer and the cathode conductor layer is 30 μm in the wiring layer formed on the element mounting surface of the printed wiring board of Example 3. A printed wiring board type solid electrolytic capacitor was obtained. The insertion loss of this example is described in the item of Example 4 in Table 1.

(Comparative Example 1)
FIG. 4 is a cross-sectional view of a solid electrolytic capacitor according to a conventional comparative example 1. The capacitor element part was produced by the same method as in Example 1. In Comparative Example 1, the dimensions of the cathode conductor layer 42 on the element mounting side of the printed wiring board are 2.5 mm in width and 1.8 mm in length, and the dimensions of the anode conductor layer 41 on both sides thereof are 2.5 mm in width and 0. A three-terminal printed wiring board type solid electrolytic capacitor was obtained by the same production method as in Example 1 except that the creepage distance between the anode conductor layer 41 and the cathode conductor layer was 8 mm and 0.6 mm. The insertion loss of Comparative Example 1 is listed in the item of Comparative Example 1 in Table 1.

(Comparative Example 2)
The capacitor element portion of Comparative Example 2 was produced by the same method as in Example 1. In Comparative Example 2, the dimension of the cathode conductor layer on the element mounting side of the printed wiring board is 2.5 mm in width and 2.3 mm in length, and the dimensions of the anode conductor layer on both sides thereof are 2.5 mm in width and 0.8 mm in length. The creepage distance between the anode conductor layer and the cathode conductor layer is 0.35 mm, the dimensions of the cathode terminal on the external terminal side on the mounting side are 2.5 mm in width and 2.3 mm in length, and the dimensions of the anode terminals on both sides are width 2 A three-terminal printed wiring board type solid electrolytic capacitor was obtained in the same manner as in Example 1 except that the thickness was 0.5 mm, the length was 0.8 mm, and the distance between the anode terminal and the cathode terminal was 0.35 mm. The insertion loss of Comparative Example 2 is shown in the item of Comparative Example 2 in Table 1.

  Table 1 shows the insertion loss of 1 GHz of the printed wiring board type solid electrolyte capacitor thus obtained. The insertion loss was measured using a high-frequency probe (Cascade Microtech) and a network analyzer (Agilent).

  From the above results, it can be seen that high frequency characteristics can be improved by using the printed wiring board type solid electrolytic capacitor of the present invention. In addition, since the distance between the anode conductor layer and the cathode conductor layer of the external terminal lands in Examples 1, 2, and 3 is the same as that in Comparative Example 1, the frequency of occurrence of short-circuit defects during substrate mounting is the same.

  The solid electrolytic capacitor according to the present invention can be applied to a printed wiring board type solid electrolytic capacitor as an external terminal by being electrically connected to a substrate such as a printed wiring board, and has better frequency characteristics than the conventional one. A solid electrolytic capacitor having the following can be obtained.

The schematic cross section of the solid electrolytic capacitor of embodiment of this invention. The schematic cross section of the solid electrolytic capacitor which concerns on Example 2 of this invention. The top view which shows the capacitor | condenser element mounting surface of the printed wiring board used for the solid electrolytic capacitor which concerns on Example 3 of this invention. Sectional drawing of the solid electrolytic capacitor which concerns on the conventional comparative example 1. FIG. Sectional drawing of the conventional three terminal type solid electrolytic capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation part 2 Anode metal layer 3 Insulation resin layer 41 Anode conductor layer 42 Cathode conductor layer 43 Anode terminal 44 Cathode terminal 45 Through hole 5 Anode body 6 Conductive polymer layer 7 Graphite layer 8 Silver layer 9 Exterior resin 10 Solder resist layer 11 Conductive adhesive 12 Anode lead 13 Cathode lead

Claims (5)

  An anode body having a dielectric made of an oxide of a valve metal formed on the surface of a plate-like or foil-like valve metal having an enlarged surface and separated by one or a plurality of insulating portions A capacitor element in which the anode metal layer is connected to the area of the part, the cathode layer is formed in the area of the other cathode part, and the anode conductor layer and the cathode conductor layer for mounting the capacitor element are formed on the surface of the insulating resin layer. A solid electrolytic capacitor connected to a printed wiring board on which an anode terminal and a cathode terminal for an external terminal electrically connected to the anode conductor layer and the cathode conductor layer, respectively, and the anode conductor layer for mounting the element And the cathode conductor layer is narrower than the gap between the anode terminal for the external terminal and the cathode terminal.   The distance between the anode conductor layer and the cathode conductor layer for mounting elements on the printed wiring board is the minimum creepage distance of the printed wiring board, and is 0.3 mm or less (excluding 0). Item 10. A solid electrolytic capacitor according to Item 1.   3. An insulating layer is provided between the anode conductor layer and the cathode conductor layer for mounting elements on the printed wiring board and partly on the anode conductor layer and the cathode conductor layer. Solid electrolytic capacitor.   4. The solid electrolytic capacitor according to claim 1, wherein the shape of the opposing sides of the element mounting anode conductor layer and the cathode conductor layer of the printed wiring board is wavy. 5.   5. The thickness of the anode conductor layer and the cathode conductor layer for mounting elements on the printed wiring board is greater than the thickness of the anode terminal and the cathode terminal for the external terminal, respectively. The solid electrolytic capacitor as described.

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