Welding method and welding equipment

Abstract

To obtain a welding method which dispenses with processing for differently removing a plating layer before welding even if a plurality of conductors including a metal conductor in which, for example, the plating layer is formed, are welded, welding equipment and a welding structure of the metal conductor.SOLUTION: In a welding method for performing welding by irradiating laser beams on surfaces of processing objects being a plurality of metal conductors including at least one metal conductor in which, for example, a plating layer is formed, the laser beams include a first laser beam whose wave length is equal to or longer than 800[nm] and equal to or shorter than 1200[nm], and a second laser beam whose wave length is equal to or shorter than 500[nm], and the plating layer is removed by the irradiation of the second laser beam. In the welding method, the wave length of the second laser beam may be equal to or longer than 400[nm] and equal to or shorter than 500[nm]. Also, in the welding method, the plating layer may be a tin-plated layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a welding method. and Welding Equipment Place Regarding. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known a welding method for welding together metal conductors such as bus bars and terminals by irradiating them with laser light (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-168340 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of welding, a plating layer may be formed on one of the metal conductors, and if the material forming the plating layer melts and gets into the welded part during welding, there is a risk that the joint strength will be weakened.

[0005] As a countermeasure, a process of removing the plating layer by irradiating a pulsed laser separately before welding has been performed, but in that case, there are problems in that the processing time is lengthened by the step of removing the plating layer, and the processing effort and cost increase.

[0006] Therefore, one of the objectives of the present invention is to provide a welding method, welding apparatus, and welding structure for a metal conductor that does not require a separate process for removing the plating layer before welding, even when welding multiple conductors including a metal conductor having a plating layer formed thereon. [Means for solving the problem]

[0007] The welding method of the present invention is a welding method for welding by irradiating laser light onto a surface of an object to be processed, which is, for example, a plurality of metal conductors including at least one metal conductor having a plating layer formed thereon, wherein the laser light includes a first laser light having a wavelength of 800 nm or more and 1200 nm or less, and a second laser light having a wavelength of 500 nm or less, and the plating layer is removed by irradiation of the second laser light.

[0008] In the welding method, for example, the second laser light has a wavelength of not less than 400 [nm] and not more than 500 [nm].

[0009] In the welding method, for example, the plating layer is a tin plating layer.

[0010] In the welding method, for example, at least one of the plurality of metal conductors is made of a copper-based material.

[0011] In the welding method, for example, the laser light is swept in a sweep direction on a surface of the laser light, and at least a portion of a second spot formed on the surface by the second laser light is located forward in the sweep direction of a first spot formed on the surface by the first laser light.

[0012] In the welding method, for example, the first spot and the second spot at least partially overlap on the surface.

[0013] In the welding method, for example, on the surface, a second outer edge of the second spot surrounds a first outer edge of the first spot.

[0014] In the welding method, for example, the power density of the second laser light on the surface is 0.16 [MW / cm 2 ] or more and 1.5 [MW / cm 2 ]below.

[0015] In the welding method, for example, a thickness of the metal conductor having the surface among the plurality of metal conductors is 0.5 [mm] or more and less than 1 [mm], a spot diameter of the first spot formed on the plane when the surface is a plane perpendicular to the laser light by the first laser light is 20 [μm] or more and 80 [μm] or less, a power of the first laser light is 0.3 [kW] or more and 6 [kW] or less, a spot diameter of the first spot formed on the plane when the surface is a plane perpendicular to the laser light by the second laser light is 50 [μm] or more and 400 [μm] or less, and a power of the second laser light is 0.05 [kW] or more and 1 [kW] or less.

[0016] In the welding method, for example, the energy density of the first laser beam per unit volume in the irradiation direction of the laser beam at the welded portion of the plurality of metal conductors is 200 [J / mm 3 ] or more, and the energy density of the second laser beam per unit volume in the irradiation direction of the laser beam at the welded portion is 5 [J / mm 3 ] or more and 49 [J / mm 3 ]below.

[0017] Furthermore, the welding apparatus of the present invention is, for example, a welding apparatus including a laser oscillator and an optical head that irradiates laser light from the laser oscillator onto a plurality of metal conductors including at least one metal conductor having a plating layer formed thereon, and welds the plurality of metal conductors, wherein the laser light includes a first laser light having a wavelength of 800 nm or more and 1200 nm or less, and a second laser light having a wavelength of 500 nm or less, and the plating layer is removed by irradiation of the second laser light.

[0018] The welding device includes, for example, a beam shaper that splits the laser light into a plurality of beams.

[0019] The welding device includes, for example, a galvanometer scanner that changes the irradiation direction of the laser light so as to sweep the laser light in a sweeping direction on the surface.

[0020] The welding device includes, for example, a detection mechanism that detects a deviation of a spot formed on the surface by the laser light from a predetermined position, and a correction mechanism that corrects the deviation.

[0021] In the welding apparatus, for example, the correction mechanism changes the relative positions of the plurality of metal conductors and the optical head.

[0022] In the welding apparatus, for example, the correction mechanism includes a galvanometer scanner that changes the irradiation direction of the laser light so as to sweep the laser light in a sweep direction on the surface.

[0023] Furthermore, the welded structure of a metal conductor of the present invention is, for example, a welded structure of a metal conductor including a plurality of metal conductors including at least one first metal conductor having a plating layer formed thereon, and a welded portion in which the plurality of metal conductors are welded together, wherein the welded portion has a weld metal extending from a surface of the welded structure of the metal conductor in a direction intersecting with the surface, and a heat-affected zone located around the weld metal, and the weld metal has a first portion and a second portion in which the average value of the cross-sectional area of ​​crystal grains in a cross section along the direction intersecting with the surface is larger than that of the first portion.

[0024] In a welded structure of the metal conductor, for example, the weld extends along the surface.

[0025] In a welded structure of the metal conductors, for example, the weld penetrates the first metal conductor and extends from the first metal conductor to another metal conductor.

[0026] In a welded structure of the metal conductors, for example, the weld extends along a boundary between the first metal conductor and another metal conductor adjacent to the first metal conductor.

[0027] In a welded structure of the metal conductors, for example, the weld extends across a boundary between the first metal conductor and another metal conductor adjacent to the first metal conductor. Effect of the Invention

[0028] According to the present invention, it is possible to obtain a welding method, welding apparatus, and welded structure for metal conductors, which do not require a separate process for removing the plating layer before welding, even when welding multiple conductors including a metal conductor having a plating layer formed thereon. [Brief description of the drawings]

[0029] [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 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 3] FIG. 3 is a graph showing the light absorptance of each metal material versus the wavelength of the irradiated laser light. [Figure 4] FIG. 4 is an exemplary schematic cross-sectional view of a welded portion according to an embodiment. [Diagram 5] FIG. 5 is an exemplary schematic cross-sectional view showing a part of a welded portion of the embodiment. [Figure 6] FIG. 6 is a graph showing experimental results of welding performed by the laser welding apparatus of the embodiment with different combinations of the power density of the first laser beam and the power density of the second laser beam. [Figure 7] FIG. 7 is an explanatory diagram showing the concept of the principle of the diffractive optical element included in the laser welding apparatus of the first embodiment. [Figure 8] FIG. 8 is a schematic plan view showing an example of a welded structure of a metal conductor according to an embodiment. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX of FIG. [Figure 10] FIG. 10 is a schematic plan view showing an example of a welded structure of a metal conductor according to an embodiment. [Figure 11] FIG. 11 is a cross-sectional view taken along line XI-XI of FIG. [Figure 12] FIG. 12 is a schematic plan view showing an example of a welded structure of a metal conductor according to an embodiment. [Figure 13] FIG. 13 is a cross-sectional view taken along line XIII-XIII of FIG. [Figure 14] FIG. 14 is a schematic plan view showing an example of a welded structure of a metal conductor according to an embodiment. [Figure 15] FIG. 15 is a schematic cross-sectional view showing an example of a welded structure of a metal conductor according to an embodiment, taken at the same position as FIG. [Figure 16] FIG. 16 is an exemplary schematic configuration diagram of the laser welding device according to the second embodiment. [Figure 17] FIG. 17 is an exemplary schematic configuration diagram of a laser welding device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] 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.

[0031] 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.

[0032] 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 a normal direction to the surface Wa (machined surface, welded surface) of the processing object W. In each figure, for convenience, an example is shown in which the sweep direction SD of the laser light L on the surface Wa is along the X direction, but the sweep direction SD only needs to be along the surface Wa and intersect with the Z direction, and is not limited to being along the X direction.

[0033] 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.

[0034] [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, an optical fiber 130, and a controller 141. The laser welding apparatus 100 is an example of a welding apparatus.

[0035] 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 irradiate laser light with a wavelength of 380 [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 the multiple light sources.

[0036] The laser device 111 outputs a first laser light having a wavelength of 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 is an example of a first laser oscillator.

[0037] On the other hand, the laser device 112 outputs a second laser light having 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 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 is an example of a second laser oscillator.

[0038] The optical fibers 130 guide the laser beams output from the laser devices 111 and 112 to the optical head 120 .

[0039] The optical head 120 is an optical device for irradiating 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, and a filter 124. The collimator lens 121, the condenser lens 122, the mirror 123, and the filter 124 may also be referred to as optical components.

[0040] The optical head 120 is configured to be able to change its position relative to the object W in order to sweep the laser light L while irradiating the laser light L on the surface Wa of the object W. The relative movement between the optical head 120 and the object W can be achieved by moving the optical head 120, moving the object W, or moving both the optical head 120 and the object W.

[0041] The optical head 120 may be configured to have a galvano scanner (not shown) or the like so as to be capable of sweeping the laser light L over the surface Wa.

[0042] 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.

[0043] The mirror 123 reflects the first laser light that has been collimated by the collimator lens 121-1. The first laser light reflected by the mirror 123 travels in the opposite Z direction toward the filter 124. Note that in a configuration in which the first laser light is input to the optical head 120 so as to travel in the opposite Z direction, the mirror 123 is not necessary.

[0044] 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 passes through filter 124 and travels in the opposite Z direction toward condenser lens 122. On the other hand, filter 124 reflects the second laser light that has been collimated by collimator lens 121-2. The second laser light reflected by filter 124 travels in the opposite Z direction toward condenser lens 122.

[0045] The condenser lens 122 condenses the first laser light and the second laser light as parallel light, and irradiates the object W to be processed with the condensed light as laser light L (output light).

[0046] Moreover, the laser welding apparatus 100 includes a controller 141 and a controlled mechanism whose operation is controlled by the controller 141. In this embodiment, the laser welding apparatus 100 includes, for example, a drive mechanism 150 as the controlled mechanism.

[0047] The driving mechanism 150 changes the relative position of the optical head 120 with respect to the workpiece W. The driving mechanism 150 has, for example, a rotation mechanism such as a motor, a speed reduction mechanism that reduces the rotation output of the rotation mechanism, and a motion conversion mechanism that converts the rotation reduced by the speed reduction mechanism into linear motion. The controller 141 can control the driving mechanism 150 so that the relative position of the optical head 120 with respect to the workpiece W in the X direction, Y direction, and Z direction is changed. The controller 141 may also control the operation of the laser devices 111, 112 and the camera 170.

[0048] The laser welding apparatus 100 also has a camera 170, and a filter 127 and a mirror 128 as optical components that guide light to the camera 170. The filter 127 is provided between the mirror 123 and the filter 124. The filter 127 transmits the first laser light from the mirror 123 toward the filter 124, and reflects light (e.g., visible light) from the surface Wa toward the mirror 128. The light reflected by the mirror 128 is input to the camera 170. With this configuration, the camera 170 can capture an image on the surface Wa. The image captured by the camera 170 may include, for example, an image of the surface Wa and an image of the beam (spot) of the laser light L. Therefore, the image captured by the camera 170 can be said to be a detection result of a deviation of the spot formed on the surface Wa from a predetermined position, and the camera 170 can be said to be an example of a sensor that detects the deviation. In addition, when the position of the spot in the angle of view of the captured image is fixed, the captured image only needs to include the target of irradiation with the laser light L, and does not need to include an image of the spot. Camera 170 and controller 141 are an example of a detection mechanism.

[0049] Moreover, the controller 141 can detect the deviation of the spot from a predetermined position from the image captured by the camera 170, and control the driving mechanism 150 to correct the deviation. The controller 141 may also execute feedback control so that the deviation falls within a predetermined threshold. The controller 141 and the driving mechanism 150 are an example of a correction mechanism. With such a configuration, the accuracy of the irradiation position of the laser light can be improved.

[0050] The workpiece W is a welded structure 10 having a plurality of metal conductors 11 and 12. The metal conductors 11 and 12 are joined by a weld 14.

[0051] When the welded structure 10 is welded by the laser welding apparatus 100, the welded structure 10 is temporarily fixed together by a fixing tool (not shown) and is set, for example, in a position in which the normal direction of the surface Wa is approximately parallel to the Z direction. In the configuration shown in Fig. 1, as an example, the surface Wa intersects with the Z direction at an end in the Z direction in the welded portion of the welded structure 10 and spreads out perpendicularly to the Z direction. The surface Wa can also be referred to as a surface irradiated with the laser light L.

[0052] The optical head 120 irradiates the laser light L toward the surface Wa in the opposite direction of the Z direction. The surface Wa is an irradiation surface of the laser light L, and may also be referred to as an opposing surface facing the optical head 120. The opposite direction of the Z direction may be referred to as the irradiation direction of the laser light L.

[0053] Such irradiation of the laser light L causes the welded portion 14 to extend from the surface Wa in the opposite direction to the Z direction. The opposite direction to the Z direction may also be referred to as the depth direction of the welded portion 14. The depth direction of the welded portion 14 is also the irradiation direction of the laser light L.

[0054] Furthermore, while the laser light L is being irradiated, the optical head 120 is moved in the sweep direction SD relative to the workpiece W by the operation of the drive mechanism 150, whereby the laser light L is swept in the sweep direction SD on the surface Wa. As a result, the welded portion 14 has a cross-sectional shape substantially similar to that of FIG. 1 and also extends in the sweep direction SD (X direction in FIG. 1) along the surface Wa. The sweep direction SD may also be referred to as the longitudinal direction or extension direction of the welded portion 14. Moreover, the direction intersecting the Z direction and the sweep direction SD (Y direction in FIG. 1) may also be referred to as the width direction of the welded portion 14.

[0055] FIG. 2 is a schematic diagram showing a beam (spot) of laser light L irradiated onto a flat 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. 2, the diameter of the circle representing beams 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 the intensity above 1 / e of the peak intensity in the direction perpendicular to the sweep direction SD (Y direction in the figure) is defined as the diameter of the region with the intensity above 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.

[0056] 2, in this embodiment, as an example, the beam of laser light L is formed such that a beam B1 of the first laser light and a 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. 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.

[0057] 2, 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.

[0058] [Wavelength and light absorption rate] Here, the light absorptance of metal materials will be explained. Fig. 3 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. 3 is the wavelength, and the vertical axis is the absorptance. Fig. 3 shows the relationship between wavelength and absorptance for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti).

[0059] Although the characteristics differ depending on the material, it can be seen that for each metal shown in Figure 3, 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.

[0060] 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.

[0061] 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.

[0062] 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. 2, 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. 2. 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.

[0063] Therefore, a thermal conduction type melting 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 type melting region is generated in the welded portion by irradiation of the first laser light. In this case, since a thermal conduction type melting region is formed in advance in the welded portion, a melting region of a required depth can be formed by a first laser light having a lower power than when the thermal conduction type melting region is not formed. Then, the melted state of the welded portion is changed by irradiation of the second laser light having a high absorptivity in the region B2b.

[0064] 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. 2. 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.

[0065] [Welding method] In welding using the laser welding device 100, first, the welded structure 10, in which the metal conductors 11 and 12 are temporarily fixed together by a holder (not shown), is set so that the laser light L is irradiated onto the surface Wa. Then, in a state in which the laser light L including the beams B1 and B2 is irradiated onto the surface Wa, the laser light L and the welded structure 10 are moved relatively. As a result, the laser light L moves (sweeps) on the surface Wa in the sweep direction SD while being irradiated onto the surface Wa. The portion irradiated with the laser light L melts, and then solidifies as the temperature decreases, thereby joining the metal conductors 11 and 12 via the welded portion 14, and the welded structure 10 is integrated.

[0066] [Weld cross section] FIG. 4 is a cross-sectional view of a weld 14 formed on the workpiece W. FIG. 4 is a cross-sectional view perpendicular to the sweep direction SD (X direction in FIG. 4) and along the thickness direction (Z direction). The weld 14 extends in the sweep direction SD, i.e., in a direction perpendicular to the paper surface of FIG. 4. Note that FIG. 4 shows a cross-section of the weld 14 formed on the workpiece W, which is a single copper plate with a thickness of 2 [mm]. It can be assumed that the shape of the weld 14 formed across multiple metal conductors 11, 12 is substantially the same as the shape of the weld 14 formed on the workpiece W, which is a single sheet of metal material, shown in FIG. 4.

[0067] 4, the welded portion 14 has a weld metal 14a extending from the surface Wa in the opposite direction to the Z direction, and a heat-affected zone 14b located around the welded metal 14a. The welded metal 14a is a portion that is melted by irradiation with laser light L and then solidifies. The welded metal 14a may also be referred to as a molten solidification zone. The heat-affected zone 14b is a portion of the base material of the processing object W that is thermally affected but is not melted.

[0068] The width of the weld metal 14a in the Y direction becomes narrower as it moves away from the surface Wa. That is, the cross section of the weld metal 14a has a tapered shape that becomes narrower in the opposite direction to the Z direction.

[0069] Further, detailed analysis of the cross section by the inventors revealed 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.

[0070] The first portion 14a1 is a portion obtained by melting in a keyhole shape by irradiation with the first laser light, and the second portion 14a2 is a portion obtained by melting by irradiation with a region B2b located behind the second laser light beam B2 in the sweep direction SD. Analysis by the electron back scattered diffraction pattern (EBSD) method revealed that the sizes of the crystal grains in the first portion 14a1 and the second portion 14a2 are different, and specifically, in a cross section perpendicular to the X direction (sweep direction SD), the average value of the cross-sectional area of ​​the crystal grains in the second portion 14a2 is larger than the average value of the cross-sectional area of ​​the crystal grains in the first portion 14a1.

[0071] The inventors confirmed that when only the beam B1 of the first laser light is irradiated to the processing object W, that is, when the region B2b located behind the beam B2 in the sweep direction SD is not irradiated, the second portion 14a2 is not formed, and the first portion 14a1 extends deeply from the surface Wa in the opposite direction to the Z direction. That is, in this embodiment, the second portion 14a2 is formed near the surface Wa by irradiating the region B2b located behind the beam B2 in the sweep direction SD, so that it can be presumed that the first portion 14a1 is formed on the opposite side of the second portion 14a2 to the surface Wa, in other words, at a position away from the surface Wa in the opposite direction to the Z direction.

[0072] FIG. 5 is a cross-sectional view showing a part of the welded portion 14. FIG. 5 shows the boundaries of crystal grains obtained by the EBSD method. In FIG. 5, as an example, crystal grains A having a crystal grain size of 13 μm or less are painted black. Note that 13 μm is not a threshold value of a physical property, but a threshold value set for the analysis of the experimental results. In addition, it is clear from FIG. 5 that crystal grains A are present in a relatively large amount in the first portion 14a1 and in a relatively small amount in the second portion 14a2. That is, the average value of the cross-sectional area of ​​the crystal grains in the second portion 14a2 is larger than the average value of the cross-sectional area of ​​the crystal grains in the first portion 14a1. The inventors confirmed through experimental analysis that the average value of the cross-sectional area of ​​the crystal grains in the second portion 14a2 is 1.8 times or more the average value of the cross-sectional area of ​​the crystal grains in the first portion 14a1.

[0073] As shown in region I in Figure 5, such relatively small crystal grains A are densely packed in a position away from the surface Wa in the Z direction, elongated in the Z direction. Furthermore, analysis of multiple locations at different positions in the X direction (sweep direction SD) confirmed that the region where crystal grains A are densely packed also extends in the sweep direction SD. Because welding is performed while sweeping, it can be assumed that crystals are formed in a similar shape in the sweep direction SD.

[0074] In a case where it is difficult to distinguish the first portion 14a1 from the second portion 14a2 from the appearance or hardness distribution in the cross section, the first region Z1 and the second region Z2, which are geometrically determined from the position and width wb on the surface Wa of the weld metal 14a as shown in Figs. 4 and 5, may be the first portion 14a1 and the second portion 14a2, respectively. As an example, the first region Z1 and the second region Z2 are rectangular regions extending in the Z direction with a width wm (equal width in the Y direction) in a cross section perpendicular to the sweep direction SD, the second region Z2 is a region from the surface Wa to a depth d in the Z direction, and the first region Z1 can be a region deeper than the depth d, in other words, a region on the opposite side of the surface Wa with respect to the position of the depth d. The width wm can be, for example, 1 / 3 of the width wb (average bead width) on the surface Wa of the weld metal 14a, and the depth d (height, thickness) of the second region Z2 can be, for example, 1 / 2 of the width wb. The depth of the first region Z1 may be, for example, three times the depth d of the second region Z2. The inventors have confirmed through experimental analysis of multiple samples that, in such a setting of the first region Z1 and the second region Z2, the average cross-sectional area of ​​the crystal grains in the second region Z2 is larger than the average cross-sectional area of ​​the crystal grains in the first region Z1, and is at least 1.8 times larger. Such a determination may also be evidence that the first portion 14a1 and the second portion 14a2 are formed in the weld metal 14a by welding.

[0075] [Laser light power density] FIG. 6 is a graph showing experimental results of welding in combinations of the power density Pd1 of the first laser beam and the power density Pd2 of the second laser beam on the surface Wa of the workpiece W. In FIG. 6, "◯" indicates a case where there were very few blowholes (excellent), "△" indicates a case where there were a few blowholes, and "×" indicates a case where there were a lot of blowholes (not good). Here, as an example, "excellent" indicates a case where the number of blowholes per unit length (e.g., 1 [cm]) of the linear welded portion was one or less, "good" indicates a case where the number of blowholes per unit length of the welded portion was two or more and less than five, and "not good" indicates a case where the number of blowholes per unit length of the welded portion was five or more. In this experiment, the wavelength of the first laser beam was 1070 [nm], the output was 1.5 [kW], the wavelength of the second laser beam was 450 [nm], and the output was 150 [W].

[0076] As shown in FIG. 6, the power density Pd2 of the second laser beam is 0.16 [MW / cm 2 ] or more and 1.5 [MW / cm 2 It was found that the number of blowholes can be suppressed when the power density Pd2 of the second laser beam is 0.16 [MW / cm 2 If the power density Pd2 is less than 1.5 [MW / cm 2 ] (lower limit), the amount of light energy absorbed by the copper plate surface is insufficient, and the preheating effect cannot be obtained sufficiently. 2 ] (upper limit value), keyhole-type melting also occurs with the second laser.

[0077] [DOE] As shown in FIG. 1, the optical head 120 further includes a DOE 125 between the collimator lens 121-1 and the mirror 123. The DOE 125 is a light-emitting diode (LED) 125a.

[0078] 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. 7, the DOE 125 has a configuration in which, for example, a plurality of diffraction gratings 125a with different periods are superimposed. The DOE 125 can shape the beam shape by bending the parallel light in a direction influenced by each diffraction grating 125a or by superimposing the diffraction gratings 125a. The DOE 125 can also be referred to as a beam shaper.

[0079] The optical head 120 may have a beam shaper provided after the collimator lens 121-2 to adjust the beam shape of the second laser light, and a beam shaper provided after the filter 124 to adjust the beam shapes of the first laser light and the second laser light. By appropriately adjusting the beam shape of the laser light L by the beam shaper, the occurrence of welding defects during welding can be further suppressed. In addition, the DOE 125 can split the beam of the first laser light into multiple beams.

[0080] [Thickness of metal conductor, spot diameter of each beam, power of each beam] Furthermore, the inventors have found, through experimental analysis, conditions for the thickness of the metal conductor (metal conductor 11 in the example of FIG. 1) having the surface Wa irradiated with the laser light L, the beam diameter (spot diameter) of each of the beams B1 and B2 on the surface Wa, and the power of each of the beams B1 and B2, under which a suitable welding state can be obtained in the welded structure 10. Here, a suitable welding state means that the blowhole state is "excellent" or "good" as described above.

[0081] According to an experimental analysis by the inventors, when the thickness T (see FIG. 1) of the metal conductor 11 in the Z direction is 0.2 mm or more and 1 mm or less, The spot diameter (first spot diameter) of the beam B1 is equal to or greater than 20 [μm] and equal to or less than 80 [μm], and The power of the beam B1 (the output of the laser device 111) is 0.3 [kW] or more and 6 [kW] or less, and The spot diameter (first spot diameter) of the beam B2 is equal to or greater than 50 [μm] and equal to or less than 400 [μm], and It has been found that a suitable welding state can be obtained when the power of the beam B1 (the output of the laser device 112) is 0.05 [kW] or more and 1 [kW] or less.

[0082] [Energy Density] In addition, in the experimental analysis, the inventors introduced a new index, namely, the energy density of the laser beam irradiation per unit volume of the welded structure 10, and found a condition for obtaining a favorable welding state for the energy density. The energy density can be expressed by the following formula (1). E n =P n / (V×D n ×Ta) ··· (1) Here, E n is the energy density [J / mm 3 ], P n is the power of the laser light from the laser device [W], V is the sweep speed [mm / s], D n is the spot diameter [mm] on the surface Wa, and Ta is the thickness [mm] in the Z direction of the welded structure 10 (see FIG. 1). Here, the subscript n is used to distinguish between the parameters, where n=1 indicates the parameter of the first laser light, and n=2 indicates the parameter of the second laser light.

[0083] According to the experimental analysis by the inventors, when the thickness Ta of the welded structure 10 in the Z direction is 0.2 mm or more and 1 mm or less, the energy density E1 of the beam B1 is 200 J / mm 3 ] or more, and the energy density E2 of the beam B2 is 5 [J / mm 3 ] or more and 49 [J / mm 3 It has been found that a suitable welding state can be obtained when the welding temperature is equal to or less than 100° C.

[0084] [Example of welded structure] 8 to 15 show examples of welded structures 10 (10-1 to 10-5) formed by a laser welding apparatus 100. In all of the examples in Figs. 8 to 15, the metal conductor 11 is a terminal connected to an end of a harness, and the metal conductor 12 is a bus bar electrically and mechanically connected to the metal conductor 11, which is the terminal, via a weld 14. In the examples in Figs. 8 to 15, the irradiation direction of the laser light L is the depth direction (described later) of each weld 14, and is not limited to the opposite direction to the Z direction.

[0085] In each of the examples of Figs. 8 to 15, the metal conductor 11 has a ring formed in a flat plate shape and an annular shape. The metal conductor 12 has a flat plate shape and a protrusion 12b protruding in the Z direction from an end face 12a in the thickness direction (Z direction). The protrusion 12b has a cylindrical shape extending in the Z direction and is inserted into a cylindrical through hole 11a (inner peripheral surface) extending in the Z direction of the metal conductor 11. The end face in the Z direction of the ring part of the metal conductor 11 and the end face of the protrusion 12b are substantially flush with each other and spread out crossing the Z direction. The ring part of the metal conductor 11 and the protrusion 12b suppress misalignment and separation between the metal conductor 11 and the metal conductor 12. In this configuration, a cylindrical boundary BL1 between the through hole 11a and the protrusion 12b and a planar and annular boundary BL2 between the metal conductor 11 and the end face 12a are provided between the metal conductor 11 and the metal conductor 12. It should be noted that the examples in FIGS. 8 to 15 are merely examples, and examples of the welded structure 10 are not limited to these configurations.

[0086] At least one of the metal conductors 11 and 12 is made of a copper-based material such as pure copper. In addition, a plating layer such as tin plating is formed on the surface of at least one of the metal conductors 11 and 12. In other words, at least one of the metal conductors 11 and 12 (first metal conductor) is plated. When welding such a plurality of metal conductors 11 and 12, if the material forming the plating layer is mixed into the welded portion 14, there is a risk that the joining strength of the welded portion 14 will be weakened. Therefore, the laser welding device 100 of this embodiment heats the welded portion by irradiating the second laser light included in the laser light L so that the plating layer evaporates before the welded portion 14 is formed by irradiating the laser light L including the first laser light and the second laser light. As an example, as shown in FIG. 2, when the region B2f of the second laser beam B2 is located in front of the first laser beam B1 in the sweep direction SD, the beams B1 and B2 are swept in the sweep direction SD relative to the surface Wa, so that the region B2f of the beam B2 can be irradiated and heated before the beam B1 is irradiated to the welded region. In this case, for example, by appropriately setting the power and power density of the laser devices 111 and 112, the spot diameter of the beams B1 and B2, the arrangement of the beams B1 and B2, the relative sweep speed of the laser beam L relative to the workpiece W, etc., it is possible to realize a temperature rise on the surface Wa that exceeds the melting point of the plating layer, evaporation of the plating layer based on the temperature rise, and high-quality welding. The melting point of the plating layer is lower than the melting points of both of the multiple metal conductors 11 and 12. As an example, in the case of tin plating, the melting point of tin, which is the main component of the plating layer, is 232°C. The inventors have confirmed that it is possible to realize a temperature rise exceeding the melting point (232°C) and high-quality welding by irradiating the laser light L including the beams B1 and B2 and sweeping the laser light L in the sweep direction SD. In this embodiment, the beams B1 and B2 are irradiated simultaneously as the laser light L, and the beams B1 and B2 are arranged so as not to be separated by more than a predetermined distance, for example, to be in contact with each other or to at least partially overlap each other.As a result, in addition to the energy imparted to the workpiece W by the beam B2, the energy imparted to the workpiece W by the beam B1 also contributes to increasing the temperature of the surface Wa and evaporating the plating layer before the weld 14 is formed. With such settings, the plating layer can be removed more easily or more reliably. Note that the beam B1 and the beam B2 may be spaced apart by a small distance.

[0087] Fig. 8 is a plan view of an example welded structure 10-1 (10), and Fig. 9 is a cross-sectional view taken along line IX-IX of Fig. 8. In the welded structure 10-1, a weld 14 is formed that extends in an annular shape along boundary BL1. Also, the weld 14 extends along the corner between boundary BL1 and boundary BL2. The depth direction of the weld 14 is opposite to the Z direction, and the extension direction of the weld 14 is the circumferential direction of the projection 12b.

[0088] Fig. 10 is a plan view of an example of a welded structure 10-2 (10), and Fig. 11 is a cross-sectional view taken along line XI-XI of Fig. 10. In the welded structure 10-2, a weld 14 is formed, which extends in an arc shape along the boundary BL2. The weld 14 extends along the corner between the outer circumferential surface of the metal conductor 11 and the end face 12a, in other words, along the radial outer edge of the boundary BL2. The depth direction of the weld 14 is a direction between the opposite direction of the Z direction and the radially inward direction of the projection 12b, and the extension direction of the weld 14 is the circumferential direction of the projection 12b.

[0089] Fig. 12 is a plan view of an example welded structure 10-3 (10), and Fig. 13 is a cross-sectional view taken along line XIII-XIII in Fig. 12. In the welded structure 10-3, a weld 14 is formed which penetrates the metal conductor 11 and straddles the boundary BL2 in the Z direction. The weld 14 extends from the metal conductor 11 to the metal conductor 12. The weld 14 also extends in an annular shape at the widthwise center of the annular portion of the metal conductor 11. The depth direction of the weld 14 is opposite to the Z direction, and the extension direction of the weld 14 is the circumferential direction of the projection 12b.

[0090] Fig. 14 is a plan view of an example welded structure 10-4 (10). In the welded structure 10-4, as in Fig. 12, a weld 14 is formed that penetrates the metal conductor 11 and straddles the boundary BL2 in the Z direction. The weld 14 also straddles the annular boundary BL2 in a direction intersecting the circumferential direction of the annular ring (the Y direction in Fig. 14). The depth direction of the weld 14 is the opposite direction to the Z direction, and the extension direction of the weld 14 is the Y direction.

[0091] Fig. 15 is a cross-sectional view of an example welded structure 10-5 (10) at the same position as Fig. 9. In the welded structure 10-5, the welded portion 14 extends in an annular shape along both boundaries BL1 and BL2. The welded portion 14 also extends along the corner between boundaries BL1 and BL2. The depth direction of the welded portion 14 is a direction between the opposite Z direction and the radially outward direction of the projection 12b, and the extension direction of the welded portion 14 is the circumferential direction of the projection 12b.

[0092] In the example of FIG. 15, the welded portion 14 does not pass through the end face of the metal conductor 11 in the Z direction. In this way, even if the welded portion 14 is not formed on the surface of the metal conductor 11, if the end face is irradiated with the second laser light, and a heated state exceeding the melting point of the metal that is a component of the plating layer is obtained at the end face, the plating layer may be removed at the end face. That is, the plating layer may be removed even at a portion away from the region where the welded portion 14 is formed, in other words, at a portion away from the exposed portion of the welded metal 14a. According to such a method, it is possible to more reliably suppress the intrusion of the metal that is a component of the plating layer into the welded portion 14.

[0093] As described above, in this embodiment, for example, a weld 14 that joins multiple metal conductors 11, 12 including a metal conductor having a plating layer formed thereon is formed by irradiating laser light L, and the laser light L includes a beam B1 having a wavelength of 800 nm or more and 1200 nm or less and a beam B2 having a wavelength of 500 nm or less, and the plating layer formed on at least one of the multiple metal conductors 11, 12 is removed by a second laser light that forms beam B2.

[0094] In the present embodiment, for example, the wavelength of the second laser light is not less than 400 [nm] and not more than 500 [nm].

[0095] According to this method, for example, the plating layer can be removed by the second laser light, so that it is possible to prevent the metal that is a component of the plating layer from being mixed into the welded portion 14, which would reduce the joint strength of the welded portion 14. In addition, since it is not necessary to remove the plating layer by irradiating a separate pulsed laser before welding, the processing time can be shortened and the processing effort and cost can be reduced. Furthermore, the irradiation of the laser light L that forms the beams B1 and B2 has the advantage of allowing higher quality welding with less spatter and blowholes to be performed.

[0096] In the present embodiment, for example, the laser light L including the first laser light and the second laser light is swept in the sweep direction SD on the surface Wa, and the welded portion 14 extends in the X direction along the surface Wa.

[0097] In this embodiment, for example, on the surface Wa, at least a part of the beam B2 (second spot) of the second laser light is located further forward in the sweep direction SD than the beam B1 (first spot) of the first laser light.

[0098] In this embodiment, for example, the beam B1 and the beam B2 at least partially overlap on the surface Wa.

[0099] Also, in this embodiment, for example, on the surface Wa, the beam B2 is wider than the beam B1.

[0100] 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.

[0101] As described above, the inventors have confirmed that welding defects can be further reduced in welding by irradiation of the laser light L that forms such beams B1 and B2 on the surface Wa. This is presumably because, as described above, the workpiece W is preheated by the region B2f of the beam B2 before the arrival of the beam B1, and the molten pool of the workpiece W formed by the beam B2 and the beam B1 is more stabilized. Therefore, with the laser light L having such beams B1 and B2, for example, welding with fewer welding defects and higher welding quality can be performed. In addition, with such settings of the beams B1 and B2, for example, the power of the first laser light can be lowered. In addition, when the beams B1 and B2 are irradiated coaxially, there is also an advantage that the relative rotation between the optical head 120 and the workpiece W is not required.

[0102] In this embodiment, for example, at least one of the metal conductors 11 and 12 is made of a copper-based material, and the plating layer is, for example, a tin plating layer. The effects of this embodiment can be obtained in such a configuration.

[0103] [Second embodiment] Fig. 16 is a schematic diagram of a laser welding apparatus 100A of the second embodiment. As shown in Fig. 16, in this embodiment, the drive mechanism 150 moves the workpiece W relative to the optical head 120, thereby sweeping the laser light L irradiated from the optical head 120 over the surface Wa. The operation of the drive mechanism 150 is controlled by the controller 141. In this case, in order to sweep the laser light L over the surface Wa in the sweep direction SD, the drive mechanism 150 moves the workpiece W in the opposite direction to the sweep direction SD relative to the optical head 120.

[0104] Also in this embodiment, the controller 141 can detect the deviation of the spot from the predetermined position from the image captured by the camera 170 and control the driving mechanism 150 to correct the deviation. The controller 141 may also execute feedback control so that the deviation falls within a predetermined threshold. The controller 141 and the driving mechanism 150 are an example of a correction mechanism. With such a configuration, the accuracy of the irradiation position of the laser light can be improved.

[0105] This embodiment also provides the same effects as the first embodiment.

[0106] [Third embodiment] Fig. 17 is a schematic diagram of a laser welding apparatus 100B of the third embodiment. As shown in Fig. 17, in this embodiment, the optical head 120 has a galvano scanner 126 between the filter 124 and the condenser lens 122. Except for this point, the laser welding apparatus 100B has the same configuration as the laser welding apparatus 100 of the first embodiment.

[0107] The galvano scanner 126 has two mirrors 126a and 126b, and is a device that can move the irradiation position of the laser light L and sweep the laser light L without moving the optical head 120 by controlling the angles of the two mirrors 126a and 126b. The angles of the mirrors 126a and 126b are each changed by a motor (not shown) controlled by, for example, the controller 141. With this configuration, a mechanism for relatively moving the optical head 120 and the workpiece W is not required, and an advantage is obtained in that, for example, the device configuration can be made more compact.

[0108] Also in this embodiment, the controller 141 can detect the deviation of the spot from a predetermined position from the image captured by the camera 170 and control the galvano scanner 126 to correct the deviation. The controller 141 may also execute feedback control so that the deviation falls within a predetermined threshold. The controller 141 and the galvano scanner 126 are an example of a correction mechanism. With such a configuration, the accuracy of the irradiation position of the laser light can be improved.

[0109] 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.

[0110] For example, the number of metal conductors may be three or more, and in this case, the number of metal conductors having a plating layer formed thereon is one or more.

[0111] Furthermore, when the laser beam is swept over the workpiece, the sweep may be performed by known wobbling, weaving, output modulation, or the like, to adjust the surface area of ​​the molten pool. [Explanation of symbols]

[0112] 10, 10-1 to 10-5… Welded structure 11...Metal conductor (first metal conductor) 11a...Through hole 12...Metal conductor (first metal conductor) 12a...end face 12b…Protrusion 14…Welded section 14a…Weld metal 14a1…first part 14a2…Second part 14b…Heat affected zone 100, 100A, 100B...Laser welding device (welding device) 111...Laser device (laser oscillator) 112...Laser device (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 127…Filter 128…Mirror 130...Optical fiber 141...Controller (detection mechanism, correction mechanism) 150...Drive mechanism (correction mechanism) 170...Camera (detection mechanism) A...Crystal grain B1…Beam (first spot) B1a…Outer edge B2…Beam (second spot) B2a…Outer edge B2b…area B2f…area BL1,BL2…boundary C...center point D1…Spot diameter (outer diameter) D2: Spot diameter (outer diameter) D n …Spot diameter d…Depth E n ,E1,E2…Energy density I…area L: Laser light Pd1, Pd2…Power density P n …power SD…Sweep direction T…(Thickness of the metal conductor irradiated with laser light) Ta…(Thickness of the object to be processed) V…Sweep speed W…Processing target Wa…Surface wb…Width (at the surface of the weld metal) X…direction Y...Direction Z…direction Z1…first area Z2…Second area

Claims

1. A welding method for welding a plurality of metal conductors by forming a weld by irradiating a laser beam onto a surface of an object to be processed, the surface being a plurality of metal conductors including at least one metal conductor having a plating layer formed thereon, and sweeping the laser beam to form a weld, the method comprising: the laser light includes a first laser light having a wavelength of 800 nm or more and 1200 nm or less, and a second laser light having a wavelength of 500 nm or less, on the surface, an entire area of ​​a first spot formed by the first laser light overlaps with a second spot formed by the second laser light, and a second outer edge of the second spot surrounds the first outer edge of the first spot at a distance; removing the plating layer by irradiating the second laser light; the welded portion has a second portion that is formed by the second laser beam and is in contact with the surface, and a first portion that is formed by the first laser beam and is located on the opposite side of the surface with respect to the second portion, and extends in an irradiation direction of the laser beam from a position in contact with the second portion, The welding method, wherein a power density of the second laser light on the surface is equal to or greater than 0.16 [MW / cm 2 ] and equal to or less than 1.5 [MW / cm 2 ].

2. 2. The welding method according to claim 1, wherein the second laser light has a wavelength of 400 nm or more and 500 nm or less.

3. The welding method according to claim 1 or 2, wherein the plating layer has a melting point lower than a melting point of the plurality of metal conductors.

4. The welding method according to any one of claims 1 to 3, wherein at least one of the plurality of metal conductors is made of a copper-based material.

5. The thickness of the metal conductor having the surface among the plurality of metal conductors is 0.5 mm or more and less than 1 mm, a spot diameter of a first spot formed on a plane perpendicular to the surface by the first laser light is equal to or greater than 20 [μm] and equal to or less than 80 [μm]; The power of the first laser light is equal to or greater than 0.3 [kW] and equal to or less than 6 [kW], a spot diameter of a first spot formed on a plane perpendicular to the surface by the second laser beam is equal to or greater than 50 [μm] and equal to or less than 400 [μm]; 5. The welding method according to claim 1, wherein the power of the second laser light is equal to or greater than 0.05 kW and equal to or less than 1 kW.

6. The energy density of the first laser light per unit volume in the irradiation direction of the laser light at the welded portion of the plurality of metal conductors is 200 [J / mm ３ ] and above, The energy density of the second laser beam per unit volume in the irradiation direction of the laser beam in the welded portion is 5 [J / mm ３ ] or more and 49 [J / mm ３ 6. The welding method according to claim 1, wherein the welding speed is 1000 mm or less.

7. A laser oscillator; an optical head that forms a weld by irradiating and sweeping a laser beam from the laser oscillator onto a surface of a processing object that is a plurality of metal conductors including at least one metal conductor having a plating layer formed thereon; A welding apparatus for welding the plurality of metal conductors, comprising: the laser light includes a first laser light having a wavelength of 800 nm or more and 1200 nm or less, and a second laser light having a wavelength of 500 nm or less, on the surface, an entire area of ​​a first spot formed by the first laser light overlaps with a second spot formed by the second laser light, and a second outer edge of the second spot surrounds the first outer edge of the first spot at a distance; removing the plating layer by irradiating the second laser light; the welded portion has a second portion formed by the second laser beam and in contact with the surface, and a first portion formed by the first laser beam, located on the opposite side of the surface with respect to the second portion, and extending in an irradiation direction of the laser beam from a position in contact with the second portion, A welding device, wherein a power density of the second laser light on the surface is equal to or greater than 0.16 [MW / cm 2 ] and equal to or less than 1.5 [MW / cm 2 ].

8. 8. The welding apparatus of claim 7, further comprising a beam shaper for splitting the laser light into a plurality of beams.

9. 9. The welding apparatus according to claim 7, further comprising a galvanometer scanner that changes an irradiation direction of the laser light so as to sweep the laser light on the surface in a sweep direction.

10. a detection mechanism for detecting a deviation of a spot formed on the surface by the laser light from a predetermined position; A correction mechanism for correcting the deviation; The welding device according to any one of claims 7 to 9, comprising:

11. The welding device according to claim 10 , wherein the correction mechanism changes a relative position between the plurality of metal conductors and the optical head.

12. The welding device according to claim 10 , wherein the correction mechanism includes a galvanometer scanner that changes an irradiation direction of the laser light so as to sweep the laser light in a sweep direction on the surface.

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