Ultrathin flexible folding glass laser micromachining deformation inhibition method

Abstract

The invention provides an ultra-thin flexible folded glass laser micromachining deformation inhibition method. The method comprises the following steps: S1, dynamic capability modulation; step S2, parting path planning; and S3, composite processing, wherein the heat input error can be reduced from + / -15% to + / -3%, the energy distribution uniformity can be improved, the edge ablation defect can be eliminated, the width of a heat affected zone can be effectively reduced, the glass substrate can be divided into millimeter-level micro-zones through stress optimization sub-domain division, staged temperature gradient release can be realized in cooperation with a delayed cooling strategy, and the heat transfer efficiency can be improved. The residual stress peak value is reduced to 0.8 MPa or below, micro-cracks can be synchronously eliminated after cutting, the fracture toughness of the glass is improved to 1.8 MPa.m / , meanwhile, a hydrofluoric acid gradient etching technology is combined, non-linear control over the etching rate is achieved through concentration and time double-variable regulation and control, the surface roughness Ra is smaller than or equal to 0.1 micron, the deformation inhibition rate of the ultra-thin glass breaks through 99%, and the ultra-thin glass has the good mechanical property. The yield is stabilized to be 99.5% or above, the machining period is shortened by 40%, and high-precision forming of complex special-shaped contours can be compatible.

Description

Technical Field

[0001] This invention belongs to the field of laser micromachining of ultrathin flexible folding glass. Specifically, this invention relates to a method for suppressing deformation during laser micromachining of ultrathin flexible folding glass. Background Technology

[0002] Ultrathin sodium aluminum silicate glass has become the core cover material for foldable screens due to its excellent optical properties and mechanical strength. To achieve flexibility in the folding area of ​​the screen, a functional weakening pattern composed of thousands of micron-sized short lines (between 50μm and 200μm in length) needs to be processed inside the glass. Infrared picosecond lasers (wavelength 1064nm, pulse width 10ps) are widely used in this process due to their high peak power and low thermal effect.

[0003] However, existing technologies have the following drawbacks: thermal stress accumulation deformation; during high-density pattern cutting, the thermal shock generated by repeated laser positioning creates an asymmetric stress field inside the glass. Experiments show that when the line segment (x, y) spacing is < (18μm, 20μm), the glass curvature radius deviation after a single processing reaches 15%-22%; edge breakage and chipping; the nonlinear absorption of picosecond lasers causes micro-detonation effects in the cutting zone, and the brittle fracture propagation depth exceeds 8% of the glass thickness (0.02mm threshold). SEM (scanning electron microscopy) observation shows that the chipping width is greater than 5μm, reducing fatigue life; process parameter mismatch; the traditional fixed power (3W-5W) and scanning speed (200mm / s-500mm / s) strategy cannot adapt to changes in line segment density gradient, and the thermal relaxation time in the high-density area is insufficient (<0.1ms), leading to crack branching. Traditional processes employ constant laser power and scanning speed, resulting in excessive energy input in high-density pattern areas (X-axis line spacing < 18 μm, Y-axis line spacing < 20 μm). Due to the low thermal diffusivity of sodium aluminosilicate glass (≈ 0.8 mm² / s), the overlap rate of the heat-affected zone (HAZ) between adjacent processing points exceeds 40% (see Appendix). Figure 3 This results in an asymmetric residual stress field. Test data shows that the local curvature radius of the glass fluctuates by more than ±18% after processing, and the bonding gap between the glass and the OLED stack exceeds the design tolerance (>5μm), causing screen creases and optical distortion. Although the heat accumulation can be alleviated by reducing the energy of a single pulse through a multi-pass processing scheme, the processing time increases to 2.6 times that of the original process, and multiple positioning errors cause line segment position offsets of ≥3μm.

[0004] Therefore, in order to improve or solve at least one of the above problems, a method for laser micromachining deformation suppression of ultrathin flexible folding glass is provided. This method can reduce the thermal input error from ±15% to ±3%, improve the uniformity of energy distribution, help eliminate edge ablation defects, effectively reduce the width of the heat-affected zone, divide the glass substrate into millimeter-level micro-regions through stress optimization subdomain division, achieve staged temperature gradient release with delayed cooling strategy, reduce the residual stress peak to below 0.8MPa, simultaneously eliminate microcracks after cutting, improve the glass fracture toughness to 1.8MPa·m¹ / ², and combine hydrofluoric acid gradient etching technology to achieve nonlinear control of etching rate through concentration and time dual-variable regulation, so that the surface roughness Ra≤0.1μm, the deformation suppression rate of ultrathin glass exceeds 99%, the yield rate is stable at over 99.5%, and the processing cycle is shortened by 40%. Summary of the Invention

[0005] This invention addresses the aforementioned problems and aims to provide a method for reducing thermal input error from ±15% to ±3%, improving energy distribution uniformity, eliminating edge ablation defects, effectively reducing the width of the heat-affected zone, dividing the glass substrate into millimeter-level micro-regions through stress optimization subdomain partitioning, achieving staged temperature gradient release with a delayed cooling strategy, reducing residual stress peaks to below 0.8 MPa, simultaneously eliminating microcracks after cutting, increasing glass fracture toughness to 1.8 MPa·m¹ / ², and combining hydrofluoric acid gradient etching technology with nonlinear control of etching rate through concentration and time dual-variable regulation, achieving a surface roughness Ra≤0.1 μm, enabling deformation suppression rate of ultra-thin glass to exceed 99%, a yield rate stable above 99.5%, and a 40% reduction in processing cycle, while also being compatible with high-precision forming of complex irregular contours. This method provides a deformation suppression method for ultra-thin flexible foldable glass laser micromachining for next-generation foldable screen devices. To achieve the above objectives, the technical solution adopted by this invention is as follows: This invention provides a method for suppressing deformation during laser micromachining of ultrathin flexible folding glass, characterized by the following steps: step S1, dynamic capability modulation; step S2, parting path planning; and step S3, composite processing.

[0006] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by the present invention may also have the following features: Step S1 includes the following sub-steps: Step S1-1, establishing a line segment density and energy mapping model; Step S1-2, ring Gaussian beam shaping.

[0007] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by this invention may also have the following features: In step S1-1, the design pattern is imported into the laser control system, and the line segment distribution density of each region is automatically identified through an image analysis algorithm. According to a preset experimental database, the correspondence between density and energy is established. When the density is ≤500μm / mm², the laser power is set to 3W, the repetition frequency is 200kHz, and the scanning speed is 400mm / s. When the density is between 500μm / mm² and 1500μm / mm², the power is linearly increased to 5W, the frequency is increased to 350kHz, and the speed is reduced to 250mm / s. When the density is >1500μm / mm², the power is increased to 8W, the frequency is 500kHz, and the speed is adjusted to 150mm / s.

[0008] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by the present invention may also have the following feature: in steps S1-2, a beam shaping module combining a deformable mirror (DM) and an acousto-optic modulator (AOM) is used to convert the original flat-top spot with a diameter of 15μm into an annular spot with an outer diameter of 18μm and an inner diameter of 10μm.

[0009] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by the present invention may also have the following features: step S2 includes the following sub-steps: step S2-1, stress optimization subdomain division; step S2-2, delayed cooling strategy embedding.

[0010] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by the present invention may also have the following features: in step S2-1, the processing pattern is divided into multiple subdomains, and the stress release coefficient (SRC) of each subdomain is calculated by finite element simulation. Subdomains with SRC≥0.8 are processed first, and a spiral outward expansion path is adopted.

[0011] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by this invention may also have the following feature: in step S2-2, a dynamic delay (Δt) is inserted between adjacent line segments during processing, and its calculation formula is: Δt = d 2 / 4α+K ·(P avg / v), α=k / ρc p Where d is the line segment spacing (μm), α is the thermal diffusivity (0.8 mm² / s), K is the material constant (0.15 mS·mm / W), and P avgWhere is the average power (W), v is the scanning speed (mm / s), k is the thermal conductivity (W / (m·K)), ρ is the density (kg / m3), and c is the average power (W). p Specific heat capacity at constant pressure (J / (kg·K)).

[0012] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by the present invention may also have the following features: step S3 includes the following sub-steps: step S3-1, CO2 laser in-situ annealing; step S3-2, hydrofluoric acid gradient etching.

[0013] The method for suppressing deformation in ultrathin flexible folding glass laser micromachining provided by the present invention may also have the following feature: in step S3-1, within 10ms after the picosecond laser cutting is completed, a CO2 laser with a wavelength of 10.6μm (spot diameter of 50μm) is used to scan and anneal the cutting trajectory. The annealing parameters are: power density 1.2kW / cm², scanning speed 100mm / s, and spot overlap rate 30%.

[0014] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by this invention may also have the following feature: In step S3-2, the processed glass is placed in a sealed etching chamber, and a mixed gas of hydrofluoric acid (HF) and nitrogen (HF volume concentration of 6%) is introduced. The process is carried out in two stages. The parameters for the main etching stage are: temperature 25°C, pressure 100 kPa, time 40 s, removing approximately 1.2 μm of heat-affected zone; the parameters for the finishing stage are: temperature 18°C, pressure 50 kPa, time 20 s, reducing the HF concentration to 3%.

[0015] The technical effects of this invention are as follows: The deformation suppression method for ultra-thin flexible folding glass laser micromachining provided by this invention includes the following steps: Step S1, dynamic capability modulation; Step S2, parting path planning; Step S3, composite processing. Through the deformation suppression method for ultra-thin flexible folding glass laser micromachining provided by this invention, the thermal input error can be reduced from ±15% to ±3%, the uniformity of energy distribution can be improved, edge ablation defects can be eliminated, the width of the heat-affected zone can be effectively reduced, the glass substrate can be divided into millimeter-level micro-regions through stress optimization subdomain division, and the staged temperature gradient release can be achieved with the delayed cooling strategy, so that the residual stress peak is reduced to below 0.8MPa, microcracks can be eliminated simultaneously after cutting, and the glass fracture toughness can be increased to 1.8MPa·m¹ / ². At the same time, combined with hydrofluoric acid gradient etching technology, the etching rate can be nonlinearly controlled by concentration and time dual-variable regulation, so that the surface roughness Ra≤0.1μm, the deformation suppression rate of ultra-thin glass exceeds 99%, the yield rate is stable at over 99.5%, the processing cycle is shortened by 40%, and it can be compatible with high-precision forming of complex irregular contours. Attached Figure Description

[0016] This manual includes the following figures, which illustrate the following: Figure 1 This is a flowchart of the deformation suppression method for ultrathin flexible folding glass laser micromachining in an embodiment of the present invention; Figure 2 This is a schematic diagram of the outward expansion path of a subdomain in an embodiment of the present invention; Figure 3 This is a schematic diagram showing the overlap of the heat-affected zones of adjacent processing points in the prior art. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0018] Figure 1 This is a flowchart of a method for suppressing deformation in ultrathin flexible folding glass laser micromachining, as described in an embodiment of the present invention.

[0019] like Figure 1 As shown, the deformation suppression method for ultrathin flexible folding glass laser micromachining provided by this invention includes the following steps: Step S1, dynamic capability modulation; Step S2, parting path planning; Step S3, composite processing. Through this method, the thermal input error can be reduced from ±15% to ±3%, improving energy distribution uniformity, eliminating edge ablation defects, effectively reducing the width of the heat-affected zone, dividing the glass substrate into millimeter-level micro-regions through stress optimization subdomain division, and achieving staged temperature gradient release with a delayed cooling strategy, reducing the residual stress peak to below 0.8 MPa. Microcracks can be eliminated simultaneously after cutting, increasing the glass fracture toughness to 1.8 MPa·m¹ / ². Simultaneously, combined with hydrofluoric acid gradient etching technology, the etching rate is nonlinearly controlled through concentration and time dual-variable regulation, achieving a surface roughness Ra≤0.1 μm. This results in a deformation suppression rate exceeding 99% for ultrathin glass, a stable yield rate above 99.5%, a 40% reduction in processing cycle, and compatibility with high-precision forming of complex irregular contours.

[0020] Step S1 includes the following sub-steps: Step S1-1: Establish a line segment density and energy mapping model. In step S1-1, the design pattern is imported into the laser control system. The line segment distribution density in each region is automatically identified through an image analysis algorithm. Based on a preset experimental database, the correspondence between density and energy is established. When the density is ≤500μm / mm², the laser power is set to 3W, the repetition frequency to 200kHz, and the scanning speed to 400mm / s. When the density is between 500μm / mm² and 1500μm / mm², the power is linearly increased to 5W, the frequency to 350kHz, and the speed to 250mm / s. When the density is >1500μm / mm², the power is increased to 8W, the frequency to 500kHz, and the speed to 150mm / s. Simultaneously, the reflected light intensity change in the processing area is monitored in real time using a high-speed photoelectric sensor (sampling rate 10kHz), and the laser output power is adjusted accordingly (adjustment accuracy ±0.2W).

[0021] Step S1-2, Ring Gaussian Beam Shaping. In step S1-2, a beam shaping module combining a deformable mirror (DM) and an acousto-optic modulator (AOM) is used to convert the original flat-top beam spot with a diameter of 15μm into a ring beam spot with an outer diameter of 18μm and an inner diameter of 10μm. Among them, the deformable mirror can compensate for wavefront distortion during laser transmission and processing by actively adjusting the mirror morphology, optimizing the spot shape and energy distribution, thereby suppressing the deformation of glass caused by uneven energy; the acousto-optic modulator can adjust the intensity, pulse and deflection state of the laser at high speed and with precision through the acousto-optic effect, which can specifically solve the deformation problem caused by thermal effect. In step S1, the laser energy and processing path complexity are dynamically matched based on the line segment density-energy mapping model, reducing the thermal input error from ±15% of the traditional method to ±3%. Combined with the ring Gaussian beam shaping technology, the uniformity of energy distribution is improved by 90%, effectively eliminating edge ablation defects, and reducing the width of the heat-affected zone (HAZ) from 8μm to 2μm.

[0022] Step S2 includes the following sub-steps: Figure 2 This is a schematic diagram of the outward expansion path of a subdomain in an embodiment of the present invention.

[0023] Step S2-1, stress optimization subdomain division. In step S2-1, the processing pattern is divided into multiple subdomains, each a square mesh with a side length of 40mm. The stress release coefficient (SRC) of each subdomain is calculated using finite element simulation. Subdomains with SRC ≥ 0.8 are processed first, i.e., areas where stress is easily released, using a spiral outward expansion path, such as... Figure 2As shown, the spiral extends outward from A→B→C······→X→Y to avoid stress superposition in the central region.

[0024] Step S2-2, embedding the delayed cooling strategy. In step S2-2, a dynamic delay (Δt) is inserted between the processing intervals of adjacent line segments. The calculation formula is: Δt = d 2 / 4α+K ·(P avg / v), α=k / ρc p Where d is the line segment spacing (μm), α is the thermal diffusivity (0.8 mm² / s), K is the material constant (0.15 mS·mm / W), and P avg Where is the average power (W), v is the scanning speed (mm / s), k is the thermal conductivity (W / (m·K)), ρ is the density (kg / m3), and c is the average power (W). p The specific heat capacity at constant pressure is (J / (kg·K)). For example, when d=15μm, Pavg=4W, and v=300mm / s, Δt=1.2ms, ensuring sufficient heat dissipation. This allows the glass substrate to be divided into millimeter-level micro-regions in step S2 using a stress-optimized subdomain partitioning algorithm. Combined with a delayed cooling strategy, this achieves staged temperature gradient release, reducing the residual stress peak to below 0.8MPa, a 75% reduction compared to traditional processes.

[0025] Step S3 includes the following sub-steps: Step S3-1, CO2 laser in-situ annealing. In step S3-1, within 10 ms after the picosecond laser cutting is completed, a CO2 laser with a wavelength of 10.6 μm (spot diameter of 50 μm) is used to scan and anneal the cutting trajectory. Annealing parameters: power density 1.2 kW / cm², scanning speed 100 mm / s, spot overlap rate 30%. Under these conditions, a molten layer with a depth of 80 nm is formed on the glass surface, which blunts the microcrack tips and reduces the crack depth from 15 μm to ≤2 μm.

[0026] Step S3-2, hydrofluoric acid gradient etching. In step S3-2, the processed glass is placed in a sealed etching chamber, and a mixture of hydrofluoric acid (HF) and nitrogen (HF volume concentration of 6%) is introduced. The process is divided into two stages: the main etching stage parameters are: temperature 25℃, pressure 100kPa, time 40s, removing approximately 1.2μm of the heat-affected zone; the finishing stage parameters are: temperature 18℃, pressure 50kPa, time 20s, reducing the HF concentration to 3%, further smoothing the sidewalls. After this treatment, the chipping width is reduced from 8.5μm to 1.8μm, and the sidewall roughness Ra < 0.1μm. This allows the glass fracture toughness to be improved to 1.8MPa·m¹ / ² by introducing a carbon dioxide laser in-situ annealing module after cutting, simultaneously eliminating microcracks. Combined with hydrofluoric acid gradient etching technology, the etching rate is nonlinearly controlled through concentration-time dual-variable regulation, achieving a surface roughness Ra ≤ 0.1μm, which is 4 times more precise than conventional chemical etching processes.

[0027] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by this invention solves the deformation and edge chipping problems of ultrathin flexible glass laser cutting through energy gradient cutting, biomimetic path planning, and gas-solid coupling dynamic cooling synergy. It adopts a three-stage energy increment strategy of "pre-cutting-main cutting-edge trimming" (e.g., 8W→12W→15W), combined with elliptical Gaussian spot trimming to reduce thermal stress and microcracks; the cutting sequence is dynamically optimized based on stress field simulation, prioritizing the cutting of high-stress areas, and adding a 50μm to 100μm closed-loop backcut at the end to disperse residual stress; helium gas is injected behind the cutting point (flow rate 8L / min), combined with vacuum adsorption and infrared temperature control to achieve rapid heat dissipation (cooling rate >100℃ / s).

[0028] The laser processing head integrates an infrared picosecond laser (wavelength 1064nm), a CO2 laser module, and a real-time monitoring photoelectric sensor. The motion platform adopts a six-axis precision displacement stage (positioning accuracy ±0.5μm) and is equipped with a vibration suppression module (vibration reduction rate ≥90%). The control system uses an industrial PC with an adaptive algorithm to achieve millisecond-level dynamic response of processing parameters.

[0029] Taking 0.2mm thick sodium aluminum silicate glass as an example, a weakened pattern containing 1200 broken line segments within a 100×100mm² area is processed: deformation control, after adopting dynamic energy modulation, the overall curvature radius deviation of the glass is reduced from 22% to 4.5% (measured by laser interferometer); edge chipping suppression, the ring spot and etching work together to stabilize the edge chipping width at 1.5μm to 2.0μm; it is beneficial to improve production efficiency, fractal path planning reduces the processing time to 58% of the traditional process (originally 210 minutes, now optimized to 122 minutes). This invention significantly improves efficiency while ensuring processing accuracy through multi-technology coupling, and is suitable for mass production of ultra-thin flexible glass with a thickness of 0.1mm-0.3mm.

[0030] The deformation suppression method for ultrathin flexible folding glass laser micromachining provided by this invention includes the following steps: Step S1, dynamic capability modulation; Step S2, parting path planning; Step S3, composite processing. Through this method, the thermal input error can be reduced from ±15% to ±3%, improving energy distribution uniformity, eliminating edge ablation defects, effectively reducing the width of the heat-affected zone, dividing the glass substrate into millimeter-level micro-regions through stress optimization subdomain partitioning, and achieving staged temperature gradient release with a delayed cooling strategy, reducing the residual stress peak to below 0.8 MPa. Microcracks can be eliminated simultaneously after cutting, increasing the glass fracture toughness to 1.8 MPa·m¹ / ². Simultaneously, combined with hydrofluoric acid gradient etching technology, the etching rate is nonlinearly controlled through concentration and time dual-variable regulation, achieving a surface roughness Ra≤0.1 μm. This results in a deformation suppression rate exceeding 99% for ultrathin glass, a stable yield rate above 99.5%, a 40% reduction in processing cycle, and compatibility with high-precision forming of complex irregular contours.

[0031] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for suppressing deformation during laser micromachining of ultrathin flexible folding glass, characterized in that, Includes the following steps: Step S1, dynamic capability modulation; Step S2, fractal path planning; Step S3, composite processing.

2. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 1, characterized in that, Step S1 includes the following sub-steps: Step S1-1, establishing a line segment density and energy mapping model; Step S1-2, ring Gaussian beam shaping.

3. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 2, characterized in that, In step S1-1, the design pattern is imported into the laser control system. The line segment distribution density of each region is automatically identified by the image analysis algorithm. According to the preset experimental database, the correspondence between density and energy is established. When the density is ≤500μm / mm², the laser power is set to 3W, the repetition frequency is 200kHz, and the scanning speed is 400mm / s. When the density is between 500μm / mm² and 1500μm / mm², the power is linearly increased to 5W, the frequency is increased to 350kHz, and the speed is reduced to 250mm / s. When the density is >1500μm / mm², the power is increased to 8W, the frequency is 500kHz, and the speed is adjusted to 150mm / s.

4. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 2, characterized in that, In step S1-2, a beam shaping module combining a deformable mirror (DM) and an acousto-optic modulator (AOM) is used to convert the original flat-top beam spot with a diameter of 15μm into an annular beam spot with an outer diameter of 18μm and an inner diameter of 10μm.

5. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 1, characterized in that, Step S2 includes the following sub-steps: Step S2-1, stress optimization subdomain partitioning; Step S2-2, delayed cooling strategy embedding.

6. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 5, characterized in that, In step S2-1, the processing pattern is divided into multiple subdomains, and the stress release coefficient (SRC) of each subdomain is calculated by finite element simulation. Subdomains with SRC ≥ 0.8 are processed first, and a spiral outward expansion path is adopted.

7. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 5, characterized in that, In step S2-2, a dynamic delay (Δt) is inserted between the processing intervals of adjacent line segments. The calculation formula is: Δt = d 2 / 4α+K·(P avg / v), α=k / ρc p Where d is the line segment spacing (μm), α is the thermal diffusivity (0.8 mm² / s), K is the material constant (0.15 mS·mm / W), and P avg Where is the average power (W), v is the scanning speed (mm / s), k is the thermal conductivity (W / (m·K)), ρ is the density (kg / m3), and c is the average power (W). p Specific heat capacity at constant pressure (J / (kg·K)).

8. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 1, characterized in that, Step S3 includes the following sub-steps: Step S3-1, CO2 laser in-situ annealing; Step S3-2, hydrofluoric acid gradient etching.

9. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 8, characterized in that, In step S3-1, within 10ms after the picosecond laser cutting is completed, a CO2 laser with a wavelength of 10.6μm (spot diameter of 50μm) is used to scan and anneal the cutting trajectory. The annealing parameters are: power density 1.2kW / cm², scanning speed 100mm / s, and spot overlap rate 30%.

10. The method for suppressing deformation during laser micromachining of ultrathin flexible folding glass according to claim 8, characterized in that, In step S3-2, the processed glass is placed in a sealed etching chamber, and a mixture of hydrofluoric acid (HF) and nitrogen (HF volume concentration of 6%) is introduced. The process is carried out in two stages. The parameters for the main etching stage are: temperature 25°C, pressure 100 kPa, time 40 s, removing approximately 1.2 μm of heat-affected zone. The parameters for the finishing stage are: temperature 18°C, pressure 50 kPa, time 20 s, reducing the HF concentration to 3%.

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