Laser subtractive processing method and laser processing equipment

Abstract

The present application relates to the field of laser processing, and specifically discloses a laser processing method, which is based on the target power P, the target spot size D opt and the target pulse repetition frequency f opt , for laser processing of the material to be processed; where f opt =P / E opt And P≤P max , f opt ≤f max , P max is the rated target power, f max is the maximum pulse repetition frequency; the target pulse energy E opt With the target pulse energy flux F opt , Target spot size D opt Both are positively correlated; target pulse energy flux F opt is the threshold F for removing energy flux th (N)e 2 times (Gaussian beam) or e times (flat-top beam); target spot size D opt ≥D min , D min The solution provided in this application improves the overall material removal efficiency under unit light source power by comprehensively optimizing pulse energy, repetition frequency, and focus spot size, thereby improving the efficiency of laser processing.

Description

Technical Field

[0001] The present application relates to the technical field of laser processing, and in particular to a laser subtractive processing method and laser processing equipment. Background Art

[0002] Ultrafast laser manufacturing such as picosecond laser and femtosecond laser has become a precise, flexible, and material-universal processing light source due to its unique advantages, especially when facing special materials, special properties, special scales, special precision, and cross-scale manufacturing. It has been increasingly widely used in aerospace, biology and medicine, weapons, consumer electronics, automobiles and other fields.

[0003] On the one hand, although the average power of ultrafast lasers is rapidly advancing from tens of watts to kilowatts or even tens of thousands of watts, compared with continuous lasers and millisecond to nanosecond long-pulse traditional lasers, their power levels are still generally low, which leads to their biggest shortcomings in terms of the scale of processed products and processing efficiency affected by material removal rate. Therefore, although ultrafast laser manufacturing technology has been able to reach the threshold of macroscopic manufacturing at the centimeter or even meter scale, it is still mainly used for micro- and micro-nanostructure manufacturing; on the other hand, with the birth of cutting-edge ultrafast laser equipment with average power of kilowatts or even tens of thousands of watts and their application in macroscopic scale structure processing, how to efficiently use high-power ultrafast lasers to achieve efficient material removal has also become a widely concerned issue. Therefore, whether it is ultrafast laser micro-, micro-nanostructure processing or macroscopic manufacturing, achieving efficient use of laser energy has become a problem of great scientific and engineering significance.

[0004] In order to overcome the problem of low efficiency of ultrafast laser subtractive processing, the existing method is generally to increase the pulse energy or average power, and use the high pulse energy or high power characteristics to increase the processing efficiency. However, since the maximum power that a laser device can output is limited, increasing the pulse energy generally means reducing the usable pulse repetition frequency. When the pulse repetition frequency distribution characteristics remain unchanged, increasing the pulse energy means increasing the output power of the laser, which will lead to an increase in device cost.

[0005] In practice, for applications that rely on repeated pulses to overlap spatially on materials to produce a volume or depth greater than the volume or depth removed by a single pulse (such as fine or macro cutting and blind hole milling that is larger than the focused spot size), or for applications that rely on repeated pulses to be spatially discretely distributed on materials (such as processing a group of micro-pit structures), the amount of material removed per unit time is determined by the amount removed by a single pulse and the pulse repetition frequency. Considering that the pulse removal depth or volume has a near-saturation effect with pulse energy at high pulse energies, for processing systems with limited average laser source power, simply increasing the pulse energy is beneficial to increasing the amount of material removed under a single pulse, but at the cost of reducing the pulse repetition frequency (i.e., the number of pulses that repeat the removal behavior of a single pulse per unit time), which may result in no significant increase in the overall material removal rate or even a decrease. Although the amount of material removed per unit time can also be increased by directly increasing the average output power of the laser source, increasing the average power at least means an increase in the cost or overhead of the light source.

[0006] How to utilize the limited power of ultrafast lasers to improve the overall material removal efficiency per unit light source power has become an urgent need for optimizing processing parameters in production. Summary of the invention

[0007] The present application provides a laser processing method and a laser processing device, the purpose of which is to improve the overall material removal efficiency per unit light source power by comprehensively optimizing pulse energy, repetition frequency, focused spot size, and scanning speed, thereby improving the efficiency of laser processing.

[0008] In a first aspect, a laser processing method is provided, comprising:

[0009] Obtain the threshold F of the removal energy flux of the material to be processed under the equivalent total irradiation pulse number N th (N);

[0010] According to the target power P, target spot size D opt and the target pulse repetition frequency f opt , laser processing the material to be processed, wherein the target power P, the target spot size D opt and the target pulse repetition frequency f opt satisfy:

[0011] f opt =P / E opt And P≤P max , f opt ≤f max , E opt is the target pulse energy, P max is the rated target power of the laser processing equipment, f max is the maximum pulse repetition frequency of the laser processing equipment; wherein,

[0012] The target pulse energy E opt The target pulse energy flux F opt , the target spot size D opt Determine the target pulse energy E opt With the target pulse energy flux F opt , the target spot size D opt All are positively correlated;

[0013] The target pulse energy flux F opt is the threshold F for removing energy flux th 2 to 10 times (N);

[0014] The target spot size D opt Satisfaction: D opt ≥D min , D min is the minimum processing spot size of the laser processing equipment.

[0015] In the existing ultrafast laser subtractive processing methods, only the power or pulse energy is increased, or only any two factors among pulse energy, pulse repetition frequency and average power are considered. Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0016] (1) The laser processing method provided by the present application is a method for comprehensive global optimization of basic parameters in laser processing, namely, average power, pulse repetition frequency, processing spot size and its radial energy distribution characteristics, speed v of the spot relative to the processed material, and other characteristics. Compared with the previous single-factor optimization method that only uses the improvement of average power or pulse energy, and the binary variable optimization method that only considers any two factors among pulse energy, pulse repetition frequency, and average power, the basic parameters in ultrafast laser processing are conducive to maximizing the subtractive processing efficiency (i.e., the amount of material removed under unit pulse energy). Therefore, the laser processing method provided by the present application is a high-efficiency multi-parameter parameter selection optimization process method.

[0017] (2) The laser processing method provided by the present application is a method for orderly and reliable optimization of basic parameters in ultrafast laser processing. Starting from the principle of interaction between ultrashort pulse laser and material, the method uses the core parameter of the basic physical quantity that can quantitatively control the etching depth and width of each pulse, the overall removal time efficiency of the group pulse on the material, and the qualitative influence on the degree of thermal damage in processing, that is, the "threshold of energy flux removal" of the material. The relationship between two adjacent physical quantities such as pulse energy flux, pulse energy, and pulse repetition frequency is used to form a method of orderly determining basic parameters of "flux threshold-energy threshold-optimal energy-target pulse repetition frequency-speed range of the light spot relative to the processed material", and through the easy-to-achieve method of adjusting the light spot size by misfocusing, the parameter chain of "energy threshold-optimal energy-target pulse repetition frequency" can be converged and self-consistent through feedback iteration. Compared with previous methods, all elements in the basic parameter set are output in an orderly manner, avoiding the insufficiency of achieving stable, reliable, and maximized optimization of material removal efficiency due to disorder, skipping, and missing elements in the element sequence of the basic parameter set.

[0018] (3) The laser processing method provided in this application quantitatively constrains the basic parameters in ultrafast laser processing and takes into account other relevant manufacturing performances besides "high efficiency" performance.

[0019] In combination with the first aspect, in some implementations of the first aspect, for 1 / e 2 The circular focus spot of E opt =π×ω 2 ×F opt / 2; for a cylindrical focused spot, E opt =π×ω 2 ×F opt ; Where ω is the spot radius.

[0020] The laser processing method provided in this application is suitable for the most common 1 / e 2 The circular focused spot and cylindrical focused spot are highly applicable to the characteristics of the beam, and the method steps are simple, the flow is clear, the calculation process is simple, and it is easy to implement.

[0021] In combination with the first aspect, in certain implementations of the first aspect, for a processing spot whose radial energy distribution is a Gaussian distribution, F opt =(e 2 ±2.5)×F th (N); For the processing spot with flat-top radial energy distribution, F opt =(e±0.8)×F th (N).

[0022] The laser processing method provided in this application is suitable for the most common Gaussian or flat-top shaped spot energy spatial distribution, has strong applicability to beam characteristics, and has simple method steps, clear flow, simple calculation process, and is easy to implement. By effectively constraining the pulse energy flux values ​​of the Gaussian spot or flat-top spot to about 5 to 10 times (the optimal value is about 7.4 times) and about 2 to 3.5 times (the optimal value is about 2.7 times), respectively, the ultrafast laser can maintain high precision and low thermal damage at medium and low fluxes greater than the removal threshold, and achieves high-quality processing under efficient material removal. Therefore, it is a high-efficiency and high-quality subtractive processing parameter window selection method.

[0023] In combination with the first aspect, in certain implementations of the first aspect, a speed v of the processing light spot relative to the material to be processed satisfies: opt ×f opt / 150≤v≤v max , where v max is the maximum processing speed of the laser processing equipment.

[0024] Compared with previous methods, it ensures that the focused beam can scan the processed area once, reducing the possibility of repeated processing or excessive burning.

[0025] In conjunction with the first aspect, in some implementations of the first aspect, F opt =(1 / 3~2 / 3)F0, F0 is the rated target power P max , the maximum pulse repetition frequency f max and the minimum processing spot size D min The pulse energy flux under .

[0026] F opt It can be smaller than F0 to reduce the possibility of excessive energy saturation effect, such as making the energy just saturated or the energy approximately saturated.

[0027] In combination with the first aspect, in some implementations of the first aspect, N is 50-150.

[0028] The total number of equivalent irradiation pulses within the spot size is controlled within the range of less than 50 to 150, which avoids saturation of the removal depth during single-pass scanning processing, thereby ensuring that other optimized parameters (target pulse repetition frequency f opt , target pulse energy flux F opt , processing spot size) optimization effect.

[0029] In combination with the first aspect, in certain implementations of the first aspect, a single pulse duration t of the laser satisfies: t≤50ps.

[0030] In combination with the first aspect, in certain implementations of the first aspect, the laser processing method is applied to one or more of the following: laser milling, laser surface engraving, laser cutting, laser drilling with a cumulative number of pulse irradiations for a single hole being less than or equal to 150 times, and laser turning.

[0031] The laser processing method provided in the present application can be applied to a variety of subtractive processing techniques, has strong applicability to processing techniques, and has simple method steps, clear flow, simple calculation process, and is easy to implement.

[0032] In combination with the first aspect, in certain implementations of the first aspect, the laser processing method is applied to one or more of the following: metal materials, metal-like materials, semiconductor materials, insulating materials, and composite materials.

[0033] The laser processing method provided in this application can be applied to a variety of subtractive processing techniques for various materials such as metal or metal-like materials, semiconductor materials, insulating materials, composite materials, etc. It has strong applicability to the processed materials, and the method steps are simple, the flow is clear, the calculation process is simple, and it is easy to implement.

[0034] In a second aspect, a laser processing device is provided, wherein the laser processing device is used to execute the laser processing method as described in any one of the implementations of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic flow chart of a laser processing method provided in an embodiment of the present application;

[0036] Figure 2 A schematic flowchart of a method for calculating laser processing parameters provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The present application embodiment discloses a laser processing method, referring to Figure 1 .

[0039] 110, obtain the threshold F of the removal energy flux of the material to be processed under the equivalent total irradiation pulse number N th (N).

[0040] 120, according to the target power P, target spot size D opt and the target pulse repetition frequency f opt , for laser processing of the material to be processed, the target power P, the target spot size D opt and the target pulse repetition frequency f opt Satisfy: f opt =P / Eopt And P≤P max , f opt ≤f max , E opt is the target pulse energy, P max is the rated target power of the laser processing equipment, f max is the maximum pulse repetition frequency of the laser processing equipment; where the target pulse energy E opt The target pulse energy flux F opt 、Target spot size D opt Determine the target pulse energy E opt With the target pulse energy flux F opt 、Target spot size D opt Both are positively correlated; target pulse energy flux F opt is the threshold F for removing energy flux th 2 to 10 times (N); target spot size D opt Satisfaction: D opt ≥D min , D min It is the minimum processing spot size of the laser processing equipment.

[0041] Combine the following Figure 2 , the calculation method of the above parameters is introduced through the following steps.

[0042] Step 1: According to the total number of equivalent irradiation pulses N of the material to be processed within the spot scale, determine the threshold F of the removal energy flux of the material to be processed under the equivalent total number of irradiation pulses N. th (N).

[0043] The total number of equivalent irradiation pulses N can be 1 to 200, further, 50 to 150, further, 100. The threshold value F of the removal energy flux of the material to be processed th (N) can be obtained through existing experiments or theoretical deduction methods.

[0044] Step 2: Determine the target pulse energy flux F according to the radial energy distribution of the processing spot opt .

[0045] The radial energy distribution of the processing light spot may be, for example, a Gaussian distribution or a flat-top distribution. Preferably, for a processing light spot with a Gaussian radial energy distribution, F opt =(e 2 ±2.5)×F th (N), that is, F opt The value range is (e 2 -2.5)×F th (N)~(e 2 +2.5)×Fth (N); further, F opt The value range is (e 2 -0.2)×F th (N)~(e 2 +0.2)×F th (N). For a processing spot with a flat-top radial energy distribution, F opt =(e±0.8)×F th (N), that is, F opt The value range is (e-0.8)×F th (N)~(e+0.8)×F th (N). Furthermore, F opt The value range is (e-0.2)×F th (N)~(e+0.2)×F th (N). Among them, e is a natural constant.

[0046] Table 1 shows the material removal efficiency of aluminum alloy, alumina ceramic, and high modulus carbon fiber resin composite materials under different pulse energy fluxes F, that is, the volume of material removed per unit average power per unit time (unit: mm3 / min / W). The rows in Table 1 represent the pulse energy flux F and the threshold F of the removal energy flux. th The columns in Table 1 represent the material types. The experimental light source parameters are: pulse duration 1ps, central wavelength 532nm, pulse repetition frequency 50kHz-2MHz, and maximum average power 60W.

[0047]

[0048]

[0049] In some embodiments, when the radial energy distribution of the processing spot is in the form of Gaussian distribution, the target pulse energy flux F opt The threshold F for removing energy flux can be th (N) is 5 to 10 times; when the radial energy distribution of the processing spot is a flat-top distribution, the target pulse energy flux F opt The threshold F for removing energy flux can be th (N) is 2 to 3.5 times.

[0050] Step 3: Adjust the spot size D opt , and calculate the target pulse energy flux F opt The corresponding target pulse energy E opt .

[0051] Spot size D opt Can be greater than or equal to the minimum processing spot size D of the laser processing equipmentmin Generally speaking, when the pulse energy flux remains unchanged, the larger the spot size, the higher the pulse energy; when the spot size remains unchanged, the larger the pulse energy flux, the higher the pulse energy. The pulse energy is also related to the shape of the spot. For 1 / e 2 The circular focus spot of E opt =π×ω 2 ×F opt / 2; for a cylindrical focused spot, E opt =π×ω 2 ×F opt ; Where ω is the spot radius.

[0052] Step 4: Select the target power P and determine the target pulse repetition frequency f opt =P / E opt Whether the condition is met: If f opt ≤f max , then take f opt As the pulse frequency for subsequent processing; if f opt >f max , then jump to step 3. In the new step 3, a larger spot size D can be selected. opt , and recalculate the target pulse energy E opt , reselect the target power P until the target pulse repetition frequency f is met opt ≤Maximum pulse repetition frequency f max In processing engineering, the expansion of the spot size can be achieved by optical means such as misfocusing or replacing the focusing lens.

[0053] Afterwards, the material to be processed can be laser processed according to the above parameters obtained by calculation or selection.

[0054] In some embodiments, F opt =(1 / 3~2 / 3)F0, F0 is the rated target power P max , maximum pulse repetition frequency f max and minimum processing spot size D min The pulse energy flux under . Where, f max =P max / E0, F0 is the rated target power P max , maximum pulse repetition frequency f max The pulse energy under 1 / e 2 Taking the circular focused spot as an example, E0=π×ω 2×F0 / 2. Since the pulse energy flux may be too large at a smaller spot size, it is easy to cause an energy oversaturation effect. In combination with the solution provided in the embodiment of the present application, by expanding the spot size, it is beneficial to reduce the pulse energy flux of the spot when performing laser processing using the rated parameters of the laser processing equipment, so F opt It can be smaller than F0, reducing the possibility of excessive energy saturation effect, such as making the energy just saturated, or the energy nearly saturated. According to a large number of experimental verifications, after optimization, F opt It can be about 1 / 2 of F0.

[0055] In some embodiments, the speed v of the processing light spot relative to the material to be processed satisfies: opt ×f opt / 150≤v≤v max , where v max It is the maximum processing speed of the laser processing equipment.

[0056] In some embodiments, the duration t of a single pulse of the laser satisfies: t≤50 ps. Further, the duration t of a single pulse of the laser satisfies: 1-10 ps.

[0057] In some embodiments, the laser processing method is applied to one or more of the following: laser milling, laser surface engraving, laser cutting, laser drilling with a pulse cumulative irradiation number of less than or equal to 150 times for a single hole, and laser turning.

[0058] In some embodiments, the laser processing method is applied to one or more of the following: metal materials, metal-like materials, semiconductor materials, insulating materials, and composite materials.

[0059] The present application also provides a laser processing device for performing the following steps: Figure 1 The laser processing method shown.

[0060] The present application is further described in detail below in conjunction with the following contents.

[0061] Specific Example 1: Flat-top beam micro-cutting of 300 μm wide gap of tantalum sheet (milling through cutting)

[0062] The processing goal is to form a gap of about 300μm in width on a 300μm thick tantalum sheet through single-pass micro-milling and its trajectory filling. The processing method is galvanometer scanning processing. The pulse width of the laser source used is 800fs, the central wavelength is 1030nm, the available average power P=100W, and the maximum available pulse energy at this time is 50μJ, and the maximum available pulse repetition frequency f max =2MHz, the processing spot is a cylindrical focusing spot with a minimum diameter of 2ω=80μm, and the size is adjustable.

[0063] First, the multi-pulse removal threshold of the material is determined. The speed v of the laser scanning the material surface is set to: at the pulse repetition frequency f, the equivalent pulse number N = 2ω × f / v of a single scan is not greater than 10 2 Therefore, the scanning speed v is flexible and has a wide range of values. By using a 1000x microscope to scan the micro scratches, the threshold F of the material removal energy flux can be determined. th (N) about 0.15J / cm 2 . Considering the characteristics of the threshold hatching effect of metal materials, the material removal processing threshold of 100 pulse irradiation has entered a near-saturation state, that is, when N = 100, 500, 2000, the material removal threshold is almost the same, and the processing thresholds of thousands or even tens of thousands of pulses are close. Therefore, the processing threshold measured at this equivalent pulse number is already able to represent the material removal flux threshold of the material in the multi-pass reciprocating removal process.

[0064] Secondly, calculate the target pulse energy flux F opt The corresponding pulse energy E opt Since a flat-top circular spot is used, the target pulse energy flux F opt =(e±0.8)×F th (N) = (0.41 ± 0.12) J / cm 2 , where the constant e≈2.72 is the base of the natural logarithm. The central value is 0.41 J / cm 2 As F opt For a flat-top focusing spot with an average radius of ω = 40 μm, use E opt =π×ω 2 ×F opt The target pulse energy E can be obtained opt =21μJ.

[0065] Again, first let the target pulse repetition frequency f opt =P / E opt =100W / 21μJ=4.76MHz, find f opt Greater than the maximum available pulse repetition frequency f max =2MHz, indicating that the target pulse repetition frequency f is set at this time opt is not feasible (i.e. too large). So we can let f opt =f max =2MHz, and jump to the previous step at the same time, by adjusting the optical device, the spot diameter is expanded to at least 2ω=80μm×sqrt(4.76MHz / f max =2MHz)≈123.4μm. At this time, if we consider the spot diameter 2ω=123.4μm, then using Eopt =π×ω 2 ×F opt The target pulse energy E can be obtained opt =50 μJ (i.e., the maximum available pulse energy is 50 μJ). A larger diameter spot may also be considered, for example, a spot with 2ω=160 μm, which still meets the conditions.

[0066] Finally, using the average power P = 100W and the spot diameter D opt ≈123μm and its corresponding target pulse repetition frequency f opt =2MHz, use v=25m / s, 10m / s, 5m / s (at this time, v≥D opt ×f opt / 150) and other parameters that can be selected flexibly, and the corresponding track filling line spacing is made to be 12.5μm, 5.0μm and 2.5μm respectively (thereby achieving equal-spaced dot matrix removal along the two perpendicular directions of the filling track and perpendicular to the track, thereby ensuring uniform thickness removal of each layer), and the area of ​​length × width × thickness = 1000μm × 300μm × 300μm is finely cut (milling through cutting). In order to avoid other factors (such as shielding of incident light energy by machining ejection splashes) for the judgment and analysis of the method results, the auxiliary blowing effect is used to blow away the ejection as much as possible. According to the measurement and statistics of the machining process, the depth of material removed with each scan increases almost proportionally. For the three scanning speeds of v = 25m / s, 10m / s, and 5m / s, an average of 9.7μm, 30.0μm, and 112.0μm in the 300μm thickness direction were removed respectively (that is, 2.9×10 -3 mm 3 9.0×10 -3 mm 3 , 3.4×10 -2 mm 3 ), the average time was 1.97μs, 6.0μs, and 24.0μs respectively, and the equivalent material removal rate was 88mm 3 / min, 90.0mm 3 / min, 85mm 3 / min, that is, within the error range, the material removal rate is almost independent of the set scanning speed range. Considering that the applied power is 100W, the material removal efficiency is between 0.88-0.90mm 3 / min / W range.

[0067] In contrast, the processing efficiency of the traditional method without global coordination of spot size, pulse repetition frequency, and pulse energy is significantly lower than the above 0.88-0.90mm. 3 / min / W material removal efficiency, for example, if the original spot without expansion (i.e., the flat-top focus spot with a diameter of 2ω = 80μm) is used, the average power P = 100W, the maximum available pulse energy 50μJ (the resulting pulse repetition frequency f = 2MHz, the pulse energy flux is about F = 1.0J / cm 2 ), setting a similar large-scale scanning speed v, the material removal efficiency is only 0.32-0.36mm according to a similar measurement method. 3 / min / W, that is, the material removal rate is 32-36mm 3 It can be seen that for the conventional method, although the average power (all 100 W), pulse energy (all 50 μJ), and repetition frequency (all 2 MHz) applied are the same as those of the method of this embodiment, since the spot size is not the minimum spot size, that is, the spot is expanded to a certain extent, the material removal efficiency and material removal performance are only about 40% of those in the above embodiment.

[0068] Specific Example 2: Gaussian beam macro-cutting of 80 μm thick carbon fiber composite material prepreg for satellite (in-situ reciprocating etching cutting)

[0069] The pulse width of the laser source used is 10ps, the central wavelength is 532nm, and the maximum pulse repetition frequency is 1MHz. According to the characteristics of the laser and the site conditions, the average power value P=60W can be used at the maximum pulse repetition frequency of 1MHz, and the pulse energy can be used at this time. 60μJ. If the pulse frequency is reduced to less than 1MHz, the average power can also become P=60W, and the pulse energy can be between 60-200μJ. The minimum diameter of the processing spot (i.e. the waist diameter of the focused beam) is 2ω=45μm (1 / e 2 The Gaussian focused spot (defined by the model) is formed, and the size can be adjusted by misfocusing. Considering that the material thickness is comparable to the spot size, which is much smaller than the focal depth of the Gaussian beam (on the order of 5mm), the in-situ reciprocating etching cutting method without filling is used to achieve cutting.

[0070] First, the multi-pulse removal threshold of the material is determined. The speed v of the laser scanning the material surface is set to: at the pulse repetition frequency f, the equivalent pulse number N = 2ω × f / v of a single scan is not greater than 10 2 This order of magnitude. Therefore, the scanning speed v is flexible and has a wide range of values. Similar to the method of the above-mentioned specific embodiment 1, the material removal flux threshold F of the material in the multi-pass reciprocating removal process can be determined. th (N) about 0.70J / cm 2 .

[0071] Secondly, calculate the target pulse energy flux F optThe corresponding pulse energy E opt Since a Gaussian circular spot is used, the target pulse energy flux F opt =(e 2 ±2.5)×F th (N) = (5.2 ± 1.8) J / cm 2 , where the constant e≈2.72 is the base of the natural logarithm. The central value is 5.20 J / cm 2 As F opt For a focused spot with an average radius of ω = 45 μm, use E opt =π×ω 2 ×F opt / 2 The target pulse energy E opt =41μJ.

[0072] Again, first let the target pulse repetition frequency f opt =P / E opt =60W / 41μJ=1.46MHz, find f opt Greater than the maximum available pulse repetition frequency f max =1MHz, indicating that the target pulse repetition frequency f is set at this time opt is not feasible (i.e. too large). So we can let f opt =f max =1MHz, and jump to the previous step at the same time, and expand the spot diameter to at least 2ω=45μm×sqrt(1.46MHz / f max =1MHz)≈54μm.

[0073] Finally, using the average power P = 60W and the spot diameter D opt =54μm and its corresponding target pulse repetition frequency f opt =1MHz, use v=25m / s (this satisfies v≥D opt ×f opt / 150) and other optional conditions, the structure of the target material (i.e., several carbon fiber composite materials for satellites with a thickness of 80 μm) Through hole) is cut with scanning galvanometer processing head. After measuring and statistically analyzing the processing process, it is found that for each The target structure, along the scale The trajectory of reciprocating cutting is about 270-290 circles (average time is about 0.70s) to achieve the material is just cut through, and the depth is almost proportional to the number of reciprocating circles, that is, the average cutting seam increases by about 1.4μm after each circle of processing. The hole circumference is about 62.8mm, and the cutting time is 0.70s, which is equivalent to an equivalent cutting speed of 90mm / s.

[0074] In contrast, the processing efficiency of the conventional processing method without global coordination of spot size, pulse repetition frequency, and pulse energy is significantly lower than the above-mentioned material cutting speed of 90 mm / s. For example, when processing the same target structure of the same material, if the original non-expanded spot (i.e., Gaussian focused spot with diameter 2ω=45 μm) is used, the maximum available pulse energy is 60 μJ (the resulting pulse energy flux is about F=12.6 J / cm 2 ), set a similar comparable spot overlap rate and after careful optimization, it was found through similar measurement methods that the equivalent cutting speed is ≤70mm / s. At this time, the slit entrance and cross-sectional dimensions are slightly smaller than the above results based on the optimization process (which means that the volume removed in the material slit is smaller than the above optimization result), but it is still at least 20% lower than the equivalent cutting speed of 90mm / s in the above results based on the optimization process. Although the 20% difference is not very obvious, this is because, on the one hand, the difference between the basic processing parameters used in the unoptimized processing method here (using the spot at the waist of the focused beam, that is, the minimum diameter of the entire beam 2ω=45μm spot to process the material) and the optimized one is not very obvious. On the other hand, considering that the equivalent cutting speed is at least 20% lower than the above optimization result and the volume removed in the slit is slightly smaller than the above optimization result, it means that the material removal efficiency and material removal performance are significantly lower than the above optimization result. Especially when the object to be cut is not the 80μm thin-walled structure here, but the sub-millimeter and millimeter-scale thin plates commonly used on satellites, in-situ reciprocating etching cutting will become increasingly difficult or even impossible (caused by the fact that the processing debris cannot be discharged due to the narrow cutting seam, thus affecting the cutting depth, etc.), and the use of track filling milling cutting will be inevitable. The method provided in this application will become necessary and have obvious advantages. It is worth mentioning that the cutting quality: although the processing efficiency of the unoptimized processing method (i.e., using the spot at the waist of the focused beam) is only 20% lower, due to its pulse energy flux (F = 12.6J / cm 2 ) is much higher than the material removal processing threshold (about 18 times) and is also much higher than the 5.20 J / cm based on the optimization process results mentioned above. 2 The scale of the thermal deterioration layer produced at the cutting edge is 2 times larger than the above-mentioned result based on the optimization process, and obvious resin overburning and carbonization phenomena occur. This shows that the optimized processing method provided by this application not only improves the material removal efficiency and effectiveness, but also takes into account the processing quality.

[0075] In summary, the laser processing provided by this application is a method for comprehensive global optimization of basic parameters in ultrafast laser processing, namely, pulse repetition frequency, processing spot size, speed v of the spot relative to the processed material, etc. at a certain allowable average power. As a multi-parameter parameter selection optimization process method, it avoids the shortcomings of traditional methods that are difficult to achieve maximum optimization of material removal efficiency, and takes into account high-quality processing at the optimal material removal rate. The method has simple steps, clear process, and is easy to implement.

[0076] Although the present application is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present application. Any technical personnel in this field may make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A laser processing method, characterized in that: include: Obtain the threshold F of the removal energy flux of the material to be processed under the equivalent total irradiation pulse number N th (N); According to the target power P, target spot size D opt and the target pulse repetition frequency f opt , laser processing the material to be processed, wherein the target power P, the target spot size D opt and the target pulse repetition frequency f opt satisfy: f opt =P / E opt And P≤P max , f opt ≤f max , E opt is the target pulse energy, P max is the rated target power of the laser processing equipment, f max is the maximum pulse repetition frequency of the laser processing equipment; wherein, The target pulse energy E opt The target pulse energy flux F opt , the target spot size D opt Determine the target pulse energy E opt With the target pulse energy flux F opt , the target spot size D opt All are positively correlated; The target pulse energy flux F opt is the threshold F for removing energy flux th 2 to 10 times (N); The target spot size D opt Satisfaction: D opt ≥D min , D min is the minimum processing spot size of the laser processing equipment.

2. The laser processing method according to claim 1, characterized in that: For 1 / e 2 The circular focus spot of E opt =π×ω 2 ×F opt / 2; For a cylindrical focused spot, E opt =π×ω 2 ×F opt ; Where ω is the spot radius.

3. The laser processing method according to claim 1, characterized in that: For a processing spot with a Gaussian radial energy distribution, F opt =(e 2 ±2.5)×F th (N); For a processing spot with a flat-top radial energy distribution, F opt =(e±0.8)×F th (N).

4. The laser processing method according to claim 1, characterized in that: The speed v of the processing light spot relative to the material to be processed satisfies: D opt ×f opt / 150≤v≤v max , where v max is the maximum processing speed of the laser processing equipment.

5. The laser processing method according to claim 1, characterized in that: F opt =(1 / 3~2 / 3)F0, F0 is the rated target power P max , the maximum pulse repetition frequency f max and the minimum processing spot size D min The pulse energy flux under .

6. The laser processing method according to claim 1, characterized in that: The value of N ranges from 50 to 150.

7. The laser processing method according to claim 1, characterized in that: The duration t of a single laser pulse satisfies: t≤50ps.

8. The laser processing method according to claim 1, characterized in that: The laser processing method is applied to one or more of the following: laser milling, laser surface engraving, laser cutting, laser drilling with the cumulative number of pulse irradiation of a single hole being less than or equal to 150 times, and laser turning.

9. The laser processing method according to claim 1, characterized in that: The laser processing method is applied to one or more of the following: metal materials, metal-like materials, semiconductor materials, insulating materials, and composite materials.

10. A laser processing device, characterized in that: The laser processing equipment is used to perform the laser processing method according to any one of claims 1 to 9.

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