A method for preparing a glass countersunk hole based on partition laser-induced modification

Abstract

The application relates to the technical field of laser processing, in particular to a glass countersunk hole preparation method based on partition laser-induced modification, which comprises the following steps: S1, shaping a Gaussian light beam emitted by a laser into a Bessel light beam; S2, setting laser processing parameters as high pulse energy, large pulse width and multiple pulse numbers, performing laser-induced modification on a glass substrate to form a first modification zone penetrating the thickness direction of the glass substrate; S3, setting laser processing parameters as low pulse energy, small pulse width and few pulse numbers, performing laser-induced modification on the glass substrate to form a second modification zone surrounding the upper periphery of the first modification zone; and S4, integrally forming a countersunk hole on the glass substrate through one-step wet etching. According to the application, step-by-step processing, mask plate manufacturing and complex tooling are not needed, the straight-through hole area and the conical countersunk hole area of the countersunk hole are synchronously formed in a single etching process, the process flow is greatly simplified, and the processing efficiency and the processing yield are improved.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, and specifically to a method for preparing glass countersunk holes based on partitioned laser-induced modification. Background Technology

[0002] Glass, due to its high transparency, chemical stability, and high electrical insulation, is widely used in optical communication, microelectronic packaging, biomedicine, and high-end displays. Countersunk glass holes, combining an upper tapered countersunk hole and a lower through hole, are key structures for achieving fiber optic guided assembly, interlayer vertical interconnection, precise fluid docking, and countersunk installation. Current mainstream processing methods for countersunk glass holes include mechanical drilling, direct laser ablation, and traditional laser-induced wet etching. Mechanical drilling requires first machining a through hole and then using a tapered tool to machine the countersunk hole. During this process, brittle glass is prone to chipping, breakage, and microcracks. Sub-millimeter-level micro-hole machining has poor precision and low yield, making it difficult to meet the requirements of high-precision devices. Direct laser ablation relies on high-energy lasers to directly vaporize and remove glass material. This results in a large heat-affected zone, and the hole walls are prone to recast layers and microcracks, with surface roughness exceeding 1μm, failing to meet optical-grade processing standards. Traditional laser-induced wet etching uses a step-by-step processing method to form a composite structure with a conical top and a straight bottom. This method is prone to problems such as hole-axis misalignment, connection steps, and morphological distortion. It also suffers from drawbacks such as complex process flow, poor processing consistency, and low efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing glass countersunk holes based on partitioned laser-induced modification, which can at least solve some of the defects in the prior art.

[0004] To achieve the above objectives, the technical solution of the present invention is a method for preparing glass countersunk holes based on partitioned laser-induced modification, comprising the following steps:

[0005] S1. Shape the Gaussian beam emitted by the laser into a Bessel beam;

[0006] S2. Adjust the height of the laser processing head so that the glass cover plate to be processed is completely within the focal depth range of the Bessel beam; set the laser processing parameters to high pulse energy, large pulse width and multiple pulses to perform laser-induced modification on the glass substrate and form the first modification zone that runs through its thickness direction.

[0007] S3. Adjust the height of the laser processing head so that the upper surface and the shallow area below the glass cover to be processed are within the focal depth of the Bessel beam; set the laser processing parameters to low pulse energy, small pulse width and few pulses to perform laser-induced modification on the glass substrate to form a second modification area surrounding the upper periphery of the first modification area.

[0008] S4. Place the glass substrate in the etching solution and perform a one-step wet etching process to integrally form a countersunk hole with a tapered countersunk hole area at the top and a through hole area at the bottom on the glass substrate.

[0009] As one implementation method, the large pulse width is 5ps to 15ps, and the number of multiple pulses is 5 to 10; the small pulse width is 200fs to 2ps, and the number of fewer pulses is 1 to 3; the low pulse energy is 0.4 to 0.7 times the high pulse energy.

[0010] As one implementation method, with the central axis of the target countersunk hole as the reference axis, the scanning path of the Bessel beam in step S2 is a circle with the intersection of the reference axis and the upper surface of the glass substrate as the center, and the scanning path of the Bessel beam in step S3 is at least one concentric circle with the intersection of the reference axis and the upper surface of the glass substrate as the center.

[0011] As one implementation method, when the diameter of the through-hole area of ​​the target countersunk hole is not much different from the upper diameter of the conical countersunk hole area, the scanning path of the Bessel beam in step S3 is a circle; when the diameter of the through-hole area of ​​the target countersunk hole is much different from the upper diameter of the conical countersunk hole area, the scanning path of the Bessel beam in step S3 is multiple concentric circles, and the radial distance between adjacent concentric circles is 50μm~150μm.

[0012] As one implementation method, the following steps are also included between steps S3 and S4: lowering the height of the laser processing head so that the lower surface and the shallow area above it of the glass cover to be processed are within the focal depth range of the Bessel beam; setting the laser processing parameters to low pulse energy, small pulse width and few pulses to laser induce the glass substrate to form a third modified area surrounding the lower periphery of the first modified area; in step S4, a countersunk hole with tapered countersunk hole areas at both ends and a through hole area in the middle is integrally formed on the glass substrate.

[0013] As one implementation method, the following steps are included before step S1: first, remove the floating dust and debris from the surface of the glass substrate, then place the glass substrate in anhydrous ethanol for ultrasonic cleaning, then transfer it to deionized water for ultrasonic cleaning, then dry it, cool it to room temperature, and then fix it on the laser processing platform.

[0014] As one implementation method, in step S1, the laser is an infrared ultrafast laser with a working wavelength of 1030nm~1064nm and a pulse width of femtosecond to picosecond.

[0015] As one implementation method, in step S1, the Gaussian beam emitted by the laser is sequentially shaped by a half-wave plate, a polarizing beam splitter, a continuously adjustable attenuator, a high-speed electronic shutter, a beam expander group, a conical lens, and an objective lens to form a Bessel beam.

[0016] As one implementation method, in step S4, the etching solution is an HF solution with a mass concentration of 5wt%~20wt% and a temperature of 20℃~40℃.

[0017] As one implementation method, in step S4, ultrasonic assistance is used during the etching process, and the frequency of the ultrasonic wave is 28kHz~40kHz.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) This invention forms a first modified region with a high corrosion rate, extending from top to bottom, by placing the glass cover plate to be processed entirely within the focal depth of the Bessel beam and using a laser with high pulse energy, large pulse width, and multiple pulses to perform full-thickness penetration modification on the glass substrate; by placing the upper surface and the shallow area below the glass cover plate to be processed within the focal depth of the Bessel beam and using a laser with low pulse energy, small pulse width, and few pulses to perform shallow-depth limited modification on the glass substrate, a second modified region with a low corrosion rate surrounding the upper periphery of the first modified region is formed on the glass substrate; finally, the first modified region is used to perform the modification. Due to the different etching rates of the modified and second modified regions, a one-step wet etching process is used to rapidly etch and penetrate the first modified region along the thickness direction, forming a vertical, smooth, and high aspect ratio lower through-hole region. The second modified region expands simultaneously in the horizontal and vertical directions in the upper shallow region of the glass substrate, naturally forming an upper conical countersunk hole region with a large upper opening and a small lower opening and a smooth transition. This allows for the integrated formation of a countersunk hole on the glass substrate, with a conical countersunk hole region at the top and a through-hole region at the bottom. This eliminates the need for step-by-step processing, mask making, and complex tooling. Furthermore, the through-hole region and the conical countersunk hole region of the countersunk hole are formed simultaneously in a single etching process, greatly simplifying the process flow and improving processing efficiency and yield.

[0020] (2) In this invention, the central axis of the target countersunk hole is used as the reference axis. The scanning path of the Bessel beam during the processing of the first modification zone and the second modification zone is a circle with the intersection of the reference axis and the upper surface of the glass substrate as the center. This ensures that the upper conical countersunk hole area and the lower through hole area of ​​the countersunk hole are manufactured in a coaxial and integrated manner without misalignment, thus avoiding hole axis misalignment. When the diameter of the through hole area of ​​the target countersunk hole is significantly different from the upper diameter of the conical countersunk hole area, the scanning path of the Bessel beam during the processing of the second modification zone is multiple concentric circles to ensure the smooth formation of the upper conical countersunk hole area and the seamless connection and stepless connection between the through hole area and the conical countersunk hole area.

[0021] (3) The method of the present invention can prepare countersunk holes with one end being conical or both ends being conical, and the processing yield is not less than 98%. The hole shape has high consistency, no misalignment, and no distortion, making it suitable for industrial mass production. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart of a glass countersunk hole preparation method based on partitioned laser-induced modification provided in an embodiment of the present invention;

[0024] Figure 2 This is a cross-sectional schematic diagram of the first modified region formed in step S2 of the present invention.

[0025] Figure 3 This is a cross-sectional schematic diagram of the second modified region formed in step S3 of an embodiment of the present invention;

[0026] Figure 4 A cross-sectional schematic diagram of the countersunk hole formed in step S3 of this embodiment of the invention;

[0027] Figure 5 A schematic diagram comparing the focal depth of a Bessel beam and a Gaussian beam provided in an embodiment of the present invention (the top is the Bessel beam, and the bottom is the Gaussian beam). Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] like Figures 1-4 As shown, this embodiment provides a method for preparing glass countersunk holes based on partitioned laser-induced modification, including the following steps:

[0032] S1. Shape the Gaussian beam emitted by the laser into a Bessel beam;

[0033] S2. Adjust the height of the laser processing head so that the glass cover plate to be processed is completely within the focal depth range of the Bessel beam; set the laser processing parameters to high pulse energy, large pulse width and multiple pulses to perform laser-induced modification on the glass substrate and form the first modification zone that runs through its thickness direction.

[0034] S3. Adjust the height of the laser processing head so that the upper surface and the shallow area below the glass cover to be processed are within the focal depth of the Bessel beam; set the laser processing parameters to low pulse energy, small pulse width and few pulses to perform laser-induced modification on the glass substrate to form a second modification area surrounding the upper periphery of the first modification area.

[0035] S4. Place the glass substrate in the etching solution and perform a one-step wet etching process to integrally form a countersunk hole with a tapered countersunk hole area at the top and a through hole area at the bottom on the glass substrate.

[0036] This embodiment achieves deep modification of the glass substrate by placing the glass cover plate to be processed entirely within the focal depth of the Bessel beam and using a high-pulse-energy, large-pulse-width, and high-pulse-number laser to penetrate the entire thickness of the glass substrate, thereby forming a first modification zone with a high corrosion rate that extends from top to bottom through the entire thickness of the glass substrate. Then, by placing the upper surface and the shallow area below the glass cover plate to be processed within the focal depth of the Bessel beam and using a low-pulse-energy, small-pulse-width, and low-pulse-number laser to perform a shallow, limited-depth gentle modification of the glass substrate, a second modification zone with a low corrosion rate surrounding the upper periphery of the first modification zone is formed on the glass substrate. Finally, the first modification zone is utilized... Due to the different etching rates of the first modified area and the second modified area, a one-step wet etching process is used to rapidly etch and penetrate the first modified area along the thickness direction, forming a vertical, smooth, high aspect ratio lower through-hole area. The second modified area expands horizontally and vertically simultaneously in the upper shallow region of the glass substrate, naturally forming an upper conical countersunk hole area with a large upper opening and a small lower opening and a smooth transition. Thus, a countersunk hole with a conical countersunk hole area at the top and a through-hole area at the bottom is integrally formed on the glass substrate, eliminating the need for step-by-step processing, mask making, and complex tooling. Moreover, the through-hole area and the conical countersunk hole area of ​​the countersunk hole are formed simultaneously in a single etching process, which greatly simplifies the process flow and improves processing efficiency and yield.

[0037] In this embodiment, high-pulse-energy, large-pulse-width, and high-pulse-number lasers can induce multiphoton absorption-induced nonlinear modification of the glass substrate, forming a dense and uniform modified structure inside the glass. This significantly improves the response rate of the first modified region to the etching solution, providing a foundation for subsequent rapid etching to form a through-hole region. Low-pulse-energy, small-pulse-width, and low-pulse-number lasers only induce mild, selective, and low-damage modification on the glass surface, without generating cracks or recast layers. Their response rate to the etching solution is significantly lower than that of the first modified region. By inducing differentiated zoning through dual-laser processing parameters, a controllable and stable differential corrosion rate zone between the inside and outside of the glass is constructed, providing a foundation for one-step etching with rapid penetration at the center and slow cone formation at the periphery.

[0038] In some embodiments, the large pulse width is 5 ps to 15 ps, and the number of multiple pulses is 5 to 10; the small pulse width is 200 fs to 2 ps, and the number of fewer pulses is 1 to 3; the low pulse energy is 0.4 to 0.7 times the high pulse energy. By controlling the pulse energy, pulse width, and number of pulses in steps S2 and S3, a stable, controllable, and significant corrosion rate difference can be formed between the first modified region and the second modified region.

[0039] Furthermore, using the central axis of the target countersunk hole as the reference axis, the scanning path of the Bessel beam in step S2 is a circle centered at the intersection of the reference axis and the upper surface of the glass substrate, and the scanning path of the Bessel beam in step S3 is at least one concentric circle centered at the intersection of the reference axis and the upper surface of the glass substrate. In this embodiment, a processing coordinate system is established using the central axis of the target countersunk hole as the coaxial reference axis to ensure that the scanning paths of the Bessel beam in step S2 and step S3 are strictly coaxial, thereby making the first modification zone and the second modification zone completely coaxial. This ensures that the upper conical countersunk hole area and the lower through hole area of ​​the countersunk hole are manufactured coaxially and integrally without misalignment, avoiding hole axis misalignment. In step S2, the Bessel beam scans a circle with the intersection of the reference axis and the upper surface of the glass substrate as the center, and the scanning radius is the design radius of the through hole area of ​​the target countersunk hole; in step S3, the Bessel beam scans a circle with a larger diameter with the intersection of the reference axis and the upper surface of the glass substrate as the center, and the scanning radius of the largest circle is the upper opening design radius of the conical countersunk hole area of ​​the target countersunk hole.

[0040] Furthermore, when the diameter of the through-hole area of ​​the target countersunk hole is not significantly different from the upper diameter of the conical countersunk hole area, the scanning path of the Bessel beam in step S3 is a circle; when the diameter of the through-hole area of ​​the target countersunk hole differs significantly from the upper diameter of the conical countersunk hole area, the scanning path of the Bessel beam in step S3 consists of multiple concentric circles, with a radial distance of 50μm to 150μm between adjacent concentric circles. In this embodiment, the number of concentric circles in the scanning path of the Bessel beam in step S3 depends on the difference between the diameter of the through-hole area and the upper diameter of the conical countersunk hole area; the larger the difference, the more concentric circles there are. The radial distance between adjacent concentric circles is 50μm to 150μm to ensure the smooth formation of the upper conical countersunk hole area and the seamless connection and stepless connection between the through-hole area and the conical countersunk hole area.

[0041] In some embodiments, the following steps are also included between steps S3 and S4: lowering the height of the laser processing head so that the shallow area above the lower surface of the glass cover to be processed is within the focal depth range of the Bessel beam; setting the laser processing parameters to low pulse energy, small pulse width and few pulses to laser-induce the glass substrate to form a third modified area surrounding the lower periphery of the first modified area; in step S4, a countersunk hole with tapered countersunk hole areas at both ends and a through hole area in the middle is integrally formed on the glass substrate. By placing the shallow region above the lower surface of the glass cover plate to be processed within the focal depth range of the Bessel beam, and using a laser with low pulse energy, small pulse width, and few pulses to perform a shallow, limited-depth, and gentle modification on the glass substrate, a third modification region with a low corrosion rate is formed on the glass substrate, surrounding the lower periphery of the first modification region. In a one-step wet etching process, the third modification region expands horizontally and vertically synchronously in the lower shallow region of the glass substrate, naturally forming a lower tapered countersunk hole region with a small upper opening, a large lower opening, and a smooth transition. This allows for the integrated formation of a countersunk hole on the glass substrate with tapered countersunk hole regions at both ends and a through hole region in the middle. This eliminates the need for step-by-step processing, tool changes, mask making, and complex optical path adjustments. The composite hole can be formed in a single etching process, improving the overall processing efficiency by more than 50% compared to traditional methods.

[0042] In this embodiment, the height of the laser processing head is precisely adjusted by the Z-axis servo motion system, thereby adjusting the overlap area between the focal depth range of the Bessel beam and the glass cover plate to be processed in the thickness direction, thus achieving modification of the glass substrate to different thicknesses. When the glass cover plate to be processed is completely within the focal depth range of the Bessel beam, a first modification zone is formed that extends continuously from the upper surface to the lower surface of the glass cover plate, with no breaks or weak areas. When the upper surface and the shallow layer below the glass cover plate to be processed are within the focal depth range of the Bessel beam, a second modification zone is formed that extends downward from the upper surface of the glass cover plate to a certain thickness, no longer penetrating the substrate thickness. When the lower surface and the shallow layer above the glass cover plate to be processed are within the focal depth range of the Bessel beam, a third modification zone is formed that extends upward from the lower surface of the glass cover plate to a certain thickness, no longer penetrating the substrate thickness. The modification depth of the second and third modification zones is linearly and precisely controlled by the Z-axis displacement Δh of the laser processing head, with a control range of 50μm to 500μm and a depth control accuracy of no less than ±2μm. It can be flexibly set according to product requirements.

[0043] In some embodiments, the following steps are included before step S1: first, remove dust and debris from the surface of the glass substrate; then, immerse the glass substrate in anhydrous ethanol for ultrasonic cleaning; subsequently, transfer it to deionized water for ultrasonic cleaning; then, dry it; and finally, fix it on the laser processing platform after cooling to room temperature. In this embodiment, the glass substrate is selected as a double-sided polished, bubble-free, and scratch-free optical-grade glass substrate. Dust and debris can be removed by blowing the surface of the glass substrate with a high-pressure nitrogen gun. During cleaning, the glass substrate is first immersed in anhydrous ethanol for ultrasonic cleaning to remove grease, organic residues, and processing stains from the surface of the glass substrate. Preferably, the cleaning time is about 10 minutes, and the ultrasonic frequency is about 40kHz. Then, it is transferred to deionized water for ultrasonic cleaning to thoroughly wash away ethanol residues and inorganic ions, avoiding residues from affecting the uniformity of modification. Preferably, the cleaning time is about 10 minutes. After cleaning, the glass substrate is placed in a constant temperature oven and dried at 70°C for 15 minutes. After cooling to room temperature, the substrate is fixed on the laser processing platform. The glass substrate can be fixed on a three-axis high-precision laser processing platform by vacuum adsorption, ensuring that the flatness of the clamping is no more than 3μm and the positioning accuracy of the X / Y / Z axes is no more than ±0.5μm, ensuring that there is no slippage, warping, or vibration during the processing.

[0044] Furthermore, in step S1, an infrared ultrafast laser is used, with a working wavelength of 1030nm~1064nm, a pulse width of femtosecond to picosecond, and an output power of 0~60W. In this embodiment, an infrared ultrafast laser is used as the processing light source, and the repetition rate, pulse energy, and output power can all be adjusted in multiple levels. After shaping, the infrared ultrafast laser forms a Bessel beam with uniform axial distribution, no diffraction, and long focal depth, which can achieve nonlinear optical modification inside the glass. This results in uniform, stable, and low-damage modification within the glass, avoiding surface ablation and heat-affected zones, as well as the defects of traditional Gaussian beams such as short focal length, uneven modification, and susceptibility to thermal damage.

[0045] Further, in step S1, the Gaussian beam emitted by the laser is sequentially shaped by a half-wave plate, a polarizing beam splitter, a continuously adjustable attenuator, a high-speed electronic shutter, a beam expander group, a conical lens, and an objective lens to form a Bessel beam. Specifically, adjusting the rotation angle of the half-wave plate can control the laser beam to a stable linear polarization state, matching the polarization direction with the optical path transmission, improving energy utilization and modification consistency. Then, through the coordinated adjustment of the polarizing beam splitter and the continuously adjustable attenuator, the output power can be continuously and precisely adjusted, ensuring accurate control of the modification energy density in different regions. Next, the beam expander group can enlarge the original beam diameter to 8mm to 12mm, ensuring the beam completely fills the effective aperture of the conical lens, guaranteeing a thin main lobe, flat focal depth, and good side lobe suppression in the shaped Bessel beam. Finally, through the axial refraction of the conical lens and the focusing effect of the objective lens, the Gaussian beam is shaped into a diffraction-free, long-focal-depth, and highly axially uniform Bessel beam. Figure 5 As shown, this ensures that the Bessel beam remains unchanged and its diameter does not change over a long distance along the glass thickness direction, providing a foundation for deep modification that penetrates the entire thickness. In this embodiment, the air focal depth after the Bessel beam is focused is mainly determined by the cone angle of the conical lens and the focusing lens in the optical path. A suitable Bessel optical path with an appropriate focal depth can be matched according to the actual thickness of the glass substrate being processed. By controlling the linkage between the high-speed electronic shutter and the three-axis high-precision laser processing platform, the Bessel beam is controlled to modify the glass substrate according to the designed scanning path.

[0046] This embodiment employs a coaxial CCD imaging system to acquire the focal line morphology of the beam in real time, monitor the straightness of the Bessel beam focal line, the stability of the central light intensity, and the depth of focus, ensuring that the beam is free from distortion and deviation. At the same time, the laser processing platform is geometrically calibrated and its perpendicularity is corrected. With the upper surface of the glass substrate as the Z-axis reference zero point, the coaxiality error between the beam axis and the platform motion axis is guaranteed to be no greater than ±1μm, providing positioning assurance for dual-region coaxial modification. After the optical path is debugged, the attitude of all optical components is locked to avoid optical path drift during processing and ensure consistency in batch processing.

[0047] Furthermore, in step S4, the etching solution is an HF solution with a mass concentration of 5wt%~20wt% and a temperature of 20℃~40℃. Preferably, the mass concentration of the HF solution is 10wt%~15wt%, and a trace amount of corrosion inhibitor can be added to improve the smoothness of the hole wall.

[0048] Furthermore, in step S4, ultrasonic assistance is used during the etching process, with the ultrasonic frequency ranging from 28 kHz to 40 kHz. By using ultrasonic assistance during the etching process, etching byproducts can be rapidly removed, avoiding rough hole walls and localized over-etching.

[0049] After step S4 in this embodiment, the following steps are also included: after etching is completed, the glass substrate is quickly rinsed with a large amount of deionized water to terminate the reaction, and then dried with nitrogen gas.

[0050] This embodiment employs an ultrafast laser cold processing method, resulting in a process free of edge chipping, microcracks, and recast layers. The hole wall roughness is no higher than 0.1 μm, achieving optical-grade ultra-precision machining standards. Furthermore, the hole depth, taper, and diameter of the through-hole area in the countersunk hole can be linearly and precisely controlled through laser processing parameters and the height of the laser processing head. This allows for a wide adjustment range, good repeatability, and rapid adaptation to customized processing needs in different scenarios. The preparation method of this embodiment is applicable to glass substrates such as quartz glass, borosilicate glass, and soda-lime glass, and is particularly suitable for hard and brittle optical glasses such as high-purity quartz (JGS1 / JGS2) and high borosilicate glass (Pyrex).

[0051] The preparation method of the present invention will be described in detail below through two examples.

[0052] Example 1: Quartz glass countersunk hole (for fiber optic ferrule)

[0053] In this embodiment, a 500μm thick JGS1 high-purity quartz glass is used as the processing substrate. This glass is an optically grade material that is double-sided optically polished, bubble-free, and scratch-free. Before processing, the surface of the glass substrate is first purged with a high-pressure nitrogen gun to remove surface dust and loose impurities. Then, the glass substrate is sequentially immersed in anhydrous ethanol and deionized water, and cleaned under ultrasonic conditions at 40kHz for 10 minutes each to thoroughly remove surface oil, organic residues, and inorganic ions. After cleaning, the glass substrate is dried in a 70℃ constant temperature oven for 15 minutes. After cooling to room temperature, it is fixed to a three-axis high-precision laser processing platform using vacuum adsorption, ensuring that the clamping flatness is no greater than 3μm and that there is no slippage, warping, or vibration during processing.

[0054] The processing light source uses an infrared femtosecond laser with a working wavelength of 1030nm. After the laser is emitted, it passes sequentially through a half-wave plate, a polarizing beam splitter, a continuously adjustable attenuator, a high-speed electronic shutter, a beam expander group, a conical lens, and an objective lens. Through optical path adjustment, the Gaussian beam is shaped into a Bessel beam with no diffraction and a long focal depth. The focal depth of the Bessel beam is 1mm. During the adjustment process, the beam shape is monitored in real time through a coaxial CCD imaging system to ensure that the focal line is straight, the energy distribution is uniform, there is no distortion, and there is no offset. The Z-axis zero point is calibrated with the upper surface of the glass as a reference to ensure that the coaxiality error between the beam axis and the platform motion axis is no more than 1μm.

[0055] After completing the optical path debugging, the first modification zone is prepared. First, the height of the laser processing head is precisely adjusted by the Z-axis servo motion system so that the focal depth of the Bessel beam completely penetrates the entire thickness of the glass substrate. Then, with the central axis of the target countersunk hole as the reference axis, a circular scanning path is executed with a diameter of Φ50μm. Laser processing parameters of 130uJ single pulse energy, 5ps pulse width, and 5 pulses are used to irradiate and modify the upper surface of the glass substrate, so that a central annular first modification zone with a continuous, dense structure and high corrosion rate is formed inside the glass from the upper surface to the lower surface.

[0056] After completing the center modification, keeping the coaxial reference axis and processing coordinate system unchanged, the height of the laser processing head is precisely adjusted upward again through the Z-axis servo motion system, so that only the upper surface of the glass substrate and the upper 150μm shallow layer are within the focal depth of the Bessel beam. The focal depth of the Bessel beam does not penetrate the overall thickness of the glass substrate. Then, a larger diameter annular large circle scanning path is executed around the first modification area. The diameter of this circle is determined by the size of the upper aperture of the upper conical countersunk hole area. The circle diameter is Φ208μm. The laser processing parameters are switched to a single pulse energy of 70μJ, a pulse width of 500fs, and a number of pulses of 2 to irradiate the upper surface of the glass substrate in a shallow layer, forming a shallow annular second modification area that is completely coaxial with the first modification area in the center but has a lower corrosion rate.

[0057] The glass substrate, after undergoing dual-region coaxial modification, was immersed in a 10wt% HF solution and wet-etched at a constant temperature of 30℃ with 40kHz ultrasonic field assistance for 2 hours. During etching, the first modified region, with a high corrosion rate at the center, was rapidly etched along the glass thickness and completely penetrated, forming a vertically smooth through-hole region with a diameter of approximately 126μm. The second modified region, with a shallower corrosion rate at the periphery, slowly expanded in the upper part of the glass, naturally forming a conical countersunk hole region with an upper diameter of approximately 300μm and a depth of 150μm. After etching, the glass substrate was quickly rinsed with a large amount of deionized water to terminate the reaction and dried with nitrogen gas. Finally, a one-step process was used to obtain a coaxial, seamless, stepless, and axially misaligned integrated countersunk hole. Testing showed that the hole wall roughness Ra of the countersunk hole was as low as 0.08μm, achieving optical-grade surface quality, with a processing yield of 98.5%. There were no chipped edges, microcracks, or recast layers, fully meeting the high-precision assembly requirements of fiber optic ferrules.

[0058] Example 2: Borosilicate glass countersunk via (for TGV substrate)

[0059] In this embodiment, Pyrex borosilicate glass with a thickness of 2750 μm was selected as the processing substrate. This glass has good chemical stability and mechanical strength, making it suitable for TGV glass through-hole substrates in the microelectronic packaging field. Before processing, the glass was pretreated according to the standard optical component cleaning process. First, the surface of the glass substrate was purged with a nitrogen gun. Then, the glass substrate was sequentially immersed in anhydrous ethanol and deionized water, and cleaned under ultrasonic conditions at 40 kHz for 10 minutes each to thoroughly remove surface oil, organic residues, and inorganic ions. Subsequently, the glass substrate was placed in a 70°C constant temperature oven to dry for 15 minutes. After cooling to room temperature, it was fixed to a three-axis high-precision laser processing platform by vacuum adsorption to ensure stable and reliable processing position.

[0060] An infrared femtosecond laser with a working wavelength of 1030 nm was used as the modification light source. After emission, the laser beam passed sequentially through a half-wave plate, a polarizing beam splitter, a continuously adjustable attenuator, a high-speed electronic shutter, a beam expander group, a conical lens, and an objective lens. Through optical path adjustment, the Gaussian beam was shaped into a Bessel beam with diffraction-free characteristics and a long depth of focus (3 mm). Optical path calibration, beam quality testing, and platform coaxiality calibration were performed to ensure that the beam had uniform, stable, and distortion-free modification capabilities along the glass thickness direction.

[0061] The first modified area is prepared by precisely adjusting the height of the laser processing head through the Z-axis servo motion system so that the focal depth of the Bessel beam completely covers the full thickness of the glass substrate. Using the central axis of the target countersunk hole as the reference axis, a central circular scan is performed with a circle diameter of Φ75μm. Laser processing parameters of 1.2mJ single pulse energy, 8ps pulse width, and 5 pulses are used to irradiate and modify the upper surface of the glass substrate, so that a central annular first modification with a full thickness penetration and high corrosion rate is formed inside the glass, which provides the basis for the subsequent formation of the through hole area.

[0062] While keeping the coaxial reference axis and processing coordinate system unchanged, the height of the laser processing head is precisely adjusted upward through the Z-axis servo motion system so that only the upper surface of the glass substrate and the upper 300μm shallow layer area are within the focal depth of the Bessel beam. Then, a circular scanning path is executed around the first modification area. The upper surface of the glass substrate is shallowly modified using laser processing parameters with a single pulse energy of 600μJ, a pulse width of 2ps, and a number of pulses of 3, forming a shallow annular second modification area that is completely coaxial with the central first modification area but has a lower corrosion rate.

[0063] The glass substrate, after undergoing dual-region coaxial modification, was immersed in a 15wt% HF etching solution and subjected to ultrasonic-assisted etching at a constant temperature of 35°C with a 40kHz ultrasonic field for approximately 6 hours. Under the action of the etching solution, the first modified region with a high corrosion rate in the center rapidly penetrated and formed a vertically smooth through-hole region with a diameter of approximately 150μm. Simultaneously, the second modified region with a shallower corrosion rate on the periphery was etched and expanded, forming a conical countersunk hole region with an upper diameter of approximately 400μm and a depth of 300μm. After etching, the glass substrate was quickly rinsed with a large amount of deionized water to terminate the reaction and dried with nitrogen gas. Finally, a coaxial, seamless, stepless, and axially misaligned integrated countersunk hole was formed in one step.

[0064] The completed samples were tested and found to have complete hole structures, high coaxiality, smooth and defect-free hole walls, no cracks, no distortion, and no connecting steps. The processing yield can reach 97.8%, which can meet the high precision and high reliability requirements of TGV glass through-hole substrates for interlayer vertical interconnection and high-density wiring in microelectronic packaging.

[0065] This invention is based on the nonlinear modification of infrared femtosecond lasers and the non-diffraction long focal depth characteristics of Bessel beams. It adopts a laser-induced modification strategy with coaxial dual zones, dual parameters, dual depths, and dual scanning paths. First, the Gaussian beam is converted into a long focal depth Bessel beam through optical path shaping. Then, through two-level precise control of the Z-axis height, the glass substrate is modified by the central circular penetration modification and the outer large circular shallow layer modification in sequence. The first and second modification zones with significantly different corrosion rates and coaxiality are constructed inside the glass. Finally, the corrosion rate difference effect of single-step wet etching is used to simultaneously realize the penetration of the lower through hole area and the formation of the upper conical countersunk hole area. The final result is a coaxial, misalignment-free, step-free glass countersunk hole integrated structure with optical-grade surface quality.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing glass countersunk holes based on partitioned laser-induced modification, characterized in that, Includes the following steps: S1. Shape the Gaussian beam emitted by the laser into a Bessel beam; S2. Adjust the height of the laser processing head so that the glass cover plate to be processed is completely within the focal depth range of the Bessel beam; set the laser processing parameters to high pulse energy, large pulse width and multiple pulses to perform laser-induced modification on the glass substrate and form the first modification zone that runs through its thickness direction. S3. Adjust the height of the laser processing head so that the upper surface and the shallow area below the glass cover to be processed are within the focal depth of the Bessel beam; set the laser processing parameters to low pulse energy, small pulse width and few pulses to perform laser-induced modification on the glass substrate to form a second modification area surrounding the upper periphery of the first modification area. S4. Place the glass substrate in the etching solution and perform a one-step wet etching process to integrally form a countersunk hole with a tapered countersunk hole area at the top and a through hole area at the bottom on the glass substrate.

2. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that: The large pulse width is 5ps to 15ps, and the number of multiple pulses is 5 to 10; the small pulse width is 200fs to 2ps, and the number of fewer pulses is 1 to 3; the low pulse energy is 0.4 to 0.7 times that of the high pulse energy.

3. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that: With the central axis of the target countersunk hole as the reference axis, the scanning path of the Bessel beam in step S2 is a circle with the intersection of the reference axis and the upper surface of the glass substrate as the center, and the scanning path of the Bessel beam in step S3 is at least one concentric circle with the intersection of the reference axis and the upper surface of the glass substrate as the center.

4. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 3, characterized in that: When the diameter of the through-hole area of ​​the target countersunk hole is not much different from the upper diameter of the conical countersunk hole area, the scanning path of the Bessel beam in step S3 is a circle; when the diameter of the through-hole area of ​​the target countersunk hole is much different from the upper diameter of the conical countersunk hole area, the scanning path of the Bessel beam in step S3 is multiple concentric circles, and the radial distance between adjacent concentric circles is 50μm~150μm.

5. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that, Between steps S3 and S4, the following steps are also included: lowering the height of the laser processing head so that the lower surface and the shallow area above it of the glass cover to be processed are within the focal depth range of the Bessel beam; setting the laser processing parameters to low pulse energy, small pulse width and few pulses to laser induce the glass substrate to form a third modified area surrounding the lower periphery of the first modified area; in step S4, a countersunk hole with tapered countersunk hole areas at both ends and a through hole area in the middle is integrally formed on the glass substrate.

6. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that: Before step S1, the following steps are also included: first, remove the floating dust and debris from the surface of the glass substrate, then put the glass substrate into anhydrous ethanol for ultrasonic cleaning, then transfer it to deionized water for ultrasonic cleaning, then dry it, cool it to room temperature, and then fix it on the laser processing platform.

7. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that: In step S1, the laser used is an infrared ultrafast laser with a working wavelength of 1030nm~1064nm and a pulse width of femtosecond to picosecond.

8. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that: In step S1, the Gaussian beam emitted by the laser is sequentially shaped by a half-wave plate, a polarizing beam splitter, a continuously adjustable attenuator, a high-speed electronic shutter, a beam expander group, a conical lens, and an objective lens to form a Bessel beam.

9. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that: In step S4, the etching solution used is HF solution with a mass concentration of 5wt%~20wt% and a temperature of 20℃~40℃.

10. The method for preparing glass countersunk holes based on partitioned laser-induced modification as described in claim 1, characterized in that: In step S4, ultrasonic assistance is used during the etching process, and the frequency of the ultrasonic waves is 28kHz~40kHz.

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