Solid electrolytic capacitor and method for manufacturing same

Abstract

A solid electrolytic capacitor can be manufactured by a manufacturing method including a facing step and a welding step. A solid electrolytic capacitor includes an anode body, an anode lead, and an anode lead frame. The anode lead extends forward in a front-back direction from a front surface of the anode body. The anode lead frame has an upright portion. In the facing step, a predetermined region on the rear surface of the upright portion and the front end of the anode lead face each other. In the welding step, the upright portion and the leading end of the anode lead are welded to each other by radiating a laser beam toward a predetermined region of the upright portion from a radiation point located above and behind the upright portion in an up-down direction perpendicular to the front-back direction.

Description

Technical Field

[0001] The present invention relates to a solid electrolytic capacitor, which includes an anode body, an anode lead, and an anode lead frame. Background Art

[0002] This type of solid electrolytic capacitor is disclosed in JP 5078827 B (Patent Document 1), the content of which is incorporated herein by reference.

[0003] Patent Document 1 discloses a solid electrolytic capacitor, which includes an anode body, an anode wire (anode lead), and an anode terminal (anode lead frame). The anode body has a front end provided with an organic electrolyte layer. The organic electrolyte layer is covered with a light reflection layer. The anode lead frame is located in front of the light reflection layer. The anode lead projects forward through the light reflection layer. The anode lead is laser welded to the anode lead frame. According to Patent Document 1, the light reflection layer arranged as described above prevents damage to the organic electrolyte layer that may be caused by the reflection of the laser beam during the laser welding process, thereby being able to prevent the degradation of the solid electrolytic capacitor in terms of characteristics. Summary of the Invention

[0004] There is a need for a new technique that can laser weld the anode lead and the anode lead frame of a solid electrolytic capacitor to each other while preventing the degradation of the solid electrolytic capacitor in terms of characteristics.

[0005] Therefore, an object of the present invention is to provide a new manufacturing method for a solid electrolytic capacitor, in which the anode lead is laser welded to the anode lead frame, and the manufacturing method is suitable for manufacturing a solid electrolytic capacitor having superior characteristics. Another object of the present invention is to provide a solid electrolytic capacitor having an anode lead laser welded to the anode lead frame and having superior characteristics.

[0006] One aspect of the present invention provides a manufacturing method for a solid electrolytic capacitor, which includes an anode body, an anode lead, and an anode lead frame. The anode lead extends forward in the front-rear direction from the front surface of the anode body. The anode lead frame has an upright portion. The manufacturing method includes a facing step and a welding step. In the facing step, a predetermined area on the rear surface of the upright portion and the front end of the anode lead face each other. In the welding step, the upright portion and the front end of the anode lead are welded to each other by radiating a laser beam from a radiation point toward the predetermined area of the upright portion, and the radiation point is located above and behind the upright portion in the up-down direction perpendicular to the front-rear direction.

[0007] Another aspect of the present invention provides a solid electrolytic capacitor, which includes an anode body, an anode lead, and an anode lead frame. The anode lead extends forward in the front-rear direction from the front surface of the anode body. The anode lead frame has an upright portion. The anode lead has a front end, which is welded to a predetermined area on the rear surface of the upright portion. At least one of the front end of the anode lead and the predetermined area of the upright portion is formed with a laser track.

[0008] According to one aspect of the present invention, the front end of the anode lead faces the upright portion and is then welded to the rear surface of the upright portion. According to this manufacturing method, when the solid electrolytic capacitor manufactured in this way is coated with an external coating resin, the space occupied by the anode lead frame can be reduced, and the front surface of the anode body can be positioned close to the front surface of the external coating resin. Therefore, the volume efficiency of the anode body can be increased relative to the solid electrolytic capacitor including the external coating resin, and thus a solid electrolytic capacitor with superior characteristics can be obtained. In addition, when the upright portion and the front end of the anode lead are welded to each other, a laser beam is radiated from a radiation point located above and behind the upright portion. According to this radiation method, the anode lead and the upright portion can be firmly welded to each other with relatively small radiation energy, and the degradation of the characteristics of the solid electrolytic capacitor can be prevented.

[0009] In summary, one aspect of the present invention provides a new manufacturing method for a solid electrolytic capacitor, in which the anode lead is laser-welded to the anode lead frame, and this manufacturing method is applicable to manufacturing a solid electrolytic capacitor with superior characteristics. The solid electrolytic capacitor manufactured by the above manufacturing method has superior characteristics. Therefore, one aspect of the present invention provides a solid electrolytic capacitor, which has an anode lead laser-welded to the anode lead frame and has superior characteristics.

[0010] The object of the present invention can be understood and the structure of the present invention can be more comprehensively understood by studying the following description of the preferred embodiments and referring to the drawings. Description of the Drawings

[0011] Figure 1 is a perspective view showing a solid electrolytic capacitor according to an embodiment of the present invention, in which the outlines of the internal components covered by the external coating resin and hidden behind the external coating resin are shown in dotted lines.

[0012] Figure 2 is Figure 1 a perspective view of the solid electrolytic capacitor, in which the outline of the external coating resin and the hidden outline of the anode lead are shown in dotted lines, and the radiation point of the laser beam radiation is shown as a white circle.

[0013] Figure 3 is a view showing Figure 2Stereoscopic view of the anode lead frame of a solid electrolytic capacitor, wherein the contour of the predetermined area irradiated by the laser beam, the contour of the focus in the predetermined area, and the position of the front edge of the base of the anode lead frame are indicated by dashed lines.

[0014] Figure 4 shows Figure 1 Flow chart of the manufacturing steps of a solid electrolytic capacitor.

[0015] Figure 5 shows Figure 2 Top view of the anode lead frame and the cathode lead frame of a solid electrolytic capacitor, wherein the contour of the body of the solid electrolytic capacitor is indicated by a dashed line, and the illustrated body, anode lead frame, and cathode lead frame are in the preparation step.

[0016] Figure 6 shows Figure 5 Top view of the body, anode lead frame, and cathode lead frame of a solid electrolytic capacitor, wherein the illustrated body, anode lead frame, and cathode lead frame are in the facing step, and the contour of the external coating resin of the solid electrolytic capacitor is indicated by a dashed line.

[0017] Figure 7 shows Figure 6 Side view of the body, anode lead frame, and cathode lead frame of a solid electrolytic capacitor, wherein the contour of the external coating resin is indicated by a dashed line.

[0018] Figure 8 shows Figure 7 Side view of a part of a solid electrolytic capacitor, wherein the hidden part of the anode lead frame and the front surface of the external coating resin are indicated by dashed lines.

[0019] Figure 9 shows Figure 8 Side view of a modified version of a solid electrolytic capacitor, wherein the hidden part of the anode lead frame and the virtual line extending forward from the lower end of the upright part of the anode lead frame are indicated by dashed lines.

[0020] Figure 10 Schematically shows Figure 2 Side view of the laser track formed on a solid electrolytic capacitor, wherein the contour of the hidden recess before laser welding and the contour of the front end of the anode lead are indicated by dashed lines.

[0021] Figure 11 Schematically shows Figure 10 Rear view of the laser track, wherein the contour of the anode lead is indicated by a dashed line.

[0022] Figure 12 Schematically shows Figure 10 Front view of the laser track.

[0023] While the present invention may be susceptible to various modifications and alternative forms, specific embodiments of the invention are shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the drawings and the detailed description thereof are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. Detailed Description of the Invention

[0024] Referring to Figure 1 and Figure 2 , a solid electrolytic capacitor 10 according to an embodiment of the present invention includes a body 12 having capacitance, an external coating resin 18 made of an insulator, an anode lead frame 40 made of a conductor, and a cathode lead frame 60 made of a conductor. The solid electrolytic capacitor 10 of this embodiment has the above components. However, the present invention is not limited thereto. For example, the solid electrolytic capacitor 10 may include other components in addition to the above components.

[0025] The solid electrolytic capacitor 10 of this embodiment has a rectangular flat plate shape parallel to the horizontal plane (XY plane). In particular, the solid electrolytic capacitor 10 of this embodiment has a small size of about 0.6 mm in the up-down direction perpendicular to the horizontal plane. In other words, the solid electrolytic capacitor 10 has a small thickness. More specifically, the thickness of the solid electrolytic capacitor 10 is less than half of the short side length of the solid electrolytic capacitor 10 in the horizontal plane. However, the present invention is not limited to the thin and compact solid electrolytic capacitor 10, but can be applied to various solid electrolytic capacitors having various shapes and sizes.

[0026] The up-down direction of this embodiment is the Z direction. In this embodiment, "upward" represents the positive Z direction, and "downward" represents the negative Z direction. Position-related terms such as the horizontal plane and the up-down direction do not represent the absolute positional relationship with respect to the ground, but only represent the relative positional relationship in the drawings. For example, in this embodiment, the solid electrolytic capacitor 10 is configured to be mounted on the main surface of a circuit board (not shown), and the plane along which the main surface extends is defined as the horizontal plane.

[0027] The main body 12 of the present embodiment has a rectangular flat plate shape that is substantially parallel to the horizontal plane (XY plane). The anode lead frame 40 and the cathode lead frame 60 are fixed to the main body 12. The main body 12 is entirely located above the anode lead frame 40 and the cathode lead frame 60. The external coating resin 18 is formed by resin molding such that the main body 12, the anode lead frame 40, and the cathode lead frame 60 are buried in the external coating resin 18. In other words, the main body 12, the anode lead frame 40, and the cathode lead frame 60 are embedded in the external coating resin 18. However, each of the anode lead frame 40 and the cathode lead frame 60 is partially exposed outward from the external coating resin 18.

[0028] Referring to Figure 2 , the exposed portion of the anode lead frame 40 that is exposed from the external coating resin 18 serves as the anode terminal 41, and the exposed portion of the cathode lead frame 60 that is exposed from the external coating resin 18 serves as the cathode terminal 61. For example, when the solid electrolytic capacitor 10 is used, the anode terminal 41 and the cathode terminal 61 are respectively soldered to the conductive patterns (not shown) formed on the upper surface of the circuit board (not shown).

[0029] The main body 12 includes an anode body 20, a cathode layer 50, and an anode lead 30 made of a metal such as tantalum. Thus, the solid electrolytic capacitor 10 includes the anode body 20, the anode lead 30, and the cathode layer 50. The anode body 20 of the present embodiment includes multiple layers, which include an anode (not shown) made of a valve metal such as tantalum and a dielectric layer (not shown) covering the anode. The cathode layer 50 of the present embodiment includes multiple layers, which include a solid electrolyte layer (not shown) covering the dielectric layer and a surface layer made of a conductor such as silver paste. The anode body 20, the anode lead 30, and the cathode layer 50 are located in the external coating resin 18. The anode body 20, the anode lead 30, and the cathode layer 50 are completely embedded in the external coating resin 18.

[0030] The cathode layer 50 completely covers the anode body 20 except for the front surface 22 of the anode body 20 in the front - rear direction perpendicular to the up - down direction. The front - rear direction of the present embodiment is the X direction. In the present embodiment, "forward" is the positive X direction, and "backward" is the negative X direction.

[0031] The anode lead 30 of the present embodiment has a cylindrical shape extending in the front - rear direction. The anode lead 30 has a rear portion embedded in the anode body 20 and a front portion protruding forward from the front surface 22 of the anode body 20, and the thus - formed anode lead 30 extends forward in the front - rear direction from the front surface 22 of the anode body 20.

[0032] The anode lead 30 has a front end 32, which is a cut surface cut during the manufacturing process of the anode lead 30. As described later, the front end 32 is welded to the anode lead frame 40. The front end 32 is a planar surface parallel to the vertical plane (YZ plane) perpendicular to the front-rear direction before welding, and has a small circular shape. The front end 32 has a diameter smaller than the dimension of the main body 12 in the up-down direction. For example, the dimension of the main body 12 in the up-down direction is about 0.3 mm, and the diameter of the front end 32 is about 0.15 mm.

[0033] The main body 12 of the present embodiment has the above structure and can be manufactured by an existing manufacturing method such as that disclosed in Patent Document 1 (JP 5078827 B). However, the structure and manufacturing method of the main body 12 of the present invention are not specifically limited as long as the solid electrolytic capacitor 10 is provided with the anode body 20 that holds the anode lead 30. For example, the anode lead 30 may have a polygonal columnar shape extending in the front-rear direction. The front end 32 of the anode lead 30 may be a planar surface inclined to the front-rear direction before welding.

[0034] Refer to Figure 5 and in combination with Figure 2 and Figure 3 In this embodiment, each of the anode lead frame 40 and the cathode lead frame 60 is formed by bending a single metal sheet having a predetermined shape cut from a metal plate. Therefore, each of the anode lead frame 40 and the cathode lead frame 60 is a single bent metal plate.

[0035] Each of the anode lead frame 40 and the cathode lead frame 60 in this embodiment is made of a metal such as iron or copper, which can be processed relatively easily. Therefore, each of the anode lead frame 40 and the cathode lead frame 60 has a melting point much lower than that of the anode lead 30 made of tantalum. However, the material, structure, and manufacturing method of each of the anode lead frame 40 and the cathode lead frame 60 of the present invention are not specifically limited. In addition, the cathode lead frame 60 can be provided as needed.

[0036] Next, the anode lead frame 40 of this embodiment will be described in more detail.

[0037] Refer to Figure 3 and Figure 2 In this embodiment, the anode lead frame 40 has a base portion 42 and an upright portion 44. The size of the base portion 42 is slightly smaller than the size of the main body 12 in the lateral direction perpendicular to the up-down direction and the front-rear direction. The size of the upright portion 44 is larger than the diameter of the front end 32 of the anode lead 30 in the lateral direction. The lateral direction of this embodiment is the Y direction. The anode lead frame 40 only has the aforementioned parts. However, the present invention is not limited thereto. For example, the anode lead frame 40 may have other parts in addition to the above parts.

[0038] Reference Figure 3 As shown in Figure 3 , the base 42 of the present embodiment extends along a horizontal plane (XY plane). The base 42 has a main portion 422 and two legs 424. The main portion 422 has a rectangular flat plate shape parallel to the horizontal plane. The main portion 422 has a leading edge extending in the lateral direction. The two legs 424 are respectively connected to opposite sides in the lateral direction of the leading edge of the main portion 422. Each of the legs 424 extends forward from the leading edge of the main portion 422.

[0039] The base 42 of the anode lead frame 40 of the present embodiment has the above structure. However, the present invention is not limited thereto, and the structure of the base 42 can be modified as needed. In addition, the base 42 can be provided as needed.

[0040] The upright portion 44 of the present embodiment extends entirely along a vertical plane (YZ plane). Specifically, the upright portion 44 is connected to the middle portion in the lateral direction of the leading edge of the main portion 422. The upright portion 44 extends forward from the leading edge of the main portion 422. Then, the upright portion 44 is curved in an arc and extends upward. The upright portion 44 has a front surface 442 and a rear surface 444. Each of the front surface 442 and the rear surface 444 of the present embodiment is a flat surface without depressions or protrusions.

[0041] The upright portion 44 of the anode lead frame 40 of the present embodiment has the above structure. However, the present invention is not limited thereto, and the structure of the upright portion 44 can be modified as needed. For example, each of the front surface 442 and the rear surface 444 can be a curved surface.

[0042] Next, a method for manufacturing the solid electrolytic capacitor 10 of the present embodiment (see Figure 1 and Figure 2 ) will be described.

[0043] Reference Figure 1 and Figure 2 It is generally difficult to improve the volume efficiency of the anode body of a thin and compact solid electrolytic capacitor (such as the anode body of the solid electrolytic capacitor 10 of the present embodiment), where the volume efficiency is the ratio of the volume occupied by the anode body to the total volume of the solid electrolytic capacitor including the external coating resin. However, as described later, according to the manufacturing method of the present embodiment, even if the solid electrolytic capacitor 10 is thin and compact, the volume efficiency of the anode body 20 can be increased, thereby enabling the solid electrolytic capacitor 10 to be improved in terms of characteristics.

[0044] Reference Figure 4 and Figure 1 and Figure 2, the solid electrolytic capacitor 10 of this embodiment is manufactured through four steps, which include: a preparation step (S10), a facing step (S20), a soldering step (S30), and a coating step (S40). However, the manufacturing method described below is only an example, and the manufacturing method of the solid electrolytic capacitor 10 can be variously modified. For example, multiple solid electrolytic capacitors 10 can be manufactured simultaneously.

[0045] First, in the preparation step (S10), each of the three components of the solid electrolytic capacitor 10, namely the body 12, the anode lead frame 40, and the cathode lead frame 60, is formed and prepared. The body 12 thus prepared has Figure 2 the shape shown. As Figure 5 shown, each of the anode lead frame 40 and the cathode lead frame 60 prepared as described above is a single metal plate having a predetermined shape. For example, each of the base 42 and the upright portion 44 of the anode lead frame 40 extends along a horizontal plane (XY plane). Similarly, the entire cathode lead frame 60 extends along a horizontal plane.

[0046] Referring to Figure 4 and Figures 5 to 7 , in the subsequent facing step (S20), the upright portion 44 of the anode lead frame 40 is bent upward so that the upright portion 44 extends along a vertical plane (YZ plane). Similarly, the rear portion of the cathode lead frame 60 is bent upward so that the rear portion extends along a vertical plane. Then, the body 12 is disposed on the base 42 of the anode lead frame 40 and the portion of the cathode lead frame 60 that extends along the horizontal plane (XY plane). At the same time, the front portion of the body 12 is disposed on the base 42 through an insulating member (not shown). In addition, the rear portion of the body 12 is fixed to the cathode lead frame 60 by a conductive adhesive 70. Therefore, the cathode layer 50 of the body 12 is electrically connected to the cathode lead frame 60 through the conductive adhesive 70.

[0047] Referring to Figure 6 and Figure 7 , as a result of the facing step (see Figure 4 ), the rear surface 444 of the upright portion 44 faces the front end 32 of the anode lead 30. The rear surface 444 of the illustrated upright portion 44 contacts the front end 32 of the anode lead 30. However, the present invention is not limited thereto. For example, a small gap may be formed between the rear surface 444 of the upright portion 44 and the front end 32 of the anode lead 30. Alternatively, the front end 32 of the anode lead 30 may abut against the rear surface 444 of the upright portion 44 and may push the rear surface 444 forward.

[0048] The rear surface 444 of the upright portion 44 has a predetermined area 447 (see Figure 3). The predetermined region 447 is a part of the rear surface 444 and faces the front end 32 of the anode lead 30. There is no distance or a distance is formed between the predetermined region 447 and the front end 32 of the anode lead 30. As described later, the predetermined region 447 is configured to be laser welded to the front end 32 of the anode lead 30. Therefore, the manufacturing method of the solid electrolytic capacitor 10 of the present embodiment includes a facing step (see Figure 4 ), or making the predetermined region 447 on the rear surface 444 of the upright portion 44 and the front end 32 of the anode lead 30 face each other, with no distance or a distance formed between the predetermined region 447 and the front end 32 of the anode lead 30. The predetermined region 447 of the present embodiment has a circular shape corresponding to the front end 32 of the anode lead 30.

[0049] Refer to Figure 5 , according to the present embodiment, two U-shaped grooves 46 are respectively formed on opposite sides of the upright portion 44 in the lateral direction. Each of the grooves 46 is located between the upright portion 44 and the leg 424 in the lateral direction. According to this structure, the upright portion 44 can be easily bent so that the upright portion 44 extends along a vertical plane (YZ plane). However, the present invention is not limited thereto. For example, the anode lead frame 40 may not be provided with the leg 424. In other words, the entire leading edge of the base 42 may be connected to the upright portion 44.

[0050] Refer to Figure 4 and Figure 2 and Figure 3 , in the subsequent welding step (S30), the front end 32 of the anode lead 30 is laser welded to the rear surface 444 of the upright portion 44. Refer to Figure 2 and Figure 3 , in the laser welding of the present embodiment, a laser beam LL is radiated from a predetermined radiation point RP toward the predetermined region 447 of the rear surface 444. Specifically, the laser beam LL is radiated toward the center of the predetermined region 447 through the upper end of the front end 32 of the anode lead 30. When the laser beam LL is radiated as described above, the front end 32 of the anode lead 30 and the rear surface 444 of the upright portion 44 are partially melted and welded to each other. Therefore, the anode terminal 41 of the anode lead frame 40 is electrically connected to the anode body 20 through the anode lead 30.

[0051] The radiation point RP of the present embodiment is located above and behind the upright portion 44. Therefore, the manufacturing method of the solid electrolytic capacitor 10 of the present embodiment includes a welding step (see Figure 4 ), or welding the upright portion 44 and the front end 32 of the anode lead 30 to each other by radiating a laser beam LL from the radiation point RP toward the predetermined region 447 of the upright portion 44, and the radiation point is located above and behind the upright portion 44.

[0052] Refer toFigure 4 and Figure 1 and Figure 2 In the subsequent coating step (S40), the outer coating resin 18 is resin-molded. Specifically, the main body 12 fixed to the anode lead frame 40 and the cathode lead frame 60 is arranged in a mold (not shown). Then, a sol-like thermosetting resin is poured into the mold. Then, the thermosetting resin is heated and hardened. Thus, except for the anode terminal 41 and the cathode terminal 61, the main body 12, the anode lead frame 40, and the cathode lead frame 60 are completely covered with the outer coating resin 18. At this time, the solid electrolytic capacitor 10 has been fabricated.

[0053] Referring to Figure 2 and Figure 8 According to the present embodiment, the front end 32 of the anode lead 30 faces the rear surface 444 of the upright portion 44 and is then welded to the rear surface 444 as described above. According to this manufacturing method, when the solid electrolytic capacitor 10 manufactured in this way is coated with the outer coating resin 18, the space occupied by the anode lead frame 40 can be reduced, and the front surface 22 of the anode body 20 can be positioned close to the front surface 182 of the outer coating resin 18. Therefore, the space between the front surface 22 of the anode body 20 and the front surface 182 of the outer coating resin 18 can be reduced. Therefore, the volume efficiency of the anode body 20 can be increased, and thus a solid electrolytic capacitor 10 having superior characteristics can be obtained.

[0054] As described below, the above laser welding is preferable for a thin and compact solid electrolytic capacitor 10. Generally, the laser beam LL may scatter during laser welding, and the anode body 20 may be damaged by such scattered laser beam LL. However, according to the present embodiment, when the upright portion 44 and the front end 32 of the anode lead 30 are welded to each other, the laser beam LL is radiated from a radiation point RP located above and behind the upright portion 44. In other words, the laser beam LL is radiated to the upright portion 44 from one side in the front-rear direction where the main body 12 is located. According to this radiation mode, damage to the main body 12 can be reliably prevented. In addition, by making the radiation angle of the laser beam LL or the angle of the laser beam LL with respect to the front-rear direction close to 90°, the space between the front surface 22 of the anode body 20 and the front surface 182 of the outer coating resin 18 can be further reduced.

[0055] In addition, according to the present embodiment, the anode body 20 can be electrically connected to the anode lead frame 40 by welding only the small front end 32 of a single anode lead 30 to the upright portion 44. Specifically, it is sufficient for the laser beam LL to melt only the upper end of the front end 32 and the portion of the anode lead frame 40 having a low melting point. Therefore, according to the present embodiment, the anode lead 30 and the upright portion 44 can be firmly welded to each other with relatively small radiation energy, and the anode body 20 can be electrically connected to the anode lead frame 40, while preventing the degradation of the characteristics of the solid electrolytic capacitor 10 that may be caused by the radiation of the laser beam LL.

[0056] In summary, the present embodiment provides a new manufacturing method of a solid electrolytic capacitor 10, in which the anode lead 30 is laser welded to the anode lead frame 40, and this manufacturing method is suitable for manufacturing a solid electrolytic capacitor 10 having superior characteristics. Compared with the volume efficiency of existing solid electrolytic capacitors, the solid electrolytic capacitor 10 manufactured by the above manufacturing method has a greater volume efficiency. Therefore, the present embodiment provides a solid electrolytic capacitor 10 having an anode lead 30 laser welded to the anode lead frame 40 and having superior characteristics.

[0057] Although the solid electrolytic capacitor 10 is thin and compact, the present embodiment provides a solid electrolytic capacitor 10 having a large volume efficiency and a manufacturing method suitable for the solid electrolytic capacitor 10. For example, the size (length) of the solid electrolytic capacitor 10 of the present embodiment in the front-rear direction is about 3.5 mm, and the distance D1 between the front surface 182 of the outer coating resin 18 and the front surface 22 of the anode body 20 is 0.3 mm or more but 0.5 mm or less. According to the present embodiment, the distance D1 can be set to 15% or less of the length of the solid electrolytic capacitor 10, so that the volume efficiency of the anode body 20 can be increased.

[0058] Hereinafter, the manufacturing method of the present embodiment will be described in more detail.

[0059] From the perspective of improving the volume efficiency of the anode body 20, the distance D1 between the front surface 182 of the outer coating resin 18 and the front surface 22 of the anode body 20 is preferably as small as possible. However, when the distance D1 becomes small, the distance D2 between the front surface 22 of the anode body 20 and the rear surface 444 of the upright portion 44 also becomes small. Generally, when the distance D2 is too small, laser welding may be difficult, and the anode body 20 may be damaged by laser welding.

[0060] For example, in the case of YAG laser welding, which is a typical laser welding, when the radiation energy of the laser beam LL is large, the anode body 20 may be damaged. More specifically, the upright portion 44 may be evaporated in large quantities, and the evaporated gas may adhere to the front surface 22 of the anode body 20, causing the anode body 20 to deteriorate. On the other hand, when the radiation energy of the laser beam LL is small, firm welding may not be possible. More specifically, when the radiation energy of the laser beam LL is small, a so-called open circuit failure may occur.

[0061] In contrast, the laser beam LL of the present embodiment can be generated by a pulsed fiber laser. The pulsed fiber laser can easily generate a laser beam LL with a small spot diameter. According to the decrease in the spot diameter, it is possible to easily increase the density of the radiation energy while decreasing the radiation energy.

[0062] Specifically, referring to Figure 3 and Figure 2 , the laser beam LL of the present embodiment is focused on the focal point 448 located at the center of the predetermined area 447. The focal point 448 of the laser beam LL formed on the predetermined area 447 has a short diameter of 0.01 mm or more but 0.05 mm or less. In other words, the spot diameter of the laser beam LL of the present embodiment is 0.01 mm to 0.05 mm (including 0.01 mm and 0.05 mm). The laser beam LL of the present embodiment has a small spot diameter as described above. Therefore, the laser beam LL of the present embodiment generally has a small amount of radiation energy.

[0063] By generating the laser beam LL with the pulsed fiber laser as described above, the radiation energy can be easily controlled. However, the method for generating the laser beam LL of the present invention is not particularly limited.

[0064] According to the present embodiment, the front end 32 of the anode lead 30 and the rear surface 444 of the upright portion 44 can be firmly welded to each other with relatively small radiation energy, and at the same time, the operator can observe the front end 32 of the anode lead 30. Therefore, it is possible to prevent the anode body 20 from being damaged without providing an additional layer such as a light reflection layer on the front surface 22 of the anode body 20. Therefore, according to the present embodiment, the manufacturing cost of the solid electrolytic capacitor 10 can be reduced.

[0065] Referring to Figure 8 , the anode lead 30 of the present embodiment has a lower end 38 that extends linearly in the front-rear direction. The front end 32 of the anode lead 30 is a planar surface parallel to the vertical plane (YZ plane). In the facing step (see Figure 4 ), the front end 32 faces the rear surface 444 of the upright portion 44 and is in surface contact with the rear surface 444 of the upright portion 44, which is a flat surface parallel to the vertical plane.

[0066] According to the above arrangement, firm welding can be achieved with relatively small radiant energy. Specifically, a laser beam LL with relatively small radiant energy enables the front end 32 and the rear surface 444 to be firmly welded to each other, while reducing the melting of the anode lead 30 and the evaporation of the upright portion 44. However, the present invention is not limited thereto. For example, the arrangement of the anode lead 30 and the upright portion 44 can be variously modified as described below.

[0067] Referring to Figure 9 , a gap GP can be formed between the rear surface 444 of the upright portion 44 and the front end 32 of the anode lead 30 in the facing step (see Figure 4 ). When the gap GP is formed, the gap GP is preferably widened upward. From the perspective of preventing open circuit failures and increasing the radiation angle of the laser beam LL, the angle θ1 formed by the rear surface 444 of the upright portion 44 and the front end 32 of the anode lead 30 is preferably as small as possible. More specifically, the angle θ1 is preferably 13° or less.

[0068] In summary, when a gap GP is formed between the rear surface 444 of the upright portion 44 and the front end 32 of the anode lead 30 in the facing situation (referring to Figure 4 ), the gap GP is preferably widened upward, and the rear surface 444 of the upright portion 44 and the front end 32 of the anode lead 30 preferably form an angle θ1 of 13° or less.

[0069] The front end 32 of the anode lead 30 can be inclined with respect to the lower end 38 of the anode lead 30. However, when the angle θ2 formed by the front end 32 of the anode lead 30 and the lower end 38 of the anode lead 30 is too small, it is difficult for a laser beam LL with a large radiation angle (see Figure 2 ) to radiate through the upper end of the front end 32 of the anode lead 30, making it difficult to weld the front end 32 and the rear surface 444 of the upright portion 44 to each other. Therefore, the angle θ2 is preferably close to 90°. More specifically, the angle θ2 is preferably 80° or greater. However, when the angle θ2 is greater than 90°, the gap GP widens downward. According to this structure, during the laser welding process, the lower part of the upright portion 44 may evaporate, and the evaporated gas may adhere to the front surface 22 of the anode body 20, causing the anode body 20 to deteriorate. Therefore, the angle θ2 is preferably 90° or less.

[0070] In summary, the front end 32 of the anode lead 30 and the lower end 38 of the anode lead 30 preferably form an angle θ2 of 80° or greater in the facing situation (see Figure 4 ). In addition, the front end 32 of the anode lead 30 and the lower end 38 of the anode lead 30 preferably form an angle θ2 of 90° or less in the facing situation (see Figure 4 ).

[0071] In the facing step (seeFigure 4 ), if the upright portion 44 bends backward too much, during the process of arranging the main body 12 on the anode lead frame 40, the front end 32 of the anode lead 30 may come into contact with the upright portion 44. Therefore, the upright portion 44 preferably extends substantially parallel to the vertical plane (YZ plane). More specifically, the rear surface 444 of the upright portion 44 and the virtual line IL extending forward from the lower end 48 of the upright portion 44 preferably form an angle θ3 of 93° or less when facing each other.

[0072] Next, the solid electrolytic capacitor 10 of the present embodiment (see Figure 1 ) will be described.

[0073] As Figure 6 shown, the size of the upright portion 44 of the present embodiment is larger than the size of the front end 32 of the anode lead 30 in the lateral direction. As Figure 3 shown, two notches 446 are formed in the upright portion 44. The two notches 446 are respectively formed at opposite ends of the upright portion 44 in the lateral direction. Each of the notches 446 is recessed inward in the lateral direction of the upright portion 44.

[0074] Referring to Figure 2 , according to the aforementioned manufacturing method, the anode lead 30 and the upright portion 44 are fixed to each other only at the welding portion near the front end 32 of the anode lead 30. For example, assuming that no notches 446 are formed, when an upward force is applied to the solid electrolytic capacitor 10 mounted on a circuit board (not shown), the upright portion 44 fixed to the circuit board and the anode lead 30 fixed to the upright portion 44 can be subjected to an upward force. Therefore, the applied force may be concentrated on the welding portion between the anode lead 30 and the upright portion 44, which may cause an open circuit failure.

[0075] However, according to the present embodiment, the notches 446 are formed, and resin is filled in each of the notches 446. According to this structure, the force applied to the solid electrolytic capacitor 10 can be dispersed, and the upward force applied to the anode lead 30 can be reduced. Therefore, the force applied to the welding portion between the anode lead 30 and the upright portion 44 can be reduced. In addition, each of the notches 446 serves as an anchor for fixing the anode lead frame 40 in the external coating resin 18, so that the main body 12, the anode lead frame 40, and the cathode lead frame 60 can be firmly fixed in the external coating resin 18. In particular, since the two notches 446 are respectively provided at opposite ends of the upright portion 44 in the lateral direction, a stable anchoring effect can be obtained.

[0076] The notch 446 of this embodiment is formed and functions as described above. However, the present invention is not limited thereto. For example, the shape of each of the notches 446 is not particularly limited. The two notches 446 may be located at positions different from each other in the up-down direction. The notch 446 can be provided as needed. For example, the notch 446 may not be provided, and the size of the upright portion 44 in the lateral direction may be increased upward. According to this structure, an effect similar to the case where the notch 446 is provided can be obtained.

[0077] Referring to Figure 10 and Figure 11 , the solid electrolytic capacitor 10 of this embodiment is manufactured as described above. Therefore, the front end 32 of the anode lead 30 is welded to a predetermined area 447 on the rear surface 444 of the upright portion 44. In the facing step (see Figure 4 ), the gap GP (see Figure 9 ) located between the front end 32 and the rear surface 444 is at least partially filled with the melted anode lead 30. In addition, at least one of the front end 32 of the anode lead 30 and the predetermined area 447 of the upright portion 44 is formed with a laser trace LM.

[0078] The laser trace LM is a depression formed due to laser welding. In other words, the laser trace LM is a cut portion of the anode lead 30 formed due to laser welding. A part of the illustrated laser trace LM is located at the upper end of the front end 32 of the anode lead 30 and is recessed downward. Another part of the laser trace LM is located at the upper end of the predetermined area 447 and is slightly recessed forward. The portion formed by the laser trace LM is made of an alloy of tantalum and iron and is discolored.

[0079] The illustrated laser trace LM is formed as described above. However, the illustrated laser trace LM is only a schematically shown example, and the actual laser trace LM is located at various positions and has various shapes and sizes. As described above, the solid electrolytic capacitor 10 has a structure in which at least one of the front end 32 and the predetermined area 447 is formed with a laser trace LM (i.e., a depression formed due to laser welding). This structure means that the solid electrolytic capacitor 10 is manufactured by the above manufacturing method.

[0080] Referring to Figure 10 and Figure 12 , a recess 449 is formed on the front surface 442 of the illustrated upright portion 44. The recess 449 is a trace formed by a laser beam LL that passes through the upright portion 44 forward and downward. Therefore, the recess 449 is a kind of laser trace. Referring to Figure 12 and Figure 11 , the recess 449 is located at a position corresponding to the predetermined area 447 in the vertical plane (YZ plane) and is recessed backward from the front surface 442. Referring to Figure 2, the recess 449 formed as described above serves as an anchor, similar to the notch 446 that fixes the anode lead frame 40 in the outer coating resin 18. In addition, the recess 449 formed on the front surface 442 of the upright portion 44 indicates that the solid electrolytic capacitor 10 is manufactured by the above manufacturing method.

[0081] Referring to Figure 12 , the recess 449 of this embodiment has an elliptical shape. The recess 449 has a width (first dimension) WT in the lateral direction and a height (second dimension) HT in the up-down direction. The second dimension HT is greater than the first dimension WT. More specifically, the second dimension HT is equal to or greater than twice the first dimension WT. However, the present invention is not limited thereto. The shape, size, and arrangement of the recess 449 can be variously changed according to the radiation direction and radiation energy of the laser beam LL (see Figure 10 ). In addition, sometimes the recess 449 is not formed.

[0082] Referring to Figure 2 , if the anode lead 30 is laser welded to a large area of the anode lead frame 40 by radiating a large amount of energy, most of the upright portion 44 of the anode lead frame 40 may be melted. In contrast, the laser welding of this embodiment is performed by the laser beam LL having a small amount of radiation energy. Therefore, the upright portion 44 is only slightly melted, and the shape of the upright portion 44 before laser welding is maintained. Therefore, the shape of the upright portion 44 can be designed relatively flexibly without considering the influence caused by laser welding. For example, as described above, the upright portion 44 can be formed with two notches 446.

[0083] Referring to Figures 10 to 12 , as described above, at least one of the front end 32 of the anode lead 30 and the predetermined area 447 of the upright portion 44 is formed with a laser track LM, which means that the front end 32 of the anode lead 30 is welded to the predetermined area 447 of the upright portion 44 by the manufacturing method of this embodiment. However, the present invention is not limited thereto. As long as the anode lead 30 extending forward from the front surface 22 of the anode body 20 is welded to the upright portion 44 of the anode lead frame 40, the volume efficiency of the solid electrolytic capacitor 10 can be made greater than that of the existing solid electrolytic capacitor. Therefore, the solid electrolytic capacitor 10 can be manufactured by another manufacturing method different from the manufacturing method of this embodiment.

[0084] Next, the conductive adhesive 70 of this embodiment will be described (see Figure 7 ).

[0085] Referring to Figure 7 , in the facing step (see Figure 4),(the cathode layer 50 at the rear of the main body 12 is fixed to the cathode lead frame 60 by a conductive adhesive 70. Specifically, first, the conductive adhesive 70 is applied to the cathode lead frame 60. Then, the cathode layer 50 is placed on the conductive adhesive 70. Then, during the manufacturing process, the solid electrolytic capacitor 10 is heated at a temperature much lower than the soldering temperature, so that the conductive adhesive 70 hardens. Thus, the cathode layer 50 and the cathode lead frame 60 are fixed to each other and electrically connected to each other. According to this embodiment, the cathode layer 50 can be electrically connected to the cathode lead frame 60 while preventing the degradation of the characteristics of the solid electrolytic capacitor 10 that may be caused by heat treatment.)

[0086] The conductive adhesive 70 of this embodiment is not particularly limited. For example, the conductive adhesive 70 can be a commonly used silver paste, or can be a conductive metal paste (metallization paste) different from the silver paste.)

[0087] The silver paste is an adhesive containing a main component and silver particles. The main component contains a thermosetting resin and a solvent. The silver particles are distributed in the main component. When the silver paste is heated, the solvent volatilizes, causing the main component to shrink, so that the silver particles come into contact with each other. Therefore, the silver paste after heat curing has conductivity. However, when the main component shrinks, the entire conductive adhesive 70 shrinks. Therefore, the conductive adhesive 70 may fall off from the cathode layer 50 or the cathode lead frame 60. For example, the cathode lead frame 60 should be formed with an anchor structure, such as a structure including recesses and protrusions, so that the cathode layer 50 and the cathode lead frame 60 are firmly connected to each other by the silver paste. Such an anchor structure may increase the size of the solid electrolytic capacitor 10.)

[0088] The conductive metal paste is an adhesive containing a main component and various metal particles including low melting point metal particles. The main component contains a thermosetting resin but basically does not contain a solvent. The metal particles are distributed in the main component. When the conductive metal paste is heated, the low melting point metal particles melt and connect the metal particles to each other. Therefore, the conductive metal paste after heat curing has conductivity. Therefore, the conductive metal paste is a metallization paste. In addition, when the conductive metal paste is heated, the conductive metal paste basically does not shrink. Therefore, the cathode layer 50 and the cathode lead frame 60 can be firmly connected to each other without forming an anchor structure on the cathode lead frame 60. Therefore, the solid electrolytic capacitor 10 can be easily made thin and compact. In addition, according to the connection by the conductive metal paste, compared with the connection by the silver paste, the change in the bonding strength between the cathode layer 50 and the cathode lead frame 60 can be reduced. Therefore, the cathode layer 50 and the cathode lead frame 60 can be stably electrically connected to each other by the conductive metal paste.)

[0089] According to this embodiment, the base 42 of the anode lead frame 40 is located directly below the cathode layer 50 at the front portion of the main body 12. The base 42 and the cathode layer 50 should be spaced apart from each other by a relatively large distance in the up-down direction so that the base 42 and the cathode layer 50 are reliably insulated from each other. Such an arrangement inevitably results in the size (height) of the gap formed between the cathode lead frame 60 and the cathode layer 50 in the up-down direction. A conductive metal paste is suitable for filling such a relatively large gap. However, in the case where the height of the gap can be made smaller, a silver paste can be used.

[0090] Although the preferred embodiments of the invention have been described, those skilled in the art will recognize that other modifications and further modifications can be made to the preferred embodiments of the invention without departing from the spirit of the invention, and it is intended to claim all such embodiments that fall within the true scope of the invention.

Claims

1. A method for manufacturing a solid electrolytic capacitor, the solid electrolytic capacitor comprising an anode body, an anode lead and an anode lead frame, the anode lead extending forward from a front surface of the anode body in a front-to-rear direction, the anode lead frame having an upright portion, the manufacturing method comprising: causing a predetermined area on a rear surface of the upright portion and a front end of the anode lead to face each other; and The upright portion and the front end of the anode lead are welded to each other by irradiating a laser beam toward a predetermined area of ​​the upright portion from a irradiation point located above the upright portion in an up-down direction perpendicular to the front-rear direction and behind the upright portion.

2. The manufacturing method according to claim 1, wherein: When a gap is formed between the rear surface of the upright portion and the front end of the anode lead in the facing state, the gap is widened upward and the rear surface of the upright portion and the front end of the anode lead form an angle of 13° or less.

3. The manufacturing method according to claim 2, wherein: The front end of the anode lead and the lower end of the anode lead are faced with each other so as to form an angle of 80° or more.

4. The manufacturing method according to claim 1, wherein: The rear surface of the upright portion is made to form an angle of 93° or less with a virtual line extending forward from a lower end of the upright portion in a facing state.

5. The manufacturing method according to claim 1, wherein: The front end of the anode lead is made to form an angle of 90° or less with the lower end of the anode lead in a facing state.

6. The manufacturing method according to any one of claims 1 to 5, wherein: A short diameter of a focal point of the laser beam formed on the predetermined area is 0.01 mm or more but 0.05 mm or less.

7. A solid electrolytic capacitor comprising an anode body, an anode lead and an anode lead frame, wherein: The anode lead extends forward from the front surface of the anode body in a front-to-rear direction; The anode lead frame has an upright portion; The anode lead has a front end welded to a predetermined area on a rear surface of the upright portion; and At least one of a front end of the anode lead and a predetermined area of ​​the upright portion is formed with a laser track.

8. The solid electrolytic capacitor according to claim 7, wherein: The dimension of the upright portion is greater than the dimension of the front end of the anode lead in a lateral direction perpendicular to the front-rear direction; The upright portion is formed with two notches; The two notches are respectively formed on opposite ends of the upright portion in the transverse direction; Each of the notches is recessed toward the inside of the upright portion in the lateral direction.

9. The solid electrolytic capacitor according to claim 7, wherein: The upright portion has a front surface formed with a recess; and The recessed portion is located at a position corresponding to the predetermined area in a vertical plane perpendicular to the front-rear direction, and the recessed portion is recessed rearward.

10. The solid electrolytic capacitor according to claim 9, wherein: The recess has an elliptical shape; The recess has a first dimension in a transverse direction perpendicular to the front-rear direction and a second dimension in an upper-lower direction perpendicular to both the front-rear direction and the transverse direction; and The second size is greater than the first size.

11. The solid electrolytic capacitor according to claim 10, wherein: The second size is equal to or greater than twice the first size.

12. The solid electrolytic capacitor according to any one of claims 7 to 11, wherein: The solid electrolytic capacitor includes an outer coating resin; The anode body and the anode lead are disposed in the outer coating resin; A distance between a front surface of the outer coating resin and a front surface of the anode body is 0.3 mm or more but 0.5 mm or less.

13. The solid electrolytic capacitor according to any one of claims 7 to 11, wherein: The solid electrolytic capacitor comprises a cathode layer and a cathode lead frame; The cathode layer is electrically connected to the cathode lead frame via a conductive adhesive; The conductive adhesive is a conductive metal paste.

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