A high-efficiency welding method for curved / inclined transparent materials

Abstract

The present invention provides a high-efficiency welding method for curved / slanted transparent materials, which specifically includes: stacking curved or slanted transparent materials and clamping them with a clamp; outputting an ultrafast laser in a MHz-level high-repetition-rate pulse train mode through the Burst mode of the laser, focusing on a specific position through a focusing mirror and generating a nonlinear optical effect therewith, the laser energy in the focused area is absorbed by the material, resulting in local electron excitation and ionization, forming a high-temperature and high-density plasma; the lower material in the high-temperature area undergoes an electron-ion recombination process, melting and recrystallization occurs, and the upper material is melted by heat conduction heating to achieve efficient mutual fusion and connection; the laser is controlled by a galvanometer to weld along a specified path to form a stable connection interface. The present invention realizes efficient heat accumulation through a long-focal-length galvanometer combined with the Burst mode of the laser, and realizes a molten teardrop structure with a depth of not less than 5 mm, which is efficient and simple and realizes high-quality, high-strength, and high-efficiency welding.

Description

Technical Field

[0001] The invention patent relates to the field of laser processing, and specifically to a high-efficiency welding method for curved / inclined transparent materials. Background Art

[0002] With the rapid development of laser technology, the global laser industry is also developing rapidly. The laser industry in many developed countries is booming, representing the highest level of development in the world's laser industry; China insists that innovation is the primary productive force, and the development of the laser industry is steady and progressive, gradually becoming an important driving force for new quality productivity. Laser technology has begun to penetrate all aspects of life, and the world has begun to enter the era of "light processing". Ultrafast laser processing is an advanced manufacturing technology with high precision and low thermal impact, which uses extremely short pulse lasers to process materials. Compared with traditional lasers, it has a very short pulse time, almost no thermal effect, and can achieve micron-level precision. It is widely used in the fields of microelectronics, medicine and materials science, and is used to manufacture tiny circuits, perform ophthalmic surgery and improve the surface properties of materials. Ultrafast laser processing has attracted great attention in the manufacturing industry due to its high precision and low thermal effect, and provides a revolutionary solution for micro-nano processing and precision manufacturing.

[0003] Transparent materials such as quartz glass, sapphire, organic polymers and various crystal structures are widely used in aerospace, chip packaging, optoelectronic packaging and medical fields due to their excellent physical and chemical properties. However, their typical high hardness and brittleness will lead to brittle fracture due to thermal expansion, making it difficult to form reliable welding joints. Ultrafast lasers are ideal heat sources for welding transparent materials because of their small thermal effect and nonlinear absorption. In recent years, the rapid development of ultrafast laser welding technology has made high-strength welding of planar transparent materials and planar transparent-metal dissimilar materials possible. The nonlinear absorption of transparent materials is stimulated by local energy injection, thereby achieving heating and melting of transparent materials.

[0004] In this regard, ultrafast lasers require a higher peak power density to form nonlinear absorption inside transparent materials, which needs to be achieved through a lens with a high numerical aperture. In this case, the smaller the focused spot, the smaller the Rayleigh length (i.e., depth of focus) formed by laser focusing. In actual welding, there are strict requirements on the flatness of the sample surface. Therefore, ultrafast laser welding technology is currently mainly used in the welding of planar transparent materials. In response to actual application requirements, the sample may be in a curved or inclined state. For example, in the packaging of deep ultraviolet LEDs, the window pieces are mostly curved transparent materials. In actual ultrafast laser welding, the focus of the laser will change with the position of the curved surface, making it difficult to complete high-strength and high-airtightness welding applications. The current common welding method is multiple scanning welding with a variable focus, that is, the focus spot position is adjusted once for each different curved surface position, so that the laser focus can be maintained on the welding interface. The patent (CN107914084A) that has been applied for publication obtains point cloud data by scanning the curved thin plate, processes the coordinate data to fit the welding curve, and controls the laser to weld the curved thin plate along the welding curve. Under this technical solution, the control system has high precision requirements, is complex, and the multiple focus adjustments also limit the welding efficiency. Therefore, it is urgent to develop a new welding method to achieve high-efficiency welding of curved / inclined transparent materials.

[0005] The present invention provides a high-efficiency welding method for curved / slanted transparent materials. An ultrafast laser is focused on a specific position of a transparent material through a focusing mirror and acts thereon. The material in the focused area absorbs photon energy and ionizes, and a high-temperature and high-density plasma is formed in an ultra-short time and gathers on the surface of the material. The lower material in the high-temperature area undergoes an electron-ion recombination process, which promotes the occurrence of melting and recrystallization, thereby realizing the mutual fusion and connection of the two interfaces of the upper material and the lower material. The long-focal-length galvanometer combined with the Burst mode output by the laser realizes efficient heat accumulation, and a molten teardrop structure with a depth of not less than 5 mm can be formed during the welding process. The molten teardrop structure has an extremely high depth range, which can keep the laser focus always on the changing curved surface position, which is crucial to ensuring the strength and stability of the weld, while minimizing thermal stress and material damage. The Burst mode pulse train of the ultrafast laser can directly realize the direct welding of curved transparent materials under the scanning of a two-dimensional galvanometer, without the need to use a variable focus method, which not only effectively improves the efficiency and quality of welding, but also shows its unique advantages in controlling the laser processing of complex optical materials. Summary of the invention

[0006] In view of the above problems, the present invention provides a high-efficiency welding method for curved / slanted transparent materials. The ultrafast laser is focused on a specific position of the transparent material through a focusing mirror and acts on it. The material in the focusing area absorbs photon energy and ionizes, forming a high-temperature and high-density plasma in an ultra-short time and gathering on the surface of the material. In these high-temperature areas, the lower curved transparent material undergoes an electron-ion recombination process, which promotes the occurrence of melting and recrystallization, thereby realizing the mutual fusion and connection of the upper curved transparent material and the lower curved transparent material. The long focal length galvanometer combined with the Burst mode output by the laser realizes efficient heat accumulation, and a molten teardrop structure with a depth of not less than 5mm can be formed during the welding process. The molten teardrop structure has an extremely high depth range, which can keep the laser focus always on the changing curved surface position, which is crucial to ensuring the strength and stability of the weld, while minimizing thermal stress and material damage. The Burst mode pulse train of the ultrafast laser can directly realize the direct welding of curved transparent materials under the scanning of the two-dimensional galvanometer, without the need to use a variable focus method, which not only effectively improves the efficiency and quality of welding, but also shows its unique advantages in controlling the laser processing of complex optical materials.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a high-efficiency welding method for curved / inclined transparent materials, comprising the following steps:

[0008] (1) stacking a curved transparent material with a curved transparent material or a sloped transparent material with a sloped transparent material, and clamping them with a clamp;

[0009] (2) Through the Burst mode of the ultrafast laser, an ultrafast laser in a pulse train mode with a high repetition rate at the MHz level is output. A long focal length focusing mirror with a focal length of not less than 50 mm is used to obtain a focusing result with a large Rayleigh length, so that the laser is focused on a specific position of the transparent material and acts on it. The transparent material undergoes nonlinear optical effects under the action of the ultrafast pulse. The laser energy in the focused area is absorbed by the transparent material, resulting in the excitation and ionization of local electrons, forming a high-temperature and high-density plasma. This rapidly formed plasma can not only heat the surface of the transparent material in a very short time, but also cause changes in the structure of the transparent material.

[0010] (3) In these high-temperature regions, the lower material undergoes an electron-ion recombination process, which promotes melting and recrystallization, forming a molten teardrop structure with a depth of not less than 5 mm. The molten teardrop structure is a unique high-depth molten structure that is ultra-fast achieved in transparent materials by a long-focal-length galvanometer combined with a Burst mode, and can subsequently heat and melt the upper material through heat conduction, thereby achieving efficient mutual fusion and connection of the two transparent materials.

[0011] (4) The ultrafast laser is controlled by a high-speed two-dimensional galvanometer to move in two dimensions, so that it can be welded on a curved or inclined surface along a specified path, ultimately forming a stable connection interface.

[0012] Furthermore, the ultrafast laser is a picosecond laser or a femtosecond laser, with a wavelength in the range of 266-2000nm, a repetition frequency of 1MHz, a Burst internal pulse interval in the range of 20-210ns, and a sub-pulse number of 1-10.

[0013] Furthermore, the Burst mode is a pulse train mode, that is, several sub-pulses are taken as a group, a sub-pulse sequence is output in each cycle, and the output is in the form of a pulse train in the entire time domain. The number of sub-pulses in the pulse train is set according to the material difference, which can change the energy distribution and time characteristics of the ultrafast laser.

[0014] Furthermore, the specific position of the transparent material is 0 μm-100 μm below the upper surface of the lower sample when welding transparent / transparent homogeneous materials.

[0015] Furthermore, the upper material is a curved surface transparent material or an inclined surface transparent material, and the lower material is the same kind of curved surface transparent material or inclined surface transparent material.

[0016] Furthermore, the high-speed two-dimensional galvanometer realizes two-dimensional movement of the light beam through the deflection and control of two reflection mirrors.

[0017] Furthermore, the transparent material is sapphire or fused quartz or ceramic or silicon, and the material is polished.

[0018] Furthermore, the transparent material is sapphire or fused quartz or ceramic or silicon, and the material is not polished.

[0019] Furthermore, a high-efficiency welding method for curved / slanted transparent materials includes a laser, a collimating mirror, a galvanometer and a focusing mirror, and is characterized in that it also includes an optical component for adjusting the optical path of the laser emitted by the laser to be perpendicular to the surface of the workpiece to be processed, a clamp for clamping the stacked samples, and a motion platform for driving the clamp to move, wherein the clamp can adjust the gap between the upper material sample and the lower material sample.

[0020] In general, the above technical solution of the present invention has the following advantages compared with the prior art:

[0021] This invention patent innovatively solves multiple challenges in traditional welding methods, especially when dealing with the welding of curved transparent materials and beveled transparent materials. For curved transparent materials or beveled transparent materials in actual needs, the focus of the laser in ultrafast laser welding will change with the position of the curved surface, making it difficult to complete high-strength, high-airtightness welding applications. Traditional methods rely on multiple adjustments of the focus and multiple scanning welding of the variable focus, which requires a high-precision control system and complex operating procedures, which greatly limits the welding efficiency and welding quality. In contrast, the patent of this invention uses a long-focal-length galvanometer to achieve a long-focal-depth focusing state, combined with the laser's Burst mode for efficient heat accumulation, and successfully achieves a molten teardrop structure with a depth of not less than 5mm.

[0022] Specifically, this technology has shown significant advantages in the processing of complex optical materials. The long focal length focusing mirror achieves focusing results with a larger spot and a larger Rayleigh length through low NA focusing conditions, so that the laser focus can be stably maintained at the changing position of curved and inclined surfaces, without the need to frequently adjust the focus position, reducing the requirements for the flatness of the sample material in actual welding, greatly simplifying the operation process and improving welding efficiency. At the same time, the laser's Burst mode pulse train consists of a series of high-energy pulses with a short time interval between each pulse. This sequence helps to enhance the energy transfer to the material surface and effectively control the heat-affected zone, thereby achieving efficient heat accumulation, which is particularly conducive to the formation of a molten teardrop structure with a wide range of depths. This structure not only ensures the strength and stability of the weld, but also minimizes thermal stress and material damage, improving welding quality and material service life.

[0023] In addition, the application field of the present invention is wide and practical. The extremely deep teardrop-shaped molten structure achieved by the patent, in addition to the direct welding of curved transparent materials and beveled transparent materials, can also be applied to the processing of other flat materials such as deep ultraviolet LED window mirrors, as well as the application scenarios of window mirror format expansion. This versatility and applicability make this technology have important commercial and scientific value in the fields of industrial manufacturing and high-precision optical equipment, bringing new solutions and development opportunities to the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a system diagram of the high-efficiency welding equipment for curved / inclined transparent materials of the present invention.

[0025] Figure 2 It is a high-depth melting structure (no less than 5mm in depth) achieved ultra-fast by combining a long focal length galvanometer with the Burst mode.

[0026] Figure 3 It is a schematic diagram of welding between curved transparent materials and other materials, and between inclined transparent materials and inclined transparent materials.

[0027] Explanation of the reference numerals: 1 - ultrafast laser; 2 - collimating mirror; 3 - galvanometer; 4 - focusing mirror; 5 - laser focus; 6 - curved surface to be welded 1; 7 - curved surface to be welded 2. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] The present invention provides a high-efficiency welding method for curved / slanted transparent materials, aiming at the problems that the variable focus multiple scanning welding method for curved / slanted transparent materials has the control system requirements of high precision, the control system is complex, and the welding efficiency is greatly reduced by multiple focus adjustments.

[0030] The structure of an example provided by the present invention is as follows Figure 1 As shown, it is a device for high-efficiency welding of curved / inclined transparent materials. The device is composed of an ultrafast laser 1, a collimating mirror 2, a galvanometer 3, a focusing mirror 4 and a workbench.

[0031] In this example, the ultrafast laser 1, the collimating mirror 2, the galvanometer 3 and the focusing mirror 4 are located on the same optical path, and the optical path enters the galvanometer 3 after being collimated by the collimating mirror 2. The galvanometer 3 controls the two-dimensional movement of the optical path so that the optical path enters the focusing mirror 4 vertically. The focusing mirror 4 is located above the workbench.

[0032] The laser light emitted by the ultrafast laser is usually a picosecond laser or a femtosecond laser. The wavelength range of the output light beam of the ultrafast laser 1 is 266-2000nm.

[0033] When working, the ultrafast laser 1 outputs a femtosecond laser in a pulse train mode with a high repetition rate at the MHz level through its own Burst mode, in which the number of sub-pulses in the pulse train can be set according to the material difference; the femtosecond laser first passes through the collimator 2 to collimate the laser beam, which is convenient for laser spatial transmission; then passes through the high-speed two-dimensional galvanometer 3, and realizes the two-dimensional movement of the laser beam through the deflection and control of the two reflectors; then the laser beam is focused through the focusing mirror 4, which is a long-focal-length focusing mirror (focal length not less than 50mm) in this patent, the purpose is to achieve a focusing result of a larger spot and a larger Rayleigh length through low numerical aperture focusing conditions; the laser beam finally acts on a specific position, and the specific position for transparent / transparent homogeneous material welding is 0μm-100μm below the upper surface of the lower sample. The ultrafast laser is focused to a specific position of the curved surface to be welded 7 through the focusing mirror 4, and the high energy density area caused by these pulse trains will cause the curved surface to be welded 7 to be rapidly absorbed and ionized, thereby forming a local high-temperature area in a short time. In these high-temperature areas, the curved surface to be welded 7 undergoes an electron-ion recombination process, which promotes the occurrence of melting and recrystallization, thereby achieving efficient mutual fusion and connection between the curved surface to be welded 6 and the curved surface to be welded 7. The long focal length galvanometer combined with the Burst mode of the laser output achieves efficient heat accumulation, and a molten teardrop structure with a depth of not less than 5mm can be formed during the welding process. Because the molten teardrop structure has an extremely high depth range, it can keep the laser focus always on the changing curved surface position, so it can directly achieve direct welding of curved transparent materials under the scanning of the two-dimensional galvanometer without the need for a variable focus method.

[0034] Specific examples:

[0035] Example 1: This example takes the upper material 6 as curved quartz glass and the lower material 7 as curved quartz glass as an example. The size of the curved quartz glass is selected to be 20 mm × 2 mm in diameter, the impurity content of the sample is 5 ppm, and the quartz glass is polished on all four sides. Laser welding is performed according to the steps in the high-efficiency welding method for curved / beveled transparent materials provided in the above example.

[0036] In the step of welding the curved transparent material with the curved transparent material, the ultrafast laser 1 is collimated by the collimator 2, the two-dimensional movement of the light beam is controlled by the galvanometer 3, and the ultrafast laser 1 is focused on a specific position by the long focal length focusing mirror 4, and the specific position is 15 μm below the upper surface of the curved surface to be welded 7. The output wavelength of the ultrafast laser is set to 1033 nm, the repetition frequency is 1 MHz, the pulse width is 40 ns, and the number of sub-pulses is 2. The control system controls the laser and the workbench to weld according to the set welding route. The high-energy laser beam with a pulse energy of 24.2 μJ is focused to a specific position of the curved surface to be welded 7 through the focusing mirror 4. The high energy density areas caused by these pulse trains will cause the rapid absorption and ionization of the curved surface to be welded 7, and then form a local high temperature area in a short time. In these high temperature areas, the curved surface to be welded 7 undergoes an electron-ion recombination process, which promotes the occurrence of melting and recrystallization, and forms a molten teardrop structure with a depth of not less than 5 mm, thereby realizing the efficient mutual fusion and connection of the two surfaces of the curved surface to be welded 6 and the curved surface to be welded 7.

[0037] Example 2: This example takes the upper material 6 as beveled quartz glass and the lower material 7 as beveled quartz glass as an example. The size of the quartz glass is selected to be 40mm×40mm×5mm, and the impurity content of the sample is 5ppm. The quartz glass is polished on all four sides and divided into two parts along a 45° direction. Laser welding is performed according to the steps in the high-efficiency welding method for curved / beveled transparent materials provided in the above example.

[0038] In the step of welding the bevel transparent material to the bevel transparent material, the ultrafast laser 1 is collimated by the collimator 2, the two-dimensional movement of the light beam is controlled by the galvanometer 3, and the long focal length focusing mirror 4 is focused on a specific position, which is 15 μm below the upper surface of the bevel surface to be welded 7. The output wavelength of the ultrafast laser is set to 1033 nm, the repetition frequency is 1 MHz, the pulse width is 80 ns, the number of sub-pulses is 4, and the control system controls the laser and the workbench to weld according to the set welding route. The high-energy laser beam with a pulse energy of 24.2 μJ is focused to a specific position of the bevel surface to be welded 7 through the focusing mirror 4. The high energy density area caused by these pulse trains will cause the bevel surface to be welded 7 to be rapidly absorbed and ionized, and then form a local high temperature area in a short time. In these high temperature areas, the bevel surface to be welded 7 undergoes an electron-ion recombination process, which promotes the occurrence of melting and recrystallization, and forms a molten teardrop structure with a depth of not less than 5 mm, thereby realizing the efficient mutual fusion and connection of the two surfaces of the bevel surface to be welded 6 and the bevel surface to be welded 7.

Claims

1. A high-efficiency welding method for curved / inclined transparent materials, characterized in that: include: Step 1: stacking curved transparent materials and curved transparent materials or inclined transparent materials and inclined transparent materials, and clamping them with a clamp; Step 2: Output MHz-class high-repetition-rate pulse train mode ultrafast laser through the Burst mode of the ultrafast laser, and use a long-focal-length focusing mirror with a focal length of not less than 50 mm to obtain a focusing result with a large Rayleigh length, so that the laser is focused on a specific position of the transparent material and acts on it. The transparent material undergoes nonlinear optical effects under the action of the ultrafast pulse, and the laser energy in the focused area is absorbed by the transparent material, resulting in the excitation and ionization of local electrons, forming a high-temperature and high-density plasma. This rapidly formed plasma can not only heat the surface of the transparent material in a very short time, but also cause changes in the structure of the transparent material; Step 3: In these high-temperature regions, the lower material undergoes an electron-ion recombination process, which promotes melting and recrystallization, forming a molten teardrop structure with a depth of not less than 5 mm. The molten teardrop structure is a unique high-depth molten structure that is ultra-fast achieved in transparent materials by a long-focal-length galvanometer combined with a Burst mode, and can subsequently heat and melt the upper material through heat conduction, thereby achieving efficient mutual fusion and connection of the two transparent materials. Step 4: Use a high-speed two-dimensional galvanometer to control the ultrafast laser to move in two dimensions, so that it can be welded on the curved or inclined surface along a specified path, ultimately forming a stable connection interface.

2. The high-efficiency welding method for curved / inclined transparent materials according to claim 1, characterized in that: In step 2, the ultrafast laser is a picosecond laser or a femtosecond laser, with a wavelength in the range of 266-2000nm, a repetition frequency of 1MHz, a Burst internal pulse interval in the range of 20-210ns, and a sub-pulse number of 1-10.

3. The high-efficiency welding method for curved / inclined transparent materials according to claim 1, characterized in that: In step 2, the Burst mode is a pulse train mode, that is, several sub-pulses are taken as a group, a sub-pulse sequence is output in each cycle, and the output is in the form of a pulse train in the entire time domain. The number of sub-pulses in the pulse train is set according to the material difference, which can change the energy distribution and time characteristics of the ultrafast laser.

4. The high-efficiency welding method for curved / inclined transparent materials according to claim 1, characterized in that: In step 2, the specific position of the transparent material is 0 μm-100 μm below the upper surface of the lower sample when welding transparent / transparent homogeneous materials.

5. The high-efficiency welding method for curved / inclined transparent materials according to claim 1, characterized in that: In step three, the upper material is a curved surface transparent material or an inclined surface transparent material, and the lower material is the same kind of curved surface transparent material or inclined surface transparent material.

6. The high-efficiency welding method for curved / inclined transparent materials according to claim 1, characterized in that: In step 4, the high-speed two-dimensional galvanometer realizes two-dimensional movement of the light beam by deflecting and controlling two reflective mirrors.

7. The high-efficiency welding method for curved / inclined transparent materials according to claim 1, characterized in that: The transparent material is sapphire or fused quartz or ceramic or silicon, and the material is polished.

8. The high-efficiency welding method for curved / inclined transparent materials according to claim 1, characterized in that: The transparent material is sapphire or fused quartz or ceramic or silicon, and the material is not polished.

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