Electrolytic capacitor manufacturing method and electrolytic capacitor

Abstract

A method for manufacturing an electrolytic capacitor is provided that can bond a plurality of electrode foils and electrode leads in a small bonding area with high bonding strength and low connection resistance. [Solution] A method for manufacturing an electrolytic capacitor includes an electrode foil laminate formation process in which a plurality of electrode foils (111) are stacked to form an electrode foil laminate (11); an electrode lead arrangement process in which an electrode lead (20) is arranged on a portion of the lower surface (S2) of the electrode foil laminate (11); a groove formation process in which a slit-shaped groove (G) is formed in the electrode foil laminate (11) by irradiating a portion of the upper surface (S1) of the electrode foil laminate (11) opposite the electrode lead (20) with a first laser light while scanning along a first direction intersecting the stacking direction; and a joint formation process in which a second laser light is irradiated into the groove (G) with an irradiation spot diameter equal to or smaller than the width (B) of the groove (G) on the upper surface (S1) of the electrode foil laminate (11) to form a joint (30) that joins the plurality of electrode foils (111) to each other within the groove (G) and joins the electrode lead (20).

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrolytic capacitor and an electrolytic capacitor, and more particularly to a method for manufacturing an electrolytic capacitor including a capacitor element having a plurality of stacked electrode foils, and an electrolytic capacitor. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an electrolytic capacitor in which anode tabs and cathode tabs connected to a plurality of stacked anode bodies and a plurality of stacked cathode bodies, respectively, are joined to anode connecting portions and cathode connecting portions of an anode lead member and a cathode lead member by crimping.

[0003] Patent Document 2 discloses that in a stacked solid electrolytic capacitor, each of the lead portions of a plurality of anode foils and each of the lead portions of a plurality of cathode foils are joined by laser welding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 181668 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-019233 Summary of the Invention [Problem to be solved by the invention]

[0005] In an electrode laminated structure as in Patent Document 1, when joining to an electrode lead terminal is performed by crimping, if the number of electrode foils to be laminated is large, some electrode foils may not be connected to the electrode lead terminal, increasing the connection resistance, or the electrode lead terminal may not be folded back enough, resulting in insufficient joining.

[0006] When stacked electrode foils are welded with a laser as in Patent Document 2, the electrode metal melted by laser irradiation may blow back toward the irradiated side due to gas generated from the molten part, causing large blowholes inside the weld, which may lead to a decrease in joint strength and an increase in contact resistance. Therefore, even if an attempt is made to increase the area of ​​the laser weld to obtain high joint strength and low contact resistance, it has been difficult to form a weld with few blowholes deep into the stack.

[0007] In particular, when welding a laminate of electrode foils that have a roughened surface or an oxide layer such as a chemical conversion film, it is necessary to melt and join the metal base material (e.g., aluminum) of the electrode foil while removing the oxide layer. Attempting to simultaneously weld the metal base material and remove the oxide layer generates expanded gas from the air layer in the roughened surface or oxide layer, resulting in pores in the molten metal pool or blowback of the molten metal toward the laser irradiation side. This can result in large blowholes inside the weld, reducing joint strength and increasing contact resistance.

[0008] The present disclosure provides a method for manufacturing an electrolytic capacitor that can bond multiple electrode foils and electrode leads in a small bonding area with high bonding strength and low connection resistance, and an electrolytic capacitor. [Means for solving the problem]

[0009] A method for manufacturing an electrolytic capacitor according to one aspect of the present disclosure is a method for manufacturing an electrolytic capacitor including a capacitor element having a plurality of stacked electrode foils, the method comprising: an electrode foil laminate forming step of stacking a plurality of electrode foils to form an electrode foil laminate; an electrode lead arranging step of arranging an electrode lead on a portion of a lower surface of the electrode foil laminate in a stacking direction; a groove forming step of irradiating a portion of an upper surface of the electrode foil laminate in the stacking direction opposite the electrode lead with a first laser beam while scanning the portion along a first direction intersecting the stacking direction to form a slit-shaped groove in the electrode foil laminate; and a joint forming step of irradiating the inside of the groove with a second laser beam with an irradiation spot diameter equal to or smaller than a width of the groove on the upper surface of the electrode foil laminate, thereby joining the plurality of electrode foils to each other within the groove and forming a joint that joins the electrode foils to the electrode lead.

[0010] An electrolytic capacitor according to one embodiment of the present disclosure includes a capacitor element having an electrode foil laminate in which multiple electrode foils are stacked, and an electrode lead joined to a portion of the lower surface in the stacking direction of the electrode foil laminate. The electrode foil laminate has a joint that joins the multiple electrode foils to each other and to the electrode lead. The joint has a slit shape on the upper surface in the stacking direction of the electrode foil laminate, extending in a first direction intersecting the stacking direction, and is formed from the upper surface to the lower surface. The ratio of the length from the upper surface to the lower surface of the joint to the width of the slit shape of the joint on the upper surface is 200 to 12,000. [Effects of the Invention]

[0011] According to the present disclosure, multiple electrode foils and electrode leads of an electrolytic capacitor can be joined in a small joining area with high joining strength and low connection resistance. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic perspective view illustrating a method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic partial plan view illustrating a method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic partial cross-sectional view illustrating a method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic partial perspective view of an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure taken along line PP in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure taken along line QQ in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Embodiment) (1) Overview Hereinafter, a method for manufacturing an electrolytic capacitor and an electrolytic capacitor according to an embodiment will be described with reference to the drawings (FIGS. 1 to 6). However, the embodiment described below is merely one of various embodiments of the present disclosure. The embodiment described below can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, each figure described in the embodiment described below is a schematic diagram, and the ratios of the sizes and thicknesses of the components in the figures do not necessarily reflect the actual dimensional ratios.

[0014] In the following description, the direction in which the multiple electrode foils 111 in the electrode foil laminate 11 are stacked is referred to as the "stacking direction" (Z direction), and the direction intersecting the stacking direction is referred to as the "first direction." In the following description and drawings, the direction in which the two electrode leads 20A, 20B are aligned in the electrolytic capacitor 1 is referred to as the "X direction," and the first direction is referred to as the direction (Y direction) perpendicular to the stacking direction (Z direction) and the X direction. That is, the X direction, Y direction, and Z direction are perpendicular to one another. However, these directions are merely examples and are not intended to limit the directions during manufacture or use of the electrolytic capacitor 1. Arrows indicating the X direction, Y direction, and Z direction in the drawings are merely shown for explanatory purposes and do not represent actual objects. Furthermore, in the stacking direction (Z direction), the direction of the electrode lead 20 is referred to as "bottom," and the opposite direction is referred to as "top," with the upper surface of the electrode foil laminate 11 in the stacking direction referred to as the "upper surface S1" and the lower surface referred to as the "lower surface S2."

[0015] <Manufacturing method of electrolytic capacitors> The method for manufacturing electrolytic capacitor 1 of this embodiment (hereinafter also referred to as manufacturing method (U)) is a method for manufacturing electrolytic capacitor 1 including capacitor element 10 having a plurality of electrode foils 111 stacked one on top of the other.

[0016] The manufacturing method (U) comprises an electrode foil laminate forming step, an electrode lead arranging step, a groove forming step, and a joint forming step.

[0017] In the electrode foil laminate forming step, a plurality of electrode foils 111 are laminated to form the electrode foil laminate 11. In the electrode lead arrangement step, the electrode lead 20 is arranged on a part of the lower surface S2 of the electrode foil laminate 11 in the lamination direction (Z direction). In the groove forming process, a first laser beam is irradiated onto the portion of the upper surface S1 of the electrode foil laminate 11 opposite the electrode lead 20 in the stacking direction (Z direction) while scanning along a first direction (Y direction) that intersects with the stacking direction (Z direction), thereby forming a slit-shaped groove G in the electrode foil laminate 11 (see Figure 2). In the joint forming process, after the groove forming process, a second laser beam is irradiated into the inside of the groove G with an irradiation spot diameter equal to or smaller than the width B of the groove G on the upper surface S1 of the electrode foil laminate 11, thereby forming joints 30 that join the multiple electrode foils 111 to each other inside the groove G and also join them to the electrode lead 20 (see Figures 4 to 6).

[0018] The manufacturing method (U) of the electrolytic capacitor 1 of this embodiment includes the above steps, and thereby makes it possible to bond a plurality of electrode foils 111 and electrode leads 20 in a small bonding area with high bonding strength and low connection resistance.

[0019] In the manufacturing method (U) of the electrolytic capacitor 1, an electrode foil laminate 11 is formed by stacking multiple electrode foils 111 (electrode foil laminate formation process), then an electrode lead 20 is positioned and placed on a part of the lower surface S2 of the electrode foil laminate 11 (electrode lead placement process), then a laser is irradiated onto the part of the upper surface S1 of the electrode foil laminate 11 opposite the electrode lead 20 to form a slit-shaped groove G (groove formation process), and after this groove formation process, a laser is again irradiated into the inside of the groove G to join the multiple electrode foils 111 to each other and to form a joint 30 that joins to the electrode lead 20 (joint formation process).

[0020] In the groove forming process, when the plurality of electrode foils 111 are melted and cut with a laser, the oxide layer and the roughened portion are crushed, and the gas generated during this process is released to the outside through the groove G. At the same time, a molten metal pool (molten pool) containing a mixture of the molten metal of the electrode foil 111 and the crushed oxide layer remains inside the groove G. Thereafter, the slit-shaped groove G is again irradiated with a laser with a spot diameter equal to or smaller than the width B (B≧laser irradiation diameter), thereby remelting the molten metal pool and forming a joint 30 that joins the plurality of electrode foils 111 and also joins to the electrode lead 20 arranged in contact with the plurality of electrode foils 111.

[0021] In this way, good joints 30 with few voids can be formed deep and narrow in the electrode foil laminate 11 in which many electrode foils 111 are laminated, and the multiple electrode foils 111 can be joined to the electrode leads 20 in a small joining area with high joining strength and low connection resistance. As a result, the electrolytic capacitor 1 produced can be miniaturized due to the smaller joining area, and can be highly reliable due to the high joining strength between the multiple electrode foils 111 and the electrode leads 20.

[0022] <Electrolytic capacitor> 4 shows a portion of the electrolytic capacitor 1 of this embodiment including the capacitor element 10 and the electrode lead 20. The electrolytic capacitor 1 includes the capacitor element 10 having the electrode foil laminate 11 in which a plurality of electrode foils 111 are laminated, and the electrode lead 20 joined to a part of the lower surface S2 of the electrode foil laminate 11 in the lamination direction (Z direction).

[0023] In the electrolytic capacitor 1, the electrode foil laminate 11 has joints 30 (30A, 30B) that join multiple electrode foils 111 (111A, 111B) to one another and to electrode leads 20 (20A, 20B). The joints 30 have a slit shape that extends in a first direction (Y direction) that intersects with the stacking direction (Z direction) on the upper surface S1 of the electrode foil laminate 11 in the stacking direction (Z direction), and are formed from the upper surface S1 to the lower surface S2. In the electrolytic capacitor 1, the ratio (T / d) of the length T (see FIG. 5) from the upper surface S1 to the lower surface S2 of the joint 30 to the width d (see FIG. 6) of the slit shape of the joint 30 on the upper surface S1 is 200 or more and 12,000 or less.

[0024] In the electrolytic capacitor 1, the width d of the joint 30 is, for example, about 1 μm, and the length (depth) T of the joint 30 is, for example, about 3 mm. In the electrolytic capacitor 1, the joint 30 having an extremely small width d and a large length (depth) T can be formed by using the above-described manufacturing method (U).

[0025] In this way, in the electrolytic capacitor 1 of this embodiment, the width of the region required for bonding in the capacitor element 10 can be reduced, and the electrolytic capacitor 1 can be made smaller while maintaining high bonding strength and low contact resistance.

[0026] (2)Details <Manufacturing method of electrolytic capacitors> The manufacturing method (U) of the electrolytic capacitor 1 according to this embodiment will be described in more detail below. In this embodiment, as a representative example, the electrolytic capacitor 1 will be described as a hybrid electrolytic capacitor 1 that includes both a solid electrolyte such as a conductive polymer and a liquid component such as an electrolytic solution.

[0027] The manufacturing method (U) includes an electrode foil laminate forming step, an electrode lead arranging step, a groove forming step, and a joint forming step. The manufacturing method (U) may further include a surface roughening step, an oxide layer forming step, etc., before the electrode foil laminate forming step. Each step will be described below.

[0028] [Surface roughening process] In this step, a roughening treatment is performed on the surface of each of the plurality of electrode foils 111. When using electrode foils 111 with roughened surfaces, there is a great benefit in adopting manufacturing method (U) because a large amount of gas is generated by pulverization when the electrode foils 111 are melted and cut with a laser.

[0029] The electrode foils 111 include an anode foil 111A and a cathode foil 111B. The anode foil 111A is a metal foil containing a valve metal such as aluminum, tantalum, or niobium. The cathode foil 111B is a metal foil containing a valve metal such as aluminum, tantalum, or niobium.

[0030] The surface roughening treatment can be performed by, for example, etching a part or all of the surfaces of electrode foils 111A and 111B. The surface roughening treatment forms a roughened portion including fine irregularities (etching pits) on the surfaces of electrode foils 111A and 111B. The etching treatment can be performed by, for example, direct current electrolysis or alternating current electrolysis.

[0031] [Oxide layer formation process] In this step, an oxide layer is formed on the surface of each of the plurality of electrode foils 111. When the electrode foils 111 having the oxide layer formed on their surfaces are melted and cut by a laser, a large amount of gas is generated by pulverization, and therefore, there are great benefits to adopting manufacturing method (U).

[0032] In this step, the surface of the anode foil 111A is chemically converted to form an oxide layer (dielectric layer) containing an oxide of the valve metal that constitutes the anode foil 111A on the surface of the anode foil 111A. In the anode foil 111A that has been subjected to the surface roughening treatment, the oxide layer (dielectric layer) is formed along the fine irregularities in the roughened portion of the surface of the anode foil 111A. Similarly, an oxide layer may be formed on the surface of the cathode foil 111B.

[0033] The oxide layer (dielectric layer) may be formed by, for example, atomic layer deposition, resistance heating vapor deposition, electron beam heating, etc. In this case, the oxide layer may be an oxide of, for example, molybdenum, vanadium, tungsten, titanium, tantalum, niobium, hafnium, zirconium, etc.

[0034] [Electrode foil laminate formation process] In this step, a plurality of electrode foils 111 are laminated to form an electrode foil laminate 11.

[0035] In this step, as shown in FIG. 1, an electrode foil laminate 11 is typically formed by stacking an anode foil 111A, a separator 12, and a cathode foil 111B multiple times. A conductive polymer serving as a solid electrolyte may be disposed between the anode foil 111A and the cathode foil 111B, along with the separator 12. Examples of materials for the separator 12 include cellulose, polyethylene terephthalate (PET), vinylon, and aramid fiber. The separator 12 can retain liquid components such as an electrolyte solution by impregnation. Examples of conductive polymers include polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene) (PEDOT), and polyaniline.

[0036] [Electrode lead placement process] In this step, the electrode lead 20 is disposed on a part of the lower surface S2 of the electrode foil laminate 11 in the lamination direction (Z direction).

[0037] The electrode lead 20 typically includes an anode lead 20A and a cathode lead 20B. The electrode lead 20 typically has a portion of its surface exposed to the outside of the case of the electrolytic capacitor 1, thereby serving as a current collector, and this current collector is joined to a substrate on which the electrolytic capacitor 1 is mounted, using solder or the like.

[0038] The electrode lead 20 preferably has a shape including a flat surface for connection with the substrate on which it is mounted, such as a simple flat plate shape or an L-shaped plate shape.

[0039] The material constituting the electrode lead 20 is usually a metal such as aluminum or copper, and aluminum is preferred.

[0040] This step is carried out by, for example, positioning and arranging the electrode leads 20A, 20B, and then arranging the electrode foil laminate 11 formed in the electrode foil laminate forming step thereon.

[0041] [Groove formation process] In this process, a first laser beam is irradiated onto the portion of the upper surface S1 of the electrode foil laminate 11 opposite the electrode lead 20 in the stacking direction (Z direction) while scanning along a first direction (Y direction) that intersects with the stacking direction (Z direction), thereby forming a slit-shaped groove G in the electrode foil laminate 11 (see Figure 2).

[0042] In this step, the first laser light melts the plurality of electrode foils 111, thereby forming a molten metal pool.

[0043] As the first laser light, for example, a YAG laser light or a fiber laser light is used.

[0044] The first laser light may be continuous light or pulsed light, but is preferably continuous light.

[0045] The scanning of the irradiation with the first laser light may be performed once, or may be performed twice or more.

[0046] 3, the grooves G are formed so that the maximum depth D of the grooves G formed by the first laser light is smaller than the thickness T of the electrode foil laminate 11 from the upper surface S1 to the lower surface S2. The ratio (D / T) of the maximum depth D of the grooves G from the upper surface S1 of the electrode foil laminate 11 to the thickness T of the electrode foil laminate 11 from the upper surface S1 to the lower surface S2 is preferably 0.5 or more and 0.9 or less. In this case, when the second laser light is irradiated in the joint forming step, the connection strength of the joints between the plurality of electrode foils 111 and the electrode leads 20 can be increased and the connection resistance can be reduced.

[0047] If the ratio (D / T) exceeds 0.9, the groove G is formed up to or close to the lower surface S2 of the electrode foil laminate 11, and the electrode lead 20 in contact with the lower surface S2 may be damaged when the molten metal pool is remelted by irradiating the second laser light in the joint forming step. On the other hand, if the ratio (D / T) is less than 0.5, the melted portion may not reach the electrode lead 20 when the molten metal pool is remelted by irradiating the second laser light in the joint forming step, and the electrode lead 20 and the electrode foil laminate 11 may not be joined.

[0048] The ratio (D / T) may be 0.85 or less, 0.75 or less, or 0.7 or less, or 0.52 or more, or 0.54 or more.

[0049] [Joint forming process] In this process, after the groove forming process, a second laser light is irradiated into the inside of the groove G with an irradiation spot diameter equal to or smaller than the width B of the groove G on the upper surface S1 of the electrode foil laminate 11, thereby joining the multiple electrode foils 111 to each other inside the groove G and forming a joining portion 30 that joins the electrode foils 111 to the electrode lead 20.

[0050] In this step, it is important that the diameter of the irradiation spot of the second laser light is equal to or smaller than the width B of the groove G. If the laser spot diameter is larger than the width B of the slit-shaped groove G, the portion of the electrode foil 111 located around the groove G will melt, generating gas from the oxide layer and roughened surface of that portion, causing voids (air pores) to form in the remelted molten metal pool, thereby reducing the bonding strength. The width B can be determined by averaging width values ​​measured at any multiple positions along the length of the slit-shaped groove G.

[0051] In this step, the molten metal pool is re-melted by the second laser light.

[0052] As the second laser light, for example, a YAG laser light or a fiber laser light is used.

[0053] The second laser beam is preferably irradiated as a pulsed beam. If the second laser beam is irradiated as a continuous beam, heat is transferred to the portion of electrode foil 111 located around groove G, which tends to melt the portion, generating gas from the oxide layer or roughened surface in that portion, and the remelted molten metal pool may contain voids (air pores), resulting in a decrease in bonding strength. By irradiating the second laser beam as a pulsed beam, the heat transfer area within the groove can be kept small even when the laser is irradiated with an intensity sufficient to remelt the molten metal pool, thereby suppressing melting and gas generation in the portion of electrode foil 111 located around groove G.

[0054] The scanning of the second laser light irradiation may be performed once, or twice or more times.

[0055] When viewed from the stacking direction (Z direction), the ratio (W / L) of the length W of the joint portion 30 in the first direction (Y direction) to the length L of the electrode foil laminate 11 in the first direction (Y direction) is preferably 0.8 or more and less than 1.0. In this case, the connection strength between the multiple electrode foils 111 and the electrode leads 20 can be increased and the connection resistance can be reduced (see FIG. 5).

[0056] Increasing the ratio (W / L) of the length W in the first direction (Y direction) of the joint 30 to the length L in the first direction (Y direction) of the electrode foil laminate 11 increases the proportion of the joint area in the electrode foil laminate 11, thereby increasing the connection strength and reducing the connection resistance. However, if the length W in the first direction (Y direction) of the joint 30 is increased to the same value as the length L in the first direction (Y direction) of the electrode foil laminate 11 (W / L = 1.0), the groove will be machined up to the edge of the electrode foil laminate 11 in the first direction (Y direction), causing the molten metal to spill outward, preventing the formation of a sufficient pool of molten metal in the groove G, and in some cases preventing the formation of a joint 30 with sufficient joint strength.

[0057] The ratio (W / L) may be 0.98 or less, 0.95 or less, 0.9 or less, or 0.87 or less. The ratio (W / L) may be 0.82 or more, or 0.84 or more.

[0058] The distance from the end face of the electrode foil laminate 11 to the joint 30 in the direction (X direction) perpendicular to the first direction (Y direction) and the stacking direction (Z direction) is preferably 0.5 mm or more. The distance may be 0.8 mm or more, or 1.0 mm or more. The distance is, for example, 3 mm or less. When the distance is within this range, gas generated during irradiation with the first laser light can be allowed to escape not only toward the upper surface but also toward the end face, and it is possible to prevent the molten metal from spilling out of the end face during irradiation with the second laser light, preventing a sufficient molten metal pool from being formed in the groove G. This allows the formation of a joint 30 with sufficient joint strength and fewer voids.

[0059] In this manner, the portion of the electrolytic capacitor 1 that includes the capacitor element 10 and the electrode leads 20 can be manufactured.

[0060] In manufacturing method (U), each of the plurality of electrode foils 111 may be an anode foil 111A. In this case, capacitor element 10 may further include a cathode foil 111B facing anode foil 111A, and a conductive polymer disposed between anode foil 111A and cathode foil 111B.

[0061] Capacitor element 10 may be impregnated with, for example, a liquid component.

[0062] The resulting capacitor element 10 and the portion including the electrode leads 20 are housed in a case or the like that is made up of a housing having an opening and a sealing member that closes the opening of the housing, thereby obtaining the electrolytic capacitor 1.

[0063] <Electrolytic capacitor> The electrolytic capacitor 1 of this embodiment includes a capacitor element 10 and an electrode lead 20. The electrode foil laminate 11 in the electrolytic capacitor 1 includes a joint 30 that joins a plurality of electrode foils 111 to one another and to the electrode lead 20. The electrolytic capacitor 1 may further include, for example, a case that houses the capacitor element 10 and the electrode lead 20. The case may be composed of, for example, a housing having an opening and a sealing body that closes the opening of the housing.

[0064] [Capacitor element] Capacitor element 10 has electrode foil laminate 11 in which a plurality of electrode foils 111 are laminated.

[0065] Each of the plurality of electrode foils 111 forming capacitor element 10 may be an anode foil 111A. Capacitor element 10 may further include a cathode foil 111B facing anode foil 111A, and a conductive polymer disposed between anode foil 111A and cathode foil 111B.

[0066] Each of the plurality of electrode foils 111 forming capacitor element 10 may have a roughened portion on its surface. Also, each of the plurality of electrode foils 111 may have an oxide layer on its surface.

[0067] Capacitor element 10 may be impregnated with, for example, a liquid component.

[0068] [Electrode lead] The electrode lead 20 is joined to a part of the lower surface S2 of the electrode foil laminate 11 in the lamination direction (Z direction).

[0069] [Joint part] The joint portion 30 has a slit shape extending in a first direction (Y direction) intersecting the stacking direction (Z direction) on the upper surface S1 of the electrode foil laminate 11 in the stacking direction (Z direction), and is formed from the upper surface S1 to the lower surface S2.

[0070] The width d of the slit shape of the joint 30 at the upper surface S1 is, for example, 0.1 μm or more and 5 μm or less, preferably 0.5 μm or more and 3 μm or less, and more preferably 0.7 μm or more and 2 μm or less (see FIG. 6). As shown in FIG. 6, the joint 30 is formed so that the width d of the joint 30 gradually decreases from the upper surface S1 toward the lower surface S2.

[0071] The length T from the upper surface S1 to the lower surface S2 of the joint 30 is, for example, 0.5 mm or more and 10 mm or less, preferably 1 mm or more and 5 mm or less, and more preferably 2 mm or more and 4 mm or less.

[0072] It is important that the ratio (T / d) of the length T from the upper surface S1 to the lower surface S2 of the joint 30 to the width d of the slit shape of the joint 30 on the upper surface S1 is 200 or more and 12000 or less. By doing so, the width of the region required for bonding in the capacitor element 10 can be reduced, and the electrolytic capacitor 1 can be made smaller while maintaining high bonding strength and low connection resistance.

[0073] The ratio (T / d) is, for example, 500 or more, preferably 1000 or more, and more preferably 2000 or more. The ratio (T / d) is, for example, 10000 or less, and may be 8000 or less, 5000 or less, or 4000 or less.

[0074] When viewed from the stacking direction (Z direction), the ratio (W / L) of the length W of the joint 30 in the first direction (Y direction) to the length L of the electrode foil laminate 11 in the first direction (Y direction) is preferably 0.8 or more and less than 1.0 (see FIG. 5). In this case, the connection strength between the multiple electrode foils 111 and the electrode leads 20 can be increased and the connection resistance can be reduced. Note that, as shown in FIG. 5, the joint 30 is formed so that the length W of the joint 30 in the first direction (Y direction) gradually decreases from the upper surface S1 toward the lower surface S2.

[0075] Increasing the ratio (W / L) of the length W in the first direction (Y direction) of the joint 30 to the length L in the first direction (Y direction) of the electrode foil laminate 11 increases the proportion of the joint area in the electrode foil laminate 11, thereby increasing the connection strength and reducing the connection resistance. However, if the length W in the first direction (Y direction) of the joint 30 is increased to the same value as the length L in the first direction (Y direction) of the electrode foil laminate 11 (W / L = 1.0), the groove will be machined close to the end of the electrode foil laminate 11 in the first direction (Y direction), causing the molten metal to spill outward, preventing the formation of a sufficient molten metal pool in the groove G, and in some cases, preventing the formation of a joint 30 with sufficient joint strength.

[0076] The ratio (W / L) may be 0.98 or less, 0.95 or less, 0.9 or less, or 0.87 or less. The ratio (W / L) may be 0.82 or more, or 0.84 or more.

[0077] [Liquid component] When electrolytic capacitor 1 contains a liquid component, the liquid component is, for example, partially impregnated into capacitor element 10, specifically, into separator 12 of capacitor element 10, etc.

[0078] An example of the liquid component is an electrolytic solution. For example, an organic solvent is used as the electrolytic solution. Examples of the organic solvent include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, and propylene glycol; sulfone compounds such as sulfolane, dimethyl sulfoxide, and diethyl sulfoxide; lactone compounds such as γ-butyrolactone and γ-valerolactone; carbonate compounds such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate; diether compounds of polyhydric alcohols such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; and monohydric alcohols such as methanol, ethanol, and propanol.

[0079] The electrolytic solution may contain a solute, such as an acid component such as an organic acid, an inorganic acid, or a complex acid compound of an organic acid and an inorganic acid; a base component such as an amine or a quaternary ammonium salt; a salt of an acid and a base; a nitro compound; or a phenol compound.

[0080] <Evaluation of bonding strength> In order to evaluate the bonding strength between the electrode foils 111 and the electrode leads 20, samples were prepared in which the electrode leads 20 were bonded to the electrode foil laminate 11, and the peel strength from the electrode lead 20 side was measured.

[0081] [Sample preparation] Sample 1 (joined by the joining method of manufacturing method (U) of this embodiment): Thirty sheets of electrode foil were stacked, placed on an electrode lead, and joined by the manufacturing method (U) of this embodiment to prepare Sample 1. Sample 2 (joined by caulking): A single layer of electrode foil was superimposed on an electrode lead, and crimping was performed in the same manner as in the conventional method to produce Sample 2.

[0082] [Peel strength measurement] The electrode foils of the samples (Sample 1 and Sample 2) were fixed to the base of the tension / compression tester, and the electrode leads were clamped. In this state, a tensile test was performed, and the samples were peeled off to measure the peel strength. The measured peel strength of each sample was as follows: Sample 1: Approx. 7N Sample 2: Approx. 2N

[0083] [Evaluation results] In Sample 1 bonded by the bonding method of manufacturing method (U) of this embodiment, the peel strength was three times or more higher than that of Sample 2 bonded by crimping. As can be seen from this result, it was found that manufacturing method (U) of this embodiment has higher bondability than the conventional manufacturing method. In the electrolytic capacitor obtained by bonding by manufacturing method (U) of this embodiment, the lead and electrode foil are fused and bonded, so it is thought that the resistance of the bonded portion is also lower than that of the conventional manufacturing method.

[0084] (summary) As is clear from the above embodiments, the present disclosure includes the following aspects. In the following, reference numerals are given in parentheses only to clarify the correspondence with the embodiments.

[0085] A first aspect of the manufacturing method for an electrolytic capacitor (1) is a manufacturing method for an electrolytic capacitor (1) including a capacitor element (10) having a plurality of stacked electrode foils (111), and includes an electrode foil laminate forming process, an electrode lead arranging process, a groove forming process, and a joint forming process. In the electrode foil laminate forming process, a plurality of electrode foils (111) are stacked to form an electrode foil laminate (11). In the electrode lead arranging process, an electrode lead (20) is arranged on a part of a lower surface (S2) in the stacking direction (Z direction) of the electrode foil laminate (11). In the groove forming process, a first laser beam is irradiated onto a part of an upper surface (S1) in the stacking direction (Z direction) of the electrode foil laminate (11) opposite to the electrode lead (20) while scanning along a first direction (Y direction) intersecting the stacking direction (Z direction), thereby forming a slit-shaped groove (G) in the electrode foil laminate (11). In the joint forming process, after the groove forming process, a second laser beam is irradiated into the groove (G) with an irradiation spot diameter equal to or smaller than the width (B) of the groove (G) on the upper surface (S1) of the electrode foil laminate (11), thereby forming joints (30) that join the multiple electrode foils (111) to each other inside the groove (G) and to the electrode lead (20).

[0086] According to the first aspect, the electrode foils (111) and the electrode lead (20) can be bonded together in a small bonding area with high bonding strength and low connection resistance.

[0087] The method for producing the electrolytic capacitor (1) of the second aspect is the same as that of the first aspect, and further comprises a surface roughening step of roughening the surface of each of the plurality of electrode foils before the electrode foil laminate forming step.

[0088] According to the second aspect, when the electrode foil (111) is melted and cut by a laser, a large amount of gas is generated by pulverization. Therefore, this can also be applied to the case where an electrode foil (111) whose surface has been roughened is used, and there are great benefits to adopting the present disclosure.

[0089] The method for producing the electrolytic capacitor (1) of the third aspect is the same as that of the first or second aspect, and further includes an oxide layer forming step of forming an oxide layer on the surface of each of the plurality of electrode foils before the electrode foil laminate forming step.

[0090] According to the third aspect, when the electrode foil (111) is melted and cut by a laser, a large amount of gas is generated by pulverization. Therefore, the third aspect can be applied to the case where an electrode foil (111) having an oxide layer formed on its surface is used, and the benefits of adopting the present disclosure are great.

[0091] In the manufacturing method of the electrolytic capacitor (1) of the fourth aspect, in any one of the first to third aspects, the ratio of the maximum depth (D) of the groove (G) from the upper surface (S1) of the electrode foil laminate (11) to the thickness (T) from the upper surface (S1) to the lower surface (S2) of the electrode foil laminate (11) is 0.5 or more and 0.9 or less.

[0092] According to the fourth aspect, the connection strength between the electrode foils (111) and the electrode lead (20) can be increased and the connection resistance can be reduced.

[0093] In the manufacturing method of the electrolytic capacitor (1) of the fifth aspect, in any one of the first to fourth aspects, when viewed from the stacking direction (Z direction), the ratio of the length (W) of the joint in a first direction (Y direction) to the length (L) in the first direction of the electrode foil laminate (11) is 0.8 or more and less than 1.0.

[0094] According to the fifth aspect, the connection strength between the electrode foils (111) and the electrode lead (20) can be increased and the connection resistance can be reduced.

[0095] In the sixth aspect of the method for manufacturing the electrolytic capacitor (1), in any one of the first to fifth aspects, the first laser light is continuous light and the second laser light is pulsed light.

[0096] According to the sixth aspect, in particular, by irradiating the second laser beam as a pulsed beam, the heat transfer area within the groove can be kept small even when the laser beam is irradiated with an intensity sufficient to remelt the molten metal pool, so that melting and gas generation in the portion of the electrode foil (111) located around the groove (G) can be suppressed.

[0097] In the seventh aspect of the method for manufacturing the electrolytic capacitor (1), in any one of the first to sixth aspects, in the groove forming step, a molten metal pool is formed by melting the multiple electrode foils (111) with a first laser beam, and in the joint forming step, the molten metal pool is re-melted with a second laser beam.

[0098] According to the seventh aspect, by forming a molten metal pool and remelting it using a laser beam, it is possible to bond a plurality of electrode foils (111) and electrode leads (20) together in a small bonding area with high bonding strength and low connection resistance.

[0099] In the eighth aspect of the method for manufacturing an electrolytic capacitor (1), in any one of the first to seventh aspects, each of the plurality of electrode foils (111) is an anode foil (111A), and the capacitor element (10) further includes a cathode foil (111B) facing the anode foil (111A), and a conductive polymer disposed between the anode foil (111A) and the cathode foil (111B).

[0100] According to the eighth aspect, the bonding method in the manufacturing method of the present disclosure can also be applied to the anode foil (111A).

[0101] In the ninth aspect of the method for producing the electrolytic capacitor (1), in any one of the first to eighth aspects, the capacitor element is impregnated with a liquid component.

[0102] According to a ninth aspect, the present disclosure can also be applied to the manufacture of an electrolytic capacitor (1) in which a capacitor element (10) is impregnated with a liquid component.

[0103] An electrolytic capacitor (1) of a tenth aspect includes a capacitor element (10) having an electrode foil laminate (11) in which a plurality of electrode foils (111) are stacked, and an electrode lead (20) joined to a portion of a lower surface (S2) in the stacking direction (Z direction) of the electrode foil laminate (11). The electrode foil laminate (11) has a joint (30) that joins the plurality of electrode foils (111) to each other and to the electrode lead (20). The joint (30) has a slit shape that extends in a first direction (Y direction) intersecting the stacking direction (Z direction) on an upper surface (S1) in the stacking direction (Z direction) of the electrode foil laminate (11), and is formed from the upper surface (S1) to the lower surface (S2). The ratio of the length (T) from the upper surface (S1) to the lower surface (S2) of the joint (30) to the width (W) of the slit shape of the joint (30) on the upper surface (S1) is 200 or more and 12,000 or less.

[0104] According to the tenth aspect, the electrolytic capacitor (1) can bond a plurality of electrode foils (111) and electrode leads (20) in a small bonding area with high bonding strength and low connection resistance, thereby enabling miniaturization of the electrolytic capacitor (1).

[0105] In the electrolytic capacitor (1) of the eleventh aspect, in the tenth aspect, each of the plurality of electrode foils (111) has a roughened portion on the surface.

[0106] According to the eleventh aspect, when the electrode foil (111) is melted and cut by a laser, a large amount of gas is generated by pulverization. Therefore, this aspect can be applied to the case where the electrode foil (111) has a roughened surface, and the electrolytic capacitor (1) can bond multiple electrode foils (111) and electrode leads (20) in a small bonding area with high bonding strength and low connection resistance.

[0107] In the electrolytic capacitor (1) of the twelfth aspect, in the tenth or eleventh aspect, each of the plurality of electrode foils (111) has an oxide layer on the surface.

[0108] According to the twelfth aspect, when the electrode foil (111) is melted and cut by a laser, a large amount of gas is generated by pulverization. Therefore, this aspect can be applied to the case where the electrode foil (111) has an oxide layer on its surface. In the electrolytic capacitor (1), the plurality of electrode foils (111) and the electrode leads (20) can be joined in a small joining area with high joining strength and low connection resistance.

[0109] In the electrolytic capacitor (1) of the thirteenth aspect, in any one of the tenth to twelfth aspects, when viewed from the stacking direction (Z direction), the ratio of the length (W) in the first direction (Y direction) of the joint portion (30) to the length (L) in the first direction (Y direction) of the electrode foil laminate (11) is 0.8 or more and less than 1.0.

[0110] According to the thirteenth aspect, the electrolytic capacitor (1) can increase the connection strength between the electrode foils (111) and the electrode leads (20) and reduce the connection resistance.

[0111] In the electrolytic capacitor (1) of a fourteenth aspect, in any one of the tenth to thirteenth aspects, each of the plurality of electrode foils (111) is an anode foil (111A), and the capacitor element (10) further includes a cathode foil (111B) facing the anode foil (111A), and a conductive polymer disposed between the anode foil (111A) and the cathode foil (111B).

[0112] According to the fourteenth aspect, in the electrolytic capacitor (1), by joining a plurality of anode foils (111A), the plurality of electrode foils (111) and the electrode lead (20) can be joined in a small joining area with high joining strength and low connection resistance.

[0113] In the electrolytic capacitor (1) of the fifteenth aspect, in any one of the tenth to fourteenth aspects, the capacitor element (10) is impregnated with a liquid component.

[0114] According to the fifteenth aspect, even in an electrolytic capacitor (1) in which a liquid component is impregnated in the capacitor element (10), a plurality of electrode foils (111) and electrode leads (20) can be joined in a small joining area with high joining strength and low connection resistance. [Explanation of symbols]

[0115] 1 electrolytic capacitor 10 Capacitor element 11 Electrode foil laminate 111 Electrode foil 20 electrode leads 30 Joint G Slit-shaped groove S1 Top surface of electrode foil laminate S2 Bottom surface of electrode foil laminate

Claims

1. A method for manufacturing an electrolytic capacitor having a capacitor element having a plurality of stacked electrode foils, comprising: an electrode foil laminate forming step of laminating a plurality of electrode foils to form an electrode foil laminate; an electrode lead arranging step of arranging an electrode lead on a part of a lower surface in a lamination direction of the electrode foil laminate; a groove forming step of forming a slit-shaped groove in the electrode foil laminate by irradiating a first laser beam onto a portion of an upper surface of the electrode foil laminate in the stacking direction, the portion being opposite to the electrode lead, along a first direction intersecting the stacking direction; and a joint forming process, after the groove forming process, in which a second laser beam is irradiated into the groove with an irradiation spot diameter that is equal to or smaller than a width of the groove on the upper surface of the electrode foil laminate, thereby joining the plurality of electrode foils to each other inside the groove and forming a joint that joins the plurality of electrode foils to the electrode lead.

2. The method for manufacturing an electrolytic capacitor according to claim 1 , further comprising, before the electrode foil laminate forming step, a surface roughening step of roughening a surface of each of the plurality of electrode foils.

3. 3. The method for manufacturing an electrolytic capacitor according to claim 1, further comprising, before the electrode foil laminate forming step, an oxide layer forming step of forming an oxide layer on a surface of each of the plurality of electrode foils.

4. 3. The method for manufacturing an electrolytic capacitor according to claim 1, wherein a ratio of a maximum depth of the groove from the upper surface of the electrode foil laminate to a thickness from the upper surface to the lower surface of the electrode foil laminate is 0.5 or more and 0.9 or less.

5. 3. The method for manufacturing an electrolytic capacitor according to claim 1, wherein a ratio of a length of the joint portion in the first direction to a length of the electrode foil laminate in the first direction, as viewed from the stacking direction, is equal to or greater than 0.8 and less than 1.

0.

6. the first laser beam is irradiated as continuous light, 3. The method for manufacturing an electrolytic capacitor according to claim 1, wherein the second laser light is pulsed light.

7. In the groove forming step, the plurality of electrode foils are melted by the first laser light to form molten metal pools, 3. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the joint forming step, the molten metal pool is re-melted by the second laser light.

8. Each of the plurality of electrode foils is an anode foil, 3. The method for manufacturing an electrolytic capacitor according to claim 1, wherein the capacitor element further comprises a cathode foil facing the anode foil, and a conductive polymer disposed between the anode foil and the cathode foil.

9. The method for manufacturing an electrolytic capacitor according to claim 1 or 2, wherein the capacitor element is impregnated with a liquid component.

10. a capacitor element having an electrode foil laminate in which a plurality of electrode foils are laminated; an electrode lead joined to a part of a lower surface in a stacking direction of the electrode foil laminate, the electrode foil laminate has joints that join the plurality of electrode foils to one another and to the electrode lead, the joint portion has a slit shape extending in a first direction intersecting the stacking direction on an upper surface of the electrode foil laminate in the stacking direction, and is formed from the upper surface to the lower surface, An electrolytic capacitor, wherein a ratio of a length from the upper surface to the lower surface of the joint portion to a width of the slit shape of the joint portion on the upper surface is 200 or more and 12,000 or less.

11. The electrolytic capacitor according to claim 10 , wherein each of the plurality of electrode foils has a roughened portion on a surface thereof.

12. 12. The electrolytic capacitor according to claim 10, wherein each of the plurality of electrode foils has an oxide layer on a surface thereof.

13. 12. The electrolytic capacitor according to claim 10, wherein a ratio of a length of the joint portion in the first direction to a length of the electrode foil laminate in the first direction, as viewed from the stacking direction, is equal to or greater than 0.8 and less than 1.

0.

14. Each of the plurality of electrode foils is an anode foil, 12. The electrolytic capacitor according to claim 10, wherein the capacitor element further comprises a cathode foil facing the anode foil, and a conductive polymer disposed between the anode foil and the cathode foil.

15. 12. The electrolytic capacitor according to claim 10, wherein the capacitor element is impregnated with a liquid component.

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