A method and system for ultra-precision micro-hole multi-energy field coupling fabrication

Abstract

This application belongs to the field of micro-hole machining technology for hard and brittle crystalline materials, specifically relating to an ultra-precision micro-hole multi-energy field coupling machining method and system. This method sets the laser pulse frequency and power according to the workpiece material type and the micro-hole depth-to-diameter ratio, positions the laser focus at the bottom of the hole inside the workpiece, and forms a modified structure extending along the hole axis by controlling the matching of the laser spot with the hole diameter and the laser spot movement trajectory. During machining, the plasma nozzle moves coaxially with the laser to achieve immediate removal of the modified area, suppressing the heat-affected zone and hole taper. Simultaneously, an axial ultrasonic vibration device applies vibration to the workpiece, promoting chip removal and reducing stress and crack formation. This application solves the problems of severe thermal damage, poor hole shape accuracy, low machining efficiency, and high energy consumption in existing micro-hole machining technologies, achieving high-quality and high-precision machining of high-depth-to-diameter ratio micro-holes in hard and brittle transparent crystalline materials.

Description

Technical Field

[0001] This application belongs to the field of micropore processing technology for hard and brittle crystalline materials, and specifically relates to an ultra-precision micropore multi-energy field coupling processing method and system. Background Technology

[0002] Hard, brittle, and transparent crystalline materials such as sapphire, crystal, quartz, and glass possess excellent mechanical and optical properties, making them frequently used in the manufacture of various precision parts. These materials are widely applied in optical components, aerospace devices, and precision electronic devices. In these applications, it is often necessary to precisely machine micro-holes onto the material surface. However, due to the high hardness and brittleness of these materials, the micro-hole machining process presents significant challenges, especially in the precision machining of micro-holes with large depth-to-diameter ratios.

[0003] Currently, milling is the main method for machining round holes in hard and brittle materials, relying on the micro-cutting action of abrasive grains on the surface of the grinding head to remove material. However, during micro-hole machining, the high hardness and brittleness of the material result in large grinding forces, which can easily lead to grinding head breakage. At the same time, it is difficult to remove grinding chips, which can easily cause blockages, seriously affecting machining efficiency and quality.

[0004] Laser processing technology uses a high-energy laser beam to melt and vaporize local materials on the surface of a workpiece to form micro-holes. However, during the laser processing of micro-holes, due to the high energy, thermal stress can cause a large thermal damage layer around the hole, reducing the surface quality of the hole. At the same time, when the depth of the hole is large, a tapered hole is often formed, making it difficult to guarantee dimensional accuracy.

[0005] Plasma processing technology relies on the mechanical impact and thermal ablation of high-energy plasma plumes to remove materials. However, if applied to transparent, hard, and brittle materials alone, it requires high-energy, high-temperature plasma, resulting in excessively high processing costs and defects such as thermal damage in the processing area. Furthermore, the material removal efficiency is extremely low on non-conductive transparent materials such as diamond and calcium fluoride, making it difficult to achieve efficient processing of micropores.

[0006] To address these issues, researchers have proposed a single laser-induced machining method. This method utilizes laser energy to generate localized microcracks or amorphous regions on or inside the workpiece surface. These weakened regions are then removed using other subsequent processing methods, thus reducing the difficulty of material removal. However, the laser-induced microcracks or amorphous layers created by this method are difficult to control precisely, resulting in inconsistent size and distribution. This leads to irregular apertures or surface defects in subsequent processing. Improper laser energy control can easily generate excessive heat-affected zones or even macroscopic cracks in the workpiece, severely impacting the reliability of the parts. Furthermore, ultrasonic-assisted machining technology has also gained attention in recent years. This method uses the ultrasonic frequency vibration of a tool head to drive abrasive particles to impact the workpiece surface, achieving the purpose of removing material. Although this method offers high precision, its processing efficiency is very low, limiting its large-scale application.

[0007] In summary, existing single-laser processing, plasma processing, and ultrasonic-assisted processing methods all suffer from low efficiency, significant thermal damage, insufficient hole precision, or high processing costs in machining micro-holes in hard, brittle, and transparent materials. Therefore, there is an urgent need for an innovative processing method involving multi-energy field coupling to fully leverage the advantages of various processing methods and solve the technical challenges of efficient and high-precision machining of micro-holes in hard, brittle, and transparent materials. Summary of the Invention

[0008] To address the technical problems of severe thermal damage, insufficient hole shape accuracy, low processing efficiency, and high energy consumption and cost in the micro-hole processing of hard, brittle, and transparent crystalline materials (such as sapphire, crystal, quartz, and glass), this application provides an ultra-precision micro-hole multi-energy field coupling processing method and system. This method achieves efficient, low-damage, and high-precision micro-hole processing of hard, brittle, and transparent crystalline materials by synergistically coupling three energy fields: laser, plasma, and ultrasonic vibration. Based on the laser ablation and amorphization threshold of the material, the laser energy is controlled within the internal modification range to form a controllable modified structure at the bottom of the hole. The modified layer is then removed in real time using a coaxial plasma jet, reducing thermal impact and hole taper. Simultaneously, ultrasonic vibration is used to assist in chip removal and stress reduction, preventing clogging and microcracks. This method is suitable for the manufacturing of precision microstructures in the optical, electronic, and aerospace fields using hard, brittle, and transparent crystalline materials such as sapphire, quartz, calcium fluoride, and diamond.

[0009] On the one hand, this application provides a method for ultra-precision micro-hole multi-energy field coupling fabrication, the method comprising:

[0010] Step 1: Based on the type of hard, brittle, and transparent crystalline material of the workpiece and the depth-to-diameter ratio of the micro-hole to be machined, set the upper limit of the pulse frequency and power of the pulsed laser.

[0011] Step 2: Inject the pulsed laser beam onto the workpiece from the selected incident surface, and position the focal point of the laser beam at the bottom of the micro-hole to be machined inside the workpiece;

[0012] Step 3: Based on the matching relationship between the aperture size of the micro-hole to be processed and the laser spot size, set the corresponding laser beam motion trajectory and control the laser beam to move along the axial direction of the micro-hole, so that the focal point of the focused spot is successively positioned at different depth positions with a predetermined step distance, so as to form an internal modified structure extending from the bottom to the top of the micro-hole along the axial direction of the micro-hole in the vicinity of the focal point inside the material.

[0013] Step 4: Place the plasma nozzle on the opposite side of the workpiece that receives the laser beam, so that the spray axis of the plasma nozzle is coaxial with the propagation axis of the laser beam, and the initial processing position of the sprayed plasma is aligned with the laser focus.

[0014] Step 5: During the processing, the processing position of the plasma and the processing position of the laser focus are moved axially in sync along the processing direction so that the internal modified area induced by the laser is removed synchronously during formation, thereby forming a micro-hole in the workpiece. Axial ultrasonic vibration is then applied to the hard, brittle and transparent material workpiece through an axial ultrasonic vibration generator to remove the debris generated during the plasma processing. This allows the laser energy, plasma energy and ultrasonic vibration energy to work synergistically within the same processing volume to complete the micro-hole processing.

[0015] Step 6: Repeat steps 1-5 until all the predetermined micro-holes on the workpiece surface have been machined;

[0016] Step 7: After processing, use a cleaning medium to clean the micro-holes of the processed workpiece to remove surface residues.

[0017] In a preferred implementation, step 1 further includes:

[0018] Step 1.1: Determine the single-pulse energy when the laser beam focus is located inside the workpiece, based on the internal modification threshold of the workpiece material;

[0019] Single pulse energy for:

[0020]

[0021] In the formula: For margin; Threshold flux; The focal area of ​​the laser beam; The radius of the focused spot;

[0022] Step 1.2: Determine the upper limit of the pulse frequency of the pulsed laser based on the thermal diffusivity of the workpiece material, the radius of the focused spot, and the radius of the micro-hole;

[0023] Upper limit of pulse frequency of pulsed laser :

[0024]

[0025] In the formula: The thermal diffusivity of the material; For safety factor; For dimensions that are subject to heat; Transmittance coefficient;

[0026] Step 1.3: Determine the average output power of the pulsed laser based on the actual pulse repetition frequency, focal spot area, and single pulse energy;

[0027] The actual average output power under constant pulse energy and frequency is:

[0028]

[0029] In the formula: P is the pulsed laser power; s is the laser focal spot area, s= f represents the actual pulse repetition frequency used by the laser during processing; Threshold flux; It is a single pulse energy.

[0030] In a preferred implementation, step 3 further includes:

[0031] Step 3.1: Set the motion trajectory of the laser beam. When the ratio of the aperture of the micro-hole to the diameter of the laser spot is in the range of 1.0 to 1.5, the motion trajectory of the laser beam is a single linear trajectory along the axial direction of the micro-hole. When the ratio of the aperture of the micro-hole to the diameter of the laser spot is greater than 1.5, the motion trajectory of the laser beam is a layered scanning trajectory that performs a covering scan in the plane corresponding to the aperture, moves upward along the axial direction of the micro-hole by a predetermined distance, and repeats the scan.

[0032] Step 3.2: Control the laser beam to move along the axial direction of the micro-hole. When the laser beam’s movement trajectory is a linear trajectory, control the laser head to move continuously along the axial direction at a set speed curve to achieve continuous movement of the focal position. When the laser beam’s movement trajectory is a layered scanning trajectory, control the laser beam to complete the scan in each planar layer and then move along the axial direction by a predetermined step distance. After moving to the position, perform the next layer scan to form an internal modified structure that penetrates the depth direction of the hole by layering.

[0033] In the preferred implementation, further, in step 3.2, the axial velocity of the laser focus with the linear trajectory is:

[0034]

[0035] In the formula: The velocity of the laser focus along the axial direction; It is a single pulse energy; The pulse repetition frequency; Set a value for the target energy linear density;

[0036] interpulse interval Equivalent diameter of laser spot Relationship satisfaction .

[0037] The ultra-precision micro-hole multi-energy field coupling processing method according to claim 3 is characterized in that, in step 3.2, the laser focus movement speed using the layered scanning trajectory is:

[0038]

[0039] In the formula: This refers to the planar scanning speed; f is the single pulse energy; f is the laser repetition frequency; The surface energy density of the target workpiece; The distance between the centers of two adjacent scan lines;

[0040] Pulse pitch satisfy .

[0041] In a preferred implementation, step 4 further includes:

[0042] Step 4.1: Establish a clamping reference based on the bearing surface of the workpiece and the incident surface, install the plasma nozzle on the opposite surface of the incident surface, and adjust the position and attitude of the plasma nozzle through a position adjustment mechanism with X, Y, Z and pitch, yaw and rotation adjustment degrees of freedom, so that its jet axis is coaxial with the propagation axis of the laser beam.

[0043] Step 4.2: Determine the spatial coordinates of the laser focus on the workpiece using a distance sensor and a confocal displacement sensor, and control the relative displacement between the workpiece and the plasma nozzle so that the initial processing position of the plasma jet column coincides with the spatial coordinates.

[0044] In a preferred implementation, further, in step 4.1, the coaxiality of the plasma nozzle's jet axis and the laser beam's propagation axis satisfies the following: radial deviation ≤ 0.05 mm and / or angular deviation ≤ 0.1° over a 100 mm axial length.

[0045] In the preferred implementation, step 5 further includes:

[0046] Step 5.1: Using a CNC motion platform, drive the laser and plasma nozzle to move synchronously along the processing direction, so that the processing position of the plasma jet column and the processing position of the laser focus are spatially overlapped and advance synchronously in the same direction. Thus, while the laser induces the formation of amorphous regions or microcrack regions inside the material, the plasma action achieves synchronous online removal of these regions.

[0047] Step 5.2: Set the ultrasonic vibration generator on the same side as the laser incident surface or on the side where the plasma nozzle is located. The ultrasonic vibration generator applies axial ultrasonic vibration to the hard, brittle and transparent material workpiece along the normal direction of the workpiece. The ultrasonic vibration will vibrate the molten material and debris in the processing area along the channel direction to complete the processing of the micro-hole and optimize the hole wall quality.

[0048] In a preferred implementation, further, in step 7, the cleaning medium includes one of deionized water, a weakly alkaline aqueous solution, or an organic solvent.

[0049] On the other hand, the present invention also provides an ultra-precision micro-hole multi-energy field coupling processing system, the system comprising:

[0050] The laser processing module includes a laser parameter setting module and a laser incident and focusing positioning module;

[0051] The laser parameter setting module is used to set the upper limit of the pulse frequency and power of the pulsed laser according to the type of hard, brittle, and transparent crystal material of the workpiece and the depth-to-diameter ratio of the micro-hole to be processed.

[0052] The laser incident and focusing positioning module is used to incident a pulsed laser beam onto the workpiece from the selected incident surface and to precisely position the focal point of the laser beam at the bottom position of the micro-hole to be machined inside the workpiece.

[0053] The laser motion control module is used to set the motion trajectory of the laser beam according to the matching relationship between the aperture size of the micro-hole to be processed and the laser spot size, and to control the laser beam to move along the axial direction of the micro-hole, so that the focal spot of the focused spot is successively positioned at different depth positions with a predetermined step distance, so as to form an internal modified structure extending from the bottom to the top of the hole along the hole axis inside the material.

[0054] The plasma processing module includes a plasma nozzle disposed on the opposite side of the incident surface of the workpiece. The spray axis of the nozzle is coaxial with the propagation axis of the laser beam, and the initial processing position of the sprayed plasma corresponds to the laser focus position. It is used to move axially synchronously with the laser focus during the processing to remove the internal modification region formed by laser induction, thereby forming a micro-hole in the workpiece.

[0055] The ultrasonic vibration module includes an axial ultrasonic vibration generator, which is used to apply axial ultrasonic vibration to a hard, brittle, transparent crystalline material workpiece during processing to remove debris generated during plasma processing. This allows laser energy, plasma energy, and ultrasonic vibration energy to work synergistically within the same processing volume to complete the micro-hole processing.

[0056] The multi-hole automatic control module is electrically connected to the laser processing module, plasma processing module and ultrasonic vibration module to realize the repeated processing and automatic control of multi-hole positions until the processing of all predetermined micro-holes on the workpiece surface is completed.

[0057] The cleaning module is used to introduce cleaning media into the workpiece surface and the formed micro-holes after processing to remove residual debris and impurities.

[0058] The beneficial effects of this application are:

[0059] First, the ultra-precision micro-hole multi-energy field coupling processing method of this application, compared with the existing technology that uses single laser processing or plasma processing of hard, brittle, and transparent materials, requires a higher thermal energy threshold, which easily causes defects such as thermal damage and thermal cracks on the material processing surface. This application sets the upper limit of pulse frequency and power based on the laser ablation and amorphization threshold of the hard, brittle, and transparent material being processed, so that the incident energy is stably within the energy window of internal modification rather than surface melting. Under the matching of aperture and spot size and step size control, the laser only forms a controllable modified structure in the vicinity of the bottom of the hole, and the modified area is removed in real time by the plasma jet that is coaxial with the laser and synchronously follows the axial direction. By suppressing thermal effects and hole taper, combined with axial ultrasonic vibration for efficient chip removal and stress reduction, and avoiding clogging and microcrack accumulation, low damage, high wall quality, and dimensional consistency are achieved in high aspect ratio micro-hole machining. At the same time, the high energy and cost required for plasma machining alone are reduced. By synergistically coupling three energy fields—laser, plasma, and ultrasonic vibration—in the micro-hole machining of hard, brittle, and transparent crystalline materials, the technical problem of extremely low material removal efficiency when machining non-conductive hard, brittle, and transparent materials such as diamond and calcium fluoride with plasma alone is solved, realizing efficient and high-precision machining of micro-holes on the surface of hard, brittle, and transparent materials.

[0060] Secondly, the pulsed laser output energy is just right to meet the amorphization or cracking threshold of the material, which avoids excessive ablation or energy waste due to excessive laser energy, and also avoids the inability to process the material due to insufficient laser energy, thus saving energy while ensuring processing efficiency.

[0061] Third, both laser processing and plasma processing are non-contact energy beam processing technologies with good versatility and high processing efficiency, enabling efficient processing of micropores on the surface of hard, brittle, and transparent materials.

[0062] Fourth, during the processing, the plasma processing position moves synchronously axially with the laser focus, ensuring that laser-induced processing and ultrasonic-assisted plasma processing are coupled synchronously, realizing the formation and immediate removal of microcracks or amorphous regions inside the crystal, thereby achieving efficient and precise processing of micropores in transparent, hard, and brittle materials.

[0063] Fifth, in the preferred implementation, this application achieves precise control over the micropore processing of hard, brittle, and transparent crystalline materials by adaptively setting laser parameters based on the material's internal modification threshold and thermal diffusivity. This method determines the laser single-pulse energy based on the material's ablation / amorphization threshold and calculates the upper limit of the pulse frequency by combining thermal diffusivity, focused spot radius, and aperture characteristic size. This ensures that the laser energy remains within a safe range for internal material modification rather than surface melting, thereby reducing the risk of thermal damage and cracking. By rationally matching the pulse energy, frequency, and average power, precise control over energy deposition within the material is achieved, ensuring uniform and controllable dimensions of the modified region and providing a stable energy foundation for subsequent multi-energy field coupling processing. This scheme effectively improves the quality and consistency of micropore formation, balancing processing efficiency and hole wall integrity.

[0064] Sixth, in the preferred implementation, this application achieves precise matching of the processing path and optimization of energy distribution by setting the laser beam trajectory and scanning method based on the difference in the ratio of the micro-aperture diameter to the laser spot diameter. When the ratio of aperture diameter to spot diameter is small, a single linear trajectory is used to move continuously along the axial direction to ensure concentrated focal energy and uniform modification area; when the ratio is large, a layered scanning method is used to cover the plane and advance layer by layer along the axial direction, so that the energy action range is uniformly superimposed and the modification depth is continuously controllable. This trajectory control strategy effectively avoids the problem of energy accumulation or uneven modification caused by the mismatch between the spot and aperture diameter, improves the consistency of micro-hole morphology and processing stability, and realizes smooth forming and high-precision controllable processing of high aspect ratio micro-holes.

[0065] Seventh, in the preferred implementation, in the linear trajectory mode, the focal axial velocity is set based on the single pulse energy and repetition frequency to maintain a constant energy density and avoid excessive heat accumulation; in the layered scanning mode, by controlling the coupling relationship between the planar scanning speed and the interlayer spacing, the energy of each modified region is uniformly superimposed without remelting or energy blind spots. This method effectively maintains a stable distribution of laser energy in the depth and lateral directions of the aperture, achieving continuity and consistency of the high aspect ratio micropore modified structure.

[0066] Eighth, the ultra-precision micro-hole multi-energy field coupled processing system of this application achieves efficient and low-damage precision processing of micro-holes in hard, brittle, and transparent crystalline materials through the synergistic integration and control of three energy fields: laser, plasma, and ultrasonic vibration. The laser parameter module, set based on material properties and aspect ratio, precisely controls energy input, avoiding ablation and cracking; the coaxial and synchronous action of laser and plasma allows the modified zone to be removed simultaneously during formation, reducing the heat-affected layer and hole taper; the ultrasonic vibration module achieves efficient debris removal and stress release, improving hole wall quality and processing stability; the multi-hole automatic control module further enables batch and intelligent processing, significantly improving production efficiency and consistency. All required equipment is detachable and highly adaptable, allowing the laser, plasma nozzle, and ultrasonic vibration device to be integrated onto a conventional coordinate grinding machine, enabling a new method for processing hard, brittle, and transparent crystalline materials. Attached Figure Description

[0067] Figure 1 This is a flowchart of the ultra-precision micro-hole multi-energy field coupling processing method in an embodiment of the present invention;

[0068] Figure 2 This is a schematic diagram of the laser-induced ultrasonic milling process for creating micro-holes in a hard, brittle, and transparent crystalline material, as described in an embodiment of the present invention.

[0069] Figure 3 This is a schematic diagram of the laser internal modification threshold of a typical transparent, hard, and brittle material in an embodiment of the present invention;

[0070] Figure 4 This is a schematic diagram illustrating the formation of columnar microcrack regions in a hard, brittle, and transparent crystalline material induced by laser in an embodiment of the present invention.

[0071] Figure 5 This is a schematic diagram of the plasma nozzle ejection direction in an embodiment of the present invention.

[0072] Wherein, 1-laser; 2-laser beam; 3-focal point; 4-micro-hole to be machined; 5-crystal material; 6-plasma nozzle; 7-plasma; 8-ultrasonic generator; 9-modified area inside the workpiece; 10-machined micro-hole; 11-machining direction. Detailed Implementation

[0073] To enable those skilled in the art to better understand the technical solutions of this application, the following will provide a more detailed description of this application in conjunction with the accompanying drawings and embodiments.

[0074] The directional terms such as above, below, left, right, front, and back used in this application are based on the positional relationships shown in the attached drawings. Different attached drawings may result in different positional relationships, therefore they should not be interpreted as limitations on the scope of protection.

[0075] In this application, the terms "installation," "connection," "interlocking," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, or a connection that allows communication between components. They can also refer to a direct connection or an indirect connection through an intermediate medium. They can refer to the internal connection of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0076] Transparent, hard, and brittle materials possess intrinsic properties such as high hardness, high brittleness, and low plasticity. Their thermal conductivity and energy absorption mechanisms are highly sensitive to external fields. When forming micropores on the surface of such materials, the inventors observed that directly removing the material using a single energy field process (e.g., using only lasers or only plasmas) often requires a high energy threshold to achieve effective removal. This easily leads to the formation of significant heat-affected zones at the pore opening and walls, resulting in thermal damage, thermal cracking, and surface quality deterioration. Consequently, it is difficult to simultaneously meet the requirements for micropore geometric accuracy and optical performance.

[0077] Through systematic experimental research, the inventors determined that the root cause of the aforementioned failures and quality fluctuations lies in the fact that the amorphization or cracking threshold of transparent, hard, and brittle materials is lower than the material ablation removal threshold. When volumetric removal is performed directly using high energy, heat and stress accumulate in localized areas, causing the material surface to degrade first and inducing crack propagation. Conversely, if the target structure, namely an amorphous region or columnar microcracks extending along the thickness direction, is induced to form inside the material first, and then the target structure is removed locally, material renewal can be completed at a lower overall energy input level. This effectively reduces heat accumulation and stress mismatch, avoiding the process paradox of causing damage before removal.

[0078] To address the aforementioned technical bottlenecks, the inventors propose an ultra-precision micro-hole multi-energy field coupling processing method for hard, brittle, and transparent materials. This method first uses a pulsed laser to focus on the bottom region of the micro-hole to be processed, and plans the focus movement path according to the aperture-to-depth-diameter ratio to induce the formation of the target structure within the material, namely an amorphous region or vertical columnar microcracks. Subsequently, the initial position of the plasma jet is adjacent to the laser focus region, and it advances synchronously with the laser focus in the processing direction, thereby removing the induced target structure online. Simultaneously, axial or torsional ultrasonic vibration is applied to the workpiece to promote debris removal and maintain the stability of the plasma effect. Through the synergistic coupling of laser induction, plasma removal, and ultrasonic-assisted removal, this method achieves high-quality micro-hole formation while reducing energy input and thermal impact, effectively suppressing thermal damage and macroscopic and microscopic crack propagation, improving hole wall integrity and processing efficiency, and providing a stable and reliable process path for the precision micro-machining of transparent, hard, and brittle materials.

[0079] As per the instruction manual Figure 1 This invention provides a method for ultra-precision micro-hole multi-energy field coupling fabrication, the method comprising:

[0080] Step 1: Based on the type of hard, brittle, and transparent crystal material of the workpiece and the depth-to-diameter ratio of the micro-hole to be machined, set the upper limit of the pulse frequency and power of the pulsed laser.

[0081] The purpose of Step 1 is to improve the local coupling efficiency of the subsequent energy beam and plasma by constructing an amorphous phase or microcracks within a transparent, hard, and brittle crystal. Matching the wavelength, pulse width, frequency, and power density avoids surface burns and full-thickness through-cracks. The initial focal depth and numerical aperture are set based on the aperture and depth-to-diameter ratio, defining the final aperture lower limit and straightness boundary conditions, providing geometric and energy boundaries for subsequent layer-by-layer expansion. Focusing the laser beam on the bottom region of the micro-hole to be processed, i.e., forming a modification trajectory from bottom to top, avoids excessive scattering and obstruction of the subsequent optical path by the modified area above, and also facilitates stress release and controlled crack propagation, reducing energy attenuation and error accumulation caused by the initial modification of the upper region.

[0082] As per the instruction manual Figure 2 Specifically, step 1 includes:

[0083] Step 1.1: Determine the single-pulse energy of the laser beam focal point located inside the workpiece based on the internal modification threshold of the workpiece material.

[0084] It should be noted that the purpose of this step is to induce amorphization or microcracks inside the workpiece material. The single-pulse light flux (energy density) or peak intensity at the laser beam focal point should be slightly higher than the internal modification threshold of the workpiece material without excessive ablation, because the single-pulse energy is set based on the modification or microcrack threshold of the workpiece material.

[0085] Specifically, the spot radius is determined based on the focusing numerical aperture NA. :

[0086] (1)

[0087] In the formula: The radius of the light spot; This is the optical diffraction limit coefficient (derived from the Airy disk model, approximately equal to 1.22). Half of it is a physical constant, not an empirical number. The laser wavelength (e.g., 1064nm); To focus on numerical aperture, , where n is the refractive index of the medium (usually n≈1 in air). It is the half-angle of the maximum ray incident on the focal point of the lens.

[0088] As can be seen from formula (1), the larger the focusing numerical aperture NA, the smaller the focused spot and the higher the energy density, but the shallower the depth of focus; the smaller the focusing numerical aperture NA, the longer the focused spot and the lower the energy density. NA determines the radius of the focused spot. The smaller the laser spot size (higher NA), the more concentrated the laser-induced modification or melting zone becomes. Therefore, the minimum diameter of the hole is usually limited by the NA. For example, when the laser wavelength λ is 1064 nm, a focusing numerical aperture (NA) of 0.05-0.1 results in a spot diameter of 10-20 µm, suitable for deep hole and long focal length processing; a focusing NA of 0.2-0.3 results in a spot diameter of 4-6 µm, suitable for micropores and modified layers; and a focusing NA of 0.4-0.6 results in a spot diameter of 1-3 µm, suitable for ultra-fine internal modification.

[0089] The single-pulse flux F is:

[0090] = (2)

[0091] In the formula: For single-pulse energy, ; s is the radius of the focused laser spot; s is the area of ​​the laser focal spot, s= .

[0092] Peak intensity for:

[0093] (3)

[0094] In the formula: The pulse width is the duration of a single laser pulse (e.g., 10 ns, 10 ps, ​​200 fs). For single-pulse energy, ; The radius of the focused spot.

[0095] It should be noted that the single-pulse flux F and peak intensity It is not itself a material threshold parameter, but rather the intensity of the laser's effect at the material's focal point. However, in processing research, threshold flux is commonly used. and threshold intensity This is used to represent the critical value at which material begins to undergo modification or damage. In this application, threshold flux is used. This represents the laser ablation amorphization threshold of the processed material. It is determined by comparing the single-pulse flux F with the threshold flux. Or compare peak intensity and threshold intensity To determine whether internal material modification can be achieved. F < or < This indicates insufficient energy, meaning the material is either not modified or only undergoes linear absorption. F≈ or ≈ This indicates that the modification threshold has been reached, and amorphization or microcracks begin to appear inside the material. F > or > This indicates that entering the strong nonlinear absorption region can generate plasma, cause crack propagation, or even breakdown.

[0096] As can be seen from formulas (2) and (3), the main factor affecting the material modification threshold is pulse width. Wavelength λ and numerical aperture NA. Common methods for determining the material modification threshold include experimental and literature review methods. The experimental method involves fixing the focusing system (wavelength, NA, pulse width, frequency), gradually increasing the single-pulse energy at a depth of 50-100 μm below the material surface, and microscopically observing whether modification or scattering occurs at the focal point, recording the value at the initial appearance of modification. Through formula Calculate the internal modification threshold of the material Repeat this process multiple times and take the average to obtain the threshold range. The reference method determines the initial range by looking up tables based on existing research results, such as those attached to the instruction manual. Figure 3 , Figure 3 The threshold for internal modification of typical transparent, hard, and brittle materials using femtosecond / picosecond lasers.

[0097] Let the threshold for internal material modification be... or The laser pulse duration is femtosecond (fs) or picosecond (ps). 1-5J / or for W / The threshold values ​​differ depending on the material, such as quartz, sapphire, or lithium niobate. The laser pulse duration is in nanoseconds (ns). 5-15J / .

[0098] Taking formula (2) as an example, the energy of a single pulse is estimated. :

[0099] (4)

[0100] In actual processing, the energy density at the focal point is affected by the following factors: spot size error (focal drift, aberration), material refractive index fluctuation / scattering, optical system transmittance fluctuation (dust, film layer), pulse energy instability, and sample surface micro-tilt or refractive difference. Considering these uncertainties, if only based on… Setting the parameters often fails to stably induce modification or microcracks, resulting in discontinuous pore formation or uneven modification volume. Therefore, based on formula (4), a setting of 1.1-1.5 times is recommended. The 1.1-1.5x range is the empirically optimal window for stabilizing "amorphization or microcrack-induced" structures, providing sufficient modification while avoiding over-ablation.

[0101] Final single pulse energy for:

[0102] (5)

[0103] Step 1.2: Determine the upper limit of the pulse frequency of the pulsed laser based on the thermal diffusivity of the workpiece material, the radius of the focused spot, and the radius of the micro-hole.

[0104] Assume the thermal diffusivity of the workpiece material is Focused spot radius Micro-pore radius To avoid significant heat accumulation, the thermal diffusion length between two pulses is required. for:

[0105] (6)

[0106] In the formula: The thermal diffusion length between the two pulses; Thermal diffusivity of the material (typical order of magnitude: fused silica). Sapphire is ); The time interval between the two pulses. f is the pulse repetition frequency.

[0107] If f is higher The shorter, The smaller the size, the less time the heat can dissipate, and the greater the risk of heat accumulation.

[0108] It should be noted that the thermal diffusion length between two pulses refers to the characteristic distance that heat diffuses within the material from the time the heat is deposited by the previous pulse until the arrival of the next pulse. If this length is larger than the "heated characteristic size" (such as a portion of the focusing spot radius or the radius of a micro-orifice), the heat will have time to dissipate; otherwise, significant heat accumulation will occur.

[0109] Empirical criteria for avoiding significant heat accumulation:

[0110] (7)

[0111] In the formula: To provide a safety factor (dimensionless, usually taken as 1-2), a margin is left to avoid significant heat accumulation. The larger β is, the more conservative the criterion. The thermal characteristic size is taken as the radius of the focused spot. With the radius of the micro-hole The smaller of the (the smaller, the more heat accumulates on whose scale).

[0112] To avoid significant heat accumulation, the required length of heat diffusion between two pulses is necessary. It must at least cover the "heat-affected feature dimensions". .like < If the frequency f is reduced (or the spot size / aperture is increased, or heat dissipation is improved) until the criterion formula (7) is met.

[0113] Based on formulas (6) and (7), the upper limit of the pulse frequency of the pulsed laser is obtained. :

[0114] (8)

[0115] In the formula: The thermal diffusivity of the material; For safety factor; This refers to the dimension of the heating feature.

[0116] Furthermore, since the shielding inside the hole (referring to the combined effects of reflection, absorption, scattering, and blocking of subsequent incident laser light caused by the medium (plasma, vapor, debris particles, redeposited dust) generated and retained inside the hole during laser drilling, as well as the geometric constraints of the hole wall, resulting in weakened effective energy reaching the bottom of the hole, disturbed wavefront, leading to decreased removal rate, increased taper, and whitening / crack upward movement) is a multi-physics coupling, involving plasma generation and attenuation, vapor / debris flow, wall scattering multiple times, absorption and re-radiation, geometric blocking, thermal-fluid-optical coupling, and "pulse-to-pulse" time accumulation, it is necessary to simplify the shielding inside the hole into an empirical transmission. A coefficient T of 0-1 is used to represent the overall equivalent of the blocking and attenuation of subsequent pulses by the plasma, debris, vapor, and wall scattering generated inside the hole. There is no need to precisely solve for the plasma; only an empirical function is needed to represent "how much light actually reaches the bottom of the hole."

[0117] Plasma and debris permeability for:

[0118] (9)

[0119] In the formula: The combined transmittance coefficient of plasma and debris (dimensionless, 0-1) represents how much incident energy can penetrate the shield inside the aperture and actually reach the bottom of the aperture. =1 No shielding, Approaching zero strong shielding; γ is the empirical attenuation coefficient (dimensionless, >0), which represents "how much the transmittance decreases exponentially when the depth-to-diameter ratio increases by 1". The larger γ is, the stronger the shielding and the faster the transmittance decreases. A is the depth-to-diameter ratio (dimensionless) of a micro-hole, where A = L / D, L is the hole depth, and D is the hole diameter.

[0120] The value is related to the material, pulse width / wavelength, repetition frequency, blowing / suction, immersion, and orifice wall roughness. A common starting range is 0.03-0.12; γ will be smaller with strong blowing / immersion.

[0121] According to formula (9), when A=0 (no depth / entrance). = As A increases, The exponential decline reflects the empirical rule that "the deeper and finer the depth, the more difficult it is for light energy to reach the bottom."

[0122] Furthermore, the equivalent frequency at the bottom of the micro-pore was obtained. Combining formulas (8) and (9), we obtain the final upper limit of the pulse frequency of the pulsed laser. :

[0123] (10)

[0124] In the formula: The thermal diffusivity of the material; For safety factor; For dimensions that are subject to heat; is the transmittance coefficient.

[0125] As can be seen from formula (10), the larger the depth-to-diameter ratio (the larger A), the better. The smaller, the more permissible The lower (or the need for strong chip removal / blowing to raise T(A)).

[0126] Step 1.3: Determine the average output power of the pulsed laser based on the actual pulse repetition frequency, focal spot area, and single pulse energy.

[0127] The actual average output power under a given pulse energy and frequency is:

[0128] (11)

[0129] In the formula: P is the pulsed laser power; s is the laser focal spot area, s= f is the actual pulse repetition frequency used by the laser during processing; F is the actual single-pulse flux acting on the focal spot, i.e., the energy surface density (see Formula 2). The single pulse energy (Formula 5); These are the technical parameters of the laser equipment, usually provided by the laser manufacturer, such as 10 W, 20 W, 50 W, etc.

[0130] In one embodiment, the diameter of the micro-hole in the hard, brittle, and transparent crystal material is in the range of 0.02-1 mm, the aspect ratio of the hole is in the range of 1-20, the pulse frequency of the laser generator is in the range of 20-500 kHz, and the laser power is in the range of 10-100 W. The specific pulse frequency and power of the laser are determined according to the workpiece material and the aspect ratio of the hole, in accordance with steps 1.1-1.3.

[0131] Step 2: Inject the pulsed laser beam onto the workpiece from the selected incident surface, and position the focal point of the laser beam at the bottom of the micro-hole to be machined inside the workpiece.

[0132] The purpose of step 2 is to ensure that material removal proceeds layer by layer from the bottom of the hole to the top along the axial direction by accurately positioning the pulsed laser focus at the bottom of the workpiece. This avoids energy scattering, surface ablation, or hole collapse problems that occur when processing from the top to the bottom of the hole, thereby improving the morphological consistency and dimensional accuracy of the micro-hole and enabling material modification and / or removal in the bottom region of the micro-hole.

[0133] Specifically, on both sides of the workpiece, the following conditions are selected as the incident surface: (i) there are no opaque inclusions or coatings obstructing the light path from this side to the bottom of the hole. (ii) the surface of this side has a surface shape accuracy ≤λ / 10 (λ is the center wavelength of the laser) and a roughness ≤Ra10 nm to reduce scattering.

[0134] A Cartesian coordinate system {X,Y,Z} is established on the laser beam incident surface of the workpiece. The normal to the outer surface of the surface to be incident is defined as the positive Z direction. Two orthogonal scans are performed on the incident surface using machine vision or coaxial microscopy, and the geometric center of the intensity peak is taken as the origin O of the hole. The micro-hole axis is defined as a straight line passing through the hole center and collinear with the normal to the local tangent plane of the incident surface.

[0135] Step 3: Based on the matching relationship between the aperture size of the micro-hole to be processed and the laser spot size, set the corresponding laser beam motion trajectory and control the laser beam to move along the axial direction of the micro-hole, so that the focal point of the focused spot is successively positioned at different depth positions with a predetermined step distance, so as to form an internal modified structure extending from the bottom to the top of the micro-hole along the axial direction of the micro-hole in the vicinity of the focal point inside the material.

[0136] The purpose of step 3 is to precisely control the trajectory of the laser beam in space, allowing the laser focus point to move layer by layer within the workpiece at predetermined depth intervals, thereby forming a continuous and controllable internal modification structure within the hard, brittle, and transparent crystalline material. Step-by-step control enables energy coupling between adjacent modification zones, achieving stable continuity from the bottom to the top of the hole. The motion trajectory is executed by a CNC system to avoid hole deformation caused by focus drift. Layer-by-layer focus positioning prevents energy diffusion and ensures stable modification effects for each layer.

[0137] It should be noted that the trajectory of the laser beam refers to the trajectory of the beam direction and focal position changes achieved by a galvanometer, rotating mirror, scanning objective, or equivalent optical actuator. Internal modified structure refers to the material structure changes formed in the vicinity of the focal point, including but not limited to microcrack zones, amorphous zones, and refractive index change zones. In this application, the internal modified structure is the formation of vertical columnar microcracks or amorphous regions within the crystalline material of the workpiece. The focal vicinity within the material refers to the spatial region where the energy density at and around the focal point reaches or approaches the material modification threshold when the laser beam is focused on the interior of a transparent or translucent material. (See attached specification.) Figure 4 , Figure 4 This is a schematic diagram illustrating the formation of columnar microcrack regions in a hard, brittle, and transparent crystalline material induced by laser.

[0138] Specifically, step 3 includes:

[0139] Step 3.1: Set the motion trajectory of the laser beam. When the ratio of the aperture diameter of the micro-hole to the laser spot diameter is in the range of 1.0 to 1.5, the motion trajectory of the laser beam is a single linear trajectory along the axial direction of the micro-hole. When the ratio of the aperture diameter of the micro-hole to the laser spot diameter is greater than 1.5, the motion trajectory of the laser beam is a layered scanning trajectory that performs a coverage scan in the plane corresponding to the aperture diameter, moves upward along the axial direction of the micro-hole by a predetermined distance, and repeats the scan.

[0140] Linear trajectory triggering conditions: A single linear trajectory along the hole axis is used, with continuous focus movement to form a through-hole modified column in the hole depth direction. The hole diameter is micro-amplified by thermo-mechanical expansion and subsequent etching / cleaning. Layered scanning trajectory triggering conditions: A layer is scanned in the plane corresponding to the aperture, and then moved upward along the axis, repeating until the target depth is reached. This ensures radial coverage and energy uniformity of the aperture, avoiding overheating in the center or under-processing at the edges.

[0141] At the same time, in order to avoid in Frequent switching in the vicinity necessitates a hysteresis band: if the previous trajectory was linear, then only when... Only then does it switch to layered scanning; if the previous trajectory was a layered trajectory, then only when Only then did it switch back to linear.

[0142] Step 3.2: Control the laser beam to move along the axial direction of the micro-hole. When the laser beam’s movement trajectory is a linear trajectory, control the laser head to move continuously along the axial direction at a set speed curve to achieve continuous movement of the focal position. When the laser beam’s movement trajectory is a layered scanning trajectory, control the laser beam to complete the scan in each planar layer and then move along the axial direction by a predetermined step distance. After moving to the position, perform the next layer scan to form an internal modified structure that penetrates the depth direction of the hole by layering.

[0143] The specific process of linear trajectory is as follows:

[0144] Set linear trajectory ,in The center of the micropore Based on the velocity curve Continuous changes enable stable movement of the focal point along the axial direction.

[0145] During continuous axial focus movement, abrupt speed changes can cause instantaneous fluctuations in laser energy density. For example, sudden speed changes in the axial drive system (lead screw, servo motor, piezoelectric or voice coil platform) can generate inertial impacts, leading to focus drift or jitter. Focus shifts of tens of micrometers can alter energy distribution, causing non-circular apertures or unstable aperture diameters. Therefore, an S-shaped speed curve is used, with a smooth acceleration phase to achieve a continuous transition between speed and acceleration, resulting in smoother focus movement and more uniform energy deposition. The S-shaped speed curve is further divided into an "acceleration phase – constant acceleration phase – deceleration phase" during the acceleration and deceleration stages, ensuring continuity between speed, acceleration, and jerk. (Speed ​​curve) Limited by energy line density:

[0146] (12)

[0147] In the formula: Energy linear density per unit length (J / mm) represents the amount of energy deposited by the laser within a unit length path on the workpiece, and is an important control quantity for processing intensity; It is a single pulse energy; The pulse repetition frequency; The velocity of the laser focus along the axial direction.

[0148] Formula (12) shows the linear energy density per unit length. The energy level is determined by the pulse energy, frequency, and speed. When the speed increases, the energy per unit length decreases, and the amount of material removed decreases; when the speed decreases, the energy accumulation increases.

[0149] According to formula (12), the velocity curve is obtained. Restrictions:

[0150] (13)

[0151] In the formula: The velocity of the laser focus along the axial direction; It is a single pulse energy; The pulse repetition frequency; Set the target energy linear density value ( Based on the material absorption characteristics, wavelength, and modification threshold, this is an empirical or calibrated value representing the minimum energy required per unit length to ensure effective material removal or modification. Typical values ​​range from [specific range not provided in the original text]. ).

[0152] Formula (13) gives the upper limit of velocity, in order to ensure that the energy density is not lower than a set threshold. ,speed Cannot exceed ,like Exceeding this limit will result in insufficient energy absorption by the material, potentially leading to incomplete modification of the pore walls or poor penetration; if If the temperature is too low, local overheating or thermal cracking may occur.

[0153] Furthermore, to ensure the continuity of laser focus movement and the uniformity of energy distribution in the axial direction, a pulse interval is set. Equivalent diameter of laser spot The relationship is as follows:

[0154] (14)

[0155] In the formula: The distance between two adjacent pulses in the axial direction of the aperture (μm); The velocity of the laser focus along the axial direction of the hole (mm / s); f is the laser pulse repetition frequency (Hz or kHz). The equivalent diameter of the laser spot (μm) is determined by the current focal length and numerical aperture (NA) of the focusing optical system, and is usually taken as... The diameter of the energy distribution area (approximately 13.5%).

[0156] when At this time, the effective areas of adjacent pulses overlap by more than 70% in the axial direction, the energy field is continuously distributed, and the modification or erosion process of the hole wall material remains stable; when When energy gaps occur between adjacent pulses, it can lead to discontinuities in the modified layer inside the hole or the formation of periodic step defects on the hole wall. In this case, the pulse repetition frequency f should be increased or the axial feed rate should be decreased. This is to restore the target overlap ratio range. It should be noted that formula (10)... It is the upper limit of the pulse frequency, that is, the upper limit of thermal safety, while the pulse repetition frequency f is the actual required frequency value.

[0157] The equivalent diameter of the laser spot is determined by the optical system and the current focusing position. If Then increase f or decrease The laser head is controlled to move continuously along the axial direction at a set speed curve according to the above settings, so as to achieve continuous movement of the focal position and form an internal modification structure in the depth direction of the hole.

[0158] By using the above-mentioned linear trajectory control strategy, the laser focal point position can be continuously and smoothly moved in the axial direction, ensuring that the pulse energy is uniformly superimposed in the depth direction of the hole, thereby forming a continuous and consistent internal modification structure in the depth direction of the hole, avoiding problems such as "step-like ablation layer" or "uneven hole wall roughness" caused by energy discontinuity.

[0159] The specific process of layered scanning is as follows:

[0160] Determine the planar radius of the micro-aperture as r = D / 2, and then complete the surface coverage of the cross-section perpendicular to the micro-aperture axis according to a preset planar scanning trajectory (including but not limited to concentric rings, reciprocating grids, or helical trajectories). Set the channel spacing. and overlap rate It has low absorption rate in brittle and transparent materials, requiring energy superposition to ensure continuous modification. The preferred thermal conductivity is 60%-80%; for metallic materials, which have fast thermal conductivity, heat accumulation must be prevented, therefore its... The preferred overlap rate is 40%-60%. When the laser scans line by line in a plane, if the interval between adjacent scan lines is too large, energy gaps will appear, leading to discontinuities in the modified region. Conversely, if the interval is too small, excessive overlap of the laser spots will cause energy accumulation, overheating, and melting. Therefore, the overlap rate is crucial. This indicates how much of the area overlaps with the previous scan line is covered by the effective spot of each scan line.

[0161] Lane spacing for:

[0162] (15)

[0163] In the formula: The distance between the centers of two adjacent scan lines (μm); The equivalent diameter of the laser spot (μm); This represents the overlap rate.

[0164] Based on formulas (5), (10), and (15), the overlap rate Equivalent diameter of laser spot Set surface energy density target :

[0165] (16)

[0166] The velocity is obtained based on formula (16). :

[0167] (17)

[0168] In the formula: This refers to the planar scanning speed; f is the single pulse energy; f is the laser repetition frequency; The surface energy density of the target workpiece is given by the material threshold. (Experimental determination) and the desired modification depth k are jointly determined. k takes values ​​ranging from 1.2 to 2.0; The distance between the centers of two adjacent scan lines (μm).

[0169] Under the condition of meeting thermal safety requirements, the pulse frequency does not exceed its upper limit. Under the premise of this, substitute formula (15) into formula (17) and solve them simultaneously to obtain the pulse point spacing. :

[0170] (18)

[0171] From formula (18), it can be seen that when the single pulse energy Target surface energy density and the spacing between scanning tracks Once determined, the pulse point spacing Therefore, it is uniquely determined that it is independent of f. When At that time, the spatial overlap rate between pulses meets the process requirements, the energy distribution is continuous, and the modified region is uniform; when When this occurs, it indicates insufficient overlap between adjacent veins, resulting in energy gaps. Compensation can be achieved by increasing the surface energy density to meet overlap requirements. Increase pulse energy input density; improve overlap rate Reduce the spacing between scanning tracks Appropriately reduce single pulse energy. Alternatively, the scanning speed can be adjusted to achieve a more uniform energy distribution. The pulse spacing can be adjusted using the methods described above. The design goal is to ensure continuous energy coverage and uniform modification during the planar scanning process.

[0172] The actual required laser repetition frequency f is selected within the feasible region:

[0173] (19)

[0174] In the formula: This is the lowest repeatable frequency of the laser. This is the maximum permissible frequency of the laser; This is the upper limit of the pulse frequency of the pulsed laser (Formula 10).

[0175] in, and Hardware constraints.

[0176] Furthermore, the actual required power is determined. The actual required power can be obtained from formula (11) in step 1. Therefore, the power P calculated from the actual laser repetition frequency f determined by formula (19) should meet the average power limit. .

[0177] Under the selected value of f, the intra-layer scanning speed is obtained using formula (17). And send it to the scanner. If If the speed exceeds the upper limit of the galvanometer / platform, f can be reduced and recalculated. Conversely, if it is too slow and affects production capacity, f can be increased without touching the upper limits.

[0178] Interlayer spacing When higher uniformity is required, the preferred option is... The interlayer starting point adopts an interleaved strategy. After each layer of planar scanning is completed, a stepping motion is performed along the axis of the micro-aperture. encoder position error And the follow-up settling time A 5ms interval is used as the arrival criterion. Upon arrival, the next layer scan is triggered. To suppress layer patterns and homogenize energy distribution, a power reduction shaping layer is inserted every N layers (e.g., every 5 layers), with the shaping layer power being 70-85% of that of the regular layer.

[0179] By employing the aforementioned layered scanning trajectory control strategy, it is possible to reduce heat accumulation and interlayer undulations while ensuring axial coverage and energy uniformity, thereby obtaining a stable and consistent internal modified structure.

[0180] Taking layered scanning as an example: laser band / pulse width in picosecond / femtosecond format, with known equivalent spot diameter Focal spot radius = / 2=10 The area of ​​the focal spot s = Inter-line overlap rate , Single pulse energy Target surface energy density Select threshold The margin k=1.3.

[0181] Spacing between verification points

[0182] The overlap constraint check passed. The spot overlap rate along the scanning direction is approximately 1- / In satisfying Choose any f=200kHz, inverse kinematics plane scanning speed .

[0183] Verification of average power P: P = .

[0184] Interlayer step distance ,set up Planar coverage employs raster scanning with alternating 0° / 90° interlayer stagger angles. The outermost ring is edge-trimmed (80–90% power), and distance triggering ensures in-plane point spacing. .

[0185] Step 4: Place the plasma nozzle on the opposite side of the workpiece that receives the laser beam, so that the spray axis of the plasma nozzle is coaxial with the propagation axis of the laser beam, and the initial processing position of the sprayed plasma is aligned with the laser focal point.

[0186] The purpose of step 4 is to achieve coaxial synergy with the laser at the focal point, enabling efficient coupling of plasma energy and laser energy within the same processing volume: on the one hand, it enhances local heating and material removal, reduces the initial perforation threshold, and stabilizes the molten pool; on the other hand, it utilizes the high-speed plasma beam formed by the reverse coaxial jet to promptly remove slag, suppress burrs and resolidify, reduce the plasma's shielding and back absorption effect on the laser, shrink the heat-affected zone, and improve the straightness and surface quality of the hole, thereby improving processing efficiency and consistency.

[0187] Specifically, step 4 includes:

[0188] Step 4.1: Establish a clamping reference based on the bearing surface of the workpiece and the incident surface, install the plasma nozzle on the opposite surface of the incident surface, and adjust the position and attitude of the plasma nozzle through a position adjustment mechanism with X, Y, Z and pitch, yaw and rotation adjustment degrees of freedom, so that its spray axis is coaxial with the propagation axis of the laser beam.

[0189] It should be noted that the bearing surface of a workpiece refers to the reference plane that supports the workpiece during clamping. It is usually the side of the workpiece that is placed on the fixture, platform, or worktable, and is used to bear the workpiece's own weight, clamping force, and external reaction force.

[0190] The coaxiality of the plasma nozzle's jet axis and the laser beam's propagation axis satisfies the following: radial deviation ≤ 0.05 mm and / or angular deviation ≤ 0.1° over a 100 mm axial length.

[0191] First, establish a clamping datum using the workpiece's bearing surface and incident surface, confirming that the flatness of the bearing surface is ≤5μm / 100mm (i.e., within a measured or specified 100mm range, the height difference between the highest and lowest points on this plane (or straight line) is ≤5μm). Then, install the plasma nozzle on the opposite side of the workpiece's incident surface, and make initial adjustments using the posture adjustment mechanism to align the nozzle's jet axis with the laser propagation direction. (See attached instruction manual.) Figure 5 , Figure 5 The arrows in the diagram indicate the machining direction of the micro-holes, as well as the direction of plasma nozzle ejection and laser movement.

[0192] Then, the control system activates the collimation teaching light source, causing the low-power laser beam to propagate along the main optical path. Step 4.1 involves setting up a coaxial detection component, which includes a coaxial imaging camera and / or a collimation teaching light source and a coaxial target. The imaging camera of the coaxial detection component observes the coincidence of the nozzle axis and the laser pointer beam at the same target center, obtaining the center point of the laser optical axis on the target plane. After the laser optical axis calibration is completed, under the command of the control system, without igniting plasma discharge, the working gas pressure of the plasma nozzle is set to a low-pressure microfluidic state of 0.02-0.05 MPa. At this time, the nozzle ejects a small amount of tracer gas or weak glow, forming a jet column profile that can be imaged by the camera. This gas flow is only used to visualize the nozzle axis and assist in coaxial adjustment.

[0193] The control system invokes the image processing module to perform edge detection and centroid fitting on the nozzle spray image captured by the imaging camera. The system automatically extracts the centerline of the nozzle spray and calculates its deviation from the target center. Based on the center deviation calculation result, the control system issues adjustment commands to automatically fine-tune the X, Y, pitch, and yaw degrees of freedom of the pose adjustment mechanism. When the automatic adjustment function is not enabled, the operator manually fine-tunes according to the interface prompts. After adjustment, the system automatically acquires the centroid coordinates of three points z=0, 50, and 100mm, fits the spray centerline, and calculates the radial deviation ≤0.05mm / 100mm and the angular deviation ≤0.1°. If the tolerances are not met, the system prompts for readjustment.

[0194] Step 4.2: Determine the spatial coordinates of the laser focus on the workpiece using a distance sensor and a confocal displacement sensor, and control the relative displacement between the workpiece and the plasma nozzle so that the initial processing position of the plasma jet column coincides with the spatial coordinates.

[0195] First, the control system calls the confocal displacement sensor to scan the workpiece incident surface and automatically locates the spatial coordinates of the laser focus A. The CNC motion platform moves the workpiece under the command of the control system, bringing the initial machining point of the spray column to the target position. The spatial coordinates of the initial processing position coincide with those of laser focus A. The control system monitors the position error in real time to ensure that the radial deviation of the initial processing position relative to the laser focus is ≤ ±20μm and / or the axial deviation is ≤ ±30μm.

[0196] Once positioning is complete, the control system executes the ignition sequence: first, a stable airflow is established; when the laser trigger signal (t_L=0ms) is issued, the system starts timing; at t_I (ignition time) (t_I= t_L+Δt, where Δt is the delay time, ranging from 0-5ms), a plasma ignition command is issued to ensure that the center line of the plasma column passes exactly through the laser focus position.

[0197] The imaging camera continuously acquires images of the focal marker and the initial plasma core, while the visual computing module extracts the centroid of the focal marker in real time. and the center of mass of the initial plasma core .like (For example =15μm), indicating that the two energy beams are not yet completely coaxial. The control system then issues a micro-displacement compensation command, driving the CNC platform to make fine adjustments according to the error direction until the center line of the jet coincides with the laser focus.

[0198] It should be noted that the focal marker is used to indicate the location of the laser focal point (a small bright spot formed by a low-power laser or teaching beam). The centroid C_f of the focal marker is the spatial projection of the laser energy focal point. The initial plasma core is used to indicate the center of the luminous region formed in the image when the plasma is just ignited. The centroid of the initial plasma core is... It is the projected position of the energy center of the plasma jet in space.

[0199] Step 5: During the processing, the processing position of the plasma and the processing position of the laser focus are moved axially in sync along the processing direction so that the internal modified area induced by the laser is removed synchronously during formation, thereby forming a micro-hole in the workpiece. Axial ultrasonic vibration is then applied to the hard, brittle and transparent material workpiece through an axial ultrasonic vibration generator to remove the debris generated during the plasma processing. This allows the laser energy, plasma energy and ultrasonic vibration energy to work synergistically within the same processing volume to complete the micro-hole processing.

[0200] The purpose of step 5 is to achieve the spatiotemporal synergy of three energy fields—laser, plasma, and ultrasonic vibration—during the processing, so that the modified regions inside the material induced by the laser are efficiently removed by the plasma at the moment of formation. At the same time, the axial ultrasonic vibration promotes the timely discharge of molten material and debris, reduces heat accumulation and stress concentration, thereby lowering the micropore forming threshold of hard, brittle, and transparent materials, suppressing cracks, edge chipping, and resolidification defects, ensuring the continuity of the pores and the surface finish, and achieving efficient, stable, and consistent micropore processing.

[0201] Specifically, step 5 includes:

[0202] Step 5.1: Using a CNC motion platform, drive the laser and plasma nozzle to move synchronously along the processing direction, so that the processing position of the plasma jet column and the processing position of the laser focus are spatially overlapped and advance synchronously in the same direction. Thus, while the laser induces the formation of amorphous regions or microcrack regions inside the material, the plasma action achieves synchronous online removal of these regions.

[0203] In step 5.1, the CNC motion platform, as the core actuator, is responsible for driving the laser assembly and the plasma jetting device to move synchronously axially along the set processing path. The purpose is to ensure that the effective position of the plasma jet column and the effective position of the laser focus are precisely aligned in space, and that they advance synchronously in the same direction. The CNC motion platform employs three-axis or five-axis linkage (three linear axes X / Y / Z, and two rotary axes θ and φ, rotating around the X or Y and Z directions respectively), with a minimum resolution ≤0.1µm and a repeatability ≤±0.5µm.

[0204] The CNC motion platform uses a linkage control algorithm to keep the spatial alignment error between the laser focusing spot center and the plasma jet center within ±2µm. The control system monitors the displacement signal of the laser focus and the plasma jet position feedback signal in real time, and performs dynamic compensation based on the deviation data to ensure that the two always move in the same direction and at the same speed during the processing.

[0205] The control system sets the time delay Δt between the laser pulse trigger time and the plasma ignition signal, preferably within the range of 0.2-2.0 ms. This delay ensures that the laser first induces the formation of an amorphous region or microcrack region inside the transparent, hard, and brittle material, and then the plasma jet removes this region synchronously online in a very short time, thereby achieving an integrated and synergistic processing effect of laser induction and plasma removal.

[0206] The laser's operating wavelength is set to 1030 nm, and the single-pulse energy output is controlled within the range of 2-30 µJ, with a pulse width of 200 fs to 10 ps and a repetition frequency of 100 kHz to 1 MHz. The feed speed of the motion platform is controlled within the range of 0.2-3 mm / s, ensuring a pulse overlap rate of no less than 80%. The distance between the plasma nozzle and the workpiece surface is maintained within the range of 0.8-1.2 mm. The working gas is high-purity argon or helium, with a flow rate of 0.2-1.0 L / min and a jet power of 100-400 W.

[0207] During processing, the instantaneous high energy density generated by the laser pulse within the material induces amorphization or microcrack formation in micro-regions. Simultaneously, the plasma jet column, through high-temperature scouring and high-speed airflow, promptly removes the molten material and microcrack debris from these areas, achieving synchronous removal of the target region. This combined effect effectively prevents crack propagation caused by thermal accumulation and improves the smoothness and geometric accuracy of the hole walls.

[0208] Step 5.2: Set the ultrasonic vibration generator on the same side as the laser incident surface or on the side where the plasma nozzle is located. The ultrasonic vibration generator applies axial ultrasonic vibration to the hard, brittle and transparent material workpiece along the normal direction of the workpiece. The ultrasonic vibration will vibrate the molten material and debris in the processing area along the channel direction to complete the processing of the micro-hole and optimize the hole wall quality.

[0209] In step 5.2, the ultrasonic vibration generator is arranged as an auxiliary unit on the same side as the laser incident surface or on the side where the plasma nozzle is located. Its main function is to apply axial ultrasonic vibration to the hard, brittle, and transparent material along the normal direction of the workpiece to promote the efficient discharge of molten material and debris in the processing zone and improve the forming quality of the micropore walls.

[0210] The ultrasonic vibration generator consists of three parts: a piezoelectric transducer, an amplitude transformer, and a coupling pad. The device generates ultrasonic vibrations of 10-35 kHz via a high-frequency drive signal, which are amplified by the amplitude transformer and transmitted along the workpiece normal to the hole machining area. The vibration direction is aligned with the micro-hole axis, ensuring that the vibration energy is concentrated within the machined area of ​​the hole.

[0211] To achieve high-precision and high-stability multi-energy field coupling processing of micropores in hard and brittle crystalline materials, the control system precisely sets and dynamically adjusts the ultrasonic frequency and vibration parameters. Specifically, the operating frequency of the ultrasonic system is selected according to the characteristics of the material being processed: when processing hard and brittle materials, the frequency is set in the range of 10-35 kHz; when processing high-hardness crystalline materials such as sapphire, aluminum nitride, and gallium oxide, the frequency is set in the range of 60-80 kHz. By optimizing frequency matching, the coupling efficiency of acoustic energy in the micro-area can be effectively improved, energy loss can be reduced, and the stable propagation of crack-induced zones can be promoted. The vibration amplitude is controlled in the range of 0.1-1.5 μm, preferably 1.0 μm. A smaller amplitude can achieve higher surface finish, while a moderate amplitude can enhance the material removal rate, achieving a balance between processing efficiency and quality. In addition, the system works in conjunction with a built-in temperature sensing module and an online optical emission spectroscopy (OES) monitoring module to monitor the temperature and plasma emission characteristics of the processing area in real time. When the system detects abnormal temperature or fluctuations in the emitted signal intensity exceeding a set threshold, the control unit automatically adjusts the duty cycle of the ultrasonic drive signal, causing the ultrasonic output to operate in a 0.2-1.0s on / 0.1-0.5s off cycle. This dynamic modulation strategy effectively avoids the propagation of microcracks or localized structural damage caused by excessive ultrasonic vibration, thereby ensuring the integrity and dimensional accuracy of the processed area. Through this control strategy, multi-energy field coupling optimization of laser-induced and ultrasonic vibration is achieved, enabling the micro-hole processing of hard and brittle crystalline materials to maintain high efficiency while reducing the risk of structural damage and improving the surface quality and micro-hole morphology consistency.

[0212] When ultrasonic vibration is applied to the workpiece, periodic sound pressure fluctuations are generated inside the duct. These fluctuations effectively reduce the adhesion between the duct wall and the debris, and promote the expulsion of molten material along the duct axis. Simultaneously, the plasma nozzle maintains a low-pressure auxiliary airflow (0.05-0.15 L / min) to continuously pump out debris along the duct direction, allowing the debris to be smoothly discharged under the combined action of acoustic flow and airflow.

[0213] By combining ultrasonic vibration and plasma, the temperature distribution inside the hole is more uniform, and the residual slag on the hole wall is significantly reduced. The roundness error of the processed hole is kept to within ±3µm, and the surface roughness Ra of the hole wall is controlled within the range of 0.25-0.35µm, which is better than the results of laser or plasma processing alone.

[0214] Step 5 involves achieving synchronous axial movement of the laser and plasma under the coordinated control of a CNC motion platform, supplemented by periodic ultrasonic vibration. This invention enables the efficient processing of high-precision micro-holes in hard, brittle, and transparent materials. The entire process achieves synchronous online removal of the laser-induced zone, directional oscillation of the molten material, and self-polishing modification of the hole walls. Ultimately, the resulting micro-holes exhibit high dimensional accuracy, smooth walls, and are free of microcracks and residue buildup, meeting the processing requirements of optical components and high-end packaging substrates.

[0215] Step 6: Repeat steps 1-5 until all the predetermined micro-holes on the workpiece surface are machined.

[0216] The purpose of step 6 is to achieve batch processing of hole arrays / multi-point locations by utilizing the programmable displacement and repeatability accuracy of the worktable, ensuring the alignment accuracy of hole spacing, array phase, and layout. The parameter sets from steps 1-5 are reused in a predetermined order to reduce heat buildup and stress accumulation, avoiding mutual interference between adjacent holes (such as crack connections or optical crosstalk). This improves yield and consistency, ensuring that hole diameter distribution, taper, perpendicularity, and optical transmittance meet design specifications and inspection procedures.

[0217] In this step, the CNC motion control system executes steps 1 to 5 sequentially on all the predetermined micro-holes on the workpiece surface according to the preset hole distribution data, until the machining task of the entire hole array is completed. This step involves key technical aspects such as hole planning, path optimization, process reuse, thermal management, and quality consistency control.

[0218] Specifically, the control system first automatically generates the hole machining path based on the hole array coordinate data (including hole diameter, hole spacing, array type, and partition number) input from the design drawings or CAD model. The center coordinates of each micro-hole are defined by the CNC system in the global coordinate system. Where i = 1, 2, ..., n, and n is the total number of predetermined holes. The system stores the hole location information in the processing operation list to ensure that the processing sequence is traceable and reproducible.

[0219] The control system employs a "shortest path priority + thermal field equalization" strategy to automatically optimize the movement trajectory between holes. For large-area hole arrays, the system divides the processing area into several sub-blocks (such as 10×10 or 20×20 array units) and uses a serpentine scanning path or reciprocating path mode for processing. This planning method effectively reduces non-processing idle travel time, ensures uniform heat distribution in the processing area, and prevents material deformation or optical performance degradation due to local heat accumulation. Each time a hole position is switched, the control system uses a laser confocal displacement sensor to detect the workpiece surface height difference in real time and automatically adjusts the Z-axis focal point position to ensure that the laser focal point and the plasma nozzle outlet are spatially aligned. The system corrects the focal length error based on the detection results, with an accuracy better than ±1µm.

[0220] As the system moves from one hole to the next, the control system automatically retrieves the processing parameters of the previous hole (including laser energy, pulse frequency, plasma power, ultrasonic amplitude, etc.) and adaptively fine-tunes the power or speed based on real-time sensor feedback to ensure processing consistency. If changes in material thickness or transmittance are detected, the system automatically adjusts the focal depth and pulse energy to adapt to the optical characteristics of different areas. After each hole is processed, the system automatically collects the OES signal peak value, temperature data, and hole wall reflectivity information, and compares them with preset thresholds to determine whether the processing meets the standards. When insufficient hole depth or excessive hole wall roughness is detected, the system automatically triggers the "repeat processing" subroutine to perform a second laser and plasma combined finishing on the abnormal hole. The number of repeat processing operations generally does not exceed 3 times, and the power of each finishing operation is reduced by 10%–30% compared to the main processing power to prevent over-removal.

[0221] After completing the processing of each block (e.g., 100 holes), the control system automatically pauses processing for 0.5-2.0 seconds and activates the auxiliary gas cooling or air circulation system to reduce the temperature rise of the workpiece surface and prevent thermal stress concentration. The system monitors the workpiece surface temperature in real time through a built-in infrared temperature measurement module. When the temperature exceeds the preset upper limit (e.g., 80°C), it automatically reduces the laser duty cycle or temporarily switches the processing area until the temperature returns to normal.

[0222] By repeatedly executing steps 1-5 of the automatic cyclic processing control, this invention can achieve consistent, high-precision, and high-efficiency processing of multi-hole arrays on workpiece surfaces. Processing accuracy is stable, with automatic focusing and energy compensation mechanisms for each hole ensuring focal point stability with an error of less than ±1µm; thermal impact is minimized, with block-type processing and intermittent cooling reducing heat accumulation and preventing material deformation; the system is highly intelligent, automatically identifying hole positions, correcting parameters, and recording data to achieve closed-loop control throughout the entire process; and processing efficiency is high, increasing by approximately 40-60% compared to traditional single-hole manual positioning methods.

[0223] Step 7: After processing, use a cleaning medium to clean the micro-holes of the processed workpiece to remove surface residues.

[0224] The purpose of step 7 is to remove residual wear debris, particles, redeposited layers, and chemical residues from the sidewalls and surfaces, restoring / maintaining optical transparency and surface energy, and avoiding contamination risks during subsequent encapsulation, coating, or bonding. It also reduces microcrack initiation sources and burrs at the aperture, improving the mechanical strength and fatigue life of the device. Furthermore, it provides a clean interface for online or offline dimensional / morphological / optical inspection (such as microscopy, interferometry, profilometry, and roughness measurements), ensuring measurement repeatability and data reliability.

[0225] Specifically, after completing the laser, plasma, and ultrasonic composite processing, the system control module instructs the cleaning unit to clean the processed workpiece to thoroughly remove molten material, powder, plasma reaction residue, and any remaining processing byproducts from the micro-holes and their surrounding surfaces, thereby ensuring the smoothness, light transmittance, and surface cleanliness of the hole walls.

[0226] The cleaning unit includes a cleaning fluid supply system, a spraying and immersion device, an ultrasonic cleaning module, a temperature control system, and a drying module. The cleaning fluid supply system includes a cleaning fluid storage tank, a filtration unit, a delivery pump, and a flow controller. The filtration accuracy of the filtration unit is preferably not less than 0.2µm to prevent secondary contamination of the workpiece surface by particles. The flow controller is used to precisely regulate the cleaning fluid flow rate, maintaining it within the range of 0.1-0.5L / min. The cleaning device can adopt a spraying or immersion structure depending on the workpiece shape. For planar sample-type workpieces, the system uses a multi-nozzle array structure; for larger lenses or windows, an immersion tank structure with a circulating flow channel is used. The nozzle outlet angle is preferably 30°-60°, and the spray distance is controlled at 20-50mm to ensure that the fluid can effectively enter the micropores.

[0227] To enhance particle stripping and bubble desorption from the microporous inner walls, the cleaning device is equipped with an ultrasonic transducer array. The transducers operate at a frequency range of 40-120 kHz, with a sound power density of 0.5-2.5 W / cm², and the working fluid temperature is controlled within the range of 25-45°C. This module can operate synchronously with the cleaning fluid flow or independently with pulse excitation to achieve periodic enhancement of the cavitation effect. After cleaning, the workpiece undergoes low-temperature drying in a constant-temperature hot air drying oven. The drying temperature is controlled at 50-70°C for 10-20 minutes to prevent residual liquid from evaporating and causing watermarks. For optical-grade parts, further nitrogen purging or vacuum drying (-0.08 MPa, for 15 minutes) can be used to ensure no atomized residue on the surface.

[0228] Depending on the workpiece material characteristics and the type of processing residue, the cleaning medium can be deionized water, a weakly alkaline aqueous solution, or an organic solvent. Deionized water is mainly used to remove molten powder, particles, and plasma oxides; its conductivity is not higher than 0.2 µS / cm, and the temperature is controlled at 20-30 °C. It is suitable for inorganic transparent materials such as quartz and sapphire. A weakly alkaline aqueous solution uses ammonia water with a mass fraction of 1–3% (…). )or The solution can effectively remove minor organic matter and processing deposits from the surface. For workpieces containing organic binders, anti-reflective films, or gel-like contaminants, anhydrous ethanol, isopropanol, or acetone can be used as auxiliary cleaning media.

[0229] After cleaning, the workpiece is inspected for residues inside the pores using a microscope and a confocal optical system. If the intensity of the reflected signal from the detected particles exceeds a set threshold, a secondary ultrasonic cleaning process is automatically triggered until the detection signal meets the cleanliness standard. After the above cleaning process, the size of the residual particles inside the micropores and at the pore opening is no greater than 0.5 µm, and the residual density is less than 100 particles / cm². The optical transmittance of the pore wall surface is restored to more than 95% of the original material, with no visible whitening, haze, or liquid traces. Scanning electron microscopy (SEM) shows that the pore wall surface is smooth and free of secondary adhesion layers. Energy dispersive spectroscopy (EDS) analysis verifies that no metal or organic contaminants were introduced after cleaning. Through the above cleaning steps, this invention achieves high-cleanliness cleaning of the processed micropores, avoiding problems such as pore opening obstruction, decreased transmittance, and subsequent coating contamination caused by residues. This step, together with the aforementioned laser, plasma, and ultrasonic collaborative processing, forms a complete process closed loop, ensuring the geometric accuracy, surface quality, and functional performance of the processed pores.

[0230] This invention also provides a multi-field coupling processing system for micropores in hard and brittle crystalline materials, comprising:

[0231] The laser processing module includes a laser parameter setting module and a laser incident and focusing positioning module;

[0232] The laser parameter setting module is used to set the upper limit of the pulse frequency and power of the pulsed laser according to the type of hard, brittle, and transparent crystal material of the workpiece and the depth-to-diameter ratio of the micro-hole to be processed.

[0233] The laser incident and focusing positioning module is used to incident a pulsed laser beam onto the workpiece from the selected incident surface and to precisely position the focal point of the laser beam at the bottom position of the micro-hole to be machined inside the workpiece.

[0234] The laser motion control module is used to set the motion trajectory of the laser beam according to the matching relationship between the aperture size of the micro-hole to be processed and the laser spot size, and to control the laser beam to move along the axial direction of the micro-hole, so that the focal spot of the focused spot is successively positioned at different depth positions with a predetermined step distance, so as to form an internal modified structure extending from the bottom to the top of the hole along the hole axis inside the material.

[0235] The plasma processing module includes a plasma nozzle disposed on the opposite side of the incident surface of the workpiece. The spray axis of the nozzle is coaxial with the propagation axis of the laser beam, and the initial processing position of the sprayed plasma corresponds to the laser focus position. It is used to move axially synchronously with the laser focus during the processing to remove the internal modification region formed by laser induction, thereby forming a micro-hole in the workpiece.

[0236] The ultrasonic vibration module includes an axial ultrasonic vibration generator, which is used to apply axial ultrasonic vibration to a hard, brittle, transparent crystalline material workpiece during processing to remove debris generated during plasma processing. This allows laser energy, plasma energy, and ultrasonic vibration energy to work synergistically within the same processing volume to complete the micro-hole processing.

[0237] The multi-hole automatic control module is electrically connected to the laser processing module, plasma processing module and ultrasonic vibration module to realize the repeated processing and automatic control of multi-hole positions until the processing of all predetermined micro-holes on the workpiece surface is completed.

[0238] The cleaning module is used to introduce cleaning media into the workpiece surface and the formed micro-holes after processing to remove residual debris and impurities.

[0239] This invention discloses an ultra-precision micro-hole multi-energy field coupled processing method and system. By synergistically coupling three energy fields—laser, plasma, and ultrasonic vibration—it achieves efficient, low-damage, and high-precision micro-hole processing of hard, brittle, and transparent crystalline materials. Based on the laser ablation threshold and amorphization threshold of hard, brittle, and transparent materials, by setting the upper limit of laser pulse frequency and power, the incident energy is stably positioned within the internal modification energy window of the material rather than the surface melting range, ensuring that the laser only forms a controllable modified structure in the vicinity of the hole bottom. Simultaneously, a plasma jet, coaxial and synchronously following the laser, instantly removes the modified area, effectively suppressing the heat-affected zone and hole taper. Furthermore, combined with the chip removal and stress reduction effects of axial ultrasonic vibration, the chip flow during processing is significantly improved, avoiding blockage and microcrack accumulation. Under this multi-energy field synergy, low-damage processing, high wall quality, and hole diameter consistency of high aspect ratio micro-holes are achieved, while reducing the high energy and processing cost required for plasma processing alone. This method is applicable to the precision manufacturing of micro-holes in hard, brittle, and transparent crystalline materials such as sapphire, quartz, calcium fluoride, and diamond, and is particularly suitable for the high-quality microstructure processing needs in fields such as optical devices, precision electronics, and aerospace components.

[0240] The above descriptions are merely embodiments of this application, and common knowledge regarding specific structures and characteristics in the solutions is not described in detail here. It will be apparent to those skilled in the art that this application is not limited to the details of the above exemplary embodiments, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for ultra-precision micro-hole multi-energy field coupling fabrication, characterized in that, The method includes: Step 1: Based on the type of hard, brittle, and transparent crystalline material of the workpiece and the depth-to-diameter ratio of the micro-hole to be machined, set the upper limit of the pulse frequency and power of the pulsed laser. Step 2: Inject the pulsed laser beam onto the workpiece from the selected incident surface, and position the focal point of the laser beam at the bottom of the micro-hole to be machined inside the workpiece; Step 3: Based on the matching relationship between the aperture size of the micro-hole to be processed and the laser spot size, set the corresponding laser beam motion trajectory and control the laser beam to move along the axial direction of the micro-hole, so that the focal point of the focused spot is successively positioned at different depth positions with a predetermined step distance, so as to form an internal modified structure extending from the bottom to the top of the micro-hole along the axial direction of the micro-hole in the vicinity of the focal point inside the material. Step 4: Place the plasma nozzle on the opposite side of the workpiece that receives the laser beam, so that the spray axis of the plasma nozzle is coaxial with the propagation axis of the laser beam, and the initial processing position of the sprayed plasma is aligned with the laser focus. Step 5: During the processing, the processing position of the plasma and the processing position of the laser focus are moved axially in sync along the processing direction so that the internal modified area induced by the laser is removed synchronously during formation, thereby forming a micro-hole in the workpiece. Axial ultrasonic vibration is then applied to the hard, brittle and transparent material workpiece through an axial ultrasonic vibration generator to remove the debris generated during the plasma processing. This allows the laser energy, plasma energy and ultrasonic vibration energy to work synergistically within the same processing volume to complete the micro-hole processing. Step 6: Repeat steps 1-5 until all the predetermined micro-holes on the workpiece surface have been machined; Step 7: After processing, use a cleaning medium to clean the micro-holes of the processed workpiece to remove surface residues.

2. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 1, characterized in that, Step 1 includes: Step 1.1: Determine the single-pulse energy of the laser beam focal point located inside the workpiece based on the internal modification threshold of the workpiece material; Single pulse energy for: ； In the formula: For margin; Threshold flux; This represents the area of ​​the laser focal spot. The radius of the focused spot; Step 1.2: Determine the upper limit of the pulse frequency of the pulsed laser based on the thermal diffusivity of the workpiece material, the radius of the focused spot, and the radius of the micro-hole; Upper limit of pulse frequency of pulsed laser : ； In the formula: The thermal diffusivity of the material; For safety factor; For dimensions that are subject to heat; Transmittance coefficient; Step 1.3: Determine the average output power of the pulsed laser based on the actual pulse repetition frequency, focal spot area, and single pulse energy; The actual average output power under constant pulse energy and frequency is: ； In the formula: P is the pulsed laser power; s is the laser focal spot area, s= f represents the actual pulse repetition frequency used by the laser during processing; Threshold flux; It is a single pulse energy.

3. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 1, characterized in that, Step 3 includes: Step 3.1: Set the motion trajectory of the laser beam. When the ratio of the aperture of the micro-hole to the diameter of the laser spot is in the range of 1.0 to 1.5, the motion trajectory of the laser beam is a single linear trajectory along the axial direction of the micro-hole. When the ratio of the aperture of the micro-hole to the diameter of the laser spot is greater than 1.5, the motion trajectory of the laser beam is a layered scanning trajectory that performs a covering scan in the plane corresponding to the aperture, moves upward along the axial direction of the micro-hole by a predetermined distance, and repeats the scan. Step 3.2: Control the laser beam to move along the axial direction of the micro-hole. When the laser beam’s movement trajectory is a linear trajectory, control the laser head to move continuously along the axial direction at a set speed curve to achieve continuous movement of the focal position. When the laser beam’s movement trajectory is a layered scanning trajectory, control the laser beam to complete the scan in each planar layer and then move along the axial direction by a predetermined step distance. After moving to the position, perform the next layer scan to form an internal modified structure that penetrates the depth direction of the hole by layering.

4. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 3, characterized in that, In step 3.2, the axial velocity of the laser focus using a linear trajectory is: ； In the formula: The velocity of the laser focus along the axial direction; It is a single pulse energy; The pulse repetition frequency; Set a value for the target energy linear density; interpulse interval Equivalent diameter of laser spot Relationship satisfaction .

5. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 3, characterized in that, In step 3.2, the laser focus movement speed using the layered scanning trajectory is: ； In the formula: This refers to the planar scanning speed; f is the single pulse energy; f is the laser repetition frequency; The surface energy density of the target workpiece; The distance between the centers of two adjacent scan lines; Pulse pitch satisfy .

6. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 1, characterized in that, Step 4 includes: Step 4.1: Establish a clamping reference based on the bearing surface of the workpiece and the incident surface, install the plasma nozzle on the opposite surface of the incident surface, and adjust the position and attitude of the plasma nozzle through a position adjustment mechanism with X, Y, Z and pitch, yaw and rotation adjustment degrees of freedom, so that its jet axis is coaxial with the propagation axis of the laser beam. Step 4.2: Determine the spatial coordinates of the laser focus on the workpiece using a distance sensor and a confocal displacement sensor, and control the relative displacement between the workpiece and the plasma nozzle so that the initial processing position of the plasma jet column coincides with the spatial coordinates.

7. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 6, characterized in that, In step 4.1, the coaxiality of the plasma nozzle's jet axis and the laser beam's propagation axis satisfies the following: radial deviation ≤ 0.05 mm and / or angular deviation ≤ 0.1° over a 100 mm axial length.

8. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 1, characterized in that, Step 5 includes: Step 5.1: Using a CNC motion platform, drive the laser and plasma nozzle to move synchronously along the processing direction, so that the processing position of the plasma jet column and the processing position of the laser focus are spatially overlapped and advance synchronously in the same direction. Thus, while the laser induces the formation of amorphous regions or microcrack regions inside the material, the plasma action achieves synchronous online removal of these regions. Step 5.2: Set the ultrasonic vibration generator on the same side as the laser incident surface or on the side where the plasma nozzle is located. The ultrasonic vibration generator applies axial ultrasonic vibration to the hard, brittle and transparent material workpiece along the normal direction of the workpiece. The ultrasonic vibration will vibrate the molten material and debris in the processing area along the channel direction to complete the processing of the micro-hole and optimize the hole wall quality.

9. The ultra-precision micro-hole multi-energy field coupling processing method according to claim 1, characterized in that, In step 7, the cleaning medium includes one of deionized water, a weakly alkaline aqueous solution, or an organic solvent.

10. A multi-energy field coupling machining system for ultra-precision micro-holes, characterized in that, include: The laser processing module includes a laser parameter setting module and a laser incident and focusing positioning module; The laser parameter setting module is used to set the upper limit of the pulse frequency and power of the pulsed laser according to the type of hard, brittle, and transparent crystal material of the workpiece and the depth-to-diameter ratio of the micro-hole to be processed. The laser incident and focusing positioning module is used to incident a pulsed laser beam onto the workpiece from the selected incident surface and to precisely position the focal point of the laser beam at the bottom position of the micro-hole to be machined inside the workpiece. The laser motion control module is used to set the motion trajectory of the laser beam according to the matching relationship between the aperture size of the micro-hole to be processed and the laser spot size, and to control the laser beam to move along the axial direction of the micro-hole, so that the focal spot of the focused spot is successively positioned at different depth positions with a predetermined step distance, so as to form an internal modified structure extending from the bottom to the top of the hole along the hole axis inside the material. The plasma processing module includes a plasma nozzle disposed on the opposite side of the incident surface of the workpiece. The spray axis of the nozzle is coaxial with the propagation axis of the laser beam, and the initial processing position of the sprayed plasma corresponds to the laser focus position. It is used to move axially synchronously with the laser focus during the processing to remove the internal modification region formed by laser induction, thereby forming a micro-hole in the workpiece. The ultrasonic vibration module includes an axial ultrasonic vibration generator, which is used to apply axial ultrasonic vibration to a hard, brittle, transparent crystalline material workpiece during processing to remove debris generated during plasma processing. This allows laser energy, plasma energy, and ultrasonic vibration energy to work synergistically within the same processing volume to complete the micro-hole processing. The multi-hole automatic control module is electrically connected to the laser processing module, plasma processing module and ultrasonic vibration module to realize the repeated processing and automatic control of multi-hole positions until the processing of all predetermined micro-holes on the workpiece surface is completed. The cleaning module is used to introduce cleaning media into the workpiece surface and the formed micro-holes after processing to remove residual debris and impurities.

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