JP2010213017A - Low-pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance low-pass filter which is made simple in processes and also wide in pass band, and large in an attenuation gradient. <P>SOLUTION: A low-pass filter is constituted by using an anode body 1 constituted of a valve operating metal in which enlargement processing is not applied to a surface to connect in parallel a plurality of double-terminal type solid-state electrolytic capacitors 30a, 30b having different electric lengths calculated from a cutoff frequency and molding them with an exterior resin. Lengths La, Lb of cathodes 7 of the double-terminal type solid-state electrolytic capacitors 30a, 30b are set to 1/4 of electric lengths. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a capacitor-type low-pass filter that suppresses noise propagating on a conducting wire such as a power supply line and a signal line.

  In recent years, with the development of microcomputers, microcomputers are mounted in all fields such as industrial equipment, consumer equipment, and communication equipment. However, in recent digital devices, high-frequency noise has increased due to the development of communication networks between devices and the improvement of the operating frequency of switching power supplies. On the other hand, there is an allowable operating margin for noise due to faster digital processing and lower operating voltages. Since it is becoming smaller, so-called low-pass filters that remove high-frequency noise are becoming more important.

  Since noise that enters a microcomputer often propagates mainly from a power supply line and a signal line, a noise filter is widely used in such a part. Conventionally used noise filters include those using a two-terminal capacitor, those using a three-terminal capacitor, those using an inductor, and a low-pass filter that combines a capacitor and an inductor.

  FIG. 5 is a conceptual diagram for explaining the characteristics of a general low-pass filter, and shows the difference between an ideal filter and an actual filter and characteristic terms. As shown in FIG. 5, as the required characteristics of the low-pass filter, the insertion loss is small in the low frequency band pass band, the attenuation band of the insertion loss is narrow, the attenuation slope of the insertion loss is large, and the stop band is wide in the high frequency band. Can be mentioned.

  In general, with a two-terminal capacitor, the attenuation slope of the insertion loss is small, so it has become difficult to maintain sufficient signal quality.On the other hand, although the attenuation slope of the insertion loss is large, the response to high-speed signals is poor. Since signal quality cannot be ensured sufficiently, current ones using three-terminal capacitors or low-pass filters combining capacitors and inductors have become mainstream.

  FIG. 4 is a schematic cross-sectional view of a conventional three-terminal solid electrolytic capacitor. The three-terminal solid electrolytic capacitor 102 is formed by forming a dielectric film 2 made of a metal oxide on the surface of an anode body 1 made of a plate-like or foil-like valve action metal whose surface has been enlarged, and its center. A solid electrolyte layer 4 made of a conductive polymer, a graphite layer 5 and a conductive paste layer 6 are sequentially laminated on the surface of the part to form a cathode part 7. Insulator layers 3 are formed on both sides of the cathode portion 7, and the anode body 1 region further outside the insulator layer 3 is used as the anode portion 8. A lead frame 9 made of copper foil or the like is connected to these anode portions 8 by ultrasonic welding or the like. Thereafter, the lead frame 9 and the cathode portion 7 are bonded to the element-side anode terminal 11a and the element-side cathode terminal 11b formed on the upper surface of the substrate 12 through the conductive adhesive 10, respectively, and then molded with an exterior resin. Mold. An external anode terminal 13a and an external cathode terminal 13b are formed on the lower surface of the substrate 12. Such a three-terminal solid electrolytic capacitor is disclosed in Patent Document 1.

JP 2008-294012 A

  However, when the conventional three-terminal type solid electrolytic capacitor as shown in FIG. 4 is used as a noise filter, the length of the anode body penetrating the cathode portion is increased, so that the inductance component increases, and the valve action metal Since the surface of the anode body is made to be enlarged by etching or the like, the capacitance is increased, so that the high frequency band stop band is widened, but the low frequency band pass band is narrowed, and the signal quality is reduced. There was a drawback of deteriorating.

  In order to solve the above-described problems, an object of the present invention is to provide a high-performance low-pass filter that simplifies the process, widens the pass band, and has a large attenuation gradient.

  In order to solve the above problems, the present invention uses an anode body made of a valve metal that does not enlarge the surface, has different electrical lengths calculated from the cut-off frequency, and the length of each cathode part. This is a low-pass filter configured by connecting a plurality of two-terminal solid electrolytic capacitors having a length equal to ¼ of each electric length in parallel.

  Moreover, since the two-terminal solid electrolytic capacitor has the same configuration as the conventional solid electrolytic capacitor except for the non-enlarging process on the valve action metal surface, the manufacturing man-hour is not complicated. The length L of the cathode portion is set so as to satisfy the relational expression 1 so that it becomes 1/4 of the electrical length.

ここでｆはローパスフィルタでのカットしたい減衰域の周波数、ｃは光速、ｅ_ffは母材となる弁作用金属の酸化物からなる誘電体皮膜の実効誘電率である。また、複数の二端子型固体電解コンデンサは、それぞれ陰極部の長さＬが異なり、陰極部の長さが長い方のコンデンサの陽極部の幅を、陰極部の長さが短い方のコンデンサの陽極部の幅より狭くし、各々の固体電解コンデンサの陽極部同士、陰極部同士をそれぞれ電気的に並列接続している。

Here, f is the frequency of the attenuation region to be cut by the low-pass filter, c is the speed of light, and _eff is the effective dielectric constant of the dielectric film made of the oxide of the valve metal that is the base material. The plurality of two-terminal solid electrolytic capacitors have different cathode portion lengths L, the width of the anode portion of the capacitor having the longer cathode portion, and the length of the capacitor having the shorter cathode portion. It is narrower than the width of the anode part, and the anode parts and cathode parts of each solid electrolytic capacitor are electrically connected in parallel.

  According to the present invention, a dielectric film made of an oxide of a valve action metal is formed on the surface of an anode body made of a linear, plate-like or foil-like valve action metal, and is formed on a part of the dielectric film. Forming a cathode part in which a cathode conductor layer including a solid electrolyte layer is laminated, forming an insulator layer next to the cathode part, and forming the anode part separated from the cathode part through the insulator layer as the anode part A plurality of two-terminal solid electrolytic capacitors having a structure in which a plurality of two-terminal solid electrolytic capacitors are connected in parallel. The length of each cathode portion of the solid electrolytic capacitor is 1/4 of the electrical length, and the surface of each anode body of the plurality of two-terminal solid electrolytic capacitors is not subjected to the surface expansion treatment. A low pass filter is obtained.

  According to the present invention, a low-pass filter made of a different valve metal can be obtained for each anode body of a plurality of two-terminal solid electrolytic capacitors.

  In the two-terminal solid electrolytic capacitor used in the low-pass filter of the present invention, the surface of the anode body made of a valve metal is not subjected to the surface enlargement process, so that the increase in the capacity is suppressed, the pass band of the low-pass filter is expanded, and It is possible to suppress the insertion loss and improve the signal quality.

  In addition, when one end of the cathode part is insulated and the length of the cathode part is ¼ of the electrical length, a standing wave is generated at a desired frequency, and the two-terminal solid electrolytic capacitor is Open stub. In general, the characteristics of an open stub depend on the shape of the anode body that forms the stub. That is, when the anode body is thin, the inhibition range is narrowed due to an increase in the inductance component, but the attenuation gradient is increased. On the other hand, when the anode body is wide, the attenuation gradient is decreased due to the increase in the capacitance component. However, the zone of inhibition becomes wider. Utilizing these characteristics, a low-pass filter having a large attenuation gradient and a wide blocking band can be obtained by combining the anode body with a long and short shape and connecting them in parallel.

  In addition, by electrically connecting the anode parts, the anode part is apparently extended, so that the inductance component is increased and the attenuation gradient can be further improved.

  Furthermore, since the two-terminal solid electrolytic capacitor used in the low-pass filter of the present invention has the same configuration as the conventional one except for the non-enlarging process of the anode body made of a valve metal, the process can be simplified and easily manufactured. It becomes possible.

FIG. 1A is a cross-sectional view of a two-terminal solid electrolytic capacitor, and FIG. 1B is a perspective view of a low-pass filter. FIG. 2A is a sectional view of a two-terminal solid electrolytic capacitor, and FIG. 2B is a perspective view of the low-pass filter. Comparison result of insertion loss of low-pass filter. The cross-sectional schematic diagram of the conventional three terminal type solid electrolytic capacitor. The conceptual diagram explaining the characteristic of a low-pass filter.

  A mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining a low-pass filter of the present invention using a two-terminal solid electrolytic capacitor. FIG. 1 (a) is a cross-sectional view of the two-terminal solid electrolytic capacitor, and FIG. 1 (b) is a perspective view of the low-pass filter. Each figure is shown.

  As a first embodiment, a low-pass filter in which two two-terminal solid electrolytic capacitors using the same valve metal are connected in parallel will be described. As shown in FIG. 1 (a), a two-terminal solid electrolytic capacitor uses an anode body 1 made of an aluminum foil valve metal, cut into a desired shape and size, and anodized on the surface including the cut surface. The body film 2 is formed.

  Next, an insulator layer 3 is formed at a predetermined position on the dielectric film 2 with an epoxy resin or the like, and an anode body 1 having two regions separated by the insulator layer 3 is obtained. This state is called an anode body with an insulator layer 3. A metal layer made of a solid electrolyte layer 4 made of a conductive polymer, a graphite layer 5, a conductive paste layer 6, etc. is sequentially laminated on one of the two regions so as to cover the anode body 1. Part 7 is configured.

  Here, the length of this region, that is, the length L of the cathode portion 7 is set so as to satisfy the relational expression 1 so that it becomes 1/4 of the electrical length.

ここでｆはローパスフィルタでのカットオフ周波数、ｃは光速、ｅ_ffは母材となる弁作用金属の酸化物からなる誘電体の実効誘電率である。

Here, f is a cutoff frequency in the low-pass filter, c is the speed of light, and _eff is an effective dielectric constant of a dielectric made of an oxide of a valve metal that serves as a base material.

  Subsequently, the dielectric film 2 on the surface is completely peeled off with a laser or the like to expose the anode body 1 with respect to the area that is not the cathode area of the two areas divided by the insulator layer, and the anode section is exposed. 8 is formed.

  As shown in FIG. 1B, two types of the above-described two-terminal solid electrolytic capacitors are produced, in which the widths Wa and Wb of the anode body 1 and the lengths La and Lb of the cathode portion 7 are different from each other. One is a so-called elongate two-terminal solid electrolytic capacitor 30a in which the width Wa of the anode body 1 is small and the length La of the cathode portion 7 is long, and the other is the width Wb of the anode body 1 being large. A so-called thick and short two-terminal solid electrolytic capacitor 30b having a short cathode portion length Lb was obtained. The width Wb of the anode body 1 of the two-terminal solid electrolytic capacitor 30b and the length Lb of the cathode portion 7 are the width Wa of the anode body 1 of the two-terminal solid electrolytic capacitor 30a and the length La of the cathode portion 7. In contrast, Wb> Wa and La> Lb are set.

  Subsequently, as shown in FIG. 1B, the two-terminal solid electrolytic capacitor 30a having the width Wa of the anode body 1 and the length La of the cathode portion 7, the width Wb of the anode body 1, and The anode portions 8 of the two-terminal solid electrolytic capacitor 30b having the length Lb of the cathode portion 7 are placed side by side on a lead frame 9 made of copper foil or the like and electrically connected by ultrasonic welding.

  Thereafter, the element-side anode terminal 11a, the element-side cathode terminal 11b, the external anode terminal 13a, and the external cathode terminal 13b are electrically conductive on the element-side anode terminal 11a and the element-side cathode terminal 11b of the substrate 12 formed on the upper and lower surfaces, respectively. The lead frame 9 and the two cathode portions 7 connecting the anode portions 8 of the two types of two-terminal type solid electrolytic capacitors 30a and 30b are placed and heat-cured through the adhesive 10 The low pass filter 100 is configured by molding with an exterior resin (not shown).

  2A and 2B are diagrams illustrating a low-pass filter of the present invention using a two-terminal solid electrolytic capacitor. FIG. 2A is a cross-sectional view of the two-terminal solid electrolytic capacitor, and FIG. 2B is a perspective view of the low-pass filter. Each figure is shown.

  As a second embodiment, a low-pass filter in which two two-terminal solid electrolytic capacitors using different types of valve metal are connected in parallel will be described. FIG. 2A is a cross-sectional view of a solid electrolytic capacitor having the same configuration as FIG. Two types of two-terminal solid electrolytic capacitors here use an anode body 1 made of a valve metal of a tantalum wire, the anode body 1 has a small width Wc, and a cathode portion length Lc is long. A so-called elongated two-terminal solid electrolytic capacitor 30c, and the other is a so-called thick and short shape in which the width Wb of the anode body 1 shown in FIG. 1B is large and the length Lb of the cathode portion is short. The same as the two-terminal solid electrolytic capacitor 30b. The width Wc of the anode body 1 of the elongated two-terminal solid electrolytic capacitor 30c and the length Lc of the cathode portion 7 are the anode of the elongated two-terminal solid electrolytic capacitor 30a shown in FIG. The width Wa of the body 1 and the length La of the cathode portion 7 are set such that Wa> Wc and Lc> La, respectively.

  As shown in FIG. 2B, the two-terminal solid electrolytic capacitor 30c having the width Wc of the anode body 1 and the length Lc of the cathode part 7, the width Wb of the anode body 1, and the cathode part 7 The anode portions 8 of the two-terminal solid electrolytic capacitor 30b having the length Lb are placed side by side on a lead frame 9 made of copper foil or the like, and are electrically connected by ultrasonic welding.

  Thereafter, the element-side anode terminal 11a, the element-side cathode terminal 11b, the external anode terminal 13a, and the external cathode terminal 13b are electrically conductive on the element-side anode terminal 11a and the element-side cathode terminal 11b of the substrate 12 formed on the upper and lower surfaces, respectively. The lead frame 9 and the two cathode portions 7 that connect the anode portions 8 of the two types of two-terminal solid electrolytic capacitors 30b and 30c are placed through the adhesive 10 and electrically cured by heating and curing. The low pass filter 101 is configured by connecting and molding with exterior resin (not shown).

  The anode body 1 may be made of a valve metal such as aluminum, tantalum, niobium, titanium, etc. The shape may be any of linear, plate or foil, but the characteristics and workability of the selected valve metal are also considered. It is preferable to select appropriately.

  The dielectric film 2 acts as a dielectric, and is formed on the metal surface by immersing the valve action metal in the electrolytic solution and flowing an electric current in the same manner as a normal solid electrolytic capacitor. It is preferable to form a film by appropriately adjusting the type and current of the electrolyte.

  As long as the material has high heat resistance, the insulator layer 3 may be an epoxy-based or silicone-based thermosetting resin, a polyimide-based thermoplastic resin, or a paste or a liquid material is used. In view of film forming processability, a silicone-based thermosetting resin is more preferable. A general method such as dipping, spraying, coating, or printing may be used as the forming method, and the thickness is preferably 10 to 30 μm, which is sufficient to ensure an insulating function. The insulator layer 3 is provided on both sides of the cathode portion 7. Since the insulator layer 3 is a treatment for insulation between the anode portion and the cathode portion, the anode body on the side opposite to the anode portion 8 is provided. When the dielectric film 2 is formed at the end of the first electrode, it may be provided only on one side of the cathode portion 7, that is, on the anode portion 8 side, without being provided on the end portion of the anode body.

  As the solid electrolyte layer 4, it is preferable to use a conductive polymer such as polythiophene or polypyrrole, as in a normal solid electrolytic capacitor.

  The graphite layer 5 is for enhancing the bonding between the silver 7 laminated on the upper layer and the solid electrolyte layer 4 formed on the lower layer, as in a normal solid electrolytic capacitor.

  The conductive paste layer 6 is preferably formed by applying a silver paste, which is generally used as a cathode electrode material, with a dispenser or the like, followed by drying and curing.

  The lead frame 9 is preferably made of a conductive material made of metal such as copper, aluminum, stainless steel, or an alloy thereof, and further having its surface plated with gold, silver, tin, nickel or the like.

  The conductive adhesive 10 is preferably applied by using a dispenser with a paste-like resin such as an epoxy resin containing metal powder such as gold, silver and copper.

  The element-side anode terminal 11a and the element-side cathode terminal 11b are formed by attaching a conductive foil body made of metal such as copper or aluminum to the upper surface of the substrate 12, and then printing such as gravure printing or screen printing. It can be formed by etching by applying a resist printing method. Not only the above method but also a conductive paste may be printed.

  The substrate 12 is preferably made of a highly heat-resistant insulating material, and any of a resin system such as a glass epoxy material, a BT resin, a polyimide, a liquid crystal polymer, or a ceramic system such as alumina may be used. It is more preferable to use a general-purpose glass epoxy material that is effective in terms of flexibility and cost.

  The external anode terminal 13a and the external cathode terminal 13b are formed by a general printing method such as gravure printing or screen printing after a conductive foil body made of metal such as copper or aluminum is bonded and attached to the lower surface of the substrate 12. It can be formed by performing resist printing and etching. Not only the above method but also a conductive paste may be printed.

  The widths Wa, Wb, and Wc of the anode body 1 can be appropriately adjusted according to the external shape of the low-pass filter, and are preferably large for a low profile and small for a small floor area.

The lengths La, Lb, and Lc of the cathode part 7 are lengths L that satisfy the above-mentioned formula 1, and the electrical length calculated by the frequency of the signal to be cut, that is, the cut-off frequency f and the effective dielectric constant _eff It is desirable that the frequency is adjusted to ¼ so that each of the two-terminal solid electrolytic capacitors 30a, 30b, and 30c has a specific resonance frequency in a frequency band higher than the cutoff frequency f.

  The exterior resin (not shown) is a general-purpose sealing resin and can be any resin that can withstand the usage environment, such as epoxy-based, phenol-based thermosetting resins, polypropylene (PP), polystyrene (PS), etc. Any of these thermoplastic resins may be used, but it is preferable to select them appropriately in consideration of heat resistance and workability. In consideration of solder reflow mounting property on the power supply board, an epoxy-based thermosetting resin is more preferable. The sealing method may be any method such as an injection method or a transfer method.

  Hereinafter, the low-pass filter of the present invention will be described in detail with reference to examples.

Example 1
First, as the anode body 1, the following two types of two-terminal solid electrolytic capacitors 30 a and 30 b were produced using an aluminum foil having a nominal chemical formation voltage of 20 V and a thickness of 100 μm that does not have a surface-enlarging treatment.

  An elongated two-terminal solid electrolytic capacitor 30a is cut into a rectangular shape having a width Wa of 1.0 mm and a length of 8.0 mm, and immersed in a 10% diammonium adipate aqueous solution, and a voltage of 25V is obtained. Was applied to form a dielectric film 2 on the entire surface including the cut surface by anodic oxidation. Thereafter, an insulating layer 3 is formed by applying and curing an epoxy resin with a width of 0.5 mm at a position 1.0 mm inside from one end in the length direction of the aluminum foil. A 1.0 mm region was defined as an anode region. Also, in the other region through the insulator layer 3, an epoxy resin is similarly applied at a position of 6.0 mm from the insulator layer 3 with a width of 0.5 mm and a thickness of 50 μm and cured to form the insulator layer 3 A 6.0 mm region sandwiched between these two insulator layers 3 was defined as a cathode region. This state is called an anode body with an insulator layer 3.

Subsequently, 3,4-ethylenedioxythiophene as a monomer, ammonium peroxodisulfate as an oxidizing agent, and paratoluenesulfonic acid as a dopant on the surface of the dielectric film 2 with respect to the cathode region of the anode body with the insulator layer 3, respectively. A solid electrolyte layer 4 made of a conductive polymer was formed by reaction at a molar ratio of 6: 1: 2, and a graphite layer 5 was formed on the surface thereof to a thickness of 15 μm by screen printing. A conductive paste layer 6 having a silver content of 80% by weight or more is formed on the graphite layer 5 to a thickness of 30 μm and left at 150 ° C. to volatilize the organic solvent in the conductive paste. The silver layer was formed by making it harden | cure and it was set as the cathode part 7. FIG. The length La of the cathode portion 7 and the width Wa of the anode body 1 are determined in Equation 1 with a cutoff frequency f = 4 GHz and an effective dielectric constant e _ff = 9 as target values.

  In addition, for the anode region of the anode body with the insulator layer 3, the dielectric film 2 on the surface was removed with a laser, and the aluminum foil was exposed to form the anode portion 8.

  On the other hand, a two-terminal solid electrolytic capacitor 30b having a thick and short shape is cut into a rectangular shape having an aluminum foil width Wb of 5.0 mm and a length of 5.0 mm, and immersed in a 10% diammonium adipate aqueous solution, A dielectric film 2 was formed by anodic oxidation on the entire surface including a cut surface by applying a voltage. Thereafter, an insulating layer 3 is formed by applying and curing an epoxy resin with a width of 0.5 mm at a position 1.0 mm inside from one end in the length direction of the aluminum foil. A 1.0 mm region was defined as an anode region. Also, in the other region through the insulator layer 3, an epoxy resin is similarly applied at a position of 3.0 mm from the insulator layer 3 with a width of 0.5 mm and a thickness of 50 μm and cured to form the insulator layer 3 A region of 3.0 mm sandwiched between these two insulator layers 3 was used as a cathode region. This state is called an anode body with an insulator layer 3.

Subsequently, the solid electrolyte layer 4, the graphite layer 5, and the conductive paste layer 6 were sequentially laminated on the cathode region of the anode body with the insulator layer 3 by the same process as described above, thereby forming the cathode portion 7. The length Lb of the cathode portion 7 and the width Wb of the anode body 1 are determined in Equation 1 with a cutoff frequency f = 9 GHz and an effective dielectric constant e _ff = 9 as target values.

  Further, with respect to the anode region of the anode body with the insulator layer 3, the dielectric film 2 on both sides was removed with a laser, and the aluminum foil was exposed to form the anode portion 8.

  A lead made of a copper foil having a length of 10 mm, a width of 0.4 mm, and a thickness of 50 μm obtained by punching out each of the anode portions 8 of the two types of two-terminal solid electrolytic capacitors 30a and 30b prepared as described above. The anode parts 8 were electrically connected to each other using the ultrasonic welding method.

  Thereafter, the conductive adhesive 10 is applied to the element-side anode terminal 11a and the element-side cathode terminal 11b of the substrate 12 to a thickness of 40 μm, and the two types of the two-terminal solid electrolytic capacitors 30a and 30b described above are applied thereon. Each cathode part 7 and lead frame 9 are placed, electrically connected by thermosetting at 150 ° C., and molded with an exterior resin, so that the two-terminal solid electrolysis shown in FIG. A capacitor type low-pass filter 100 was obtained.

(Example 2)
In the low-pass filter of the second embodiment, only the elongated two-terminal solid electrolytic capacitor 30c of the two types of the two-terminal solid electrolytic capacitor of the first embodiment is replaced. A low-pass filter using the two-terminal type solid electrolytic capacitor shown in FIG. 2 (b) by the same construction method as in Example 1 except that the anode 8 and the lead frame 9 are connected by resistance welding. 101 was obtained.

The two-terminal solid electrolytic capacitor 30c having an elongated shape is formed as an anode body 1 using a tantalum wire having a diameter of 0.1 mm and a length of 7 mm, which has not been subjected to a surface enlargement process, as a valve metal. A dielectric film 2 was formed by applying a voltage of 80 V in an aqueous solution and anodizing. Subsequently, an epoxy resin is applied with a width of 0.5 mm and a thickness of 50 μm at a position 1.0 mm inside from one end in the length direction of the tantalum wire and cured to form the insulator layer 3, and insulation from one end surface An area of 1.0 mm up to the layer body 3 was defined as an anode area. In addition, in the other region through the insulator layer 3, an epoxy resin is similarly applied at a position of 5.0 mm from the insulator layer 3 with a width of 0.5 mm and a thickness of 50 μm and cured to form the insulator layer 3. A region of 5.0 mm formed and sandwiched between these two insulator layers 3 was defined as a cathode region. Then, the cathode part 7 and the anode part 8 were formed by the same process as the two-terminal solid electrolytic capacitor 30a of Example 1, and the two-terminal solid electrolytic capacitor 30c was obtained. The length Lc of the cathode portion 7 and the width Wc of the anode body 1 are determined in Equation 1 with a cutoff frequency f = 4 GHz and an effective dielectric constant e _ff = 14 as target values. The same two-terminal solid electrolytic capacitor 30b as in Example 1 was used.

  The anode portions 8 of the two types of two-terminal solid electrolytic capacitors 30b and 30c are arranged on a lead frame 9 made of a copper foil having a length of 10 mm, a width of 0.4 mm, and a thickness of 50 μm previously cut out by punching. The anode parts 8 were electrically connected using an ultrasonic welding method.

  Thereafter, the conductive adhesive 10 is applied to the element-side anode terminal 11a and the element-side cathode terminal 11b of the substrate 12 to a thickness of 40 μm, and the two types of the two-terminal solid electrolytic capacitors 30b and 30c described above are applied thereon. Each cathode part 7 and the lead frame 9 are placed, electrically connected by thermosetting at 150 ° C., and molded with an exterior resin (not shown), so that the two terminals shown in FIG. A solid electrolytic capacitor type low-pass filter 101 was obtained.

(Comparative example)
As a comparative example, it has a structure of a low-pass filter composed of a single unit of the conventional three-terminal solid electrolytic capacitor shown in FIG. 4, and the anode body 1 is not subjected to a surface enlargement process by etching or the like as in Example 1. An aluminum foil having a nominal formation voltage of 20 V and a thickness of 100 μm was used. This aluminum foil was cut into a rectangular shape having a width of 2.5 mm and a length of 7.0 mm, immersed in a 10% aqueous solution of diammonium adipate, a voltage of 25 V was applied, and the entire surface including the cut surface was anodized. Dielectric film 2 was formed. Thereafter, an insulating layer 3 is formed by applying and curing an epoxy resin with a width of 0.5 mm and a thickness of 50 μm at positions 1.0 mm inside from both ends in the length direction. The 1.0 mm region up to this point was used as the anode region, and the 4.0 mm region sandwiched between these two insulating layers 3 was used as the cathode region.

  Subsequently, the cathode part 7 and the anode part 8 are formed by the same process as that of the two-terminal solid electrolytic capacitor 30a of Example 1, and the anode part 8 has a length of 0.8 mm and a width previously cut out by punching. A lead frame 9 made of copper foil with a thickness of 2.5 mm and a thickness of 50 μm was connected using an ultrasonic welding method to obtain a three-terminal solid electrolytic capacitor.

  Thereafter, as in Example 1, the conductive adhesive 10 was applied to the element-side anode terminal 11a and the element-side cathode terminal 11b of the substrate 12 to a thickness of 40 μm, and the above three-terminal solid electrolytic capacitor was further formed thereon. Were electrically connected by thermosetting at 150 ° C., and molded with an exterior resin (not shown) to obtain a low-pass filter using the three-terminal solid electrolytic capacitor 102 shown in FIG.

  With respect to the low-pass filters according to Example 1, Example 2, and Comparative Example manufactured as described above, the frequency characteristics of insertion loss were measured with a vector network analyzer (37247D: manufactured by Anritsu), and the comparison result is shown in FIG. .

  As shown in FIG. 3, the low-pass filters of the first and second embodiments according to the present invention have a smaller insertion loss in the pass band, a narrower attenuation region of the insertion loss, and a lower attenuation gradient than the low-pass filter of the comparative example. I found it getting bigger. It can be presumed that the slanted two-terminal solid electrolytic capacitor has a large attenuation gradient, and the thick and short two-terminal solid electrolytic capacitor suppresses the rise in insertion loss in the high frequency band. In addition, because there is no dielectric with a high dielectric constant between the anode part and the cathode part that connect the anode bodies, the design of the low-pass filter has a higher attenuation gradient than the conventional low-pass filter that combines a capacitor and inductor. It has been found that this is easily possible.

  The conventional solid electrolytic capacitor type low-pass filter has a narrow passband and a small attenuation gradient, so noise removal in the power supply line and low-speed signal line was the main, but according to the present invention, the passband is extended to the high frequency band, In addition, since the attenuation gradient is large, it can be applied as a low-pass filter for high-speed lines.

DESCRIPTION OF SYMBOLS 1 Anode body 2 Dielectric film 3 Insulator layer 4 Solid electrolyte layer 5 Graphite layer 6 Conductive paste layer 7 Cathode part 8 Anode part 9 Lead frame 10 Conductive adhesive 11a Element side anode terminal 11b Element side cathode terminal 12 Substrate 13a External anode terminal 13b External cathode terminals 30a, 30b, 30c Two-terminal solid electrolytic capacitors 100, 101 Low-pass filter 102 Three-terminal solid electrolytic capacitors Wa, Wb, Wc Width L, La, Lb, Lc Length

Claims (2)

  A dielectric film made of an oxide of the valve action metal is formed on a surface of an anode body made of a linear, plate-like or foil-like valve action metal, and a solid electrolyte layer is formed on a part of the dielectric film. A cathode portion laminated with a cathode conductor layer is formed, an insulator layer is formed next to the cathode portion, and a portion of the anode body separated from the cathode portion via the insulator layer is formed as an anode portion. A plurality of two-terminal solid electrolytic capacitors having a structure in which a plurality of two-terminal solid electrolytic capacitors are connected in parallel, wherein the plurality of two-terminal solid electrolytic capacitors have different electrical lengths calculated from a cutoff frequency, The length of the cathode part of each of the two-terminal solid electrolytic capacitors is 1/4 of the electric length of each, and the surfaces of the anode bodies of the plurality of two-terminal solid electrolytic capacitors are both expanded. That it has not been processed Low-pass filter for the butterflies.   2. The low-pass filter according to claim 1, wherein each of the anode bodies of the plurality of two-terminal solid electrolytic capacitors is made of a different valve metal.

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