Femtosecond picosecond composite laser welding method and equipment for heterogeneous materials

Abstract

This invention provides a femtosecond-picosecond hybrid laser welding method and equipment for heterogeneous materials, specifically including: stacking glass and metal on a three-dimensional motion platform and clamping them with fixtures; adjusting the femtosecond laser (pulse width 50-1000 fs, peak power density 10¹²-10¹³ W / cm²) and the picosecond laser (pulse width 1-200 ps, ​​peak power density 10⁸-10⁹ W / cm²) through different beam expansion systems, so that the picosecond laser spot completely surrounds the femtosecond laser spot after focusing; the hybrid laser acts spatiotemporally and synchronously on the welding area, with the femtosecond laser focusing at the interface, exciting plasma to melt the metal and fill the gap, and the picosecond laser forming a wide-area heating field around the femtosecond laser, controlling the severe temperature gradient to a gentle state, and having both preheating and post-heating effects, suppressing cracks, enhancing absorption, and improving welding strength; the hybrid laser welds according to a specified path under the control of the control system, achieving a high-strength connection of glass / metal heterogeneous materials. This becomes a key breakthrough in controlling the temperature gradient, suppressing crack formation, and improving welding strength.

Description

Technical Field

[0001] This invention patent relates to the field of laser micro-nano processing, specifically to a femtosecond picosecond composite laser welding method and equipment for heterogeneous materials. Background Technology

[0002] Glass / metal heterostructure bonding has extensive and critical application requirements in aerospace, precision instruments, optoelectronic packaging, and new energy fields. For example, the connection between transparent cockpits and metal frames in aerospace, the encapsulation of glass lenses and metal bases in optical instruments, and the sealing of glass covers and metal housings in electronic devices all require high-strength, high-airtightness connections between glass and metal to meet requirements for structural stability, functional integration, and adaptability to extreme environments. Traditional glass / metal bonding methods have many limitations: mechanical connections introduce stress concentration, compromising material integrity and making it difficult to achieve high airtightness; adhesive bonding is limited by the temperature and aging resistance of adhesives, making it unsuitable for harsh conditions such as high temperature and high humidity; brazing or diffusion welding requires overall high-temperature heating, which can easily cause the glass to crack due to mismatched thermal expansion coefficients, and it is difficult to achieve precise, localized connections. These drawbacks greatly limit the application expansion of glass / metal heterostructures in high-end manufacturing.

[0003] Laser welding, as a localized heating and high-precision joining technology, has become an important direction for solving the challenges of joining glass / metal dissimilar materials due to its advantages such as high energy density, small heat-affected zone, and strong controllability. In particular, ultrafast lasers can achieve non-thermally fusible or micro-fusible joining of materials, effectively reducing the thermal stress problems in traditional thermal welding and providing new possibilities for joining dissimilar materials. However, in laser welding of glass / metal dissimilar materials, longitudinal and transverse cracks are easily generated inside the transparent, hard, and brittle glass, which is the core bottleneck limiting the weld strength. This stems from the significant differences in the thermophysical properties (coefficient of thermal expansion, thermal conductivity, etc.) between glass and metal. The intense temperature gradient caused by localized high temperatures during welding leads to residual stress concentrated inside the glass during cooling, which, exceeding its fracture strength, triggers cracking. Therefore, controlling the temperature gradient during welding and optimizing the cooling path of the glass have become key strategies for suppressing crack formation and improving weld strength.

[0004] To achieve this goal, this invention proposes a welding method combining femtosecond and picosecond lasers. Both are Gaussian beams. The femtosecond laser, with its ultrashort femtosecond pulse width and high peak power, can achieve precise local energy deposition at the glass-metal interface, triggering material modification and micro-fusion bonding. The picosecond laser, with its relatively long picosecond pulse width and lower peak power, forms an auxiliary heating zone around the femtosecond laser's active area. By constructing a gradient temperature field to control the overall cooling process, crack formation is suppressed, and welding strength is improved. Simultaneously, during the scanning and moving welding process, the picosecond laser also plays a role in preheating by reducing the initial temperature gradient and in slowly releasing residual stress through post-heating, enhancing the glass's absorption efficiency of the laser and improving the stability of the welding process. In practice, two independent beam expanding systems are used to adjust the beam diameter and divergence angle of the femtosecond laser and picosecond laser respectively. After focusing by the same objective lens, the beam spot is matched: the diameter of the femtosecond laser focused beam spot is controlled at 1-10μm to ensure the accuracy of the connection area; the diameter of the picosecond laser focused beam spot is controlled at 1-50μm to form the outer heating range; if a lens is used for focusing, the diameter of the femtosecond laser beam spot is 10-30μm and the diameter of the picosecond laser beam spot is 10-100μm, which can adapt to different welding scale requirements.

[0005] Compared with existing technologies, such as the continuous laser-assisted scheme used in the authorized patent (CN114160975B) and the published patent application (CN114160975A) "Large-format High-intensity Laser Welding Method and Equipment for Dissimilar Materials", this invention has significant advantages: the thermal effect of continuous lasers is too strong, which can cause the metal to melt and expand over a large area during composite welding, while simultaneously heating and melting a large amount of glass material, thus exacerbating joint stress and crack formation. Although it can solve the problem of non-optical contact welding, it cannot effectively control cracks to improve strength. In contrast, the picosecond laser and femtosecond laser selected in this invention belong to the ultrafast laser category and can be applied to transparent glass through nonlinear absorption mechanisms, avoiding the excessive thermal effects of traditional continuous lasers. Compared with femtosecond lasers, picosecond lasers have lower peak power and longer pulse widths, which can control the temperature drop rate and reduce the temperature gradient through continuous energy input without causing severe thermal damage to the material, thereby achieving a breakthrough improvement in suppressing crack formation and improving welding strength.

[0006] The core advantage stems from the fundamental difference in heat injection characteristics between femtosecond continuous-wave lasers and femtosecond picosecond lasers: Femtosecond continuous-wave lasers, due to their continuous power output, have long heat conduction times and large heat diffusion ranges, easily leading to material cracking or performance degradation. Their energy relies on linear absorption, requiring accumulation on the material surface before conduction. Transparent materials are prone to reflection losses, low utilization, and ablation. Continuous energy supply also causes significant heat accumulation, and the interface is more susceptible to heat buildup and stress due to differences in thermal conductivity. In contrast, femtosecond picosecond lasers, with their ultrashort pulse characteristics, release energy in a concentrated manner, completing welding before heat diffusion occurs. The heat-affected zone can be reduced to below 10 micrometers, with near-zero heat impact and preservation of the material's original properties. High peak power enables nonlinear absorption, allowing energy to directly reach the welding interface. This supports internal welding of transparent materials and improves utilization. Furthermore, heat dissipation between material gaps can be achieved by adjusting the pulse interval and energy, resulting in minimal heat accumulation and superior controllability of heat injection. Summary of the Invention

[0007] To address the problem that longitudinal and transverse cracks inside the transparent material greatly limit the welding strength in glass / metal heterogeneous welding, this invention patent provides a femtosecond and picosecond composite laser welding method and equipment for heterogeneous materials. This method can control the temperature gradient during the welding process, optimize the cooling path of the glass, suppress crack formation, and improve welding strength.

[0008] To achieve the above objectives, the present invention provides a femtosecond and picosecond composite laser welding method and equipment for heterogeneous materials, comprising the following steps:

[0009] (1) Place the glass and metal on a three-dimensional motion platform, with the glass on top of the metal and clamped by a fixture;

[0010] (2) The beam diameter and divergence angle of the femtosecond laser and the picosecond laser are adjusted by different beam expansion systems. After focusing by the objective lens or lens, the beam spot is matched. The diameter of the femtosecond laser beam spot is w1 and the diameter of the picosecond laser beam spot is w2. Ensure that w2>>1.5w1, which lays the foundation for subsequent temperature gradient control.

[0011] (3) In the composite laser synchronous scanning welding stage, the femtosecond laser and the picosecond laser act on the welding area in a time-synchronized and spatially coupled manner. The femtosecond laser focuses on the interface, and the ultra-high peak energy is absorbed by the metal, which excites high-temperature and high-density plasma. The plasma continuously absorbs energy and expands freely, driving the interface temperature to rise above the metal melting point, causing the metal to melt locally and fill the gap. Meanwhile, the picosecond laser forms a wide-area heating field around the femtosecond laser action area, which modulates the severe temperature gradient when the femtosecond laser acts alone into a gentle temperature gradient, suppresses crack generation, and improves welding strength.

[0012] (4) When the centers of the picosecond spot w2 and the femtosecond spot w1 coincide, when the scanning moves, the side where w2 is greater than w1 can form a preheating of the interface of the heterogeneous material, reducing the initial temperature gradient, while the other side can form a postheating, slowly releasing residual stress, inhibiting crack formation, and improving welding stability.

[0013] (5) Under the control of the control system, the composite laser can weld along the specified path, which can increase the welding strength of non-optical contact glass / metal heteromaterials from 10-20MPa for femtosecond lasers and 20-30MPa for picosecond lasers to 60-80MPa.

[0014] Furthermore, the three-dimensional motion platform is a motion platform with three degrees of freedom, capable of moving or rotating independently or in conjunction on the X, Y, and Z axes, thereby achieving precise position and orientation adjustment of the workpiece in three-dimensional space.

[0015] Furthermore, the femtosecond laser has a wavelength of 532-1064 nm, a pulse width of 50-1000 fs, a repetition rate of 1 kHz-2 MHz, a power of 1-60 W, a peak power density of 10¹²-10¹³ W / cm², and a pulse energy of 1-100 μJ. The picosecond laser has a wavelength of 532-1064 nm, a pulse width of 1-200 ps, ​​a repetition rate of 1 kHz-2 MHz, a power of 10-60 W, and a peak power density of 10 μJ. 8 -10 9 W / cm², pulse energy up to 10-1000uJ, picosecond lasers have long pulse widths and low peak values ​​to form an outer heating range, while femtosecond lasers have short pulse widths and high peak values ​​to ensure precise connection areas.

[0016] Furthermore, the beam expanding system includes a femtosecond beam expanding system and a picosecond beam expanding system, which respectively adjust the beam diameter and divergence angle of the femtosecond laser and the picosecond laser. Under objective focusing, the femtosecond spot diameter is 1-10μm and the picosecond spot diameter is 1-50μm. Under lens focusing, the femtosecond spot diameter is 10-30μm and the picosecond spot diameter is 10-100μm, adapting to different welding scale requirements.

[0017] Furthermore, the femtosecond laser and picosecond laser are combined through a coaxial optical path, precisely coinciding at the glass-metal interface at the spatial focal point. The timing is controlled and synchronized by an electronic phase-locked loop (PLL) and a piezoelectric ceramic (PZT) feedback system, and the energy ratio is adjusted according to the glass thickness and metal material.

[0018] Furthermore, the non-optical contact refers to a contact condition where the gap between the glass / metal contact surfaces is greater than 1 / 4 of the incident laser wavelength.

[0019] Furthermore, the glass is sapphire, fused silica, ceramic, or silicon, and the metal is Invar, titanium alloy, aluminum alloy, or copper.

[0020] Furthermore, the femtosecond picosecond composite laser welding equipment for heterogeneous materials is characterized by employing the aforementioned femtosecond picosecond composite laser welding method for heterogeneous materials, used to suppress crack formation and improve welding strength in glass / metal heterogeneous welding.

[0021] In summary, compared with the prior art, the technical solutions of the present invention have the following main advantages:

[0022] Precise temperature gradient control significantly suppresses crack formation. Existing technologies mostly employ continuous lasers, whose concentrated and intense thermal effects not only cause large-volume melting and expansion in the metal welding area but also generate significant thermal stress in transparent materials due to overheating. This ultimately leads to a dense network of longitudinal and transverse cracks at the weld joint, severely limiting the improvement of weld strength. This invention employs a composite welding scheme using picosecond lasers assisted by femtosecond lasers. The femtosecond laser achieves precise energy deposition with its ultra-short pulse width, while the picosecond laser, with its longer pulse width and lower peak power, forms a gentle and uniform auxiliary heating zone outside the femtosecond laser's active area. This composite heat source, by controlling the energy ratio and spatial distribution of the two laser beams, constructs a suitable temperature gradient, effectively slowing down the cooling rate of transparent materials after welding, avoiding a sudden increase in local thermal stress, suppressing crack formation at its source, and significantly improving the structural integrity and mechanical strength of the weld joint.

[0023] To avoid excessive thermal damage while balancing energy absorption rate and welding stability, existing continuous laser welding technology, when processing transparent materials, is prone to localized over-melting due to excessively concentrated laser energy. This not only damages the material's microstructure but also reduces welding stability due to the expansion of the thermal damage area. One of the core advantages of this invention lies in utilizing the synergistic effect of picosecond and femtosecond ultrafast lasers: on the one hand, both types of ultrafast lasers can efficiently act on transparent materials through nonlinear absorption effects, solving the problem of low absorption efficiency of traditional lasers on transparent materials; on the other hand, compared to femtosecond lasers, picosecond lasers have lower peak power and longer pulse widths, resulting in a gentler auxiliary heating process that avoids excessive thermal damage to transparent materials due to excessively high instantaneous energy. Simultaneously, picosecond lasers can also play a dual role in preheating and post-heating during the scanning welding process: the preheating stage can improve the absorption efficiency of the transparent material for subsequent femtosecond lasers, while the post-heating stage can further release residual stress in the welding area, significantly improving the overall stability and reliability of the welding process.

[0024] This invention simplifies optical path control and adapts to various welding needs. Existing technologies for non-optical contact welding of dissimilar materials often require complex optical path compensation or frequency locking devices, and are difficult to optimize specifically for crack problems in transparent materials. In this invention, both picosecond and femtosecond lasers use Gaussian beams, and the beam diameter and divergence angle of the two lasers can be flexibly adjusted through different beam expansion systems. In objective lens focusing scenarios, the femtosecond laser spot can be controlled within 1-10μm to ensure processing accuracy, while the picosecond laser spot is matched to 1-50μm to achieve a wide range of auxiliary heating. In lens focusing scenarios, the configuration of 10-30μm femtosecond laser spot and 10-100μm picosecond laser spot can adapt to large-format welding requirements. This adjustable light spot not only simplifies the optical path debugging process, eliminating the need for additional complex frequency locking or optical path offset compensation devices, but also allows for flexible adjustment of light spot parameters based on the thickness, thermal conductivity, and welding precision requirements of different transparent materials. This adapts to various application scenarios such as semiconductor packaging and optical component splicing, significantly improving practicality and adaptability compared to the single parameter configuration of existing technologies. Attached Figure Description

[0025] Figure 1 This is a system diagram of the femtosecond picosecond hybrid laser welding equipment for glass / metal heterostructures according to the present invention.

[0026] Figure 2 This is a schematic diagram illustrating the formation and result of cracks in femtosecond laser heterojunction welding of sapphire / Invar alloy.

[0027] Figure 3 This is a schematic diagram of temperature gradient modulation using a femtosecond and picosecond combined laser.

[0028] Explanation of reference numerals in the attached figures: 1-Femtosecond laser; 2-Picosecond laser; 3-Femtosecond beam expander system; 4-Picosecond beam expander system; 5-Reflecting mirror; 6-Reflection and transmission combination mirror; 7-Collimating optical path; 8-Scanning galvanometer; 9-Objective lens or lens; 10-Three-dimensional motion platform; 11-Glass; 12-Metal. Detailed Implementation

[0029] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. It should be noted that the descriptions of these embodiments are intended to aid in understanding the invention but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0030] This invention addresses the problem that longitudinal and transverse cracks inside transparent materials greatly limit the welding strength in glass / metal heterogeneous welding. It provides a femtosecond and picosecond composite laser welding method and equipment for heterogeneous materials, which can control the temperature gradient during the welding process and optimize the cooling path of the glass, thus becoming a key breakthrough in suppressing crack formation and improving welding strength.

[0031] The structure of an example provided by this invention is as follows: Figure 1 The image shows a device for femtosecond and picosecond composite laser welding of heterogeneous materials. This device consists of a femtosecond laser 1, a picosecond laser 2, a femtosecond beam expander system 3, a picosecond beam expander system 4, a reflecting mirror 5, a reflection-transmission combination mirror 6, a collimating optical path 7, a scanning galvanometer 8, an objective lens or lens 9, a three-dimensional motion platform 10, glass 11, and metal 12.

[0032] Femtosecond lasers have wavelengths of 532-1064 nm, pulse widths of 50-1000 fs, repetition rates of 1 kHz-2 MHz, power of 1-60 W, peak power densities of 10¹²-10¹³ W / cm², and pulse energies of 1-100 μJ. Picosecond lasers have wavelengths of 532-1064 nm, pulse widths of 1-200 ps, ​​repetition rates of 1 kHz-2 MHz, power of 10⁻⁶ W, and peak power densities of 10⁻⁶ W / cm². 8 -10 9 With pulse energies ranging from 10 to 1000 μJ, picosecond lasers offer long pulse widths and low peak values, creating a peripheral heating range. Femtosecond lasers, on the other hand, have short pulse widths and high peak values, ensuring precise connection areas. Picosecond and femtosecond lasers utilize two independent beam-expanding systems to adjust beam diameter and divergence angle. After focusing through the same objective or lens, spot matching is achieved: under objective focusing, the femtosecond spot diameter is 1-10 μm, and the picosecond spot diameter is 1-50 μm; under lens focusing, the femtosecond spot diameter is 10-30 μm, and the picosecond spot diameter is 10-100 μm.

[0033] During operation, glass 11 and metal 12 are stacked on a three-dimensional motion platform 10, with glass 11 positioned above metal 12 and held in place by a clamp. The femtosecond laser emitted by femtosecond laser 1 and the picosecond laser emitted by picosecond laser 2 are adjusted for different beam diameters and divergence angles via femtosecond beam expander system 3 and picosecond beam expander system 4. After being focused by objective lens or lens 9, beam spot matching is achieved, ensuring that the picosecond beam completely envelops the femtosecond beam, laying the foundation for subsequent temperature gradient control. In the composite laser synchronous scanning welding stage, the femtosecond laser and picosecond laser act on the welding area in a time-synchronized and spatially coupled manner. The femtosecond laser is focused on the interface, achieving ultra-high peak energy. Absorbed by the metal, the plasma is excited to reach high temperature and density. The plasma continuously absorbs energy and expands freely, driving the interface temperature above the metal's melting point, causing the metal to melt locally and fill the gaps. Meanwhile, the picosecond laser forms a wide-area heating field around the femtosecond laser's action zone, modulating the severe temperature gradient that occurs when the femtosecond laser acts alone into a gentler temperature gradient. This suppresses crack formation, increases welding strength, and also provides preheating by reducing the initial temperature gradient and slowly releasing residual stress, enhancing laser absorption and improving welding stability. Under the control of the control system, the composite laser completes the high-strength welding of glass / metal dissimilar materials along a designated path.

[0034] Specific examples:

[0035] Example 1:

[0036] This example uses sapphire glass and Invar alloy metal as examples, where the sapphire dimensions are 8mm × 10mm × 2mm and the Invar alloy dimensions are 10mm × 20mm × 2mm. The femtosecond laser wavelength is 1035nm, pulse width is 100fs, repetition rate is set to 1MHz, and power is set to 40W. The picosecond laser wavelength is 1035nm, pulse width is 100ps, repetition rate is set to 1MHz, and power is set to 20W. Laser welding is performed according to the steps in the femtosecond and picosecond composite laser welding method and equipment for heterogeneous materials provided above.

[0037] During operation, sapphire and Invar alloy are stacked on a three-dimensional motion platform, with the sapphire positioned above the Invar alloy and held in place by clamps. Femtosecond and picosecond lasers are adjusted for different beam diameters and divergence angles using different beam expanding systems. After focusing by objectives or lenses, beam spot matching is achieved, ensuring the picosecond spot completely envelops the femtosecond spot, laying the foundation for subsequent temperature gradient control. In the composite laser synchronous scanning welding stage, the femtosecond and picosecond lasers act on the welding area in a time-synchronized and spatially coupled manner. The femtosecond laser is focused at the interface, and its ultra-high peak energy is absorbed by the Invar alloy, exciting high-temperature, high-density plasma. The plasma continuously absorbs energy and expands freely, driving the interface temperature above the melting point of the Invar alloy, causing the Invar alloy to partially melt and fill the gaps. Meanwhile, the picosecond laser forms a wide-area heating field around the femtosecond laser's action zone, modulating the severe temperature gradient that occurs when the femtosecond laser acts alone into a gentler temperature gradient, suppressing crack formation, and improving welding strength. At the same time, it also plays a role in preheating by reducing the initial temperature gradient and slowly releasing residual stress, enhancing laser absorption rate and improving welding stability. Under the control of the control system, the composite laser completes the high-strength welding of sapphire and Invar alloy dissimilar materials according to a specified path.

[0038] Using the method described above, femtosecond and picosecond hybrid lasers were used to weld sapphire and Invar alloy under non-optical contact conditions. The average weld strength was measured to be approximately 60 MPa. Picosecond lasers have long pulse widths and low peak values, forming an outer heating range, while femtosecond lasers have short pulse widths and high peak values, ensuring precise bonding. The gain effect resulting from this specific spatiotemporal matching of femtosecond and picosecond hybrid lasers is far greater than that of dual femtosecond or dual picosecond welding. In contrast, when using femtosecond-continuous laser hybrid lasers to weld sapphire and Invar alloy (with a femtosecond laser wavelength of 1035 nm, a pulse width of 100 fs, a repetition rate of 1 MHz, and a power of 40 W, and a continuous laser wavelength of 1035 nm), the average weld strength was measured to be approximately 20 MPa. Due to the excessive thermal effect of the continuous laser, the Invar alloy expanded significantly, and the sapphire cracked, making it prone to breakage, which greatly limited the improvement of the weld strength of dissimilar materials.

[0039] Example 2:

[0040] This example uses quartz glass as the glass and stainless steel as the metal, with the quartz glass dimensions being 8mm × 10mm × 2mm and the stainless steel dimensions being 10mm × 20mm × 2mm. The femtosecond laser wavelength is 1035nm, the pulse width is 200fs, the repetition rate is set to 2MHz, and the power is set to 40W. The picosecond laser wavelength is 1035nm, the pulse width is 200ps, the repetition rate is set to 2MHz, and the power is set to 20W. Laser welding is performed according to the steps in the femtosecond and picosecond composite laser welding method and equipment for heterogeneous materials provided above.

[0041] During operation, quartz glass and stainless steel are stacked on a three-dimensional motion platform, with the quartz glass positioned above the stainless steel and held in place by clamps. Femtosecond and picosecond lasers are adjusted for different beam diameters and divergence angles using different beam expanding systems. After focusing by objectives or lenses, beam spot matching is achieved, ensuring the picosecond spot completely envelops the femtosecond spot, laying the foundation for subsequent temperature gradient control. In the composite laser synchronous scanning welding stage, the femtosecond and picosecond lasers act on the welding area in a time-synchronized and spatially coupled manner. The femtosecond laser is focused at the interface, and its ultra-high peak energy is absorbed by the stainless steel, exciting high-temperature, high-density plasma. The plasma continuously absorbs energy and expands freely, driving the interface temperature to above the melting point of stainless steel, causing the stainless steel to melt locally and fill the gaps. Meanwhile, the picosecond laser forms a wide-area heating field around the femtosecond laser's action area, modulating the severe temperature gradient that occurs when the femtosecond laser acts alone into a gentler temperature gradient, suppressing crack formation, and improving welding strength. At the same time, it can also play a role in preheating by reducing the initial temperature gradient and slowly releasing residual stress, enhancing laser absorption rate and improving welding stability. Under the control of the control system, the composite laser completes the high-strength welding of quartz glass and stainless steel dissimilar materials according to a specified path.

Claims

1. A femtosecond picosecond hybrid laser welding method for heterogeneous materials, used to suppress crack formation and improve welding strength in glass-metal heterogeneous welding, characterized in that... Includes the following steps: Step 1: Place the glass and metal on a three-dimensional motion platform, with the glass on top of the metal, and hold it with clamps; Step 2: Adjust the beam diameter and divergence angle of the femtosecond laser and picosecond laser using different beam expanding systems. After focusing with an objective lens or lens, achieve spot matching. The femtosecond laser spot diameter is w1, and the picosecond laser spot diameter is w2, ensuring that w2 >> 1.5w1, which lays the foundation for subsequent temperature gradient control. Step 3, the composite laser synchronous scanning welding stage, femtosecond laser and picosecond laser act on the welding area in a time-synchronized and spatially coupled manner. The femtosecond laser is focused on the interface, and the ultra-high peak energy is absorbed by the metal, exciting high-temperature and high-density plasma. The plasma continuously absorbs energy and expands freely, driving the interface temperature to rise above the metal melting point, causing the metal to melt locally and fill the gap. Meanwhile, the picosecond laser forms a wide-area heating field around the femtosecond laser action area, modulating the severe temperature gradient when the femtosecond laser acts alone into a gentle temperature gradient, suppressing crack formation and improving welding strength. Step 4: When w2 and w1 coincide, as the scan moves, the side where w2 is greater than w1 forms a preheating effect on the interface of the heterogeneous materials, reducing the initial temperature gradient, while the other side forms a postheating effect, slowly releasing residual stress, inhibiting crack formation, and improving welding stability. Step 5: Under the control of the control system, the composite laser welds along the specified path, which can increase the welding strength of non-optical contact glass-metal heterostructures from 10-20MPa for femtosecond lasers and 20-30MPa for picosecond lasers to 60-80MPa. The beam expanding system includes a femtosecond beam expanding system and a picosecond beam expanding system, which respectively adjust the beam diameter and divergence angle of the femtosecond laser and the picosecond laser. Under objective focusing, the femtosecond laser spot diameter is 1-10μm and the picosecond laser spot diameter is 1-50μm. Under lens focusing, the femtosecond laser spot diameter is 10-30μm and the picosecond laser spot diameter is 10-100μm, adapting to different welding scale requirements.

2. The femtosecond and picosecond composite laser welding method for heterogeneous materials according to claim 1, characterized in that, The three-dimensional motion platform is a motion platform with three degrees of freedom, capable of moving or rotating independently or in conjunction on the X, Y, and Z axes, to achieve precise position and posture adjustment of the workpiece in three-dimensional space.

3. The femtosecond and picosecond hybrid laser welding method for heterogeneous materials according to claim 1, characterized in that, The femtosecond laser has a wavelength of 532-1064 nm, a pulse width of 50-1000 fs, a repetition rate of 1 kHz-2 MHz, a power of 1-60 W, a peak power density of 10¹²-10¹³ W / cm², and a pulse energy of 1-100 μJ. The picosecond laser has a wavelength of 532-1064 nm, a pulse width of 1-200 ps, ​​a repetition rate of 1 kHz-2 MHz, a power of 10-60 W, and a peak power density of 10 μJ. 8 -10 9 W / cm², pulse energy up to 10-1000uJ, picosecond lasers have long pulse widths and low peak values ​​to form an outer heating range, while femtosecond lasers have short pulse widths and high peak values ​​to ensure precise connection areas.

4. The femtosecond and picosecond hybrid laser welding method for heterogeneous materials according to claim 1, characterized in that, The femtosecond laser and picosecond laser are combined through a coaxial optical path and precisely coincide at the glass-metal interface at the spatial focal point. The time synchronization is controlled by an electronic phase-locked loop (PLL) and a piezoelectric ceramic (PZT) feedback system, and the energy ratio is adjusted according to the glass thickness and metal material.

5. The femtosecond and picosecond hybrid laser welding method for heterogeneous materials according to claim 1, characterized in that, The non-optical contact refers to a contact condition where the gap between the glass-metal contact surfaces is greater than 1 / 4 of the incident laser wavelength.

6. The femtosecond and picosecond composite laser welding method for heterogeneous materials according to claim 1, characterized in that, The glass is fused silica, and the metal is Invar, titanium alloy, aluminum alloy, or copper.

7. A femtosecond and picosecond hybrid laser welding device for heterogeneous materials, characterized in that, The femtosecond picosecond composite laser welding method for heterogeneous materials described in claim 1 is used to suppress crack formation and improve welding strength in glass-metal heterogeneous welding.

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