Laser processing apparatus and laser processing method

Abstract

The laser processing apparatus (1A) of the present invention includes: a semiconductor laser element (2); a waveform output unit (6) that outputs input waveform data (Da); a drive circuit (4) that supplies a drive current (id) having a time waveform corresponding to the input waveform data (Da) to the semiconductor laser element (2); and a processing optical system (5) that irradiates the workpiece (B) with the laser output from the semiconductor laser element (2). The semiconductor laser element (2) outputs a laser (La) formed by arranging two or more groups of optical pulses each including one or more optical pulses with a time interval therebetween. The time waveforms of at least two of the two or more groups of optical pulses are different from each other. The time waveform includes at least one of the time waveforms of the one or more optical pulses, the time widths of the one or more optical pulses, and the time intervals of the plurality of optical pulses. Thus, a laser processing apparatus and a laser processing method are realized in which a structure for irradiating a workpiece with a plurality of optical pulses having different time waveforms at a time difference can be miniaturized.

Description

Technical Field

[0001] The present disclosure relates to a laser processing apparatus and a laser processing method. Background Art

[0002] In Patent Document 1, a technique related to a laser processing method is disclosed. In this method, by combining at least two pulses (pulse trains) each having a pulse width of 10 picoseconds to 100 picoseconds, the material removal rate is increased. In order to generate two optical pulses having a time difference, the optical path of the laser from a laser oscillator is divided into two branches by a beam splitter, propagated on two optical paths having different optical path lengths, and then these optical paths are coupled by a beam combiner.

[0003] In Patent Document 2, a technique related to a laser processing method and a laser processing apparatus is disclosed. In this method and apparatus, two optical pulses having different pulse widths are irradiated onto a workpiece. Therefore, in one embodiment, a laser source that outputs one optical pulse and another laser source that outputs another optical pulse are provided.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-511314

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-128088 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In recent years, a technique of laser processing using optical pulses having a time width of nanoseconds or picoseconds has been studied. In such laser processing, various effects of laser processing can be obtained by irradiating multiple optical pulses with a time difference.

[0010] For example, in the above-mentioned Patent Document 1, it is described that the material removal rate is increased by irradiating two optical pulses with a time difference. In addition, there are cases where additional effects can be further exerted by making the time waveforms of the optical pulses different among multiple optical pulses. For example, in the above-mentioned Patent Document 2, it is described that damage to a non-processing area can be avoided by irradiating two optical pulses having different time widths.

[0011] However, in the method described in Patent Document 1, since the time difference between two optical pulses is achieved by using the optical path length difference between two optical paths, an optical path length difference corresponding to the desired time interval is required. For example, when the time difference is set to 5 nanoseconds, the optical path length difference is approximately 1.5 m. In addition, when the time difference is set to 5 microseconds, the optical path length difference is approximately 1500 m. Therefore, there is a problem of excessive device size. In addition, since a large loss is generated during the propagation of the laser on such a long optical path, there is also a problem of low energy efficiency.

[0012] In the device and method described as an embodiment in Patent Document 2, since a plurality of laser sources corresponding to each of a plurality of optical pulses having different time widths are required, the number of laser sources increases as the types of optical pulses increase, which becomes a factor hindering the miniaturization and cost reduction of the laser processing device.

[0013] An object of the present invention is to provide a laser processing device and a laser processing method capable of miniaturizing a structure for irradiating a workpiece with a plurality of optical pulses having different time waveforms.

[0014] Technical means for solving the problem

[0015] An embodiment of the present invention is a laser processing device. The laser processing device includes: a semiconductor laser element; a waveform output unit that outputs input waveform data; a drive circuit that generates a drive current having a time waveform corresponding to the input waveform data and supplies the drive current to the semiconductor laser element; and an optical system that irradiates the workpiece with the laser output from the semiconductor laser element. The semiconductor laser element outputs a laser, which is formed by arranging two or more optical pulse groups each including one or more optical pulses at intervals of time. Among the two or more optical pulse groups, at least two optical pulse groups have different time waveforms. The time waveform includes at least one of the time waveforms of one or more optical pulses, the time widths of one or more optical pulses, and the time intervals of a plurality of optical pulses.

[0016] An embodiment of the present invention is a laser processing method. The laser processing method includes: a current supply step of generating a drive current having a time waveform corresponding to the input waveform data and supplying the drive current to the semiconductor laser element; and a light irradiation step of irradiating the workpiece with the laser output from the semiconductor laser element. In the light irradiation step, the semiconductor laser element outputs a laser, which is formed by arranging two or more optical pulse groups each including one or more optical pulses at intervals of time. Among the two or more optical pulse groups, at least two optical pulse groups have different time waveforms. The time waveform includes at least one of the time waveforms of one or more optical pulses, the time widths of one or more optical pulses, and the time intervals of a plurality of optical pulses.

[0017] In the above-described laser processing apparatus and laser processing method, the waveform output unit outputs input waveform data, and the drive circuit supplies a drive current having a time waveform corresponding to the input waveform data to the semiconductor laser element. Therefore, by including an arbitrary time waveform in the input waveform data, an optical pulse having an arbitrary time waveform can be output from the semiconductor laser element. Further, by including a plurality of pulse groups having a time difference in the input waveform data, a plurality of optical pulse groups having a time difference can be output from the semiconductor laser element.

[0018] That is, according to these apparatuses and methods, a plurality of optical pulse groups having different time waveforms can be irradiated onto the workpiece with a time difference. Further, since a plurality of optical pulse groups are output from a single semiconductor laser element on a single optical path, the apparatus structure can be miniaturized as compared with the methods described in Patent Documents 1 and 2.

[0019] Effects of the Invention

[0020] According to an embodiment of the present invention, there can be provided a laser processing apparatus and a laser processing method capable of miniaturizing a structure for irradiating a workpiece with a plurality of optical pulses having different time waveforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a block diagram schematically showing the structure of a laser processing apparatus according to an embodiment.

[0022] Figure 2 is a block diagram showing the peripheral structure of the semiconductor laser element 2, the optical amplifier 3, the drive circuit 4, and the waveform output unit 6.

[0023] Figure 3 is a block diagram showing a specific example of the peripheral structure of the semiconductor laser element 2, the optical amplifier 3, the drive circuit 4, and the waveform output unit 6.

[0024] Figure 4 is a block diagram showing a detailed structural example of the drive circuit 4.

[0025] Figure 5 is a diagram schematically showing the function of the waveform timing adjustment unit 43.

[0026] Figure 6 is a flowchart showing the operation of the laser processing apparatus 1A.

[0027] Figure 7 (a) to (d) are diagrams schematically showing optical pulse waveforms.

[0028] Figure 8 (a) is a graph showing the time waveform of the laser La before amplification, and (b) is a graph showing the time waveform of the laser Lb after amplification.

[0029] Figure 9 (a) is a graph showing the time waveform of the laser La before amplification, and (b) is a graph showing the time waveform of the laser Lb after amplification.

[0030] Figure 10 is a graph showing an example of the time waveform of the laser Lb output from the optical amplifier 3. (a) shows a Gaussian waveform with an FWHM of 4 ns, and (b) shows a Gaussian waveform with an FWHM of 32 ns.

[0031] Figure 11 is a graph showing an example of the time waveform of the laser Lb output from the optical amplifier 3. (a) shows a rectangular wave with an FWHM of 120 ns, and (b) shows a ramp waveform with an FWHM of 4 ns.

[0032] Figure 12 is a graph showing the time waveform of the Gaussian pulse Pa with a pulse width of 23.7 ns (FWHM) generated as the laser Lb in the laser processing apparatus 1A of one embodiment.

[0033] Figure 13 (a) is a front image of the workpiece B after through-hole machining observed by SEM (Scanning Electron Microscope), and (b) is a back image of the workpiece B after through-hole machining observed by SEM.

[0034] Figure 14 is a graph showing the time waveform of the optical pulse train including a plurality of ultrashort optical pulses Pba, that is, the optical pulse group Pb, generated as the laser Lb in the laser processing apparatus 1A of one embodiment.

[0035] Figure 15 (a) is a front image of the workpiece B after through-hole machining observed by SEM, and (b) is a back image of the workpiece B after through-hole machining observed by SEM.

[0036] Figure 16 (a) is a graph showing the time waveforms of the optical pulse groups Pc and Pd generated as the laser Lb in the laser processing apparatus 1A of one embodiment, and (b) is a front image of the workpiece B after through-hole machining observed by SEM.

[0037] Figure 17 is a graph showing an example of the time waveform of the laser Lb.

[0038] Figure 18It is a diagram showing an example of the time waveform of laser Lb. (a) shows a light pulse group Pf1 including a plurality of ultrashort light pulses Pfa, a light pulse group Pf2 including a single light pulse Pfb, and (b) shows a light pulse group Pg1 including a plurality of ultrashort light pulses Pga, a light pulse group Pg2 including a single light pulse Pgb, and a light pulse group Pg3 including a single light pulse Pgc.

[0039] Figure 19 It is a diagram showing an example of the time waveform of laser Lb, showing a light pulse group Ph1 including a single light pulse Pha and a light pulse group Ph2 including a single light pulse Phb.

[0040] Figure 20 (a) to (c) are diagrams conceptually showing various time waveforms that can be output from a laser processing apparatus 1A of an embodiment.

[0041] Figure 21 (a) to (c) are diagrams conceptually showing various time waveforms that can be output from a laser processing apparatus 1A of an embodiment.

[0042] Figure 22 (a) to (c) are diagrams conceptually showing various time waveforms that can be output from a laser processing apparatus 1A of an embodiment.

[0043] Figure 23 (a) to (c) are diagrams conceptually showing various time waveforms that can be output from a laser processing apparatus 1A of an embodiment.

[0044] Figure 24 (a) to (c) are diagrams conceptually showing various time waveforms that can be output from a laser processing apparatus 1A of an embodiment.

[0045] Figure 25 It is a diagram showing an example of combining a plurality of light pulse groups Pi, Pj, and Py corresponding to a plurality of processing processes respectively.

[0046] Figure 26 It shows the processing process when using a laser processing apparatus 1A of an embodiment to continuously perform a plurality of processing processes in a short period of time. (a) shows a workpiece B having a plurality of layers B1 to B3 made of different materials and the laser Lb irradiated onto the workpiece B, and (b) shows the time waveform of the laser Lb.

[0047] Figure 27 It shows the processing process when using a laser processing apparatus 1A of an embodiment to continuously perform a plurality of processing processes in a short period of time. (a) shows a workpiece B having a plurality of layers B1 to B3 made of different materials and the laser Lb irradiated onto the workpiece B, and (b) shows the time waveform of the laser Lb.

[0048] Figure 28 Shows the processing process when using the laser processing apparatus 1A of an embodiment to continuously perform a plurality of processing processes during a short period of time. (a) shows the workpiece B having a plurality of layers B1 to B3 with different constituent materials, the laser Lb irradiated onto the workpiece B, and (b) shows the time waveform of the laser Lb.

[0049] Figure 29 Shows the processing process when using the laser processing apparatus 1A of an embodiment to continuously perform a plurality of processing processes during a short period of time. (a) shows the workpiece B having a plurality of layers B1 to B3 with different constituent materials, the laser Lb irradiated onto the workpiece B, and (b) shows the time waveform of the laser Lb.

[0050] Figure 30 (a) is a diagram showing the combination of optical pulse groups Pi, Py, and Pk corresponding to a certain processing process, (b) is a diagram showing the optical pulse group Pj corresponding to the next processing process, and (c) is a diagram showing the optical pulse groups Pi, Pi, and Pm corresponding to the further next processing process.

[0051] Figure 31 Is a diagram showing the time waveform of the laser Lb irradiated in one embodiment.

[0052] Figure 32 (a) and (b) are diagrams showing SEM images of the holes formed in the workpiece B.

[0053] Figure 33 (a) and (b) are diagrams showing SEM images of the holes formed in the workpiece B.

[0054] Figure 34 Is a block diagram showing the structure of a modification.

[0055] Figure 35 Is a diagram showing an example of a plurality of optical pulse groups irradiated onto the workpiece B in a modification. Detailed implementation mode

[0056] Hereinafter, while referring to the drawings, embodiments of the laser processing apparatus and the laser processing method will be described in detail. In addition, in the description of the drawings, the same reference numerals are assigned to the same components, and duplicate descriptions are omitted. Furthermore, the present invention is not limited to these examples.

[0057] Figure 1 Is a block diagram schematically showing the structure of a laser processing apparatus according to an embodiment. As Figure 1As shown, the laser processing apparatus 1A of the present embodiment includes a semiconductor laser element 2, an optical amplifier 3, a drive circuit 4, a processing optical system 5, and a waveform output unit 6. The waveform output unit 6 is composed of an electronic circuit and is electrically connected to the drive circuit 4. The waveform output unit 6 calculates and generates input waveform data Da for making the time waveform of the optical pulse output from the optical amplifier 3 approximate to the target waveform, and provides the input waveform data Da to the drive circuit 4.

[0058] The input terminal of the drive circuit 4 is electrically connected to the waveform output unit 6, and receives the input waveform data Da from the waveform output unit 6. The drive circuit 4 generates a drive current id having a time waveform corresponding to the input waveform data Da. The output terminal of the drive circuit 4 is electrically connected to the semiconductor laser element 2, and supplies the generated drive current id to the semiconductor laser element 2. In addition, there is a case where a bias current having a constant magnitude without time variation is superimposed on the drive current id.

[0059] The semiconductor laser element 2 is a laser diode and is electrically connected to the drive circuit 4. The drive circuit 4 supplies the drive current id to either the cathode or the anode of the semiconductor laser element 2. The semiconductor laser element 2 receives the drive current id and generates a laser beam La. This laser beam La is the light before being amplified by the optical amplifier 3 and has a time waveform corresponding to the input waveform data Da.

[0060] In one example, the semiconductor laser element 2 is a distributed feedback (DFB) laser diode. Since the semiconductor laser element 2 is a DFB laser diode, it is easy to achieve optimization in accordance with the wavelength characteristics of the gain of the optical amplifier 3. The output power of the semiconductor laser element 2 is, for example, several nanojoules.

[0061] The optical input terminal of the optical amplifier 3 is optically coupled to the semiconductor laser element 2, and amplifies the laser beam La output from the semiconductor laser element 2. The optical amplifier 3 does not convert the laser beam La into an electrical signal, but directly amplifies it in the optical state. The optical amplifier 3 can be composed of, for example, an optical fiber amplifier, a solid-state laser amplifier, or a combination thereof.

[0062] The optical fiber amplifier has an optical fiber made of glass doped with impurities such as Er, Yb, etc., and amplifies the laser beam La by inputting pump light into the optical fiber together with or before the laser beam La. In addition, the solid-state laser amplifier can be composed of glass doped with impurities such as Nd, yttrium aluminum garnet (YAG), or neodymium, yttrium, vanadium tetraoxide (YVO4). The solid-state laser amplifier amplifies the laser beam La by inputting pump light together with or before the laser beam La. The gain of the optical amplifier 3 is, for example, in the range of 3 dB to 30 dB.

[0063] The processing optical system 5 is configured to include an optical path extending from the output end of the optical amplifier 3 and a condensing optical system provided on the optical path. The amplified laser beam Lb output from the optical amplifier 3 propagates on the optical path of the processing optical system 5, reaches the condensing optical system, is condensed by the condensing optical system, and is irradiated onto the workpiece B.

[0064] Figure 2 is a block diagram showing the peripheral structure of the semiconductor laser element 2, the optical amplifier 3, the drive circuit 4, and the waveform output unit 6. In addition, the waveform A in the figure schematically shows the time waveform of the laser beam La output from the semiconductor laser element 2. As Figure 2 shown, the waveform output unit 6 includes a computer 31, a waveform adjustment unit 32, and a comparison unit 33.

[0065] The computer 31 has a CPU (Central Processing Unit) and a memory, and operates according to a program stored in the memory. The memory of the computer 31 is the storage unit of the present embodiment, and stores data representing a desired (arbitrary) time waveform, that is, target waveform data (hereinafter referred to as target waveform data) in advance.

[0066] This target waveform data is stored in the memory in advance by the operator through the data input terminal of the computer 31 before the laser processing apparatus 1A operates. Alternatively, the computer 31 can also design the target waveform as a waveform design unit itself. That is, the computer 31 can also calculate a target waveform for realizing the light irradiation conditions (processing conditions, observation conditions) given from the outside. The target waveform data representing the calculated target waveform is stored in the memory of the computer 31.

[0067] The comparison unit 33 is electrically connected to a light detection unit 14 described later, and obtains the time waveform of the laser beam Lb based on the detection signal (light intensity signal Sc) that can be obtained from the light detection unit 14. In addition, the comparison unit 33 is electrically connected to the computer 31, and obtains the target waveform data Db from the computer 31. The comparison unit 33 compares the time waveform of the laser beam Lb with the target waveform, and sends the difference data Dc representing the difference to the waveform adjustment unit 32.

[0068] In addition, the comparison unit 33 can also be constituted by a computer having a CPU and a memory. In this case, the comparison unit 33 can be separated from the computer 31 or can be implemented in a computer common to the computer 31.

[0069] The waveform adjustment unit 32 is electrically connected to the computer 31, and obtains the target waveform data Db from the computer 31. In addition, the waveform adjustment unit 32 is electrically connected to the comparison unit 33, and obtains the difference data Dc output from the comparison unit 33. The waveform adjustment unit 32 generates input waveform data Da in such a manner that the time waveform of the laser beam Lb approaches the target waveform (that is, in such a manner that the difference becomes smaller) based on these data Db and Dc.

[0070] In addition, the waveform adjustment unit 32 may also be constituted by a computer having a CPU and a memory. In this case, the waveform adjustment unit 32 may be separate from the computer 31 and the comparison unit 33, or may be implemented in a computer common to at least one of the computer 31 and the comparison unit 33.

[0071] Figure 2 The laser processing apparatus 1A shown also includes an optical isolator 12, an optical branching unit 13, and an optical detection unit 14. The optical input end of the optical isolator 12 is optically coupled to the laser output end of the semiconductor laser element 2. In addition, the optical output end of the optical isolator 12 is optically coupled to the optical input end of the optical amplifier 3. That is, the optical isolator 12 is located on the optical path between the semiconductor laser element 2 and the optical amplifier 3. The optical isolator 12 prevents the light amplified by the optical amplifier 3 from returning to the semiconductor laser element 2.

[0072] The optical branching unit 13 and the optical detection unit 14 constitute an optical waveform detection unit 15. The optical waveform detection unit 15 detects the temporal waveform of the amplified laser beam Lb output from the optical amplifier 3. The optical branching unit 13 is optically coupled to the optical output end of the optical amplifier 3. The optical branching unit 13 branches a part Lb1 of the amplified laser beam Lb by reflecting (or transmitting) a part Lb1 of the amplified laser beam Lb output from the optical amplifier 3. The optical branching unit 13 may be constituted by, for example, a glass plate.

[0073] The ratio (branching ratio) P1 / P2 of the intensity P1 of a part Lb1 of the laser beam Lb to the intensity P2 of the remaining part is, for example, in the range of 0.005 to 0.01. The optical detection unit 14 is optically coupled to the optical branching unit 13 and receives a part Lb1 of the amplified laser beam Lb. In addition, the remaining part of the laser beam Lb is irradiated onto the workpiece B via Figure 1 the processing optical system 5 shown.

[0074] The optical detection unit 14 generates an electrical signal corresponding to the optical intensity of a part Lb1 of the laser beam Lb, that is, an optical intensity signal Sc, and provides this optical intensity signal Sc to the comparison unit 33. In one example, the optical detection unit 14 may be configured to include a photodiode and a circuit that converts the photocurrent flowing through the photodiode into a voltage signal.

[0075] The optical detection unit 14 may output the generated voltage signal as the optical intensity signal Sc, or may convert the generated voltage signal into a digital signal and output this digital signal as the optical intensity signal Sc. When the optical intensity signal Sc is a voltage signal, it is converted into a digital signal in the comparison unit 33. In addition, the optical detection unit 14 may include a phototube (for example, a double-sided phototube) instead of a photodiode.

[0076] Figure 3It is a block diagram showing a specific example of the peripheral structure of the semiconductor laser element 2, the optical amplifier 3, the drive circuit 4, and the waveform output unit 6. Figure 3 In the shown specific example, the laser processing apparatus 1A includes: as Figure 2 the optical isolators 21, 23, 27, and 29 of the optical isolator 12 shown, and the fiber optic amplifier 22, the solid-state laser amplifier 28, and 30 as the optical amplifier 3. Thus, in this specific example, the optical amplifier 3 is configured in multiple stages. Furthermore, the laser processing apparatus 1A includes a band-pass filter 24, a fiber optic connector 25, and a collimating lens 26.

[0077] The optical input end of the fiber optic amplifier 22 is optically coupled to the semiconductor laser element 2 via the optical fiber F1. Between the fiber optic amplifier 22 and the semiconductor laser element 2, the optical isolator 21 is interposed. The optical isolator 21 prevents light (laser La and pump light) from returning from the fiber optic amplifier 22 to the semiconductor laser element 2. Thereby, damage to the semiconductor laser element 2 can be prevented.

[0078] The optical output end of the fiber optic amplifier 22 is optically coupled to the band-pass filter 24 via the optical fiber F2. Between the fiber optic amplifier 22 and the band-pass filter 24, the optical isolator 23 is interposed. The optical isolator 23 prevents the light in the subsequent stage of the band-pass filter 24 from returning to the fiber optic amplifier 22.

[0079] The fiber optic amplifier 22 is the first-stage optical amplifier that amplifies the laser La output from the semiconductor laser element 2. The gain of the fiber optic amplifier 22 is, for example, in the range of 20 dB to 30 dB. The fiber optic amplifier 22 is, for example, a ytterbium-doped fiber (YDF). The band-pass filter 24 blocks the wavelength components of the fluorescence contained in the light output from the fiber optic amplifier 22. The band-pass filter 24 can be constituted by, for example, a dielectric multilayer film.

[0080] The band-pass filter 24 is optically coupled to the fiber optic connector 25 via the optical fiber F3. The fiber optic connector 25 terminates the optical fiber F3. That is, the light passing through the band-pass filter 24 propagates in the optical fiber F3 and reaches the fiber optic connector 25 and then is output into the space.

[0081] The collimating lens 26 is optically coupled to the fiber optic connector 25 via the space and collimates (parallelizes) the light radially output from the fiber optic connector 25. Since the intensity of the light amplified by the subsequent solid-state laser amplifiers 28 and 30 is large, in order to avoid damage to optical materials such as glass caused by the laser, thus in the subsequent stage of the fiber optic connector 25, it propagates in the space rather than in the optical fiber. In addition, Figure 3 in the figure, the light propagating in the space is shown by a dashed line.

[0082] The solid-state laser amplifier 28 is optically coupled to the collimating lens 26 via the optical isolator 27. The optical isolator 27 prevents the light of the solid-state laser amplifier 28 from returning to the front stage of the solid-state laser amplifier 28. Thus, damage to the fiber amplifier 22 can be prevented.

[0083] The solid-state laser amplifier 28 is an optical amplifier in the second stage, which further amplifies the amplified laser output from the fiber amplifier 22. The gain of the solid-state laser amplifier 28 is, for example, in the range of 3 dB to 20 dB.

[0084] The solid-state laser amplifier 30 is optically coupled to the solid-state laser amplifier 28 via the optical isolator 29. That is, the fiber amplifier 22, the solid-state laser amplifiers 28 and 30 are coupled in series with each other. The optical isolator 29 prevents the light of the solid-state laser amplifier 30 from returning to the front stage of the solid-state laser amplifier 30. Thus, damage to the solid-state laser amplifier 28 can be prevented.

[0085] The solid-state laser amplifier 30 is an optical amplifier in the third stage, which further amplifies the amplified laser output from the solid-state laser amplifier 28. The gain of the solid-state laser amplifier 30 is, for example, in the range of 3 dB to 10 dB. The light amplified by the solid-state laser amplifier 30 is output as the amplified laser Lb.

[0086] Figure 4 It is a block diagram showing a detailed structural example of the drive circuit 4. As Figure 4 shown, the drive circuit 4 has a control board 41, a waveform data storage unit 42, a waveform timing adjustment unit 43, a waveform signal generation unit 44, and a current conversion unit 45. In addition, the control board 41 is configured to include a CPU 41a and a high-speed DAC (Digital to Analog Converter) interface 41b. Among them, the high-speed DAC interface 41b, the waveform data storage unit 42, the waveform timing adjustment unit 43, and the waveform signal generation unit 44 constitute a D / A conversion unit 46. The D / A conversion unit 46 is an electronic circuit that converts the digital input waveform data Da into an analog drive signal Sd.

[0087] The control board 41 is a circuit board that serves as an interface with the waveform output unit 6. The CPU 41a is electrically connected to the waveform adjustment unit 32 of the waveform output unit 6 via a communication line (refer to Figure 2 ) and receives the input waveform data Da from the waveform adjustment unit 32. The CPU 41a sends the input waveform data Da to the high-speed DAC interface 41b at an appropriate timing. The high-speed DAC interface 41b causes the waveform data storage unit 42 to temporarily store the input waveform data Da. The waveform data storage unit 42 is electrically connected to the high-speed DAC interface 41b and is, for example, composed of a volatile storage element.

[0088] The waveform adjustment unit 32 of the present embodiment outputs the input waveform data Da as a plurality of consecutive interval waveform data obtained by dividing the time waveform of the input waveform data Da (details will be described below). These interval waveform data are output in parallel and simultaneously in units of two or more interval waveform data. Further, the waveform data storage unit 42 stores these plurality of interval waveform data and outputs the plurality of interval waveform data as required.

[0089] The waveform timing adjustment unit 43 is electrically connected to the waveform data storage unit 42 and adjusts (controls) the timing of outputting the input waveform data Da from the waveform data storage unit 42. Figure 5 It is a diagram schematically showing the function of the waveform timing adjustment unit 43. As Figure 5 shown, the waveform timing adjustment unit 43 outputs these data in sequence while giving an appropriate time difference to the plurality of interval waveform data DD1 to DD4 read from the waveform data storage unit 42. Here, the appropriate time difference is, for example, the time width of each interval waveform data. This time width defines the time resolution of the output waveform, which is 1 nanosecond in one embodiment.

[0090] The waveform signal generation unit 44 sequentially inputs the plurality of interval waveform data DD1 to DD4 output from the waveform timing adjustment unit 43, and sequentially converts these interval waveform data DD1 to DD4 into an analog signal (voltage signal), that is, a drive signal Sd. At this time, the time difference in the conversion timing of the interval waveform data DD1 to DD4 is substantially the same as the time difference given by the waveform timing adjustment unit 43.

[0091] Refer again to Figure 4 . The current conversion unit 45 is electrically connected to the waveform signal generation unit 44 and converts the drive signal Sd into a drive current id. That is, the current conversion unit 45 is composed of an analog circuit including a transistor and converts the voltage signal, that is, the drive signal Sd, into a current signal, that is, the drive current id. The time waveform of the drive current id generated at this time is substantially the same as the time waveform of the drive signal Sd.

[0092] In addition, a bias current control unit 11 is also connected to the current conversion unit 45. The bias current control unit 11 controls the magnitude of the bias voltage component included in the drive current id. The semiconductor laser element 2 is electrically connected to the current output terminal of the current conversion unit 45, receives the drive current id from the current conversion unit 45, and outputs the laser La. The time waveform of the laser La is substantially the same as the time waveform of the drive current id.

[0093] Figure 6 It is a flowchart showing the operation of the laser processing apparatus 1A. In addition, Figure 7(a) to (d) are diagrams schematically showing optical pulse waveforms. In these diagrams, the time waveform of the optical pulse is represented as a set of peak values (light intensities) of a plurality of consecutive unit intervals. A delay time TA is set as needed, and the starting point of the time waveform of the optical pulse is postponed by the delay time TA from the reference time. Figure 7 In (a) to (d), the vertical axis represents the light intensity, and the horizontal axis represents the time. While referring to Figure 6 and Figure 7 , the operation of the laser processing apparatus 1A and the laser processing method according to the present embodiment will be described.

[0094] First, the waveform adjustment unit 32 sets initial input waveform data Da (step ST1). The initial input waveform data Da is set based on the target waveform data Db. In one example, the target waveform data Db is directly used as the initial input waveform data Da. Next, based on the initial input waveform data Da, the drive circuit 4 supplies a drive current id to the semiconductor laser element 2, and the semiconductor laser element 2 outputs a laser La (current supply step ST2). Figure 7 (a) is a diagram schematically showing the time waveform of the laser La generated based on the initial input waveform data Da. The laser La is amplified by the optical amplifier 3 (optical amplification step ST3).

[0095] In addition, the current supply step ST2 includes a D / A conversion step ST21 and a current conversion step ST22. In the D / A conversion step ST21, the D / A conversion unit 46 converts the digital input waveform data Da into an analog drive signal Sd. At this time, as described above, a plurality of consecutive interval waveform data DD1 to DD4 (refer to Figure 5 ) obtained by dividing the time waveform of the input waveform data Da are sequentially converted into the drive signal Sd while giving a time difference. In the current conversion step ST22, the current conversion unit 45 converts the drive signal Sd into a drive current id.

[0096] Next, the time waveform of the amplified laser Lb is detected by the optical detection unit 14 (optical waveform detection step ST4). Figure 7 (b) is a diagram schematically showing the detected time waveform. In most cases, the time waveform of the amplified laser Lb is different from the time waveform of the laser La before amplification. As one of the reasons, it is cited that the excitation state of the optical amplifier 3 changes with time. That is, immediately after the laser La is incident, the optical amplifier 3 is strongly excited and amplifies the laser La with a high gain. However, as time elapses since the laser La is incident, the excitation intensity of the optical amplifier 3 gradually decreases, and accordingly, the amplification gain of the laser La also decreases.

[0097] Figure 8 and Figure 9It is a graph showing the respective time waveforms of the pre-amplification laser La and the post-amplification laser Lb that are actually measured. Figure 8 (a) shows the time waveform (rectangular wave) of the pre-amplification laser La, Figure 8 (b) shows the time waveform of the laser Lb after amplifying the laser La having the time waveform shown in Figure 8 (a). Additionally, Figure 9 (a) shows the time waveform (ramp wave) of the pre-amplification laser La, Figure 9 (b) shows the time waveform of the laser Lb after amplifying the laser La having the time waveform shown in Figure 9 (a). Furthermore, the vertical axis represents the light intensity (arbitrary unit), and the horizontal axis represents the time (unit: nanosecond). As shown in these figures, the time waveform of the post-amplification laser Lb is significantly different from the time waveform of the pre-amplification laser La.

[0098] Refer again to Figure 7 . In the waveform adjustment step ST5, first, the comparison unit 33 compares the detected time waveform of the laser Lb with the target waveform shown by the target waveform data Db ( Figure 7 (c)) and outputs their difference (error) (step ST51). Then, the waveform adjustment unit 32 adjusts the time waveform of the input waveform data Da based on this difference. That is, the waveform adjustment unit 32 calculates new input waveform data Da in such a way that this difference becomes smaller (i.e., approaches 0) (step ST52).

[0099] Based on this new input waveform data Da, the drive circuit 4 supplies a drive current id to the semiconductor laser element 2, and the semiconductor laser element 2 outputs the laser La (current supply step ST2). Figure 7 (d) schematically shows the time waveform of the laser La generated based on the new input waveform data Da. This laser La is amplified by the optical amplifier 3 (optical amplification step ST3). By repeating the above steps ST2 to ST5, the time waveform of the post-amplification laser Lb approaches the target waveform. The thus-generated laser Lb is irradiated onto the workpiece B via the Figure 1 shown processing optical system 5 (light irradiation step ST6).

[0100] Figure 10 and Figure 11 are graphs showing examples of the time waveforms of the laser Lb output from the optical amplifier 3. Additionally, the vertical axis represents the light intensity (arbitrary unit), and the horizontal axis represents the time (unit: nanosecond). Figure 10 (a) shows a Gaussian waveform with a full width at half maximum (FWHM) of 4 nanoseconds. Figure 10 (b) shows a Gaussian waveform with an FWHM of 32 nanoseconds. Figure 11(a) represents a rectangular wave with an FWHM of 120 nanoseconds. Figure 11 (b) represents a ramp waveform with an FWHM of 4 nanoseconds. As shown by these, the laser processing apparatus 1A according to the present embodiment can generate various arbitrary time waveforms.

[0101] Further study is made on a preferred time waveform of the laser Lb. Figure 12 is a graph showing the time waveform (measured value) of the Gaussian pulse Pa with a pulse width of 23.7 ns (FWHM) generated as the laser Lb in the laser processing apparatus 1A of the present embodiment. Figure 12 In this, the vertical axis represents the normalized intensity (arbitrary unit), and the horizontal axis represents time (unit: nanosecond). The laser Lb is irradiated onto the workpiece B to perform through-hole machining.

[0102] In addition, the wavelength of the laser Lb is set to 1064 nm, the repetition frequency of the optical pulse Pa is set to 300 Hz, irradiated for 3 seconds (i.e., the number of irradiations of the optical pulse Pa is 900 times), the pulse energy of the optical pulse Pa is set to 40 μJ, and a plano-convex lens with a focal length of 40 mm is used as the condenser lens of the processing optical system 5. Further, the workpiece B is set to stainless steel (SUS(steel use stainless)304) with a thickness of 50 μm, and the condensing diameter of the laser Lb on the workpiece B is set to 10 μm.

[0103] Figure 13 (a) is an image of the front surface (laser irradiation surface) of the workpiece B after through-hole machining observed by a scanning electron microscope (SEM). Figure 13 (b) is an image of the back surface of the workpiece B after through-hole machining observed by SEM. Refer to Figure 13 It can be seen that a substantially circular through-hole is formed in the workpiece B. When measuring the diameter of the hole on the front surface of the workpiece B, the width dx in the left-right direction of the paper surface is 19.1 μm, and the width dy in the up-down direction of the paper surface is 21.4 μm. That is, a hole about twice the size of the condensing diameter of the laser Lb is formed.

[0104] Figure 14 is a graph showing the time waveform (measured value) of an optical pulse train including a plurality of ultrashort optical pulses Pba, that is, an optical pulse group Pb, generated as the laser Lb in the laser processing apparatus 1A of the present embodiment. Figure 14 In this, the vertical axis represents the normalized intensity (arbitrary unit), and the horizontal axis represents time (unit: nanosecond). The laser Lb is irradiated onto the workpiece B to perform through-hole machining.

[0105] In addition, the pulse width of each ultrashort optical pulse Pba that constitutes the optical pulse train Pb is set to 70 ps (FWHM), the time interval between pulses is set to 2 ns, and the number of ultrashort optical pulses Pba is set to 10. Additionally, the repetition frequency of the optical pulse train Pb is set to 300 Hz, and it is irradiated for 3 seconds (i.e., the number of irradiations of the optical pulse train Pb is 900 times), and the pulse energy of each ultrashort optical pulse Pba is set to 40 μJ. The wavelength of the laser Lb, the condenser lens of the processing optical system 5, the material of the workpiece B, and the condensing diameter of the laser Lb are the same as above.

[0106] Figure 15 (a) is an image of the front surface (laser irradiation surface) of the workpiece B after through-hole machining observed by SEM. Figure 15 (b) is an image of the back surface of the workpiece B after through-hole machining observed by SEM. Referring to Figure 15 it can be seen that in this embodiment, a substantially circular through-hole is also formed in the workpiece B. When measuring the diameter of the hole on the front surface of the workpiece B, the width dx in the left-right direction of the paper surface is 28.6 μm, and the width dy in the up-down direction of the paper surface is 25.4 μm. That is, a hole larger than that in the case of the Gaussian pulse Pa shown in Figure 12 is formed.

[0107] Figure 12 The peak output of the Gaussian pulse Pa shown in 2 is 2.15 GW / cm Figure 14 . On the other hand, since the pulse width of the multiple ultrashort optical pulses Pba shown in 2 is smaller than that of the Gaussian pulse Pa, its peak output is about 30 times that of the peak output of the Gaussian pulse Pa (60 GW / cm Figure 15 ). Therefore, it is speculated that ablation is further promoted in

[0108] Figure 16 (a) is a graph showing the time waveforms (measured values) of the optical pulse trains Pc and Pd generated as the laser Lb in the laser processing apparatus 1A of the present embodiment. Figure 16 In (a), the vertical axis represents the normalized intensity (arbitrary unit), and the horizontal axis represents time (unit: nanosecond). The laser Lb is irradiated onto the workpiece B for through-hole machining.

[0109] In addition, the optical pulse train Pc includes multiple ultrashort optical pulses Pca, and compared with Figure 14The number of ultrashort optical pulses Pba in the optical pulse train Pb shown is halved to five, which is the same. The optical pulse Pd is a single pulse with a pulse width of 71 ns. The time interval Δt between the optical pulse train Pc and the optical pulse Pd is 260.1 ns. The wavelength, pulse energy, condenser lens of the processing optical system 5, the material of the workpiece B, and the condenser diameter of the laser Lb are the same as those described above.

[0110] Figure 16 (b) is an image of the front surface (laser irradiation surface) of the workpiece B after through-hole machining observed by SEM. In addition, in this embodiment, the hole does not penetrate to the back surface of the workpiece B. Referring to Figure 16 (b), it can be seen that a substantially circular small recess is formed on the front surface of the workpiece B. When measuring the diameter of the recess on the front surface of the workpiece B, the width dx in the left-right direction of the paper surface is 2.5 μm, and the width dy in the up-down direction of the paper surface is 2.4 μm. That is, a small recess with a diameter significantly smaller than the condenser diameter of the laser Lb is formed.

[0111] It is considered that the recess with a diameter significantly smaller than the condenser diameter of the laser Lb is obtained as a result of the following combined processing: the processing of the optical pulse train Pc including multiple ultrashort optical pulses Pca with a picosecond-level time width, and the processing of the optical pulse Pd with a nanosecond-level time width. More specifically, it is speculated that with the optical pulse train Pc having a high peak output, the hole machining progresses. On the other hand, with the long-time energy irradiation of the optical pulse Pd with a low peak output, the thermal processing progresses, whereby the workpiece B (SUS304) is moderately melted to form a recess with a small diameter.

[0112] Figure 16 The embodiment shown has the following inspiration: Two or more optical pulse trains each including one or more optical pulses are irradiated onto the workpiece B with a time interval Δt therebetween, and the time waveforms of at least two of the two or more optical pulse trains are made different from each other, whereby various processing that has been difficult to achieve before can be performed. And such an irradiation method is realized by the following: Two or more pulse trains each including one or more pulses are arranged with a time interval Δt therebetween, and in the current supply step ST2, a drive current id with different time waveforms for at least two of the two or more pulse trains is supplied from the drive circuit 4 to the semiconductor element 2.

[0113] In addition, the concept of the time waveform here includes at least one of the following: the time waveform of each of the one or more pulses in each pulse train, the time width of each of the one or more pulses in each pulse train, and the time interval between the multiple pulses in each pulse train. The time interval Δt is, for example, 200 microseconds or less, and more preferably 1 microsecond or less.

[0114] Figure 17 It is a graph (measured value) showing another embodiment of the time waveform of the laser Lb indicating such an irradiation method. Figure 17 In it, the vertical axis represents the normalized intensity (arbitrary unit), and the horizontal axis represents time (unit: nanosecond). In this embodiment, a light pulse group Pe1 including a single light pulse Pea and a light pulse group Pe2 including a single light pulse Peb are output from the optical amplifier 3. Both the light pulses Pea and Peb are Gaussian pulses, and the time widths (FWHM) are 62 ps and 15 ns respectively. The time interval Δt between the light pulse group Pe1 and the light pulse group Pe2 is 25.8 ns.

[0115] According to the laser processing apparatus 1A of the present embodiment, the pulse width of the light pulse Peb included in one light pulse group Pe2 can also be set to be 10 times or more the pulse width of the light pulse Pea included in the other light pulse group Pe1. In this case, it is preferable that in the current supply step ST2, a drive current id is supplied from the drive circuit 4 to the semiconductor laser element 2, and the drive current id arranges the pulse group corresponding to the light pulse group Pe1 and the pulse group corresponding to the light pulse group Pe2 with a time interval Δt therebetween.

[0116] Figure 18 and Figure 19 It is a graph (measured value) further showing another embodiment. Figure 18 (a) shows a light pulse group Pf1 including a plurality of ultrashort light pulses Pfa and a light pulse group Pf2 including a single light pulse Pfb. Both the ultrashort light pulse Pfa and the light pulse Pfb are Gaussian pulses, and the time widths (FWHM) are 62 ps and 15 ns respectively, and the time interval between the plurality of ultrashort light pulses Pfa is 10 ns. The time interval Δt between the light pulse group Pf1 and the light pulse group Pf2 is 37.4 ns.

[0117] In addition, Figure 18 (b) shows a light pulse group Pg1 including a plurality of ultrashort light pulses Pga, a light pulse group Pg2 including a single light pulse Pgb, and a light pulse group Pg3 including a single light pulse Pgc. Both the ultrashort light pulse Pga and the light pulse Pgb are Gaussian pulses, and the time waveform of the light pulse Pgc is a triangular wave. The time widths (FWHM) of the ultrashort light pulse Pga and the light pulse Pgb are 62 ps and 15 ns respectively, and the time width of the light pulse Pgc is 36 ns. The time interval between the plurality of ultrashort light pulses Pga is 5 nanoseconds in the first half and 10 nanoseconds in the second half. The time interval Δt1 between the light pulse group Pg1 and the light pulse group Pg2 is 58.2 ns, and the time interval Δt2 between the light pulse group Pg2 and the light pulse group Pg3 is 49.9 ns.

[0118] In addition, Figure 19It represents a light pulse group Ph1 including a single light pulse Pha and a light pulse group Ph2 including a single light pulse Phb. Both the light pulses Pha and Phb are Gaussian pulses, with time widths (FWHM) of 62 ps and 12 ns respectively. The time interval Δt between the light pulse group Ph1 and the light pulse group Ph2 is 40.9 ns.

[0119] In addition, Figure 18 and Figure 19 For each of the waveforms shown, a drive current id can be supplied from the drive circuit 4 to the semiconductor laser element 2 in the current supply step ST2, and the drive current id arranges the pulse groups corresponding to each light pulse group Pf1, Pf2 (Pg1 to Pg3 or Ph1, Ph2) with a time interval Δt (or Δt1, Δt2) between them.

[0120] Figures 20 to 24 (a) to (c) are diagrams conceptually showing various time waveforms that can be output from the laser processing apparatus 1A of the present embodiment. In these diagrams, the vertical axis represents the light intensity and the horizontal axis represents the time. Figure 20 (a) and (b) show examples of combining a light pulse train, i.e., a light pulse group Pi, including multiple ultrashort light pulses and a light pulse group Pj including a single Gaussian pulse. Figure 20 (a) shows an example of irradiating the light pulse group Pj after the light pulse group Pi, Figure 20 (b) shows an example of irradiating the light pulse group Pi after the light pulse group Pj.

[0121] In addition, the number of ultrashort light pulses included in the light pulse group Pi is arbitrary. In the illustrated example, the number of ultrashort light pulses is 3. Also, the peak intensities of the respective ultrashort light pulses included in the light pulse group Pi may be equal to each other, or at least one of them may be different from the others. Also, similar to Figure 20 (a) and (b), in each of the examples described below, the order of the light pulse groups can be appropriately replaced.

[0122] Figure 20 (c) shows an example of combining a light pulse group Pk including a single light pulse having a triangular-wave-shaped time waveform with a monotonically increasing light intensity and a light pulse group Pj including a single Gaussian pulse.

[0123] Figure 21 (a) shows an example of combining the light pulse group Pi, a light pulse group Pm including a single ultrashort light pulse, and the light pulse group Pk. In the illustrated example, the number of ultrashort light pulses constituting the light pulse group Pi is 2, and the peak intensities of the respective ultrashort light pulses are equal to each other.

[0124] Figure 21(b) shows an example of combining a light pulse group Pn that includes a train of multiple ultrashort light pulses with monotonically increasing peak intensities of each ultrashort light pulse, and a light pulse group Pp that includes a single light pulse with a stepwise increasing light intensity. The number of ultrashort light pulses included in the light pulse group Pn is arbitrary. In the illustrated example, the number of ultrashort light pulses is 5. Additionally, the order of the light pulse that constitutes the light pulse group Pp is arbitrary. In the illustrated example, the order of the light pulse is 2.

[0125] Figure 21 (c) shows an example of combining a light pulse group Pq that includes a train of multiple ultrashort light pulses with monotonically decreasing peak intensities of each ultrashort light pulse, and a light pulse group Pr that includes a single light pulse with a stepwise decreasing light intensity. The number of ultrashort light pulses included in the light pulse group Pq is arbitrary. In the illustrated example, the number of ultrashort light pulses is 5. Additionally, the order of the light pulse that constitutes the light pulse group Pr is arbitrary. In the illustrated example, the order of the light pulse is 4.

[0126] Figure 22 (a) shows an example of combining a light pulse group Ps that includes a single light pulse with a time waveform having a flat section with a constant light intensity, and two light pulse groups Pm.

[0127] Figure 22 (b) shows an example of combining a light pulse group Pk and a light pulse group Pt that includes a train of multiple light pulses with each light pulse having a triangular-wave-shaped time waveform with monotonically increasing light intensity. The number of triangular-wave-shaped light pulses included in the light pulse group Pt is arbitrary. In the illustrated example, the number of light pulses is 4. Additionally, the peak intensities of each light pulse included in the light pulse group Pt may be equal to each other, or at least one of them may be different from the others.

[0128] Figure 22 (c) shows an example of combining two light pulse groups Pj with different peak intensities of Gaussian pulses and a light pulse group Pi. In the illustrated example, the peak intensity of the Gaussian pulse in the first light pulse group Pj is greater than the peak intensity of the Gaussian pulse in the second light pulse group Pj. Additionally, the number of ultrashort light pulses that constitutes the light pulse group Pi is 2, and the peak intensities of each ultrashort light pulse are equal to each other.

[0129] Figure 23 (a) shows an example of combining a light pulse group Pu that includes a train of multiple ultrashort light pulses with peak intensities that first increase monotonically and then decrease monotonically, and a light pulse group Pj. The number of ultrashort light pulses included in the light pulse group Pu is arbitrary. In the illustrated example, the number of light pulses is 11.

[0130] Figure 23(b) represents an optical pulse group Pv that includes an optical pulse train containing multiple ultrashort optical pulses and the peak intensity of each ultrashort optical pulse monotonically decreases and then monotonically increases. The number of ultrashort optical pulses included in the optical pulse group Pv is arbitrary. In the illustrated example, the number of optical pulses is 10.

[0131] Figure 23 (c) represents an example of combining an optical pulse group Pw that includes a single optical pulse having a time waveform with the optical intensity monotonically increasing starting from an optical intensity greater than zero, and the optical pulse group Pi. In the illustrated example, the number of ultrashort optical pulses constituting the optical pulse group Pi is 3, and the peak intensities of the respective ultrashort optical pulses are equal to each other.

[0132] Figure 24 (a) represents an example of combining an optical pulse group Px that includes a single optical pulse having a triangular-wave-shaped time waveform with the optical intensity monotonically increasing, and the optical pulse group Pi. In the illustrated example, the number of ultrashort optical pulses constituting the optical pulse group Pi is 6, and the peak intensities of the respective ultrashort optical pulses are equal to each other.

[0133] Figure 24 (b) represents an example of combining an optical pulse group Py that includes a single optical pulse having a time waveform with a flat section where the optical intensity is constant, the optical pulse group Pi, and an optical pulse group Pz that includes a single optical pulse having a triangular-wave-shaped time waveform with the optical intensity monotonically decreasing. In the illustrated example, the number of ultrashort optical pulses constituting the optical pulse group Pi is 4, and the peak intensities of the respective ultrashort optical pulses are equal to each other.

[0134] Figure 24 (c) represents an example of combining multiple optical pulse groups Pj at equal intervals. The peak intensities of the Gaussian pulses of each optical pulse group Pj may be equal to each other, or at least one of them may be different from the others.

[0135] Figure 25 is a diagram showing an example of combining multiple optical pulse groups Pi, Pj, and Py corresponding to multiple processing processes respectively. Figure 25 In it, the vertical axis represents the optical intensity and the horizontal axis represents the time. As Figure 25 shown, first, the optical pulse group Pi corresponding to a certain processing process is irradiated, the optical pulse group Pj corresponding to another processing process is irradiated after a time Δt3, and the optical pulse group Py corresponding to yet another processing process is irradiated after a time Δt4. In this case, these processing processes that were previously performed using different laser processing apparatuses can be continuously performed in a short period of time.

[0136] The pulse width (FWHM) of each ultrashort optical pulse included in the optical pulse train Pi is, for example, 1 picosecond or more and 1 nanosecond or less. The pulse width (FWHM) of the Gaussian pulse included in the optical pulse train Pj is, for example, 1 nanosecond or more and 1 microsecond or less. The time width of the flat section of the optical pulse constituting the optical pulse train Py is, for example, 1 microsecond or more and 1 millisecond or less. The time intervals Δt3 and Δt4 are, for example, 1 millisecond or less, and more preferably 200 microseconds or less.

[0137] Figures 26 to 29 This shows an example when multiple machining processes are continuously performed in a short period using the laser processing apparatus 1A of the present embodiment. Figures 26 to 29 Each (a) shows a workpiece B having a plurality of (three in the figure) layers B1 to B3 made of different constituent materials, and a laser Lb irradiated onto the workpiece B. Figures 26 to 29 Each (b) shows the time waveform of the laser Lb during each machining process.

[0138] In this example, first, by irradiating the optical pulse train Py shown in Figure 26 (b) onto the uppermost layer B1, the surface to be machined is cleaned. Among the optical pulses constituting the optical pulse train Py, the time width of the flat section where the light intensity is constant is, for example, 1 millisecond. Next, by irradiating the optical pulse train Pi shown in Figure 27 (b) onto the uppermost layer B1, as shown in Figure 27 (a), a hole B1a is formed in the uppermost layer B1. The time width of each optical pulse constituting the optical pulse train Pi is, for example, 60 picoseconds.

[0139] Next, by irradiating the optical pulse train Pp shown in Figure 28 (b) onto the layer B2, as shown in Figure 28 (a), the layer B2 is locally modified to form a modified region B2a. The time width of the optical pulse constituting the optical pulse train Pp is, for example, 30 nanoseconds. Next, by irradiating the optical pulse train Pi shown in Figure 29 (b) onto the layer B2, and then irradiating the optical pulse train Pj onto the layer B3, as shown in Figure 29 (a), a hole B2b is formed in the layer B2 and a hole B3a is formed in the layer B3, respectively. The time width of each optical pulse constituting the optical pulse train Pi is, for example, 60 picoseconds, and the FWHM of the Gaussian pulse constituting the optical pulse train Pj is, for example, 30 nanoseconds.

[0140] In this way, in the workpiece B formed by laminating different materials, through holes can be formed in a short period.

[0141] In addition, the combination of multiple optical pulse trains corresponding to multiple machining processes can also be in the following manner. Figure 30 (a) is a diagram showing the combination of the optical pulse trains Pi, Py, and Pk corresponding to a certain machining process.Figure 30 (b) is a diagram showing a set of optical pulses Pj corresponding to the next processing step. Figure 30 (c) is a diagram showing sets of optical pulses Pi, Pi, and Pm corresponding to the next processing step after that. As shown in this example, multiple sets of optical pulses can be irradiated onto the workpiece B in each processing step.

[0142] Here, an embodiment in which multiple sets of optical pulses corresponding to respective multiple processing steps are irradiated onto the workpiece B will be described. Figure 31 is a diagram showing the time waveform of the laser Lb irradiated in this embodiment. As Figure 31 shown, in this embodiment, the laser Lb is set to include the following: multiple sets of optical pulses Pi having a time waveform suitable for drilling (pre-processing), and multiple sets of optical pulses Pj having a time waveform suitable for subsequent deburring (post-processing).

[0143] The number of sets of optical pulses Pi is set to 300, the number of multiple optical pulses included in the set of optical pulses Pi is set to 10, the energy of each optical pulse is set to 2 μJ, the time width (FWDM) of each optical pulse is set to 80 ps, and the time interval between pulses is set to 2 ns. Additionally, the number of sets of optical pulses Pj is set to 300, the energy of the Gaussian pulses constituting the set of optical pulses Pj is set to 40 μJ, and the time width (FWDM) of the Gaussian pulses is set to 137 ns. Further, the time interval Δt5 between the set of optical pulses Pi and the set of optical pulses Pj is set to 1 s, which is the time for the workpiece B to reach a stable state after the processing by the set of optical pulses Pi. The time interval between the sets of optical pulses Pi is set to 3.3 ms, and the time interval between the sets of optical pulses Pj is set to 3.3 ms.

[0144] Figure 32 and Figure 33 is a diagram showing the SEM image of the holes formed in the workpiece B. Figure 32 shows the (a) front side (laser irradiation surface) and (b) back side of the workpiece B after irradiating the set of optical pulses Pi and before irradiating the set of optical pulses Pj. Additionally, Figure 33 shows the (a) front side and (b) back side of the workpiece B after irradiating the set of optical pulses Pj.

[0145] Comparing Figure 32 (a) with Figure 33 (a), it can be seen that the burrs around the holes generated after irradiating the set of optical pulses Pi are melted and smoothed by irradiating the set of optical pulses Pj. Additionally, comparing Figure 32 (b) with Figure 33 (b), it can be seen that the aperture diameter on the side opposite to the laser irradiation surface is melted by irradiating the set of optical pulses Pj and thus becomes smaller.

[0146] In addition, when measuring the diameter of the hole on the back surface of the workpiece B, before irradiating the light pulse group Pj ( Figure 32 (b)), the width dx in the left-right direction of the paper surface is 8.3 μm, the width dy in the up-down direction of the paper surface is 8.1 μm, and the average width is 8.2 μm. In contrast, after irradiating the light pulse group Pj ( Figure 33 (b)), the width dx in the left-right direction of the paper surface is 2.9 μm, the width dy in the up-down direction of the paper surface is 2.7 μm, and the average width is 2.8 μm.

[0147] The effects obtained by the laser processing apparatus 1A and the laser processing method of the present embodiment described above will be described.

[0148] In the laser processing apparatus 1A and the laser processing method of the present embodiment, the waveform output unit 6 outputs the input waveform data Da, and the drive circuit 4 supplies the drive current id having a time waveform corresponding to the input waveform data Da to the semiconductor laser element 2. Therefore, by including an arbitrary time waveform in the input waveform data Da, light pulses having an arbitrary time waveform can be output from the semiconductor laser element 2. In addition, by including a plurality of pulse groups having a time difference in the input waveform data Da, a plurality of light pulse groups having a time difference can be output from the semiconductor laser element 2.

[0149] That is, according to the present embodiment, a plurality of light pulse groups having different time waveforms can be irradiated to the workpiece B with a time difference. In addition, since a plurality of light pulse groups are output from a single semiconductor laser element 2 on a single optical path, the device structure can be miniaturized compared with the methods described in Patent Documents 1 and 2.

[0150] In addition, by irradiating a plurality of light pulse groups having different time waveforms to the workpiece B in a short period of time (continuously), the plurality of light pulse groups act on the workpiece B in a combined manner, and various processing shapes and processing qualities that were difficult to achieve before, such as forming a concave portion having a diameter smaller than the irradiation diameter as shown in Figure 16 (b), can be realized.

[0151] In addition, as in the past, if a light source having an appropriate time waveform is prepared in each processing process and each processing process is performed, an operation for replacing the light source is required. In addition, after replacing the light source, an operation for correcting the deviation of the optical axis is further required, and the time required for the processing becomes longer. In contrast, according to the present embodiment, as shown in Figures 26 to 29 and Figures 31 to 33 , a plurality of light pulse groups having time waveforms suitable for respective multiple processing processes can be generated from a single semiconductor laser element 2 in a short period of time (continuously), and the time required for the processing can be significantly shortened.

[0152] In the present embodiment, the drive circuit 4 (current supply step ST2) may also include: a D / A conversion unit 46 (D / A conversion step ST21) that converts digital input waveform data Da into an analog drive signal Sd; and a current conversion unit 45 (current conversion step ST22) that converts the drive signal Sd into a drive current id. Further, the D / A conversion unit 46 (D / A conversion step ST21) may sequentially convert continuous multiple interval waveform data DD1 to DD4 obtained by dividing the time waveform of the divided input waveform data Da into the drive signal Sd while giving a time difference. Thereby, the drive signal Sd can be made faster, and the time resolution of the time waveform of the optical pulse can be improved.

[0153] In the present embodiment, the time width of one or more pulses in each optical pulse group may also be 1 microsecond or less. By irradiating the workpiece B with optical pulses having a short time width in this way, the thermal influence on the periphery of the processed area can be suppressed, and the light intensity of the laser Lb can be increased, thereby improving the processing accuracy.

[0154] In the present embodiment, the time interval between the optical pulse groups may also be 200 microseconds or less. In this case, the workpiece B can be irradiated with the laser Lb including two or more optical pulse groups in a short time, and the time required for processing can be shortened.

[0155] In the present embodiment, the waveform output unit 6 (in the current supply step ST2) may also change the time waveform of at least one pulse group among two or more pulse groups in the laser Lb during the processing of the workpiece B. In the present embodiment, the time waveform of the pulse group can be changed in this way during the processing of the workpiece B. Therefore, multiple stages of processing processes with different time waveforms required for the laser can be continuously performed in a short time, and the time required for processing can be shortened.

[0156] In the present embodiment, the pulse width of one or more optical pulses in one optical pulse group may also be 10 times or more the pulse width of one or more optical pulses in another optical pulse group. According to the present embodiment, for example, optical pulses with significantly different pulse widths can be continuously output in a short time, and various processing conditions can be adapted.

[0157] (Modification example)

[0158] Figure 34 It is a block diagram showing the structure of a modification example of the above embodiment. As Figure 34 shown, the laser processing apparatus 1B of this modification example further includes a spatial light modulator 7 and a drive unit 8 in addition to the structure of the laser processing apparatus 1A of the above embodiment.

[0159] The spatial light modulator 7 has a plurality of pixels arranged in a two-dimensional pattern, and individually modulates the phase of the incident light in each pixel. The spatial light modulator 7 can be either a transmissive type or a reflective type. In one example, the spatial light modulator 7 is a liquid crystal type LCOS-SLM (Liquid Crystal on Silicon-Spatial Light Modulator).

[0160] The spatial light modulator 7 is disposed on the optical path between the semiconductor laser element 2 and the processing optical system 5 (in the illustrated example, on the optical path between the optical amplifier 3 and the processing optical system 5). The spatial light modulator 7 spatially modulates the phase of the laser Lb output from the optical amplifier 3, and outputs the modulated laser Lc to the processing optical system 5. The laser Lc is irradiated onto the workpiece B via the processing optical system 5. That is, Figure 6 In the light irradiation step ST6 shown, the laser Lb is irradiated onto the workpiece B via the spatial light modulator 7.

[0161] The drive unit 8 is a circuit for applying a voltage signal Sv for driving the spatial light modulator 7 to each pixel of the spatial light modulator 7. The magnitude of the voltage signal Sv for each pixel is determined based on the computer-generated hologram (CGH: Computer Generated Hologram) generated in the waveform output unit 6.

[0162] Figure 35 This is an example of a plurality of light pulse groups irradiated onto the workpiece B in this modified example. For example, the light pulse group Py1 is irradiated onto the workpiece B, and after a time Δt6, the light pulse group Py2 is irradiated onto the workpiece B, and after a time Δt7, the light pulse group Py3 is further irradiated onto the workpiece B. Such an irradiation method is achieved by including pulse groups corresponding to the pulse groups Py1, Py2, and Py3 in the drive current id from the drive circuit 4.

[0163] Here, in this modified example, the spatial light modulator 7 presents a CGH as follows, which is used to make the positions of the irradiated light pulse groups Py1, Py2, and Py3 on the workpiece B different for each light pulse group Py1, Py2, and Py3, or to make the irradiation position of at least one light pulse group Py1, Py2, or Py3 different from the irradiation positions of other light pulse groups. In other words, the spatial light modulator 7 sequentially presents a CGH for irradiating the first light pulse group Py1 (or Py2) to the first irradiation position, and a CGH for irradiating the second light pulse group Py2 (or Py3) to a second irradiation position different from the first irradiation position. In addition, the above time Δt6 and Δt7 are greater than the time required for the spatial light modulator 7 to change the CGH.

[0164] According to this modification example, light pulse groups with different time waveforms can be irradiated to at least two processed parts, and these light pulse groups can be irradiated continuously in a short time. Therefore, compared with the existing laser processing apparatus, the time required for processing can be significantly shortened.

[0165] The laser processing apparatus and the laser processing method are not limited to the above-described embodiments and structural examples, and various modifications can also be made. For example, in the above-described embodiment, the target waveform data is stored in the waveform output unit 6, but the target waveform data may be input from the outside of the laser processing apparatus 1A. In addition, the optical amplifier 3 and / or the optical isolator 12 may be omitted as needed.

[0166] In addition, in the above-described embodiment, the waveform output unit 6 includes the waveform adjustment unit 32 and the comparison unit 33, and feeds back the time waveform of the feedback laser Lb to generate the input waveform data Da. However, a structure for such feedback may not be provided, and the target waveform data Db from the computer 31 may be directly used to generate the laser Lb.

[0167] The laser processing apparatus of the above-described embodiment is configured to include: a semiconductor laser element; a waveform output unit that outputs input waveform data; a drive circuit that generates a drive current having a time waveform corresponding to the input waveform data and supplies the drive current to the semiconductor laser element; and an optical system that irradiates the laser output from the semiconductor laser element onto a workpiece. The semiconductor laser element outputs a laser in which two or more light pulse groups each including one or more light pulses are arranged at intervals of time, and the time waveforms of at least two of the two or more light pulse groups are different from each other. The time waveform includes at least one of the time waveforms of one or more light pulses, the time widths of one or more light pulses, and the time intervals of a plurality of light pulses.

[0168] The laser processing method of the above-described embodiment is configured to include: a current supply step of generating a drive current having a time waveform corresponding to the input waveform data and supplying the drive current to the semiconductor laser element; and a light irradiation step of irradiating the laser output from the semiconductor laser element onto a workpiece. In the light irradiation step, the semiconductor laser element outputs a laser in which two or more light pulse groups each including one or more light pulses are arranged at intervals of time, and the time waveforms of at least two of the two or more light pulse groups are different from each other. The time waveform includes at least one of the time waveforms of one or more light pulses, the time widths of one or more light pulses, and the time intervals of a plurality of light pulses.

[0169] In the above-described laser processing apparatus, it may also be configured such that the drive circuit includes: a D / A conversion unit that converts digital input waveform data into an analog drive signal; and a current conversion unit that converts the drive signal into a drive current. The D / A conversion unit sequentially converts continuous multiple interval waveform data obtained by dividing the time waveform of the input waveform data into drive signals while giving a time difference.

[0170] In the above-described laser processing method, it may also be configured such that the current supply step includes: a D / A conversion step that converts digital input waveform data into an analog drive signal; and a current conversion step that converts the drive signal into a drive current. In the D / A conversion step, continuous multiple interval waveform data obtained by dividing the time waveform of the input waveform data are sequentially converted into drive signals while giving a time difference.

[0171] According to these apparatuses and methods, the drive signal can be made faster, and the time resolution of the time waveform of the optical pulse can be improved.

[0172] In the above-described laser processing apparatus and laser processing method, it may also be configured such that the time width of each one or more optical pulses in each optical pulse group is 1 μs or less. By irradiating the workpiece with optical pulses having such a short time width, the thermal influence on the periphery of the processed area can be suppressed, and the light intensity of the laser can be increased, thereby improving the processing accuracy.

[0173] In the above-described laser processing apparatus and laser processing method, it may also be configured such that the time interval between two or more optical pulse groups is 200 μs or less. In this case, two or more optical pulse groups can be irradiated onto the workpiece in a short time, and the time required for processing can be shortened.

[0174] In the above-described laser processing apparatus, the waveform output unit may be configured to change the time waveform of at least one optical pulse group among two or more optical pulse groups during the processing of the workpiece. Further, in the above-described laser processing method, it may also be configured to change the time waveform of at least one optical pulse group among two or more optical pulse groups during the processing of the workpiece.

[0175] In the above-described apparatuses and methods, the time waveform of the optical pulse group can be easily changed during the processing of the workpiece in this way. Therefore, processing in multiple stages with different time waveforms required for the laser can be continuously performed in a short time, and the time required for processing can be shortened.

[0176] In the above-described laser processing apparatus and laser processing method, it may also be configured such that in at least two optical pulse groups, the pulse width of one or more optical pulses in one optical pulse group is 10 times or more the pulse width of one or more optical pulses in another optical pulse group. According to the above-described apparatuses and methods, for example, optical pulses with significantly different pulse widths can be continuously output in a short time, and various processing conditions can be adapted.

[0177] The above laser processing apparatus may also be configured to further include a spatial light modulator, which is disposed on the optical path between the semiconductor laser element and the optical system. The spatial light modulator sequentially presents a hologram for irradiating the laser corresponding to the first light pulse group included in two or more light pulse groups to the first irradiation position, and a hologram for irradiating the laser corresponding to the second light pulse group to the second irradiation position different from the first irradiation position.

[0178] The above laser processing method may also be configured such that, in the light irradiation step, the workpiece is irradiated with the laser via the spatial light modulator, and the spatial light modulator sequentially presents a hologram for irradiating the laser corresponding to the first light pulse group included in two or more light pulse groups to the first irradiation position, and a hologram for irradiating the laser corresponding to the second light pulse group to the second irradiation position different from the first irradiation position.

[0179] In this case, the laser can be irradiated to a plurality of processing parts continuously in a short time, and the time required for processing can be shortened.

[0180] Industrial Applicability

[0181] The present invention can be used as a laser processing apparatus and a laser processing method capable of miniaturizing a structure for irradiating a workpiece with a plurality of light pulses having different time waveforms.

[0182]

Reference Signs

[0183] 1A, 1B... Laser processing apparatus;

[0184] 2... Semiconductor laser element;

[0185] 3... Optical amplifier;

[0186] 4... Drive circuit;

[0187] 5... Processing optical system;

[0188] 6... Waveform output unit;

[0189] 7... Spatial light modulator;

[0190] 8... Drive unit;

[0191] 11... Bias current control unit;

[0192] 12, 21, 23, 27, 29... Optical isolator;

[0193] 13... Optical branching unit;

[0194] 14... Optical detection unit;

[0195] 15... Optical waveform detection unit;

[0196] 22... Optical fiber amplifier;

[0197] 24... Band - pass filter;

[0198] 25... Optical fiber connector;

[0199] 26... Collimating lens;

[0200] 28, 30... Solid - state laser amplifier;

[0201] 31... Computer;

[0202] 32... Waveform adjustment unit;

[0203] 33... Comparison unit;

[0204] 41... Control board;

[0205] 41a... CPU;

[0206] 41b... High - speed DAC interface;

[0207] 42... Waveform data storage unit;

[0208] 43... Waveform timing adjustment unit;

[0209] 44... Waveform signal generation unit;

[0210] 45... Current conversion unit;

[0211] 46... D / A conversion unit;

[0212] B... Workpiece;

[0213] B1 - B3... Layers;

[0214] B1a, B2b, B3a... Holes;

[0215] B2a... Modified region;

[0216] Da... Input waveform data;

[0217] Db... Target waveform data;

[0218] Dc... Differential data;

[0219] DD1 - DD4... Interval waveform data;

[0220] F1 - F3... Optical fibers;

[0221] id... Driving current;

[0222] La, Lb, Lc... lasers;

[0223] Pa... optical pulse (Gaussian pulse);

[0224] Pb, Pc, Pe1, Pe2, Pf1, Pf2, Pg1, Pg2, Pg3, Ph1, Ph2, Pi~Pz, Py1, Py2, Py3... optical pulse groups;

[0225] Pba, Pca, Pfa, Pga... ultrashort optical pulses;

[0226] Pd, Pea, Peb, Pfb, Pgb, Pgc, Pha, Phb... optical pulses;

[0227] Sc... optical intensity signal;

[0228] Sd... drive signal;

[0229] Sv... voltage signal;

[0230] TA... delay time;

[0231] Δt, Δt1, Δt2, Δt5... time intervals.

Claims

1. A laser processing apparatus, comprising: A semiconductor laser element; A waveform output unit that outputs input waveform data; A drive circuit that generates a drive current having a time waveform corresponding to the input waveform data and supplies the drive current to the semiconductor laser element; and An optical system that irradiates a workpiece with the laser output from the semiconductor laser element, The semiconductor laser element outputs the laser, and the laser is formed by arranging two or more groups of optical pulses each including one or more optical pulses with a time interval therebetween, Among the two or more groups of optical pulses, the time waveforms of at least two of the groups of optical pulses are different from each other, In the time waveform, at least one of the time waveforms of the one or more optical pulses, the time widths of the one or more optical pulses, and the time intervals of the plurality of optical pulses is included, The time width of the one or more optical pulses in one of the at least two groups of optical pulses is 10 times or more the time width of the one or more optical pulses in the other group of optical pulses, The time width of the one or more optical pulses in the other group of optical pulses is 1 picosecond or more and 1 nanosecond or less.

2. The laser processing apparatus according to claim 1, Wherein, The drive circuit has: A D / A conversion unit that converts the digital input waveform data into an analog drive signal; and A current conversion unit that converts the drive signal into the drive current, The D / A conversion unit sequentially converts the drive signal while giving a time difference to continuous multiple interval waveform data obtained by dividing the time waveform of the input waveform data.

3. The laser processing apparatus according to claim 1 or 2, Wherein, The time width of each of the one or more optical pulses in each group of optical pulses is 1 microsecond or less.

4. The laser processing apparatus according to any one of claims 1 to 3, Wherein, The time interval between the two or more groups of optical pulses is 200 microseconds or less.

5. The laser processing apparatus according to any one of claims 1 to 4, Wherein, The waveform output unit changes the time waveform of at least one of the two or more groups of optical pulses during the processing of the workpiece.

6. The laser processing apparatus according to any one of claims 1 to 5, Wherein, It further includes: a spatial light modulator disposed on the optical path between the semiconductor laser element and the optical system, The spatial light modulator sequentially presents a hologram for irradiating the laser corresponding to the first group of optical pulses included in the two or more groups of optical pulses to a first irradiation position, and a hologram for irradiating the laser corresponding to the second group of optical pulses to a second irradiation position different from the first irradiation position.

7. A laser processing method, comprising: A current supply step of generating a drive current having a time waveform corresponding to input waveform data and supplying the drive current to a semiconductor laser element; and A light irradiation step of irradiating a workpiece with the laser output from the semiconductor laser element, In the light irradiation step, the semiconductor laser element outputs the laser, and the laser is formed by arranging two or more groups of optical pulses each including one or more optical pulses with a time interval therebetween. The time waveforms of at least two of the two or more groups of optical pulses are different from each other. The time waveform includes at least one of the time waveforms of the one or more optical pulses, the time widths of the one or more optical pulses, and the time intervals of the plurality of optical pulses. The time width of the one or more optical pulses in one group of optical pulses among the at least two groups of optical pulses is 10 times or more the time width of the one or more optical pulses in other groups of optical pulses. The time width of the one or more optical pulses in the other groups of optical pulses is 1 picosecond or more and 1 nanosecond or less.

8. The laser processing method according to claim 7, wherein The current supply step includes: a D / A conversion step that converts the digital input waveform data into an analog drive signal; and a current conversion step that converts the drive signal into the drive current, In the D / A conversion step, the continuous plurality of interval waveform data obtained by dividing the time waveform of the input waveform data are sequentially converted into the drive signal while giving a time difference.

9. The laser processing method according to claim 7 or 8, wherein The time width of each of the one or more optical pulses in each group of optical pulses is set to 1 microsecond or less.

10. The laser processing method according to any one of claims 7 to 9, wherein The time interval between the two or more groups of optical pulses is set to 200 microseconds or less.

11. The laser processing method according to any one of claims 7 to 10, wherein During the processing of the workpiece, the time waveform of at least one of the two or more groups of optical pulses is changed.

12. The laser processing method according to any one of claims 7 to 11, wherein In the light irradiation step, the laser is irradiated onto the workpiece via a spatial light modulator, and the spatial light modulator sequentially presents a hologram for irradiating the laser corresponding to the first group of optical pulses included in the two or more groups of optical pulses to a first irradiation position, and a hologram for irradiating the laser corresponding to the second group of optical pulses to a second irradiation position different from the first irradiation position.

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