High-robustness binding surface micro riveting type ultrashort pulse laser welding system

Abstract

The utility model discloses a high-robustness binding surface micro riveting type ultrashort pulse laser welding system which comprises an ultrashort pulse laser, a half-wave plate, a polarization beam splitter prism, a mechanical shutter, a dichroscope and a focusing lens which are sequentially connected in the light path propagation direction. The ultrashort pulse laser emits linear polarization laser with the wavelength range of lambda; laser vertically enters the half-wave plate to change the polarization direction, and then is separated into P polarized light or S polarized light through the polarization beam splitter prism; one of the P polarized light and the S polarized light enters a dichroscope after passing through a mechanical shutter, the dichroscope reflects input laser, and the polarized light reflected by the dichroscope sequentially passes through a focusing lens and a to-be-welded object with large light transmittance and then is focused on the binding face of the two to-be-welded objects in a defocusing mode; and under the action of the laser beams, tiny welding spots crossing the binding surfaces of the two objects to be welded are formed in the axis direction of the laser beams. The welding device is wide in application range and high in welding strength and robustness.

Description

Highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces Technical Field

[0001] This utility model relates to the fields of optical technology and material welding, and in particular to a highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces. Background Technology

[0002] Currently, after decades of development, ultrashort pulse lasers have demonstrated strong practical potential in the field of laser welding. However, the low robustness of ultrashort pulse laser welding has always been a major obstacle hindering its practical application. Existing technologies mostly employ continuous scanning welding methods. For example, the technical solutions disclosed in patents CN116117322A and CN113292233A achieve welding through continuous line scanning. Another example is the laser spot welding connection proposed in patent CN118808912A, which is essentially a continuous scanning method, with a centimeter-scale helical structure in the welding area. However, this type of welding method cannot achieve reliable welding when dealing with complex curved materials with poor surface adhesion, limiting its robustness and applicability. Summary of the Invention

[0003] This invention provides a highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces to solve the technical problems existing in the prior art.

[0004] The technical solution adopted by this utility model to solve the technical problems existing in the prior art is as follows:

[0005] A robust micro-riveting ultrashort pulse laser welding system for bonding surfaces includes an ultrashort pulse laser, a half-wave plate, a polarizing beam splitter prism, a mechanical shutter, a dichroic mirror, and a focusing lens connected sequentially in the optical path propagation direction; two objects to be welded are stacked on a stage; the light corresponds to the wavelength range λ, and the transmittance of one of the objects is ≥90%;

[0006] An ultrashort pulse laser emits a linearly polarized laser beam with a wavelength range including λ. The laser beam is perpendicularly incident on a half-wave plate, where its polarization direction is changed. It is then separated into P-polarized or S-polarized light by a polarizing beam splitter. One of the P-polarized or S-polarized light passes through a mechanical shutter and is incident on a dichroic mirror. The dichroic mirror reflects the input laser beam. The polarized light reflected from the dichroic mirror passes sequentially through a focusing lens and then through the objects to be welded, which have high transmittance. Finally, it is defocused and focused onto the mating surfaces of the two objects. Under the action of the focused laser beam, a tiny weld point is formed along the laser beam axis, spanning the mating surfaces of the two objects, thus welding them together.

[0007] Furthermore, objects with higher light transmittance are placed below, and the stage is either a transparent stage or a stage with a hollow corresponding welding area.

[0008] Furthermore, the mating surfaces of the two objects to be welded are planes, curved surfaces, or composite surfaces composed of planes and curved surfaces.

[0009] Furthermore, it also includes a control unit, a stage that is a three-dimensional moving platform; several discrete laser welding points are set on the mating surfaces of the two objects to be welded; the control unit controls the three-dimensional movement of the stage, so that the laser beam focus is aligned with the discrete laser welding points, and controls the operation of the ultrashort pulse laser and the mechanical shutter to complete the spot welding of the discrete laser welding points.

[0010] Furthermore, it also includes an image acquisition unit, which includes an infinity imaging system, a flat beam splitter, and an LED light source; the LED light source is used to provide white light; the flat beam splitter is used to reflect the white light to the area to be welded and transmit the reflected detection light to the infinity imaging system; the infinity imaging system and the focusing lens are combined to form a confocal microscope structure;

[0011] The white light emitted by the LED light source passes through a beam splitter, a dichroic mirror, and a focusing lens in sequence and is focused onto the mating surfaces of the two objects to be welded. The light returning from the focal point passes through the focusing lens, the dichroic mirror, and the flat beam splitter in sequence and generates an image in the infinity imaging system. The position of the laser beam focal point and / or the size of the weld joint are determined by the generated image.

[0012] Furthermore, the transparent stage is made of glass.

[0013] Furthermore, the numerical aperture (NA) of the focusing lens is 0.4–0.6, and the working distance is 10–30 mm.

[0014] The advantages and positive effects of this invention are as follows: This invention provides a highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces, enabling spot welding of the bonding surfaces of two objects to be welded, thus replacing the traditional continuous scanning welding technique. A strong connection between materials is achieved by sequentially applying laser pulses of a certain flux to multiple discrete welding points with reasonable spacing. Both materials maintain high welding strength while exhibiting high robustness.

[0015] When an object with high light transmittance is placed below, a transparent stage or a stage with a hollow corresponding welding area can be used. The laser beam can be incident upwards onto the bonding surface of the objects to be welded, with the bonding surface above the laser beam. During welding, depending on the weight of the upper object to be welded, bonding can be achieved through the material's own weight without clamps, or appropriate auxiliary pressure can be applied using clamps. When bonding is achieved through the material's own weight, without the application of additional mechanical pressure from external clamps or clamping devices, residual stress in the welding area can be effectively reduced, which helps to improve the long-term stability and structural integrity of the weld joint.

[0016] This invention features a three-dimensional movable stage, enabling the creation of arbitrary two-dimensional or three-dimensional discrete laser welding point array structures, such as linear, matrix, spiral, or honeycomb array structures. Spot welding at each discrete laser welding point does not interfere with each other, and each micro-welding operation is independent of the others.

[0017] This invention is applicable to laser welding of one transparent object to another transparent or non-transparent object. It can provide welding strength equivalent to continuous scanning welding. The contact surfaces of the two objects to be welded are planar, curved, or composite surfaces composed of a combination of planar and curved surfaces. This invention is applicable to a wide range of materials and shapes of objects to be welded, and can achieve high welding strength and high robustness in all cases. Attached Figure Description

[0018] Figure 1 is a schematic diagram of the structure of a highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces according to this utility model.

[0019] Figure 2 is a schematic diagram of a highly robust micro-riveting ultrashort pulse laser welding method for bonding surfaces according to this utility model.

[0020] In the diagram: 1. Ultrashort pulse laser; 2. Half-wave plate; 3. Polarizing beam splitter prism; 4. Mechanical shutter; 5. Infinity imaging system; 6. Flat beam splitter; 7. LED light source; 8. Dichroic mirror; 9. Focusing lens; 10. Stage; 11. Lower object; 12. Upper object; 13. Focused laser beam; 14. Discrete laser welding point. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] In the description of this utility model, the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and do not require that this utility model be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this utility model. The terms "connected" and "linked" used in this utility model should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a direct connection or an indirect connection through intermediate components; or an electrical connection or signal transmission. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0023] Please refer to Figures 1 and 2. A highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces includes an ultrashort pulse laser 1, a half-wave plate 2, a polarizing beam splitter prism 3, a mechanical shutter 4, a dichroic mirror 8, and a focusing lens 9, which are connected sequentially in the optical path propagation direction; two objects to be welded are stacked on a stage 10; the light corresponds to the wavelength range λ, and the transmittance of one of the objects is ≥90%.

[0024] The ultrashort pulse laser 1 is used to emit a laser beam with a wavelength range including λ; the half-wave plate 2 is used to change the polarization direction of the laser beam; the polarization beam splitter prism 3 is used to transmit P-polarized light in linearly polarized light and reflect S-polarized light; the mechanical shutter 4 is used to control the time of the beam's passage; the dichroic mirror 8 is used to reflect the laser beam and transmit white light; and the focusing lens 9 is used to converge parallel light rays to a point.

[0025] An ultrashort pulse laser 1 emits a linearly polarized laser beam with a wavelength range including λ. The laser beam is perpendicularly incident on a half-wave plate 2, where its polarization direction is changed. It is then separated into P-polarized light or S-polarized light by a polarizing beam splitter prism 3. One of the P-polarized light and S-polarized light passes through a mechanical shutter 4 and is incident on a dichroic mirror 8. The dichroic mirror 8 reflects the input laser beam. The polarized light reflected from the dichroic mirror 8 passes sequentially through a focusing lens 9 and the objects to be welded with high transmittance. It is then focused in a defocused manner onto the mating surfaces of the two objects to be welded. Under the action of the focused laser beam 13, a tiny weld point is formed along the laser beam axis, spanning the mating surfaces of the two objects to be welded, thus welding the two objects together.

[0026] Under the action of an ultrashort pulse laser, the two materials in the welding area generate plasma. After the plasma solidifies rapidly, it forms a tiny weld point. The function of the tiny weld point is similar to that of a rivet, which firmly connects the two objects to be welded, thereby achieving a strong weld.

[0027] Two objects to be welded are stacked on the platform. The object to be welded on top is called the upper object 12. The object to be welded below is called the lower object 11.

[0028] Preferably, objects with higher light transmittance can be placed below, and the stage 10 can be a transparent stage 10 or a stage 10 with a hollow corresponding welding area. The transparent stage 10 can be made of glass or sapphire window.

[0029] Preferably, the mating surfaces of the two objects to be welded can be planes, curved surfaces, or composite surfaces composed of planes and curved surfaces.

[0030] Preferably, it may also include a control unit, and the stage 10 may be a three-dimensional moving platform; a plurality of discrete laser welding points 14 may be set on the mating surfaces of the two objects to be welded; the control unit controls the three-dimensional movement of the stage 10 so that the laser beam focus is aligned with the discrete laser welding points 14, and controls the operation of the ultrashort pulse laser 1 and the mechanical shutter 4 to complete the spot welding of the discrete laser welding points 14.

[0031] Preferably, for certain specially shaped mating surfaces, the stage 10 can not only achieve three-dimensional translational motion, but also rotational and other attitude adjustments, enabling motion with 5 or more degrees of freedom to ensure that the laser always incident along the normal of the mating surface.

[0032] Preferably, it may also include an image acquisition unit, which may include an infinity imaging system 5, a flat beam splitter 6, and an LED light source 7; the LED light source 7 is used to provide white light; the flat beam splitter 6 is used to reflect the white light to the area to be welded and transmit the reflected detection light to the infinity imaging system 5; the infinity imaging system 5 and the focusing lens 9 are combined to form a confocal microscope structure.

[0033] The Infinity Imaging System 5, also known as the Infinity Optical System or Infinity Imaging Microscopy System, can be used for high-resolution cell and tissue section analysis, high-magnification metallographic analysis, and detection of dimensional tolerances of tiny objects such as chips.

[0034] For example, the high-magnification metallographic measuring microscope in existing technology uses an infinity optical system to observe the grain morphology, phase composition and inclusion distribution of metallic materials.

[0035] The white light emitted by the LED light source 7 can be focused onto the mating surfaces of the two objects to be welded after passing through the beam splitter, dichroic mirror 8, and focusing lens 9 in sequence. The light returning from the focal point can be generated into an image in the infinity imaging system 5 after passing through the focusing lens 9, dichroic mirror 8, and flat beam splitter 6 in sequence. The position of the laser beam focal point and / or the size of the weld joint are determined by the generated image.

[0036] The generated image can determine the position of the bonding surface corresponding to the laser beam focus, and the defocusing amount can be used to further determine the laser focus position and / or the solder joint size.

[0037] Preferably, it may also include an image processing unit, which receives a spot welding state diagram of the bonding surface of the upper object 12 and the lower object 11 from the image acquisition unit, evaluates the spot welding state based on the laser spot welding quality evaluation reference state diagram, and sends the evaluation result to the control unit. The control unit outputs a signal to adjust the output parameters of the ultrashort pulse laser 1.

[0038] Preferably, the image processing unit may be equipped with a neural network; the neural network, based on the laser spot welding quality evaluation reference state diagram, performs defect marking and defect classification on the welding points of the mating surfaces of the upper object 12 and the lower object 11.

[0039] Using existing neural networks, such as Graph Neural Networks (GNNs), we can learn graph-structured data, extract and discover features and patterns in the graph-structured data, and satisfy graph learning tasks such as clustering, classification, prediction, segmentation, and generation.

[0040] This invention also provides a robust micro-riveting ultrashort pulse laser welding method for bonding surfaces using the aforementioned robust bonding surface micro-riveting ultrashort pulse laser welding system. The method involves setting the output parameters of the ultrashort pulse laser 1; setting several discrete laser welding points 14 on the bonding surfaces of the two objects to be welded; acquiring the three-dimensional coordinates of each discrete laser welding point 14 relative to a reference point on the bonding surfaces of the two objects; stacking the two objects to be welded on a stage 10; moving the stage 10 so that the focal point of the laser beam from the focusing lens 9 is aligned with the reference point, with the distance between the two points being the defocus distance h; using the current position of the stage 10 as the working origin; setting the welding sequence of each discrete laser welding point 14; and welding according to the welding sequence and the phase ratio of each discrete laser welding point 14. The stage 10 is moved according to the three-dimensional coordinates of the reference point; the position of the stage 10 when the laser beam focus is aligned with a discrete laser welding point 14 and the distance between the laser beam focus and the discrete laser welding point 14 is the defocus distance h is called the welding positioning position of the discrete laser welding point 14; when the stage 10 moves to the welding positioning position of the discrete laser welding point 14, the mechanical shutter 4 is opened so that the laser beam can start spot welding at the position of the discrete laser welding point 14, and the number of laser pulses or the laser beam irradiation time is controlled by controlling the ultrashort pulse laser 1 and / or the mechanical shutter 4; after the welding of the discrete laser welding point 14 is completed, the mechanical shutter 4 is closed so that the stage 10 moves to the welding positioning position of the next discrete laser welding point 14 to continue welding.

[0041] When the stage 10 moves to the welding positioning position of the next discrete laser welding point 14, the mechanical shutter 4 is opened so that the laser beam can start spot welding at the discrete laser welding point 14. The number of laser beam pulses or the laser beam irradiation time can be controlled by controlling the ultrashort pulse laser 1 and / or the mechanical shutter 4.

[0042] Repeat the above welding operation until all discrete laser weld points 14 are welded.

[0043] The three-dimensional coordinates of each discrete laser welding point 14 relative to the reference point of the mating surface of the two objects to be welded can be collected using devices such as laser scanners, coordinate measuring machines, and confocal microscopes.

[0044] The defocus distance h is determined based on factors such as the materials of the two objects to be welded and the output parameters of the ultrashort pulse laser 1. It can be determined based on experience or through experimental analysis.

[0045] Preferably, a welding trajectory can also be set between discrete laser welding points 14 so that the laser beam scans and welds along the welding trajectory.

[0046] Preferably, the mating surfaces of the two objects to be welded can be divided into several grids, and the center point of the grid can be initially set as a discrete laser welding point 14.

[0047] Preferably, the position of the initially set discrete laser welding point 14 can be adjusted according to the degree of adhesion between the mating surfaces of the two objects to be welded.

[0048] Discrete laser solder points 14 can also be added or their positions adjusted according to the lattice sparsity of discrete laser solder points 14.

[0049] The position of discrete laser weld points 14 can be optimized simultaneously based on the principles of uniform dispersion and minimum fit. The principle of uniform dispersion means that the number of discrete laser weld points 14 per unit area in each zone on the bonding surfaces of the two objects to be welded is approximately equal. The principle of minimum fit means that when setting the position of discrete laser weld points 14, the position with the smaller fit between the bonding surfaces of the two objects to be welded is preferred.

[0050] Preferably, the following welding processing parameters can be set according to the materials of the two objects to be welded: laser wavelength, pulse width, incident laser beam diameter, laser power, pulse laser repetition frequency, focusing lens 9N.A. value or focal length, number of single-point pulses or laser irradiation time, and defocusing amount.

[0051] Preferably, one of the two objects to be welded is a transparent material, and the output parameters of the ultrashort pulse laser 1 can be set as follows: pulse width of 300±100fs, repetition frequency of 100~1000kHz; numerical aperture NA of focusing lens 9 of 0.4~0.6, and working distance of 10~30mm.

[0052] The structure and working principle of this utility model are further illustrated below with a preferred embodiment:

[0053] A robust micro-riveting ultrashort pulse laser welding system for bonding surfaces includes an ultrashort pulse laser 1, a half-wave plate 2, a polarizing beam splitter prism 3, a mechanical shutter 4, a dichroic mirror 8, and a focusing lens 9, which are connected sequentially in the optical path propagation direction; two objects to be welded are stacked on a stage 10; the light corresponds to the wavelength range λ, and the transmittance of one of the objects is ≥90%.

[0054] Two objects to be welded are stacked on a stage. The lower object 11 is made of glass, and the upper object 12 is made of a thin film of pure aluminum. The contact surfaces of the two objects are flat. The stage 10 is a transparent glass stage.

[0055] An ultrashort pulse laser 1 emits a linearly polarized laser beam with a wavelength range including λ. The laser beam is perpendicularly incident on a half-wave plate 2, where its polarization direction is changed. It is then separated into P-polarized light or S-polarized light by a polarizing beam splitter prism 3. One of the P-polarized light and S-polarized light passes through a mechanical shutter 4 and is incident on a dichroic mirror 8. The dichroic mirror 8 reflects the input laser beam. The polarized light reflected from the dichroic mirror 8 passes from bottom to top through a focusing lens 9 and then through the lower object 11, which has a higher transmittance, before being focused in a defocused manner onto the bonding surface of the two objects to be welded. Under the action of the focused laser beam 13, a tiny weld point is formed along the laser beam axis, spanning the bonding surface of the two objects to be welded, thus welding the two objects together.

[0056] It also includes an image acquisition unit, which includes an infinity imaging system 5, a flat beam splitter 6, and an LED light source 7. The LED light source 7 is used to provide white light. The flat beam splitter 6 is used to reflect the white light to the area to be welded and transmit the reflected detection light to the infinity imaging system 5. The infinity imaging system 5 and the focusing lens 9 are combined to form a confocal microscope structure.

[0057] The white light emitted by the LED light source 7 passes through a beam splitter, a dichroic mirror 8, and a focusing lens 9 in sequence and is focused onto the mating surfaces of the two objects to be welded. The light returning from the focal point passes through the focusing lens 9, the dichroic mirror 8, and the flat beam splitter 6 in sequence and generates an image in the infinity imaging system 5. The position of the laser beam focal point and / or the size of the weld joint are determined by the generated image.

[0058] The output parameters of the ultrashort pulse laser 1 are set as follows: center wavelength of 1030 nm; pulse width of 300 fs; average power of 400 mW; repetition frequency of 100 kHz; numerical aperture (NA) of focusing lens 9 of 0.4; working distance of 20 mm; focusing point 15 micrometers above the bonding surface of upper object 12 and lower object 11; discrete laser welding points 14 are arranged in a matrix, with a spacing of 100 micrometers between the welding points. There are 400 welding points, forming a 20×20 square array.

[0059] The mating surfaces of the two objects to be welded are divided into several grids, and the center point of the grid is set as the discrete laser welding point 14.

[0060] Using the highly robust micro-riveting ultrashort pulse laser welding method of this invention, after welding two objects to be welded, the tensile strength of the welded parts exceeds the yield strength of the aluminum film after tensile strength testing.

[0061] The welding strength originates from the mixing of plasmas of the two materials in the welding area and the subsequent rapid solidification process; this invention can control the welding strength by controlling the output parameters of the ultrashort pulse laser 1 and the opening and closing time of the mechanical shutter 4.

[0062] The ultrashort pulse laser 1, half-wave plate 2, polarizing beam splitter prism 3, mechanical shutter 4, infinity imaging system 5, flat beam splitter 6, LED light source 7, dichroic mirror 8, focusing lens 9, stage 10, control unit, image acquisition unit, image processing unit, neural network, three-dimensional moving platform and other components, devices and functional modules described in this application can all adopt applicable components and functional modules in the prior art, or adopt components, devices and functional modules in the prior art and construct them using conventional technical means.

[0063] The embodiments described above are only used to illustrate the technical ideas and features of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it accordingly. The patent scope of this utility model should not be limited by these embodiments. That is, any equivalent changes or modifications made to the spirit disclosed in this utility model still fall within the patent scope of this utility model.

Claims

1. A highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces, characterized in that, The assembly consists of an ultrashort pulse laser, a half-wave plate, a polarizing beam splitter prism, a mechanical shutter, a dichroic mirror, and a focusing lens, all connected sequentially along the optical path. Two objects to be welded are stacked on a stage. The wavelength range corresponds to λ, and one of the objects has a transmittance ≥90%. The ultrashort pulse laser emits a linearly polarized laser beam with a wavelength range including λ. The laser beam is perpendicularly incident on the half-wave plate, where its polarization direction is changed. It is then separated into P-polarized or S-polarized light by the polarizing beam splitter prism. One of the P-polarized or S-polarized light passes through the mechanical shutter and is incident on the dichroic mirror. The dichroic mirror reflects the input laser beam, and the polarized light reflected from the dichroic mirror passes sequentially through the focusing lens and the object with higher transmittance to be welded, before being focused in a defocused manner onto the mating surface of the two objects. Under the action of the focused laser beam, a tiny weld point is formed along the laser beam axis, spanning the mating surface of the two objects, thus welding the two objects together.

2. The highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces according to claim 1, characterized in that, Objects with high light transmittance are placed at the bottom, and the stage is either a transparent stage or a stage with a hollow corresponding welding area.

3. The highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces according to claim 1, characterized in that, The mating surfaces of the two objects to be welded are planes, curved surfaces, or composite surfaces composed of planes and curved surfaces.

4. The highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces according to claim 1, characterized in that, It also includes a control unit, a stage that is a three-dimensional moving platform; several discrete laser welding points are set on the mating surfaces of the two objects to be welded; the control unit controls the three-dimensional movement of the stage, so that the laser beam focus is aligned with the discrete laser welding points, and controls the operation of the ultrashort pulse laser and the mechanical shutter to complete the spot welding of the discrete laser welding points.

5. The highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces according to claim 1, characterized in that, It also includes an image acquisition unit, which comprises an infinity imaging system, a flat beam splitter, and an LED light source. The LED light source provides white light. The flat beam splitter reflects the white light to the area to be welded and transmits the reflected detection light back to the infinity imaging system. The infinity imaging system, combined with a focusing lens, forms a confocal microscope structure. The white light emitted by the LED light source passes sequentially through the beam splitter, dichroic mirror, and focusing lens to be focused onto the mating surfaces of the two objects to be welded. The light returning from the focal point passes sequentially through the focusing lens, dichroic mirror, and flat beam splitter to generate an image in the infinity imaging system. The generated image determines the position of the laser beam focal point and / or the weld joint size.

6. The highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces according to claim 1, characterized in that, The transparent stage is made of glass.

7. The highly robust micro-riveting ultrashort pulse laser welding system for bonding surfaces according to claim 1, characterized in that, The numerical aperture (NA) of the focusing lens is 0.4–0.6, and the working distance is 10–30 mm.

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