Laser dynamic oscillation high-precision welding method and welding system for transparent material

Abstract

The invention discloses a laser dynamic oscillation high-precision welding method for transparent materials. The laser dynamic oscillation high-precision welding method comprises the following steps: 1) performing small-range high-speed oscillation scanning on tightly focused ultrafast laser by adopting a high-speed scanning device; (2) the moving platform drives the sample to be welded, so that the laser performs direct writing welding on the surface of the sample according to a preset track; and (3) relevant welding parameters such as the oscillation scanning path, the scanning speed and the platform direct writing speed are optimized and adjusted, and high-strength and high-quality ultrafast laser sealing welding is achieved. The laser dynamic oscillation high-precision welding system for the transparent material is a device for implementing the welding method. The invention provides a composite scanning strategy combining small focal spot high-speed scanning and motion platform direct writing, while the motion platform realizes predetermined track welding, the tight focusing laser focal spot keeps continuous high-speed oscillation, and the method has the advantages of high welding efficiency, high welding sealing performance and high welding precision, and is suitable for high-precision micro-area welding of transparent materials.

Description

Technical Field

[0001] The invention belongs to laser welding, and relates to a laser dynamic oscillation high-precision welding method and a welding system for transparent materials. Background Art

[0002] After ultrafast laser focusing, the peak power density is extremely high. Through nonlinear multiphoton absorption, high-precision energy deposition can be achieved inside transparent media. When the ultrafast laser is focused near the contact surface of two pieces of glass, the local high temperature generated by photoionization causes the material near the focus area to melt and solidify quickly, thereby welding the materials together. However, when using ultrafast lasers to weld transparent materials, there are usually two welding schemes: the first is that the laser beam remains fixed, and the moving platform drives the material for welding. This method can use a high numerical aperture objective lens for focusing, which has high welding accuracy, but the spot focused by the objective lens is small, resulting in a small welding pool, making it difficult to achieve continuous and stable focusing throughout the welding process. At the same time, the platform movement speed is slow, which limits the improvement of welding efficiency. Another solution is to use a galvanometer to drive the laser for high-speed scanning. After focusing with a long focal length field lens, its welding speed is dozens or even hundreds of times that of the moving platform. However, the focusing spot of the long focal length field lens is large, the focal depth is also long, and the welding accuracy is limited.

[0003] Since Tamaki et al. first used a low repetition rate (1kHz) femtosecond laser to successfully weld two quartz glass plates in 2005 (JJAP, 2005, 44 (20-23): L687-L689.), in recent years, more and more researchers have used microscope objective focusing for line welding and spot welding, and achieved good results (1. Appl. Phys. A, 2015, 121: 1-9; 2. JLMN, 2018, 13 (1): 0005; 3. CIRP Annals-Manufacturing Technology, 2022, 71 (1): 157-160). This method has high welding accuracy, but the welding is driven by the movement of the stage and the speed is slow. In 2019, several scholars used galvanometers and F-theta lenses instead of microscope objective lenses and displacement platforms for focus scanning, which greatly improved the scanning speed (1. AO, 2019, 58(32): 8858-8864.; 2. OL, 2019, 44(10): 2570-2573; 3. OE, 2019, 27(21): 30297-30307). For example, French researchers used galvanometers instead of microscope objective lenses for welding, achieving a welding speed of 1000 mm / s (AO, 2019, 58(32): 8858-8864). However, although the scanning speed has been greatly improved, the welding accuracy has been affected, especially when welding micro devices, its limitations are particularly obvious.

[0004] In summary, although the existing ultrafast laser welding technology has made some progress, there is still a contradiction between welding accuracy and welding speed. Therefore, it is necessary to develop a new welding method that can maintain high welding accuracy and achieve a fast and efficient welding process. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention proposes a laser dynamic oscillation high-precision welding method and welding system for transparent materials, so that the tightly focused laser oscillates and scans at a high speed while the moving platform drives the sample to be welded to move along a predetermined trajectory. Through a dynamic oscillation scanning strategy that combines galvanometer high-speed scanning and platform movement, a galvanometer scanning system and an optical 4f system are introduced while the moving platform is directly writing and welding. The galvanometer scanning system is used to make the laser focal spot oscillate at a high speed, and the optical 4f system is used to convert the optical path so that the light spot can be kept within the range of the objective lens entrance pupil under scanning. The use of a dynamic oscillation scanning strategy can greatly improve the size of the welding molten pool, welding efficiency and welding quality. In actual welding, the scanning parameters such as the oscillation scanning path, platform movement speed, and oscillation scanning amplitude can be optimized and adjusted according to different weld shapes and widths to achieve high-intensity and high-quality ultrafast laser sealing welding.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] On the one hand, the present invention provides a laser dynamic oscillation high-precision welding method and welding system for transparent materials, which are characterized in that they include the following steps:

[0008] S1. stacking a first sample and a second sample on a two-dimensional motion platform, wherein at least one sample is a transparent material;

[0009] S2. Adjust the two-dimensional motion platform so that the ultrafast laser beam is focused on the interface between the first sample and the second sample to be welded;

[0010] S3. Turn on the high-speed scanning device, load the preset scanning path, and use a tightly focused ultrafast laser to perform high-speed oscillation scanning within the scanning path;

[0011] S4. Load the preset motion trajectory of the two-dimensional motion platform, and synchronously control the two-dimensional motion platform so that while the laser beam is performing high-speed oscillation scanning, the two-dimensional motion platform drives the material to be welded to perform mobile welding according to the preset motion trajectory.

[0012] Furthermore, the diameter of the laser focus spot is 0.5-10μm. The smaller the focus spot diameter, the higher the welding accuracy. The maximum amplitude of the oscillation scan depends on the field of view of the focusing objective lens, which is 5-100 times the diameter of the laser focus spot. The maximum width of a single weld depends on the oscillation scan amplitude, and the width of a single weld is between 0-100μm. The focus spot oscillation scan speed is 10-10^4 times the platform direct writing speed. Increasing the oscillation scan speed is conducive to improving welding efficiency.

[0013] Furthermore, the scanning path is a single circular path, a rectangular path, a concentric circular path, a parallel path, a vertical path, a cross path, or a complex path formed by a combination of multiple simple paths; the platform motion trajectory is an actual weld trajectory, and while the galvanometer is scanning, the platform moves linearly according to the weld range required by the device to be welded; the platform motion speed matches the scanning speed, and if the platform motion speed is too high, blank areas will appear in the scanning, and if the platform motion speed is too low, repeated scanning of local areas will occur, and excessive accumulation of laser energy will damage the material. The platform motion speed needs to be controlled so that the weld area is just completely scanned and covered.

[0014] Furthermore, the scanning path is realized by high-speed vibration of the galvanometer. The platform movement speed matches the scanning speed. If the platform movement speed is too high, blank areas will appear in the scanning. If the platform movement speed is too low, repeated scanning of local areas will occur. Excessive accumulation of laser energy will damage the material. The platform movement speed needs to be controlled so that the entire weld area is scanned and covered.

[0015] Furthermore, the high-speed oscillation scanning can be performed in an XY plane parallel to the sample surface, or simultaneously in three dimensions of XYZ; and the oscillation scanning welding path is optimized and selected according to actual welding requirements.

[0016] Furthermore, the transparent material includes transparent plastic, glass, gemstone, diamond, ceramic, and crystal; the other sample is a transparent material or a non-transparent material, and the non-transparent material includes plastic, semiconductor, metal, and ceramic.

[0017] Furthermore, the ultrafast laser is a picosecond or femtosecond laser with a power of 1-100W and a repetition frequency of 50-5000kHz.

[0018] On the other hand, the present invention also provides a welding system for implementing the above-mentioned laser dynamic oscillation high-precision welding method for transparent materials, which is characterized in that it includes:

[0019] Lasers, used to emit ultrafast laser pulses;

[0020] A beam expander and collimator lens, used for expanding and collimating the laser beam;

[0021] A power regulation system for regulating the power of the laser beam;

[0022] A tightly focused high-speed scanning system is used to tightly focus the laser beam and achieve high-speed oscillation scanning, and at least includes a galvanometer, a lens, and a reflector to adjust the optical path;

[0023] The optical 4f system is used to convert the optical path so that the light spot can be kept within the entrance pupil of the objective lens during scanning.

[0024] Microscopic imaging system, used to achieve coaxial real-time observation;

[0025] A two-dimensional motion platform is used to drive the sample to be welded to move along a predetermined trajectory;

[0026] Among them, the device realizes a dynamic oscillation scanning strategy by combining the galvanometer high-speed scanning and the platform movement. While the moving platform is directly writing welding, the laser focus spot is oscillated and scanned at high speed under the control of the tightly focused high-speed scanning system to improve the size of the welding pool, welding efficiency and welding quality.

[0027] Furthermore, the microscopic imaging system includes a CMOS camera, a tube lens and an objective lens.

[0028] Furthermore, the high-speed scanning system includes a high-speed scanning galvanometer, a high-speed scanning rotating mirror and a high-speed acousto-optic scanning device.

[0029] Compared with the prior art, the present invention proposes a dynamic oscillation scanning welding strategy combining high-speed scanning of the galvanometer and slow movement of the motion platform, and its beneficial effects are as follows:

[0030] 1. On the basis of keeping the objective lens tightly focused and high precision welding, the welding efficiency can be improved by several orders of magnitude through dynamic oscillation scanning;

[0031] 2. It can effectively expand the volume of the molten pool, alleviate the stress concentration caused by the excessively high focus temperature, and improve the sealing effect of transparent materials with large gaps. By expanding the volume of the molten pool, it can also reduce the difficulty of aligning the focus;

[0032] 3. The oscillation creates the effect of stirring the molten pool, further reducing stress accumulation, avoiding the generation of microcracks, and significantly improving welding quality;

[0033] 4. The tightly focused spot has the advantages of small spot and high welding precision, which can reach the micron level. At the same time, by controlling the oscillation range, the width of the welding area can be controlled, which can be as small as several microns, which is suitable for high-precision micro-area welding of transparent materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1This is a diagram of an embodiment of a laser dynamic oscillation high-precision welding device for transparent materials of the present invention, in which: 1. ultrafast laser; 2. half-wave plate; 3. polarization beam splitter cube; 4. CMOS camera; 5. microscope objective lens; 6. optical 4f system; 7. galvanometer; 8. two-dimensional motion platform.

[0035] Figure 2 This is a diagram of an embodiment of the laser dynamic oscillation high-precision welding scanning path of a transparent material used in the present invention, in which: (a) a single circular oscillation scanning path; (b) a rectangular oscillation scanning path; (c) a concentric circular oscillation scanning path; (d) a parallel oscillation scanning path; (e) a vertical oscillation scanning path; (f) a cross oscillation scanning path. By adopting different paths, the distribution of laser energy received by the weld can be adjusted to achieve different effects, for example, path (a) can make the energy more evenly distributed; it can make the energy evenly distributed along the direction parallel to the weld; path (c) can expand the molten pool and widen the weld; path (d) can widen the weld on the basis of path (b) and make the energy evenly distributed along the direction perpendicular to the weld; path (e) can widen the weld on the basis of path (b) and make the energy evenly distributed along the direction parallel to the weld; path (f) can widen the weld on the basis of path (b) and make the energy evenly distributed along the direction parallel to the weld; and path (b) can widen the weld on the basis of path (b) and make the energy evenly distributed along the direction parallel to and perpendicular to the weld.

[0036] Figure 3 It is a schematic diagram of the coordination between the concentric circle oscillation scanning path and the linear movement of the platform. DETAILED DESCRIPTION

[0037] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0038] A laser dynamic oscillation high-precision welding method for transparent materials comprises the following steps:

[0039] Step 1, directly place the material to be welded or fix it with a fixture and then place it on a two-dimensional motion platform, and adjust the z-axis of the motion platform to focus the laser beam on the interface to be welded;

[0040] Step 2, turn on the high-speed scanning device, load the preset scanning path, and make the tightly focused ultrafast laser oscillate and scan at high speed in a small range.

[0041] Step 3, loading the preset platform motion trajectory, synchronously controlling the two-dimensional motion platform, so that the laser moves and welds along the preset trajectory while oscillating and scanning at a high speed.

[0042] The scanning path may be a single circular path, a rectangular path, a concentric circular path, a parallel path, a vertical path, a cross path, etc., or a complex path formed by combining multiple simple paths. The composite path is formed by combining multiple simple paths, and the scanning times and scanning speed of each path may be changed according to actual conditions.

[0043] It is suitable for precision welding of various transparent materials with transparent or non-transparent materials, such as welding between transparent plastics, glass, gems, diamonds, ceramics, crystals and other materials, or welding between the above transparent materials and non-transparent materials, such as opaque plastics, semiconductors, metals, ceramics, etc.

[0044] The width of a single weld is within 3-100μm, which can be adjusted according to actual needs by replacing different magnification objective lenses and changing the oscillation scanning range. The diameter of the laser focus spot is usually within the range of 0.5-10μm, the oscillation scanning area is usually 5-100 times the diameter of the laser focus spot, and the oscillation scanning speed is usually 10-10 times the platform direct writing speed. 4 Ultrafast lasers generally use picosecond or femtosecond lasers, with a power of 1-100W and a repetition frequency of 50-5000kHz.

[0045] Embodiment 1: An embodiment of a laser dynamic oscillation high-precision welding method for transparent materials, specifically comprising the following steps:

[0046] A picosecond laser with a central wavelength of 1064nm, a pulse width of 10ps, a maximum power of 60W, and an adjustable repetition frequency (ranging from 50 to 1000kHz) was used as the welding light source. Two pieces of JGS2 quartz glass with a size of 5×5×0.5mm were selected as the experimental material.

[0047] The glass to be welded is fixed with a fixture and placed on a two-dimensional motion platform, and the position of the two-dimensional motion platform is adjusted so that the laser beam can be focused on the interface to be welded. Before welding, it was observed that there were no obvious interference fringes between the two pieces of glass, and no optical contact was achieved, indicating that the surface quality of the two pieces of glass was low.

[0048] In order to achieve a good sealing effect, different welding parameters were used for experiments, and finally the sealing welding was successfully achieved. The specific welding parameters are as follows: laser power is 3W, repetition frequency is 100kHz, the number of pulse train sub-pulses is 3, the movement speed of the two-dimensional motion platform is 0.04mm / s, and the galvanometer scanning speed is 1mm / s. During welding, a single circle oscillation scanning path is used, the circle diameter is 50μm, and the welding track is a 4×3mm right-angle rectangle.

[0049] After welding, the weld and its edge were observed under a microscope. No microcracks were observed in all weld areas and their edges, including the right-angle corners of the weld. The sample was immersed in water for 10 days, and no obvious signs of water penetration were observed in the area surrounded by the weld. The welding results show that the oscillation scanning welding method can achieve good sealing.

[0050] Example 2: Another example of a laser dynamic oscillation high-precision welding method for transparent materials, used to compare the effects of oscillation scanning on quartz glass welding.

[0051] A femtosecond laser with a central wavelength of 1030nm, a pulse width of 800fs, a maximum power of 10W, and a repetition frequency of 50-300kHz was used. The experimental material was JGS2 quartz glass (5×5×0.5mm). The glass to be welded was fixed with a clamp and placed on a two-dimensional motion platform. There were no obvious interference fringes before welding, and no optical contact was achieved, indicating that the surface quality of the two pieces of glass was low. In order to compare the effect of oscillation scanning on quartz glass welding, a comparative experiment was conducted using a non-oscillation scanning and a single circle oscillation scanning path. After many experiments, only the sample welded using a single circle oscillation scanning path successfully achieved a good sealing effect. The specific welding parameters are as follows: laser power of 5W, repetition frequency of 50kHz, number of pulse train sub-pulses of 1, platform movement speed of 0.04mm / s, and galvanometer scanning speed of 1mm / s. A single circle oscillation scanning path was used, the circle diameter was 30μm, and the welding track was a 4×3mm right-angle rectangle. After welding, no microcracks were observed under a microscope in all weld areas and their edges, including the right-angle corners of the weld. After the sample was immersed in water for 10 days, no obvious signs of water penetration were observed in the area surrounded by the weld. The welding results show that it is easier to achieve a good seal using the oscillation scanning welding method than without oscillation scanning welding, which may be related to the fact that oscillation scanning effectively expands the volume of the molten pool. When oscillation scanning is not used, the size and depth of the molten pool are small, making it difficult to keep the focus on the welding interface continuously and stably throughout the welding process.

[0052] Example 3: An example of a transparent material laser dynamic oscillation high-precision welding method using a three-dimensional galvanometer, used to compare the effects of different three-dimensional oscillation scanning paths on the depth of the welding molten pool.

[0053] A picosecond laser with a central wavelength of 1064nm, a pulse width of 10ps, a maximum power of 60W, and a repetition frequency of 50-1000kHz was used. The experimental materials were two pieces of JGS2 quartz glass (5×5×0.5mm). The glass to be welded was fixed with a clamp and placed on a two-dimensional motion platform. There were no obvious interference fringes before welding, and no optical contact was achieved, indicating that the surface quality of the two pieces of glass was low. In order to further increase the depth of the welding molten pool, a three-dimensional galvanometer was used to make the laser focus oscillate at high speed in the three dimensions of XYZ. The effects of different three-dimensional oscillation scanning paths on the welding molten pool were compared. Two scanning paths were used for comparative experiments. The other laser welding parameters selected remained unchanged, as follows: laser power of 3W, repetition frequency of 100kHz, number of pulse train sub-pulses of 3, platform movement speed of 0.04mm / s, and galvanometer scanning speed of 5mm / s. The two scanning paths are: concentric circle scanning path and concentric cylinder scanning path (oscillating the concentric circles in the Z-axis direction). After welding, the weld cross section was observed under a microscope, and it was found that the weld pool using the concentric cylindrical scanning path was significantly deeper than the weld pool using the concentric circle scanning path. The welding results show that the XYZ three-dimensional oscillating scanning path has a good effect on increasing the weld pool depth.

[0054] Figure 2 It is a schematic diagram of the relationship between weld width, scanning range and spot diameter. The weld width is equal to the sum of the scanning range and the spot diameter. Figure 3 This is a schematic diagram of the movement path of the laser focus relative to the material under the coordination of a single circular oscillation scanning path and the linear movement of the platform. Compared with direct writing welding of the same path relying solely on platform movement, the advantage of oscillation scanning is that the scanning speed is fast, and the entire scanning area of ​​the galvanometer can remain in a molten state, which can not only effectively expand the molten pool, but also produce the effect of stirring the molten pool and reduce stress accumulation. When the same path is directly written, if the platform moves too slowly, the phenomenon that the front section has solidified and the rear section begins to melt will occur, and a complete large molten pool cannot be formed, and stress is also easy to accumulate.

[0055] It should be pointed out that the above embodiments are intended to facilitate understanding of the technical solutions of the present invention rather than to limit them; any modification, equivalent substitution and improvement of the present invention are within the protection scope of the present invention.

Claims

1. A laser dynamic oscillation high-precision welding method for transparent materials, characterized in that: The steps include: S1. stacking a first sample and a second sample on a two-dimensional motion platform, wherein at least one sample is a transparent material; S2. Adjust the two-dimensional motion platform so that the ultrafast laser beam is focused on the interface between the first sample and the second sample to be welded; S3. Turn on the high-speed scanning device, load the preset scanning path, and use a tightly focused ultrafast laser to perform high-speed oscillation scanning within the scanning path; S4. Load the preset motion trajectory of the two-dimensional motion platform, and synchronously control the two-dimensional motion platform so that while the laser beam is performing high-speed oscillation scanning, the two-dimensional motion platform drives the material to be welded to perform mobile welding according to the preset motion trajectory.

2. The laser dynamic oscillation high-precision welding method for transparent materials according to claim 1, characterized in that: The diameter of the laser focused spot is 0.5-10μm; the maximum amplitude of the oscillation scan is 5-100 times the diameter of the laser focus spot; the width of a single weld is between 0-100μm; the focus spot oscillation scanning speed is 10-10^4 times the platform direct writing speed.

3. The laser dynamic oscillation high-precision welding method for transparent materials according to claim 1 or 2, characterized in that: The scanning path is a single circular path, a rectangular path, a concentric circular path, a parallel path, a vertical path, a cross path, or a complex path formed by combining multiple simple paths.

4. The laser dynamic oscillation high-precision welding method for transparent materials according to claim 1, characterized in that: The high-speed oscillation scanning can be performed in the XY plane parallel to the sample surface, or simultaneously in the XYZ three dimensions; and the oscillation scanning welding path is optimized and selected according to actual welding requirements.

5. The laser dynamic oscillation high-precision welding method for transparent materials according to claim 1, characterized in that: The transparent material includes transparent plastic, glass, gemstone, diamond, ceramic, and crystal; the other sample is a transparent material or a non-transparent material, and the non-transparent material includes plastic, semiconductor, metal, and ceramic.

6. The laser dynamic oscillation high-precision welding method for transparent materials according to claim 1, characterized in that: The ultrafast laser is a picosecond or femtosecond laser with a power of 1-100W and a repetition frequency of 25-5000kHz.

7. A welding system for implementing the laser dynamic oscillation high-precision welding method for transparent materials according to any one of claims 1 to 6, characterized in that: include: Lasers, used to emit ultrafast laser pulses; A beam expander and collimator lens, used for expanding and collimating the laser beam; A power regulation system for regulating the power of the laser beam; A tightly focused high-speed scanning system, used to tightly focus the laser beam and achieve high-speed oscillation scanning, at least including a lens or a reflector to adjust the optical path; Microscopic imaging system, used to achieve coaxial real-time observation; A two-dimensional motion platform is used to drive the sample to be welded to move along a predetermined trajectory; Among them, the device realizes a dynamic oscillation scanning strategy by combining the galvanometer high-speed scanning and the platform movement. While the moving platform is directly writing welding, the laser focus spot is oscillated and scanned at high speed under the control of the tightly focused high-speed scanning system to improve the size of the welding pool, welding efficiency and welding quality.

8. The welding system according to claim 7, characterized in that The microscopic imaging system comprises a CMOS camera, a tube lens and an objective lens.

9. The welding system according to claim 7, characterized in that: The high-speed scanning system comprises a high-speed scanning galvanometer, a high-speed scanning rotating mirror and a high-speed acousto-optic scanning device.

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