A laser welding method and a laser welding apparatus thereof

Abstract

The application belongs to the technical field of laser welding and relates to a laser welding method and a laser welding device thereof. The laser welding method comprises the following steps: providing a first copper alloy ultrathin plate and a second copper alloy ultrathin plate; arranging a filler metal on a to-be-welded area of the first copper alloy ultrathin plate; stacking the second copper alloy ultrathin plate above the first copper alloy ultrathin plate, so that the to-be-welded areas of the two are aligned; preheating the first copper alloy ultrathin plate and the second copper alloy ultrathin plate as a whole by using an induction heating device; and performing laser welding along the arrangement position of the filler metal by using a laser. The copper alloy ultrathin plate is preheated as a whole by induction heating, so that the absorption rate of the copper alloy to laser can be improved, the laser energy loss can be reduced, the wetting performance of the filler metal on the surface of the copper base body can be improved, and the filling of the weld gap can be promoted.

Description

Technical Field

[0001] This application relates to the field of laser welding technology, and more specifically, to a laser welding method and a laser welding apparatus thereof. Background Technology

[0002] Copper alloys possess excellent electrical and thermal conductivity and corrosion resistance, making them widely used in electronics, aerospace, and automotive manufacturing. With the increasing demand for lightweight and heat dissipation in consumer electronics, the application of thin copper alloy sheets is becoming more widespread, and the application of ultra-thin copper alloy sheets is also gaining increasing attention, leading to higher requirements for thin-sheet welding technology. Laser welding, as a high-energy-density welding method, offers advantages such as fast welding speed, small heat-affected zone, minimal deformation, and high weld quality, giving it unique advantages in ultra-thin sheet welding. However, laser welding of copper alloys still faces many challenges.

[0003] For example, copper alloys have extremely low absorption rates for infrared lasers. At room temperature, the absorption rate of fiber lasers with a wavelength of 915nm is only 3-5%, which means that very high laser power is required to form a stable molten pool during the welding process, resulting in low energy utilization. At the same time, the fact that ultra-thin copper alloy plates are prone to deformation after welding also restricts their development. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of this application is that copper alloys have extremely low absorption rates for infrared lasers in the prior art.

[0005] To address the aforementioned technical problems, this application provides a laser welding method and a laser welding apparatus, employing the following technical solution: A laser welding method, comprising: Provides first and second copper alloy ultrathin plates; Solder filler metal is applied to the area to be welded on the first copper alloy ultrathin plate; The second copper alloy ultrathin plate is stacked on top of the first copper alloy ultrathin plate so that the areas to be welded on both are aligned. The first and second copper alloy ultrathin plates are preheated as a whole using an induction heating device; Laser welding is performed using a laser along the layout of the brazing filler metal.

[0006] Furthermore, the first and second copper alloy ultrathin plates comprise Cu and O, by mass percentage: Cu: ≥ 99.90%, O: 0.02-0.05%, other impurities: ≤ 0.10%; and / or, The thickness of the first copper alloy ultrathin plate and the second copper alloy ultrathin plate is 0.05-1.0 mm.

[0007] Furthermore, the brazing filler metal is a silver-copper brazing filler metal, which, by mass percentage, comprises: Ag: 60-72% and Cu: 28-40%.

[0008] Furthermore, the step of applying solder to the area to be soldered on the first copper alloy ultrathin plate includes: The solder is applied by dispensing, forming a solder layer of a predetermined width along the edge of the first copper alloy ultrathin plate.

[0009] Furthermore, the induction heating device includes an induction coil and a high-frequency induction heating power supply; The high-frequency induction heating power supply is set to a power of 5-15kW and a frequency of 50-200kHz; and / or, The induction coil is made of a circular copper tube with an inner diameter of 10-20 mm; and / or, The distance between the induction coil and the workpiece to be welded is 3-8mm.

[0010] Furthermore, after the step of preheating the first copper alloy ultrathin plate and the second copper alloy ultrathin plate as a whole using an induction heating device, the method further includes: Once the temperatures of the first and second copper alloy ultrathin plates stabilize at the preset temperature, maintain this temperature for 5-10 seconds before turning off the induction heating equipment, and then immediately perform laser welding.

[0011] Furthermore, the wavelength of the laser is 900-920nm, the welding spot of the laser is a flat-topped spot, and the energy uniformity of the spot is ≥90%.

[0012] Furthermore, a shielding gas is continuously introduced during the laser welding process. The shielding gas is argon with a purity greater than or equal to 99.99%, and the gas flow rate is set to 10-15 L / min; and / or, Laser welding employs a positive defocus welding method, with a defocusing amount of +1 to +5 mm; and / or, Laser power 50-100W, welding speed 10-30mm / s.

[0013] Furthermore, prior to the step of applying solder to the area to be soldered on the first copper alloy ultrathin plate, the method further includes: The first copper alloy ultrathin plate and the second copper alloy ultrathin plate are subjected to pre-welding pretreatment, which includes removing surface impurities, cleaning with anhydrous ethanol and drying.

[0014] To address the aforementioned technical problems, this application also provides a laser welding apparatus, including a worktable, a dispensing unit, an induction heating unit, and a laser welding unit; The workbench is equipped with a fixture platform that can move along a preset trajectory for fixing two copper alloy ultrathin plates to be welded. The dispensing unit is fixed to the first end of the workbench and is used to apply solder to the area to be soldered on the lower copper alloy ultrathin plate. The induction heating unit is movably disposed above the workbench for preheating the stacked first copper alloy ultrathin plate and the second copper alloy ultrathin plate as a whole. The laser welding unit is fixed at the second end of the worktable and is used to emit a flat-top light beam with an energy uniformity of ≥90% and perform laser welding along the brazing filler metal layout position.

[0015] Compared with the prior art, the embodiments of this application have the following main advantages: Preheating two ultrathin copper alloy plates as a whole by induction heating can improve the absorption rate of the copper alloy to the laser, reduce laser energy loss, and improve the wetting performance of the brazing filler metal on the copper substrate surface, thus promoting the filling of the weld gap. Stacking and aligning the two ultrathin plates ensures that the brazing filler metal is evenly distributed on the joint surface. Combined with the laser welding process, a reliable connection can be achieved with a smaller heat input, which helps to reduce post-weld deformation of the ultrathin plates and improve the forming quality and sealing reliability of the weld joint. Attached Figure Description

[0016] To more clearly illustrate the solution of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of the laser welding method of the present invention; Figure 2 This is a schematic diagram of the laser welding apparatus of the present invention; Figure 3 This is a schematic diagram of the laser welding unit of the present invention; Figure 4 This is a schematic diagram of the weld area of ​​the present invention; Reference numerals: 1. Workbench; 2. Moving slide rail; 3. Fixture platform; 4. High-frequency induction heating power supply; 5. Lower fixture cover plate; 6. First copper alloy ultra-thin plate; 7. Second copper alloy ultra-thin plate; 8. Upper fixture cover plate; 9. Induction coil; 10. Dispensing control system; 11. Dispensing needle; 12. Dispensing equipment; 13. Laser welding control system; 14. Scanning head; 15. Semiconductor laser; 16. Fixing bolt; 17. Welding area. Detailed Implementation

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0019] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] This application provides a laser welding method, such as... Figure 1 As shown, steps S100 to S500 are included: Step S100: Provide a first copper alloy ultrathin plate and a second copper alloy ultrathin plate.

[0021] Specifically, a first copper alloy ultrathin plate and a second copper alloy ultrathin plate are provided. By mass percentage, the composition of the copper alloy ultrathin plate is: Cu ≥ 99.90%, O: 0.02-0.05%, and other impurities ≤ 0.10%. This copper alloy composition is the foundation for achieving high-quality ultrathin plate sealing welding, meeting the heat dissipation and structural requirements of electronic component housings while ensuring the tightness and mechanical properties of the weld joint. The plate thickness ranges from 0.05-1.0 mm. When the thickness is less than 0.05 mm, the plate rigidity is insufficient, making it prone to burn-through and warping deformation during welding. When the thickness is greater than 1.0 mm, the temperature uniformity of induction heating decreases significantly, and higher laser power is required to achieve effective fusion.

[0022] Furthermore, the first and second copper alloy ultrathin plates are subjected to pre-welding pretreatment, including removing surface impurities, cleaning with anhydrous ethanol, and drying.

[0023] For example, the oxide layer and attached mechanical impurities on the surface of the two copper alloy ultrathin plates are removed by mechanical grinding or chemical cleaning. Then, the surface of the plates is wiped with anhydrous ethanol or ultrasonically cleaned to remove oil stains. Finally, the plates are dried with clean and dry compressed air for later use.

[0024] The oxide layer on the surface of copper alloys reduces the wettability of silver-copper brazing filler metal. Oil and impurities decompose at high temperatures, easily creating porosity, leading to incomplete fusion and sealing failure. Pretreatment can remove the oxide layer, exposing a fresh copper alloy sheet, reducing welding defects and ensuring weld tightness and sealing performance.

[0025] Step S200: Apply solder to the area to be soldered on the first copper alloy ultrathin plate.

[0026] Specifically, the pre-treated first copper alloy ultrathin plate is placed as the lower cover in the middle of the lower fixture cover plate of the fixture platform. Solder filler metal is applied to the area to be soldered on the first copper alloy ultrathin plate using the dispensing unit.

[0027] Using a dispensing method to apply the solder allows for more precise control over its position and width, which helps improve the consistency of the weld formation and the sealing effect. In this invention, the solder is applied using a dispensing method, forming a continuous, uniform solder layer with a width of 0.5 mm along the edge of the first copper alloy ultrathin plate, approximately 1.5 mm from the edge.

[0028] The brazing filler metal is silver-copper brazing filler metal, and its composition by mass percentage is: Ag: 60-72%, Cu: 28-40%, with a melting point range of 600-780℃.

[0029] The choice of brazing filler metal is crucial to the welding quality. This invention uses silver-copper brazing filler metal (Ag-Cu alloy), which has a melting point of 600-780℃, matching the preheating temperature. It can partially melt during the preheating process, which helps to improve the wettability and fluidity of the brazing filler metal on the copper substrate surface and facilitates the filling of the weld gap.

[0030] Step S300: Stack the second copper alloy ultrathin plate on top of the first copper alloy ultrathin plate so that the areas to be welded on both are aligned.

[0031] Specifically, a second copper alloy ultrathin plate of the same size is placed on top of the first copper alloy ultrathin plate, ensuring that the areas to be welded are completely aligned. Then, the upper fixture cover plate is placed on top. Stacking two copper alloy ultrathin plates of the same size and aligning their areas ensures that the brazing filler metal layer is evenly distributed on the mating surfaces of the upper and lower plates, preventing weld discontinuities caused by brazing filler metal misalignment. Placing the upper fixture cover plate provides initial fixation of the workpiece, reducing the risk of workpiece displacement due to thermal stress or equipment vibration during welding. It also limits thermal warpage deformation of the ultrathin plate to some extent, contributing to improved weld quality and sealing reliability. The second copper alloy ultrathin plate should be stacked in place within 20 seconds after the first copper alloy ultrathin plate has completed the solder placement. Silver-copper solder has high surface activity and is easily oxidized when exposed to air. Therefore, stacking should be completed within 20 seconds to shorten the contact time between the solder and air, thus avoiding prolonged exposure to air and oxidation of the solder surface, which would affect the subsequent welding quality.

[0032] Step S400: Preheat the first copper alloy ultrathin plate and the second copper alloy ultrathin plate as a whole using an induction heating device.

[0033] Specifically, the induction heating equipment includes an induction coil and a high-frequency induction heating power supply. The fixture platform with the workpiece fixed is moved to the induction heating station by moving the slide rail, and the position of the induction heating unit is adjusted so that the induction coil is aligned with the welding area of ​​the workpiece.

[0034] The high-frequency induction heating power supply is activated to preheat the two stacked copper alloy ultrathin plates as a whole. The output power of the high-frequency induction heating power supply is set to 5-15kW, and the operating frequency is set to 50-200kHz. The induction coil is made of a circular copper tube with an inner diameter of 10-20mm. The distance between the induction coil and the workpiece is controlled at 3-8mm, and the heating time is controlled at 10-60s, ensuring the overall temperature of the workpiece rises to within the melting point range of the brazing filler metal, for example, the melting point range of the aforementioned silver-copper brazing filler metal is 600-650℃. High-frequency induction heating can achieve uniform preheating of the copper alloy ultrathin plates. The temperature range of 600-650℃ significantly improves the absorption rate of infrared laser by the copper alloy, and is compatible with the melting point of the silver-copper brazing filler metal, causing the filler metal to partially melt in advance, improving its wetting and spreading performance. Controlling the induction power, frequency, and distance between the coil and the workpiece can obtain a more uniform temperature field and reduce local overheating.

[0035] Next, an infrared thermometer was used to monitor the surface temperature of the workpiece in real time. Once the temperature stabilized at 620℃, it was held for 5-10 seconds, after which the induction heating equipment was turned off, and laser welding was immediately performed. Holding the temperature for 5-10 seconds after stabilization allows for a more uniform temperature distribution inside the workpiece, which helps reduce welding thermal stress and the possibility of deformation of ultra-thin plates after welding.

[0036] Step S500: Laser welding is performed using a laser along the layout position of the brazing filler metal.

[0037] Specifically, the laser uses a semiconductor laser with a wavelength of 900-920nm to emit a flat-top beam. Its beam shaping system uses a microlens array or diffractive optical elements to convert the Gaussian beam into a flat-top spot with a length of 14mm and a width of 1mm, and the energy uniformity of the spot is ≥90%. Using a 900-920nm semiconductor laser in conjunction with a flat-top spot results in a more uniform energy distribution, which can reduce the risk of burn-through caused by overheating at the center of the Gaussian beam, while ensuring the fusion effect at the weld edge.

[0038] During laser welding, a protective gas, argon gas with a purity ≥99.99%, is continuously introduced into the welding area at a flow rate of 10-15 L / min. The gas nozzle is positioned at a 45° angle to the weld plane along the welding direction. Welding employs a positive defocusing method with a defocusing amount of +1 to +5 mm. The laser power is set to 50-100 W, and the welding speed is set to 10-30 mm / s. High-purity argon gas protection effectively isolates the weld from air, reducing the probability of oxidation at high temperatures. Simultaneously, the positive defocusing welding method helps reduce welding spatter. The matched laser power and welding speed control heat input while ensuring fusion quality, thus reducing deformation of ultra-thin plates.

[0039] After laser welding, continue to supply shielding gas for 10-15 seconds to prevent oxidation in the high-temperature weld area. Continuing to supply shielding gas after welding further protects the weld during the cooling phase, improving joint quality. Once the welded sample has completely cooled to room temperature, loosen the upper fixture cover and remove the welded workpiece.

[0040] This implementation preheats the entire copper alloy ultrathin plate to 600-650°C using induction heating. The absorption rate of the copper alloy for 915nm laser can be increased from about 5% at room temperature to about 25%, reducing the required laser power and improving energy utilization efficiency.

[0041] In addition, the preheating temperature is precisely matched with the melting point of silver-copper brazing filler metal (600-780℃), which allows the filler metal to partially melt before welding, improving its wettability and fluidity on the copper alloy surface, effectively filling the weld gap, and reducing defects such as incomplete fusion and porosity.

[0042] In addition, a 14mm×1mm flat-top beam spot is used for welding, with a beam spot energy uniformity of ≥90%. This avoids the problems of local overheating and burn-through caused by excessive energy at the center of the traditional Gaussian beam. At the same time, it achieves a uniform temperature field distribution, avoids local overheating, reduces the generation of porosity and spatter, and results in a beautiful weld formation and good sealing effect.

[0043] Based on the above laser welding method, such as Figures 2 to 4As shown in the figure, this application embodiment also provides a laser welding apparatus for implementing the above-mentioned laser welding method, including a worktable 1, a dispensing unit, an induction heating unit, and a laser welding unit.

[0044] The worktable 1 is equipped with a fixture platform 3 that can move along a preset trajectory. The fixture platform 3 includes a lower fixture cover plate 5 and an upper fixture cover plate 8. The lower fixture cover plate 5 is fixed to the fixture platform 3 by fixing bolts 16 to prevent the workpiece from shifting during the welding process. A sliding rail 2 is provided between the worktable 1 and the fixture platform 3. The fixture platform 3 can automatically switch between the dispensing station, the induction heating station, and the laser welding station through the sliding rail 2.

[0045] The dispensing unit is installed at the first end of the workbench 1. The dispensing unit includes a dispensing needle 11, a dispensing control system 10, and a dispensing device 12, which is used to accurately and continuously apply solder to the area to be soldered on the lower copper alloy ultrathin plate.

[0046] The induction heating unit is vertically and movably mounted above the worktable 1, and includes a high-frequency induction heating power supply 4 and an induction coil 9, used to uniformly preheat two stacked and fixed copper alloy ultrathin plates. The induction heating unit controls the vertical distance between the induction coil 9 and the workpiece surface through an independent lifting mechanism.

[0047] The laser welding unit is installed at the second end of the worktable 1 and includes a semiconductor laser 15, a laser welding control system 13 and a galvanometer 14. It is used to emit a flat-top light beam of a specific size and complete the laser welding of the weld seam according to a preset trajectory.

[0048] In this embodiment, a temperature detection unit and an automation control unit can also be provided. The temperature detection unit uses a non-contact infrared thermometer, with the probe aimed at the center area of ​​the workpiece on the fixture platform 3, to monitor the surface temperature of the copper alloy ultrathin plate in real time. The automation control unit is electrically connected to the fixture platform 3, the dispensing unit, the induction heating unit, the laser welding unit, and the temperature detection unit, respectively, to uniformly control the action sequence and process parameters of each unit, thereby realizing the automated operation of the entire welding process.

[0049] This embodiment uses a dispensing unit, an induction heating unit, and a laser welding unit to preheat the entire copper alloy ultrathin plate to 600-650°C. The absorption rate of the copper alloy to 915nm laser can be increased from about 5% at room temperature to about 25%, which greatly reduces the required laser power, significantly improves energy utilization efficiency, and reduces equipment costs.

[0050] Example 1 This embodiment focuses on the stacking and sealing of C11000 ultra-thin copper plates of different thicknesses. The specific steps are as follows: Step 1: Prepare a first copper alloy ultra-thin plate 6 (lower cover) with dimensions of 200mm×60mm×0.12mm and a second copper alloy ultra-thin plate 7 (upper cover) with dimensions of 200mm×60mm×0.06mm. Both are C11000 copper with the following mass percentage composition: Cu≥99.90%, O: 0.02-0.05%, other impurities: ≤0.10%. Remove the surface oxide layer, clean the surface oil stains with anhydrous ethanol, and dry with a hair dryer.

[0051] Step 2: Place the first copper alloy ultrathin plate 6 on the fixture platform 3, and apply a layer of silver-copper solder with a width of 0.5 mm and a thickness of 0.1 mm along the lower cover 1.5 mm from the edge using the dispensing device 12. The solder mass percentage composition is: Ag: 60-72%, Cu: 28-40%, and the melting point is 600-780℃.

[0052] Step 3: Within 20 seconds after the brazing filler metal is laid out, stack and align the second copper alloy ultrathin plate 7, and cover it with the upper fixture cover plate 8.

[0053] Step 4: Adjust the position of the circular copper tube induction coil 9, ensuring the distance between the coil and the workpiece is 5mm. Set the induction heating power to 10kW, the frequency to 100kHz, and the heating time to 30s. Once the infrared thermometer displays a stable temperature of 620℃ and holds for 5s, turn off the induction heating power and immediately move the fixture platform 3 to the laser welding station.

[0054] Step 5: Activate the 915nm semiconductor laser 15. The beam shaping system uses a microlens array to generate a 14mm × 1mm flat-top spot with an energy uniformity of ≥90%. Set the laser power to 150W, the welding speed to 20mm / s, and the defocusing distance to +5mm. During the welding process, continuously introduce 99.999% pure argon gas at a flow rate of 10L / min.

[0055] Among them, weld area 17, as Figure 4 As shown.

[0056] Step 6: After welding, continue to purge with argon gas for 10 seconds, and remove the sample after it has cooled to room temperature.

[0057] After cleaning the surface of the welded sample in Example 1, X-ray non-destructive testing, metallographic observation and sealing test were performed. The weld was well formed, without burn-through and crack defects, and the porosity was about 0.8%. The joint had good airtightness and met the product sealing requirements.

[0058] Example 2 This embodiment describes the stacking and sealing of C11000 ultra-thin copper plates of the same thickness. The specific steps are as follows: Step 1: Prepare two C11000 ultra-thin copper plates, each measuring 200mm × 60mm × 0.07mm, with the following mass percentage composition: Cu ≥ 99.90%, O: 0.02-0.05%, other impurities: ≤0.10%. Remove the surface oxide layer, clean the surface oil stains with anhydrous ethanol, and dry with a hair dryer.

[0059] Step 2: Place one of the pieces as the first copper alloy ultrathin plate 6 on the fixture platform 3, and apply a layer of silver-copper brazing filler metal with a width of 0.5 mm and a thickness of 0.1 mm at a distance of 1.5 mm from the edge. The brazing filler metal has the following composition by weight percentage: Ag: 60-72%, Cu: 28-40%, and a melting point of 600-780℃.

[0060] Step 3: Within 20 seconds of completing the solder application, stack and align another copper alloy ultrathin plate.

[0061] Step 4: Adjust the inner diameter of induction coil 9 to a distance of 5mm between the coil and the workpiece. Set the induction heating power to 8kW, the frequency to 150kHz, and the heating time to 20s. After the temperature stabilizes at 620℃, maintain this temperature for 5s, then turn off the induction heating and move the fixture to the welding station.

[0062] Step 5: Use a 910nm semiconductor laser 15 with a flat-top spot size of 14mm × 1mm and an energy uniformity of ≥90%. Set the laser power to 120W, welding speed to 8mm / s, and defocusing distance to +3mm. Use 99.99% argon as the shielding gas with a flow rate of 10L / min.

[0063] Among them, weld area 17, as Figure 4 As shown.

[0064] Step 6: After welding, purge with argon gas for 8 seconds, and remove the workpiece after cooling.

[0065] X-ray non-destructive testing, metallographic observation and sealing test were performed on the workpiece after welding in Example 2. The weld was well formed, without burn-through and crack defects, and the porosity was about 0.6%. The joint had good airtightness and met the product sealing requirements.

[0066] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A laser welding method, characterized in that, include: Provides first and second copper alloy ultrathin plates; Solder filler metal is applied to the area to be welded on the first copper alloy ultrathin plate; The second copper alloy ultrathin plate is stacked on top of the first copper alloy ultrathin plate so that the areas to be welded on both are aligned. The first and second copper alloy ultrathin plates are preheated as a whole using an induction heating device; Laser welding is performed using a laser along the layout of the brazing filler metal.

2. The laser welding method according to claim 1, characterized in that, The first and second copper alloy ultrathin plates comprise Cu and O, by mass percentage: Cu ≥ 99.90%, O: 0.02-0.05%; and / or, The thickness of the first copper alloy ultrathin plate and the second copper alloy ultrathin plate is 0.05-1.0 mm.

3. The laser welding method according to claim 1, characterized in that, The brazing filler metal is a silver-copper brazing filler metal, which, by mass percentage, comprises: Ag: 60-72% and Cu: 28-40%.

4. The laser welding method according to claim 1, characterized in that, The step of applying solder to the area to be soldered in the first copper alloy ultrathin plate includes: The solder is applied by dispensing, forming a solder layer of a predetermined width along the edge of the first copper alloy ultrathin plate.

5. The laser welding method according to claim 1, characterized in that, The induction heating device includes an induction coil and a high-frequency induction heating power supply; The power of the high-frequency induction heating power supply is set to 5-15kW, and the frequency is set to 50-200kHz. And / or, the induction coil is made of a circular copper tube with an inner diameter of 10-20mm; And / or, the distance between the induction coil and the workpiece to be welded is 3-8mm.

6. The laser welding method according to claim 1, characterized in that, After the step of preheating the first and second copper alloy ultrathin plates as a whole using an induction heating device, the method further includes: Once the temperatures of the first and second copper alloy ultrathin plates stabilize at the preset temperature, the induction heating equipment is turned off after 5-10 seconds, and then laser welding is performed.

7. The laser welding method according to claim 1, characterized in that, The laser has a wavelength of 900-920nm, and the welding spot of the laser is a flat-topped spot with a spot energy uniformity of ≥90%.

8. The laser welding method according to claim 1, characterized in that, During laser welding, a shielding gas is continuously introduced. The shielding gas is argon with a purity greater than or equal to 99.99%, and the gas flow rate is set to 10-15 L / min; and / or, Laser welding employs a positive defocus welding method, with a defocusing amount of +1 to +5 mm; and / or, Laser power 50-100W, welding speed 10-30mm / s.

9. The laser welding method according to claim 1, characterized in that, Before the step of applying solder to the area to be soldered on the first copper alloy ultrathin plate, the method further includes: The first copper alloy ultrathin plate and the second copper alloy ultrathin plate are subjected to pre-welding pretreatment, which includes removing surface impurities, cleaning with anhydrous ethanol and drying.

10. A laser welding apparatus, characterized in that, Includes a worktable, dispensing unit, induction heating unit, and laser welding unit; The workbench is equipped with a fixture platform that can move along a preset trajectory for fixing two copper alloy ultra-thin plates to be welded. The dispensing unit is fixed to the first end of the workbench and is used to apply solder to the area to be soldered on the lower copper alloy ultrathin plate. The induction heating unit is movably disposed above the workbench for preheating the stacked first copper alloy ultrathin plate and the second copper alloy ultrathin plate as a whole. The laser welding unit is fixed at the second end of the worktable and is used to emit a flat-top light beam with an energy uniformity of ≥90% and perform laser welding along the brazing filler metal layout position.

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