Solid electrolytic capacitor with an improved mounting property, and manufacturing method of the same

A solid electrolytic capacitor includes a capacitor element, an anode terminal, a cathode terminal, and an outer casing resin. The anode and cathode terminals constitute parts of the mounting surface, and are drawn immediately below the capacitor element. The anode terminal and the cathode terminal are electrically coupled with an anode leader of the capacitor element and a cathode layer, respectively. The outer casing resin covers the capacitor element, and exposes the anode and cathode terminals on the mounting surface. At least one recess is provided on a mounting surface side of at least one of the anode and cathode terminals having a larger area projected onto the mounting surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid electrolytic capacitor and a manufacturing method of the same.

2. Description of the Related Art

Capacitor element61includes anode body62, anode leader63, dielectric oxide film64, solid electrolyte65, and cathode layer66. Anode body62is formed of a valve metal foil. Anode leader63is provided at one end of anode body62, and dielectric oxide film64is formed on a surface of another end of anode body62. Solid electrolyte65made of a conductive polymer is provided on dielectric oxide film64. In cathode layer66, a carbon layer is laminated on solid electrolyte65, and a silver paste layer is laminated on the carbon layer.

Anode terminal67and cathode terminal68are formed of metal plates which are made by machining copper lead frames. Anode terminal67includes flat portion70, leading portions72, and placement portions74. Flat portion70is exposed from outer casing resin69at mounting surface76. Leading portions72are bent obliquely upward from both ends of flat portion70. Placement portions74are coupled with a lower surface of anode leader63. Cathode terminal68includes flat portion71, leading portions73, and placement portions75. Flat portion71is exposed from outer casing resin69at mounting surface76. Leading portions73are bent obliquely upward from both ends of flat portion71. Placement portions75are coupled with a lower surface of cathode layer66.

Outer casing resin69is made of an electrically insulating resin such as an epoxy resin. Outer casing resin69covers capacitor element61such that anode terminal67and cathode terminal68are exposed in the same plane with mounting surface76in the flat shape.

In the above mentioned configuration, anode terminal67and cathode terminal68are provided such that anode terminal67and cathode terminal68are arranged adjacent to each other as close as possible, which shortens a path of current passing through capacitor element61from wiring of a circuit board. Therefore, equivalent series resistance (ESR) and equivalent series inductance (ESL) are decreased in the solid electrolytic capacitor. For example, Japanese Patent Unexamined Publication No. 2003-133177 discloses this kind of solid electrolytic capacitor.

The state in which the conventional solid electrolytic capacitor is mounted on the circuit board will be described with reference toFIG. 8.FIG. 8is a sectional view showing a mounted state of the solid electrolytic capacitor shown inFIG. 7A. Lands78are provided in circuit board77. Lands78correspond to positions of anode terminal67and cathode terminal68which are exposed at mounting surface76, and lands78have shapes substantially similar to those of the terminals. After a solder cream is applied onto lands78, the solid electrolytic capacitor is placed on lands78, and the solder is melted by high-temperature reflow to join the solid electrolytic capacitor to circuit board77. At this point, when an area of cathode terminal68in mounting surface76is larger than that of anode terminal67, the melted solder is easily aggregated in a central portion of cathode terminal68. Therefore, soldering layer79A on anode terminal67differs from soldering layer79B on cathode terminal68in thickness, which sometimes results in a problem that mounting property is impaired such that the solid electrolytic capacitor is mounted while inclined or floating.

SUMMARY OF THE INVENTION

In view of the foregoing an object of the invention is to provide a solid electrolytic capacitor having excellent high frequency properties, in which the mounting property is improved, and a manufacturing method thereof. A solid electrolytic capacitor according to the present invention has a capacitor element, an anode terminal, a cathode terminal, and an outer casing resin. The capacitor element includes an anode body, an anode leader, a dielectric oxide film, a solid electrolyte, and a cathode layer. The anode body is made of a valve metal, the anode leader is provided at one end of the anode body. The dielectric oxide film is formed on a surface of the anode body at a side opposite a side on which the anode leader is provided. The solid electrolyte is formed on the dielectric oxide film, and the cathode layer is formed on the solid electrolyte. The anode and cathode terminals are drawn immediately below the capacitor element to constitute parts of a mounting surface. The anode terminal is electrically coupled with the anode leader, and the cathode terminal is electrically coupled with the cathode layer. The outer casing resin covers the capacitor element, and exposes the anode and cathode terminals from the mounting surface. A recess is provided on the mounting surface side of at least one of the anode terminal and cathode terminal that has a larger area projected onto the mounting surface.

According to the structure, the melted solder flows into the recess during the mounting, the solder thicknesses are equalized on the anode terminal and the cathode terminal, therefore, the mounting property is improved in the solid electrolytic capacitor. Furthermore, the conductivity with the circuit board is not impaired because contact areas between the anode terminal and/or the cathode terminal and the circuit board are increased by the recess. Accordingly, the high-frequency properties of the ESR and ESL properties of the solid electrolytic capacitor are improved as well as the mounting property.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1Ais a sectional side view of a solid electrolytic capacitor according to an exemplary embodiment of the present invention,FIG. 1Bis a sectional front view thereof, andFIG. 1Cis a bottom view of the same.FIG. 1Ashows a sectional view taken along line1A-1A ofFIG. 1C, andFIG. 1Bshows a sectional view taken along line1B-1B ofFIG. 1C.

Capacitor element1includes anode body2, anode leader3, insulator layer4, dielectric oxide film5, solid electrolyte6, and cathode layer7. Anode body2is formed of a valve metal foil. Insulator layer4divides anode body2into an anode portion and a cathode portion. Anode leader3is provided at one end which is the anode portion of anode body2, and dielectric oxide film5is formed on the surface of the other end which is the cathode portion of anode body2. Solid electrolyte6made of a conductive polymer is provided on dielectric oxide film5. In cathode layer7, a carbon layer is laminated on solid electrolyte6, and a silver paste layer is laminated on the carbon layer.

Anode body2is made of a valve metal such as aluminum, tantalum, niobium, and titanium, and a portion where dielectric oxide film5is formed may be made of a porous sintered material including valve metal powders. Solid electrolyte6is made of a conductive polymer such as polypyrrole, polythiophene, and polyaniline. Alternatively, solid electrolyte6may be made of manganese oxides such as manganese dioxide. Anode terminal8and cathode terminal9are formed of metal materials which are made by machining plate-shape lead frames. Outer casing resin10is made of an insulating resin such as an epoxy resin. A lower surface of outer casing resin10becomes mounting surface21.

Anode terminal8is electrically coupled with anode leader3, and cathode terminal9is electrically coupled with cathode layer7. Anode terminal8and cathode terminal9are drawn immediately below capacitor element1, and each of anode terminal8and cathode terminal9constitutes a part of mounting surface21. That is, flat portion11is provided in anode terminal8while exposed from outer casing resin10, and flat portion11is arranged in a same plane with mounting surface21. Flat portion12is provided in cathode terminal9while exposed from outer casing resin10, and flat portion12is arranged in a same plane with mounting surface21. Flat portion11is formed in a rectangular shape, and flat portion12is formed in a T-shape. Flat portion12is provided close onto a side of flat portion11while going beyond a central portion of mounting surface21from an end portion of mounting surface21. Flat portions11and12on mounting surface21have symmetrical shapes with respect to a C-axis which is of a direction connecting flat portion11and flat portion12.

Leading portions13are provided in both end portions of anode terminal8in a direction which is not a thickness direction while being orthogonal to the C-axis. Leading portions13are obliquely raised from flat portion11so as to be separated from each other. Similarly, leading portions14are provided in both end portions of cathode terminal9in a direction which is not a thickness direction while being orthogonal to the C-axis. Leading portions14are obliquely raised from flat portion12so as to be separated from each other. As shown inFIG. 1B, inclination angles θ1are formed by leading portions13and14and flat portions11and12respectively. The inclination angle θ1ranges from 30° to 60°.

Flat placement portions15and16are provided in upper surfaces of leading portions13and14, and placement portions15and16are coupled with lower surfaces of anode leader3and cathode layer7, respectively. There are steps ranging from 0.1 to 0.15 mm between placement portions15and16and flat portions11and12respectively. Placement portions15and16and flat portions11and12are coupled by leading portion13and14, respectively. That is, each of placement portions15and flat portion11are formed in a stepwise shape, and each of placement portions16and flat portion12are formed in the stepwise shape.

Recesses17are provided on the side of mounting surface21of cathode terminal9while exposed onto the side of mounting surface21. Recesses17are provided in both sides of a longitudinal rod portion of T-shape cathode terminal9. One side of recess17is formed by wall surface18of cathode terminal9, and wall surface18made of the metal is obliquely raised from flat portion12. The other side is formed by wall surface19of outer casing resin10. The whole of wall surface18is curved so as to be swelled toward the direction opposite mounting surface21, and the whole of wall surface18is formed by an arc in which an angle φ1ranges from 10° to 90° in a cross section on line1B-1B. On the other hand, wall surface19is substantially perpendicular to mounting surface21. As shown inFIG. 1C, an opening intersecting mounting surface21of recess17has a shape in which an ellipse is cut into halves in parallel with the center line, and surroundings of the opening are closed.

In comparison of an area projected onto mounting surface21, the area of cathode terminal9is 2 to 6 times larger than the area of cathode terminal9. In flat portion11of anode terminal8, a tin metal layer (not shown) is formed in the surface on the side of mounting surface21. Also in flat portion12of cathode terminal9, the tin metal layer (not shown) is formed in the surface on the side of mounting surface21, where recess17is exposed. A tin plating layer whose thickness ranges, for example, from 3 to 10 μm is formed by metal plating, and is melted by a laser so as to be solidified to form the tin metal layer.

Hereinafter, a method of producing the solid electrolytic capacitor of the present embodiment will be described. The surface of rectangular aluminum foil having the thickness of 100 μm as anode body2is roughened by an electrochemically etching process. The processed foil is anodized by voltage application in an aqueous ammonium adipate solution to form an aluminum oxide layer as dielectric oxide film5.

Then, insulator layer4is formed by a polyimide adhesion tape, and one end of anode body2is dipped in a manganese nitrate solution. The one end of anode body2is divided to become the cathode portion by insulator layer4. Then, the manganese nitrate is thermally decomposed to make a manganese oxide layer which becomes a part of solid electrolyte6. Thereafter, the manganese oxide layer is dipped in a mixture solution containing pyrrole monomer and sodium propyl-naphthalene sulfonate, and electrolytic oxidative polymerization is performed to form solid electrolyte6made of polypyrrole.

The cathode portion side is dipped in a colloidal carbon suspending solution to apply it onto solid electrolyte6, and the suspending solution is dried to form the carbon layer. After a silver paste is applied onto the cathode portion side, the silver paste is cured to form the silver paste layer on the carbon layer, and thereby cathode layer7including the carbon layer and the silver paste layer is formed. Thus, capacitor element1is produced.

FIG. 2is a perspective view showing a main part of a lead frame, in which recess17shown inFIGS. 1A to 1Cis formed. Lead frame22is formed by a belt-shape metal member having the thickness of 0.1 mm. The metal member is made of copper or a copper alloy. A nickel underlaying plating layer and a tin plating layer on the nickel layer are formed in one surface of the metal member. The surface of the metal member becomes the side of mounting surface21. The metal member is punched to provide plural pairs of punched portions55and56which become anode terminal8and cathode terminal9. The pairs of punched portions55and56are provided at constant intervals. Thus, lead frame22is produced.

Bending portions51and52and placement portions15and16are provided in punched lead frame22by press metallic dies. Bending portions51and52become leading portions13and14, and placement portions15and16are formed in the stepwise shape on bending portions51and52. Bending portions51are bent from both ends of flat lower surface53of lead frame22which becomes flat portion11of anode terminal8, and bending portions51are bent obliquely upward at an inclination angle θ1with respect to lower surface53so as to be separated from each other. Similarly, bending portions52are bent from both ends of flat lower surface54of lead frame22which becomes flat portion12of cathode terminal9, and bending portions52are bent obliquely upward at an inclination angle θ1with respect to lower surface54so as to be separated from each other.

Using the press dies, parts of lower surface54and bending portions52are raised and bent so as to be swelled toward the direction opposite lower surface54, and thereby wall surfaces18each which becomes a part of recess17are formed. Then, as shown inFIG. 1B, paste conductive bonding agent27is applied on surfaces of placement portions16, lower surface54, and wall surfaces18to bond cathode layer7to punched portion56. Placement portions15of punched portion55and anode leader3are coupled with each other by laser welding. Thus, capacitor element1is coupled with lead frame22.

Then, an upper die and a lower die are prepared. A cavity is provided in the upper die, and the cavity accommodates capacitor element1, placement portions15and16, bending portions51and52, and wall surfaces18. The lower die comes into contact with flat portions11and12. Lead frame22is clamped with the upper and lower dies, and outer casing resin10is formed with the epoxy resin by transfer molding. Therefore, outer casing resin10is formed so as to cover capacitor element1, placement portions15and16, leading portions13and14, and wall surfaces18, and to expose flat portions11and12.

Outer casing resin10includes a curing body of epoxy resin and inorganic particles dispersed in the curing body. For example, the curing body is made of dicyclopentadiene type epoxy resin as a main-skeleton and a phenolic novolac resin. The inorganic particles is made of, for example, silica having an average grain size of 60 μm to 80 μm, and the curing body contains the inorganic particles at 80% to 90% in terms of mass.

Then, portions of outer casing resin10are removed to expose wall surfaces18by a laser apparatus.FIG. 3is a schematic view showing laser irradiation points23in mounting surface21after outer casing resin10is formed.

For example, YAG (Yttrium aluminum garnet) laser is used as the laser apparatus, first laser irradiation is performed while laser irradiation energy is set in a range of 20 J to 40 J.

As shown inFIG. 3, in the first laser irradiation, lower surfaces53and54and the surface of the portions of outer casing resin10are irradiated with the laser at laser irradiation points23. Lower surfaces53and54correspond to flat portions11and12exposed to mounting surface21, and the portions of outer casing resin10cover wall surfaces18. Distances between laser irradiation points23are 0.1 mm in both the C-axis direction and the D-axis direction orthogonal to the C-axis. After the laser is scanned along the D-axis direction, laser scanning positions are sequentially moved along the C-axis direction. The portions of outer casing resin10on wall surfaces18are removed by the first laser irradiation, and recesses17each whose one side becomes wall surface19composed of outer casing resin10are formed in punched portion56which becomes cathode terminal9. In lower surfaces53and54of punched portions55and56, the tin plating layer is melted and solidified so as to be raised around laser irradiation point23having a diameter of about 0.1 mm.

Then, using the same laser apparatus, second laser irradiation is performed on the same conditions as the first laser irradiation. The second laser irradiation removes dirt on wall surfaces18. As with lower surfaces53and54, the second laser irradiation melts and solidifies the tin plating layer on wall surfaces18such that the tin plating layer is raised around laser irradiation point23having the diameter of about 0.1 mm.

Finally, lead frame22is cut to form pieces of the solid electrolytic capacitor. Lead frame22is cut at portions which are connected to lower surface53or lower surface54and extended toward outside planes from mounting surface21of outer casing resin10.

Thus, in the present embodiment, after outer casing resin10is formed such that wall surfaces18coupled to flat portion12are covered while lower surface54corresponding to flat portion12is exposed, the portions of outer casing resin10is removed to expose wall surfaces18. Therefore, a variation in machining dimension of wall surfaces18has no influence on a variation in exposure of flat portion12, so that flat portion12can accurately be arranged in a same plane with mounting surface21. This ensures flatness of mounting surface21and improves the mounting property.

The portions of outer casing resin10which cover wall surfaces18are carbonized and removed by the laser irradiation. Therefore, even if the variation is generated in the machining dimension of wall surfaces18, recesses17each surrounded by wall surface18and wall surface19can securely be formed. Additionally, recesses17having excellent solder wetting properties can securely be formed.

Hereinafter, a method of attaching the solid electrolytic capacitor of the present embodiment to a circuit board will be described.FIG. 4is a sectional view showing the state in which the solid electrolytic capacitor of the present embodiment is mounted on a circuit board. Lands25are provided on circuit board24. Lands25correspond to positions of anode terminal8and cathode terminal9which are exposed onto the side of mounting surface21, and lands25have shapes substantially similar to those of the terminals. Lands25are slightly larger than the terminals. After the solder cream is applied onto lands25, the solid electrolytic capacitor of the present embodiment is placed on the lands25, and the solder is melted by high-temperature reflow to attach the solid electrolytic capacitor to circuit board24.

In the solid electrolytic capacitor of the present embodiment, recesses17are provided on cathode terminal9. Therefore, the melted solder in mounting the solid electrolytic capacitor onto the circuit board24is accommodated in recesses17, and the thicknesses of soldering layers26becomes substantially equal to each other in anode terminal8and cathode terminal9. As a result, the mounting property is improved, and the solid electrolytic capacitor can be mounted while the high-frequency properties are improved.

Recesses17are preferably formed while bent so as to be swelled toward the direction in which recesses17are separated away from mounting surface21. Therefore, in a process during which the melted solder is wetting the metal surfaces of recesses17, swelling of the solder generated toward outer casing resin10by surface tension of the solder is particularly decreased in a deep portion of recesses17. That is, the swelling of the solder generated by surface tension of the solder can be decreased, which hardly includes a bubble to form soldering layer26over recesses17.

Recesses17are preferably provided at two points so as to face each other with respect to the C-axis as a first axis connecting anode terminal8and cathode terminal9. When the solder is formed in recesses17, the surface tensions generated at both end portions intersecting the D-axis ofFIG. 3in cathode terminal9act so as to cancel each other. Therefore, the solid electrolytic capacitor is prevented from being inclined or floating, and the mounting property is further improved. InFIGS. 1C and 3, recesses17are provided at two points so as to face each other with respect to C-axis. Alternatively, recesses17may be provided at two points so as to face each other with respect to the D-axis as a second axis orthogonal to the C-axis.

It is preferable to form leading portions14while bent obliquely upward from flat portion12, and to form wall surfaces18in the inclined surfaces of leading portions14. Thus, the inclined surfaces of leading portions14are exposed as wall surfaces18, so as to allow the soldering to be performed from mounting surface21to leading portions14. Therefore, connection resistance is decreased from mounting surface21to capacitor element1, so as to further improve the high-frequency properties.

It is preferable to form leading portions14while bent obliquely upward from flat portion12, and to form wall surfaces18by raising cathode terminal9so as to couple to the inclined surfaces of leading portions14and flat portion12. Thereby, when cathode layer7and cathode terminal9are coupled with each other, deformation of leading portions14can be suppressed. That is, although physical stress may be generated by the deformation of leading portion14, the physical stress on capacitor element1can be reduced so as to decrease leak current of capacitor element1.

Because the leading distance to capacitor element1can be shortened by increasing the contacting area of recesses17and lands25, the high-frequency properties is improved.

Wall surfaces19each which is of a part of wall surface in recess17is preferably formed by outer casing resin10. Thereby, thanks to outer casing resin10in which the solder leakage is not generated, the melted solder generated at both end portions intersecting the D-axis acts so as to be correctly aligned with a patterns of a circuit board in mounting surface21. Accordingly, the solid electrolytic capacitor is prevented from being inclined or floating, and the mounting property is further improved.

The each surface of the metal members of recesses17is preferably melted by the laser irradiation after recesses17are exposed. In order to secure soldering properties, the metal layer made of Sn, an alloy of Sn and Ag, Pb, Bi, In, or Cu, silver, or gold is formed in the each surface of the metal members of recesses17by plating or evaporation. The metal layer surface is melted and solidified by the laser irradiation, so as to decrease the oxidation film. As a result, the metal layer is densified to enhance the solder wetting properties in the surfaces of recesses17.

Particularly, in the plating layer formed via electrolytic plating or nonelectrolytic plating, the deposited particles are collected together while having grain boundaries therebetween, and the thickness of the plating layer ranges from 1 μm to 20 μm. The plating layer is melted by the laser irradiation, and the melted plating layer is rapidly solidified, which eliminates the grain boundary to form the dense metal layer. The metal layer melted and solidified by the laser irradiation is formed over the surfaces of the anode terminal and cathode terminal so as to allow the solder wetting property to be further enhanced.

The laser irradiation is preferably scanned so as to correspond to at least one of anode terminal8and cathode terminal9which are exposed on mounting surface21. Thereby, using the one laser apparatus, the surfaces of flat portions11and12can continuously be melted and outer casing resin10can be removed on recesses17while irradiation energy is kept constant.

The metal layer on the surfaces of recesses17can be melted by performing the laser irradiation plural times, and thereby the solder wetting properties are enhanced on the surfaces of flat portion12and recesses17. In the plural-time laser irradiation, the same irradiation points may be irradiated in each laser scan, or the different irradiation points may be irradiated in each laser scan. When the different irradiation points are irradiated in each laser scan, the uniform thickness can be achieved in the melted metal layer to further improve the solder wetting property.

Although the YAG laser is used in the present embodiment, a CO2laser and an excimer laser can be used. However, the YAG laser has the irradiation energy enough to be able to remove outer casing resin10, and the YAG laser has good focusing properties to machine a detail portion. Therefore, the YAG laser is desirably used.

Hereinafter, a solid electrolytic capacitor having a cathode terminal provided with different recesses will be described below.FIG. 5Ais a sectional side view of another solid electrolytic capacitor according to the exemplary embodiment of the present invention,FIG. 5Bis a sectional front view thereof, andFIG. 5Cis a bottom view thereof.FIG. 5Ashows a sectional view taken along line5A-5A ofFIG. 5C, andFIG. 5Bshows a sectional view taken along line5B-5B ofFIG. 5C.

Cathode terminal30is made of the metal member which is made by machining a lead frame. Flat portion31is provided in a lower surface as mounting surface21, and flat portion31is arranged in a same plane with mounting surface21while exposed from outer casing resin10. Cathode terminal30has a T-shape in mounting surface21, and cathode terminal30is provided close onto the side of anode terminal8while going beyond the central portion of the lower surface from the end portion of mounting surface21.

Leading portions33are provided both end portions of the longitudinal rod portion in T-shaped cathode terminal30, and leading portions33have inclined wall surfaces32made of metal. Placement portions34are provided in the upper portions of leading portions33. Using press dies, leading portions33are bent obliquely upward at inclination angles θ2ranging from 5 to 45° with respect to flat portion31so as to be separated from the flat lower surface of the lead frame. Flat portion31and each of placement portions34are formed in the stepwise shape while having a step ranging from 0.1 to 0.15 mm.

In producing the solid electrolytic capacitor mentioned above, capacitor element1is connected to the lead frame, outer casing resin10is formed, and wall surfaces32are exposed by the laser irradiation likeFIG. 3. Then, recess36is formed. In recess36, the surroundings of the rectangular opening intersecting mounting surface21are closed. That is, one of the side faces of each recess36is formed by wall surface32, and the other side face is formed by wall surface35of the outer casing resin. Wall surface35is provided in the direction substantially perpendicular to mounting surface21.

In mounting the solid electrolytic capacitor of this structure, the melted solder is accommodated in recesses36, and the soldering layer on anode terminal8is substantially equal to that on cathode terminal30in thickness. That is, the same effect as the solid electrolytic capacitor shown inFIGS. 1A to 1Cis obtained.

Hereinafter, a solid electrolytic capacitor having a cathode terminal with a recess different from that of the solid electrolytic capacitor shown inFIGS. 5A to 5Cwill be described below.FIG. 6Ais a sectional side view of a still other solid electrolytic capacitor according to the exemplary embodiment of the present invention,FIG. 6Bis a sectional front view thereof, andFIG. 6Cis a bottom view thereof.FIG. 6Ashows a sectional view taken along line6A-6A ofFIG. 6C, andFIG. 6Bshows a sectional view taken along line6B-6B ofFIG. 6C.

Cathode terminal37is made of the metal member which is made by machining a lead frame. Flat portion38is provided in a lower surface as mounting surface21, and flat portion38is arranged in a same plane with mounting surface21while exposed from outer casing resin10. Cathode terminal37has a T-shape in mounting surface21, and cathode terminal37is provided close onto the side of anode terminal8while going beyond the central portion of the lower surface from the end portion of mounting surface21.

On the side of mounting surface21of cathode terminal37, recess39is provided in an edge of the short rod portion in T-shaped cathode terminal37, which intersects the C-axis and is located adjacent to anode terminal8. One side face of recess39is formed by wall surface40made of metal, and wall surface40is raised obliquely upward from flat portion38. The other side face is formed by wall surface41of outer casing resin10, and wall surface41is located adjacent to anode terminal8.

Using press dies, wall surface40is formed by curving the whole surface such that the flat lower surface of the lead frame is swelled toward the direction opposite mounting surface21. As shown inFIG. 6A, the cross section of wall surface40is formed in the arc in which an angle φ2ranges from 10° to 90°. Wall surface40is arranged in the direction substantially perpendicular to mounting surface21.

Leading portions42are obliquely provided in both end portions of cathode terminal37in a direction which is orthogonal to line6A to6A and not a thickness direction. Placement portions43are provided on the upper side of leading portions42while having steps respectively. After metal wall surface40is formed in the lead frame, using press dies, leading portions42are bent obliquely upward at inclination angles ranging from 30° to 60° so as to be separated from the flat lower surface of the lead frame.

After the lead frame is bent, likeFIG. 1A, capacitor element1is connected to the lead frame and outer casing resin10is formed. Finally, wall surface40is exposed by the laser irradiation, and recess39is formed while surrounded by wall surface40and wall surface41.

In mounting the solid electrolytic capacitor of this structure, the melted solder is accommodated in recess39, and the soldering layer on anode terminal8is substantially equal to that on cathode terminal37in thickness. That is, the same effect as the solid electrolytic capacitor shown inFIGS. 1A to 1Cis obtained.

In the above embodiment, recesses17,36, and39are provided in cathode terminals9,30, and37, respectively. That is, recesses17,36, and39are provided on the side of mounting surface21of cathode terminals9,30, and37, where the areas projected onto mounting surface21of cathode terminals9,30, and37are larger than that of anode terminal8. In addition, when the area projected onto mounting surface of the anode and cathode terminals is large, one of or both the anode and cathode terminals may be provided so as to have at least one recess having the large capacity. In the above embodiment, the anode and cathode terminals are formed by the lead frames. However, the invention is not limited thereto. For example, the anode and cathode terminals may be formed by metal pieces in which a metal rod is cut.

As described above, according to the exemplary embodiment of the present invention, can produce solid electrolytic capacitors having excellent high-frequency properties and improved mounting property. That is, the solid electrolytic capacitor according to the present invention and the manufacturing method thereof can be applied to surface-mount type solid electrolytic capacitors in which the low-ESR and low ESL properties are required.