Welding method, welding apparatus, metal laminate, electrical component, and electrical product

Abstract

In a welding method in which a metal member is welded with a plurality of metal foils, for example, by irradiating a laser light including first laser light of a wavelength of 800 [nm] or more and 1200 [nm] or less and second laser light of a wavelength of 500 [nm] or less from an opposite side of the metal member to the plurality of metal foils overlapped in a first direction on a first face of the metal member, the laser light is irradiated on a second face of a metal foil of the plurality of metal foils farthest from the metal member in the first direction on an opposite side of the metal member. In addition, in the welding method, the wavelength of the second laser light can be 400 [nm] or more and 500 [nm] or less.

Description

Technical Field

[0001] This invention relates to welding methods, welding apparatus, metal laminates, electrical components, and electrical products. Background Technology

[0002] Previously, batteries were known to be joined by laser welding of multiple tabs and terminals (e.g., Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-4643 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In this type of welding, it is important to ensure the required joint strength and to prevent welding defects such as spatter or porosity from occurring on the workpiece.

[0008] Therefore, one of the objectives of this invention is, for example, to obtain a new and improved welding method and welding apparatus capable of welding a laminate formed by overlapping multiple metal foils and metal components, as well as a metal laminate, electrical component, and electrical product welded using the welding method or welding apparatus.

[0009] Solution for solving the problem

[0010] In the welding method of the present invention, for example, the metal component is welded to the plurality of metal foils by irradiating a laser from the opposite side of the metal component onto a plurality of metal foils overlapping in a first direction on a first surface of the metal component. The laser includes a first laser with a wavelength of 800 nm or more and 1200 nm or less and a second laser with a wavelength of 550 nm or less. The laser is irradiated onto the second surface of the metal foil that is furthest from the metal component in the first direction on the side opposite to the metal component.

[0011] In the welding method, the wavelength of the second laser may be above 400 nm and below 500 nm.

[0012] In the welding method, the laser may also scan the second surface in a scanning direction along a second direction intersecting the first direction, and at least a portion of the second spot formed on the second surface by the second laser is located in front of the first spot formed on the second surface by the first laser in the scanning direction.

[0013] In the welding method, the first spot and the second spot may at least partially overlap on the second surface.

[0014] In the welding method, the second outer edge of the second light spot may surround the first outer edge of the first light spot on the second surface.

[0015] In the welding method, the ratio of the first energy density of the first laser on the second surface to the second energy density of the second laser on the second surface may be greater than 1 and less than 10.

[0016] In the welding method, the ratio of the first energy density of the first laser on the second surface to the second energy density of the second laser on the second surface may be 2 or more and 8 or less.

[0017] In the welding method, the ratio of the first energy density of the first laser on the second surface to the second energy density of the second laser on the second surface may be greater than 1 and less than 10.

[0018] In the welding method, the metal component and the plurality of metal foils may be made of any one of copper-based metal materials, aluminum-based metal materials, nickel-based metal materials, iron-based metal materials, and titanium-based metal materials.

[0019] In the welding method, the thickness of the metal component in the first direction may be 0.05 mm or more and 2.0 mm or less, and the thickness of the plurality of metal foil layers may be 0.05 mm or more and 2.0 mm or less.

[0020] The welding apparatus of the present invention includes: a laser oscillator; and an optical head that irradiates a plurality of metal foils overlapping on a first surface of a metal member along a first direction from the opposite side of the metal member with laser light from the laser oscillator. The welding apparatus welds the metal member to the plurality of metal foils. The laser light includes a first laser with a wavelength of 800 nm or more and 1200 nm or less, and a second laser with a wavelength of 500 nm or less. The optical head irradiates the laser light onto a second surface of the metal foil that is furthest from the metal member in the first direction, on the side opposite to the metal member.

[0021] Alternatively, the welding apparatus may include a beam shaper that splits the laser into multiple beams.

[0022] Alternatively, the welding apparatus may include an electrical scanner that alters the emission direction of the laser by moving the laser on a second surface of the metal foil furthest from the metal member among the plurality of metal foils on the side opposite to the metal member in a scanning direction along a second direction intersecting the first direction.

[0023] In the metal laminate of the present invention, for example, it includes: a metal member having a first surface; a plurality of metal foils overlapping the first surface along a first direction; and a welding portion formed by welding the metal member to the plurality of metal foils, the welding portion having: a welding metal extending toward the metal member from a second surface of the metal foil furthest from the metal member in the first direction on the side opposite to the metal member; and a heat-affected portion located around the welding metal, the welding metal having: a first portion; and a second portion having a larger average cross-sectional area of ​​grains in a cross section along the first direction compared to the first portion.

[0024] In the metal laminate, for example, the average cross-sectional area of ​​the grains included in the second portion may be more than 1.8 times the average cross-sectional area of ​​the grains included in the first portion.

[0025] In the metal laminate, for example, the welded portion may extend along a second direction that intersects the first direction.

[0026] In the metal laminate of the present invention, for example, there is a metal member and a plurality of metal foils overlapping the metal member, and it has a first surface opposite to the metal member, a second surface on the back side of the first surface, and a weld portion extending along the first surface, wherein the weld portion has: a weld metal extending from the first surface toward the second surface; and a heat-affected zone located around the weld metal, wherein the first grain boundary number ratio is expressed as the following formula (3-1).

[0027] Rb1=N12 / N11 (3-1)

[0028] Here, Rb1 is the first grain boundary ratio, N11 is the number of grain boundaries intersecting a straight test line of a predetermined length along the first surface in a test section orthogonal to the first surface and along the extension direction of the weld, and N12 is the number of grain boundaries intersecting a straight test line of the predetermined length extending in a direction orthogonal to the first surface in the test section. The weld metal has: a third portion located at a position separated from the first surface in a thickness direction from the first surface toward the second surface; and a fourth portion located between the third portion and the first surface, wherein the first grain boundary ratio of the fourth portion is lower than the first grain boundary ratio of the third portion.

[0029] In the metal laminate of the present invention, for example, there is a metal member and a plurality of metal foils overlapping the metal member, and it has a first surface opposite to the metal member, a second surface on the back side of the first surface, and a weld portion extending along the first surface, wherein the weld portion has: a weld metal extending from the first surface toward the second surface; and a heat-affected zone located around the weld metal, wherein the second grain boundary ratio is expressed as the following formula (3-2).

[0030] Rb2=max(N22 / N21, N21 / N22) (3-2)

[0031] Here, Rb2 is the second grain boundary ratio, N21 is the number of grain boundaries in the test section orthogonal to the first surface and along the extension direction of the weld, intersecting a straight test line of a predetermined length extending in a first direction between the direction along the first surface and the direction orthogonal to the first surface, and N22 is the number of grain boundaries in the test section intersecting a straight test line of the predetermined length extending in a second direction orthogonal to the first direction. max(N22 / N21, N21 / N22) is set to (N22 / N21) when (N22 / N21) is greater than (N21 / N22), and is set to (N21 / N22) when (N22 / N21) is less than (N21 / N22). The weld metal has: a third portion located at a position separated from the first surface in the thickness direction from the first surface toward the second surface; and a fourth portion located between the third portion and the first surface, wherein the second grain boundary ratio of the fourth portion is higher than the second grain boundary ratio of the third portion.

[0032] In the metal laminate of the present invention, for example, there is a metal member and a plurality of metal foils overlapping the metal member, and it has a first surface opposite to the metal member, a second surface on the back side of the first surface, and a weld portion extending along the first surface, wherein the weld portion has: a weld metal extending from the first surface toward the second surface; and a heat-affected zone located around the weld metal, wherein the first grain boundary ratio is expressed as the following formula (3-1).

[0033] Rb1=N12 / N11 (3-1)

[0034] Here, Rb1 is the first grain boundary ratio, N11 is the number of grain boundaries intersecting a straight test line of a predetermined length along the first surface in a test section orthogonal to the first surface and along the extension direction of the weld, and N12 is the number of grain boundaries intersecting the straight test line of the predetermined length extending in a direction orthogonal to the first surface in the test section.

[0035] Furthermore, when the second grain boundary ratio Rb2 is expressed as equation (3-2),

[0036] Rb2=max(N22 / N21, N21 / N22) (3-2)

[0037] Here, Rb2 is the second grain boundary ratio, N21 is the number of grain boundaries in the test section orthogonal to the first surface and along the extension direction of the weld, intersecting with a straight test line of a predetermined length extending in a first direction between the direction along the first surface and the direction orthogonal to the first surface, N22 is the number of grain boundaries in the test section intersecting with a straight test line of the predetermined length extending in a second direction orthogonal to the first direction, and max(N22 / N21, N21 / N22) is (N21 / N22) in (N22 / N21). In the above cases, it is set as (N22 / N21), and when (N22 / N21) is less than (N21 / N22), it is set as (N21 / N22). The weld metal has: a third portion located at a position separated from the first surface in the thickness direction from the first surface toward the second surface; and a fourth portion located between the third portion and the first surface, wherein the first grain boundary ratio of the fourth portion is lower than the first grain boundary ratio of the third portion and the second grain boundary ratio of the fourth portion is higher than the second grain boundary ratio of the third portion.

[0038] The electrical components of the present invention, for example, include the aforementioned metal laminate as a conductor.

[0039] The electrical products of the present invention, for example, include the aforementioned metal laminate as a conductor.

[0040] Invention Effects

[0041] According to the present invention, for example, it is possible to obtain a new and improved welding method and welding apparatus capable of welding laminates formed by overlapping multiple metal foils and metal components, as well as metal laminates, electrical components and electrical products welded using the welding method or welding apparatus. Attached Figure Description

[0042] Figure 1 This is an exemplary schematic structural diagram of the laser welding apparatus according to the first embodiment.

[0043] Figure 2 This is an exemplary and schematic cross-sectional view of a metal laminate that is the object of processing in the laser welding apparatus of the first embodiment.

[0044] Figure 3 This is an exemplary and schematic cross-sectional view of a battery that includes a metal laminate that is the object of processing, as described in the laser welding apparatus of the first embodiment.

[0045] Figure 4 This is an exemplary schematic diagram showing the laser beam (spot) formed on the surface of the workpiece by the laser welding apparatus of the first embodiment.

[0046] Figure 5 It is a graph showing the absorption rate of various metallic materials for light of different wavelengths of laser light.

[0047] Figure 6 This is an illustrative and schematic cross-sectional view of the welded portion in the embodiment.

[0048] Figure 7 This is an illustrative and schematic cross-sectional view showing a portion of the welded portion of an embodiment.

[0049] Figure 8 This is a graph showing the relationship between the power ratio of the second laser generated by the laser welding apparatus of the embodiment relative to the power of the first laser, i.e., the output ratio, and the sputtering suppression rate.

[0050] Figure 9 yes Figure 2 A magnified view of a portion of it.

[0051] Figure 10 This is an explanatory diagram showing the application of a first reference line to a location in the cross-section of the welded portion of the embodiment.

[0052] Figure 11This is an explanatory diagram showing the application of a second reference line at one location in the cross-section of the welded portion of the embodiment.

[0053] Figure 12 This is an exemplary schematic structural diagram of the laser welding apparatus according to the second embodiment.

[0054] Figure 13 This is an explanatory diagram illustrating the concept of the diffractive optical element included in the laser welding apparatus of the second embodiment.

[0055] Figure 14 This is an exemplary schematic structural diagram of the laser welding apparatus according to the third embodiment.

[0056] Figure 15 This is an exemplary schematic structural diagram of the laser welding apparatus according to the fourth embodiment.

[0057] Figure 16 This is an exemplary schematic structural diagram of the laser welding apparatus according to the fifth embodiment.

[0058] Figure 17 This is a schematic diagram showing an example of a laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus of the fifth embodiment.

[0059] Figure 18 This is a schematic diagram showing an example of a laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus of the fifth embodiment. Detailed Implementation

[0060] Hereinafter, exemplary embodiments of the present invention are disclosed. The structure of the embodiments shown below, as well as the effects and results (effects) brought about by such structures, are examples. The present invention can also be implemented with structures other than those disclosed in the following embodiments. Furthermore, according to the present invention, at least one of various effects (including derived effects) obtained through the structure can be obtained.

[0061] The embodiments shown below have the same structure. Therefore, based on the structure of each embodiment, the same function and effect can be obtained based on the same structure. In addition, there are cases where these identical structures are labeled with the same reference numerals and repeated descriptions are omitted.

[0062] In addition, in each figure, the arrow X represents the X direction, the arrow Y represents the Y direction, and the arrow Z represents the Z direction. The X, Y, and Z directions intersect and are orthogonal. The X direction is the scanning direction SD, and the Y direction is the scanning width direction. Furthermore, the Z direction is the normal direction of the surface Wa (processed surface, welding 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.

[0063] In addition, the ordinal numbers in this specification are used expediently to distinguish parts, components, locations, lasers, directions, etc., and do not indicate priority or order.

[0064] [First Implementation Method]

[0065] Figure 1 This is a schematic structural diagram of the laser welding apparatus 100 according to the first embodiment. Figure 1 As shown, 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.

[0066] Laser devices 111 and 112 each have a laser oscillator and are configured, for example, to output laser power of several kW. Laser devices 111 and 112 emit laser light with wavelengths of 380 nm or higher and 1200 nm or lower. Laser devices 111 and 112 internally include laser sources such as fiber lasers, semiconductor lasers (elements), YAG lasers, and disk lasers. Laser devices 111 and 112 can also be configured to output multimode laser light with a combined power of several kW as the output of multiple light sources.

[0067] Laser device 111 outputs a first laser beam with a wavelength of 800 nm or more and 1200 nm or less. Laser device 111 is an example of a first laser device. As an example, laser device 111 has a fiber laser or a semiconductor laser (element) as the laser source. The laser oscillator included in laser device 111 is an example of a first laser oscillator.

[0068] On the other hand, the laser device 112 outputs a second laser with a wavelength of 500 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 source. The laser device 112 preferably outputs a second laser with a wavelength of 400 nm or more and 500 nm or less. The laser oscillator included in the laser device 112 is an example of a second laser oscillator.

[0069] Fiber 130 guides the laser output from laser devices 111 and 112 to the laser-guided optical head 120.

[0070] The optical head 120 is an optical device used to irradiate the workpiece W with laser light input from the laser devices 111 and 112. The optical head 120 includes a collimating lens 121, a condenser lens 122, a reflector 123, and a filter 124. The collimating lens 121, the condenser lens 122, the reflector 123, and the filter 124 can also be referred to as optical components.

[0071] The optical head 120 is configured to change its relative position with the workpiece W in order to simultaneously irradiate the workpiece W with the laser L and scan the laser 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.

[0072] It should be noted that the optical head 120 can also be configured to scan the laser L on the surface Wa by means of an electrical scanner (galvanoscanner) not shown.

[0073] Collimating lenses 121 (121-1, 121-2) collimate the laser light input via optical fiber 130. The collimated laser light becomes parallel light.

[0074] The reflector 123 reflects the first laser light, which has become parallel light through the collimating lens 121-1. The first laser light reflected by the reflector 123 travels in the opposite direction of the Z-direction and goes to the filter 124. It should be noted that in a structure where the first laser light is input in the opposite direction of the Z-direction in the optical head 120, the reflector 123 is not required.

[0075] Filter 124 is a high-pass filter that allows the first laser to pass through but blocks the second laser, instead reflecting it. The first laser passes through filter 124 and travels in the opposite direction of the Z-direction, heading towards condenser lens 122. On the other hand, filter 124 reflects the second laser, which has become parallel light after passing through collimating lenses 121-2. The second laser, reflected by filter 124, travels in the opposite direction of the Z-direction and towards condenser lens 122.

[0076] The focusing lens 122 focuses the first and second lasers, which are parallel beams, and directs them as laser L (output light) onto the workpiece W.

[0077] The processing object W is a metal laminate 10 formed by stacking a metal component 11 and multiple metal foils 12 along the Z direction. The metal laminate 10 is an example of a laminate. The metal laminate 10 has a metal component 11, multiple metal foils 12, and a welding part 14. The welding part 14 mechanically and electrically connects the metal component 11 and the multiple metal foils 12.

[0078] Figure 2 This is a cross-sectional view of the metal laminate 10. The metal member 11, as an example, has a plate-like shape that extends intersecting the Z direction. However, the metal member 11 is not limited to a plate-like member. A plurality of metal foils 12 are laminated along the Z direction on the Z-direction end face 11a of the metal member 11.

[0079] When the metal laminate 10 is welded by the laser welding apparatus 100, it is temporarily fixed in the aforementioned laminated state by a fixing clamp (not shown), and is positioned such that the normal direction of the surface Wa of the metal foil 12 is approximately parallel to the Z direction. The fixing clamp is, for example, two metal plates arranged separately along the Z direction. These two metal plates clamp the laminated metal component 11 and the plurality of metal foils 12 along the Z direction in an orientation intersecting the Z direction. The metal plate facing the optical head 120 of these two metal plates is provided with a through hole through which the laser L can pass. This through hole has a slit-like shape that extends elongatedly in the scanning direction SD (X direction).

[0080] Surface Wa is the Z-direction end face of the metal laminate 10, and is the side of the metal foil 12 furthest from the metal member 11 among the plurality of metal foils 12, opposite to the metal member 11. Laser L is irradiated relative to surface Wa in the opposite direction to the Z-direction; in other words, it is irradiated relative to surface Wa from the side opposite to the metal member 11 along the Z-direction. It should be noted that the side of the metal member 11 opposite to the end face 11a is the back surface Wb of the metal laminate 10. Surface Wa is the irradiation surface of laser 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. End face 11a is an example of a first surface, and surface Wa is an example of a second surface. Furthermore, surface Wa is also an example of a first surface, and back surface Wb is an example of a second surface.

[0081] Irradiation by laser L causes the weld portion 14 to extend from surface Wa in the opposite direction to the Z direction. This opposite direction to the Z direction can also be referred to as the depth direction of the weld portion 14. Furthermore, laser L scans the surface Wa along the X direction (scanning direction SD), thereby allowing the weld portion 14 to extend in the direction opposite to the Z direction. Figure 2 The roughly identical cross-sectional shape also extends along the X direction. The X direction is an example of the second direction. It can also be referred to as the long side direction or the extension direction of the weld 14. In addition, the Y direction can also be referred to as the width direction of the weld 14.

[0082] The weld portion 14 includes weld metal 14a. Weld metal 14a extends from surface Wa toward metal member 11. Weld metal 14a has a first portion 14a1 and a second portion 14a2. The first portion 14a1 is mainly formed by irradiation with a first laser, and the second portion 14a2 is mainly formed by irradiation with a second laser. Figure 2In the example, the second portion 14a2 extends from the surface Wa in the opposite direction to the Z direction. The second portion 14a2 is adjacent to the first portion 14a1 in the Z direction. That is, the first portion 14a1 is adjacent to the second portion 14a2 in the opposite direction to the Z direction. The second portion 14a2 is formed within at least a plurality of metal foils 12. The first portion 14a1 extends within the range of the plurality of metal foils 12 and the metal member 11. In addition, the weld metal 14a, as a whole, does not penetrate the metal laminate 10 along the Z direction. It should be noted that the shape of the weld metal 14a is not limited to such a shape. The structure of the weld metal 14a, including the first portion 14a1 and the second portion 14a2, will be described in detail later.

[0083] Figure 3 This is a cross-sectional view of a battery 1, which is an electrical product having a metal laminate 10. The battery 1 is an application example of the metal laminate 10. In this case, the metal laminate 10 is an example of an electrical component that is a conductor, and an example of an electrical component included in the electrical product. The electrical component can also be referred to as a constituent component of the electrical product.

[0084] Figure 3 The battery 1 shown is, for example, a laminated lithium-ion battery cell. Battery 1 has two membrane-like outer components 20. A receiving chamber 20a is formed between the two outer components 20. Multiple flat positive electrode elements 13p, multiple flat negative electrode elements 13m, and multiple flat separators 15 are housed within the receiving chamber 20a. Within the receiving chamber 20a, the positive electrode elements 13p and negative electrode elements 13m are alternately stacked with separators 15 present between them. Metal foils 12 extend from the multiple positive electrode elements 13p and the multiple negative electrode elements 13m, respectively. Figure 3 In this example, multiple metal foils 12 extending from the positive electrode 13p overlap the metal member 11 at their ends on opposite sides of the battery 1 in the Y direction. A metal laminate 10, formed by welding the metal member 11 and the multiple metal foils 12, is provided at these ends. On the positive electrode side, only a portion of the metal member 11 is exposed outside the outer casing 20; the other portion of the metal member 11, the multiple metal foils 12, and the welded portion 14 are not exposed outside the outer casing 20. The metal member 11 constitutes the positive terminal of the battery 1. On the other hand, multiple metal foils 12 extending from the negative electrode 13m overlap the metal member 11 at their ends in the Y direction of the battery 1. A metal laminate 10, formed by welding the metal member 11 and the multiple metal foils 12, is provided at these ends. On the negative electrode side, only a portion of the metal member 11 is exposed outside the outer casing 20; the other portion of the metal member 11, the multiple metal foils 12, and the welded portion 14 are also not exposed outside the outer casing 20. The metal member 11 constitutes the negative terminal of the battery 1.

[0085] like Figure 3As shown, the metal laminate 10 is sandwiched between two outer components 20. An airtight or liquid-tight seal is ensured between the metal laminate 10 and the outer components 20 by a sealing element or the like. Therefore, the surface Wa and back surface Wb of the metal laminate 10 are preferably as small, few, or nonexistent as possible. Regarding this point, according to the welding method of this embodiment, as will be described in detail later, the occurrence of welding defects can be suppressed, thus reducing the unevenness of the surface Wa caused by welding defects. Therefore, the metal laminate 10 welded using the welding method of this embodiment is preferred for the positive and negative terminals of the battery 1. It should be noted that 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 and negative terminals are examples of electrical components. The metal laminate 10 or metal component 11 can also be referred to as an electrode tab or electrode lug. In addition, the metal component 11 can also be referred to as a conductive component.

[0086] Figure 4 This is a schematic diagram showing the laser beam (spot) L illuminating the surface Wa. Beams B1 and B2 each have a Gaussian power distribution, for example, in the radial direction of a section orthogonal to their optical axes. However, the power distributions of beams B1 and B2 are not limited to a Gaussian shape. Furthermore, as... Figure 4 Therefore, in the diagrams representing beams B1 and B2 by circles, the diameter of the circle representing beam B1 and B2 is the beam diameter of each beam B1 and B2. The beam diameter of each beam B1 and B2 is defined as including the peak value of the beam and being 1 / e of the peak intensity. 2 The diameter of the region with the above intensity. It should be noted that, although not illustrated, in the case of a non-circular beam, it is possible to obtain 1 / e of the peak intensity in the direction perpendicular to the scanning direction SD. 2 The length of the region with the above intensity is defined as the beam diameter. Additionally, the beam diameter on surface Wa is called the spot diameter.

[0087] like Figure 4 As shown, in this embodiment, as an example, the laser beam L is formed on surface Wa as follows: the beam B1 of the first laser overlaps with the beam B2 of the second laser, beam B2 is larger (wider) than beam B1, and the outer edge B2a of beam B2 surrounds the outer edge B1a of beam B1. In this case, the spot diameter D2 of beam B2 is larger than the spot diameter D1 of beam B1. On surface Wa, beam B1 is an example of a first spot, and beam B2 is an example of a second spot.

[0088] In addition, in this embodiment, such as Figure 4As shown, on surface Wa, the laser beam (spot) has a point-symmetric shape with respect to the center point C, so the shape of the spot is the same in any scanning direction SD. Therefore, when a moving mechanism is provided to move the optical head 120 relative to the workpiece W for scanning the laser L on surface Wa, the moving mechanism only needs to have a mechanism that can move in parallel with the workpiece, and there are cases where a mechanism that can rotate relative to the workpiece can be omitted.

[0089] The metal component 11 and metal foil 12, which are the objects of processing W, can be made of conductive metal materials. Examples of such metal materials include copper-based metals, aluminum-based metals, nickel-based metals, iron-based metals, and titanium-based metals. Specifically, these include copper, copper alloys, aluminum, aluminum alloys, tin, nickel, nickel alloys, iron, stainless steel, titanium, and titanium alloys. The metal component 11 and metal foil 12 can be made of the same material or different materials.

[0090] [Wavelength and light absorption rate]

[0091] Here, we will explain the light absorption rate of metallic materials. Figure 5 This is a graph showing the absorption rate of various metallic materials for the wavelength of the irradiated laser L. Figure 5 The horizontal axis of the graph represents wavelength, and the vertical axis represents absorbance. Figure 5 The relationship between wavelength and absorbance is shown for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti).

[0092] Although the properties vary depending on the material, regarding Figure 5 For the metals shown, it can be understood that the absorption rate of blue or green lasers (second lasers) is higher than that of lasers using conventional infrared (IR) light (first laser). This characteristic becomes more pronounced in copper (Cu), gold (Au), and the like.

[0093] When a laser is irradiated onto a workpiece W with a relatively low absorption rate for the wavelength used, most of the light energy is reflected and does not contribute as heat to the workpiece W. Therefore, to obtain a sufficiently deep molten region, a relatively high power is required. In this case, energy is rapidly injected into the center of the beam, resulting in sublimation and the formation of a keyhole.

[0094] On the other hand, when a laser is irradiated onto a workpiece W with a high absorption rate for the wavelength used, most of the applied energy is absorbed by the workpiece W and converted into heat energy. That is, no excessive power is required, so there is no formation of pinholes, and it becomes a heat-conductive melting process.

[0095] In this embodiment, the wavelengths of the first laser, the second laser, and the material of the workpiece W are selected such that the absorption rate of the workpiece W to the second laser is higher than its absorption rate to the first laser. In this case, the scanning direction is... Figure 4 In the case of the scanning direction SD shown, under the scanning action of the laser L spot, the second laser beam B2 is first used to... Figure 4 The region B2f in front of the SD in the process irradiates the welded part (hereinafter referred to as the welded part) of the workpiece W with a second laser. Then, the first laser beam B1 is irradiated into the welded part, and then the welded part is irradiated again with the second laser beam B2 in the region B2b located behind the scanning direction SD.

[0096] Therefore, at the welding site, a heat-conducting molten region is first generated by irradiation with a second laser in region B2f, which has a higher absorptivity. Then, at the welding site, a deeper pinhole-type molten region is generated by irradiation with a first laser. In this case, a heat-conducting molten region is pre-formed at the welding site, thus allowing the formation of a molten region of the required depth using a lower-power first laser compared to the case where no such molten region is formed. Furthermore, at the welding site, the molten state is changed by irradiation with a second laser in region B2b, which has a higher absorptivity. From this perspective, the wavelength of the second laser is preferably set to 550 nm or less, more preferably 500 nm or less.

[0097] Furthermore, through the experimental research of the inventors, it has been confirmed that the use of Figure 4 In welding irradiated by such a laser beam L, welding defects such as sputtering and porosity can be reduced. This can be presumed to be because, by preheating the workpiece W with region B2f of beam B2 before beam B1 arrives, the molten pool of workpiece W formed by beams B2 and B1 is more stable.

[0098] Furthermore, through experimental research by the inventors, it was determined that if the temperature of the metal foil 12 is higher than the temperature of the metal component 11 due to laser L irradiation, sometimes multiple metal foils 12 stretch and flex and bend away from the metal component 11 under the action of thermal expansion, creating gaps between the multiple metal foils 12 and the metal component 11. Only the multiple metal foils 12 are then welded, or they are welded while gaps remain between the multiple metal foils 12 and the metal component 11. The inventors also discovered that by setting appropriate conditions, welding in a state where such gaps have occurred can be prevented. These preferred conditions will be described later.

[0099] [Welding Method]

[0100] In the welding process using the laser welding apparatus 100, firstly, a metal laminate 10, formed by temporarily fixing a metal component 11 and multiple metal foils 12 together using a retainer, is positioned such that it is irradiated onto a surface Wa by a laser L. Then, while the surface Wa is irradiated by the laser L, which includes beams B1 and B2, the laser L is moved relative to the metal laminate 10. Thus, while the laser L irradiates the surface Wa, it moves along the scanning direction SD on the surface Wa (scanning). The portion irradiated by the laser L melts and then solidifies as the temperature decreases, thereby welding the metal component 11 and the multiple metal foils 12 together, and the metal laminate 10 becomes integrated.

[0101] [Cross-section of the welded part]

[0102] Figure 6 This is a cross-sectional view of the welded portion 14 formed on the workpiece W. Figure 6 This is a cross-sectional view perpendicular to the scanning direction SD (X direction) and along the thickness direction (Z direction). The weld portion 14 is along the scanning direction SD, i.e., perpendicular to... Figure 6 It extends perpendicularly to the paper surface. It should be noted that... Figure 6 The cross-section of the welded portion 14 formed on a copper plate of thickness 2 mm is shown. It can be inferred that the welded portion 14, formed by the metal laminate 10 of the overlapping metal members 11 and multiple metal foils 12 along the Z direction, has a shape similar to... Figure 6 The shape of the welded part 14 formed as a metal material processing object W is roughly the same as that shown.

[0103] like Figure 6 As shown, the weld portion 14 has weld metal 14a extending from the surface Wa in the opposite direction to the Z direction, and a heat-affected zone 14b surrounding the weld metal 14a. The weld metal 14a is a portion formed by melting and then solidifying under the irradiation of a laser L. The weld metal 14a can also be referred to as a molten and solidified portion. The heat-affected zone 14b is a portion formed by heat affecting the base material of the workpiece W, and is an unmelted portion.

[0104] The width of the weld metal 14a along the Y direction becomes narrower the further away from the surface Wa. That is, the cross-section of the weld metal 14a has a conical shape that tapers in the opposite direction toward the Z direction.

[0105] Furthermore, through detailed analysis of the cross-section by the inventors, it was determined that the weld metal 14a includes a first portion 14a1 away from the surface Wa and a second portion 14a2 between the first portion 14a1 and the surface Wa.

[0106] The first region 14a1 is obtained by melting through a small aperture created by irradiation with the first laser, and the second region 14a2 is obtained by melting through irradiation with region B2b located behind the scanning direction SD in the beam B2 of the second laser. Analysis based on the EBSD (electron backscatter diffraction pattern) method revealed that the grain sizes in the first region 14a1 and the second region 14a2 are different. Specifically, in a cross-section orthogonal to the X direction (scanning direction SD), the average cross-sectional area of ​​the grains in the second region 14a2 is larger than the average cross-sectional area of ​​the grains in the first region 14a1.

[0107] The inventors confirmed that when only the first laser beam B1 is irradiated onto the workpiece W, i.e., when the region B2b located behind the scanning direction SD in the beam B2 is not irradiated, the second portion 14a2 is not formed, and the first portion 14a1 extends deeper from the surface Wa in the opposite direction to the Z direction. That is, in this embodiment, it can be presumed that the second portion 14a2 is formed near the surface Wa by irradiation of the region B2b located behind the scanning direction SD in the beam B2, therefore the first portion 14a1 is formed relative to the second portion 14a2 on the side opposite to the surface Wa, in other words, at a position separated from the surface Wa in the opposite direction to the Z direction.

[0108] Figure 7 This is a cross-sectional view showing a portion of the welded part 14. Figure 7 The grain boundaries obtained by the EBSD method are shown. Additionally, in Figure 7 In this example, grain A with a grain size of 13 μm or less is painted black. It should be noted that 13 μm is not a threshold for physical properties, but rather a threshold set for the analysis of the experimental results. Furthermore, according to... Figure 7 It is clearly known that grain A is more abundant in the first region 14a1 and less abundant in the second region 14a2. That is, the average cross-sectional area of ​​the grains in the second region 14a2 is larger than the average cross-sectional area of ​​the grains in the first region 14a1. The inventors have confirmed through experimental analysis that the average cross-sectional area of ​​the grains in the second region 14a2 is more than 1.8 times the average cross-sectional area of ​​the grains in the first region 14a1.

[0109] like Figure 7As shown in region I, these relatively small grains A are densely packed at locations separating from the surface Wa in the Z direction, extending elongatedly in the Z direction. Furthermore, analysis at multiple locations at different positions in the X direction (scanning direction SD) confirms that the densely packed region of grain A also extends along the scanning direction SD. Since the welding was performed simultaneously with the scan, it can be inferred that the crystallization in the scanning direction SD forms the same morphology.

[0110] In cases where it is difficult to distinguish between the first part 14a1 and the second part 14a2 based on the appearance or hardness distribution in the cross-section, it is also possible to... Figure 6 , 7 The first region Z1 and the second region Z2, geometrically determined based on the position and width wb of the weld metal 14a in the surface Wa, are respectively designated as the first part 14a1 and the second part 14a2. As an example, the first region Z1 and the second region Z2 are quadrilateral-shaped regions extending along the Z direction with a width wm (equal width in the Y direction) in a section orthogonal to the scanning direction SD. The second region Z2 can be defined as a region extending along the Z direction from the surface Wa to a depth d. The first region Z1 can be defined as a region deeper than the depth d, in other words, a region on the side opposite to the surface Wa in relation to the depth d. The width wm can, for example, be set to 1 / 3 of the width wb (average weld width) of the weld metal 14a on the surface Wa, and the depth d (height, thickness) of the second region Z2 can, for example, be set to 1 / 2 of the width wb. Furthermore, the depth of the first region Z1 can, for example, be set to 3 times the depth d of the second region Z2. Through experimental analysis of multiple samples, the inventors confirmed that, under the given settings of the first region Z1 and the second region Z2, the average cross-sectional area of ​​the grains in the second region Z2 is larger than the average cross-sectional area of ​​the grains in the first region Z1, by more than 1.8 times. This determination also serves as evidence that the first portion 14a1 and the second portion 14a2 are formed in the weld metal 14a through welding.

[0111] Furthermore, the inventors experimentally analyzed the ratio of the energy density of the first laser on surface Wa to the energy density of the second laser on surface Wa. Here, for each laser, the effective energy density E on surface Wa is defined by the following equation (1).

[0112] E n =Am×P n / (D n ×V) (1)

[0113] Here, E n For effective energy density [J / mm 2 ], Am is the absorption rate of the material W to be processed, P nFor the output [W] of the laser based on the laser device, D n Let Wa be the diameter of the laser spot on the surface [mm], and V be the scanning speed [mm / s]. Here, the subscript n is used to distinguish the parameters, where n=1 represents the parameters of the first laser and n=2 represents the parameters of the second laser.

[0114] Therefore, the ratio R of the effective energy density E1 of the first laser to the effective energy density E2 of the second laser on the surface Wa is expressed by the following equation (2).

[0115] R = E1 / E2 (2)

[0116] It should be noted that the ratio R is a dimensionless number. Effective energy density E1 is an example of the first energy density, and effective energy density E2 is an example of the second energy density.

[0117] The inventors conducted experiments under various conditions, including a ratio R of 2 or higher and 47 or lower, and irradiation with only the first laser and only the second laser. Based on their experimental analysis, the inventors determined that, from the perspectives of suppressing sputtering, suppressing porosity in the metal foil 12, and achieving a penetration depth above the threshold of the weld 14, a ratio R is preferably 1 or higher and 10 or lower, and more preferably 2 or higher and 8 or lower. Furthermore, regarding the gap between the plurality of metal foils 12 and the metal member 11, it was determined that when the ratio R is as low as 1, the heat applied to the plurality of metal foils 12 by the second laser irradiation does not reach the metal member 11; instead, the plurality of metal foils 12 are primarily heated, causing them to stretch, flex, and bend, thus creating the gap. In other words, the inventors discovered that by setting the ratio R to 1 or higher, the generation of a gap between the plurality of metal foils 12 and the metal member 11 can be prevented.

[0118] Regarding the ratio R, specifically, when 50 sheets of oxygen-free copper foil 12 with a thickness of 8 μm are overlapped and welded to the metal component 11, the optimal welding state with minimal sputtering and porosity is obtained when the output of the first laser beam B1 is 500 W or more, the output of the second laser beam B2 is 100 W or more, and the ratio R is approximately 6. Furthermore, when 100 sheets of oxygen-free copper foil 12 with a thickness of 8 μm are overlapped and welded to the metal component 11, the optimal welding state with minimal sputtering and porosity is obtained when the output of the first laser beam B1 is 1000 W or more, the output of the second laser beam B2 is 400 W or more, and the ratio R is approximately 3.7.

[0119] Furthermore, the inventors conducted experimental analysis on cases where the thickness of the metal component 11 in the Z direction is within a practically envisioned range, i.e., 0.05 mm or more and 2.0 mm or less, and the thickness of the layers of the plurality of metal foils 12 in the Z direction is also within a practically envisioned range, i.e., 0.05 mm or more and 2.0 mm or less. If the thickness of the metal component 11 and the layers of the plurality of metal foils 12 is thin, heat diffusion is suppressed, and therefore, when irradiated with a laser, material sublimation due to a rapid temperature rise may occur, leading to material breakage. Regarding this point, the inventors confirmed through this experimental analysis that if the thickness of the metal component 11 and the layers of the plurality of metal foils 12 in the Z direction is 0.05 mm or more, such breakage will not occur.

[0120] [Suppression of sputtering caused by the output ratio of the first laser to the second laser]

[0121] Figure 8 This is a graph showing the relationship between the power of the second laser (Pw2) and the power of the first laser (Pw1), i.e., the output ratio (Rp = Pw2 / Pw1), and the sputtering suppression rate. Here, the sputtering suppression rate Rs is defined by the following equation (3).

[0122] Rs=1-Nh / Nir (3)

[0123] Here, Nh represents the number of sputtered particles generated within a specified area when both the first and second lasers are applied, and Nir represents the number of sputtered particles generated within the specified area when only the first laser is applied at the same power as Nh. Additionally, Figure 8 The results of multiple experiments were shown at various output ratios. The line segment corresponding to the output ratio represents the range of deviations in sputtering suppression rate among multiple samples (at least 3 samples) at that output ratio, and □ represents the median sputtering suppression rate for each output ratio.

[0124] like Figure 8 As shown, through the inventors' experimental research, it has been determined that the output ratio Rp being 0.1 or more and less than 0.18 is preferred (○), the output ratio being 0.18 or more and less than 0.3 is more preferred (◎), and the output ratio being 0.3 or more and less than 2 is even more preferred (◎◎).

[0125] [Differences in location due to grain orientation]

[0126] Figure 9 yes Figure 2 A magnified image of a portion. This was determined through experimental research by the inventors, such as... Figure 9As shown, in the welded portion 14 formed by irradiation from both the first and second lasers, the orientation (long side direction, growth direction) of the grains differs depending on the depth from the surface Wa. This is believed to be due to the different grain growth patterns during solidification between the third portion 14a3, obtained by melting through a small aperture generated by irradiation from the first laser, and the fourth portion 14a4, obtained by melting through irradiation from the region B2b located behind the scanning direction in the beam B2 of the second laser. Here, the third portion 14a3 is located away from the surface Wa and corresponds to the first portion 14a1 described above. The fourth portion 14a4 is located between the third portion 14a3 and the surface Wa and corresponds to the second portion 14a2 described above.

[0127] In order to numerically represent such a structure, the inventors defined an index representing the orientation (long side direction) of the grains in each part of the welded portion 14, based on A.2: Cutting method of JIS G 0551:2020.

[0128] Specifically, such as Figure 9 As shown, in the cross-sectional image, two reference lines, R1 and R2, are used, including two mutually orthogonal straight test lines. Figure 9 In the diagram, the first reference line R1 is represented by a solid line, and the second reference line R2 is represented by a dashed line. The first reference line R1 has two mutually orthogonal diameters of the reference circle R0 as straight test lines L11 and L12. One straight test line L11 extends along the X direction (scanning direction) of surface Wa, and the other straight test line L12 extends in the Z direction orthogonal to surface Wa. Similarly, the second reference line R2 has two mutually orthogonal diameters of the same reference circle R0 as the first reference line R1 as straight test lines L21 and L22. One straight test line L21 extends in a direction between the X and Z directions, and the other straight test line L22 extends in a direction between the opposite direction of the X direction and the Z direction, or in a direction between the opposite direction of the Z direction and the X direction. The angle difference between straight test lines L11 and L21 is 45° or 135°, and the angle difference between straight test lines L12 and L22 is also 45° or 135°. The length of the diameter of the reference circle R0, i.e. the length of the straight test lines L11, L12, L21, L22, is, for example, the length corresponding to 200 [μm] (an example of the specified length), but it can be appropriately set according to the size of the grain.

[0129] Furthermore, at each point P within the welded portion 14, the first reference line R1 and the second reference line R2 are applied, and the first grain boundary ratio Rb1 and the second grain boundary ratio Rb2 are calculated using the following formulas (3-1) and (3-2).

[0130] Rb1=N12 / N11 (3-1)

[0131] Rb2=max(N22 / N21, N21 / N22) (3-2)

[0132] Here, N11 is the number of grains intersecting the straight test line L11, and N12 is the number of grains intersecting the straight test line L12. N21 is the number of grains intersecting the straight test line L21, and N22 is the number of grains intersecting the straight test line L22. The number of grains can also be referred to as the grain boundary number. Furthermore, in equation (3-2), when (N22 / N21) is greater than or equal to (N21 / N22), max(N22 / N21, N21 / N22) is (N22 / N21), and when (N22 / N21) is less than (N21 / N22), max(N22 / N21, N21 / N22) is (N21 / N22). In actual measurements, the above measurements are performed at any specified location, for example, at 10 or more locations, in a microscope photograph of the XZ section taken at 50x magnification, and the average values ​​can be set as Rb1 and Rb2 respectively. It should be noted that if any one of N11, N12, N21, and N22 at a point P within the welded part 14 becomes 0, the number of grain boundaries at point P can be excluded from the calculation of Rb1 and Rb2.

[0133] Figure 10 , 11 This illustrates the case where the first reference line R1 is applied to a point P within the cross-section of the welded portion 14. Figure 10 ) and the case where the second baseline R2 is applied ( Figure 11 A schematic diagram illustrating (e.g.) Figure 10 , 11 As shown, the number of intersections between grain A (grain boundary) and the linear experimental lines L11, L12, L21, and L22 varies. Figure 10 , 11 In the example, the angle difference between the straight experimental line L21 and grain A is relatively small, therefore the grain boundary number N21 is smaller than the other grain boundary numbers N11, N12, and N22. Therefore, Figure 10 , 11 The point P shown in the example is called the point P where the second grain boundary ratio Rb2 is higher than the first grain boundary ratio Rb1. Similarly, in the above definition, at the point P where the angle difference between the long side direction of grain A and the X direction within the reference circle R0 is relatively small, the first grain boundary ratio Rb1 is relatively high and larger than the second grain boundary ratio Rb2. Furthermore, at the point P where the angle difference between the long side direction of grain A and the direction between the X and Z directions (45° direction) is relatively small, the second grain boundary ratio Rb2 is relatively high and larger than the first grain boundary ratio Rb1.

[0134] Through experimental research by the inventors, it was determined that the first grain boundary ratio Rb1 at each point P in the fourth region 14a4 is lower than that at each point P in the third region 14a3. Furthermore, it was determined that the second grain boundary ratio Rb2 at each point P in the fourth region 14a4 is higher than that at each point P in the third region 14a3. Additionally, it was determined that at each point P in the third region 14a3, the first grain boundary ratio Rb1 is higher than the second grain boundary ratio Rb2, and at each point P in the fourth region 14a4, the second grain boundary ratio Rb2 is higher than the first grain boundary ratio Rb1. The presence of such differences in the first grain boundary ratio Rb1 and the second grain boundary ratio Rb2 within the weld portion 14 is considered an important factor in achieving strong weld strength in the workpiece W, and serves as evidence that welding based on both first and second laser irradiation has been performed.

[0135] As explained above, in the welding method of this embodiment, for example, a laser L is irradiated from the opposite side of the metal member 11 along the Z direction (first direction) relative to the multiple metal foils 12 stacked on the end face 11a (first face) of the metal member 11, in other words, in the opposite direction of the Z direction. Thus, a metal laminate 10 formed by welding the metal member 11 and the multiple metal foils 12 via the welding section 14 is obtained.

[0136] Assuming that when welding the metal component 11 and all the plurality of metal foils 12 using a laser L irradiated onto the metal component 11, the molten area (melt pool) forming the weld portion 14 needs to penetrate from the metal component 11 through all the plurality of metal foils 12. In this case, welding defects may occur such that if the output of the laser L is too low, the weld portion 14 does not reach the metal foil 12 away from the metal component 11 and the metal foil 12 is not joined, or conversely, if the output of the laser L is too high, the metal foil 12 away from the metal component 11 breaks. Regarding this point, according to the structure and method of this embodiment, as described above, by irradiating the metal foil 12 with the laser L from the opposite side of the metal component 11 to form the weld portion 14, it is easier to form the weld portion 14 that penetrates through the plurality of metal foils 12 and reaches the metal component 11, and the aforementioned defects that occur when the laser L is irradiated onto the metal component 11 can be avoided. In addition, if a pinhole-type molten state is initially generated in the layer of the plurality of metal foils 12 due to laser irradiation, welding defects such as porosity in the metal foil 12 may occur. Regarding this point, in this embodiment, from the initial irradiation of the plurality of metal foils 12 by the laser, a heat-conducting molten state caused by the action of the second laser is obtained in the layer of the plurality of metal foils 12, thus avoiding welding defects such as pores in the metal foils 12.

[0137] In addition, in this embodiment, for example, the wavelength of the second laser is 400 nm or more and 500 nm or less.

[0138] Based on such a structure and method, for example, it is possible to obtain a higher quality metal laminate 10 with less or no sputtering material and without producing pores in the metal foil 12.

[0139] In addition, in this embodiment, for example, on the surface Wa, at least a portion of the second laser beam B2 (second spot) is located in front of the first laser beam B1 (first spot) in the scanning direction SD.

[0140] In addition, in this embodiment, for example, on surface Wa, beam B1 and beam B2 overlap at least partially.

[0141] In addition, in this embodiment, for example, on surface Wa, beam B2 is wider than beam B1.

[0142] In addition, in this embodiment, for example, on the surface Wa, the outer edge B2a (second outer edge) of the beam B2 surrounds the outer edge B1a (first outer edge) of the beam B1.

[0143] As described above, the inventors have confirmed that welding performed by irradiation with a laser L beam having such beams B1 and B2 formed on the surface Wa can further reduce sputtering and porosity. This can be presumed to be because, as described above, by preheating the workpiece W with the region B2f of beam B2 before the arrival of beam B1, the molten pool of the workpiece W formed by beams B2 and B1 is more stable. Therefore, with a laser L having such beams B1 and B2, for example, welding with higher quality and less sputtering and porosity can be performed. In addition, with such beams B1 and B2, for example, the advantage of lower power of the first laser can also be obtained. Furthermore, when beams B1 and B2 are irradiated coaxially, the advantage of not requiring relative rotation between the optical head 120 and the workpiece W can also be obtained.

[0144] Furthermore, in this embodiment, for example, the ratio of the effective energy density E1 (first energy density) of the first laser on surface Wa to the effective energy density E2 (second energy density) of the second laser on surface Wa (second surface) is 1 or more and 10 or less.

[0145] Based on such a structure and method, for example, it is possible to obtain a higher quality metal laminate 10.

[0146] In addition, in this embodiment, for example, the workpiece W is made of any one of copper-based metals, aluminum-based metals, nickel-based metals, iron-based metals, and titanium-based metals.

[0147] The effects of the welding method of this embodiment can be obtained when the workpiece W is made of any of the above-mentioned materials.

[0148] [Second Implementation]

[0149] Figure 12 This is a schematic structural diagram of the laser welding apparatus 100A according to the second embodiment. In this embodiment, the optical head 120 has a DOE 125 between the collimating lens 121-1 and the reflecting mirror 123. Apart from this, the laser welding apparatus 100A has the same structure as the laser welding apparatus 100 of the first embodiment.

[0150] The shape of the first laser beam B1 formed by the DOE125 (hereinafter referred to as beam shape). Figure 13 As conceptually illustrated, the DOE 125 has, for example, a structure formed by overlapping multiple diffraction gratings 125a with different periods. The DOE 125 can shape a beam by bending or aligning parallel light in the directions affected by the individual diffraction gratings 125a. The DOE 125 can also be referred to as a beam shaper.

[0151] It should be noted that the optical head 120 may also include a beam shaper disposed at the rear end of the collimating lens 121-2 to adjust the beam shape of the second laser, or a beam shaper disposed at the rear end of the filter 124 to adjust the beam shapes of the first and second lasers. By using the beam shaper to properly adjust the beam shape of the laser L, the generation of sputtering and porosity can be further suppressed during welding.

[0152] [Third Implementation Method]

[0153] Figure 14 This is a schematic structural diagram of the laser welding apparatus 100B according to the third embodiment. In this embodiment, the optical head 120 has an electrical scanner 126 between the filter 124 and the condenser lens 122. Apart from this, the laser welding apparatus 100B has the same structure as the laser welding apparatus 100 of the first embodiment.

[0154] The electronic scanner 126 has two reflectors 126a and 126b, and is a device that can move the irradiation position of the laser L and scan the laser L without moving the optical head 120 by controlling the angles of the two reflectors 126a and 126b. The angles of the reflectors 126a and 126b are changed, for example, by a motor (not shown). With this structure, a mechanism that does not require relative movement between the optical head 120 and the workpiece W can be obtained, which has advantages such as miniaturization of the device structure.

[0155] [Fourth Implementation Method]

[0156] Figure 15 This is a schematic structural diagram of the laser welding apparatus 100C according to the fourth embodiment. In this embodiment, the optical head 120 has a DOE 125 (beam shaper) between the collimating lenses 121-2 and the filter 124. Apart from this, the laser welding apparatus 100C has the same structure as the laser welding apparatus 100B of the third embodiment. With this structure, the same effects as the third embodiment based on the presence of the electronic scanner 126 can be obtained, as well as the same effects as the second embodiment based on the presence of the DOE 125 (beam shaper).

[0157] It should be noted that, in this embodiment, the optical head 120 may also have a beam shaper disposed at the rear end of the collimating lens 121-1 to adjust the beam shape of the first laser, a beam shaper disposed at the rear end of the filter 124 to adjust the beam shape of the first laser and the second laser, etc.

[0158] [Fifth Implementation]

[0159] Figure 16This is a schematic structural diagram of the laser welding apparatus 100D according to the fifth embodiment. In this embodiment, the optical head 120 includes a first portion 120-1 that irradiates the first laser L1 and a second portion 120-2 that irradiates the second laser L2, each consisting of a separate main body (housing). With this structure, the same functions and effects as in the above-described embodiments can be obtained.

[0160] Figure 17 , 18 Examples of laser beams B1 and B2 formed on surface Wa using a laser welding apparatus 100D are shown. Figure 17 , 18 As shown, according to the laser welding apparatus 100D, the relative positions of beams B1 and B2 can be arbitrarily set by setting the relative positions and orientations of the first part 120-1 and the second part 120-2. Through the inventors' research, it has been determined that on the surface Wa... Figure 17 , 18 When at least a portion of beam B2 (the second spot) is positioned ahead of beam B1 (the first spot) in the scanning direction SD, and when beams B1 and B2 are in contact with each other or at least partially overlap, the same preheating effect as in the first embodiment can be obtained based on beam B2. Furthermore, it has been determined that even when at least a portion of beam B2 is positioned ahead of beam B1 in the scanning direction SD, beams B1 and B2 can still be separated by a small distance. It should be noted that... Figure 17 , 18 Each is just one example; the configuration of beams B1 and B2 obtained using the laser welding device 100D, and the dimensions of each beam B1 and B2, are not limited to... Figure 17 , 18 Examples.

[0161] The above embodiments of the present invention have been illustrated, but these embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other ways, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the specifications of various structures, shapes, etc. (construction, type, orientation, model, size, length, width, thickness, height, number, configuration, position, material, etc.) can be appropriately modified for implementation.

[0162] For example, the present invention can also be applied to lithium-ion battery cells with structures different from those described above, and can also be applied to batteries other than lithium-ion battery cells. Furthermore, a battery is an example of an electrical product, and the electrical product of the present invention is not limited to a battery. Additionally, the terminals of a battery are an example of an electrical component, and the electrical component of the present invention is not limited to the terminals of a battery.

[0163] Alternatively, when scanning the workpiece with a laser, known techniques such as wobbling, weaving, and output modulation can be used for scanning, and the surface area of ​​the molten pool can be adjusted.

[0164] Alternatively, the laser can be scanned multiple times on the object being processed. In this case, it is also possible to [1] make the power of the laser in the subsequent scan lower or higher than the power of the laser in the previous scan, or [2] make the scanning speed in the subsequent scan faster or slower than the scanning speed in the previous scan, or [3] make the power of the laser in the subsequent scan higher than the power of the laser in the previous scan, and make the scanning speed in the subsequent scan faster than the scanning speed in the previous scan.

[0165] Alternatively, the workpiece can also have a thin layer of other metals on its surface, similar to a plated metal sheet.

[0166] Industrial applicability

[0167] This invention can be applied to welding methods, welding apparatus, metal laminates, electrical components, and electrical products.

[0168] Explanation of reference numerals in the attached figures

[0169] 1 Battery (electrical product), 10 Metal laminate (laminated body, electrical component), 11 Metal component, 11a End face (first face), 12 Metal foil, 13p Positive electrode, 13m Negative electrode, 14 Welding part, 14a Welding metal, 14a1 First part, 14a2 Second part, 14a3 Third part, 14a4 Fourth part, 14b Heat-affected part, 15 Separator, 20 Outer casing, 20a Housing, 100, 100A~100D Laser welding apparatus (welding apparatus), 111 Laser device (first laser oscillator), 112 Laser device (second laser oscillator), 1 20 Optical head, 120-1 First part, 120-2 Second part, 121, 121-1, 121-2 Collimating lenses, 122 Condenser lens, 123 Mirror, 124 Filter, 125 DOE (Diffractive Optical Element), 125a Diffraction grating, 126 Electronic scanner, 126a, 126b Mirrors, 130 Optical fiber, A-crystal, Am absorptivity, B1 beam (first spot), Bla outer edge, B2 beam (second spot), B2a outer edge, B2b region, B2f region, C-center point, D1 spot diameter (outer diameter), D2 spot diameter (outer diameter), D nSpot diameter, d depth, E effective energy density, E1 effective energy density (first energy density), E2 effective energy density (second energy density), I region, L laser, L1 first laser, L2 second laser, L11, L12, L21, L22 straight test lines, N11, N12, N21, N22 grain boundary numbers, P point, P n Output, R ratio, R0 reference circle, R1 first reference line, R2 second reference line, Rb1 first grain boundary number ratio, Rb2 second grain boundary number ratio, SD scan direction, V scan speed, W processing object, Wa surface (second side), Wb back side, wb (width on the surface of the weld metal), wm (width of the first and second regions), X direction (second direction), Y direction, Z direction (first direction), Z1 first region (first part), Z2 second region (second part).

Claims

1. A welding method comprising welding the metal component to the plurality of metal foils by irradiating a plurality of metal foils overlapping on a first surface of the metal component along a first direction with a laser from the opposite side of the metal component to form a weld metal spanning the plurality of metal foils and the metal component, wherein, The metal components and the plurality of metal foils are respectively made of any one of copper-based metals, aluminum-based metals, nickel-based metals, iron-based metals, and titanium-based metals. The laser includes a first laser with a wavelength of 800 nm or more and 1200 nm or less, and a second laser with a wavelength of 550 nm or less. The laser is irradiated onto the second surface of the metal foil furthest from the metal member in the first direction, on the side opposite to the metal member, and scanned on the second surface. On the second surface, 1 / e of the peak intensity of the first laser 2 The entire area of ​​the first intensity region mentioned above is equal to 1 / e of the peak intensity of the second laser. 2 The above-mentioned second intensity regions overlap, and the second intensity region has a region that does not overlap with the first intensity region and is located in front of the first intensity region in the scanning direction, and a region that does not overlap with the first intensity region and is located behind the first intensity region in the scanning direction. The second laser is used to perform thermal conductivity melting on at least a portion of the second side of the plurality of metal foils, thereby forming a second portion of the weld metal that terminates within the plurality of metal foils, and the first laser is used to generate a pinhole melting, thereby forming a first portion of the weld metal that extends into the metal member from a position adjacent to the second portion on the side opposite to the second side relative to the second portion.

2. The welding method according to claim 1, wherein, The thickness of the metal component in the first direction is 0.05 mm or more and 2.0 mm or less, and the thickness of the layers of the plurality of metal foils is 0.05 mm or more and 2.0 mm or less.

3. The welding method according to claim 1 or 2, wherein, The laser is irradiated onto the second surface while being rotated, swung horizontally, or modulated.

4. The welding method according to claim 1 or 2, wherein, The laser is scanned multiple times on the second surface.

5. The welding method according to claim 1 or 2, wherein, The laser is scanned on the second surface, and the scanning speed on the second surface is changed midway through the scan.

6. The welding method according to claim 1 or 2, wherein, The laser is scanned on the second surface, and the power of the laser is changed midway through the scan on the second surface.

7. The welding method according to claim 1 or 2, wherein, The metal component includes a plated metal sheet.

8. The welding method according to claim 1 or 2, wherein, On the second surface, the second spot formed by the second laser on the second surface is wider than the first spot formed by the first laser on the second surface.

9. The welding method according to claim 1 or 2, wherein, The laser irradiates the second surface with the normal direction of the second surface being approximately parallel to the first direction.

10. The welding method according to claim 1 or 2, wherein, On the second surface, the shape of the light spot formed by the laser on the second surface has a point-symmetric shape with respect to the center of the light spot.

11. The welding method according to claim 1 or 2, wherein, The first laser and the second laser irradiate each other on the same axis.

12. The welding method according to claim 1 or 2, wherein, On the second surface, the center of the first light spot formed on the second surface by the first laser is approximately the same as the center of the second light spot formed on the second surface by the second laser.

13. The welding method according to claim 1 or 2, wherein, On the second surface, the first light spot formed on the second surface by the first laser and the second light spot formed on the second surface by the second laser are offset from each other.

14. A welding apparatus comprising: Laser oscillator; and An optical head that irradiates a plurality of metal foils overlapping along a first direction on a first surface of a metal component with laser light from the opposite side of the metal component. The welding apparatus welds the metal component to the plurality of metal foils by forming a weld metal spanning the plurality of metal foils and the metal component. in, The metal components and the plurality of metal foils are respectively made of any one of copper-based metals, aluminum-based metals, nickel-based metals, iron-based metals, and titanium-based metals. The laser includes a first laser with a wavelength of 800 nm or more and 1200 nm or less, and a second laser with a wavelength of 500 nm or less. The optical head irradiates the laser onto the second surface of the metal foil that is furthest from the metal member in the first direction, on the side opposite to the metal member, and scans the second surface. On the second surface, 1 / e of the peak intensity of the first laser 2 The entire area of ​​the first intensity region mentioned above is equal to 1 / e of the peak intensity of the second laser. 2 The above-mentioned second intensity regions overlap, and the second intensity region has a region that does not overlap with the first intensity region and is located in front of the first intensity region in the scanning direction, and a region that does not overlap with the first intensity region and is located behind the first intensity region in the scanning direction. The second laser is used to perform thermal conductivity melting on at least a portion of the second side of the plurality of metal foils, thereby forming a second portion of the weld metal that terminates within the plurality of metal foils, and the first laser is used to generate a pinhole melting, thereby forming a first portion of the weld metal that extends into the metal member from a position adjacent to the second portion on the side opposite to the second side relative to the second portion.

15. The welding apparatus according to claim 14, wherein, The welding apparatus includes a beam shaper that splits the laser into multiple beams.

16. The welding apparatus according to claim 14 or 15, wherein, The welding apparatus includes an electrical scanner that changes the emission direction of the laser by moving the laser on the second surface in a scanning direction along a second direction intersecting the first direction.

17. The welding apparatus according to claim 14 or 15, wherein, The optical head illuminates the second surface while simultaneously rotating, swaying, or modulating the output of the laser.

18. The welding apparatus according to claim 14 or 15, wherein, The optical head illuminates the first laser and the second laser on the same axis.

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