Laser and method for welding copper and aluminum

Abstract

The invention discloses a laser and a method for welding copper and aluminum, and provides the following scheme aiming at the problems of poor welding effect and low connection strength in the prior art: the laser for welding copper and aluminum adopts a semiconductor laser, the laser wavelength is 360-470 nanometers, the optical power is 100-4000 watts, and the laser spot diameter is 0.1-0.6 mm; the laser comprises a blue laser light-emitting module, a collimating lens, a cylindrical lens and a condensing lens, the collimating lens, the cylindrical lens and the condensing lens are arranged from top to bottom, a zone melting process similar to impurity removal in the semiconductor industry is adopted, blue laser is adopted, in the wavelength range, the absorption rate of copper can reach 50% or above, and the absorption rate of copper can reach 50% or above. In the welding process or after welding is finished, the track that laser starts from a welding seam, is perpendicular to the welding seam and moves towards the aluminum direction is increased, copper enriched near the welding seam is driven to enter the deep part of the aluminum, and therefore generation of a brittle eutectic phase Al2Cu is eliminated or reduced.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more particularly to a laser and method for welding copper and aluminum. Background Technology

[0002] Chinese patent application No. 201910592962.3 discloses a high-strength double-helix welding process for dissimilar copper and aluminum materials. The method involves cleaning the aluminum and copper materials to be welded, applying pressure to the welding surfaces to place the aluminum on top of the copper, using a single-mode laser, and employing a double-wedge mirror rotational vibration welding process. A vibration module installed between the collimating and focusing mirrors generates a spiral weld. Gas shielding is used during welding. Compared to traditional multimode laser welding processes, this invention's process utilizes the stronger penetration of single-mode lasers, resulting in greater weld penetration. Single-mode lasers offer significant advantages over multimode lasers in terms of monochromaticity and beam path, effectively reducing the edge heat effects caused by stray light and the larger beam path of multimode lasers. This also reduces side reactions such as oxidation of aluminum and copper during laser welding, lowers the formation of brittle copper-aluminum compounds, and results in higher mechanical strength and better stability of the weld, achieving stable and high-strength welding of dissimilar copper and aluminum materials.

[0003] The joining of dissimilar metals, aluminum and copper, is widely used in the manufacture of electrical and electronic products. Traditional welding methods generally employ TIG welding or MIG welding processes. The main problems with these methods are that the large heat input during welding causes significant deformation of the workpieces being welded, and the welding speed is slow.

[0004] The new welding method—laser welding—has the characteristics of high power density, low welding heat input, small welding heat-affected zone, and small welding deformation.

[0005] However, laser welding of copper and aluminum presents challenges: both copper and aluminum have low absorption rates of laser light before melting, requiring high laser power to form a molten pool and keyhole; the weld zone where copper and aluminum meet contains many brittle intermediate phases, especially Al2Cu, resulting in low weld strength and poor toughness.

[0006] In addition to the two points mentioned above, copper has a much higher volumetric heat capacity than aluminum, and its thermal conductivity is also much higher than that of aluminum. In other words, copper is more difficult to heat and raise the temperature of than aluminum.

[0007] In addition, copper has a much higher melting point than aluminum. During the welding process, aluminum melts first, while copper is difficult to melt.

[0008] Furthermore, the difference in thermal expansion coefficients and solidification shrinkage rates between aluminum and copper generates significant thermal stress in the copper-aluminum weld zone during solidification and cooling. This thermal stress acts on the brittle mesophase, causing cracks and promoting crack propagation, ultimately leading to failure.

[0009] Ultimately, the high reflectivity of copper and aluminum to infrared wavelengths makes it difficult for them to absorb laser energy. The brittle intermediate phase Al2Cu generated by the eutectic reaction causes low mechanical strength, low impact toughness, and low ability to prevent crack propagation in the copper-aluminum weld zone. Summary of the Invention

[0010] Based on the technical problems existing in the background art, the present invention proposes a laser and method for welding copper and aluminum.

[0011] This invention proposes a laser for welding copper and aluminum. The laser for welding copper and aluminum is a semiconductor laser with a laser wavelength of 360 nm to 470 nm, an optical power of 100 W to 4000 W, and a laser spot diameter of 0.1 mm to 0.6 mm. The laser includes a blue laser emission module, a collimating lens, a cylindrical lens, and a condenser lens, arranged from top to bottom.

[0012] Preferably, the laser wavelength is 405 nm to 470 nm, and the laser spot diameter is 0.1 mm to 0.6 mm, which can ensure welding efficiency.

[0013] Preferably, the optical system of the laser passes through a spot correction lens, a collimating lens, a cylindrical lens and a condenser lens in sequence along the optical path. The cylindrical lens has a through hole in the center to limit the output diameter of the light beam.

[0014] A method for welding copper and aluminum includes the following steps: S1: Prepare copper and aluminum plate materials, fix them on the fixture respectively, align the splicing ends to obtain copper-aluminum splicing parts; S2: Preheat the copper-aluminum splice parts at a temperature of 300℃~500℃. S3: While the laser spot moves along the direction of the copper-aluminum weld, it is superimposed with the trajectory that starts from the copper side and moves to the aluminum side along the direction perpendicular to the weld. S4: The laser uses pulsed power output mode to finally complete the welding of copper and aluminum.

[0015] Preferably, in step S2, a high-frequency induction heating device is used for preheating, which has a good preheating effect.

[0016] Preferably, in step S3, the laser moves a distance of 3 to 10 laser spot sizes along the direction perpendicular to the weld, the laser moves at a speed of 5 mm / s along the weld direction, and moves at a speed of 10 mm / s along the direction perpendicular to the weld, which can ensure the welding effect.

[0017] Preferably, in step S4, the duty cycle of the pulse power is 50% to 90%, the pulse width is 5ms to 50ms, the power intensity of the laser in the copper region is higher than that in the aluminum region, and the intensity ratio is 1.5:1 to 5:1. During the laser's travel from the aluminum side back to the copper side, the power is adjusted to zero, which can ensure the welding effect.

[0018] Preferably, the duty cycle of the pulse power is 80%, the pulse width is 10ms, the power intensity ratio is 2:1, and the laser moves a distance of 5 laser spot sizes along the direction perpendicular to the weld seam, which can provide a preferred solution.

[0019] Preferably, in step S1, the copper plate is made of pure copper with a copper content greater than 99.7%, and the aluminum plate is made of 1050 aluminum with an aluminum content greater than 99.6%. The thickness of both the copper and aluminum plates is 0.5 mm, and the splicing ends of the copper and aluminum plates are flat, which can ensure the flush splicing and facilitate subsequent welding.

[0020] Preferably, the laser moves a distance perpendicular to the weld seam that is 2 to 10 times the size of the laser spot, with the optimal value being 4 times. After welding, the resulting non-equilibrium eutectic structure is subjected to tempering heat treatment to eliminate the structure, resulting in a good welding effect.

[0021] The beneficial effects of this invention are: The process employs a "zone melting" technique similar to that used in the semiconductor industry to remove impurities. It utilizes a blue laser with a wavelength of 400nm to 470nm. Within this wavelength range, copper can achieve an absorption rate of over 50%. During or after welding, the laser is guided to move from the weld seam, perpendicular to the weld seam, and toward the aluminum. This drives the copper enriched near the weld seam into the deeper layers of the aluminum, thereby eliminating or reducing the formation of the brittle eutectic phase Al2Cu. Attached Figure Description

[0022] Figure 1 This invention illustrates the relationship between the percentage of light absorption and the wavelength of the light source in a laser and method for welding copper and aluminum. Figure 2 The aluminum-copper binary phase diagram for a laser and method for welding copper and aluminum proposed in this invention; Figure 3 The aluminum enrichment diagram in the aluminum-copper binary phase diagram is for the laser and method for welding copper and aluminum proposed in this invention. Figure 4 Blue laser welding diagram of a laser and method for welding copper and aluminum proposed in this invention; Figure 5 This is a schematic diagram of the "zone melting" process of a laser and method for welding copper and aluminum proposed in this invention; Figure 6This is a diagram illustrating the solidification process of a liquid aluminum-copper alloy in a laser and method for welding copper and aluminum, as proposed in this invention. Figure 7 This is a graph showing the variation of laser power with the laser welding trajectory for a laser and method for welding copper and aluminum proposed in this invention. Figure 8 This is a flowchart of a laser and method for welding copper and aluminum proposed in this invention. Detailed Implementation

[0023] The present invention will be further explained below with reference to specific embodiments. Example

[0024] refer to Figure 1-8 This embodiment proposes a laser for welding copper and aluminum. The laser for welding copper and aluminum is a semiconductor laser with a laser wavelength of 360 nm to 470 nm, an optical power of 100 W to 4000 W, and a laser spot diameter of 0.1 mm to 0.6 mm. The laser includes a blue laser emission module, a collimating lens, a cylindrical lens, and a condenser lens, arranged from top to bottom. The laser wavelength is 405 nm to 470 nm, and the laser spot diameter is 0.1 mm to 0.6 mm. The optical system of the laser passes through a spot correction lens, a collimating lens, a cylindrical lens and a condenser lens in sequence along the optical path. The cylindrical lens has a through hole in the center to limit the output diameter of the light beam. A method for welding copper and aluminum includes the following steps: S1: Prepare copper and aluminum plate materials. The copper plate is made of pure copper with a copper content greater than 99.7%, and the aluminum plate is made of 1050 aluminum with an aluminum content greater than 99.6%. The thickness of both copper and aluminum plates is 0.5mm. The splicing ends of the copper and aluminum plates are flat and fixed on the fixtures respectively. The splicing ends are aligned to obtain the copper-aluminum splicing parts. S2: Preheat the copper-aluminum splice parts at a temperature of 300℃~500℃ using a high-frequency induction heating device. S3: While the laser spot moves along the copper-aluminum weld seam, a trajectory is superimposed, starting from the copper side and moving perpendicular to the weld seam to the aluminum side. The laser's movement distance perpendicular to the weld seam is 3 to 10 times the laser spot size. The laser's movement speed along the weld seam is 5 mm / s, and its movement speed perpendicular to the weld seam is 10 mm / s. The laser's movement distance perpendicular to the weld seam is 2 to 10 times the laser spot size, with an optimal value of 4 times. After welding, the resulting non-equilibrium eutectic structure is subjected to tempering heat treatment to eliminate the structure. S4: The laser adopts a pulsed power output mode with a pulse power duty cycle of 50% to 90% and a pulse width of 5ms to 50ms. The power intensity of the laser in the copper area is higher than that in the aluminum area, with an intensity ratio of 1.5:1 to 5:1. During the laser's movement from the aluminum side back to the copper side, the power is adjusted to zero. The pulse power duty cycle is 80%, the pulse width is 10ms, and the power intensity ratio is 2:1. The laser moves a distance of 5 laser spot sizes along the direction perpendicular to the weld seam, ultimately completing the copper-aluminum welding.

[0025]

[0026] The low absorption rates of copper and aluminum at certain wavelengths: Figure 1 This shows the relationship between the light absorption rate and light wavelength of some metals, including copper and aluminum. Currently, the most widely used welding equipment in the domestic market is the infrared-wavelength fiber laser, such as the 1064 nm Nd / YAG laser. Around this wavelength, such as… Figure 1 The data shows that copper has almost zero absorption, while aluminum has less than 5% absorption. Copper's absorption rate increases sharply at a wavelength of approximately 750 nm as the wavelength decreases. In the green light wavelength range of 520 nm to 550 nm, the absorption rate is close to 40%, in the blue light wavelength range of 450 nm, the absorption rate is close to 50%, and in the ultraviolet wavelength range of approximately 300 nm, the absorption rate reaches a peak of nearly 70%. As for aluminum, the figure shows that its absorption rate is very low (<10%) across the entire wavelength range from ultraviolet to infrared. Although the absorption rate tends to increase as the wavelength decreases, it has a peak absorption rate of approximately 14% in the 750 nm to 850 nm range.

[0027] Literature reports that the absorption rate of light waves by metals increases with increasing temperature. The main related factor is the concentration of free electrons in the metal. The higher the concentration of free electrons, the stronger the ability to reflect light waves. The electrical conductivity of metals decreases with increasing temperature, and the ability to reflect light waves decreases accordingly.

[0028] Infrared fiber lasers have long been technologically mature and industrialized, but semiconductor blue lasers have been hampered by limitations in materials, cost, and technology, with power levels hovering between a few watts and tens of watts, becoming a bottleneck in laser technology development.

[0029] In 2015, German semiconductor laser manufacturer DILAS launched its first blue visible light semiconductor laser system with a wavelength of 450nm and a maximum output power of 25 watts. It uses fiber core diameters of 200μm or 400μm and can be extended to 100 watts, which can be used for materials processing. In the same year, Shimadzu Corporation of Japan announced the successful development of the fiber-coupled high-brightness blue direct diode laser "BLUE IMPACT", which uses blue gallium nitride semiconductor laser and is the world's first laser processing light source to be commercialized.

[0030] In 2017, the American company Nuburu first developed a blue semiconductor laser, followed by a 150W laser in 2018 and a 500W laser in 2019. In 2019, the German company Laserline showcased the world's first 1kW commercial blue semiconductor laser at the Shanghai International Optoelectronic Exposition.

[0031] This patent uses a self-made 400nm-450nm light ultraviolet-blue wavelength laser, which greatly improves the absorption efficiency of copper and aluminum compared with infrared lasers widely used in laser welding on the market, making copper-aluminum welding possible.

[0032] The binary phase diagram of copper and aluminum is as follows: Figure 2 and Figure 3 As shown in the phase diagram, the copper-rich portion shows that the solubility of aluminum in copper is as high as nearly 20 at%, meaning that 8 copper atoms can accommodate 2 aluminum atoms. The copper-aluminum weld zone is adjacent to the solidified area of ​​the copper portion. Due to the extremely high solubility of aluminum in copper, it is mainly a copper-aluminum solid solution.

[0033] Although the solid solution of aluminum in copper produces a solid solution strengthening effect, its effect on yield strength, tensile strength, and elongation is generally less significant than that of precipitation phase strengthening.

[0034] In addition, copper-aluminum solution treatment is not sensitive to post-weld heat treatment, and its mechanical properties do not change much.

[0035] In the aluminum enrichment section ( Figure 3 However, the situation is quite different.

[0036] The solubility of copper in aluminum crystal structure is very limited; at 300℃, the solubility of copper in aluminum is only 0.45 wt%.

[0037] At the eutectic temperature of α(Al)-θ(Al2Cu) of 548℃, the solubility of copper in aluminum increases to 5.7wt%, which is significantly different from the solubility at 300℃.

[0038] If the copper content in the aluminum-copper alloy is less than 5.7 wt%, only α(Al) will precipitate during solidification.

[0039] If the copper content in the aluminum-copper alloy is more than 5.7 wt%, during the solidification process, the α(Al) phase, which has a lower copper content than the overall composition, will precipitate first, and the excess copper will be discharged into the liquid, thus increasing the copper content of the liquid.

[0040] When the temperature drops to the eutectic temperature of 548℃, the remaining liquid containing 33.2% copper undergoes a eutectic reaction to generate α(Al) and the intermediate phase θ(Al2Cu).

[0041] The microstructure of the eutectic reaction is that the α (Al) and intermediate phase θ (Al2Cu) are arranged in a lamellar pattern with alternating intervals. The two phases are "eutectic", that is, the phase interface between the α phase and the θ phase has a coherent relationship with fixed crystal planes.

[0042] This eutectic microstructure has little to no slip surface and dislocation structure required for plastic deformation, making it difficult to produce plastic deformation. This is the fundamental reason for the low strength and high brittleness of the copper-aluminum weld interface.

[0043] Figure 3 The results show that a eutectic reaction and a brittle eutectic structure will only occur when the copper content in the aluminum-copper alloy exceeds 5.7 wt% and the alloy solidifies from the liquid state.

[0044] Therefore, avoiding a copper content exceeding 5.7 wt% in the fusion zone during copper-aluminum laser welding is one of the effective methods to reduce the brittleness of copper-aluminum welds.

[0045] Figure 3 It is an equilibrium phase diagram. In the actual solidification process of aluminum-copper alloys, even if the copper content is less than 5.7 wt%, a non-equilibrium eutectic structure will be generated. However, this non-equilibrium eutectic structure can be eliminated by tempering heat treatment.

[0046] This invention employs a "zone melting" process similar to that used in the semiconductor industry to remove impurities. During the copper-aluminum welding process, a laser spot is added that travels from the weld seam perpendicularly to the weld seam and penetrates deep into the aluminum. This drives the copper atoms enriched in the weld seam into the deeper parts of the aluminum, reducing the concentration of copper atoms in the weld seam and decreasing the formation of brittle eutectic structures.

[0047] Direct laser fusion between copper and aluminum is rarely reported in the literature and has always been considered very difficult, mainly due to two challenges: how to improve the absorption efficiency of infrared lasers on copper surfaces and how to reduce brittle mesophases.

[0048] There are copper-aluminum welding transition joints on the market, with one side being copper and the other side being aluminum, which transforms the fusion welding between copper and aluminum into one side being copper-copper fusion welding and the other side being aluminum-aluminum fusion welding.

[0049] To eliminate the brittle mesophase θ (Al₂Cu) at the copper-aluminum weld interface, according to US 4224 499, General Electric uses a 1.06µm YAG laser for the welding of copper and aluminum.

[0050] Pulsed laser welding is performed while maintaining a contact interface of 100psi to 350psi between copper and aluminum.

[0051] The pressure at the contact surface forces the molten material out of the weld joint.

[0052] The molten material contains a large amount of brittle mesophase Al2Cu, while the remaining narrow and deep molten zone is basically free of brittle mesophase Al2Cu. The disadvantage of this method is that pressures of 100psi to 350psi are difficult to achieve in many specific applications.

[0053] This invention proposes a novel method for welding copper and aluminum using a blue laser with a wavelength of 400nm to 470nm. Within this wavelength range, the absorption rate of copper can reach over 50%. During or after welding, the laser is guided to move along a path perpendicular to the weld and toward the aluminum, driving the copper enriched near the weld into the deeper layers of the aluminum, thereby eliminating or reducing the formation of the brittle eutectic phase Al2Cu.

[0054] Lasers employing laser diodes with wavelengths in the range of 360 nm to 470 nm are preferred, with laser diode lasers having wavelengths in the range of 405 nm to 470 nm.

[0055] See the schematic diagram of the laser structure. Figure 4 : Laser source 1 uses a self-produced laser diode laser source with an optical power of 100 watts to 400 watts. The optical system of the laser can be designed in many different ways. This example is given to illustrate the principle and does not exclude other design possibilities.

[0056] Starting from light source 1, along the optical path is a spot correction lens, which adjusts the divergence angle of the laser's fast and slow axes; then comes collimating lens 2, which transforms the diverging beam into a parallel collimated beam; then comes cylindrical lens 3, which has a through-hole in the center to limit the output diameter of the beam; and then comes condenser lens, which focuses the parallel light at the focal point.

[0057] To reduce the accumulation of copper atoms on the aluminum edge of the weld, a method similar to "zone melting" used in the semiconductor industry to remove impurities is employed.

[0058] Figure 5 This is a schematic diagram of zone melting: A cylindrical rod containing impurities in a semiconductor material moves through a heating coil, which melts part of the rod, forming a local melting zone. The melting zone moves sequentially from one end of the rod to the other. The solubility of impurities in the solid state of the semiconductor material is lower than its solubility in the liquid state. Therefore, the impurity concentration in the solidified solid left behind after the melting zone moves is lower than the impurity concentration in the molten liquid before the melting zone moves.

[0059] As the melting zone moves from one end of the round bar to the other, the impurity concentration at the starting end is much lower than that at the ending end. The portion with high impurity concentration at the ending end is cut off, and the process of regional melting is repeated to further remove impurities from the material.

[0060] Figure 6It is part of the aluminum-copper binary phase diagram, showing the upper right region as the liquid phase L, the lower left region as the solid phase α (Al), and the middle region as the L+α two-phase region.

[0061] The composition of the solid and liquid phases changes with temperature as Cs and CL lines, respectively. At the same temperature, the ratio of the composition of the solid and liquid phases, k0 = Cs / CL, is called the segregation coefficient. K < 1 means that the solubility of the solid phase is lower than that of the liquid phase.

[0062] Figure 6 The result shows that k0 = 5.72 / 33.2 = 0.17, which means that the ratio of the copper-containing component of the solid phase precipitated from the liquid phase to the original component of the liquid phase is 0.17.

[0063] Figure 6 The text also provides a specific example: when a liquid phase containing 15% copper begins to solidify, the copper content of the solid phase is 2.6%, and the excess copper, 15% - 2.6% = 12.4%, is discharged into the liquid phase.

[0064] The main points of the laser welding process are as follows: Preheating the copper-aluminum joint to 300℃~500℃ is to improve the absorption rate of the laser, whether it is infrared or blue light. Increasing the temperature can improve the absorption rate of the metal material to the laser. Due to the high heat capacity and high thermal conductivity of copper, it is difficult to heat copper locally. Preheating can also reduce the power required for laser welding. Preheating can be done in an additional preheating furnace, such as a high-frequency induction heating device.

[0065] The laser beam starts on the copper side of the copper-aluminum joint. After the copper melts, it moves from the copper side to the aluminum side along a direction perpendicular to the copper-aluminum joint. Then it returns to the copper side and begins the next cycle of movement. When the laser beam returns from the aluminum side to the copper side, the laser power is zero or very low. The length of the laser beam's movement trajectory perpendicular to the weld is 2 to 10 times the size of the laser spot, with 4 times being optimal.

[0066] Laser power changes over time as follows Figure 7 As shown: Pulse power output is adopted, with a pulse duty cycle of 50% to 90%, the optimal value being 80%, and a pulse width of 5ms to 50ms, the optimal value being 10ms. The pulse power intensity is higher in the copper region than in the aluminum region, with an intensity ratio ranging from 5:1 to 1.5:1, the optimal value being 2:1. During the movement of the laser beam from one side of the aluminum to the other side of the copper, the laser power adjustment is zero.

[0067] This invention relates to a laser welding device and method for welding aluminum and copper together. The main purpose is to increase the absorption rate of the welded materials to the laser and reduce the brittleness of the weld area. A 360nm-470nm wavelength blue semiconductor laser with a significantly improved copper absorption rate is used. During the welding of the copper and aluminum joint, while the laser spot moves along the weld seam, a superimposed laser spot moves from the copper to the aluminum along a direction perpendicular to the copper-aluminum weld seam. This is similar to the "zone melting" process for removing impurities from semiconductors. This spot movement trajectory sweeps away the copper enriched in the weld seam, making the copper evenly distributed on the aluminum edge of the weld seam, thereby avoiding or reducing the formation of the brittle mesophase Al2Cu in the weld seam.

[0068] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A laser for welding copper aluminum, characterized by, The laser for welding copper-aluminum adopts a semiconductor laser, the laser wavelength is 360nm-470nm, the light power is 100w-4000w, the laser spot diameter is 0.1mm-0.6mm, the laser comprises a blue laser light emitting module, a collimating lens, a cylindrical lens and a condenser lens, and the blue laser light emitting module, the collimating lens, the cylindrical lens and the condenser lens are arranged from top to bottom.

2. A laser soldered copper-aluminum according to claim 1, wherein, The laser wavelength is 405nm-470nm, and the laser spot diameter is 0.1mm-0.6mm.

3. The laser welded copper-aluminum of claim 1, wherein, The optical system of the laser sequentially passes through a spot correction lens, a collimating lens, a cylindrical lens and a condenser lens along an optical path, and the cylindrical lens is provided with a through hole in the center.

4. The method of claim 1, wherein The method comprises the following steps: S1: prepare copper plate and aluminum plate materials, respectively fixed on the fixture, align the splicing port, and obtain a copper-aluminum splicing piece; S2: preheat the copper-aluminum splicing piece, the preheating temperature is 300-500 DEG C; S3: while the laser spot moves along the copper-aluminum weld seam direction, superimpose the trajectory from the copper side to the aluminum side along the direction perpendicular to the weld seam; S4: the laser adopts pulse power output mode, and finally completes the welding of copper-aluminum.

5. The method of claim 4, wherein the brazing of the copper to the aluminum is performed at a temperature of about 500 °C to about 600 °C. In S2, a high-frequency induction heating device is used for preheating.

6. The method of claim 4, wherein the brazing of the copper to the aluminum is performed at a temperature of about 500 °C to about 600 °C. In S3, the moving distance of the laser along the direction perpendicular to the weld seam is 3-10 laser spot sizes, the moving speed of the laser along the weld seam direction is 5mm / s, and the moving speed of the laser along the direction perpendicular to the weld seam is 10mm / s.

7. The method of claim 4, wherein the brazing of the copper to the aluminum is performed at a temperature of about 500 °C to about 600 °C. In S4, the duty cycle of the pulse power is 50%-90%, the pulse width is 5ms-50ms, the power intensity of the laser in the copper area is higher than that in the aluminum area, the intensity ratio is 1.5:1 to 5:1, and the power adjustment is zero in the moving stroke of the laser from the aluminum side to the copper side.

8. The method of claim 7, wherein the welding of the copper to the aluminum is performed at a temperature of about 200 °C to about 300 °C. The duty cycle of the pulse power is 80%, the pulse width is 10ms, the power intensity ratio is 2:1, and the moving distance of the laser along the direction perpendicular to the weld seam is 5 laser spot sizes.

9. The method of claim 4, wherein the welding of the copper to the aluminum is performed at a temperature of about 200°C to about 300°C. In S1, the copper plate adopts red copper, the copper content is greater than 99.7%, the aluminum plate adopts 1050 aluminum, the aluminum content is greater than 99.6%, the thickness of the copper plate and the aluminum plate is 0.5mm, and the splicing end face of the copper plate and the aluminum plate is flat.

10. The method of claim 4, wherein the welding of the copper and aluminum is characterized by, The moving distance of the laser along the direction perpendicular to the weld seam is 2-10 times the laser spot size, and the best is 4 times; after welding, the non-equilibrium eutectic structure is subjected to tempering heat treatment to eliminate the structure.

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