Manufacturing Method of Lead Terminal for Storage Device

Abstract

To provide a method for appropriately manufacturing a lead terminal for a power storage device having an electrode terminal made of a wire material mainly containing aluminum or copper, and a lead terminal manufactured by the method.SOLUTION: A manufacturing method for a lead terminal for a power storage device having an electrode terminal 2 made of a wire 100 mainly containing aluminum or copper, and a lead wire 3 connected to the electrode terminal via a welded portion 4, includes a first step of aligning a wire and a lead wire in a straight line and holding the wire and the lead wire in a state where a predetermined distance is maintained between an end face 100b of the wire on the lead wire side and an end face 3b of the lead wire on the wire side, a second step of irradiating an end face 100a of the wire on the lead wire side with a laser beam using a laser irradiator 400 to melt the end, and a third step of pushing one of the wire and the lead wire axially toward the other after a predetermined time has elapsed from the start of irradiation of the laser beam in the second step, to form a welded portion.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a lead terminal for a power storage device. In the method It relates thereto.

Background Art

[0002] Conventionally, lead terminals for power storage devices have been known. Lead terminals for power storage devices all include a metal electrode terminal and a lead wire. The lead wire is connected to the electrode terminal via a welded portion. For example, in a lead terminal for an electrolytic capacitor (a type of power storage device), the electrode terminal is connected to an electrode foil that forms a capacitor element (a component of the electrolytic capacitor), and the lead wire is connected to an electric circuit.

[0003] As a typical lead terminal, a lead terminal including an aluminum or copper electrode terminal is known. The welded portion of such a lead terminal has generally been formed by percussion arc welding (see, for example, Patent Document 1). This is because when forming the welded portion by other welding methods, such as brazing (a type of soldering), there is a risk of foreign matter mixing in, and when forming the welded portion by resistance welding (a type of pressure welding), there are drawbacks such as a relatively slow melting rate of the material to be welded. Among the welding methods considered at that time, percussion arc welding could achieve the highest yield.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] ​

[0006] The present invention has been made to address the above-described problems. That is, one of the objects of the present invention is to appropriately manufacture a lead terminal for a power storage device including an electrode terminal made of a wire mainly containing aluminum or copper. the method and to provide a manufacturing method therefor.

[0007] A method for manufacturing a lead terminal of the present invention is a method for manufacturing a lead terminal for a power storage device including an electrode terminal (2) made of a wire (100) mainly containing aluminum or copper and a lead wire (3) connected to the electrode terminal via a welded portion (4). The method for manufacturing the lead terminal is as follows. A first step of aligning the wire (100) and the lead wire (3) linearly and holding the wire and the lead wire in a state where the distance between the end face (100b) on the lead wire side of the wire and the end face (3b) on the wire side of the lead wire is maintained at a predetermined distance; A second step of irradiating a laser beam onto the end portion (100a) on the lead wire side of the wire (100) with a laser irradiator (400) to melt the end portion; A third step of forming the welded portion (4) by pushing one of the wire (100) and the lead wire (3) axially toward the other after a predetermined time has elapsed from the start of irradiation of the laser beam in the second step. and includes.

[0009] According to the present invention, a manufacturing method for appropriately manufacturing a lead terminal for a power storage device including an electrode terminal made of a wire mainly containing aluminum or copper can be provided. the method and can be provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 2D

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Figure 5A

Figure 5B

Figure 5C

Figure 6

Figure 7A

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Figure 8A

Figure 8B

Figure 8C

[0011] Hereinafter, with reference to the drawings, a method for manufacturing a lead terminal for a power storage device according to an embodiment of the present invention will be described by taking a lead terminal for an electrolytic capacitor, which is a type of power storage device, as an example. First, the configuration of the lead terminal will be described. As shown in FIG. 1, the lead terminal 1 includes an aluminum electrode terminal 2 and a lead wire 3 made of a CP wire.

[0012] The electrode terminal 2 is formed by pressing a part in the axial direction of a wire rod mainly containing aluminum (hereinafter simply referred to as an "aluminum wire") in the radial direction, and has a rod-shaped portion 21 on one end side and a rolled portion 22 on the other end side. The rod-shaped portion 21 is a remaining portion that has not been pressed (that is, the other part in the axial direction of the aluminum wire). The rolled portion 22 is formed by pressing the above-mentioned part of the aluminum wire into a flat plate shape and cutting its outer periphery along the thickness direction. The axis of the rolled portion 22 (a line passing through the center in the width direction and the thickness direction) is coaxial with the axis of the rod-shaped portion 21. However, a configuration in which the rolled portion 22 is eccentric with respect to the rod-shaped portion 21 may be adopted. This aluminum wire has been subjected to a well-known anodic oxidation treatment in advance, and an oxide film is formed on its outer peripheral surface. The diameter of the aluminum wire is about 2 mm. Note that the electrode terminal 2 may be formed using an aluminum wire that has not been subjected to anodic oxidation treatment.

[0013] The lead wire 3 is connected to one end of the rod-shaped portion 21 via a welded portion 4. The diameter of the lead wire 3 is about 0.8 mm, which is smaller than that of the rod-shaped portion 21. The axis of the lead wire 3 is coaxial with the axis of the rod-shaped portion 21. In the present embodiment, as the CP wire constituting the lead wire 3, a metal wire in which the outer peripheral surface of an iron wire is coated with a copper plating layer and the copper plating layer is further coated with a tin plating layer is used. The thicknesses of both the copper plating layer and the tin plating layer are on the order of several tens of μm. However, instead of the tin plating layer, a CP wire coated with a nickel plating layer, a silver plating layer, or a lead-free solder plating layer may be used. Alternatively, as the CP wire constituting the lead wire 3, a metal wire in which the outer peripheral surface of an iron wire is coated only with a copper plating layer may be used.

[0014] Next, a method for manufacturing the lead terminal 1 will be described with reference to FIGS. 2A to 2D. First, a long aluminum wire (strictly speaking, an aluminum wire subjected to anodizing treatment), which is the material of the electrode terminal 2, is cut to a predetermined length to form a wire rod 100. Also, a long CP wire, which is the material of the lead wire 3, is cut to a predetermined length to form the lead wire 3.

[0015] Subsequently, as shown in FIG. 2A, the wire rod 100 is held by a jig 200, and the lead wire 3 is held by a jig 300. The wire rod 100 and the lead wire 3 are linearly aligned so that their axes are coaxial, and the distance between the end face 100b of one end 100a of the wire rod 100 and the end face 3b of the other end 3a of the lead wire 3 is maintained at a predetermined distance (2 mm in this embodiment) (first step).

[0016] Next, a laser beam is irradiated from a direction orthogonal to the axis of the wire rod 100 (hereinafter, also simply referred to as the "orthogonal direction") to a predetermined position P of the end 100a of the wire rod 100 by a laser irradiation machine 400. The position P is located at a position separated by a predetermined distance L (0.10 mm in this embodiment) from the end face 100b on the outer peripheral surface 100c of the end 100a. When the wire rod 100 is viewed in plan from the irradiation direction of the laser beam, the position P is located at the center in the radial direction of the wire rod 100. That is, the laser beam is irradiated toward the axis of the wire rod 100. The irradiation machine 400 is a single-mode infrared laser (IR laser) having an output of 700 W. The laser beam is irradiated for 0.030 s with a spot diameter of 30 μm. When the laser beam is irradiated to the position P of the wire rod 100 by the irradiation machine 400, as shown in FIG. 2B, the end 100a is melted throughout to form a molten pool A (second step). Note that the distance L may be appropriately changed according to the output of the irradiation machine 400, the spot diameter, the irradiation time, and the like.

[0017] The jig 300 is provided with a pushing mechanism (not shown). The pushing mechanism is configured to apply an external force in a predetermined direction. In this embodiment, the pushing mechanism applies an external force to the lead wire 3, pushing the lead wire 3 axially toward the wire 100, immediately after the laser beam irradiation by the irradiator 400 is completed (in other words, after the irradiation time has elapsed since the start of laser beam irradiation). This external force is applied so that the lead wire 3 moves a predetermined distance at a predetermined speed (200 mm / s in this embodiment). As a result, the end 3 a of the lead wire 3 is pushed into the molten pool A of the wire 100, as shown in FIG. 2C. Then, a portion of the molten pool A spreads to cover the outer peripheral surface 3 c of the end 3 a of the lead wire 3. Thereafter, when the molten pool A (or, if the end 3a is partially melted, the molten pool A and the molten portion of the end 3a) solidifies, a conical (strictly speaking, approximately truncated conical) weld 4 is formed between the wire 100 and the lead wire 3, as shown in Figure 2D, and the wire 100 and the lead wire 3 are connected (third step).

[0018] Thereafter, the other end of the wire 100 is pressed to form the rolled portion 22 shown in Fig. 1, and is subjected to well-known anodizing and resin coating processes as necessary, thereby producing the lead terminal 1. Note that, as a result of a strength test, it was confirmed that the strength of the lead terminal 1 produced by laser welding was equivalent to that of a lead terminal produced by percussion arc welding.

[0019] The manufacturing method for a lead terminal according to the present embodiment enables more appropriate manufacturing of lead terminals than conventional manufacturing methods using percussion arc welding (hereinafter simply referred to as "arc welding"). The following specific explanations are provided below. Conventional arc welding methods have the following problems. The first problem is poor reproducibility of the weld shape. In other words, arc welding has a problem in that the amount of heat input tends to vary from workpiece to workpiece depending on the environmental conditions at the time of arc generation (type and flow rate of shielding gas, shape and condition of each end face of the wire and lead wire). As a result, there is a problem in that the shape of the lead terminal tends to vary. FIGS. 5A to 5C are partially enlarged views of a defective lead terminal 11 manufactured using arc welding. The lead terminal 11 includes an aluminum electrode terminal 12 and a lead wire 13 made of a CP wire connected to the electrode terminal 12 via a weld 14. In Fig. 5A, a portion 14a of the weld 14 covers the outer peripheral surface of the lead wire 13, while the other portion of the weld 14 does not, resulting in an irregular shape (so-called uneven weld). In Fig. 5B, a protrusion (so-called weld thorn) 14b large enough to be visible to the naked eye is generated from the weld 14. In Fig. 5C, a portion 14c of the weld 14 in the circumferential direction protrudes radially, causing a local increase in the diameter of the weld 14 (so-called protrusion). The low reproducibility of the weld shape exemplified in the lead terminal 11 of Figs. 5A to 5C has been a factor preventing improvement in yield.

[0020] The second problem is the deposition of dissimilar metals on the workpiece (especially the electrode terminals). In arc welding, an arc discharge generates an arc between the wire and the lead wire, melting the ends of both wires and lead wires, generating spatter from both the wire and lead wire. For example, if the lead wire is a copper-plated wire coated with copper and tin, the spatter generated from the lead wire contains copper and tin. Therefore, when spatter containing copper and tin generated from the lead wire adheres to the aluminum wire, dissimilar metals are deposited on the workpiece (specifically, the part that will become the electrode terminal after the product is completed). When capacitor elements (components of electrolytic capacitors) are manufactured using lead terminals with dissimilar metals attached to their electrode terminals, the dissimilar metals may react with the electrolyte inside the capacitor element, potentially resulting in a deterioration in quality characteristics. This problem is unavoidable as long as the lead wire contains materials other than aluminum. The deposition of dissimilar metals on the workpiece was another factor hindering yield improvement.

[0021] The third problem is the limitations on improving workpiece manufacturing speed. In arc welding, an arc is generated by first bringing the wire and lead wire into contact with each other and then separating them. The tips of the wire and lead wire melt, and then the two are brought into contact again (strictly speaking, one is pushed into the other). This requires multiple reciprocating motions for each workpiece, complicating the manufacturing process. Furthermore, there are limitations to the performance of actuators capable of performing this series of reciprocating motions, making it difficult to control the actuators at high speed. These issues have hindered efforts to increase workpiece manufacturing speed.

[0022] In contrast, in this embodiment, laser welding is adopted as the welding method. Therefore, the shape of the welded portion 4 can be controlled relatively easily (in other words, once the environmental conditions during laser beam irradiation are determined, subsequent adjustments are basically unnecessary). As a result, the reproducibility of the shape of the welded portion can be significantly improved. Further, in laser welding, since only the wire 100 is irradiated with the laser beam, even if spatter occurs from the wire 100 due to laser welding, a situation where a dissimilar metal adheres to the electrode terminal 2 cannot occur (adhesion of spatter generated from the wire 100 to the lead wire 3 is not particularly regarded as a problem). In addition, in laser welding, the welded portion 4 is formed by pushing the end portion 3a of the lead wire 3 into the molten pool A of the wire 100. Therefore, the welding process can be carried out by simply moving the lead wire 3 in one direction once for one workpiece, and the manufacturing process can be simplified. Also, since an actuator that can realize such a simple movement is easily available, by introducing an actuator that operates at high speed, the time required for the operation of the actuator can be significantly shortened. From the above, by adopting laser welding as the welding method, the above three problems related to arc welding can be solved, and the yield and manufacturing speed of the lead terminal 1 can be improved.

[0023] Here, even when laser welding is used as the welding method, in the following manufacturing method, that is, "manufacturing method M in which while irradiating the wire 100 with a laser beam in a state where the end face 100b of the wire 100 and the end face 3b of the lead wire 3 are abutted (contacted), one of the wire 100 and the lead wire 3 is pushed axially toward the other", the welded portion 4 may not be appropriately formed. This will be specifically described with reference to FIG. 3. FIG. 3 shows a partially enlarged view of the lead terminal 1 when the welded portion 4 is formed by the manufacturing method M. In this example, the laser beam is irradiated from the orthogonal direction. As shown in FIG. 3, a crater-shaped indentation d is formed in the welded portion 4. The indentation d is a depression formed due to the laser beam continuously irradiating one location on the outer peripheral surface 100c of the wire 100. The height hd of the welded portion 4 at the portion where the indentation d is formed is larger than the height h of the welded portion 4 at the portion where the indentation d is not formed, and it has been found that the ratio (hd / h) tends to be about 1.5 to 2 times. Since the welded portion 4 with such an indentation d formed deviates greatly from the general standard of the welded portion 4, it becomes a factor hindering the improvement of the yield. Further, when an electrolytic capacitor is manufactured using the lead terminal 1 having the indentation d in the welded portion 4, a gap may occur between the resin sealing body and the lead terminal 1, and the electrolytic solution (the electrolytic solution held by the capacitor element) may leak from the gap. In that case, the quality characteristics of the electrolytic capacitor may deteriorate.

[0024] Therefore, in the present embodiment, the irradiation of the laser beam is started while maintaining the distance between the end face 100b of the wire 100 and the end face 3b of the lead wire 3 at a predetermined distance, and after a lapse of a predetermined time T from the start of the irradiation, one of the wire 100 and the lead wire 3 is pushed axially toward the other. According to this configuration, it becomes difficult for the indentation d to occur in the welded portion 4. As a result, the yield of the lead terminal 1 can be improved and the deterioration of the quality characteristics of the electrolytic capacitor can be suppressed.

[0025] As described above, according to the method for manufacturing a lead terminal according to the present embodiment, it is possible to appropriately manufacture a lead terminal including an electrode terminal made of a wire mainly containing aluminum. Note that the lead terminal 1 is not limited to an electrolytic capacitor and may be used as a component of other power storage devices. Other power storage devices include, for example, a lithium ion capacitor, an electric double layer capacitor (EDLC), or a lithium ion battery. Even when the lead terminal 1 is used as a component of other power storage devices, the same effect can be obtained.

[0026] The inventors of the present application verified the generation rate of the indentation d while changing the predetermined time T (the time from the start of the irradiation of the laser beam to the time when the lead wire 3 is pushed into the wire 100). As a result, when the laser beam is irradiated from the orthogonal direction, when 0 < T < irradiation time, although the generation rate of the indentation d can be reduced compared to when T = 0, it was found that the generation rate of the indentation d is higher than when T = irradiation time. Further, when T > irradiation time, although the generation rate of the indentation d could be suppressed to the same level as when T = irradiation time, since the temperature of the molten pool A decreases by the amount of delay in the timing of pushing the lead wire 3 toward the wire 100, it was found that there is a possibility that the wire 100 and the lead wire 3 cannot be appropriately connected (that is, the strength of the lead terminal 1 decreases). Therefore, in the present embodiment, when the laser beam is irradiated from the orthogonal direction, the lead wire 3 is pushed toward the wire 100 immediately after the irradiation of the laser beam ends (that is, the predetermined time T = irradiation time). According to this configuration, it is possible to further reduce the generation rate of the indentation d in the welded portion 4 while ensuring the strength of the lead terminal 1.

[0027] Note that when the laser beam is irradiated from the orthogonal direction, the position adjustment of the irradiator 400 is performed by making the axis of the irradiation port orthogonal to the axis of the wire 100. Therefore, the position adjustment of the irradiator 400 can be easily performed as compared with a configuration in which the laser beam is irradiated so as to intersect obliquely with the axis of the wire 100.

[0028] Furthermore, in the present embodiment, an infrared laser is used in the irradiator 400. Therefore, the cost of the manufacturing equipment for the lead terminal 1 can be reduced as compared with the case where a short-wavelength laser (typically, a blue laser or a green laser) is used in the irradiator 400. However, since the absorption rate of aluminum is the same in the entire wavelength band of infrared rays and visible light, from the viewpoint other than the manufacturing cost, the same effects as those of the present embodiment can be achieved even when a short-wavelength laser is used. Note that the type of laser (for example, a fiber laser or a semiconductor laser) is not particularly limited.

[0029] The laser beam is not limited to the position P of the wire 100, and may be irradiated, for example, linearly or elliptically in a predetermined range on the outer peripheral surface 100c of the end portion 100a. Further, during the irradiation of the laser beam, the wire 100 may be rotated at a predetermined speed around the axis.

[0030] (Modification 1) Next, a method for manufacturing a lead terminal for a power storage device according to Modification 1 of the present invention will be described with reference to FIG. 4. The same reference numerals are given to the same components as those in the embodiment, and the detailed description thereof will be omitted. This also applies to other modifications. As shown in FIG. 4, the manufacturing method of Modification 1 is different from the manufacturing method of the embodiment in that the irradiation direction of the laser beam is oblique with respect to the axis of the wire 100. Specifically, in the present modification, the irradiator 400 irradiates a laser beam from a direction intersecting the axis of the wire 100 at 45° to the center C of the end face 100b of the wire 100. The pushing mechanism applies an external force to the lead wire 3 to push the lead wire 3 axially toward the wire 100 immediately after the irradiation of the laser beam ends (that is, a predetermined time T = irradiation time). The spot diameter and the irradiation time may be the same as or different from those in the embodiment.

[0031] Even with this configuration, the same operational effects as those of the embodiment can be achieved. In particular, in this modified example, the laser beam is irradiated onto the end face 100b (i.e., the portion that becomes the inside of the melting pool A) of the wire 100 instead of the outer peripheral surface 100c. For this reason, indentations d are not formed on the welded portion 4, and the yield of the lead terminal 1 can be more suitably improved, and a further reduction in the quality characteristics of the power storage device can be suppressed.

[0032] Note that as long as the laser beam is irradiated onto the end face 100b of the wire 100, the irradiation direction of the laser beam is not limited to the direction intersecting the axis of the wire 100 at 45°. Also, the irradiation position of the laser beam may be eccentric from the center C of the end face 100b, or may be irradiated, for example, linearly or circularly within a predetermined range on the end face 100b. Furthermore, since indentations d are not formed on the welded portion 4 in this modified example, the timing at which the lead wire 3 is pushed toward the wire 100 may be earlier than the time when the irradiation of the laser beam ends (typically, it may be several tens of ms earlier than the end of irradiation). That is, the predetermined time T can be set to any value satisfying 0 < T ≤ irradiation time.

[0033] (Modified Example 2) Next, a method for manufacturing a lead terminal for a power storage device according to Modified Example 2 of the present invention will be described. The manufacturing method of Modified Example 2 is different from the manufacturing methods of the embodiment and Modified Example 1 in that a wire mainly containing copper is used as the wire 100 constituting the electrode terminal 2, and a short-wavelength laser is used as the irradiation machine 400 instead of an infrared laser.

[0034] This wire 100 is previously subjected to a well-known anodic oxidation treatment, and an oxide film is formed on its outer peripheral surface. The diameter of the wire 100 and the method of forming the electrode terminal 2 are the same as those in the embodiment. Note that the electrode terminal 2 may be formed using a wire that has not been subjected to anodic oxidation treatment.

[0035] The lead terminal 1 can basically be manufactured by the manufacturing method described in the embodiment or Modification 1. However, in the second step, a short-wavelength laser is used as the irradiator 400. The short-wavelength laser is a multi-mode blue laser having an output of 2 kW. The laser beam is irradiated for 70 μs with a spot diameter of 600 μm. When the laser beam is irradiated to the position P of the wire 100 by the blue laser, as in the embodiment, the end portion 100a is melted throughout to form a melting pool A. Note that a green laser may be used instead of the blue laser as the short-wavelength laser. In this case, the spot diameter and the irradiation time can be appropriately adjusted according to the output of the green laser.

[0036] Here, when a wire mainly containing copper is used as the wire 100, even if a predetermined time T (the time from the start of irradiation of the laser beam until the lead wire 3 is pushed toward the wire 100) satisfies 0 < T < the irradiation time, the indentation d does not occur. Therefore, in this modification, the predetermined time T does not necessarily have to satisfy T = the irradiation time. The predetermined time T can be appropriately set based on the wire diameter ratio of the lead wire 3 to the wire 100, the output of the short-wavelength laser, the spot diameter, the irradiation time, and the like.

[0037] As described above, according to the manufacturing method of the lead terminal for the power storage device according to Modification 2, the three problems related to arc welding described in the embodiment can be solved, and the yield and the manufacturing speed of the lead terminal 1 can be improved. That is, it becomes possible to appropriately manufacture the lead terminal 1 including the electrode terminal made of a wire mainly containing copper.

[0038] In addition, when manufacturing the lead terminal 1 by the same manufacturing method as in the embodiment, the position adjustment of the short-wavelength laser can be easily performed as compared with the configuration in which the laser beam is irradiated so as to intersect obliquely with the axis of the wire 100.

[0039] Furthermore, generally, the absorption rate of a laser beam with respect to a metal varies depending on the wavelength of the laser beam and the type of the metal. However, the absorption rate with respect to copper is significantly higher for a laser beam of a short-wavelength laser than for a laser beam of an infrared laser. Therefore, when the wire 100 mainly contains copper, the end portion 100a of the wire 100 can be appropriately melted by using a short-wavelength laser.

[0040] (Modification Example 3) Next, regarding the lead terminal for a power storage device and the method for manufacturing the same according to Modification Example 3 of the present invention, the lead terminal for an electrolytic capacitor will be taken as an example and described with reference to FIGS. 6 to 8C. The lead terminal of Modification Example 3 is different from the lead terminals 1 of the embodiment, Modification Example 1, and Modification Example 2 in that the wire diameter ratio of the lead wire with respect to the wire (described later) is relatively large.

[0041] As shown in FIG. 6, the lead terminal 101 according to this modification includes an aluminum electrode terminal 102 and a lead wire 103 made of a CP wire. The electrode terminal 102 has a rod-shaped portion 121 on one end side and a rolled portion 122 on the other end side. The lead wire 103 is connected to one end of the rod-shaped portion 121 via a welded portion 104. The diameter of the wire (aluminum wire), that is, the diameter of the rod-shaped portion 121, is, for example, 1.2 mm, and the diameter of the lead wire 103 is, for example, 1.0 mm. Hereinafter, the ratio of the diameter of the lead wire to the diameter of the wire (that is, the diameter of the rod-shaped portion) is referred to as the "wire diameter ratio of the lead wire with respect to the wire" or the "wire diameter ratio of the lead terminal". The wire diameter ratio is calculated as an integer value by rounding off the decimal part. The upper limit value of the wire diameter ratio is 100%. In the above example, the wire diameter ratio of the lead terminal 101 is 1.0 / 1.2 = 83%, which is larger than the wire diameter ratio of 40% (= 0.8 / 2) of the lead terminal 1 according to the embodiment, Modification Example 1, and Modification Example 2. The lead terminal according to this modification is characterized in that the wire diameter ratio is in the range of 83% or more and 100% or less. That is, as long as the wire diameter ratio of the lead terminal 101 is within this range, the diameters of the wire and the lead wire 103 are not limited to the above values.

[0042] The lead terminal 101 can be manufactured by using a wire material and a lead wire 103 having a wire diameter ratio of 83% or more and 100% or less in the first step of the embodiment. Further, the lead terminal 1 can also be manufactured by the manufacturing method of Modification 1.

[0043] FIG. 7A is a view showing the welded portion 104 of the lead terminal 101 and its vicinity. The diameter of the rod-shaped portion 121 is 1.2 mm, and the diameter of the lead wire 103 is 1.0 mm. FIG. 7B is a schematic diagram of the X-ray image of FIG. 7A. FIG. 7C is a schematic diagram of an EPMA (Electron Probe Micro Analyzer) image in a cross section including the axis of the sample S. The sample S is manufactured by laser welding (strictly speaking, the manufacturing method according to the embodiment) using a material having the same dimensions as the lead terminal 101. On the other hand, FIG. 8A is a view showing the welded portion 114 of the lead terminal 111 as a comparative example manufactured by arc welding and its vicinity. The diameter of the rod-shaped portion 131 is 1.2 mm, and the diameter of the lead wire 113 is 1.0 mm. FIG. 8B is a schematic diagram of the X-ray image of FIG. 8A. FIG. 8C is a schematic diagram of an EPMA image in a cross section including the axis of the sample Sc. The sample Sc is manufactured by arc welding using a material having the same dimensions as the lead terminal 111.

[0044] Comparing FIG. 7A and FIG. 8A, in FIG. 7A, the surface of the welded portion 104 of the lead terminal 101 is relatively smooth, whereas in FIG. 8A, a large number of irregularities are formed on the surface of the welded portion 114 of the lead terminal 111. Further, although the welded portion 104 has a slightly swollen portion partially, its shape is substantially symmetric around the axis. In contrast, the welded portion 114 protrudes significantly in the radial direction, and its shape is asymmetric around the axis. Generally, when an electrolytic capacitor is manufactured using a lead terminal whose welded portion shape is asymmetric around the axis, a gap may be generated between the sealing body and the lead terminal, and the electrolytic solution may leak from the gap. In that case, the quality characteristics of the electrolytic capacitor may deteriorate.

[0045] Therefore, in this modified example, an upper limit value dmu is set for the maximum diameter dm of the welded portion, and dm <dmuを満たすリード端子のみを良品としている。上限値dmuは電解液の漏出を十分に抑制できる程度の値であり、例えば、「線材の直径+0.100mm」に設定され得る(dmu=線材の直径+0.100mm)。図7A及び図8Aの例では、溶接部104の最大径dmは上限値dmu未満であるのに対し、溶接部114の最大径dmは上限値dmuを大きく上回っている。このため、線径比が83%のリード端子を用いて電解コンデンサを製造する場合、レーザー溶接では電解液の漏出を適切に抑制できるが、アーク溶接では電解液の漏出に起因して電解コンデンサの品質特性低下を招く可能性がある。

[0046] The reason why the shape of the welded portion of lead terminal 101 can be more precisely controlled than that of lead terminal 111 is believed to be due to the difference in the welding method. That is, with laser welding, the environmental conditions during irradiation are set in advance to match the wire diameter ratio, so that the shape of welded portion 104 can be appropriately controlled regardless of the value of the wire diameter ratio. In contrast, with arc welding, as the wire diameter ratio increases (in other words, as the difference in wire diameter between the wire material and lead wire 113 decreases), it becomes more difficult for lead wire 113 made of CP wire to melt. For this reason, when the tip of lead wire 113, which is not fully melted, is forcefully inserted into the molten pool formed at the end of the wire material, the molten pool is pushed out radially while mixing with the small amount of molten metal at the tip of lead wire 113, resulting in welded portion 114 having a shape that protrudes significantly radially.

[0047] Another factor that degrades the quality characteristics of an electrolytic capacitor is the bending strength of the welded part of the lead terminal. The bending strength is an index representing the strength of the welded part. When the operation of bending the lead wire 90° in one direction with respect to the wire material and then returning it, and then bending it 90° in the other direction (the direction opposite to the one side) and returning it is defined as one cycle, it is represented by the number of cycles n until the lead wire breaks. For example, when the lead wire breaks in 2 cycles, n = 2. The larger the number of cycles n, the higher the strength of the welded part. In addition, when the lead wire breaks when it is bent 90° in one direction with respect to the wire material and then returned, the number of cycles n is defined as "the number of cycles so far + 0.5". When manufacturing an electrolytic capacitor using lead terminals with low bending strength, the lead terminals may break due to vibration or mild impact during use. In that case, the quality characteristics of the electrolytic capacitor may deteriorate.

[0048] Therefore, in this modification example, a lower limit value nl is set for the number of cycles n, and only lead terminals that satisfy n ≥ nl are regarded as acceptable products. The lower limit value nl is a value that can sufficiently suppress the breakage of the lead terminal caused by vibration or mild impact. In the dimensional specifications of this modification example, for example, it can be set to 1.0 cycle. As a result of performing a bending strength test on the lead terminals 101 and 111, the number of cycles n of the lead terminal 101 was 1.5 cycles, which satisfied n ≥ nl, while the number of cycles n of the lead terminal 111 was 0.5 cycle, which was n < nl. For this reason, when manufacturing an electrolytic capacitor using lead terminals with a wire diameter ratio of 83%, laser welding can appropriately suppress the breakage of the lead terminals, but arc welding may cause a deterioration in the quality characteristics of the electrolytic capacitor due to the breakage of the lead terminals.

[0049] The reason why the lead terminal 101 has a higher bending strength than the lead terminal 111 is considered to be due to the difference in the composition between the welding part 104 and the welding part 114. Hereinafter, it will be described with reference to FIGS. 7B, 7C, 8B, and 8C. In FIG. 7B, the portion p1 corresponds to the rod-shaped portion 121, the upper ends of the portions p2 and p3 correspond to the welding part 104, and the remaining portion of the portion p3 corresponds to the lead wire 103. Most of the welding part 104 is occupied by the portion p2. The shading of the colors of the portions p1 to p3 is due to the X-ray transmission amount. The portion p1 shows a color derived from the main component (aluminum) of the wire, and the portion p3 shows a color derived from the main component (iron) of the lead wire 103. Since the portion p2 shows an intermediate color between the two, it is considered that in the portion p2, aluminum and iron (strictly speaking, in addition to iron, trace amounts of copper and tin) are melted and solidified.

[0050] This is also supported by FIG. 7C. That is, in FIG. 7C, the portion p4 corresponds to the rod-shaped portion 121, the upper ends of the portions p5 and p6 correspond to the welding part 104, and the remaining portion of the portion p6 corresponds to the lead wire 103. Most of the welding part 104 is occupied by the portion p5. The shading of the colors of the portions p4 to p6 is due to the type and concentration of the elements. The portion p4 shows a color derived from the main component (aluminum) of the wire, and the portion p6 shows a color derived from the main component (iron) of the lead wire 103. The portion p5 shows an intermediate color between the two, similar to the portion p2. From the above, it can be seen that in the welding part 104, most of it has a composition in which aluminum and iron (strictly speaking, in addition to iron, trace amounts of copper and tin) are melted, mixed, and then solidified. Hereinafter, such a composition will be referred to as a "mixed composition".

[0051] On the one hand, in Fig. 8B, the part of the portion p11 excluding the lower end corresponds to the rod-shaped portion 131, the lower end of the portion p11, the portion p12, and the upper end of the portion p13 (in other words, the portion of the portion p13 covered by the portions p11 and p12) correspond to the welding portion 114, and the remaining part of the portion p13 corresponds to the lead wire 113. Most of the welding portion 114 is occupied by the portion p13. The portion p11 shows a color derived from the main component (aluminum) of the wire, and the portion p13 shows a color derived from the main component (iron) of the lead wire 103. Since the portion p12 shows an intermediate color between the two, it is considered that in the portion p12, aluminum and iron (strictly speaking, in addition to iron, trace amounts of copper and tin) are melted and solidified.

[0052] This is also supported by Fig. 8C. That is, in Fig. 8C, the part of the portion p14 excluding the lower end corresponds to the rod-shaped portion 131, the lower end of the portion p14, the portion p15, and the upper end of the portion p16 (in other words, the portion of the portion p16 covered by the portions p14 and p15) correspond to the welding portion 114, and the remaining part of the portion p16 corresponds to the lead wire 113. Most of the welding portion 114 is occupied by the portion p16. The portion p14 shows a color derived from the main component (aluminum) of the wire, and the portion p16 shows a color derived from the main component (iron) of the lead wire 113. The portion p15 shows an intermediate color between the two, similar to the portion p12. From the above, it can be seen that in the welding portion 114, most of it has an iron composition, and at the boundary between different metals (iron and aluminum) is formed between the portions p13 and p11 (or between the portions p16 and p14) within the welding portion 114. In addition, it can be seen that the mixed composition is formed only in the outer peripheral portion within the welding portion 114.

[0053] As described above, the welded portion 104 is mostly composed of a mixture of aluminum and iron. Therefore, when a bending load is applied to the lead terminal 101, the welded portion 104 acts as a buffer, preventing stress from concentrating at the welded portion 104, resulting in increased bending strength. In contrast, the welded portion 114 is mostly composed of iron, and a boundary between dissimilar metals (iron and aluminum) is formed within the welded portion 114. Therefore, when a bending load is applied to the lead terminal 111, stress is concentrated at the welded portion 114 due to the difference in physical properties (typically, hardness and bendability) between iron and aluminum. In particular, in the examples of FIGS. 8A to 8C , the wire diameter ratio is relatively large (in other words, the difference in wire diameter between the wire material and the lead wire 113 is small), which increases the area of the boundary between iron and aluminum, resulting in correspondingly large stress concentrations. As a result, the bending strength is likely to be reduced.

[0054] In order to verify the superiority of laser welding over arc welding in terms of wire diameter ratio, the inventors of the present application manufactured seven lead terminal samples (Samples 1 to 7) with different wire diameter ratios by laser welding and arc welding, respectively, and conducted tests to investigate their quality. Table 1 below shows the test results for Samples 1 to 7 of lead terminals in which the wire material is an aluminum wire and the lead wire is a CP wire. [Table 1]

[0055] In this test, the maximum diameter dm of the weld is dm <dmuを満たし、且つ、折り曲げ強度試験のサイクル数nがn≧nlを満たす場合にリード端子の品質が良好(○)であると評価し、dm≧dmu、又は、n<nlである場合にリード端子の品質が不良(×)であると評価した。上限値dmuは、線径比に関わらず「線材の直径+0.100mm」である。一方、下限値nlは、リード端子の寸法規格毎に所定の値に設定されている。例えば、線径比が33%の場合はnl=1.5、線径比が40%の場合はnl=2.0、線径比が53%の場合はnl=2.0、線径比が57%の場合はnl=1.5、線径比が67%の場合はnl=1.0、線径比が83%の場合はnl=1.0、線径比が100%の場合はnl=1.0にそれぞれ設定され得る。なお、リード端子の寸法規格に応じて異なる種類のCP線(例えば、銅めっき層の厚みが異なるCP線)が用いられてもよい。

[0056] With laser welding, the quality is good for all samples 1 to 7. In contrast, with arc welding, the quality is good for samples 1 to 5, but the quality is poor for samples 6 and 7.

[0057] The good quality of the laser-welded lead terminals for all Samples 1 to 7 is believed to be due to the following two reasons. The first reason is that with laser welding, the environmental conditions during irradiation are set in advance to match the wire diameter ratio, making it possible to appropriately control the shape of the weld regardless of the wire diameter ratio. The second reason is that with laser welding, most of the weld is of mixed composition, making it difficult for stress to concentrate on the weld, and achieving high bending strength.

[0058] In contrast, the poor quality of the arc-welded lead terminals for Samples 6 and 7 is believed to be due to the following two reasons. First, in arc welding, as the wire diameter ratio increases, it becomes more difficult for the lead wire made of CP wire to melt. Therefore, in lead terminals with a wire diameter ratio of 83% or more, the tip of the insufficiently molten lead wire is thrust forcefully into the molten pool formed at the end of the wire, causing the weld to protrude significantly in the radial direction. Second, in arc-welded lead terminals with a wire diameter ratio of 83% or more, most of the weld is made of iron, and in lead terminals with a wire diameter ratio of 83% or more, the area of the boundary between dissimilar metals (iron and aluminum) in the weld increases. Therefore, when a bending load is applied to the lead terminal, large stress tends to concentrate in the weld, reducing the bending strength of the lead terminal.

[0059] The good quality of the arc-welded lead terminals for Samples 1 to 5 is believed to be due to the following two reasons. First, in lead terminals with a wire diameter ratio of 67% or less, the lead wire made of CP wire melts sufficiently even when arc-welded, making it difficult for the welded portion to protrude significantly in the radial direction even when the tip of the lead wire is forcefully inserted into the molten pool formed at the end of the wire. Second, in lead terminals with a wire diameter ratio of 67% or less, the area of the boundary between dissimilar metals in the welded portion is relatively small, so stress does not concentrate significantly in the welded portion even when a bending load is applied to the lead terminal.

[0060] According to Table 1, lead terminals related to laser welding can ensure their quality regardless of the wire diameter ratio. However, in this modification example, lead terminals with a wire diameter ratio of 83% or more and 100% or less are the subject of the invention. This is because, with the development of the automotive industry, computer industry, etc. in recent years, it is expected that the applications of electrolytic capacitors will become increasingly diverse in the future. As a result, as one of the lead terminals with various dimensional specifications, the development of lead terminals with a relatively large wire diameter ratio is required. Most of the conventional lead terminals were manufactured by arc welding. As is clear from Table 1, it was difficult to ensure the quality in arc welding when the wire diameter ratio was relatively large. In contrast, since the lead terminals according to this modification example are manufactured by laser welding, the quality of lead terminals with a wire diameter ratio (i.e., 83% to 100%) that could not be ensured in arc welding can be appropriately ensured.

[0061] In addition, since the wire diameter ratio is large, when the diameter of the wire 100 is the same as that of the conventional one, a lead wire thicker than the conventional one can be used for the lead wire 103. When the diameter of the lead wire 103 increases, the thickness of the copper plating layer also increases accordingly. Since the conductivity of the lead wire 103 is mainly borne by copper, according to this configuration, the electrical resistance of the lead terminal 101 can be reduced, and the electrical characteristics of the electrolytic capacitor can be improved.

[0062] Also, the lead terminal 101 may be manufactured by the manufacturing method according to Modification Example 2. That is, a wire mainly containing copper may be used as the wire 100 instead of an aluminum wire. Even in this case, the same results as in Table 1 were obtained.

[0063] Furthermore, instead of the CP wire, a metal wire mainly containing copper (hereinafter, also referred to as "copper lead wire") may be used as the lead wire 103. Here, the "metal wire mainly containing copper" means a metal wire whose outer peripheral surface of the copper wire is coated with a tin plating layer or a silver plating layer. In this case, the lead terminal 101 includes two types: "a lead terminal in which the wire material 100 is an aluminum wire and the lead wire 103 is a copper lead wire" and "a lead terminal in which the wire material 100 is a wire material mainly containing copper and the lead wire 103 is a copper lead wire". In either type of lead terminal 101, the same results as in Table 1 were obtained.

[0064] As described above, according to the manufacturing method of the lead terminal 101 and the lead terminal 101 according to Modification 3, it is possible to provide a manufacturing method for appropriately manufacturing the lead terminal 101 including the electrode terminal 102 made of the wire material 100 mainly containing aluminum or copper, and the lead terminal 101 manufactured by the manufacturing method. Note that the lead terminal 101 is not limited to the electrolytic capacitor and may be used as a component of other power storage devices. Other power storage devices include, for example, lithium-ion capacitors, electric double-layer capacitors, or lithium-ion batteries. Even when the lead terminal 101 is used as a component of other power storage devices, the same effects can be achieved.

[0065] Although the embodiments and Modifications 1 to 3 have been described above, the present invention is not limited to the above embodiments and modifications, and various changes are possible without departing from the object of the present invention.

[0066] For example, as in Modification 3, in the embodiment and Modifications 1 and 2, the type of lead wire is not limited to a CP wire. The lead wire may be, for example, a copper lead wire (a metal wire mainly containing copper). When a copper lead wire is used in Modification 2 (i.e., when the main metal materials of the wire rod 100 and the lead wire 3 are both copper), the following effect can be obtained in addition to the above-described effect. That is, when the main metal materials of the wire rod 100 and the lead wire 3 are both copper, there is a problem that, when attempting to melt the wire rod 100 by arc welding, the lead wire 3 melts excessively, making it impossible to properly connect the wire rod 100 and the lead wire 3 (in other words, making it impossible to properly form the welded portion 4). On the other hand, there is a problem that, when the amount of discharge is suppressed in order to properly melt the lead wire 3, the wire rod 100 does not melt sufficiently, and in this case too, there is a problem that the wire rod 100 and the lead wire 3 cannot be properly connected. In contrast, in the manufacturing method according to Modification 2, only the end 100a of the wire 100 is melted by laser welding, and the lead wire 3 is pressed into the molten pool A and then melted by the heat of the molten pool A. The molten pool A at the end 100a and the molten copper at the end 3a of the lead wire 3 mix and solidify to form the weld 4. This manufacturing method can avoid excessive melting of the lead wire 3 or insufficient melting of the wire 100, and therefore can appropriately manufacture the lead terminal 101 in which the main metallic materials of both the wire 100 and the lead wire 3 are copper, which has been difficult to manufacture by arc welding. Note that the weld 4 is mostly a solidified structure of copper, and contains a small amount of an alloy of copper and other metals (e.g., tin).

[0067] Furthermore, the pushing mechanism may be provided in the jig 200 instead of the jig 300. That is, the pushing mechanism may be configured to apply an external force to the wire 100 that pushes the wire 100 axially toward the lead wire 3 by a predetermined distance at a predetermined speed.

[0068] Furthermore, in the above-described embodiment (and Modifications 1 to 3), the wire 100, which is the material of the electrode terminal 2, and the lead wire 3 are welded and then the wire 100 is press-worked to form the electrode terminal 2. Instead of this, the wire 100 may be press-worked first to form the electrode terminal 2, and then the lead wire 3 may be welded to one end of the rod-shaped portion 21 thereof.

[0069] Furthermore, in the above-described embodiment and Modifications 1 to 3, a hybrid laser combining an infrared laser and a short-wavelength laser may be used as the laser irradiator 400.

[0070] Furthermore, as described in the above-described embodiment, the absorption rate of aluminum is the same in the entire wavelength band of infrared rays and visible light. Therefore, when an aluminum wire is used for the wire 100, not limited to an infrared laser or a short-wavelength laser, other inexpensive laser irradiators may be used.

Description of Reference Numerals

[0071] 1,101: Lead terminal, 2,102: Electrode terminal, 3,103: Lead wire, 3a: End portion of lead wire, 3b: End face of lead wire, 3c: Outer peripheral surface of lead wire, 4,104: Welded portion, 21,121: Rod-shaped portion, 22,122: Rolled portion, 100: Wire, 100a: End portion of wire, 100b: End face of wire, 100c: Outer peripheral surface of wire, 200: Fixture, 300: Fixture, 400: Laser irradiator

Claims

1. A method for manufacturing a lead terminal for a power storage device, comprising an electrode terminal made of a wire mainly containing aluminum or copper, and a lead wire connected to the electrode terminal via a welded portion, a first step of aligning the wire and the lead wire linearly and holding the wire and the lead wire in a state where the distance between the end face of the wire on the lead wire side and the end face of the lead wire on the wire side is maintained at a predetermined distance; a second step of irradiating the end of the wire on the lead wire side with a laser beam using a laser irradiator to melt the end; a third step of forming the welded portion by pushing one of the wire and the lead wire axially toward the other after a predetermined time has elapsed from the start of irradiation of the laser beam in the second step; comprising a method for manufacturing a lead terminal.

2. The method for manufacturing a lead terminal according to claim 1, wherein in the first step, a CP wire or a metal wire mainly containing copper is used as the lead wire. a method for manufacturing a lead terminal.

3. The method for manufacturing a lead terminal according to claim 1, wherein in the second step, the laser beam is irradiated onto the outer peripheral surface of the end of the wire from a direction perpendicular to the axial direction. a method for manufacturing a lead terminal.

4. The method for manufacturing a lead terminal according to claim 3, wherein in the second step, the laser beam is irradiated onto a predetermined position on the outer peripheral surface of the wire. a method for manufacturing a lead terminal.

5. The method for manufacturing a lead terminal according to claim 3, wherein in the first step, a wire mainly containing aluminum is used as the electrode terminal, and the predetermined time in the third step is the irradiation time of the laser beam. a method for manufacturing a lead terminal.

6. The method for manufacturing a lead terminal according to claim 4, wherein in the first step, a wire mainly containing aluminum is used as the electrode terminal, and the predetermined time in the third step is the irradiation time of the laser beam. a method for manufacturing a lead terminal.

7. The method for manufacturing a lead terminal according to claim 1, wherein in the second step, the laser beam is irradiated onto the end face of the end of the wire from a direction obliquely intersecting the axial direction. a method for manufacturing a lead terminal.

8. The method for manufacturing a lead terminal according to claim 7, wherein in the first step, a wire mainly containing aluminum is used as the electrode terminal, and the predetermined time in the third step is the irradiation time of the laser beam. Method for manufacturing a lead terminal. **Claim 9** The method for manufacturing a lead terminal according to any one of Claims 1 to 8, wherein in the first step, a wire mainly containing aluminum is used as the electrode terminal, and the laser irradiator is an infrared laser. Method for manufacturing a lead terminal. **Claim 10** The method for manufacturing a lead terminal according to any one of Claims 1 to 4 and Claim 7, wherein in the first step, a wire mainly containing copper is used as the electrode terminal, and the laser irradiator is a short-wavelength laser or a hybrid laser. Method for manufacturing a lead terminal. **Claim 11** The method for manufacturing a lead terminal according to any one of Claims 1 to 8, wherein in the first step, a wire and a lead wire having a wire diameter ratio of the lead wire to the wire of 83% or more and 100% or less with respect to the wire are used for the wire and the lead wire. Method for manufacturing a lead terminal.

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