Welding method, metal laminate, electric component, and electric product

Abstract

To provide a new and improved welding method which can weld a laminate where a plurality of metal foils and metal members are superimposed on each other, and a metal laminate which is welded by the welding method, an electric component, and an electric product.SOLUTION: A welding method for irradiating a metal foil on a side opposite to a metal member out of a plurality of metal foils superimposed on the metal member with a first laser beam and a second laser beam having energy density lower than that of the first laser beam, and welding the metal member and the plurality of metal foils includes a step of irradiating the metal foil with the laser beam and forming a molten pool over the plurality of metal foils and the metal member, and a step of solidifying the molten pool and forming a weld part, wherein the step of forming the molten pool sweeps the spot of the laser beam on the surface of the metal foil, and absorption energy per unit length in a sweeping direction of the plurality of metal foils and the metal member which has been absorbed from the laser beam is 0.14 [J / mm] or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a welding method, a metal laminate, an electrical component, and an electrical product. [Background technology]

[0002] 2. Description of the Related Art Conventionally, batteries in which a plurality of tabs and terminals are joined by laser welding are known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-4643 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of welding, it is important not only to ensure the required joint strength, but also to avoid defects such as cutting of multiple metal foils or partial tearing of the metal foils at the site irradiated with the laser light.

[0005] Therefore, one of the objects of the present invention is to provide a new and improved welding method capable of welding, for example, a laminate in which a plurality of metal foils and metal members are overlapped, as well as a metal laminate, an electrical component, and an electrical product welded by the welding method. [Means for solving the problem]

[0006] The welding method of the present invention is a welding method for welding a metal member and a plurality of metal foils by, for example, irradiating a laser light including a first laser light and a second laser light having a lower energy density than the first laser light to a metal foil on an opposite side of the metal member among a plurality of metal foils overlapping on a metal member in a first direction, the metal foil and the plurality of metal foils being welded together, the method comprising the steps of: irradiating the laser light to form a molten pool spanning the plurality of metal foils and the metal member; and solidifying the molten pool to form a weld. In the step of forming the molten pool, a spot of the laser light is swept over the surface of the metal foil, and the absorbed energy from the laser light by the plurality of metal foils and the metal member, the absorbed energy per unit length in the sweep direction, is 0.14 [J / mm] or less.

[0007] In the welding method, the absorbed energy may be equal to or greater than a level at which a metal foil in contact with the metal member among the plurality of metal foils can melt.

[0008] In the welding method, the absorbed energy may be 0.05 [J / mm] or more when a thickness of the plurality of metal foils overlapped in the first direction is 400 [μm] or more.

[0009] In the welding method, a sweep speed of the spot may be 300 [mm / s] or more and 10,000 [mm / s] or less.

[0010] In the welding method, the first laser beam may have a wavelength of 800 nm or more and 1200 nm or less, and the second laser beam may have a wavelength of 550 nm or less.

[0011] In the welding method, the second laser light may have a wavelength of 400 nm or more and 500 nm or less.

[0012] In the welding method, the laser light beam may be shaped by a beam shaper.

[0013] In the welding method, the beam shaper may be a DOE.

[0014] In the welding method, in the process of forming the molten pool, a sweep trajectory of the spot on the metal foil may be set so that at least a portion of the sweep trajectory overlaps with a portion of the spot that has already been melted by irradiation with the laser light.

[0015] In the welding method, the sweep locus may include an endless portion.

[0016] In the welding method, the sweep locus may have an endless shape as a whole.

[0017] In the welding method, in the process of forming the molten pool, after the endless portion is formed in the sweep trajectory, the spot of the laser light may be swept in an inner area of ​​the endless portion on the surface.

[0018] In the welding method, the sweep trajectory may include a plurality of sections extending adjacent to each other.

[0019] In the welding method, the sweep locus may include a line segment section connecting two points on the sweep locus.

[0020] In the welding method, the sweep trajectory may include a spiral section.

[0021] In the welding method, the sweep trajectory may include a wobbling section in which the reference point moves in a second direction while the spot revolves around the reference point.

[0022] In the welding method, the sweep trajectory may include a section extending linearly in the second direction, and the wobbling section swept after the linear section and partially overlapping with the linear section.

[0023] In the welding method, the sweep locus may include a portion where the sweep loci intersect with each other.

[0024] In the welding method, the width of the welded portion formed may be 30 μm or more and 300 μm or less.

[0025] The welding method of the present invention is, for example, a welding method for welding a metal member and a plurality of metal foils by irradiating a laser light including a first laser light and a second laser light having a lower energy density than the first laser light to a metal foil on an opposite side to the metal member among a plurality of metal foils overlapping on a metal member in a first direction, the method including: forming a molten pool spanning the plurality of metal foils and the metal member by irradiating the laser light; and solidifying the molten pool to form a weld, wherein in the step of forming the molten pool, an outer diameter of the weld formed when a point-like spot of the laser light is irradiated onto the metal foil on the opposite side to the metal member among the plurality of metal foils, or a width of the weld formed when the spot of the laser light is swept over the metal foil on the opposite side to the metal member among the plurality of metal foils is 30 [μm] or more and 300 [μm] or less.

[0026] The welding method of the present invention is, for example, a welding method for welding a metal member and a plurality of metal foils by irradiating a laser light including a first laser light and a second laser light having a lower energy density than the first laser light to a metal foil on an opposite side to the metal member among a plurality of metal foils overlapping on a metal member in a first direction, the method including a step of irradiating the laser light to form a molten pool spanning the plurality of metal foils and the metal member, and a step of solidifying the molten pool to form a weld, wherein in the step of forming the molten pool, a point-shaped spot of the laser light is irradiated onto the metal foil on the opposite side to the metal member among the plurality of metal foils, and the input energy of the laser light to the plurality of metal foils and the metal member is 1.0 [J] or less.

[0027] In the welding method, the input energy may be equal to or greater than a level that allows a metal foil in contact with the metal member among the plurality of metal foils to melt.

[0028] The welding method of the present invention is a welding method for welding a metal member and a plurality of metal foils together by, for example, irradiating a laser light including a first laser light and a second laser light having a lower energy density than the first laser light to a metal foil on an opposite side of a plurality of metal foils overlapping a metal member in a first direction, the metal foil and the plurality of metal foils being welded together, the method including: a step of irradiating the laser light to form a molten pool spanning the plurality of metal foils and the metal member; and a step of solidifying the molten pool to form a weld, wherein in the step of forming the molten pool, a spot of the laser light is swept over the surface of the metal foil, and the sweep trajectory of the spot on the metal foil includes a wobbling section in which the spot revolves around a reference point while the reference point moves in a second direction, and a section that extends linearly in the second direction and partially overlaps with the wobbling section.

[0029] The metal laminate of the present invention, for example, comprises a metal member, a plurality of metal foils stacked on the metal member in a first direction, and a welded portion at which the metal member and the plurality of metal foils are welded together, and in the metal foil of the plurality of metal foils opposite the metal member, the outer diameter of the welded portion when formed in a dot shape, or the width of the welded portion when formed in a line shape, is 30 μm or more and 300 μm or less.

[0030] The electrical component of the present invention includes, for example, the metal laminate as a conductor.

[0031] The electrical appliance of the present invention includes, for example, the metal laminate as a conductor. Effect of the Invention

[0032] According to the present invention, it is possible to provide a novel and improved welding method capable of welding, for example, a laminate in which a plurality of metal foils and metal members are overlapped, as well as a metal laminate, an electrical component, and an electrical product welded by the welding method. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is an exemplary schematic configuration diagram of a laser welding device according to a first embodiment. [Diagram 2] FIG. 2 is an exemplary schematic cross-sectional view of a metal laminate as an object to be processed by the laser welding apparatus of the embodiment. [Diagram 3] FIG. 3 is an illustrative schematic cross-sectional view of a battery including a metal laminate as an object to be processed by the laser welding apparatus of the embodiment. [Figure 4] FIG. 4 is an exemplary schematic diagram showing a beam (spot) of laser light formed on the surface of an object to be processed by the laser welding apparatus of the first embodiment. [Diagram 5] FIG. 5 is a graph showing the light absorptance of metals versus the wavelength of the irradiated laser light. [Figure 6] FIG. 6 is an exemplary flowchart showing the procedure of the welding method according to the embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view illustrating an example of a mechanism by which a fracture occurs at the boundary between a weld and a metal foil in a metal laminate. [Figure 8] FIG. 8 is an illustrative cross-sectional view showing a case where a break occurs in a welded portion by the welding method of the reference example. [Figure 9] FIG. 9 is an exemplary cross-sectional view showing a case where a good joint state is obtained by the welding method according to the embodiment. [Figure 10] FIG. 10 is an illustrative cross-sectional view showing a case where a part of the metal foil is torn by the welding method of the reference example. [Figure 11] FIG. 11 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 12] FIG. 12 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 13] FIG. 13 is a cross-sectional view taken along line XIII-XIII of FIG. [Figure 14] FIG. 14 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 15]FIG. 15 is a cross-sectional view taken along line XV-XV of FIG. [Figure 16] FIG. 16 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 17] FIG. 17 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 18] FIG. 18 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 19] FIG. 19 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 20] FIG. 20 is a schematic diagram showing an example of a trajectory of a laser light spot on a surface of a metal foil by the welding method of the embodiment. [Figure 21] FIG. 21 is an exemplary schematic configuration diagram of the laser welding device according to the second embodiment. [Figure 22] FIG. 22 is an explanatory diagram showing the concept of the principle of the diffractive optical element included in the laser welding apparatus of the second embodiment. [Figure 23] FIG. 23 is a schematic diagram showing an example of a laser light beam (spot) formed on the surface of the processing object by the laser welding apparatus of the second embodiment. [Figure 24] FIG. 24 is an exemplary schematic configuration diagram of a laser welding device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Exemplary embodiments of the present invention are disclosed below. The configurations of the embodiments shown below, and the actions and results (effects) brought about by the configurations are merely examples. The present invention can be realized by configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derivative effects) obtained by the configurations.

[0035] The embodiments described below have similar configurations. Therefore, according to the configurations of the respective embodiments, similar actions and effects based on the similar configurations can be obtained. In addition, in the following, the similar configurations are given the same reference numerals, and duplicated descriptions may be omitted.

[0036] In each figure, the X direction is represented by an arrow X, the Y direction is represented by an arrow Y, and the Z direction is represented by an arrow Z. The X direction, Y direction, and Z direction intersect each other and are perpendicular to each other. The Z direction is the normal direction to the surface Wa (machined surface, welded surface) of the workpiece W, the thickness direction of the metal foil 12, and the stacking direction of the metal foil 12 and the metal laminate 10.

[0037] In addition, in this specification, ordinal numbers are given for the sake of convenience to distinguish between parts, members, parts, laser beams, directions, etc., and do not indicate priority or order.

[0038] [First embodiment] Fig. 1 is a schematic configuration diagram of a laser welding apparatus 100 according to the first embodiment. As shown in Fig. 1, the laser welding apparatus 100 includes a laser device 111, a laser device 112, an optical head 120, and an optical fiber 130. The laser welding apparatus 100 is an example of a welding apparatus.

[0039] The laser devices 111 and 112 each have a laser oscillator and are configured to be able to output laser light with a power of, for example, several kW. The laser devices 111 and 112 emit laser light with a wavelength of 400 nm or more and 1200 nm or less. The laser devices 111 and 112 each have a laser light source therein, such as a fiber laser, a semiconductor laser (element), a YAG laser, or a disk laser. The laser devices 111 and 112 may be configured to output multi-mode laser light with a power of several kW as the sum of the outputs of multiple light sources.

[0040] The laser device 111 outputs a first laser light having a wavelength of, for example, 800 [nm] or more and 1200 [nm] or less. The laser device 111 is an example of a first laser device. As an example, the laser device 111 has a fiber laser or a semiconductor laser (element) as a laser light source. The laser oscillator of the laser device 111 may also be referred to as a first laser oscillator.

[0041] On the other hand, the laser device 112 outputs a second laser light having a wavelength of, for example, 550 [nm] or less. The laser device 112 is an example of a second laser device. As an example, the laser device 112 has a semiconductor laser (element) as a laser light source. It is preferable that the laser device 112 outputs a second laser light having a wavelength of 400 [nm] or more and 500 [nm] or less. The laser oscillator of the laser device 112 may also be referred to as a second laser oscillator.

[0042] The optical fiber 130 optically connects the laser devices 111 and 112 to the optical head 120. In other words, the optical fiber 130 guides the laser light output from the laser devices 111 and 112 to the optical head 120.

[0043] The optical head 120 is an optical device that irradiates the laser light input from the laser devices 111 and 112 toward the workpiece W. The optical head 120 includes a collimator lens 121, a condenser lens 122, a mirror 123, a filter 124, and a galvanometer scanner 126. The collimator lens 121, the condenser lens 122, the mirror 123, the filter 124, and the galvanometer scanner 126 may also be referred to as optical components.

[0044] The collimating lenses 121 (121-1, 121-2) each collimate the laser light input via the optical fiber 130. The collimated laser light becomes parallel light.

[0045] The mirror 123 reflects the first laser light, which has been collimated by the collimator lens 121-1, toward the galvano scanner 126.

[0046] The filter 124 is a high-pass filter that transmits the first laser light and reflects but does not transmit the second laser light. The first laser light from the mirror 123 transmits through the filter 124 and travels toward the galvano scanner 126. On the other hand, the second laser light from the collimator lens 121-2 is reflected by the filter 124 and travels toward the galvano scanner 126.

[0047] The galvano scanner 126 has a plurality of mirrors 126a, 126b. By changing the angles of the plurality of mirrors 126a, 126b, the emission direction of the laser light L from the optical head 120 can be switched, and thus the irradiation position of the laser light L on the surface of the workpiece W can be changed. The angles of the mirrors 126a, 126b are each changed by, for example, a motor (neither shown) controlled by a control device. The optical head 120 can sweep the laser light L on the surface Wa of the workpiece W by changing the emission direction of the laser light L while irradiating the laser light L.

[0048] The condenser lens 122 condenses the laser light coming from the galvano scanner 126 as parallel light, and irradiates the laser light L (output light) onto the workpiece W.

[0049] The processing object W is a metal laminate 10 in which a metal member 11 and a plurality of metal foils 12 are laminated in the Z direction. The metal laminate 10 may also be referred to as a laminate. The metal laminate 10 has a metal member 11, a plurality of metal foils 12, and a welded portion 14. The welded portion 14 welds the metal member 11 and the plurality of metal foils 12 together, mechanically and electrically connecting them.

[0050] 2 is a cross-sectional view of the metal laminate 10. As an example, the metal member 11 has a plate-like shape that spreads across the Z direction. However, the metal member 11 is not limited to a plate-like member. A plurality of metal foils 12 are laminated in the Z direction on an end face 11a of the metal member 11 in the Z direction.

[0051] When the metal laminate 10 is welded by the laser welding device 100, the metal laminate 10 is temporarily fixed together in the above-mentioned laminated state by a fixing jig (not shown), and is set in a posture in which the normal direction of the surface Wa of the metal foil 12 is approximately parallel to the Z direction. The fixing jig is, for example, two metal plates arranged at a distance from each other in the Z direction. The two metal plates are in a posture intersecting with the Z direction and sandwich the laminated metal member 11 and the multiple metal foils 12 in the Z direction. Of the two metal plates, the metal plate facing the optical head 120 is provided with a through hole through which the laser light L can pass.

[0052] The surface Wa is an end face in the Z direction of the metal laminate 10, and is the metal foil 12 of the multiple metal foils 12 opposite to the metal member 11, in other words, the surface of the metal foil 12 farthest from the metal member 11, opposite to the metal member 11. The laser light L is irradiated in the opposite direction to the Z direction to the surface Wa, in other words, from the opposite side to the metal member 11 to the surface Wa along the Z direction. The surface opposite to the end face 11a of the metal member 11 is the back surface Wb of the metal laminate 10. The surface Wa is also referred to as the irradiation surface of the laser light L, and can also be referred to as the opposing surface facing the optical head 120. The Z direction is an example of a first direction.

[0053] By irradiating the laser light L in this manner, the welded portion 14 extends from the surface Wa in the direction opposite to the Z direction. The direction opposite to the Z direction may also be referred to as the depth direction of the welded portion 14. Furthermore, by sweeping the laser light L in the sweep direction SD on the surface Wa, the welded portion 14 also extends in the sweep direction SD with a cross-sectional shape substantially similar to that shown in FIG. 2. The sweep direction SD is a temporary direction at the position where the laser light L is irradiated. Furthermore, when the sweep direction SD is the X direction as in FIGS. 1 and 2, the Y direction perpendicular to the X direction may also be referred to as the width direction of the welded portion 14.

[0054] 3 is a cross-sectional view of a battery 1 as an electrical product having a metal laminate 10. The battery 1 is one application example of the metal laminate 10. In this case, the metal laminate 10 is an example of an electrical component as a conductor, and is an example of an electrical component included in an electrical product. An electrical component may also be referred to as a component of an electrical product.

[0055] The battery 1 shown in FIG. 3 is, for example, a laminated lithium-ion battery cell. The battery 1 has two film-like exterior materials 20. A storage chamber 20a is formed between the two exterior materials 20. A plurality of flat positive electrode materials 13p, a plurality of flat negative electrode materials 13m, and a plurality of flat separators 15 are stored in the storage chamber 20a. In the storage chamber 20a, the positive electrode materials 13p and the negative electrode materials 13m are alternately stacked with the separators 15 interposed therebetween. Metal foils 12 extend from the plurality of positive electrode materials 13p and the plurality of negative electrode materials 13m. In the example of FIG. 3, the plurality of metal foils 12 extending from each of the positive electrode materials 13p are stacked on the metal member 11 at the end on the opposite side in the Y direction of the battery 1, and a metal laminate 10 is provided in which the metal member 11 and the plurality of metal foils 12 are welded to the end. On the positive electrode side, only a part of the metal member 11 is exposed to the outside of the exterior material 20, and the other part of the metal member 11, the multiple metal foils 12, and the welded part 14 are not exposed to the outside of the exterior material 20. The metal member 11 constitutes the positive electrode terminal of the battery 1. On the other hand, the multiple metal foils 12 extending from each of the negative electrode materials 13m are overlapped on the metal member 11 at the end of the battery 1 in the Y direction, and a metal laminate 10 is provided in which the metal member 11 and the multiple metal foils 12 are welded to the end. On the negative electrode side, only a part of the metal member 11 is exposed to the outside of the exterior material 20, and the other part of the metal member 11, the multiple metal foils 12, and the welded part 14 are not exposed to the outside of the exterior material 20. The metal member 11 constitutes the negative electrode terminal of the battery 1.

[0056] As shown in FIG. 3, each metal laminate 10 is sandwiched between two exterior materials 20. Between the metal laminate 10 and the exterior material 20, airtightness or liquidtightness is ensured by a sealing material or the like. For this reason, it is preferable that the front surface Wa and back surface Wb of the metal laminate 10 have as little or no unevenness as possible. When the battery 1 is a lithium ion battery cell, the metal foil 12 constituting the metal laminate 10 as the positive terminal is made of, for example, an aluminum-based metal material, and the metal foil 12 constituting the metal laminate 10 as the negative terminal is made of, for example, a copper-based metal material. The positive terminal and the negative terminal are examples of electrical components. The metal laminate 10 or the metal member 11 may also be referred to as an electrode tab or a tab. The metal member 11 may also be referred to as a conductive member.

[0057] FIG. 4 is a schematic diagram showing a beam (spot) of laser light L irradiated onto a surface Wa. Each of beams B1 and B2 has, for example, a Gaussian-shaped power distribution in the radial direction of a cross section perpendicular to the optical axis direction of the beam. However, the power distribution of beams B1 and B2 is not limited to a Gaussian shape. In addition, in each diagram in which each beam B1, B2 is represented by a circle as in FIG. 4, the diameter of the circle representing the beam B1, B2 is the beam diameter of each beam B1, B2. The beam diameter of each beam B1, B2 includes the peak of the beam and is 1 / e of the peak intensity. 2 In the case of a non-circular beam (not shown), the diameter of the region with an intensity of 1 / e of the peak intensity in the direction perpendicular to the sweep direction SD is defined as the diameter of the region with an intensity of 1 / e 2 The length of the region where the intensity is equal to or greater than this can be defined as the beam diameter. The beam diameter on the surface Wa is called the spot diameter.

[0058] As shown in Fig. 4, in this embodiment, as an example, the beam of the laser light L is formed such that the beam B1 of the first laser light and the beam B2 of the second laser light overlap on the surface Wa, the beam B2 is larger (wider) than the beam B1, and the outer edge B2a of the beam B2 surrounds the outer edge B1a of the beam B1. In this case, the spot diameter D2 of the beam B2 is larger than the spot diameter D1 of the beam B1. Also, the energy density of the beam B2 is set lower than the energy density of the beam B1. On the surface Wa, the beam B1 is an example of a first spot, and the beam B2 is an example of a second spot.

[0059] 4, the beam (spot) of the laser light L on the surface Wa has a point-symmetric shape with respect to the center point C, so the shape of the spot is the same for any sweep direction SD. Therefore, when a moving mechanism for relatively moving the optical head 120 and the workpiece W is provided to sweep the laser light L on the surface Wa, the moving mechanism needs to have at least a mechanism capable of relatively translating, and a mechanism capable of relatively rotating can be omitted in some cases.

[0060] The metal member 11 and the metal foil 12 as the processing object W may each be made of a conductive metal material. The metal material may be, for example, a copper-based metal material, an aluminum-based metal material, a nickel-based metal material, an iron-based metal material, or a titanium-based metal material, and more specifically, may be copper, a copper alloy, aluminum, an aluminum alloy, tin, nickel, a nickel alloy, iron, stainless steel, titanium, a titanium alloy, etc. The metal member 11 and the metal foil 12 may be made of the same material or different materials.

[0061] [Wavelength and light absorption rate] Here, the light absorptance of metal materials will be explained. Fig. 5 is a graph showing the light absorptance of each metal material versus the wavelength of the irradiated laser light L. The horizontal axis of the graph in Fig. 5 is the wavelength, and the vertical axis is the absorptance. Fig. 5 shows the relationship between wavelength and absorptance for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti).

[0062] Although the characteristics differ depending on the material, it can be seen that for each metal shown in Figure 5, the energy absorption rate is higher when using blue or green laser light (second laser light) than when using general infrared (IR) laser light (first laser light). This characteristic is prominent in copper (Cu), gold (Au), etc.

[0063] When a laser beam is irradiated onto a workpiece W, which has a relatively low absorption rate for the wavelength used, most of the light energy is reflected and does not affect the workpiece W as heat. Therefore, a relatively high power must be applied to obtain a melted region of sufficient depth. In this case, the center of the beam is suddenly energized, causing sublimation and forming a keyhole.

[0064] On the other hand, when a laser beam is irradiated onto a workpiece W having a relatively high absorptivity for the wavelength used, most of the input energy is absorbed by the workpiece W and converted into thermal energy. In other words, since there is no need to apply excessive power, no keyhole is formed and melting occurs by thermal conduction.

[0065] In this embodiment, the wavelength of the first laser light, the wavelength of the second laser light, and the material of the object W to be processed are selected so that the absorptance of the second laser light in the object W to be processed is higher than the absorptance of the first laser light. In this case, when the sweep direction is the sweep direction SD shown in Fig. 4, the second laser light is first irradiated to the part to be welded (hereinafter referred to as the welded part) of the object W by sweeping the spot of the laser light L from the region B2f of the beam B2 of the second laser light located in front of SD in Fig. 4. Thereafter, the part to be welded is irradiated with the beam B1 of the first laser light, and then the second laser light is irradiated again from the region B2b of the beam B2 of the second laser light located behind the sweep direction SD.

[0066] Therefore, a thermally conductive molten region is first generated in the welded portion by irradiation of the second laser light having a high absorptivity in the region B2f. Then, a deeper keyhole-shaped molten region is generated in the welded portion by irradiation of the first laser light. In this case, since a thermally conductive molten region is formed in advance in the welded portion, a molten region of a required depth can be formed by a lower power first laser light compared to a case where the thermally conductive molten region is not formed. Then, the molten state of the welded portion is changed by irradiation of the second laser light having a high absorptivity in the region B2b. From this viewpoint, the wavelength of the second laser light is preferably 550 [nm] or less, and more preferably 500 [nm] or less.

[0067] Furthermore, experimental research by the inventors has confirmed that welding defects such as spatters and blowholes can be reduced in welding by irradiation with laser light L of a beam as shown in Fig. 4. This is presumably because the molten pool of the workpiece W formed by beam B2 and beam B1 becomes more stable by preheating the workpiece W by region B2f of beam B2 before the arrival of beam B1.

[0068] [Welding method] FIG. 6 is a flow chart showing an example of a procedure for laser welding of the workpiece W by the laser welding device 100. As shown in FIG. 6, first, the metal laminate 10 in which the metal member 11 and the multiple metal foils 12 are temporarily fixed together by the holder, that is, the workpiece W, is set in a state in which the laser light L is irradiated onto the surface Wa (S11). Then, the laser light L is irradiated onto the surface Wa of the workpiece W to form a molten pool across the multiple metal foils 12 and the metal member 11 (S12). In S12, the laser light L is irradiated approximately along the opposite direction to the Z direction. Also, in S12, the laser light L and the metal laminate 10 may be moved relatively while the laser light L including the beams B1 and B2 is irradiated onto the surface Wa. In this case, the spot of the laser light L on the surface Wa moves in the sweep direction SD on the surface Wa, in other words, it is swept. The molten pool formed by the irradiation of the laser light L solidifies as the temperature drops, forming a weld 14 (S13). In this manner, the metal foils 12 and the metal members 11 are welded together, and the metal laminate 10 is integrated.

[0069] [rupture] The inventors discovered that when welding multiple metal foils 12 and a metal member 11, fractures may occur at the boundary B between the weld 14 and the metal foil 12, and that fractures can be avoided by setting appropriate conditions.

[0070] 7 are cross-sectional views showing the mechanism by which a fracture occurs, where (a) shows a state (S12) in which a molten pool M has been formed, and (b) shows a state in which the molten pool M has solidified to form a weld 14. In the example of Fig. 7, as shown in (b), a fracture 14a occurs at the boundary B between the weld 14 and the multiple metal foils 12. This is presumably because the molten pool M contracts when it cools and solidifies to form the weld 14, and the metal foils 12 are unable to keep up with the contraction, resulting in the fracture 14a at the boundary B.

[0071] [Conditions that make fractures less likely to occur] The inventors have obtained the following findings (1) to (4) through experimental research. In the experiment, the processing object W (metal laminate 10) included a metal member 11 made of an aluminum-based material and a metal foil 12, the thickness of the metal foil 12 was 20 [μm], the number of the metal foils 12 was 20, the wavelength of the first laser light was 1070 [nm], and the wavelength of the second laser light was 465 [nm].

[0072] (1) The smaller the volume of the welded portion 14, the less likely the fracture 14a is to occur. Specifically, it was found that when the outer diameter of the welded portion 14 formed in a dot shape, or the width of the welded portion 14 formed in a line shape, is 30 [μm] or more and 300 [μm] or less, the fracture 14a is less likely to occur. When the outer diameter of the welded portion 14 formed in a dot shape, or the width of the welded portion 14 formed in a line shape, is greater than 300 [μm], the volume of the molten pool M (welded portion 14) becomes large, and the fracture 14a occurs at the boundary B between the welded portion 14 and the metal foil 12. In addition, in order to obtain a sufficient welded state between the multiple metal foils 12 and the metal member 11, the welded portion 14 needs to have the metal foil 12 in contact with the metal member 11 melted by irradiation of the laser light L. In this regard, when the processing speed is high (or the input energy amount is small), the molten pool M (weld portion 14) cannot reach the metal member 11 from the surface Wa; in other words, the metal foil 12 in contact with the metal member 11 cannot melt, and a sufficient welded state between the multiple metal foils 12 and the metal member 11 by the weld portion 14 cannot be obtained ("non-joining" described below). As a countermeasure, when the power of the first laser beam is increased relative to the second laser beam, the molten pool M is not formed in the multiple metal foils 12, and the multiple metal foils 12 are cut ("cut" described below). Note that the spot diameter D2 is also the width of the beam when the spot of the laser beam L is swept over the surface Wa.

[0073] (2) In the case where the spot of the laser light L is not swept on the surface Wa, that is, in the case of spot welding, it was found that when the input energy to the plurality of metal foils 12 and the metal member 11 is 1.0 [J] or less, the fracture 14a is unlikely to occur. When the input energy is larger than 1.0 [J], the volume of the molten pool M (welded portion 14) becomes large, and the fracture 14a occurs at the boundary B between the welded portion 14 and the metal foil 12. Also, as described above, in order to obtain a sufficient welded state between the plurality of metal foils 12 and the metal member 11, the welded portion 14 needs to have the metal foil 12 in contact with the metal member 11 melted by irradiation with the laser light L. From this viewpoint, the input energy needs to be equal to or larger than the magnitude at which the metal foil 12 in contact with the metal member 11 can melt.

[0074] (3) When the spot of the laser light L is swept over the surface Wa, it has been found that if the absorbed energy E (formula (1)) by the metal foils 12 and the metal member 11 is 0.14 [J / mm] or less, fracture 14a is unlikely to occur. The absorbed energy E is defined as the following formula (1). E = A Pw / V (1) Here, E is the absorbed energy [J / mm], A is the absorptivity by the metal, Pw is the power [W] of the laser light L, and V is the sweep speed [mm / s]. Table 1 shows the experimental results, including the sweep speed [mm / s], absorbed energy [J / mm], and results for each sample (experiment number). [Table 1]

[0075] In the "Results" section of Table 1, "cut" refers to a state in which the multiple metal foils 12 are separated in a direction (width direction, Y direction) intersecting the sweep direction SD, and no welded portion 14 is formed. FIG. 8 is a cross-sectional view showing an example of the "cut" state. As shown in FIG. 8, in this case, the welded portion 14 is not formed, a gap 14c is formed, and the multiple metal foils 12 are cut in the Y direction (width direction) intersecting the sweep direction SD. In addition, the metal material melted from the multiple metal foils 12 by the irradiation of the laser light L moves between the multiple metal foils 12 and the metal member 11 due to the energy of the laser light L and gravity, and remains as a residue 14b.

[0076] "Joined" is a state in which welds 14 are formed across multiple metal foils 12 and the metal member 11, and the multiple metal foils 12 and the metal member 11 are satisfactorily mechanically and electrically joined via the welds 14. Fig. 9 is a cross-sectional view showing an example of the "joined" state. In the "Results" of Table 1, only "joined" is an acceptable state.

[0077] "Fracture" refers to a state in which the welded portion 14 and one of the metal foils 12 are torn at the boundary B, i.e., a state in which a fracture 14a has occurred. Fig. 10 is a cross-sectional view showing an example of the "fracture" state. As shown in Fig. 10, fracture 14a is likely to occur in a portion T close to the emission source of the laser light L, in other words, in a portion T far from the metal member 11. It can be seen from Fig. 10 that fracture 14a occurs when the metal foil 12 is stretched in the Y direction (width direction).

[0078] Moreover, "unjoined" indicates a state in which the welded portion 14 does not penetrate all the metal foils 12 and does not reach the metal member 11.

[0079] From the above-mentioned experiments and the investigation, it was found that when the absorbed energy is 0.14 [J / mm] or less, it does not "break" but "joins", that is, a good joint state is obtained. Furthermore, it is necessary that the absorbed energy is large enough not to "disjoin", that is, it is large enough to melt the metal foil 12 in contact with the metal member 11 among the plurality of metal foils 12. As an example, when the metal member 11 and the metal foil 12 made of an aluminum-based material are included, the thickness of the metal foil 12 is 20 [μm], and the number of the metal foils 12 is 20, the absorbed energy that melts the metal foil 12 in contact with the metal member 11 among the plurality of metal foils 12 is 0.05 [J / mm], and it was found that it is preferable to set the absorbed energy to 0.05 [J / mm] or more when the total thickness of the metal foils 12 is 400 [μm] or more. In addition, in the experiment No. 1 in Table 1, the second laser light was not irradiated, and only the first laser light was irradiated, so that it was "cut". The inventors have also found that in order to obtain such a range of absorbed energy, the sweep speed is preferably not less than 300 [mm / s] and not more than 10,000 [mm / s].

[0080] (4) It was found that when the spot of the laser light L is swept on the surface Wa, the fracture 14a is likely to occur at the start and end points of the sweep locus, and when the sweep locus has an endless section, the fracture 14a is unlikely to occur in the endless section. At the end of the sweep locus in the sweep direction, the area of ​​the boundary B between the welded portion 14 and the multiple metal foils 12 becomes wider, and the fracture 14a is likely to occur. In this regard, in the endless section of the sweep locus, the area of ​​the boundary B between the welded portion 14 and the multiple metal foils 12 can be made smaller, so that the fracture 14a is unlikely to occur. Figures 11 to 20 show examples of various loci P that can obtain a suitable joining state.

[0081] FIG. 11 illustrates a locus P1 (P) of the spot of the laser light L on the surface Wa. In addition, the thick solid lines in FIGS. 11, 12, 14, 16 to 20 indicate the locus of the center position of the spot of the laser light L. As shown in FIG. 11, the locus P1 has an endless section Pe and a plurality of line-segment sections Pl. The endless section Pe can also be called a closed path. The endless section Pe has an elliptical shape. In FIG. 11, the endless section Pe has a start point Pe and an end point Pee at the same position, but the start point Pe and the end point Pee do not necessarily have to be at the same position. For example, the start point Pes and the end point Pee may be positioned so as to overlap with other positions on the locus Pe of the spot of the laser light L, or may be spaced apart from the locus Pe of the spot of the laser light L by an interval equal to or less than the beam width (spot diameter D2) of the laser light L. The endless section Pe is an example of an endless section. The line-segment section Pl is bridged between the parallel linear sections of the endless section Pe that are spaced apart from each other. That is, the line-segment section Pl starts from a starting point Pls and ends at an end point Ple, and the starting point Pls is located on or in contact with the endless section Pe, and the end point Ple is located on or in contact with another endless section Pe. That is, the line-segment section Pl starts from a previously melted section and ends at a previously melted section. It can be said that the trajectory P1 in FIG. 11 has a plurality of endless sections or closed paths. The line-segment section Pl may be curved.

[0082] FIG. 12 illustrates a locus P2 (P) of a spot of the laser light L on the surface Wa. As shown in FIG. 12, the locus P2 also has an endless section Pe and a line-segment section Pl, as in the example of FIG. 11. The start point Pls of the line-segment section Pl is located on or in contact with the endless section Pe, and the end point Ple is located on or in contact with another endless section Pe. That is, in the example of FIG. 12, the line-segment section Pl also starts from a previously melted portion and ends at a previously melted portion. It can be said that the locus P2 in FIG. 12 also has a plurality of endless sections or closed paths. However, in the example of FIG. 12, the line-segment sections Pl are respectively connected between the curved portions of the endless section Pe that are spaced apart from each other, and are parallel to the straight portions of the endless section Pe. The straight-line portion of the endless section Pe and the multiple line-segment sections Pl extend adjacent to each other.

[0083] 11 and 12, all start points Pls and end points Ple of the line segment section Pl are located on or in contact with the endless section Pe, but some start points Pls and end points Ple of the line segment section Pl may be located on the endless section Pe. However, it is preferable that all start points Pls and end points Ple of the line segment section Pl are located on or in contact with the endless section Pe.

[0084] FIG. 13 is a cross-sectional view taken along the line XIII-XIII in FIG. 12. In FIG. 13, the previous molten pool M (or the welded portion 14) is indicated by a two-dot chain line, and the latest molten pool M is indicated by a solid line. As shown in FIG. 13, the latest molten pool M formed by sweeping the latest line-shaped section Pl is set to partially overlap with the previous endless section Pe (straight-line portion) or the previous molten pool M (or the welded portion 14) formed by sweeping the line-shaped section Pl. In this example, adjacent molten pools M (or adjacent latest molten pool M and previous welded portion 14) partially overlap in the width direction (Y direction). In this way, when the latest molten pool M partially overlaps with the previous molten pool M (or the welded portion 14), no boundary B is formed between the welded portion 14 and the multiple metal foils 12, and therefore no fracture 14a occurs. In order to obtain such overlap, the line-segment section Pl is set so that a part of the spot partially overlaps with the previous endless section Pe or the part melted by irradiation with the laser light L during the sweep of the line-segment section Pl. In this example, the inside of the endless section Pe is in a state in which it appears to be filled with the molten pool M (weld 14).

[0085] Fig. 14 illustrates a locus P3 (P) of a spot of the laser light L on the surface Wa. As shown in Fig. 14, the locus P3 has a spiral shape and has an endless shape as a whole. That is, the locus P3 has only an endless section Pe. The endless section Pe starts from a starting point Pes and ends at an end point Pee, and the starting point Pes is located on or in contact with the endless section Pe, and the end point Pee is also located on or in contact with the endless section Pe. That is, the endless section Pe starts from a previously melted portion and ends at a previously melted portion.

[0086] FIG. 15 is a cross-sectional view taken along the line XV-XV in FIG. 14. In FIG. 15 as well, the previous molten pool M (or the welded portion 14) is indicated by a two-dot chain line, and the latest molten pool M is indicated by a solid line. As shown in FIG. 15, the latest molten pool M formed by the sweep of the latest endless section Pe is set to partially overlap with the previous molten pool M (or the welded portion 14) formed by the sweep of the previous endless section Pe. In this example as well, the adjacent molten pools M (or the latest molten pool M and the previous welded portion 14) partially overlap in the width direction (Y direction). In order to obtain such an overlap, the endless section Pe is set so that a part of its spot partially overlaps with a portion melted by irradiation of the laser light L in the sweep of the previous endless section Pe. In this example as well, the inside of the endless section Pe is filled with the molten pool M (welded portion 14).

[0087] FIG. 16 illustrates a trajectory P4(P) of the spot of the laser light L on the surface Wa. As shown in FIG. 16, the trajectory P4 also has an endless shape overall. That is, the trajectory P4 has only an endless section Pe. However, in this example, as shown in FIG. 16, the front part of the endless section Pe is an elliptical section, and the rear part of the endless section Pe is a wobbling section in which the spot of the laser light L revolves around a reference point and the reference point moves in the X direction inside the elliptical section. The dashed-dotted arrow Lc in FIG. 16 is the movement trajectory of the reference point in the X direction. The X direction is an example of the second direction. The inventors have confirmed that wobbling is effective from the viewpoint of not causing fracture 14a, and that a suitable joining state can be obtained with wobbling even under conditions where the absorbed energy is higher and fracture 14a occurs without wobbling.

[0088] 14 and 16 show an example in which the trajectory P has one start point Pes and one end point Pee, but this is not limiting. The trajectory P may have any shape as long as it is endless overall, and may have, for example, multiple start points Pes and multiple end points Pee. Furthermore, the trajectory P may have other sweep paths locally within a range that does not impair the effects obtained in this embodiment.

[0089] FIG. 17 illustrates a locus P5(P) of a spot of laser light L on a surface Wa. As shown in FIG. 17, the locus P5 has a wobbling section Pw and a line-segment section Pl extending in the X direction and partially overlapping with the wobbling section Pw. In this example, the spot of the laser light L is swept in the line-segment section Pl, and then swept in the wobbling section Pw. The wobbling section Pw has a plurality of endless sections (closed paths). Therefore, in this example, the same effect as in the other examples in which the locus P has an endless section Pe can be obtained.

[0090] Fig. 18 illustrates a trajectory P6(P) of the spot of the laser beam L on the surface Wa. In this example, the trajectory P6 has a plurality of line-segment sections Pl, but does not have an endless section Pe, which is different from the example in Fig. 12. However, in this example, similar to the examples in Figs. 12 and 13, the line-segment sections Pl are set so that a part of the spot partially overlaps with a part that was melted by irradiation of the laser beam L in the previous sweep of the line-segment sections Pl. In this example, too, a predetermined range is filled with the molten pool M (welded portion 14), and the same effect as in the examples in Figs. 12 and 13 can be obtained.

[0091] FIG. 19 illustrates a trajectory P7(P) of the spot of the laser beam L on the surface Wa. In this example, the trajectory P7 has an oval endless section Pe and a plurality of spots Pp arranged inside the endless section Pe. In this case, the outer diameter of the welded portion 14 when it is formed in a dot shape or the width of the welded portion 14 when it is formed in a line shape is set to 30 [μm] or more and 300 [μm] or less, and the input energy is set to 1.0 [J] or less. Also in this example, the latest molten pool M formed in the latest spot Pp is set to partially overlap with the previous molten pool M (or welded portion 14) formed in the previous spot Pp. In order to obtain such overlap, a part of the spot Pp is set to partially overlap with a portion of the spot Pp that has already been irradiated and melted by irradiation with the laser beam L. Also in this example, the inside of the endless section Pe is in a state where it is filled with the molten pool M (welded portion 14).

[0092] Fig. 20 illustrates a locus P8(P) of the spot of the laser light L on the surface Wa. In this example, the locus P8 has a shape similar to that of the example locus P7 in Fig. 19, except that it does not have the elliptical endless section Pe. In this way, even if there is no endless section Pe, a good joining state without fractures 14a or breaks can be obtained by setting appropriate conditions for the multiple spots Pp.

[0093] As described above, through intensive research by the inventors, it has been found that, according to the welding method of this embodiment, by appropriately setting various parameters when irradiating a spot of laser light L, a suitable joining state free from fracture 14a, disconnection, and non-joining can be obtained.

[0094] [Second embodiment] 21 is a schematic configuration diagram of a laser welding apparatus 100A according to the second embodiment. In this embodiment, an optical head 120 has a DOE 125 between a collimator lens 121-2 and a filter 124. Except for this point, the laser welding apparatus 100A has a similar configuration to the laser welding apparatus 100 according to the first embodiment.

[0095] The DOE 125 shapes the shape of the beam B1 of the first laser light (hereinafter referred to as the beam shape). As conceptually illustrated in Fig. 22, the DOE 125 has a configuration in which, for example, a plurality of diffraction gratings 125a with different periods are overlapped. The DOE 125 can shape the beam shape by bending the parallel light in a direction influenced by each diffraction grating 125a or by overlapping the diffraction gratings. The DOE 125 can also be called a beam shaper.

[0096] The optical head 120 may have a beam shaper provided after the collimator lens 121-1 for adjusting the beam shape of the first laser light, and a beam shaper provided after the filter 124 for adjusting the beam shapes of the first laser light and the second laser light. By appropriately adjusting the beam shape of the laser light L with the beam shaper, a better joining state can be obtained.

[0097] FIG. 23 shows an example of a beam spot obtained by the laser welding apparatus 100A. In the example of FIG. 23, due to beam shaping by the DOE 125, a plurality of beam B2 spots are arranged in an approximately arc shape (approximately annular shape) around one beam B1 spot on the surface Wa. In such a case, the width w (spot diameter) of the beam spot is defined as the distance between the centers of two beams that are most distant in the direction perpendicular to the sweep direction SD, as shown in FIG. 23. In addition, by making the beam pattern approximately axially symmetrical as in the example of FIG. 23, it is not necessary to rotate the optical head 120 in accordance with the trajectory P when sweeping along a curved path, and therefore sweeping can be performed more efficiently, and the device configuration of the optical head 120 can be simplified and the optical head 120 can be controlled more easily.

[0098] [Third embodiment] 24 is a schematic diagram of a laser welding apparatus 100B of the third embodiment. In this embodiment, the optical head 120 does not have a galvano scanner 126, and is configured to be able to change the relative position with respect to the workpiece W in order to sweep the laser light L while irradiating the surface Wa of the workpiece W with the laser light L. The relative movement between the optical head 120 and the workpiece W can be achieved by moving the optical head 120, moving the workpiece W, or moving both the optical head 120 and the workpiece W. With this laser welding apparatus 100B, the same effects as those of the above-mentioned embodiments can be obtained.

[0099] Although the embodiment of the present invention has been illustrated above, the above embodiment is merely an example and is not intended to limit the scope of the invention. The above embodiment can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the gist of the invention. In addition, the specifications of each configuration, shape, and the like (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be appropriately changed and implemented.

[0100] For example, the present invention can be applied to lithium ion battery cells having configurations different from those of the above-described embodiment, and can also be applied to batteries other than lithium ion battery cells. Also, a battery is an example of an electrical product, and the electrical product of the present invention is not limited to a battery. Also, a battery terminal is an example of an electrical component, and the electrical component of the present invention is not limited to a battery terminal.

[0101] The object to be processed may also be a metal plate having a thin layer of another metal on its surface, such as a plated metal sheet. [Explanation of symbols]

[0102] 1...Batteries (electrical appliances) 10...Metal laminate (laminate, electrical parts) 11...Metal parts 11a...End surface (first surface) 12...Metal foil 13p…Cathode material 13m…Negative electrode material 14…Welded section 14a…rupture 14b...residue 14c…Gap 15…Separator 20…Exterior material 20a…Containment room 100, 100A, 100B...Laser welding device (welding device) 111...Laser device (first laser oscillator) 112...Laser device (second laser oscillator) 120...Optical head 121, 121-1, 121-2...Collimating lenses 122...Condenser lens 123…Mirror 124…Filter 125...DOE (diffractive optical element) 125a...Diffraction grating 126...Galvanometer scanner 126a, 126b…Mirror 130...Optical fiber B…boundary B1…Beam (first spot) B1a…Outer edge B2…Beam (second spot) B2a…Outer edge B2b…area B2f…area C...center point D1…Spot diameter (outer diameter) D2: Spot diameter (outer diameter) L: Laser light Lc...(reference point) movement trajectory M…Molten pool P,P1~P8…Trajectory (sweep trajectory) Pe: Endless section Pes…Starting point Pee…End point Pl: Linear section Pls…Start point Ple…End point Pp…Spot Pw...Wobbling section SD…Sweep direction T…part w…width W…Processing target Wa…Surface Wb…Back side X…direction (second direction) Y...Direction Z…direction (first direction)

Claims

1. A welding method for welding a metal member and a plurality of metal foils overlapping each other in a first direction by irradiating a laser beam including a first laser beam and a second laser beam having an energy density lower than that of the first laser beam to a metal foil on an opposite side of the metal member, the metal member and the plurality of metal foils being welded together, forming a molten pool across the plurality of metal foils and the metal member by irradiating the laser light; solidifying the molten pool to form a weld; having In the step of forming the molten pool, The spot of the laser light is swept over the surface of the metal foil, The welding method, wherein the energy absorbed by the plurality of metal foils and the metal member from the laser light is 0.14 [J / mm] or less per unit length in the sweep direction.

2. The welding method according to claim 1 , wherein the absorbed energy is equal to or greater than a level at which a metal foil in contact with the metal member among the plurality of metal foils can melt.

3. 3. The welding method according to claim 2, wherein the absorbed energy is 0.05 [J / mm] or more when a thickness of the plurality of metal foils stacked in the first direction is 400 [μm] or more.

4. 4. The welding method according to claim 1, wherein a sweep speed of the spot is 300 mm / s or more and 10,000 mm / s or less.

5. 5. The welding method according to claim 1, wherein the first laser beam has a wavelength of 800 nm or more and 1200 nm or less, and the second laser beam has a wavelength of 550 nm or less.

6. 6. The welding method according to claim 5, wherein the second laser light has a wavelength of 400 nm or more and 500 nm or less.

7. The welding method according to any one of claims 1 to 6, wherein the laser light beam is shaped by a beam shaper.

8. The method of claim 7 , wherein the beam shaper is a DOE.

9. 9. The welding method according to claim 1, wherein in the process of forming the molten pool, a sweep trajectory of the spot on the metal foil is set so that at least a portion of the sweep trajectory overlaps with a portion of the spot that has already been melted by irradiation with the laser light.

10. The welding method of claim 9 , wherein the sweep trajectory includes an endless portion.

11. The method of claim 10 , wherein the sweep trajectory has a generally endless shape.

12. 12. The welding method according to claim 10 or 11, wherein in the process of forming the molten pool, after the endless portion is formed in the sweep trajectory, the spot of the laser light is swept in an area inside the endless portion on the surface.

13. The welding method according to any one of claims 9 to 12, wherein the sweep trajectory includes a plurality of sections extending adjacent to each other.

14. The welding method according to any one of claims 9 to 13, wherein the sweep trajectory includes a line segment section connecting two points on the sweep trajectory.

15. The welding method according to any one of claims 9 to 14, wherein the sweep trajectory includes a spiral section.

16. The welding method according to any one of claims 9 to 15, wherein the sweep trajectory includes a wobbling section in which the reference point moves in the second direction while the spot revolves around the reference point.

17. The welding method according to claim 16 , wherein the sweep trajectory includes a section extending linearly in the second direction, and the wobbling section that is swept after the linearly extending section and partially overlaps with the linearly extending section.

18. The welding method according to any one of claims 9 to 17, wherein the sweep trajectories include a portion where the sweep trajectories intersect with each other.

19. The welding method according to any one of claims 1 to 18, wherein the width of the welded portion formed is 30 μm or more and 300 μm or less.

20. A welding method for welding a metal member and a plurality of metal foils overlapping each other in a first direction by irradiating a laser beam including a first laser beam and a second laser beam having an energy density lower than that of the first laser beam to a metal foil on an opposite side of the metal member, the metal member and the plurality of metal foils being welded together, forming a molten pool across the plurality of metal foils and the metal member by irradiating the laser light; solidifying the molten pool to form a weld; having In the step of forming the molten pool, a welding method in which an outer diameter of the weld formed when a point-shaped spot of the laser light is irradiated onto a metal foil of the plurality of metal foils opposite the metal member, or a width of the weld formed when the spot of the laser light is swept onto a metal foil of the plurality of metal foils opposite the metal member, is 30 μm or more and 300 μm or less.

21. A welding method for welding a metal member and a plurality of metal foils overlapping each other in a first direction by irradiating a laser beam including a first laser beam and a second laser beam having an energy density lower than that of the first laser beam to a metal foil on an opposite side of the metal member, the metal member and the plurality of metal foils being welded together, forming a molten pool across the plurality of metal foils and the metal member by irradiating the laser light; solidifying the molten pool to form a weld; having In the step of forming the molten pool, Irradiating a point-shaped spot of the laser light onto a metal foil of the plurality of metal foils on an opposite side to the metal member; A welding method, wherein the input energy of the laser light to the plurality of metal foils and the metal members is 1.0 [J] or less.

22. 22. The welding method according to claim 21, wherein the input energy is equal to or greater than the amount by which a metal foil in contact with the metal member among the plurality of metal foils can be melted.

23. A welding method for welding a metal member and a plurality of metal foils overlapping each other in a first direction by irradiating a laser beam including a first laser beam and a second laser beam having an energy density lower than that of the first laser beam to a metal foil on an opposite side of the metal member, the metal member and the plurality of metal foils being welded together, forming a molten pool across the plurality of metal foils and the metal member by irradiating the laser light; solidifying the molten pool to form a weld; having In the step of forming the molten pool, The spot of the laser light is swept over the surface of the metal foil, a sweep trajectory of the spot on the metal foil including a wobbling section in which the spot revolves around a reference point while the reference point moves in a second direction, and a section extending linearly in the second direction and partially overlapping with the wobbling section.

24. A metal member; A plurality of metal foils overlapped in a first direction on the metal member; a welded portion formed by welding the metal member and the plurality of metal foils; Equipped with A metal laminate, wherein the outer diameter of the welded portion when formed in a dot shape, or the width of the welded portion when formed in a line shape, of the metal foil on the opposite side of the metal member among the plurality of metal foils is 30 μm or more and 300 μm or less.

25. An electrical component comprising the metal laminate according to claim 24 as a conductor.

26. An electrical product comprising the metal laminate according to claim 24 as a conductor.

Images