A laser welding method and a laser welding apparatus

Abstract

The present application relates to the technical field of laser, in particular to a laser welding method and laser welding equipment. The present application comprises: making the annular laser spot weld the object to be welded according to the pattern of spiral point shape. The present application solves the defects of welding point explosion splash, bulge and the like existing in the prior art of laser welding process technology.

Description

Technical Field

[0001] This invention relates to the field of laser technology, specifically a laser welding method and laser welding equipment. Background Technology

[0002] Semiconductor lasers use a semiconductor material as the working medium and are excited by an electric current to output laser light. Currently, the commonly used semiconductor lasers in industry operate in the 900-1000nm wavelength range, primarily used in lidar detection, laser welding, and as pump excitation sources for fiber lasers. In laser welding applications, semiconductor lasers can be categorized into 100W-level and kilowatt-level lasers. 100W-level semiconductor lasers are mainly used for laser soldering, plastic welding, and thin-film welding, while kilowatt-level semiconductor lasers are mainly used for welding metals such as carbon steel and stainless steel. In laser welding, semiconductor lasers use module beam combining to couple the semiconductor laser light into a large-core fiber to achieve 100W or kilowatt-level laser output. The output laser beam is a Gaussian beam, typically circular in shape. The higher the output power, the greater the power density at the center of the beam. During laser welding, a locally high power density can easily lead to spatter and uneven weld pool, limiting the application scenarios for precision welding. Summary of the Invention

[0003] To address the technical problems of spatter and uneven weld pool in current devices, a laser welding method and equipment are proposed, aiming to solve the problems of locally high spot power density, spatter, and uneven weld pool caused by current Gaussian beams. The purpose of this invention is to provide a laser welding method, comprising:

[0004] The ring-shaped laser spot is used to weld the workpiece in a spiral dot pattern.

[0005] Furthermore, including:

[0006] Step S10: The central control system controls the laser to emit a ring-shaped laser spot, which enters the galvanometer group through the external optical path transmission system.

[0007] Step S20: The annular laser spot is moved in a spiral dot pattern by the high-speed oscillation of the galvanometer group to weld the workpiece.

[0008] Optionally, the welding speed range is 500mm / s-600mm / s.

[0009] Optionally, the spiral spacing of the spiral dot pattern ranges from 0.001mm to 100.00mm or from 0.05mm to 0.06mm.

[0010] Optionally, the laser output from the laser is transmitted through an optical fiber to obtain a ring-shaped laser spot. The inner ring core diameter of the optical fiber is 14um-100um, which is used to output the inner ring spot. The outer ring core diameter of the optical fiber is 100um-400um.

[0011] Optionally, the annular laser spot consists of an inner ring spot and an outer ring spot, wherein the power of the inner ring spot is 500W-2000W and the power of the outer ring spot is 1000W-4000W.

[0012] Optionally, the annular laser spot is composed of an inner ring spot and an outer ring spot, wherein the ratio of the outer diameter of the outer ring spot to the inner diameter of the inner ring spot is greater than 1.

[0013] Optionally, the outer ring spot power is 1000W, and the inner ring spot power is 1000W.

[0014] Optionally, the laser output from the laser is transmitted through an optical fiber to obtain an initial annular spot. The initial annular spot is then collimated by a collimation module, oscillated by a galvanometer group, and focused by a field lens to become an annular laser spot.

[0015] Optionally, the object to be soldered is a laptop battery protection board (BMU).

[0016] Optionally, the copper busbar BSB plated with OSP on the laptop battery protection board BMU is overlaid with Ni pads, and the thickness of the copper plated with OSP is 0.2mm-0.3mm, and the thickness of the Ni pads is 0.3mm-0.5mm.

[0017] Optionally, a dust extraction device can be used to remove the fumes generated during the welding process.

[0018] A laser welding apparatus is provided, which is used in the steps of the laser welding method described in any one of the above. The apparatus includes a central control system, a laser, an optical fiber for outputting a ring-shaped laser spot, a collimation module, a galvanometer group, a field lens, a dust extraction method, and a worktable. The central control system is electrically connected to or wirelessly connected to the laser. The output end of the laser is connected to the input end of the optical fiber. The output end of the optical fiber is connected to the laser input end of the collimation module. The laser output end of the collimation module has a laser input end of the galvanometer group, and the laser output end of the galvanometer group has a field lens. The laser output from the laser passes sequentially through the optical fiber, the collimation module, the galvanometer group, and the field lens to reach the workpiece to be welded located on the worktable. The galvanometer group oscillates at high speed, causing the ring-shaped laser spot to move on the workpiece according to a preset weld point pattern. The preset weld point pattern is a spiral dot shape with a spiral spacing ranging from 0.001mm to 100.00mm or from 0.05mm to 0.06mm.

[0019] Optionally, the collimation module has a collimation focal length of 100mm-200mm, the galvanometer aperture of the galvanometer group has a focal length of 15mm-30mm, and the field lens has a focal length of 175mm-348mm.

[0020] Optionally, the laser emits a wavelength range of 335nm-1064nm.

[0021] Optionally, the laser is a ring-shaped laser, wherein the inner ring core diameter is 14um-100um and the inner ring power is 500W-2000W, the outer ring core diameter is 100um-400um and the outer ring power is 1000W-4000W.

[0022] Beneficial effects: This method and equipment control a laser generator via a central control system, which transmits the laser beam through an external optical path to a galvanometer system. Under the control of the control system, the battery module (BMU) is ultimately laser-welded. This method and equipment for welding on the BMU offers advantages such as a good weld appearance, no bulging, and no spatter or spatter. This method and equipment for welding on the BMU solves the defects of existing laser welding processes, such as spatter and bulging at the weld joints. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the welding scenario of the present invention;

[0024] Figure 2 This is a schematic diagram of the welding trajectory;

[0025] Figure 3 This is a schematic diagram of a laser welding equipment.

[0026] Figure 4 This is a schematic diagram of a ring-shaped light spot. Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terms "inner," "upper," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0028] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] The present invention will be further described below with reference to the accompanying drawings:

[0030] Reference Figures 1-4 In one embodiment, the annular laser spot is used to weld the workpiece in a spiral dot pattern.

[0031] In this embodiment, the annular laser spot is used to weld the workpiece in a spiral dot pattern. The workpiece consists of a copper busbar BSB layer with OSP plating, a Ni pad layer, a tin layer, and a battery protection board (BMU) layer from top to bottom. The tin layer adheres the Ni pad layer to the battery protection board (BMU) layer. OSP is an organic polymer film layer. In this embodiment, the copper busbar BSB layer is welded to the Ni pads on the battery protection board (BMU) using an annular laser spot.

[0032] On the one hand, when the ring-shaped laser beam is incident on the copper busbar BSB layer plated with OSP, the OSP will decompose under heat during the welding process, generating a large amount of gas. Some of the gas is violently discharged from the molten pool, causing problems such as blasting and spattering; the other part of the gas dissolves in the molten pool and precipitates out during the cooling process due to the reduced solubility of the gas in the molten liquid. It cannot be discharged in time and forms bulges. On the other hand, since there is a tin layer in the workpiece to be welded, but the tin layer has a low melting point and heats up quickly in the laser welding scenario, if the welding heat input is too large, the rapid melting of the tin layer will cause the molten tin to fly out, resulting in poor solder ball spattering.

[0033] In this embodiment, the workpiece is welded using a ring-shaped laser spot in a spiral dot pattern to address the two issues mentioned above. Firstly, the spiral dot welding trajectory has two advantages over other welding trajectories: the spacing between spiral dots is equal and non-intersecting, resulting in better penetration stability; secondly, the temperature field at the spiral dots is more concentrated, leading to slower weld cooling and reducing the likelihood of OSP bulging and spatter in the BSB layer. Therefore, the spiral dot welding trajectory is preferred. Secondly, the combination of "spiral dots + ring-shaped laser spot" reduces the probability of bulging and produces a significantly better weld appearance than either "spiral dots" or "ring-shaped laser spot" alone. This reduces bulging while preventing tin melting and solder ball spatter.

[0034] In one embodiment, it includes:

[0035] Step S10: The central control system controls the laser 2 to emit a ring-shaped laser spot, which enters the galvanometer group 5 through the external optical path transmission system.

[0036] In step S20, the annular laser spot is moved in a spiral dot pattern by the high-speed oscillation of the galvanometer group 5 to weld the workpiece.

[0037] In one embodiment, the welding speed ranges from 500 mm / s to 600 mm / s.

[0038] In this embodiment, at a lower welding speed, the weld pool cools slowly, which facilitates the escape of gas from the molten pool and reduces the probability of bulging and spatter. However, the weld penetration stability is poor. At a higher welding speed, the weld pool cools quickly, which is not conducive to the escape of gas from the molten pool and easily leads to bulging, spatter, and spatter. Experimental verification shows that the optimal welding speed range for good welding results is 500mm / s-600mm / s.

[0039] In one embodiment, the helical spacing of the helical dot pattern ranges from 0.001mm to 100.00mm or from 0.05mm to 0.06mm.

[0040] In this embodiment, laser 2 is a ring-spot laser that outputs a ring-shaped laser spot. The ring-shaped laser spot welds the workpiece according to a preset weld point pattern. The preset weld point pattern is a spiral dot shape with a spiral spacing ranging from 0.001mm to 100.00mm or from 0.05mm to 0.06mm. The spiral spacing of the spiral dot trajectory has a significant impact on the welding effect. The smaller the spiral spacing, the higher the weld overlap, but the slower the weld pool cools. The gas inside the weld pool is easier to expel, but the higher the overlap, the worse the weld penetration stability. The larger the spiral spacing, the smaller the weld overlap, the faster the weld pool cools, and the more difficult it is for the gas inside the weld pool to escape, making it prone to bulging, spattering, and other defects. Experimental verification shows that a spiral spacing range of 0.05mm-0.06mm yields better welding results.

[0041] In one embodiment, the laser output from laser 2 is transmitted through optical fiber 3 to obtain an annular laser spot. The inner ring core diameter of optical fiber 3 is 14um-100um, which is used to output the inner ring spot; the outer ring core diameter of optical fiber 3 is 100um-400um.

[0042] In one embodiment, the annular laser spot is composed of an inner ring spot and an outer ring spot, wherein the power of the inner ring spot is 500W-2000W and the power of the outer ring spot is 1000W-4000W.

[0043] In one embodiment, the annular laser spot is composed of an inner ring spot and an outer ring spot, wherein the ratio of the outer diameter of the outer ring spot to the inner diameter of the inner ring spot is greater than 1.

[0044] In one embodiment, the power of the outer ring spot is 1000W, and the power of the inner ring spot is 1000W.

[0045] In one embodiment, the laser output by the laser 2 is transmitted through the optical fiber 3 to obtain an annular initial light spot. The annular initial light spot is collimated by the collimation module 4, oscillated by the galvanometer group 5, and focused by the field lens 6 to become an annular laser light spot.

[0046] In one embodiment, the object to be soldered is a laptop battery protection board BMU8.

[0047] In one embodiment, the copper busbar BSB plated with OSP on the notebook battery protection board BMU8 is overlaid with Ni pads, and the thickness of the copper plated with OSP is 0.2mm-0.3mm, and the thickness of the Ni pads is 0.3mm-0.5mm.

[0048] In this embodiment, OSP is an organic solder mask.

[0049] In one embodiment, the dust generated during the welding process is removed by a dust extraction device 7.

[0050] In this embodiment, a dust extraction device 7 is provided on one side of the notebook battery protection board BMU(8) to remove the fumes generated during the welding process.

[0051] A laser welding apparatus is provided, which is used to perform the steps of the laser welding method described in any one of the above claims. The apparatus includes a central control system 1, a laser 2, an optical fiber 3 for outputting a ring-shaped laser spot, a collimation module 4, a galvanometer group 5, a field lens 6, a dust extraction method 7, and a worktable 9. The central control system 1 is electrically connected to the laser 2 or wirelessly connected. The output end of the laser 2 is connected to the input end of the optical fiber 3, and the output end of the optical fiber 3 is connected to the laser input end of the collimation module 4. The laser output end of the collimation module 4 is provided with the laser input end of the galvanometer group 5, and the laser output end of the galvanometer group 5 is provided with the field lens 6. The laser output from the laser 2 passes sequentially through the optical fiber 3, the collimation module 4, the galvanometer group 5, and the field lens 6 before reaching the workpiece to be welded located on the worktable 9. The galvanometer group 5 oscillates at high speed, causing the ring-shaped laser spot to move on the workpiece according to a preset weld point pattern. The preset weld point pattern is a spiral dot shape with a spiral spacing ranging from 0.001mm to 100.00mm or from 0.05mm to 0.06mm.

[0052] In one embodiment, the collimation module 4 has a collimation focal length of 100mm-200mm, the galvanometer group 5 has a galvanometer aperture of 15mm-30mm, and the field lens 6 has a focal length of 175mm-348mm.

[0053] In one embodiment, the laser emitted by laser 2 has a wavelength range of 335nm-1064nm.

[0054] In one embodiment, the laser 2 is a ring-shaped laser, wherein the inner ring core diameter of the laser 2 is 14um-100um and the inner ring power is 500W-2000W, the outer ring core diameter is 100um-400um and the outer ring power is 1000W-4000W.

[0055] In one embodiment, a laser welding method on a BMU (Brainboard Unit) includes the following steps:

[0056] Select the BMU8 to be soldered and set the relative position of the BMU8 to be soldered and the external optical path system;

[0057] The laser 2 is controlled by the central control system 1 to emit laser light.

[0058] The laser emitted by laser 2 enters the galvanometer group 5 through the external optical path transmission system;

[0059] The laser is oscillated at high speed by the galvanometer group 5, so that the laser works on the BMU 8 to be welded and forms a welding trajectory.

[0060] In one embodiment, a dust extraction device 7 is provided on one side of the BMU 8 being welded to remove the fumes generated during the welding process.

[0061] In one embodiment, the BMU 8 to be soldered is a copper BSB plated with OSP and laminated with a Ni pad, and the thickness of the copper OSP is 0.2mm-0.3mm, and the thickness of the Ni pad is 0.3mm-0.5mm.

[0062] In one embodiment, the weld pattern is a spiral pattern. Because the heat is concentrated at the spiral pattern, the weld pool cools relatively slowly, which is conducive to the exhaust of gas from the weld pool and results in a relatively good welding effect.

[0063] A laser welding device for BMU (Brainboard Unit) includes a central control system 1, a laser 2, an optical fiber 3, a collimation module 4, a galvanometer group 5, a field lens 6, a dust extraction device 7, and a worktable 9.

[0064] In one embodiment, the laser 2 is a ring-shaped laser with an inner ring core diameter of 14um-100um and an inner ring power of 500W-2000W, and an outer ring core diameter of 100um-400um and an outer ring power of 1000W-4000W.

[0065] In one embodiment, the laser emitted by laser 2 has a wavelength range of 335nm-1064nm.

[0066] In one embodiment, the collimating focal length is 100mm-200mm, the galvanometer aperture is 15mm-30mm, and the field lens focal length is 175mm-348mm.

[0067] In one embodiment, reference is made to Figure 1-4 When welding BMU, the appropriate laser is first selected based on the characteristics of the material being welded, its surface condition, and the welding requirements. Copper has good thermal conductivity, and the weld pool cools quickly, requiring preheating and slow cooling to improve the stability of the weld pool. Copper has a low absorption rate of infrared laser, and a higher power density is beneficial to the stability of the weld pool. Copper has an OSP coating on its surface, which requires slowing down the cooling rate of the weld pool and improving the exhaust of gas from the weld pool. Therefore, the laser 2 selected in this embodiment is a ring spot laser.

[0068] The selection of the inner and outer ring core diameters of the laser is mainly based on the requirements for weld pool stability, weld depth uniformity, and the limitation of welding heat input. Considering that the inner ring core diameter has better weld depth stability and uniformity, and the outer ring core diameter has lower heat input, the preferred inner ring core diameter is 14µm, and the preferred outer ring core diameter is 100µm. The selection of laser power is mainly based on the physical properties and thickness specifications of the welding material, but considering the actual equipment conditions, the preferred inner ring power is 1000W, and the preferred outer ring power is 1000W.

[0069] Next, based on the optical performance parameters of the laser, the influence of the galvanometer size on the welding effect, and the influence of the welding spot size on the welding effect, the configuration of the external optical path system is selected. Small-diameter galvanometers provide faster control response during welding, making them more suitable for high-speed welding of small welding patterns. Considering the optical performance parameters and collimation specification range of the laser, the preferred aperture of galvanometer group 5 is 20mm. Based on the optical performance parameters of the laser and the selected galvanometer aperture size, and according to optical formulas, if the collimation is too large, the collimated spot diameter will exceed the galvanometer aperture; therefore, the preferred focal length of collimation module 4 is 100mm. Considering the influence of the welding spot size on the welding effect, the preferred focal length of field lens 6 is 175mm.

[0070] Next, adjust the worktable 9 to move the galvanometer group 5 up and down, determine the focusing point of the field lens 6, and mark the focus position. Then adjust the worktable 9 again so that the focus is located on the surface of the BUM to be welded.

[0071] Next, the central control system 1 activates the laser generator 2 to emit laser light. The laser light passes through the optical fiber 3 into the collimation module 4, where it is collimated into a parallel beam. This beam then passes through the aperture of the galvanometer mirror and enters the galvanometer group 5. After being reflected by the deflecting mirror, it enters the field mirror 6, which focuses the parallel beam onto the BMU 8 to be welded, forming a molten pool. The parameters of the laser generator 2 and the galvanometer group 5 are then set in the central control system 1, causing the laser with a certain energy to form a welding trajectory on the BMU 8 through the high-speed oscillation of the deflecting mirror within the galvanometer group 5. Simultaneously, a dust extraction device 7 is installed to remove the fumes generated during welding, preventing any impact on the welding effect and environmental pollution.

[0072] The welding trajectory of this welding method is a spiral point, as shown in the schematic diagram below. Figure 2 As shown in the figure, Δr represents the helical spacing of the helical points. The helical point welding trajectory has two advantages over other welding trajectories: firstly, the spacing between the helical points is equal and there is no overlap, resulting in better weld penetration stability; secondly, the temperature field at the helical points is more concentrated, and the weld cools relatively slowly, which can reduce the probability of bulging, spatter, and splashing to a certain extent. Therefore, the helical point welding trajectory is preferred.

[0073] The helical spacing of the spiral trajectory has a significant impact on the welding effect. A smaller helical spacing results in higher weld overlap, but slower molten pool cooling. While it facilitates the expulsion of gas from the weld pool, the higher the overlap, the worse the weld penetration stability. Conversely, a larger helical spacing results in lower weld overlap, faster weld pool cooling, and difficulty in gas expulsion, leading to bulging, spattering, and other defects. Experiments have shown that a helical spacing of 0.05mm-0.06mm provides the optimal welding effect.

[0074] In laser welding, welding speed directly affects the welding effect. Besides directly influencing the weld penetration, it also affects the cooling rate of the weld pool and the stability of the penetration. At lower speeds, the weld pool cools slowly, facilitating gas escape and reducing the likelihood of bulging and spatter. However, the weld penetration stability is poor. At higher welding speeds, the weld pool cools quickly, hindering gas escape and increasing the likelihood of bulging, spatter, and spatter. Experiments have shown that the optimal welding speed range for good welding results is 500 mm / s to 600 mm / s.

[0075] The inner and outer ring power of the laser have different effects on the welding effect. The inner ring power mainly affects the weld pool depth, while the outer ring power mainly affects the weld appearance. Because welding requirements limit the weld depth range, the inner ring welding power is adjusted based on the weld depth. The outer ring power has a direct and significant impact on the weld appearance. Lower outer ring power results in poor preheating and slow cooling of the weld, hindering gas escape and potentially causing bulging, spatter, and other defects. Higher outer ring power provides significant preheating and slow cooling, facilitating gas escape and greatly improving bulging and spatter issues. However, due to the limitations of BMU welding heat input, the solder layer at the bottom of the pads cannot melt and overflow due to excessive pad temperature. Experimental testing shows that the optimal outer ring power range for welding effect is 300W-500W.

[0076] Based on the absorption characteristics of BMU welding materials, welding requirements, and welding effects, this invention selects a suitable laser, peripheral optical configuration, and welding pattern. It comprehensively considers and sets three parameters: helical pitch, welding speed, and outer ring power, resulting in good weld penetration stability and a suitable preheating and slow cooling effect. This greatly improves the defects of weld bulging and spatter, and avoids the melting of the tin layer under the pad due to excessive welding heat output, thus obtaining a solder joint with good penetration stability and no bulging or spatter.

[0077] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A laser welding method, characterized in that, include: The ring-shaped laser spot is used to weld the workpiece according to a spiral dot pattern. Step S10: The central control system (1) controls the laser (2) to emit a ring laser spot, which enters the galvanometer group (5) through the external optical path transmission system. Step S20: The annular laser spot is moved in a spiral dot pattern by the high-speed oscillation of the galvanometer group (5) to weld the workpiece; the welding speed range is 500mm / s-600mm / s; the spiral spacing of the spiral dot pattern ranges from 0.05mm to 0.06mm; the laser output from the laser (2) is transmitted through the optical fiber (3) to obtain the annular laser spot, and the inner ring core diameter of the optical fiber (3) is 14um-100um, which is used to output the inner ring spot. The outer ring core diameter of the optical fiber (3) is 100um-400um. The laser output from the laser (2) is transmitted through the optical fiber (3) to obtain an annular initial spot. The annular initial spot is collimated by the collimation module (4), oscillated by the galvanometer group (5), and focused by the field lens (6) to become an annular laser spot. The annular laser spot is composed of an inner ring spot and an outer ring spot. The power of the inner ring spot is 500W-2000W, and the power of the outer ring spot is 1000W-4000W.

2. The laser welding method according to claim 1, characterized in that, The ring-shaped laser spot consists of an inner ring spot and an outer ring spot, wherein the ratio of the outer diameter of the outer ring spot to the inner diameter of the inner ring spot is greater than 1.

3. The laser welding method according to claim 1, characterized in that, The outer ring spot power is 1000W, and the inner ring spot power is 1000W.

4. The laser welding method according to claim 1, characterized in that, The fumes generated during the welding process are removed by a dust extraction device (7).

5. The laser welding method according to claim 1, characterized in that... Laser welding is performed using laser welding equipment, which includes a central control system (1), a laser (2), an optical fiber (3) for outputting a ring-shaped light spot, a collimation module (4), a galvanometer group (5), a field lens (6), a dust extraction device (7), and a worktable (9). The central control system (1) is electrically connected to the laser (2) or wirelessly connected. The output end of the laser (2) is connected to the input end of the optical fiber (3), and the output end of the optical fiber (3) is connected to the laser input end of the collimation module (4). 4) The laser output end is provided with the laser input end of the galvanometer group (5). The laser output end of the galvanometer group (5) is provided with the field lens (6). The laser output by the laser (2) passes through the optical fiber (3), collimation module (4), galvanometer group (5) and field lens (6) in sequence and reaches the workpiece to be welded on the worktable (9). The galvanometer group (5) swings at high speed to make the annular laser spot move on the workpiece to be welded according to the preset weld point pattern. The preset weld point pattern is a spiral dot shape with a spiral spacing range of 0.05mm-0.06mm.

6. The laser welding method according to claim 5, characterized in that, The collimation module (4) has a collimation focal length of 100mm-200mm, the galvanometer aperture of the galvanometer group (5) is 15mm-30mm, and the field lens (6) has a focal length of 175mm-348mm.

7. The laser welding method according to claim 6, characterized in that, The laser emitted by the laser (2) has a wavelength range of 335nm-1064nm.

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