An ultrafast laser welding device for sapphire and metal

Abstract

The utility model relates to the technical field of superfast laser welding, and concretely relates to a superfast laser welding device for sapphire and metal. The device comprises a superfast laser unit and a fixed pressure applying unit. The fixed pressure applying unit comprises a shell, a base and a cover plate arranged at the two ends of the shell, a first pressure plate and a second pressure plate arranged in the shell, the first pressure plate located on the side close to the cover plate, a sapphire plate and a metal plate located between the first pressure plate and the second pressure plate, the sapphire plate located on the side close to the first pressure plate, a through hole arranged on the cover plate, the first pressure plate made of transparent material capable of transmitting superfast laser beams, and a pressure applying component arranged on the base for applying pressure to the second pressure plate. The shell further comprises a pressure sensor. The device can be directly used for superfast laser welding of metal materials and sapphire with surface roughness in the micron level, thereby reducing the requirement for surface roughness, lowering the processing difficulty and processing cost, and significantly improving the processing efficiency.

Description

Technical Field

[0001] This utility model relates to the field of ultrafast laser welding technology, and more specifically, to an ultrafast laser welding device for sapphire and metal. Background Technology

[0002] Sapphire (also known as corundum) is an inorganic non-metallic material composed of single-crystal α-Al₂O₃, with an Al₂O₃ content as high as 99.99%. Sapphire possesses excellent physical and chemical properties, including a hardness second only to diamond, stable chemical properties, good mechanical properties, and high-temperature resistance. Furthermore, sapphire exhibits excellent light transmittance in the ultraviolet to infrared region, reaching up to 87%, thus finding wide application in electronic component packaging substrates, high-speed aircraft fairings, and optical windows. In practical applications, sapphire often needs to be bonded to metallic materials to achieve its integrated application in complex structural systems, such as infrared detector windows, high-power waveguide windows, electronic devices, and vacuum equipment. Therefore, the bonding technology between sapphire and metals has become one of the key technologies restricting its engineering applications.

[0003] Traditional welding methods for joining sapphire and metals present numerous challenges. For instance, conventional continuous laser welding involves high heat input, easily leading to cracks, ablation, or even fragmentation of the sapphire, severely impacting the join quality and structural integrity. In recent years, ultrafast laser (femtosecond and picosecond) welding technology, with its extremely short pulse width, small heat-affected zone, high energy density, non-contact heating, and high flexibility, can induce nonlinear absorption effects and local phase transitions in transparent materials, achieving high-quality welding without damaging the material itself. However, existing ultrafast laser welding technologies still present the following problems when used to join sapphire and metals: First, the surface roughness requirements for the welding materials are extremely high, typically requiring optical contact or nanoscale roughness. This not only increases the processing difficulty and cost but also reduces processing efficiency. Currently, the clamping force applied during ultrafast laser welding of sapphire and metal is uneven, and the magnitude of the interfacial pressure cannot be controlled, making it difficult to maintain stable welding quality, resulting in insufficient welding strength or uneven interfacial bonding. Furthermore, the lack of effective auxiliary means (such as pressure control and inert gas) to improve interfacial bonding strength during the welding process further limits the widespread application of this technology in industry.

[0004] To address the aforementioned issues, there is an urgent need to develop a structurally sound, easy-to-operate, and highly adaptable interface pressure-assisted ultrafast laser welding device. This device would solve the technical bottlenecks in ultrafast laser welding of sapphire and metals, such as high surface roughness requirements, low processing efficiency, and low interface bonding strength. This would promote the application of this technology in high-end manufacturing fields such as precision optical devices, semiconductor packaging, and aerospace.

[0005] In view of the above, this utility model is hereby proposed. Utility Model Content

[0006] The purpose of this invention is to provide an ultrafast laser welding device for sapphire and metal, in order to solve the technical problems of uneven clamping force, inability to control pressure, high requirements for surface roughness of the welding material, and inability to achieve inert gas protection in existing ultrafast laser welding devices.

[0007] In order to achieve the above-mentioned objectives of this utility model, the following technical solution is adopted: This invention provides an ultrafast laser welding device for sapphire and metal, comprising an ultrafast laser unit and a fixed pressure unit; The fixed pressure unit includes a housing with openings at both ends. A base and a cover plate are respectively provided at both ends of the housing. A first pressure plate and a second pressure plate are provided inside the housing. The first pressure plate is located on the side of the second pressure plate near the cover plate. A sapphire plate and a metal plate are located between the first pressure plate and the second pressure plate. The sapphire plate is located on the side near the first pressure plate. A through hole is provided on the cover plate. The first pressure plate is a transparent material that can transmit ultrafast laser beams for the passage of ultrafast laser beams. The base is provided with a pressure applying component for applying pressure to the second pressure plate, and the housing is also provided with a pressure sensor for real-time monitoring of the pressure on the second pressure plate.

[0008] Furthermore, the housing is provided with a pressure sensor base that slides with the inner wall of the housing. The pressure sensor is located between the second pressure plate and the pressure sensor base and is fixedly connected to the pressure sensor base. The pressure applying component includes a clamping screw that is threadedly connected to the base. One end of the clamping screw located inside the housing contacts the pressure sensor base.

[0009] Furthermore, a motor is connected to the end of the clamping screw away from the pressure sensor base, and both the motor and the pressure sensor are connected to a controller.

[0010] Furthermore, the housing is provided with an air inlet and an air outlet.

[0011] Furthermore, the housing, the cover plate, and the base are connected by bolts and nuts.

[0012] Furthermore, the first pressure plate is made of sapphire, which can transmit light in the range of 300nm-5000nm and has a transmittance of more than 87%.

[0013] Furthermore, the thickness of the first pressure plate is 1mm-2mm.

[0014] Furthermore, the sapphire substrate has a thickness of 1-5mm, and the sapphire substrate can transmit light in the range of 300nm-5000nm with a transmittance greater than 87%.

[0015] Furthermore, the metal sheet comprises any one of titanium alloy, copper, or Invar alloy.

[0016] Furthermore, the ultrafast laser unit includes an ultrafast laser, and also includes a beam expander, a reflector, and a focusing galvanometer arranged sequentially along the ultrafast laser beam direction of the ultrafast laser.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows: This invention, by setting a fixed pressure unit in an ultrafast laser welding device, can uniformly apply pressure to the stack of sapphire and metal plates during ultrafast laser welding and can adjust the magnitude of the interface pressure. By applying appropriate interface pressure, the surface of the metal material is induced to undergo slight deformation, increasing the contact area between the metal and sapphire, reducing the welding gap, and improving welding quality and process stability through interface pressure assistance. It also significantly improves the shear strength of the welded joint. This device can be used for ultrafast laser welding of metal materials and sapphire with surface roughness in the micrometer range, eliminating the need for strict nanoscale surface treatment, reducing the requirements for surface roughness of the welding materials, greatly reducing processing difficulty and cost, and significantly improving processing efficiency. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the overall structure of the welding device provided in this embodiment of the present invention during operation; Figure 2 A schematic diagram of the overall structure of the fixed pressure application unit provided in this embodiment of the utility model; Figure 3 This is a schematic diagram of the internal structure of the fixed pressure application unit provided in an embodiment of the present invention; Figure 4 A schematic diagram showing the interface between the sapphire sheet and the metal sheet before applying the pressure load. Figure 5 A schematic diagram showing the application of a pressure load at the interface between a sapphire substrate and a metal substrate. Figure 6These are surface morphology diagrams of the sapphire-titanium alloy welded joints in Embodiment 1 and Comparative Examples 3-6 of this utility model. Figure 7 The images show the weld morphology and EDS scan location data of the sapphire-titanium alloy welded joint in Comparative Example 2 and Example 1 of this invention.

[0020] Figure label: 1-Ultrafast laser; 2-Beam expander; 3-Reflector; 4-Focusing galvanometer; 5-Sapphire plate; 6-Metal plate; 7-Pressure load; 8-Ultrafast laser beam; 9-Welding trajectory; 10-Bolt; 11-Cover plate; 12-Housing; 13-Nut; 14-Base; 15-First pressure plate; 16-Second pressure plate; 17-Pressure sensor; 18-Pressure sensor base; 19-Clamping screw; 20-Air inlet; 21-Air outlet. Detailed Implementation

[0021] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this utility model, not all embodiments, and are only used to illustrate this utility model, and should not be regarded as limiting the scope of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0022] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," 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 this utility model 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 a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0023] like Figure 1 As shown, this utility model provides an ultrafast laser welding device for sapphire and metal, including an ultrafast laser unit and a fixed pressure unit; like Figure 2 and Figure 3 As shown, the fixed pressure unit includes a housing 12 with openings at both ends. The two ends of the housing 12 are respectively provided with a base 14 and a cover plate 11. The housing 12 is provided with a first pressure plate 15 and a second pressure plate 16. The first pressure plate 15 is located on the side of the second pressure plate 16 near the cover plate 11. A sapphire plate 5 and a metal plate 6 are located between the first pressure plate 15 and the second pressure plate 16. The sapphire plate 5 is located on the side near the first pressure plate 15. A through hole is provided on the cover plate 11. The first pressure plate 15 is a transparent material that can transmit ultrafast laser beams for the ultrafast laser beam to pass through. The base 14 is provided with a pressure application component for applying pressure to the second pressure plate 16, and the housing 12 is also provided with a pressure sensor 17 for real-time monitoring of the pressure on the second pressure plate 16.

[0024] This invention incorporates a fixed pressure unit within an ultrafast laser welding device. During ultrafast laser welding, a first pressure plate 15 and a second pressure plate 16 are used to fix the sapphire plate 5 and the metal plate 6 and apply pressure to them, improving the uniformity of pressure application. The first pressure plate 15 is made of a transparent material that can be penetrated by the ultrafast laser beam, and an opening is provided on the cover plate 11. The first pressure plate 15 completely covers the opening and contacts the inner wall of the cover plate 11. The purpose is to ensure that, while applying fixed pressure, the ultrafast laser beam 8 can act on the joint between the sapphire plate 5 and the metal plate 6 through the cover plate 11 and the first pressure plate 15, forming localized melting and achieving effective welding of the sapphire plate 5 and the metal plate 6. Figure 4 As shown, before the interfacial pressure is applied, due to the high roughness of the metal plate 6, a gap is generated at the joint between the sapphire plate 5 and the metal plate 6. Direct ultrafast laser welding makes it difficult to achieve an effective connection between the sapphire and the metal. However, as... Figure 5 As shown, with the cover plate 11 and the first pressure plate 15 fixed, a pressure load 7 is applied to the second pressure plate 16 through the pressure applying component. The pressure is transmitted to the metal plate 6, causing a slight deformation on the surface of the metal plate 6, which can increase the contact area between the metal and the sapphire, reduce the welding gap, and thus improve the welding quality. The pressure sensor 17 can monitor the pressure applied to the second pressure plate 16 in real time, so as to facilitate accurate control of the interface pressure. This device is suitable for ultrafast laser welding of metal materials and sapphire with surface roughness in the micrometer range. It reduces the requirements for the surface roughness of the welding material in the ultrafast laser welding process, greatly reduces the processing difficulty and processing cost, and significantly improves the processing efficiency.

[0025] In some specific embodiments of this utility model, a pressure sensor base 18 is provided inside the housing 12 and slides with the inner wall of the housing 12. The pressure sensor 17 is located between the second pressure plate 16 and the pressure sensor base 18 and is fixedly connected to the pressure sensor base 18. The pressure application component includes a clamping screw 19 threadedly connected to the base 14. One end of the clamping screw 19 located inside the housing 12 contacts the pressure sensor base 18. By rotating the clamping screw 19, the pressure sensor base 18 can be driven to slide up and down along the inner wall of the housing, adjusting the pressure load applied to the second pressure plate 16, thereby achieving the purpose of adjusting the pressure at the interface between the metal material and the sapphire.

[0026] In some specific embodiments of this utility model, the inner wall of the housing 12 has a rectangular cross-section perpendicular to the inner wall direction, and the pressure sensor base 18 is a rectangular plate adapted to the inner wall size of the housing 12.

[0027] In some other embodiments, the cross-section of the inner wall of the housing 12 along the direction perpendicular to the inner wall can also be other shapes, such as a circle. To prevent the pressure sensor base 18 from rotating, a groove is provided on the inner wall of the housing 12, and a slider that slides in cooperation with the groove is provided on the side of the pressure sensor base 18.

[0028] In some specific embodiments of this utility model, a motor is connected to the end of the clamping screw 19 away from the pressure sensor base 18, and both the motor and the pressure sensor 17 are connected to the controller. During ultrafast laser welding, the pressure sensor 17 transmits the detected pressure signal to the controller. When the pressure is not appropriate, the controller can transmit a signal to the motor to control the motor to drive the clamping screw 19 to rotate, thereby realizing automatic adjustment and control of the interface pressure.

[0029] In some specific embodiments of this utility model, the housing 12 is provided with an air inlet 20 and an air outlet 21. The air inlet 20 is used to introduce inert gas into the housing 12, and the air outlet 21 is used to discharge the gas. The purpose is to provide an inert gas protective environment during the ultrafast laser welding process to avoid material oxidation.

[0030] In some specific embodiments of this utility model, the housing 12, the cover plate 11 and the base 14 are fixedly connected together by bolts 10 and nuts 13.

[0031] In some specific embodiments of this utility model, the material of the first pressure plate 15 is sapphire, which can transmit light of 300nm-5000nm and has a transmittance of more than 87%; the purpose is to ensure that the ultrafast laser beam can pass through the first pressure plate 15 to reach the contact interface between the sapphire plate 5 and the metal plate 6.

[0032] In some specific embodiments of this utility model, the thickness of the first pressure plate 15 is 1mm-2mm. If the thickness is too thin, it is easy to break under pressure, and if the thickness is too thick, it will increase the energy attenuation when the ultrafast laser beam passes through, affecting the welding effect.

[0033] In some specific embodiments of this utility model, the thickness of the sapphire plate 5 is 1-5mm. For example, it can be any one value or a range of any two values ​​from 1mm, 2mm, 3mm, 4mm, to 5mm. By controlling the thickness of the sapphire to 1-5mm, the laser energy can penetrate and deposit better at the interface, achieving a better welding effect. The sapphire plate can transmit light in the range of 300nm-5000nm, and the transmittance is greater than 87%.

[0034] In some specific embodiments of this utility model, the metal plate 6 welded to the sapphire plate 5 includes any one of titanium alloy, copper or Invar alloy.

[0035] In some specific embodiments of this utility model, the ultrafast laser unit includes an ultrafast laser 1, and also includes a beam expander 2, a reflector 3 and a focusing galvanometer 4 arranged sequentially along the ultrafast laser beam direction of the ultrafast laser 1. The ultrafast laser 1 generates an ultrafast laser beam 8. After passing through the beam expander 2, the reflector 3 and the focusing galvanometer 4 in sequence, the ultrafast laser beam 8 is focused at the junction of the sapphire plate 5 and the metal plate 6, and a welding trajectory 9 is formed under the operation of the focusing galvanometer 4.

[0036] In some specific embodiments, the method for welding sapphire and metal using the ultrafast laser welding device for sapphire and metal provided by this utility model includes the following steps: S1. Pretreatment: Clean and dry the sapphire plate and the metal plate. The surface roughness Ra of the metal plate to be soldered is 0.5μm-1.6μm. S2. Assembly: The pre-treated sapphire sheet and metal sheet are stacked together, so that the surface of the sapphire sheet to be welded is in contact with the surface of the metal sheet to be welded. The sheet is placed between the first pressure plate and the second pressure plate, and pressure is applied to it by the pressure application component to generate interface pressure at the welding interface. S3. Welding: Under an inert atmosphere, an ultrafast laser welding process is used to weld the areas to be welded on sapphire and metal sheets. The welding process is as follows: Figure 1 As shown.

[0037] In existing technologies, ultrafast laser welding, with its advantages of high energy density, short pulse time, and extremely small heat-affected zone, can effectively avoid the large-scale thermal damage in traditional welding and successfully achieve the joining of sapphire and metal. However, existing ultrafast laser welding technology has extremely high requirements for the surface roughness of the material and the contact gap between sapphire and metal (needing to achieve optical contact or nanoscale roughness). This not only reduces processing efficiency but may also lead to unstable processing quality, limiting its widespread application in industry.

[0038] To address the aforementioned issues, this invention introduces interfacial pressure-assisted ultrafast laser welding technology. By applying interfacial pressure, the shear strength of the weld joint is significantly improved, while the surface roughness requirements of the materials to be welded are reduced. This allows for the welding of metal materials with micron-level roughness and sapphire without the need for stringent nanoscale surface treatment. This solves the problems of stringent surface roughness requirements and insufficient welding strength in existing technologies, improving not only processing efficiency but also welding quality and process stability. This device and method are applicable to the welding of various metal materials and sapphire, with a wide range of applications. The resulting weld joints can be widely used in precision optical devices, semiconductor packaging, and aerospace fields.

[0039] In some embodiments, step S1 further includes sanding the surface of the metal sheet to be welded with sandpaper to obtain a suitable surface roughness; for example, the surface roughness of the surface of the metal sheet to be welded can be any one value or a range of any two values ​​among 0.5µm, 0.6µm, 0.8µm, 1.0µm, 1.2µm, 1.4µm, and 1.6µm.

[0040] In some specific embodiments, in step S1, the cleaning involves immersing the sapphire plate and the metal plate in ethanol for ultrasonic cleaning, with the aim of removing contaminants from the surface of the welding materials.

[0041] In some specific embodiments, the surface roughness Ra of the sapphire plate to be welded is 0.3μm-0.5μm. For example, it can be any single value or a range of any two values ​​among 0.3μm, 0.35μm, 0.4μm, 0.45μm, and 0.5μm. When using the device of this invention for welding, neither the sapphire nor the metal material to be welded needs to be processed to a mirror finish or nanoscale roughness, which reduces the processing difficulty and processing cost, and significantly improves processing efficiency and the stability of the production process.

[0042] In some specific embodiments, in step S2, the applied pressure S0 satisfies: S-0.27≤S0≤S+0.27; in, , The unit of S is MPa, Ra 金denoted as , where is the surface roughness of the metal surface to be welded, in μm; HV is the Vickers hardness of the metal, in MPa; E is the elastic modulus of the metal, in GPa; and α, β, and γ are material constants. The parameters in the formula are shown in Table 1 when the metal materials are titanium alloy, Invar alloy, and copper, respectively. Table 1

[0043] The pressure S calculated using the above formula is the optimal applied pressure. S and Ra 金 A positive correlation exists: the higher the surface roughness of the metal, the more microscopic protrusions there are, requiring greater interfacial pressure to induce plastic deformation and fill the gap with the sapphire. Conversely, lower roughness results in a smoother surface, requiring less pressure to achieve close contact. Controlling the applied pressure within the range of S ± 0.27 yields good welding results. For example, S0 can be any single value or a range of any two values ​​from S-0.27, S-0.23, S-0.2, S-0.1, S-0.02, S, S+0.1, S+0.2, and S+0.27. A better result is achieved when S0 is equal to or close to S.

[0044] In some specific embodiments, ultrafast laser welding is femtosecond laser welding, and the laser power of femtosecond laser welding is 4.8W-14.0W, for example, it can be any single value or a range of any two values ​​from 4.8W, 5.2W, 7W, 8.1W, 10W, 12W, and 14W; the scanning speed is 10mm / s-15mm / s, for example, it can be any of 10mm / s, 11mm / s, 12mm / s, 13mm / s, 14mm / s, and 15mm / s. The value can be any single point or a range of any two points; the laser pulse width is 200fs-500fs, for example, it can be any single point or a range of any two points from 200fs, 250fs, 300fs, 350fs, 400fs, 450fs, and 500fs; the laser repetition frequency is 1MHz-20MHz, for example, it can be any single point or a range of any two points from 1MHz, 5MHz, 10MHz, 15MHz, and 20MHz.

[0045] In some specific embodiments, the laser wavelength for femtosecond laser welding is 1025nm-1035nm, for example, it can be any single value or a range of any two values ​​among 1025nm, 1028nm, 1030nm, 1032nm, and 1035nm; the laser focal position is -0.01mm to +0.01mm, for example, it can be any single value or a range of any two values ​​among -0.01mm, -0.005mm, 0mm, +0.005mm, and +0.01mm.

[0046] In some specific embodiments, the femtosecond laser welding process controls the welding path of the laser beam through a focusing galvanometer. The welding path is a parallel line, and the spacing between each scanning line is 50μm-100μm. For example, it can be any point value or a range of any two point values ​​among 50μm, 60μm, 70μm, 80μm, 90μm, and 100μm.

[0047] The following describes the solution with reference to specific application examples. All the following examples are implemented using the device provided by this utility model. The thickness of the first pressure plate of the device used in the examples and comparative examples is 1 mm.

[0048] Example 1 This embodiment involves welding sapphire to a TC4 titanium alloy sheet. The sapphire has dimensions of 20×20×1mm, and the titanium alloy has dimensions of 20×40×2mm. The Vickers hardness HV=350MPa, the elastic modulus E=110GPa, and the welding area is 4mm². 2 ; S1. Pretreatment: Use 400-grit sandpaper to polish the surface of the titanium alloy to be welded, so that its surface roughness Ra=1.6µm. Use finished sapphire with a surface roughness Ra=0.5µm. Soak the sapphire and titanium alloy in ethanol for ultrasonic cleaning to remove surface contaminants and dry them. S2. Assembly: The pre-treated sapphire and titanium alloy are stacked one on top of the other, with the titanium alloy below the sapphire, so that the solderable surface of the sapphire is in contact with the solderable surface of the titanium alloy. According to the formula, S = (0.035 × 3.18 + 0.25) × 1.6 + 0.15 = 0.73 MPa. The stacked sapphire and titanium alloy are fixed by a fixed pressure unit, and a pressure of 0.75 MPa is applied to them. S3. Welding: Under an inert atmosphere, femtosecond laser welding is used to weld the areas to be welded on sapphire and titanium alloy. The laser power is 8.1W, the scanning speed is 10 mm / s, the laser focus position is +0 mm, the laser wavelength is 1030 nm, the laser repetition frequency is 10 MHz, the laser pulse width is 211 fs, and the welding scan line spacing is 50 μm.

[0049] Example 2 Example 2 is similar to Example 1, except that in step S2, the pressure applied to the stacked sapphire and titanium alloy is 0.5 MPa, and all other conditions are the same as in Example 1.

[0050] Example 3 Example 3 is similar to Example 1, except that in step S2, the pressure applied to the stacked sapphire and titanium alloy is 1 MPa, and all other conditions are the same as in Example 1.

[0051] Example 4 This embodiment involves welding sapphire to a 4J36 Invar alloy sheet. The sapphire has dimensions of 20×20×1mm, and the 4J36 Invar alloy has dimensions of 20×40×2mm. The Vickers hardness HV=200MPa, the elastic modulus E=140GPa, and the welding area is 4mm². 2 ; S1. Pretreatment: Use 400-grit sandpaper to polish the surface of the 4J36 Invar alloy to be soldered, so that its surface roughness Ra=1.6µm. Use finished sapphire with a surface roughness Ra=0.5µm. Soak the sapphire and 4J36 Invar alloy in ethanol for ultrasonic cleaning to remove surface contaminants, and then dry them. S2. Assembly: The pre-treated sapphire and 4J36 Invar alloy are stacked one on top of the other, with the 4J36 Invar alloy below the sapphire, so that the solderable surface of the sapphire is in contact with the solderable surface of the 4J36 Invar alloy. According to the formula, S = (0.028 × 1.43 + 0.20) × 1.6 + 0.20 = 0.58 MPa is calculated. The stacked sapphire and 4J36 Invar alloy are fixed by a fixed pressure unit, and a pressure of 0.58 MPa is applied to them. S3. Welding: Under an inert atmosphere, femtosecond laser welding was used to weld the areas to be welded on sapphire and 4J36 Invar alloy. The laser power was 7.8W, the scanning speed was 10 mm / s, the laser focus position was +0 mm, the laser wavelength was 1030 nm, the laser repetition frequency was 10 MHz, the laser pulse width was 211 fs, and the welding scan line spacing was 50 μm.

[0052] Example 5 This embodiment involves welding sapphire to copper sheet. The sapphire size is 20×20×1mm, and the copper size is 20×40×2mm. The Vickers hardness HV=100MPa, the elastic modulus E=110GPa, and the welding area is 4mm². 2 ; S1. Pretreatment: Polish the copper surface to be soldered with 400-grit sandpaper to achieve a surface roughness Ra=1.6µm. Use finished sapphire with a surface roughness Ra=0.5µm. Soak the sapphire and copper in ethanol for ultrasonic cleaning to remove surface contaminants and then dry them. S2. Assembly: The pre-treated sapphire and copper are stacked one on top of the other, with the copper below the sapphire, so that the solderable surface of the sapphire is in contact with the solderable surface of the copper. According to the formula, S = (0.015 × 0.9 + 0.15) × 1.6 + 0.10 = 0.36 MPa. The stacked sapphire and copper are fixed by a fixed pressure unit, and a pressure of 0.36 MPa is applied to them. S3. Welding: Under an inert atmosphere, femtosecond laser welding is used to weld the areas to be welded on sapphire and copper. The laser power is 5.2W, the scanning speed is 10 mm / s, the laser focus position is +0 mm, the laser wavelength is 1030 nm, the laser repetition frequency is 10 MHz, the laser pulse width is 211 fs, and the welding scan line spacing is 50 μm.

[0053] Comparative Example 1 This comparative example involves welding sapphire to TC4 titanium alloy sheet. The sapphire dimensions are 20×20×1mm, and the titanium alloy dimensions are 40×40×2mm. The surface roughness of the sapphire surface to be welded is Ra0.5µm, and the surface roughness of the titanium alloy surface to be welded is Ra1.6µm. Continuous laser welding of the sapphire and titanium alloy was performed using the following parameters: laser power 1000W, welding speed 5mm / s, minimum spot radius 1mm, laser wavelength 1030nm, defocusing amount +0mm, and applied pressure load +0.25MPa.

[0054] Comparative Example 2 Comparative Example 2 is similar to Example 1, except that no pressure load is applied in step S2, and all other conditions are the same as in Example 1.

[0055] Comparative Example 3 Comparative Example 3 is similar to Example 1, except that the pressure applied in step S2 is 0.125 MPa, and all other conditions are the same as in Example 1.

[0056] Comparative Example 4 Comparative Example 4 is similar to Example 1, except that the pressure applied in step S2 is 0.25 MPa, and all other conditions are the same as in Example 1.

[0057] Comparative Example 5 Comparative Example 5 is similar to Example 1, except that the pressure applied in step S2 is 1.25 MPa, and all other conditions are the same as in Example 1.

[0058] Comparative Example 6 Comparative Example 6 is similar to Example 1, except that the pressure applied in step S2 is 1.75 MPa, and all other conditions are the same as in Example 1.

[0059] Comparative Example 7 Comparative Example 7 is similar to Example 1, except that the pressure applied in step S2 is 2.25 MPa, and all other conditions are the same as in Example 1.

[0060] Test case The shear strength of the welded joints obtained in each embodiment and comparative examples 2-7 was tested using a universal testing machine. The test was conducted according to GB / T 11363-2008, and the test results are shown in Table 2.

[0061] Table 2

[0062] As shown in Table 1, applying appropriate interfacial pressure during femtosecond laser welding enables the welding of sapphire with metal materials having surface roughness in the micrometer range, and the resulting joints exhibit high shear strength. When the surface roughness Ra of sapphire is 0.5µm and the surface roughness Ra of the metal is 1.6µm, the shear strengths of the welded joints of sapphire with 4J36 Invar alloy, copper, and titanium alloy can reach 120.0MPa, 122.5MPa, and 32.0MPa, respectively. This ensures welding quality while reducing polishing costs and improving production efficiency. Compared with Comparative Example 2, applying pressure significantly increases the shear strength of the weld. As the load increases, the shear strength of the weld first increases and then decreases. When the applied interfacial pressure is too high, the fixed gap becomes too small, causing severe cracking of the sapphire base material. Therefore, precise control of the interfacial pressure between the weldment components is necessary to achieve better welding quality.

[0063] Figure 6 The images show the surface morphology of the sapphire and titanium alloy welded joints in Embodiment 1 and Comparative Examples 3-6 of this utility model. (a) is the weld morphology, (b) is an enlarged view of region A, (c) is an enlarged view of region B, and (d) is an enlarged view of region C. Figure 6 It can be seen that when the applied interfacial pressure is appropriate, the weld is defect-free and the welding effect is good; when the applied interfacial pressure is too low (0.125MPa, 0.25MPa), complete welding cannot be achieved; when the applied pressure is too high (1.25MPa, 1.75MPa), cracks appear in the sapphire base material.

[0064] Figure 7 The figures show the weld morphology and EDS scan position data of the sapphire and titanium alloy welded joints in Comparative Example 2 and Example 1. (a) is the weld morphology of Comparative Example 2, (b) is the EDS scan position data of Comparative Example 2, (c) is the weld morphology of Example 1, and (d) is the EDS scan position data of Example 1. Figure 7It can be seen that when no interfacial pressure is applied, the sapphire and titanium alloy fail to bond tightly, with a significant gap at the interface. Numerous cracks form at the weld / base material interface, and O, Al, Ti, and V elements diffuse only at the interface. The sapphire and titanium alloy fail to form a metallurgical bond. When the interfacial pressure is 0.75 MPa, there is no gap between the sapphire and the titanium alloy base material, no cracks at the weld / base material interface, a uniform transition at the sapphire-titanium alloy connection without cracks, no significant fluctuations in elemental signals, and uniform element diffusion at the interface. The sapphire and titanium alloy can form a metallurgical bond.

[0065] In Comparative Example 1, after high-power continuous laser scanning, obvious ablation marks appeared on the surface of the titanium alloy, and the sapphire was completely broken. Effective connection between the sapphire and the titanium alloy could not be achieved, indicating that continuous laser welding is not suitable for high-quality connection between sapphire and metal.

[0066] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. An ultrafast laser welding device for sapphire and metal, characterized in that, Includes an ultrafast laser unit and a fixed pressure application unit; The fixed pressure unit includes a housing with openings at both ends. A base and a cover plate are respectively provided at both ends of the housing. A first pressure plate and a second pressure plate are provided inside the housing. The first pressure plate is located on the side of the second pressure plate near the cover plate. A sapphire plate and a metal plate are located between the first pressure plate and the second pressure plate. The sapphire plate is located on the side near the first pressure plate. A through hole is provided on the cover plate. The first pressure plate is a transparent material that can transmit ultrafast laser beams. The base is provided with a pressure applying component for applying pressure to the second pressure plate, and the housing is also provided with a pressure sensor for real-time monitoring of the pressure on the second pressure plate.

2. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The housing is provided with a pressure sensor base that slides with the inner wall of the housing. The pressure sensor is located between the second pressure plate and the pressure sensor base and is fixedly connected to the pressure sensor base. The pressure applying component includes a clamping screw that is threaded to the base. One end of the clamping screw located inside the housing contacts the pressure sensor base.

3. The ultrafast laser welding apparatus for sapphire and metal according to claim 2, characterized in that, The end of the clamping screw away from the pressure sensor base is connected to a motor, and both the motor and the pressure sensor are connected to a controller.

4. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The housing is provided with an air inlet and an air outlet.

5. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The housing, the cover plate, and the base are connected by bolts and nuts.

6. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The first pressure plate is made of sapphire, which can transmit light in the range of 300nm-5000nm and has a transmittance of more than 87%.

7. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The thickness of the first pressure plate is 1mm-2mm.

8. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The sapphire substrate has a thickness of 1-5mm and can transmit light in the range of 300nm-5000nm with a transmittance greater than 87%.

9. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The metal sheet includes any one of titanium alloy, copper, or Invar alloy.

10. The ultrafast laser welding apparatus for sapphire and metal according to claim 1, characterized in that, The ultrafast laser unit includes an ultrafast laser, and also includes a beam expander, a reflector, and a focusing galvanometer arranged sequentially along the ultrafast laser beam direction of the ultrafast laser.

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