Multi-energy-field auxiliary laser drilling method and device for silicon carbide micropores with large depth-diameter ratio

Abstract

The invention provides a multi-energy-field auxiliary laser drilling method and device for a silicon carbide micropore with the large depth-diameter ratio, and relates to the technical field of hard and brittle material precision machining.The multi-energy-field auxiliary laser drilling method for the silicon carbide micropore with the large depth-diameter ratio comprises the following steps that a silicon carbide workpiece is ablated layer by layer through an ultrafast laser beam to form the micropore; and in the layer-by-layer ablation process, the workpiece or the ultrafast laser beam generates relative high-frequency micro-amplitude ultrasonic vibration in the axial direction of the micropore, and the low-temperature high-speed air flow is coaxially guided to an ablation point of the ultrafast laser beam so as to remove ablation products and cool the ablation point and the adjacent area of the ablation point. Through organic combination and synergistic effect of ultrafast laser ablation, ultrasonic vibration in the axial direction of a drill hole and coaxial low-temperature high-speed airflow, the problems that in the prior art, due to unsmooth chip removal of ablation products and the remarkable heat effect, the machining depth is limited, the hole wall quality is poor, and the machining efficiency is low are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precision machining of hard and brittle materials, and particularly relates to a multi-energy field assisted laser drilling method and device for silicon carbide micro-holes with a large depth-diameter ratio. BACKGROUND

[0002] Silicon carbide (SiC) has become an indispensable key material in the forefront fields of semiconductors, aerospace, new energy and national defense industry due to its excellent properties such as high hardness, high thermal conductivity, low thermal expansion coefficient and excellent chemical stability. However, it is precisely these excellent properties, especially its ultra-high hardness (Mohs hardness 9.5) and high brittleness, which make it extremely challenging to precisely form and process, especially to process high-precision micro-holes. At present, with the continuous improvement of device integration and performance requirements, the demand for processing micro-holes with a depth-diameter ratio (ratio of hole depth to hole diameter) greater than 5:1, even more than 10:1 on thick-layer silicon carbide substrates is increasingly urgent.

[0003] Traditional mechanical drilling methods, such as using polycrystalline diamond (PCD) drills for drilling, are one of the conventional means for processing silicon carbide. However, when faced with the processing of micro-holes with a large depth-diameter ratio, the PCD drill will produce severe wear during continuous friction with the ultra-hard silicon carbide, and the tool life is extremely short. In deep hole processing, it is extremely difficult to remove chips, and the clogging of chips can easily lead to a sharp increase in drilling torque, which can easily cause drill breakage, causing the tool to be stuck in the expensive workpiece, resulting in the double scrap of the workpiece and the tool.

[0004] Laser processing fundamentally avoids the problem of tool wear and becomes an effective way to process hard and brittle materials such as silicon carbide. However, using conventional single laser processing methods in the processing of micro-holes with a large depth-diameter ratio also faces insurmountable bottlenecks. The core problem is that as the processing depth increases, the molten material, gasified material and plasma produced by laser ablation are difficult to effectively remove outside the hole. These ablation products will form a shielding effect in the hole, absorb and scatter the subsequent laser energy, resulting in a sharp decrease in the laser energy density acting on the hole bottom, and the processing efficiency and capacity decrease sharply with the increase of the depth. In addition, the ablation products (especially the slag) are easy to re-solidify and adhere to the hole wall and hole bottom after the temperature decreases, forming a hard recast layer and oxides (such as silicon dioxide), which not only seriously affects the quality of the hole wall, but also directly blocks the processing channel, ultimately leading to the premature termination of processing, thereby strictly limiting the achievable processing depth and depth-diameter ratio.

[0005] Therefore, it is necessary to improve the existing laser drilling technology of silicon carbide to overcome the defects of the prior art. SUMMARY

[0006] To overcome the problems in the related art, one of the purposes of the present application is to provide a silicon carbide large-depth-ratio micro-hole multi-energy-field assisted laser drilling method, which organically combines and synergizes ultrafast laser ablation, ultrasonic vibration along the drilling axial direction and coaxial low-temperature high-speed airflow to overcome the problems of limited processing depth, poor hole wall quality and low processing efficiency caused by poor ablation product chip removal and significant thermal effect in the prior art.

[0007] A silicon carbide large-depth-ratio micro-hole multi-energy-field assisted laser drilling method, comprising the following steps:

[0008] An ultrafast laser beam is used to perform layer-by-layer ablation on a silicon carbide workpiece to form a micro-hole;

[0009] During the layer-by-layer ablation, relative high-frequency micro-amplitude ultrasonic vibration is generated along the axial direction of the micro-hole, and low-temperature high-speed airflow is coaxially introduced to the ablation point of the ultrafast laser beam to remove ablation products and cool the ablation point and its adjacent area.

[0010] Further, the temperature of the low-temperature high-speed airflow ranges from -70℃ to -10℃.

[0011] Setting the temperature of the low-temperature high-speed airflow in the depth low-temperature range of -70℃ to -10℃ can achieve the effect of "forced quenching" on the high-temperature molten material generated instantaneously by laser ablation. This rapid cooling causes the viscous molten material to solidify and become brittle rapidly, greatly reducing its adhesion to the hole wall, making it easier to be stripped by ultrasonic vibration and removed by high-speed airflow. At the same time, this low-temperature environment effectively inhibits the oxidation reaction of silicon carbide at high temperatures, avoiding the formation of a hard silica layer that absorbs laser energy and is difficult to remove, thereby ensuring the continuity of the processing and the purity of the hole wall.

[0012] Further, the outlet flow rate of the low-temperature high-speed airflow is higher than 10m / s.

[0013] By ensuring that the outlet flow rate of the low-temperature high-speed airflow is higher than 10m / s, sufficient kinetic energy and impact force can be provided for the airflow. This high-speed airflow can penetrate through the complex flow field environment in the deep hole and reach the bottom of the hole, strongly carrying and blowing out the ablation product particles stripped by ultrasonic vibration and already brittle outside the hole. This effectively avoids the accumulation and blockage of ablation products in the hole, ensuring the smoothness of the laser beam transmission path, which is a necessary dynamic condition for stable and efficient deep hole processing.

[0014] Further, the frequency of the relative high-frequency micro-amplitude vibration is 15kHz to 40kHz, and the amplitude is 1μm to 10μm.

[0015] The vibration frequency is set in the ultrasonic wave band of 15 kHz to 40 kHz, and is matched with a micro amplitude of 1 μm to 10 μm, so that the most efficient mechanical stripping effect can be realized without affecting the micron-level positioning precision of laser processing. The high-frequency vibration can generate a high-acceleration shaking effect on the ablation product, effectively overcoming the adhesion between the product and the hole wall; and the micron-level amplitude can ensure the stripping effect and avoid the decrease of the hole type precision caused by excessive vibration, so that the best balance between the chip removal effect and the processing precision is realized.

[0016] Further, the flow direction of the cooling gas flow is coaxial with the ultrafast laser beam and surrounds the ultrafast laser beam.

[0017] The cooling gas flow surrounds and is coaxial with the ultrafast laser beam, which has three advantages. First, the cooling and blowing effects can be most accurately focused on the laser ablation point, so that the energy utilization and the chip removal efficiency are maximized. Second, the surrounding gas flow forms a uniform pressure field at the hole, which helps to process a micro-hole with better roundness and smaller taper. Third, the downward gas flow also forms a wind screen, effectively preventing the machining debris and plasma from splashing upward, thereby protecting the precise optical elements of the laser head and improving the stability and service life of the equipment.

[0018] Further, in the process of the layer-by-layer ablation, further comprising:

[0019] According to the real-time processing depth of the micro-hole, the flow direction and / or the focusing position of the cooling gas flow are dynamically adjusted.

[0020] By dynamically adjusting the flow direction or the focusing position of the cooling gas flow according to the real-time processing depth of the micro-hole, the adaptive adjustment strategy ensures that the efficiency of the auxiliary gas flow always remains in the best state regardless of the processing depth, and the action point is always synchronized with the laser ablation front, which is the key to stable processing of a large depth-to-diameter ratio (such as > 15:1).

[0021] The second object of the present application is to provide a multi-energy field assisted laser drilling device for implementing the multi-energy field assisted laser drilling method of the silicon carbide micro-hole with a large depth-to-diameter ratio as described above, and the device comprises:

[0022] A laser processing system for generating the ultrafast laser beam acting on the to-be-processed region of the silicon carbide workpiece;

[0023] An ultrasonic vibration workbench for carrying the silicon carbide workpiece and generating a relative high-frequency micro-amplitude vibration along the axial direction of the ultrafast laser beam between the silicon carbide workpiece and the ultrafast laser beam;

[0024] A cooling gas flow system for supplying the low-temperature high-speed gas flow to the to-be-processed region.

[0025] Further, the cooling airflow system comprises a cylindrical nozzle and uniformly distributed spray holes on the nozzle, the nozzle has a central passage for passing the ultrafast laser beam, and the nozzle is coaxially arranged on the transmission path of the ultrafast laser beam.

[0026] The annular nozzle structure with a central passage provides a simple, stable and reliable implementation scheme for realizing the shaft surrounding airflow. It ensures the unobstructed passage of the laser beam, and at the same time, the uniformly distributed spray holes can form a stable and energy concentrated airflow that accurately acts on the machining area.

[0027] Further, the multi-energy field assisted laser drilling device further comprises:

[0028] The adjusting mechanism is used for adjusting the posture of the nozzle and / or the airflow of different spray holes in the nozzle, so as to change the flow direction or focusing position of the low-temperature high-speed airflow.

[0029] By arranging the adjusting mechanism, the ability to actively change the flow direction or focusing position of the airflow is achieved, which provides hardware support for the dynamic adjustment method, so that the cooling airflow system of the device is changed from a static and fixed system to a dynamically controllable and intelligent system, thereby actively adapting to the change of the machining depth to realize efficient machining of the ultra-deep hole.

[0030] Further, the multi-energy field assisted laser drilling device further comprises:

[0031] The sensor is used for acquiring real-time machining depth information of the micro-hole;

[0032] The controller is electrically connected with the sensor and the adjusting mechanism, and is configured to control the adjusting mechanism to adjust the flow direction or focusing position of the low-temperature high-speed airflow in real time based on the real-time machining depth information.

[0033] Through the sensor and the controller, a real-time closed-loop feedback control system about the focusing position of the airflow is constructed. The airflow state can be automatically adjusted in real time according to the actual machining depth without manual intervention, which improves the stability and repeatability of the machining process.

[0034] The beneficial effects of the present application are:

[0035] The application provides a multi-energy field assisted laser drilling method for a silicon carbide micro-hole with a large depth-diameter ratio. The biggest problem of single laser processing is that the sticky molten ablation product is difficult to discharge. The high-temperature molten product is first forced to quench by the low-temperature high-speed airflow, so that it is quickly solidified, embrittled and the adhesion to the hole wall is reduced; the high-frequency micro-amplitude ultrasonic vibration can shake off and peel off these embrittled products from the hole wall and the hole bottom, and finally the high-speed airflow carries them out of the hole. The shielding effect of the ablation product on the subsequent laser is overcome, so that the laser energy can continuously and stably act on the hole bottom. In addition, the low-temperature high-speed airflow forms a local low-temperature low-oxygen environment in the processing area. The oxidation reaction of silicon carbide at high temperature is effectively inhibited, and the generation of hard silica layer on the hole wall which is difficult to remove and absorbs laser energy is avoided; on the other hand, the rapid cooling effect greatly reduces the heat affected zone, improves the quality of the recast layer of the hole wall, and reduces the risk of thermal micro-cracks around the hole, so that a high-quality micro-hole with smaller taper, lower edge collapse and smoother hole wall is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0036] Fig. 1 is a schematic diagram of a multi-energy field assisted laser drilling device provided in the embodiments of the application;

[0037] Fig. 2 is a schematic diagram of a laser head integrated with a ring array nozzle device provided in the embodiments of the application;

[0038] Fig. 3 is a processing schematic diagram of the multi-energy field assisted laser drilling method provided in the application.

[0039] REFERENCE SIGNS:

[0040] 11, ultrafast laser source; 18, processing platform; 22, nozzle; 23, laser beam outlet. DETAILED DESCRIPTION

[0041] The preferred embodiments of the application will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the application are shown in the drawings, it should be understood that the application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the application more thorough and complete, and to fully convey the scope of the application to those skilled in the art.

[0042] In order to better understand the application, the technical features involved in the application are further explained as follows:

[0043] Ultrafast laser beam, specifically refers to the laser pulse beam with pulse width reaching picosecond (10 -12 second) or femtosecond (10 -15 second) order. Its core feature is the extremely short action time, which is much smaller than the time required for heat conduction within the material.

[0044] High-frequency micro-amplitude ultrasonic vibration, high frequency refers to the vibration frequency in the ultrasonic wave range (usually 15 kHz to 40 kHz); micro-amplitude refers to the extremely small amplitude of the vibration, usually in the micron (μm) level (for example, 1 μm to 10 μm). The vibration is applied to the workpiece, making it move back and forth along the axis of the laser beam (i.e. the depth direction of the micro-hole).

[0045] Low-temperature high-speed gas flow, low temperature refers to the temperature of the gas flow being significantly lower than normal temperature, usually in the deep refrigeration range of minus 10℃ to 70℃; high speed refers to the gas flow having a high flow rate (for example, higher than 10 m / s) at the nozzle outlet, having sufficient momentum and impact force.

[0046] The present application provides a multi-energy field assisted laser drilling device and method for silicon carbide micro-holes with large depth-to-diameter ratio. By synergistically coupling ultrafast laser beam, high-frequency micro-amplitude ultrasonic vibration along the drilling axis, and coaxial low-temperature high-speed gas flow, the problems of limited processing depth, poor hole wall quality, and low processing efficiency caused by poor ablation product chip removal and significant thermal effect when processing hard and brittle materials such as silicon carbide to form micro-holes with large depth-to-diameter ratio are effectively solved.

[0047] As shown in Figs. 1 to 3 , the present application provides a multi-energy field assisted laser drilling device, mainly including a high-stability processing platform 18, a laser processing system installed on the processing platform 18, an ultrasonic vibration workbench, and a cooling gas flow system.

[0048] In a specific embodiment of the present application, the base and main body structure of the device can be made of materials with excellent shock absorption and thermal stability, such as natural granite or Meehan cast iron, to ensure the ultra-high stability and positioning accuracy of the entire system during high-speed operation. The ultrasonic vibration workbench is integrated on the processing platform 18.

[0049] The ultrasonic vibration workbench is the core component that carries and drives the workpiece to vibrate. The workbench is used to carry and stably fix the silicon carbide workpiece to be processed. To ensure that the workpiece remains stable in position when subjected to high-frequency vibration, the fixing method can adopt a composite design, for example, a vacuum chuck with a micro-hole array is provided on the surface of the workbench, and the workpiece is adsorbed by negative pressure; at the same time, ultraviolet light curing (UV) glue is applied to the edge of the workpiece for auxiliary bonding, forming double locking of vacuum and bonding.

[0050] The internal core of the ultrasonic vibration workbench is an ultrasonic transducer and an ultrasonic generator. The ultrasonic generator serves as an electrical signal source to generate a high-frequency sinusoidal electrical signal of a specific frequency (e.g., 15 kHz to 40 kHz), which is transmitted to the ultrasonic transducer through a cable. The ultrasonic transducer, such as a piezoelectric ceramic stack transducer, uses the inverse piezoelectric effect to efficiently convert the input high-frequency electrical energy into mechanical vibrations of the same frequency. After amplification and optimization by the horn, the vibrations drive the entire workbench table along with the workpiece fixed thereon to produce a controllable high-frequency micro-reciprocal motion along the incident axis of the laser beam (i.e., the processing depth direction, usually defined as the Z-axis), with an amplitude that can be precisely adjusted within a range of one to ten microns (1 μm-10 μm). This axial vibration can effectively loosen and embrittle the ablation products (such as slag, oxide particles, etc.) on the hole wall and hole bottom during laser ablation through "shaking" and "impact", and then peel them off from the substrate, creating extremely favorable conditions for subsequent airflow cleaning.

[0051] Above the ultrasonic vibration workbench, a laser processing system is vertically arranged. This system is the main body for material removal. The laser processing system includes an ultrafast laser source 11, a set of precise beam transmission and collimation unit (i.e., transmission optical path), and a dedicated spiral cutting laser head. Among them, the ultrafast laser source 11 is preferably an industrial picosecond laser or femtosecond laser, which generates laser pulses with a width of picoseconds (10-12s) or femtoseconds (10-15s), and can act on the material with extremely high energy density in a very short time to achieve cold ablation with a very small heat-affected zone. The laser wavelength can be selected according to the absorption characteristics of silicon carbide materials, such as 1064 nm, 532 nm, or 355 nm.

[0052] After the laser beam is emitted from the laser source, it enters the transmission optical path, which includes a laser optical path lens group that can include a mirror group, a beam expander, and a high-speed galvanometer scanning system. The galvanometer scanning system precisely controls the scanning trajectory of the laser beam in the X-Y plane through two high-speed deflectable mirrors. Finally, the laser beam is guided to the spiral cutting laser head, focused into a micron-level small spot by the internal focusing lens group (such as F-Theta lens), and irradiated on the workpiece area to be processed. The spiral cutting laser head controls the galvanometer scanning system to make the focused spot perform layer-by-layer scanning ablation on the material in the form of a spiral line, concentric circle, or other preset filling path, thereby carving out high-precision and high-steepness micro-holes layer by layer.

[0053] Coaxial with the laser processing system is a cooling airflow system, which is the key to achieving efficient chip removal and thermal management. In this embodiment, the system integrates a specially designed annular array nozzle device at the end of the helical cutting laser head, i.e. the end closest to the workpiece. The annular array nozzle device is integral with the helical cutting laser head. Inside the annular array nozzle device is a cold air cavity. The external gas source (e.g. high-purity compressed air, or inert protective gas such as argon, nitrogen, etc. for optimal oxidation resistance) is first deeply cooled by a high-efficiency refrigeration unit, which can be a vortex tube-based refrigerator or a compressor refrigeration cycle system, capable of reducing the gas temperature to an ultra-low temperature range of -70°C to -10°C.

[0054] The cooled gas is introduced into the cold air cavity and then sprayed out at high speed through multiple micro-nozzles evenly distributed along the circumference of the annular nozzle 22. To achieve higher outlet flow velocity (e.g. higher than 10 m / s, even reaching supersonic speed), these nozzles can be designed as converging-diverging Laval nozzle structures. The geometric center of the annular nozzle 22 is provided with a through-hole as the laser beam outlet 23, ensuring that the laser beam can pass through unobstructed. This coaxial surrounding design ensures that the multiple low-temperature high-speed air streams can converge and precisely act on the laser ablation point and its adjacent area. The low-temperature high-speed airflow has a dual key role: first, it forcibly and efficiently blows the ultrasonic vibration stripped ablation products out of the deep hole, keeping the processing channel clean; second, it forcibly quenches the processing area with extremely low temperature, greatly inhibiting the oxidation reaction of silicon carbide to generate hard silicon dioxide under the action of laser, while quickly removing heat, significantly reducing the thickness of the heat-affected zone and recast layer.

[0055] To address the problem of increased chip removal difficulty due to increased hole depth in deep hole machining, the device can further be configured with a dynamic self-adaptive adjustment system. The system includes an adjustment mechanism for real-time adjustment of the annular nozzle 22, a sensor for detecting the real-time depth of the micro-hole, and a central controller.

[0056] The adjustment mechanism can be composed of a multi-axis precision electric translation stage or a piezoelectric ceramic driver, which can realize fine adjustment of the overall attitude (such as pitch and yaw angles) of the annular nozzle 22. In addition, it can also change the gas flow of different direction nozzles by controlling multiple independent electrically controlled proportional valves connected to different groups of nozzles, thereby dynamically reshaping and guiding the flow direction and focusing position of the synthetic gas flow. Sensors such as laser confocal displacement sensors or spectral analyzers are configured to monitor the depth of the processing hole in real time in a non-contact manner. The controller (such as an industrial PC or PLC) receives real-time depth data from the sensor and issues instructions to the adjustment mechanism according to a pre-set control algorithm (for example, the algorithm can preset the optimal gas flow convergence point position at different depths). Through this closed-loop feedback control, adaptive adjustment of the gas flow focusing point can be realized, ensuring that the convergence point of the multi-beam gas flow can always dynamically match the current action point of the laser throughout the processing process from the hole to the hole bottom, thereby ensuring optimal chip removal and cooling effect at any depth.

[0057] As shown in Fig. 3 The present application provides a multi-energy field assisted laser drilling method for silicon carbide micro-holes with large depth-to-diameter ratio. The method utilizes the above-mentioned multi-energy field assisted laser drilling device to realize the synergistic effect of ultrafast laser ablation, ultrasonic vibration assisted peeling, and low-temperature high-speed airflow assisted chip removal and cooling. The specific steps include:

[0058] Step one: Workpiece pretreatment.

[0059] The carbonized silicon workpiece to be processed is cleaned, for example, ultrasonic cleaning in anhydrous ethanol solution to remove surface oil and impurities, and then dried.

[0060] More specifically, this step is the basis for ensuring the quality and stability of subsequent processing. The purpose is to obtain a clean, stress-free workpiece surface. The carbonized silicon workpiece to be processed needs to be thoroughly cleaned first. The preferred cleaning method is to place the workpiece in a container containing high-purity organic solvents such as anhydrous ethanol or isopropanol, and perform ultrasonic cleaning for a duration of usually 10 to 15 minutes. The cavitation effect produced by ultrasonic waves can effectively remove processing oil stains, dust particles, and other contaminants remaining in the surface and micro-pores of the workpiece. The presence of these contaminants not only affects the adhesion strength of the subsequent UV-cured glue, but also may carbonize under the action of the laser, interfering with the stable absorption of laser energy and affecting the processing precision and quality. After cleaning, the workpiece needs to be thoroughly dried. Clean compressed air or nitrogen can be used for drying, followed by placing in a constant temperature oven at a temperature of, for example, 80°C for 30 minutes to ensure that the surface adsorbed solvent molecules are completely removed, avoiding interference with the laser beam or causing unnecessary chemical reactions during processing.

[0061] Step two: Workpiece fixation and positioning.

[0062] The clean workpiece is placed on the ultrasonic vibration workbench, which can be fixed by vacuum adsorption and UV adhesive adhesion, etc. to ensure the stability of the workpiece during processing. Then, the precise position of the micro-hole to be processed is determined by the CCD vision system.

[0063] More specifically, the key of this step is to ensure the absolute position stability of the workpiece in the complex processing environment of high-frequency vibration and laser impact. The clean and dry workpiece is placed on the ultrasonic vibration workbench of the device. The invention uses a combination of vacuum adsorption and UV curing adhesive adhesion for cooperative fixation. First, the built-in vacuum adsorption function of the workbench is started to preliminarily adsorb and flatten the workpiece on the workbench surface, eliminating the gap between the workpiece and the surface. Then, a layer of ultraviolet light curing (UV) adhesive is applied to the edge area of the workpiece and is cured by ultraviolet light source. Vacuum adsorption provides initial positioning and good planar contact, while UV adhesive provides rigid connection, which is crucial for the high-frequency micro-vibration generated by the ultrasonic transducer to be transmitted to the entire workpiece without loss and high fidelity, ensuring effective use of vibration energy. After the workpiece is fixed, the high-resolution CCD vision system integrated on the device is used for accurate alignment. The system captures the image of the workpiece surface, automatically or manually identifies the reference mark or feature edge on the workpiece using image recognition algorithm, and establishes the accurate mapping relationship between the workpiece coordinate system and the device motion coordinate system. This ensures that the starting point of the subsequent laser drilling can be positioned within the micron-level accuracy required by the design.

[0064] Step three: processing parameter setting.

[0065] In the control software, a three-dimensional removal model is established according to the size of the target micro-hole (such as hole diameter, depth, shape). The laser processing parameters are set, including laser power, frequency, scanning speed, single-layer scanning height, scanning filling method (such as spiral filling), etc. At the same time, the parameters of the multi-energy field auxiliary system are set, including the vibration frequency and amplitude of the ultrasonic vibration platform, and the gas temperature and outlet flow rate of the cooling gas flow system.

[0066] More specifically, this step is the core of achieving the expected processing result, which requires the collaborative optimization of the parameters of laser, ultrasonic vibration and cooling gas flow according to the material properties, micro-hole geometry, etc. In the control software of the device, a three-dimensional digital removal model is first established according to the geometric parameters of the target micro-hole (such as hole diameter of 0.5mm, depth of 8mm, i.e. depth to diameter ratio of 16:1). Then, the parameters of each system are set:

[0067] 1. Ultrafast laser beam parameter setting:

[0068] The ultrafast laser with pulse width in the order of picosecond (ps) or femtosecond (fs) is selected. Its cold ablation characteristic, i.e. the energy acts on the material in a very short time, makes the material directly sublimate or vaporize, and the heat has no time to spread to the surrounding, thereby greatly reducing the generation of heat-affected zone, recast layer and micro-cracks.

[0069] The material removal threshold and efficiency requirements are set. For example, the laser average power can be set to 20W to 40W, and the repetition frequency can be set to 100kHz to 500kHz. Higher power and frequency generally mean faster material removal rate, but need to be matched with the scanning speed to avoid excessive heat accumulation.

[0070] For circular micro-holes, it is preferred to use a filling method of spiral scanning or concentric circle scanning, which can better ensure the smoothness and roundness of the hole wall than the traditional reciprocating raster scanning. The scanning pitch is usually set to 5μm to 20μm to ensure sufficient energy overlap rate.

[0071] The single-layer removal thickness is set to 2μm to 10μm, which has a significant impact on the chip removal effect and the quality of the side wall. Thinner layer thickness is beneficial to the discharge of ablation products, but it will reduce the overall processing efficiency. In actual processing, a variable parameter strategy can be used, i.e. a thicker layer thickness is used at the beginning of processing to improve efficiency, and the layer thickness is appropriately reduced as the hole depth increases to ensure smooth chip removal.

[0072] 2. High-frequency micro-amplitude ultrasonic vibration parameter setting:

[0073] The frequency is usually determined by the inherent characteristics of the ultrasonic transducer, and the typical range is 15kHz to 40kHz.

[0074] The amplitude is a key adjustable parameter that determines the size of the vibration impact energy. The amplitude is usually set to 1μm to 10μm. Appropriate amplitude can effectively "shake off" the ablation products attached to the hole wall and hole bottom, but excessive amplitude may cause fatigue damage or clamping loosening of the workpiece.

[0075] 3. Low-temperature high-speed gas flow parameter setting:

[0076] The gas temperature setting range is usually -10℃ to -70℃. Lower temperature can more effectively quench high-temperature molten material, making it quickly brittle and reducing viscosity, and can more significantly inhibit oxidation reaction.

[0077] The outlet flow rate setting range is usually 10m / s to 40m / s or higher. Higher flow rate means stronger momentum, which can carry heavier and deeper ablation particles out of the hole.

[0078] In the standard requirements, clean and dry compressed air can be used. For the application with extremely high antioxidant requirements, inert gases such as argon (Ar) and nitrogen (N2) can be selected to fundamentally eliminate the generation of hard silica layer in the processing process.

[0079] Step four: multi-energy field synergy drilling.

[0080] Start the multi-energy field auxiliary system, i.e. turn on the ultrasonic generator to make the workpiece produce axial high-frequency micro-vibration, and start the cooling gas flow system to deliver low-temperature high-speed gas flow to the processing area. Then, start the laser processing system, and the ultrafast laser beam ablates the workpiece layer by layer according to the preset path.

[0081] More specifically, this step is the core of the execution of the method of the present application, and the three physical fields are tightly coupled and synergistically act in this stage to achieve efficient and high-quality processing of micro-holes with large depth-diameter ratio. After starting the processing program, the ultrasonic vibration system and the low-temperature gas flow system are first activated, and a stable vibration field and low-temperature gas flow field are established in the area to be processed before the laser beam acts on the workpiece. Then, the laser processing system is started, and the ultrafast laser beam removes the material layer by layer according to the preset scanning path. The microcosmic synergistic process is as follows:

[0082] The single ultrafast laser pulse gasifies and melts a small amount of silicon carbide material in an instant, forming a mixture of plasma, vapor and high-temperature molten particles. The low-temperature high-speed gas flow, which arrives almost simultaneously with the laser pulse, immediately forcibly quenches these high-temperature ablation products. The high-temperature molten material solidifies and becomes brittle in a very short time, greatly reducing its adhesion to the hole wall. At the same time, the impact force of the gas flow begins to blow the lighter particles and vapor out of the hole. The workpiece as a whole vibrates in the axial direction with high frequency and small amplitude. This continuous mechanical impact makes the ablation particles, which have been brittle and weakly connected to the hole wall or hole bottom, completely loose and peeled off. The solid particles peeled off by vibration are suspended in the hole, and the high-speed gas flow immediately carries them as carriers, using strong kinetic energy to efficiently carry and eject these "cleaned" particles out of the micro-hole.

[0083] This cycle of "laser ablation → gas flow quenching → vibration peeling → gas flow chip removal" repeats at a high speed with each scanning point of the laser, forming a dynamic and efficient closed loop of material removal and product cleaning. As the hole depth increases, the system can also dynamically adjust the attitude of the gas flow nozzle so that the gas flow focal point can act more deeply on the hole bottom, ensuring the continuous chip removal capability.

[0084] Step five: post-processing and detection.

[0085] After processing, stop all systems. After softening the UV glue with a debonder, remove the workpiece and perform ultrasonic cleaning again to remove surface residues. Finally, use a laser confocal microscope, scanning electron microscope and other equipment to detect the quality of the processed micro-holes, including aperture, depth, taper, hole wall morphology, etc.

[0086] In order to better understand the present application, several specific embodiments are listed below.

[0087] Example One

[0088] This example aims to process a through hole with a depth-to-diameter ratio of 8:1.

[0089] The workpiece is a sintered silicon carbide (SSiC) with a thickness of 8.0 mm, and the target is to process a through hole with a diameter of 1.0 mm.

[0090] Method steps:

[0091] 1. Pretreatment and fixation:

[0092] The SSiC workpiece is ultrasonically cleaned with anhydrous ethanol and dried, then fixed on the ultrasonic vibration workbench by vacuum adsorption and UV glue, and positioned by CCD.

[0093] 2. Ultrafast laser beam:

[0094] A picosecond laser is selected, with a laser power of 31.88 W and a repetition frequency of 100 kHz. In the control software, a cylindrical removal model with a diameter of 1.0 mm and a height of 8.0 mm is established. The removal height of each layer is set to 0.005 mm, the scanning pitch is 0.01 mm, the scanning speed is 500 mm / s, and the filling method is spiral filling. The ultrafast laser beam in this case realizes cold processing through its ultra-short pulse width (picosecond order), with a very small heat affected zone, effectively reducing thermal damage to the material.

[0095] 3. High-frequency micro-amplitude ultrasonic vibration:

[0096] Turn on the ultrasonic vibration platform and set the vibration frequency to 20 kHz (within the range of 15 kHz to 40 kHz) and the amplitude to 5 μm (within the range of 1 μm to 10 μm). This vibration provides continuous mechanical impact energy to the ablation products, making it difficult for them to firmly adhere to the hole wall and hole bottom.

[0097] 4. Low-temperature high-speed airflow:

[0098] Start the cryogenic air cooling system, use compressed air as the gas source, set the outlet gas temperature to -15°C (in the range of -70°C to -10°C), and the nozzle outlet flow rate to 15 m / s (higher than 10 m / s). The airflow continuously scours the processing area, blowing out loose particles, and the low-temperature effect inhibits the oxidation of SiC.

[0099] 5. Post-processing:

[0100] Start the processing, and after the processing is completed, remove the workpiece according to the standard process and clean it.

[0101] 6. Test results:

[0102] Using a scanning electron microscope, the resulting micro-hole taper is extremely small, the hole wall is smooth, and there is no obvious slag and oxide residue.

[0103] Example Two

[0104] This example aims to process a blind hole with a depth-to-diameter ratio greater than 10:1.

[0105] The workpiece is a chemical vapor deposition silicon carbide (CVD-SiC) with a thickness of 10.0 mm, and the target is to process a blind hole with a hole diameter of 0.4 mm and a depth of 6.0 mm (depth-to-diameter ratio of 15:1).

[0106] Method steps:

[0107] 1. Pretreatment and fixation:

[0108] The CVD-SiC workpiece is ultrasonically cleaned with anhydrous ethanol and dried, then fixed on the ultrasonic vibration workbench by vacuum adsorption and UV glue, and positioned by CCD.

[0109] 2. Ultrafast laser beam:

[0110] Laser power 31.88 W, frequency 100 kHz. A cylindrical removal model with a diameter of 0.4 mm and a height of 6.0 mm is established. To ensure the energy density at the bottom of the deep hole, set the removal height of each layer to 0.008 mm, the scanning pitch to 0.01 mm, the scanning speed to 400 mm / s, and the spiral filling. The high peak power density of the ultrafast laser beam is the key to effectively removing the superhard CVD-SiC material.

[0111] 3. High-frequency micro-amplitude ultrasonic vibration:

[0112] Set the vibration frequency to 25 kHz and the amplitude to 5 μm. For a blind hole with a very large depth-to-diameter ratio, the removal of debris at the bottom of the hole is the biggest difficulty, and high-frequency vibration is crucial for the peeling of ablation at the bottom of the hole.

[0113] 4. Low-temperature high-speed airflow:

[0114] To cope with the challenge of chip removal caused by deeper hole depth and smaller hole diameter, the outlet gas temperature was set to -45℃ and the nozzle outlet flow rate was 32 m / s. Lower temperature and higher flow rate were aimed to provide stronger cooling effect and chip removal kinetic energy, ensuring stable machining environment at the bottom of deep hole.

[0115] 5. Post-processing:

[0116] Start machining, after machining is completed, take out the workpiece and clean according to the standard process.

[0117] 6. Test results:

[0118] The test showed that a high-quality blind hole with a depth-to-diameter ratio of 15:1 was successfully obtained, the hole shape was regular, and there was no a large amount of slag and oxide on the hole wall.

[0119] Example Three

[0120] This example aims to machine a stepped hole to demonstrate the ability to machine complex hole shapes.

[0121] The workpiece is a piece of CVD-SiC with a thickness of 10.0 mm, and the target is to machine a stepped hole with a large hole diameter of 1.0 mm and a depth of 5.0 mm, and a small hole diameter of 0.5 mm and a depth of 5.0 mm.

[0122] 1. Pretreatment and fixation:

[0123] The CVD-SiC workpiece was ultrasonically cleaned with anhydrous ethanol and dried, then fixed on the ultrasonic vibration workbench by vacuum adsorption and UV glue, and positioned by CCD.

[0124] 2. Ultrafast laser beam:

[0125] The laser power was 31.88 W and the frequency was 100 kHz. The corresponding stepped shaft removal model was established in the software. When machining the large hole, the layer height was set to 0.005 mm and the scanning speed was 500 mm / s; when machining the small hole, the layer height was set to 0.008 mm and the scanning speed was 400 mm / s. Through software control, the scanning range and parameters of the laser beam can be flexibly switched to accurately realize the machining of complex shapes.

[0126] 3. High-frequency micro-amplitude ultrasonic vibration:

[0127] The vibration frequency was set to 28 kHz and the amplitude was 5 μm.

[0128] 4. Low-temperature high-speed airflow:

[0129] To cope with the influence of hole diameter change on airflow field during machining, the outlet gas temperature was set to -60℃ and the nozzle outlet flow rate was 32 m / s to provide strong cooling and blowing capacity to meet the machining requirements at different stages.

[0130] 5. Perform post-processing:

[0131] Start processing, after processing is completed, take out the workpiece according to the standard process and clean.

[0132] 6. Test results:

[0133] The detection shows that the size accuracy of the stepped hole is high, the transition of the large hole and the small hole is clear, the taper is very small, and the hole wall quality is excellent.

[0134] The application provides a high-efficiency and high-quality silicon carbide micro-hole machining method with a large depth-diameter ratio through the synergistic effect of ultrafast laser, ultrasonic vibration and low-temperature high-speed airflow. The method not only improves the machining depth limit, but also greatly improves the hole wall quality, improves the machining efficiency, and has the ability to machine complex hole types, thereby providing key technical support for the application of hard and brittle materials such as silicon carbide in high-end fields.

[0135] Unless specifically stated otherwise, the relative arrangements of parts and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the application. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0136] In addition, it should be noted that the use of the words "first", "second", and the like is merely for the convenience of distinction, and unless otherwise stated, the above words do not have special meanings, and therefore cannot be understood as limiting the scope of protection of the application.

[0137] The above only describes the preferred embodiments of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method of multi-energy field assisted laser drilling of silicon carbide micro-holes with a large depth-to-diameter ratio, characterized in that, The method comprises the following steps: layer-by-layer ablation of a silicon carbide workpiece by an ultrafast laser beam to form a micro-hole; during the layer-by-layer ablation, relatively high-frequency micro-amplitude ultrasonic vibration is generated along the axial direction of the micro-hole between the workpiece and the ultrafast laser beam, and a low-temperature high-speed gas flow is coaxially introduced to the ablation point of the ultrafast laser beam to remove ablation products and cool the ablation point and its adjacent area.

2. The multi-energy field assisted laser drilling method for a silicon carbide micro-hole with a large depth-to-diameter ratio according to claim 1, wherein: the low-temperature high-speed gas flow has a temperature ranging from -70°C to -10°C.

3. The multi-energy field assisted laser drilling method for a silicon carbide micro-hole with a large depth-to-diameter ratio according to claim 1, wherein: the low-temperature high-speed gas flow has an outlet flow rate higher than 10 m / s.

4. The multi-energy field assisted laser drilling method for a silicon carbide micro-hole with a large depth-to-diameter ratio according to claim 1, wherein: the relatively high-frequency micro-amplitude vibration has a frequency of 15 kHz to 40 kHz and an amplitude of 1 μm to 10 μm.

5. The multi-energy field assisted laser drilling method for a silicon carbide micro-hole with a large depth-to-diameter ratio according to claim 1, wherein: the flow direction of the cooling gas flow is coaxial with the ultrafast laser beam and surrounds the ultrafast laser beam.

6. The multi-energy field assisted laser drilling method for a silicon carbide micro-hole with a large depth-to-diameter ratio according to claim 1, wherein: during the layer-by-layer ablation, the following steps are further included: based on the real-time machining depth of the micro-hole, the flow direction and / or the focusing position of the cooling gas flow are dynamically adjusted.

7. A multi-energy field assisted laser drilling apparatus, characterized by, An apparatus for implementing the multi-energy field assisted laser drilling method for a silicon carbide micro-hole with a large depth-to-diameter ratio according to any one of claims 1 to 6, the apparatus comprising: a laser processing system for generating the ultrafast laser beam acting on a to-be-processed region of a silicon carbide workpiece; an ultrasonic vibration workbench for carrying the silicon carbide workpiece and generating relatively high-frequency micro-amplitude vibration along the axial direction of the ultrafast laser beam between the silicon carbide workpiece and the ultrafast laser beam; a cooling gas flow system for supplying the low-temperature high-speed gas flow to the to-be-processed region.

8. The multi-energy field assisted laser drilling apparatus according to claim 7, wherein: the cooling gas flow system comprises a cylindrical nozzle having a central passage for passing through the ultrafast laser beam and a plurality of spray holes uniformly arranged on the nozzle, and the nozzle is coaxially arranged on the transmission path of the ultrafast laser beam.

9. The multi-energy field assisted laser drilling apparatus of claim 8, wherein, The multi-energy field assisted laser drilling apparatus further comprises: an adjustment mechanism for adjusting the posture of the nozzle and / or the gas flow rate of different spray holes in the nozzle to change the flow direction or focusing position of the low-temperature high-speed gas flow.

10. The multi-energy field assisted laser drilling apparatus of claim 9, wherein, The multi-energy field assisted laser drilling apparatus further comprises: a sensor for acquiring real-time machining depth information of the micro-hole; a controller electrically connected to the sensor and the adjustment mechanism, and configured to control the adjustment mechanism to adjust the flow direction or focusing position of the low-temperature high-speed gas flow in real time based on the real-time machining depth information.

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