Abstract:
A solid electrolytic capacitor includes a porous sintered body made of valve metal, and an external anode terminal used for surface-mounting. The anode terminal is offset from the center of the sintered body, as viewed in the thickness direction or first direction of the sintered body. Further, the anode terminal is spaced away from the sintered body in a second direction which is perpendicular to the first direction. Between the sintered body and the anode terminal is formed a conductive path, which is inclined with respect to both the first and the second directions. The path comes closer to the anode terminal in the first direction as it goes farther away from the sintered body in the second direction.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a solid electrolytic capacitor comprising a porous sintered body made of a valve metal, and also relates to a manufacturing method of making the same.  
         [0003]     2. Description of the Related Art  
         [0004]     An example of a solid electrolytic capacitor includes a capacitor utilized for canceling noise generated by a device such as CPU, or for stabilizing power supply for an electronic device. (Refer to JP-A-2003-163137, for example.)  FIG. 19  illustrates an example of such a solid electrolytic capacitor. The illustrated solid electrolytic capacitor X includes a porous sintered body  90  made of a metal having valve action. The porous sintered body  90  is provided with an anode wire  91  partly protruding out thereof. The surface of the porous sintered body  90  is formed with a cathode conductive layer  92 . Each of the anode wire  91  and the conductive layer  92  is connected to a respective one of conductive members  93 ,  94  partly protruding from a sealing resin  95  to serve as an external anode terminal  93   a  and an external cathode terminal  94   a  for surface mounting. The frequency characteristic of the impedance Z at the solid electrolytic capacitor is given by the following formula. 
 
 Z =√{square root over (( R   2 +(1/ω C−ωL ) 2 ))}
        (ω: 2πf (f: frequency), C: capacity, R: resistance, L: inductance)        
 
         [0006]     As seen from the above formula, in a low frequency range in which the frequency is lower than the self-resonance point, “1/ωC” is dominant, where the impedance can be lowered by increasing the capacity of the solid electrolytic capacitor X. In a high frequency range in which the frequency is around the self-resonance point, the resistance “R” is dominant, where it is required to lower ESR (equivalent series resistance) of the solid electrolytic capacitor X. Further, in an ultrahigh frequency range in which the frequency is higher than the self-resonance point, “ωL” is dominant, where it is required to lower ESL (equivalent series inductance) of the solid electrolytic capacitor X.  
         [0007]     Recently, noise at a high frequency including high harmonic component is generated by a device having a high clock frequency, such as a CPU. Further, in accordance with an increase in operation speed and digitalization of electronic devices, a power supply system with high responsiveness has become necessary. For such use, the solid electrolytic capacitor X is also strongly desired to have a lowered ESL. In order to lower the ESL, the shape of the porous sintered body  90  may be changed, or a plurality of anode wires  91  may be provided. However, the conductive path between the external anode terminal  93   a  and the porous sintered body  90  includes a vertical portion  93   b,  at the conductive member  93 , that extends perpendicular to the longitudinal direction of a circuit board on which the solid electrolytic capacitor X is to be mounted. Through the vertical portion, the electrical current passes in a direction different from the adjacent portions of the conductive path. Thus, the length of the vertical portion is proportional to the inductance, and thus to the impedance at a high frequency range. Therefore, the solid electrolytic capacitor X cannot have a sufficiently lowered ESL.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been proposed under the above-described circumstances. It is therefore an object of the present invention to provide a solid electrolytic capacitor having a lowered ESL, and a manufacturing method of making the same.  
         [0009]     To achieve the above object, the present invention provides following technique.  
         [0010]     A solid electrolytic capacitor according to a first aspect of the present invention includes a porous sintered body made of a metal having valve action, and an external anode terminal for surface mounting. The external anode terminal is arranged at a position which is offset to one side relative to an intermediate portion of the porous sintered body, as viewed in a first direction, i.e., the thickness direction of the porous sintered body. Further, the anode terminal is arranged at a position which is apart from the porous sintered body in a second direction perpendicular to the first direction. A conductive path is formed between the porous sintered body and the external anode terminal. This conductive path is inclined relative to both of the first and the second directions. The path comes closer to the external anode terminal in the first direction, as proceeding apart from the porous sintered body in the second direction.  
         [0011]     Due to the above structure, the vertical portion extending in the first direction can be shortened, or be eliminated from the conductive path. Further, the conductive path can be bent by a minute angle. Thus, the conductive path can have a lowered inductance and thus have a small impedance at a high frequency range. Therefore, the structure is suitable to lower the ESL of the solid electrolytic capacitor. Further, the shortened vertical portion enables to make a thin solid electrolytic capacitor.  
         [0012]     According to a preferable embodiment of the present invention, the solid electrolytic capacitor further comprises an anode wire made of a metal having valve action. The anode wire protrudes from a surface of the porous sintered body that faces in the second direction. The wire is connected to the external anode terminal. The anode wire includes an inclined portion inclined relative to both of the first and the second directions to serve as the conductive path. Due to this, the inclined portion inclined relative to both of the first and the second directions can be easily formed at the conductive path.  
         [0013]     According to a preferable embodiment of the present invention, the anode wire is formed by bending a rod-shaped metal material having valve action.  
         [0014]     According to a preferable embodiment of the present invention, the anode wire is formed with a cutout at a portion to be bent. Due to this, no excessive stress is applied to the porous sintered body during the bending process.  
         [0015]     According to a preferable embodiment of the present invention, the anode wire includes a flat portion which is to be bent. The flat portion is formed by at least partly compressing a portion of the anode wire protruding from the porous sintered body. Due to this, the bending step can be performed by a reduced force, and thus the structure is suitable to reduce the stress applied to the porous sintered body.  
         [0016]     According to a preferable embodiment of the present invention, a ring is fitted around the base of the anode wire. Due to this, the stress applied to the porous sintered body is shared with the ring.  
         [0017]     According to a preferable embodiment of the present invention, the ring is made of a resin, so that the ring does not suffer from erosion during manufacture of the solid electrolytic capacitor.  
         [0018]     According to a preferable embodiment of the present invention, the solid electrolytic capacitor further comprises an anode wire protruding from a surface of the porous sintered body that faces in the second direction, and a conductive member interposed between the anode wire and the external anode terminal as viewed in the first direction. A solder fillet is provided to connect the conductive member and the external anode terminal, to form the conductive path. Due to this, the inclined portion is formed properly at the conductive path, and the solid electrolytic capacitor can have a lowered ESL.  
         [0019]     According to a preferable embodiment of the present invention, the solid electrolytic capacitor further comprises a plurality wires equivalent to the above-mentioned anode wire. Due to this, the solid electrolytic capacitor has a lowered ESR and ESL.  
         [0020]     According to a second aspect of the present invention, there is provided a method of making a solid electrolytic capacitor including a porous sintered body made of a metal having valve action. The method comprises the following steps. First, a porous sintered body provided with a metal rod having valve action is formed. The metal rod is caused to protrude from the porous sintered body in a second direction perpendicular to a first direction, that is, the thickness direction of the porous sintered body. Then, an anode wire is formed after the porous sintered body is formed. At this stage, the metal rod is bent so that the anode wire is formed with an inclined portion inclined relative to both of the first and the second directions. Then, an external anode terminal is bonded to an end of the anode wire. With this method, the solid electrolytic capacitor according to the first aspect of the present invention can be properly made.  
         [0021]     According to a preferable embodiment of the present invention, before the metal rod is bent, a cutout is made in the metal rod at a portion to be bent. Due to this, the bending step can be performed by an advantageously small force, thereby reducing the stress applied to the porous sintered body.  
         [0022]     According to a preferable embodiment of the present invention, the cutout is wedge-shaped in section, and includes one surface perpendicular to the longitudinal direction of the metal rod, and other surface inclined relative to the longitudinal direction of the metal rod. Due to this, the bending force can be prevented from being unduly applied to the metal during the bending step.  
         [0023]     According to a preferable embodiment of the present invention, a portion containing a part to be bent in the metal rod is compressed in the first direction before the bending is performed, thereby producing a flat portion, and wherein this flat portion is subjected to the bending. In this manner, the bending can be performed easily.  
         [0024]     According to a preferable embodiment of the present invention, the method further comprises the step of forming a ring at the base of the metal rod after the porous sintered body is formed and before the metal rod is bent.  
         [0025]     According to a preferable embodiment of the present invention, the ring is made of a resin. Due to this, the ring helps to reduce the bending force applied to the porous sintered body during the bending step. Further, the resin infiltrates into the porous sintered body from around the base of the metal rod. Thus, the relevant part of the porous sintered body is reinforced, and can be prevented from being broken in the bending step.  
         [0026]     Other features and advantages will be apparent from the following description of the embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]      FIG. 1  is a sectional view illustrating a solid electrolytic capacitor according to a first embodiment of the present invention.  
         [0028]      FIG. 2  is a perspective view illustrating the principal part of the solid electrolytic capacitor of the present invention.  
         [0029]      FIG. 3  is a sectional view illustrating a step of a method of making the solid electrolytic capacitor of the present invention.  
         [0030]      FIG. 4  is a sectional view illustrating another step of the method of making the solid electrolytic capacitor of the present invention.  
         [0031]      FIG. 5  is a sectional view illustrating another step of the method of making the solid electrolytic capacitor of the present invention.  
         [0032]      FIG. 6  is a sectional view illustrating another step of the method of making the solid electrolytic capacitor of the present invention.  
         [0033]      FIG. 7  is a sectional view illustrating another step of the method of making the solid electrolytic capacitor of the present invention.  
         [0034]      FIG. 8  is a sectional view illustrating a step of a modified method of making the solid electrolytic capacitor of the present invention.  
         [0035]      FIG. 9  is a perspective view illustrating the principal part of a solid electrolytic capacitor according to a second embodiment of the present invention.  
         [0036]      FIG. 10  is a sectional view illustrating a step of a modified method of making the solid electrolytic capacitor of the present invention.  
         [0037]      FIG. 11  is a sectional view illustrating another step of the modified method of making the solid electrolytic capacitor of the present invention.  
         [0038]      FIG. 12  is a sectional view illustrating another step of the modified method of making the solid electrolytic capacitor of the present invention.  
         [0039]      FIG. 13  is a sectional view illustrating the principal part of another example of solid electrolytic capacitor according to the present invention.  
         [0040]      FIG. 14  is a sectional view illustrating the principal part of another example of solid electrolytic capacitor according to the present invention.  
         [0041]      FIG. 15  is a sectional view illustrating the principal part of another example of solid electrolytic capacitor according to the present invention.  
         [0042]      FIG. 16  is a sectional view illustrating the principal part of another example of solid electrolytic capacitor according to the present invention.  
         [0043]      FIG. 17  is a sectional view illustrating another example of solid electrolytic capacitor according to the present invention.  
         [0044]      FIG. 18  is a perspective view illustrating the principal part of another example of solid electrolytic capacitor according to the present invention.  
         [0045]      FIG. 19  is a sectional view illustrating an example of a conventional solid electrolytic capacitor. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0046]     Preferred embodiments of the present invention will now be described below with reference to the accompanying drawings.  
         [0047]      FIGS. 1 and 2  illustrate an example of a solid electrolytic capacitor according to the present invention. As shown in  FIG. 1 , the solid electrolytic capacitor A of the present embodiment includes a porous sintered body  1 , anode wires  21 A,  21 B, external anode terminals  3 A,  3 B, external cathode terminals  6 A,  6 B, and a sealing resin  8 . The sealing resin  8  is not shown in  FIG. 2 .  
         [0048]     As shown in  FIG. 2 , the porous sintered body  1  is made of niobium having valve action, by compacting niobium powder to be a rectangular board and then sintering the board. In the sintered niobium powder making the porous sintered body  1 , adjacent niobium particles form minute gaps. The surface of the above sintered powder is formed with a dielectric layer (not shown) made of niobium oxide, for example. Further, the surface of the dielectric layer is formed with a solid electrolyte layer (not shown). The solid electrolyte layer is made of e.g. manganese dioxide or of conductive polymer, and preferably, covers all of the gaps between the niobium particles. Any material may be used to make the porous sintered body  1  if it has valve action, and tantalum may be used in place of niobium.  
         [0049]     As shown in  FIG. 1 , the external surface of the porous sintered body  1  is formed with a conductive layer  9  electrically connected to the solid electrolyte layer. The conductive layer  9  includes a graphite layer and also includes a silver layer formed on the graphite layer using silver paste, for example.  
         [0050]     As shown in  FIG. 2 , the anode wires  21 A,  21 B are made of a metal material having valve action, such as niobium, similarly to the porous sintered body  1 . Three of the anode wires protruding from a side surface  1   a  of the porous sintered body  1  are the anode wires  21 A for input, while the other three of the anode wires protruding from another side surface  1   b  of the porous sintered body are the anode wires  21 B for output. The anode wires  21 A,  21 B protrude in directions perpendicular to the thickness direction of the porous sintered body  1 .  
         [0051]     Each of the anode wires  21 A,  21 B includes a base  25 , an inclined portion  26 , and a tip end  27 . The base  25 , the inclined portion  26 , and the tip end  27  are formed by bending a niobium rod which is the material of the anode wires  21 A,  21 B. Each of the portions to be bent is formed with a cutout  28 . As shown in  FIG. 1 , the inclined portion  26  is inclined relative to the thickness direction of the porous sintered body  1  (the vertical direction in the figure), which is a first direction of the present invention, and is also inclined relative to the lateral direction in the figure, which is a second direction of the present invention.  
         [0052]     The base  25  of each of the anode wires  21 A,  21 B is provided with a resin ring  7 . In the present embodiment, the resin ring  7  fits around the base  25 , and partly infiltrates into the porous sintered body  1 . The resin ring  7  is made of epoxy resin, for example.  
         [0053]     As shown in  FIG. 2 , each of the two external anode terminals  3 A,  3 B is respectively connected to the three of the anode wires  21 A,  21 B, and is exposed from the sealing resin  8 , as shown in  FIG. 1 . The external anode terminals  3 A,  3 B are used for surface mounting of the solid electrolytic capacitor A onto a circuit board S. The external anode terminals  3 A,  3 B are rectangular metal plates bonded to the anode wires  21 A,  21 B by e.g. solder or conductive resin (neither of them is shown).  
         [0054]     As shown in  FIG. 1 , a cathode metal plate  60  is bonded to the under surface of the porous sintered body  1  via the conductive layer  9 . As shown in  FIG. 2 , the cathode metal plate  60  includes four extensions, two each of which serve as a respective one of the external cathode terminals  6 A,  6 B for input and output. Thus, the solid electrolytic capacitor A is provided with the external anode terminals  3 A,  3 B for input and output, as well as with the external cathode terminals  6 A,  6 B for input and output, that is, the so-called four terminal type.  
         [0055]     As shown in  FIG. 1 , the sealing resin  8  forms a resin package covering the porous sintered body  1  and the anode wires  21 A,  21 B for protection. The sealing resin  8  is made of a thermosetting resin such as epoxy resin.  
         [0056]     Next, a manufacturing method of the solid electrolytic capacitor A is described below with reference to  FIGS. 3-7 .  
         [0057]     First, as shown in  FIG. 3 , the porous sintered body  1  is made of niobium having valve action. The porous sintered body  1  is provided with niobium rods  2 A,  2 B protruding out thereof. Such porous sintered body  1  may be made by filling niobium fine powder into a mold, shaping it by pressure forming, and then sintering it, with the metal rods  2 A,  2 B partly inserted into the fine powder.  
         [0058]     After making the porous sintered body  1 , as shown in  FIG. 4 , the resin rings  7  are formed at the bases of the metal rods  2 A,  2 B. In forming the resin rings  7 , liquid epoxy resin having relatively high viscosity is dropped to cover the bases of the metal rods  2 A,  2 B. Preferably, the liquid epoxy resin infiltrates into the porous sintered body  1 . After a predetermined time in this state, the liquid epoxy resin is solidified to be resin rings  7 .  
         [0059]     After forming the resin rings  7 , as shown in  FIG. 5 , the metal rods  2 A,  2 B are formed with the cutouts  28 . The cutouts  28  are formed by partly cutting the metal rods  2 A,  2 B, using a cutting tool B. The cutouts  28  are formed at two portions of each of the metal rods  2 A,  2 B, at an upper portion near the tip end and a lower portion near the base. Each of the cutouts  28  includes surfaces  28   a,    28   b  and is wedge-shaped in section. In forming the cutouts  28 , the cutting tool B strikes the metal rods at a predetermined angle so that the surface  28   a  is formed to be perpendicular to the longitudinal direction of the metal rods  2 A,  2 B, while the surface  28   b  is formed to be inclined relative to the longitudinal direction of the metal rods  2 A,  2 B.  
         [0060]     After forming the cutouts  28 , as shown in  FIG. 6 , the metal rods  2 A,  2 B are bent to form the anode wires  21 A,  21 B. First, the porous sintered body  1  is fixed by a clamp C 2 . The tip end  21  of the metal rod  2 A is held by a clamp C 1 . Next, the clamp C 1  is moved downward relative to the clamp C 2 , to apply a bending moment to the metal rod  2 A. As the metal rod  2 A is formed with two cutouts  28 , the flexural rigidity is lowered at the portions formed with the cutouts  28 . Thus, these portions of the metal rod  2 A are bent in the closing direction of the cutouts  28 . Through the bending process, the anode wires  21 A,  21 B each including the tip end  27 , the inclined portion  26 , and the base  25  are made. The clamp C 1  is pressed down at a predetermined distance so that the inclined portion  26  is inclined at a desired angle.  
         [0061]     The cutouts  28  are useful for bending only the desired portions of the metal rods  2 A,  2 B. Further, due to the cutouts, the porous sintered body  1  can be prevented from unduly receiving bending force during the bending process. Still further, in the present embodiment, the resin rings  7  alleviate the bending force applied to the porous sintered body  1 . The inventor carried out a following experiment. A porous sintered body  1  having a thickness of 1.5 mm was provided with a metal rod  2 A′ having a diameter of 0.5 mm and a protruding length of 2 mm. The tip end of the metal rod  2 A′ was pressed down by 0.5 mm to be bent, and was provided with a resin ring  7 . The experiment proved that the resin ring decreased the stress applied to such porous sintered body  1  to ⅕.  
         [0062]     After forming the anode wires  21 A,  21 B, the porous sintered body  1  is formed with the dielectric layer (not shown) and the solid electrolyte layer (not shown). In forming the dielectric layer, either of the anode wires  21 A,  21 B is held while the porous sintered body  1  is immersed in chemical liquid containing an aqueous solution of phosphoric acid, for example. In this way, the porous sintered body  1  is anodized and the dielectric layer containing niobium pentoxide is formed. In forming the solid electrolyte layer, a step in which, for example, the porous sintered body  1  is immersed in an aqueous solution of e.g. manganese nitrate and then a step in which the porous sintered body is sintered, are repeated several times.  
         [0063]     After forming the solid electrolyte layer, as shown in  FIG. 7 , the conductive layer  9  is formed by laminating a graphite layer and a silver layer. Then, via the conductive layer  9 , the cathode metal plate  60  is bonded to the under surface of the porous sintered body  1 . The tip ends  27  of the anode wires  21 A,  21 B are bonded to the external anode terminals  3 A,  3 B. Thereafter, the porous sintered body  1  and the anode wires  21 A,  21 B are covered by the sealing resin  8  to complete the solid electrolytic capacitor A shown in  FIG. 1 .  
         [0064]     Next, functions of the solid electrolytic capacitor A will be described below.  
         [0065]     According to the present embodiment, as shown in  FIG. 2 , the anode wires  21 A,  21 B serve as conductive paths between the porous sintered body  1  and the external anode terminals  3 A,  3 B. As shown in  FIG. 1 , the conductive paths are inclined at the inclined portions  26  relative to the thickness direction of the porous sintered body  1  (the vertical direction in the figure) and to the longitudinal direction of the circuit board S (the lateral direction in the figure). The inclined portions are inclined in a manner such that they come closer to the external anode terminals  3 A,  3 B as proceeding apart from the porous sintered body  1 . Thus, the conductive paths are formed neither with a portion extending in the vertical direction in the figure nor with a portion bent through an acute angle. Therefore, the conductive paths between the porous sintered body  1  and the external anode terminals  3 A,  3 B have small inductances and thus have small impedances at a high frequency range. Accordingly, the entire solid electrolytic capacitor A has a small ESL and thus is suitable for improving noise cancellation property at a high frequency range and for supplying power with high responsiveness.  
         [0066]     Further, as described above, the cutouts  28  and the resin rings  7  reduce the stress applied to the porous sintered body  1  during the bending process shown in  FIG. 6 . Thus, it is possible to solve the problems that the conductive paths between the anode wires  21 A,  21 B and the porous sintered body  1  are blocked, and that the anode wires  21 A,  21 B unduly come off the porous sintered body  1 . In this way, the solid electrolytic capacitor A is prevented from inappropriate conduction or insulation due to the above problems, and thus the solid electrolytic capacitor A can fulfill its function. Still further, as the resin rings  7  partly infiltrate into the porous sintered body  1 , the porous sintered body  1  is reinforced. The resin rings  7  have high chemical corrosion resistance, which is preferable to prevent undue erosion during manufacture of the solid electrolytic capacitor A. However, the present invention is not limited to this, but a metal ring-shaped member may be fitted around the metal rods  2 A,  2 B.  
         [0067]     In the present embodiment, a plurality of anode wires  21 A,  21 B are provided, so that an electric current can be divided into the plurality of anode wires  21 A,  21 B. Thus, the solid electrolytic capacitor A can have a lowered ESR and a lowered ESL. Further, as the plurality of anode wires  21 A,  21 B are provided, each of the anode wires  21 A,  21 B can be thinned down. Thus, in manufacturing the solid electrolytic capacitor A, the bending process of the metal rods  2 A,  2 B shown in FIG.  6  can be facilitated.  
         [0068]     In the present embodiment, the bending process of the metal rods  2 A,  2 B is performed before forming the dielectric layer. In this way, the dielectric layer is desirably prevented from being unduly broken in the bending process. However, the present invention is not limited to the above-described embodiment, but before performing the bending process, the dielectric layer and the solid electrolyte layer may be first formed and then the conductive layer  9  shown in  FIG. 1  may be formed.  
         [0069]     In the present embodiment, as shown in  FIG. 5 , the cutout s  28  are provided to facilitate the above-described bending process, though the present invention is not limited to this. For example, as shown in  FIG. 8 , the metal rod  2 A may be fixed by the clamp C 1  and by another clamp C 3 , while the clamp C 1  moves downward to bend the metal rod  2 A. Even in this way, it is possible to prevent excess stress from being applied to the porous sintered body  1 .  
         [0070]      FIG. 9  illustrates another example of a solid electrolytic capacitor according to the present invention. The illustrated embodiment differs from the above-described embodiment in that the anode wire  22 A is partly flat, and the anode wire  22 A is arranged at the lower portion of the porous sintered body  1  as seen in the figure. The number and arrangement of the anode wires for input and output are similar to the above-described embodiment.  
         [0071]     The anode wire  22 A is circular in section at the base  25 , but is flat, in the vertical direction of the figure, in section at the inclined portion  26  and the tip end  27 . The base  25  is covered by the resin ring  7 , similarly to the above-described embodiment. The anode wire  22 A is arranged at a portion lower than the intermediate portion in the thickness direction of the porous sintered body  1 .  
         [0072]     Next, a manufacturing method of such solid electrolytic capacitor is described below. First, the porous sintered body  1  shown in  FIG. 10  is made. The porous sintered body  1  is provided with the metal rods  2 A,  2 B arranged at the lower portion in the figure. A portion adjacent to the each tip end of the metal rods  2 A is compressed, in the vertical direction of the figure, by a compressor P to make a flat portion  29 . Next, as shown in  FIG. 11 , a resin ring  7  is formed so as to cover the base  25  of each of the metal rods  2 A,  2 B. Thereafter, as shown in  FIG. 12 , the portion adjacent to the tip end of the flat portion  29  is pressed downward by the clamp C 1 . In this way, the anode wires  22 A,  22 B having flat inclined portion  26  and flat tip end  27  can be made.  
         [0073]     In the present embodiment, as the flat portion  29  is provided, the bending process requires a small force. Thus, it is suitable to reduce the bending force applied to the porous sintered body  1 . Further, as shown in  FIG. 12 , the metal rod  2 A is selectively bent at the portion around the right-side surface of the clamp C 1  in the figure, and at the end of the flat portion  29  adjacent to the porous sintered body  1 . Thus, the bending process can be facilitated. The cutouts  28  shown in  FIG. 5  may also be formed before the bending process shown in  FIG. 12 . In this way, the bending process may be further facilitated.  
         [0074]     As shown in  FIG. 9 , the distance between the anode wires  22 A,  22 B and the respective external anode terminals  3 A,  3 B is shortened, so that the anode wires  22 A,  22 B are bent by a minute angle. Thus, in making such solid electrolytic capacitor, the stress applied to the porous sintered body  1  during the bending process can be reduced. Therefore, the solid electrolytic capacitor can be provided with conductive paths, each of which has shortened height and a minute bended angle at its bending portion, between the porous sintered body  1  and the external anode terminals  3 A,  3 B. As a result, the conductive paths have small inductances, and thus the solid electrolytic capacitor has a lowered ESL.  
         [0075]      FIG. 13  illustrates a modification of the present invention. The illustrated embodiment differs from the above-described two embodiments in that a linear anode wire  23 A, conductive member  4 , and a solder fillet  5  are provided.  
         [0076]     The anode wire  23 A linearly projects from one surface of the porous sintered body  1 , and is substantially the same as the metal rod  2 A shown in  FIG. 3 , for example. The conductive member  4  is arranged between the anode wire  23 A and the external anode terminal  3 A, for conduction therebetween. The solder fillet  5  connects the conductive member  4  and the external anode terminal  3 A. The solder fillet  5  is formed at the left side surface of the conductive member  4 , and is a tapered shape having a gently inclined surface.  
         [0077]     In the third example, the solder fillet  5  provides an inclined portion to the conductive path between the porous sintered body  1  and the external anode terminal  3 A. Thus, similarly to the above-described first and second examples, the solid electrolytic capacitor has a lowered ESL.  
         [0078]     In another embodiment shown in  FIG. 14 , the tapered solder fillet  5  is formed at the left side surface of the conductive member  4  and also at the left end surface of the anode wire  23 A. In the fourth example, it is possible to form an inclined conductive path between the left end of the anode wire  23 A and the external anode terminal  3 A via the solder fillet  5 . Thus, the conductive path can have shortened vertical portion, thereby reducing the ESL.  
         [0079]     In another example shown in  FIG. 15 , the right end of the conductive member  4  and the right end of the external anode terminal  3 A are aligned. According to the present embodiment, differently from the embodiment shown in  FIG. 13 , no portions of the external anode terminal  3 A protrude beyond the conductive member  4  toward the porous sintered body  1 . Thus, the conductive path between the anode wire  23 A and the external anode terminal  3 A can be advantageously inclined, thereby reducing the ESL. In the embodiment shown in  FIG. 1 , if the protruding portions of the external anode terminals  3 A,  3 B are shortened, the effect of reducing the ESL may be further achieved.  
         [0080]     Another embodiment shown in  FIG. 16  differs from the third through fifth embodiments shown in  FIGS. 13-15 , in that the solder fillet  5  is not formed at the conductive member  4  but formed only at the anode wire  23 A. The anode wire  23 A is made of a metal having valve action such as niobium or tantalum, and thus typically has low solderability. In the present embodiment, a portion of the anode wire  23 A close to its tip end is coated by a plating  24  to improve the solderability. The plating  24  is formed by coating with palladium as the base and then by coating with nickel thereon. According to the present embodiment, it is also possible to provide the inclined conductive path between the anode wire  23 A and the external anode terminal  3 A, thereby reducing the ESL.  
         [0081]      FIGS. 17 and 18  illustrate another example of the present invention. The present embodiment differs from any of the above-described embodiments in that each of the external anode terminals  3 A,  3 B includes an inclined portion  32 .  
         [0082]     The anode wires  21 A,  22 A linearly protrude from the respective side surfaces  1   a,    1   b  of the porous sintered body  1 . Each of the external anode terminals  3 A,  3 B is formed, through a bending process, with a main plate  31 , the inclined portion  32 , and a terminal  33 . The inclined portion  32  has a gentle inclined angle so that no vertical portion is formed at the conductive path. As shown in  FIG. 17 , the terminal  33  is partly exposed from the sealing resin  8 , so that the exposed portion is used for surface mounting. In the present embodiment, it is also possible to lower the ESL at the solid electrolytic capacitor A. Especially in the solid electrolytic capacitor A having a relatively large porous sintered body  1 , the external anode terminals  3 A,  3 B are also large and thus are suitable to be bent into the shape shown in  FIGS. 17 and 18 .  
         [0083]     The solid electrolytic capacitor according to the present invention is not limited to the above-described embodiments. Specific structure of the solid electrolytic capacitor according to the present invention may be modified variously.  
         [0084]     The material of the porous sintered body and the anode wires may be any metal having valve action such as niobium and tantalum. Specific use of the solid electrolytic capacitor according to the present invention is not limited, either.