Method for ultrafast laser processing of micro-holes with large depth-to-diameter ratio
By combining ultrafast laser with three protective gases and employing spiral and retraction techniques, the problem of reducing micro-hole size in the machining of micro-holes with large aspect ratios has been solved, achieving efficient and high-precision micro-hole machining and improving machining depth and accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 苏州易理激光科技有限公司
- Filing Date
- 2024-02-19
- Publication Date
- 2026-06-02
AI Technical Summary
When existing technologies struggle to process micro-holes with large aspect ratios, the size of the micro-hole gradually decreases as the depth increases, leading to problems such as conical holes or even the inability to drill through.
The process employs an ultrafast laser combined with three protective gases to remove each layer of material in a spiral motion. During processing, the laser focus retraction and power adjustment, as well as the change in protective gas flow rate, are controlled. Combined with the use of a circular shape to remove material from the hole wall, this method achieves efficient and high-precision processing of multiple materials and sizes.
Without affecting the drilling size, the maximum depth of the micro-hole was significantly increased, the interference of the plasma shielding effect was reduced, and the processing accuracy and efficiency were improved.
Smart Images
Figure CN117862704B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for laser processing of micro-holes with a large aspect ratio. Background Technology
[0002] With the development of laser technology, laser processing technology has also emerged. Micro-hole machining of materials is an important application in this field, offering advantages such as: laser drilling is a non-contact process, avoiding tool damage associated with traditional machining methods, and boasting high precision, high efficiency, and high quality. Ultrafast lasers typically refer to pulsed lasers with pulse widths in the sub-picosecond to femtosecond range. Based on their extremely short pulse widths and extremely high peak energy, they can process almost all materials. Furthermore, ultrafast lasers can achieve "cold working" of materials, and with appropriate processing techniques, precision machining can be achieved without heat-affected zones, recast layers, or microcracks.
[0003] In existing laser micro-hole machining technologies, the machining of high-depth micro-holes has always been a difficult problem, especially for micro-holes with large aspect ratios. Due to the characteristics of lasers, as the machining depth increases, the plasma and material debris inside the micro-hole enhance the shielding effect on the laser, thereby reducing the continuous machining effect of the laser. Furthermore, this shielding effect leads to a decrease in the laser energy incident on the substrate surface, resulting in increased refraction of the laser by the micro-hole sidewalls, a gradual reduction in the micro-hole size, and even the emergence of tapered holes or holes that cannot be drilled through. Summary of the Invention
[0004] The present invention aims to solve the technical problem that in the current laser processing of micro-holes with large aspect ratios, the size of the micro-hole gradually decreases with the increase of processing depth, resulting in tapered holes or even holes that cannot be drilled through. The invention provides a method for ultrafast laser processing of micro-holes with large aspect ratios.
[0005] The method for ultrafast laser processing of micro-holes with large aspect ratios according to the present invention is carried out according to the following steps:
[0006] 1. Drilling is performed using an ultrafast laser. During the process, three protective gas beams are set up for protection. The three protective gas beams are evenly distributed and at the same height. When viewed from above, the three protective gas beams are spaced 120° apart and converge at the center of the surface of the hole to be drilled.
[0007] The three protective gas beams have the same angle with the workpiece surface, and all of them are greater than or equal to 40° and less than 90°.
[0008] Starting from the center of the upper surface of the hole to be drilled, rotate outwards in a spiral motion to completely remove each layer of microporous material until a through hole is formed. The diameter of the through hole is 10μm to 30μm smaller than the preset diameter of the hole to be drilled.
[0009] The ratio of the depth to the diameter of the hole to be drilled is ≥10:1;
[0010] The following requirements also apply during the processing:
[0011] ① During the micro-hole processing, the laser focus continues to move one layer towards the micro-hole exit direction after each layer of material is processed. The distance of each layer is 0.005mm to 0.01mm. The sum of the distances of 200 to 400 layers is defined as distance L.
[0012] ② After processing a distance L, the laser focus needs to be moved back by 1 / 4 to 1 / 3 of the distance L towards the entrance of the micro-hole, and the laser should be turned off during the retraction process; after the retraction is completed, the ultrafast laser is started and processing continues for a distance L towards the exit of the micro-hole; during the processing, the protective gas flow rate also increases after processing a distance L.
[0013] ③ Repeat the processing method in ② above until the through hole is formed. After each section of distance L is processed, the laser power is increased by 10% to 30% before processing the next section of distance L.
[0014] 2. An ultrafast laser is used to remove material from the hole wall in a circular shape, while the protective gas flow rate is the final flow rate in step 1 and remains constant; the processing range extends from the micro-hole inlet to the outlet, and the through-hole diameter is the preset diameter of the hole to be drilled; during the micro-hole processing, the laser focus continues to move towards the micro-hole outlet after each layer of material is processed until the micro-hole processing is completed, and the distance of each layer is 0.01mm to 0.03mm; the laser power remains constant throughout this process.
[0015] Advantages of this invention:
[0016] The method of this invention can increase the maximum drilling depth without affecting the planned drilling size; the three-beam protective gas can effectively increase the protective gas flow rate inside the micro-hole and reduce interference factors such as plasma shielding effect during the micro-hole processing; through the flexible control mechanism of protective gas position and flow rate, the purpose of high-efficiency and high-precision large-diameter-ratio micro-hole processing can be achieved for multiple materials, multiple sizes, and large depth-to-diameter ratios.
[0017] Due to the characteristics of lasers, as the processing depth increases, the plasma and material debris inside the microhole enhance the shielding effect on the laser, thereby reducing the continuous processing effect of the laser. Furthermore, this shielding effect leads to a decrease in the laser energy incident on the substrate surface, resulting in increased refraction of the laser by the microhole sidewalls, a gradual reduction in the microhole size, and even the appearance of tapered holes or holes that cannot be drilled through. In step one of this invention, the retraction method can move the laser processing focus upwards before the processing taper is generated. During the retraction process, the laser is turned off, and the continuous protective gas can completely remove the debris inside the hole. When processing is performed again, it can continue to be processed in a straight hole manner until the next taper is generated. This operation is repeated until the through hole is completed.
[0018] The step-by-step drilling method of this invention (first using high-power spiral planar drilling, then using medium- and low-power circumferential drilling) can increase the maximum drilling depth while maintaining drilling accuracy. High-power spiral planar drilling removes the single-layer material inside the micropore, providing a channel for subsequent residue removal. After the through-hole is formed, medium- and low-power circumferential drilling removes irregular deposits on the hole wall, and subsequent residue can be discharged from the through-hole outlet with the help of an auxiliary device, improving drilling accuracy. The staged micro-hole processing method can further reduce interference from plasma shielding and increase drilling depth. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the laser spot trajectory in step one of Experiment 1;
[0020] Figure 2 This is a schematic diagram of the laser spot trajectory in step two of Experiment 1;
[0021] Figure 3 This is a schematic diagram of the laser focus movement in step one of Experiment 1. Detailed Implementation
[0022] Specific Implementation Method 1: This implementation method is a method for ultrafast laser processing of micro-holes with a large aspect ratio, specifically carried out according to the following steps:
[0023] 1. Drilling is performed using an ultrafast laser. During the process, three protective gas beams are set up for protection. The three protective gas beams are evenly distributed and at the same height. When viewed from above, the three protective gas beams are spaced 120° apart and converge at the center of the surface of the hole to be drilled.
[0024] The three protective gas beams have the same angle with the upper surface of the workpiece, and all of them are greater than or equal to 40° and less than 90°.
[0025] Starting from the center of the upper surface of the hole to be drilled, rotate outwards in a spiral motion to completely remove each layer of microporous material until a through hole is formed. The diameter of the through hole is 10μm to 30μm smaller than the preset diameter of the hole to be drilled.
[0026] The ratio of the depth to the diameter of the hole to be drilled is ≥10:1;
[0027] The following requirements also apply during the processing:
[0028] ① During the micro-hole processing, the laser focus continues to move one layer towards the micro-hole exit direction after each layer of material is processed. The distance of each layer is 0.005mm to 0.01mm. The sum of the distances of 200 to 400 layers is defined as distance L.
[0029] ② After processing a distance L, the laser focus needs to be moved back by 1 / 4 to 1 / 3 of the distance L towards the entrance of the micro-hole, and the laser should be turned off during the retraction process; after the retraction is completed, the ultrafast laser should be started and the processing should continue towards the exit of the micro-hole for a distance L.
[0030] During the processing, the protective gas flow rate increases for every processing distance L;
[0031] ③ Repeat the processing method in ② above until the through hole is formed. After each section of distance L is processed, the laser power is increased by 10% to 30% before processing the next section of distance L.
[0032] 2. An ultrafast laser is used to remove material from the hole wall in a circular shape, while the protective gas flow rate is the final flow rate in step 1 and remains constant; the processing range extends from the micro-hole inlet to the outlet, and the through-hole diameter is the preset diameter of the hole to be drilled; during the micro-hole processing, the laser focus continues to move towards the micro-hole outlet after each layer of material is processed until the micro-hole processing is completed, and the distance of each layer is 0.01mm to 0.03mm; the laser power remains constant throughout this process.
[0033] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that it uses a Dowell prism module to control the laser movement. The Dowell prism module is an existing product, and the website for purchasing it is: https: / / acunity.de / laserbohren-technologie / , model: HDO v7, product name: Helical Drilling Optics, company name: ACunity. Everything else is the same as in Specific Implementation Method One.
[0034] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the inner diameter of the three protective gas nozzles is 0.1mm to 1.5mm. Everything else is the same as in Specific Implementation Method 1 or 2.
[0035] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the protective gas pressure range is 0.2 MPa to 1 MPa. Everything else is the same as in Specific Implementation Methods One to Three.
[0036] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the protective gas is argon or air. The main function of the protective gas is to blow out debris from inside the hole, and for certain materials, it can also prevent oxidation during processing. Everything else is the same as in Specific Implementation Method Four.
[0037] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the pulse width of the ultrafast laser is in the picosecond or femtosecond range. Everything else is the same as in Specific Implementation Method Five.
[0038] The invention was verified using the following experiments:
[0039] Experiment 1: This experiment demonstrates a method for ultrafast laser processing of micro-holes with large aspect ratios, specifically carried out according to the following steps:
[0040] 1. Drilling is performed using an ultrafast laser to prepare a through hole with a diameter of 0.5 mm, a depth of 5 mm, and a depth-to-diameter ratio of 10:1 in a nickel-based superalloy material. During the machining process, three protective gas beams are used for protection. The three protective gas beams are evenly distributed and at the same height. When viewed from above, the three protective gas beams are spaced 120° apart and converge at the center of the surface of the hole to be drilled. The angle between the three protective gas beams and the surface of the workpiece is 76°. The initial laser power is 10W.
[0041] The vertical distance between the nozzle head of the three protective gas streams and the upper surface of the sample is 2 mm; the three points of the nozzle head of the three protective gas streams are concentric circles with a diameter of 1 mm; the inner diameter of the protective gas nozzle is 0.3 mm.
[0042] Starting from the center of the upper surface of the hole to be drilled, rotate outwards in a spiral motion to completely remove each layer of microporous material until a through hole is formed with a diameter of 0.48 mm.
[0043] The following requirements also apply during the processing: Figure 3 As shown:
[0044] ① During the micro-hole processing, the laser focus continues to move one layer towards the micro-hole exit direction after each layer of material is processed, and the distance of each layer is 0.008mm; the sum of the distances of 200 layers is defined as distance L;
[0045] ② After processing a distance L, the laser focus needs to be moved back by 1 / 4 of the distance L towards the entrance of the micro-hole, and the laser should be turned off during the retraction. After the retraction is completed, the ultrafast laser should be started and the processing should continue for a distance L towards the exit of the micro-hole. During the processing, the protective gas flow rate is initially set to 0.4MPa. As the processing depth of the micro-hole increases, the protective gas flow rate increases by 0.2MPa for each processing distance L.
[0046] ③ Repeat the processing method in ② above until the through hole is formed. After each section of distance L is processed, the laser power is increased by 20% before processing the next section of distance L.
[0047] 2. An ultrafast laser is used to remove material from the hole wall in a circular shape. The protective gas flow rate is the final flow rate in step one and remains constant. The processing range is from the micro-hole inlet to the outlet, and the through-hole diameter is the preset diameter of the hole to be drilled. During the micro-hole processing, the laser focus continues to move towards the micro-hole outlet after each layer of material is processed until the micro-hole processing is completed. The distance of each layer is 0.02mm. The laser processing range is 0.47mm to 0.5mm. The laser power is always 8W during this process.
[0048] In this experiment, a Dowell prism module was used to control the movement of the laser. The Dowell prism module is an existing product. The website of the company from which it was purchased is: https: / / acunity.de / laserbohren-technologie / , the model is: HDOv7, the product name is Helical Drilling Optics, and the company name is: ACunity.
[0049] The protective gas used in this experiment is argon. The main function of the protective gas is to blow out the debris inside the hole and to prevent oxidation.
[0050] In this experiment, the ultrafast laser pulse width is in the picosecond range. This type of laser has a shorter pulse duration, less thermal effect, and higher processing quality.
[0051] Figure 1 This is a schematic diagram of the laser spot trajectory in step one of Experiment 1.
[0052] Figure 2 This is a schematic diagram of the laser spot trajectory in step two of Experiment 1.
[0053] Figure 3 This is a schematic diagram of the laser focus movement in step one of Experiment 1. 1 represents the micro-hole being processed, 2 represents the forward processing distance L of the first segment, 3 represents the retraction distance 1 / 4L of the first segment, 6 represents the forward processing distance L of the second segment, 5 represents the retraction distance 1 / 4L of the second segment, and 4 represents the forward processing distance L of the third segment.
Claims
1. A method for ultrafast laser processing of microholes with a large aspect ratio, characterized in that... The method for ultrafast laser processing of micro-holes with large aspect ratios is carried out according to the following steps:
1. Drilling is performed using an ultrafast laser. During the process, three protective gas beams are set up for protection. The three protective gas beams are evenly distributed and at the same height. When viewed from above, the three protective gas beams are spaced 120° apart and converge at the center of the surface of the hole to be drilled. The three protective gas beams have the same angle with the upper surface of the workpiece, and all of them are greater than or equal to 40° and less than 90°. Starting from the center of the upper surface of the hole to be drilled, rotate outwards in a spiral motion to completely remove each layer of microporous material until a through hole is formed. The diameter of the through hole is 10μm to 30μm smaller than the preset diameter of the hole to be drilled. The ratio of the depth to the diameter of the hole to be drilled is ≥10:1; The following requirements also apply during the processing: ① During the micro-hole processing, the laser focus continues to move one layer towards the micro-hole exit direction after each layer of material is processed. The distance of each layer is 0.005mm to 0.01mm. The sum of the distances of 200 to 400 layers is defined as distance L. ② After processing a distance L, the laser focus needs to be moved back by 1 / 4 to 1 / 3 of the distance L towards the entrance of the micro-hole, and the laser should be turned off during the retraction process; after the retraction is completed, the ultrafast laser should be started and the processing should continue towards the exit of the micro-hole for a distance L. During the processing, the protective gas flow rate increases for every processing distance L; ③ Repeat the processing method in ② above until the through hole is formed. After each section of distance L is processed, the laser power is increased by 10% to 30% before processing the next section of distance L.
2. An ultrafast laser is used to remove material from the hole wall in a circular shape, while the protective gas flow rate is the final flow rate in step 1 and remains constant; the processing range extends from the micro-hole inlet to the outlet, and the through-hole diameter is the preset diameter of the hole to be drilled; during the micro-hole processing, the laser focus continues to move towards the micro-hole outlet after each layer of material is processed until the micro-hole processing is completed, and the distance of each layer is 0.01mm to 0.03mm; the laser power remains constant throughout this process.
2. The method for ultrafast laser processing of microholes with large aspect ratios according to claim 1, characterized in that... The movement of the laser is controlled by a Dowell prism module.
3. The method for ultrafast laser processing of microholes with large aspect ratios according to claim 1, characterized in that... The inner diameter of the three protective gas nozzles is 0.1mm to 1.5mm.
4. The method for ultrafast laser processing of microholes with large aspect ratios according to claim 1, characterized in that... The protective gas pressure range is 0.2MPa to 1MPa.
5. The method for ultrafast laser processing of microholes with large aspect ratios according to claim 1, characterized in that... The protective gas is argon or air.
6. The method for ultrafast laser processing of microholes with large aspect ratios according to claim 1, characterized in that... The laser pulse width of the ultrafast laser is in the picosecond or femtosecond range.