JP5995767B2 - Laser processing apparatus and laser processing method - Google Patents

Description

  The present invention relates to a laser processing apparatus that performs laser processing by emitting a pulse laser, and a laser processing method.

  In a gas laser such as a carbon dioxide laser, impurities in the laser medium gas affect the discharge. For this reason, variation occurs in pulse energy for each emitted laser pulse. When laser pulses are used for drilling, if the pulse energy varies, the processing quality varies.

  Patent Document 1 below discloses a laser oscillation method that reduces variations in pulse energy. In the method disclosed in Patent Document 1, the energy value of the laser beam emitted from the laser oscillator is measured a plurality of times during one pulse excitation. A plurality of measured energy values are added, and a predicted total energy value of the laser light oscillated by the pulse excitation is predicted. The excitation time is controlled based on this expected total energy value. Thereby, the total energy value (pulse energy) can be stabilized.

Japanese Patent Laid-Open No. 2002-299736

  When the pulse width is relatively long, for example, about several hundred μs, even if the delay time from the laser oscillation command to the rise of the laser pulse varies, the pulse energy is adjusted by the method disclosed in Patent Document 1 above. Is possible. However, when the pulse width is short, for example, several tens of μs, it is difficult to control the excitation time in consideration of energy detection sensitivity and calculation time.

  An object of the present invention is to provide a laser processing apparatus and a laser processing method capable of stabilizing pulse energy for each pulse even when the delay time from the laser oscillation command to the rise of the laser pulse varies. is there.

According to one aspect of the invention,
A laser light source that starts laser oscillation in synchronization with a laser oscillation start trigger received from outside, and stops laser oscillation in synchronization with a laser oscillation stop trigger;
A photodetector for detecting a laser pulse emitted from the laser light source;
The laser oscillation start trigger is given to the laser light source, and the time to give the laser oscillation stop trigger to the laser light source is determined based on the detection time of the laser pulse by the photodetector, and the laser is determined at the determined time. There is provided a laser processing apparatus having a control device that applies an oscillation stop trigger to the laser light source.

According to another aspect of the invention,
In synchronization with the laser oscillation start trigger received from the controller starts laser oscillation, the laser light source to stop the laser oscillation in synchronization with the laser oscillation stop trigger, the steps of the control device gives the laser oscillation start trigger,
A step in which a photodetector detects a laser pulse emitted from the laser light source, and the controller detects a rise time based on a detection result of the photodetector ;
From the rise time of the laser pulse, the time that elapsed time corresponding to the target pulse width set in advance, the laser processing method provided with a step of said controller gives said laser oscillation stop trigger to the laser light source Is done.

  By determining the time to give the laser oscillation stop trigger to the laser light source based on the detection time of the laser pulse, even if the delay time from the time the laser oscillation start trigger is given to the rise of the laser pulse varies, the pulse energy is Can be stabilized.

FIG. 1 is a schematic diagram of a laser processing apparatus according to an embodiment. FIG. 2 is a cross-sectional view of a laser oscillator of the laser processing apparatus according to the embodiment and a block diagram of a drive circuit. FIG. 3 is a timing chart of the trigger signal given from the control device to the laser light source, the high frequency voltage applied to the discharge electrode of the laser oscillator, the discharge current flowing through the discharge electrode, and the light output from the laser oscillator. FIG. 4 shows the relationship between the pulse energy and the delay time until the laser pulse rises under the condition that the trigger time width from the time when the laser oscillation start trigger is applied to the laser light source to the time when the laser oscillation stop trigger is applied is constant. It is a graph which shows. FIG. 5 is a flowchart of processing executed by the control device of the laser processing apparatus according to the embodiment. FIG. 6 is a timing chart of the trigger signal given from the control device to the laser light source, the high-frequency voltage applied to the discharge electrode of the laser oscillator, the discharge current flowing through the discharge electrode, and the light output from the laser oscillator.

  FIG. 1 shows a schematic diagram of a laser processing apparatus according to an embodiment. The laser light source 1 starts laser oscillation in synchronization with the laser oscillation start trigger received from the control device 20, and stops laser oscillation in synchronization with the laser oscillation stop trigger. When laser oscillation is started, the laser light source 1 emits a laser pulse.

  The laser light source 1 includes a laser oscillator 10 and a drive circuit 11. As the laser oscillator 10, a gas laser oscillator such as a carbon dioxide laser oscillator is used. A laser oscillation start trigger and a laser oscillation stop trigger are given to the drive circuit 11 from the control device 20. Upon receiving the laser oscillation start trigger, the drive circuit 11 starts supplying power to the laser oscillator 10. When the laser oscillation stop trigger is received, the supply of power to the laser oscillator 10 is stopped.

  The laser beam emitted from the laser light source 1 is branched into a transmitted beam and a reflected beam by the partial reflection mirror 21. The reflected beam enters the photodetector 22. When the light detector 22 detects light, it sends a detection signal to the control device 20. The control device 20 determines a time at which a laser oscillation stop trigger is given to the laser light source 1 with reference to the time when the detection signal is received from the photodetector 22, that is, the rising time of the laser pulse. At the determined time, a laser oscillation stop trigger is given to the laser light source 1.

The transmitted beam that has traveled straight through the partial reflecting mirror 21 passes through the spot position stabilizing optical system 12 and enters the aspherical lens 13. The spot position stabilizing optical system 12 includes a plurality of convex lenses, and stabilizes the position of the beam spot at the position where the aspherical lens 13 is disposed even if the traveling direction of the laser beam emitted from the laser light source 1 is deviated. The aspheric lens 13 changes the profile of the laser beam. For example, a Gaussian beam profile is changed to a top flat beam profile.

  The laser beam transmitted through the aspherical lens 13 is collimated by the collimating lens 14 and then enters the mask 15. The mask 15 includes a transmission window and a light shielding portion, and shapes the beam cross section of the laser beam. The laser beam transmitted through the transmission window of the mask 15 enters the beam scanner 18 via the field lens 16 and the folding mirror 17. The beam scanner 18 scans the laser beam in a two-dimensional direction. For example, a galvano scanner is used as the beam scanner 18.

  The laser beam scanned by the beam scanner 18 is condensed by the fθ lens 19 and enters the workpiece 30. The workpiece 30 is held on the stage 25. The field lens 16 and the fθ lens 19 image the transmission window of the mask 15 on the surface of the workpiece 30. The stage 25 moves the workpiece 30 in a direction parallel to the surface.

  FIG. 2 shows a cross-sectional view of the laser oscillator 10 according to the embodiment and a block diagram of a drive circuit. A blower 40, a pair of discharge electrodes 41, a heat exchanger 46, and a laser medium gas are accommodated in the chamber 50. A discharge space 42 is defined between the pair of discharge electrodes 41. The discharge of the discharge space 42 excites the laser medium gas. In FIG. 2, a cross section orthogonal to the length direction of the discharge electrode 41 is shown. For the blower 40, for example, a turbo blower is used. Instead of a turbo blower, a cross flow fan, an axial flow fan or the like may be used. Each of the discharge electrodes 41 includes a conductive member 43 and a ceramic member 44. The ceramic member 44 isolates the conductive member 43 and the discharge space 42.

  A circulation path from the blower 40 to the blower 40 via the discharge space 42 between the discharge electrodes 41 and the heat exchanger 46 is formed in the chamber 50. The heat exchanger 46 cools the laser medium gas that has become hot due to the discharge.

  A pair of terminals 51 are attached to the wall surface of the chamber 50. The conductive member 43 of the discharge electrode 41 is connected to the terminal 51 by an in-chamber current path 52, respectively. The terminal 51 is connected to the drive circuit 11 by a chamber outside current path 55.

  3 shows a trigger signal given from the control device 20 (FIG. 1) to the drive circuit 11 (FIG. 1), a high-frequency voltage applied to the discharge electrode 41 (FIG. 2), a discharge current flowing through the discharge electrode 41, and a laser oscillator. 10 shows a timing chart of the light output emitted from 10 (FIG. 1).

  At time t1, the trigger signal rises. The rising edge of the trigger signal corresponds to a laser oscillation start trigger. When the drive circuit 11 receives the laser oscillation start trigger at time t <b> 1, the drive circuit 11 applies a high-frequency voltage to the discharge electrode 41. The frequency of the high frequency voltage is 2 MHz, for example. When the discharge starts at time t2 after the high frequency voltage is applied, the discharge current starts to flow.

After the discharge starts, the optical output (laser pulse) rises at time t3 when the gain in the optical resonator of the laser oscillator 10 exceeds the loss. That is, the laser pulse rises at time t3 when the delay time Td elapses from time t1 when the laser oscillation start trigger is given. The light output shows a sharp peak instantaneously at the rise, and then stabilizes. When the laser pulse rises, light is detected by the photodetector 22 (FIG. 1), and a detection signal is sent to the control device 20 (FIG. 1) .

The control device 20 determines a time t4 at which a laser oscillation stop trigger is given to the laser light source 1 with reference to the time when the detection signal is received from the photodetector 22, that is, the rising time t3 of the laser pulse. For example, the time t4 is determined so that the time width Pd from the laser pulse detection time t3 to the time t4 is constant.

  At time t4, the control device 20 applies a laser oscillation stop trigger to the laser light source 1 by lowering the trigger signal. When the drive circuit 11 receives the laser oscillation stop trigger from the control device 20, the drive circuit 11 stops applying the high-frequency voltage. When the high frequency voltage is no longer applied to the discharge electrode 41, the discharge stops, the discharge current stops flowing, and the light output becomes 0 (the laser pulse falls). The time width from time t3 to time t4 corresponds to the pulse width Pd of the laser pulse. The elapsed time from the time t1 at which the laser oscillation start trigger is applied to the time t4 at which the laser oscillation stop trigger is applied is referred to as a trigger time width Te.

  FIG. 4 shows the relationship between the delay time Td and the pulse energy of the laser pulse when the control is performed under a condition where the trigger time width Te is constant. The horizontal axis represents the delay time Td, and the vertical axis represents the pulse energy. Since the trigger time width Te is constant, the sum of the delay time Td and the pulse width Pd (FIG. 3) is constant. For this reason, as the delay time Td becomes longer, the pulse width Pd becomes shorter. As the pulse width Pd decreases, the pulse energy decreases. When the laser oscillation is controlled so that the trigger time width Te is constant, it can be seen that the pulse energy varies due to variations in the delay time Td.

  Next, a laser processing method using the laser processing apparatus according to the embodiment will be described with reference to FIGS. Prior to laser processing, the workpiece 30 is first held on the stage 25 (FIG. 1), and the stage 25 is moved to position the workpiece 30. A plurality of processing points are defined in the processing object 30 within a range that can be scanned by the beam scanner 18. During laser processing, the control device 20 controls the beam scanner 18 so that the laser pulses are incident on the processing points on the processing object 30 in order to perform drilling processing.

  FIG. 5 shows a flowchart of processing executed by the control device 20 (FIG. 1) of the laser processing apparatus according to the embodiment. FIG. 6 shows a timing chart of the trigger signal, the high frequency voltage, the discharge current, and the light output. When the workpiece 30 is held on the stage 25 and the positioning of the workpiece 30 is completed, the beam scanner 18 is controlled so that a laser pulse is incident on a workpiece to be processed first. In step S1, the process waits until the positioning of the beam scanner 18 is completed. When the positioning of the beam scanner 18 is completed, a laser oscillation start trigger is given to the laser light source 1 in step S2. Step S2 corresponds to times t11, t21, and t31 shown in FIG.

  When a laser oscillation start trigger is given to the laser light source 1, a high frequency voltage is applied to the laser oscillator 10 (FIG. 1), and a discharge current flows. The laser pulses Lp1, Lp2, and Lp3 rise at times t12, t22, and t32 when the delay times Td1, Td2, and Td3 have elapsed from the times t11, t21, and t31 when the laser oscillation start trigger is given, respectively. The delay times Td1, Td2, and Td3 are not all equal because of the vibration of the reflecting mirror of the optical resonator and the influence of impurities contained in the laser medium gas. FIG. 6 shows an example in which the relationship between the delay times is Td3 <Td1 <Td2.

  In step S3, delay times Td1, Td2, and Td3 from when the laser oscillation stop trigger is given until the laser pulse rises are measured. Specifically, the control device 20 measures the elapsed time from when the laser oscillation start trigger is given to the laser light source 1 until the detection signal is received from the photodetector 22.

  In step S4, it is determined whether or not the delay time Td is within the standard. If the delay time Td is outside the standard, a laser oscillation stop trigger is given to the laser light source 1 in step S8. Thereby, supply of the electric power to the discharge electrode 41 (FIG. 1) is stopped. Abnormal oscillation can be prevented by stopping the supply of power.

  When the delay time Td is within the standard, in step S5, times t13, t23, and t33 (FIG. 6) for giving a laser oscillation stop trigger to the laser light source 1 with reference to the rising times t12, t22, and t32 (FIG. 6) of the laser pulse. 6) is calculated. Specifically, the times when the time corresponding to the target pulse width Pd has elapsed from the rising times t12, t22, and t32 of the laser pulse are set as times t13, t23, and t33 that give a laser oscillation stop trigger. The target pulse width Pd is stored in the control device 20 in advance.

  In step S6, a laser oscillation stop trigger is given to the laser light source 1 at times t13, t23, and t33 (FIG. 6) calculated in step S5. As a result, the laser pulses Lp1, Lp2, and Lp3 fall.

  In step S7 (FIG. 5), it is determined whether or not the processing is finished. When an unprocessed processing point remains, the beam scanner 18 is controlled so that the laser pulse is incident on the processing point to be processed next, and the process returns to step S1. When the processing of all the processing points is completed, the laser processing is finished.

  In the example shown in FIG. 6, when the timing control is performed so that the trigger time widths Te1, Te2, Te3 are the same, the pulse width from the rising time to the falling time of the laser pulse becomes the delay time Td1, Td2, It varies due to the influence of variation in Td3.

In the above embodiment, the times t13, t23, and t33 (FIG. 6) at which the laser oscillation stop trigger is given to the laser light source 1 are determined with reference to the rising times t12, t22, and t32 (FIG. 6) of the laser pulse. Therefore, the pulse width Pd of the laser pulse is not affected by variations in the delay times Td1, Td2, and Td3. Therefore, even if the delay times Td1, Td2, and Td3 vary, the pulse width Pd can be made constant. As a result, variations in pulse energy are reduced. If the elapsed time from the time t12 , t22, t32 of the rise of the laser pulse to the time t13, t23, t33 giving the laser oscillation stop trigger is made constant, the pulse energy can be made substantially uniform.

  Since the pulse width Pd is stored in advance in the control device 20 (FIG. 1), it is not necessary to perform an operation for determining a target pulse width after detecting the rising edge of the laser pulse. Based on the measurement result after the rise of the laser pulse, the method for performing the calculation for determining the pulse width of the laser pulse can be applied to laser processing using a laser pulse having a pulse width shorter than the calculation time. Can not. In the above embodiment, since it is not necessary to perform an operation for determining the pulse width, the pulse width Pd is not restricted by the operation time. In the above embodiment, it is not necessary to measure the light energy after the rise of the laser pulse, and it is only necessary to detect the presence or absence of the laser pulse. For this reason, it is not necessary to ensure the measurement time for performing a highly accurate optical energy measurement. For the above-described reasons, the above embodiment can be applied to laser processing with a short pulse width Pd, for example, laser processing with a pulse width shorter than several tens of μs.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 1 Laser light source 10 Laser oscillator 11 Drive circuit 12 Spot position stabilization optical system 13 Aspherical lens 14 Collimating lens 15 Mask 16 Field lens 17 Folding mirror 18 Beam scanner 19 f (theta) lens 20 Control apparatus 21 Partial reflector 22 Optical detector 25 Stage 30 Work object 40 Blower 41 Discharge electrode 42 Discharge space 43 Conductive member 44 Ceramic member 46 Heat exchanger 50 Chamber 51 Terminal 52 Current path in chamber 55 Current path outside chamber

Claims (3)

A laser light source that starts laser oscillation in synchronization with a laser oscillation start trigger received from outside, and stops laser oscillation in synchronization with a laser oscillation stop trigger;
A photodetector for detecting a laser pulse emitted from the laser light source;
The laser oscillation start trigger is given to the laser light source, and the time to give the laser oscillation stop trigger to the laser light source is determined based on the detection time of the laser pulse by the photodetector, and the laser is determined at the determined time. A laser processing apparatus having a control device for giving an oscillation stop trigger to the laser light source;   The control device stores a target pulse width of a laser pulse to be emitted, and when the time equal to the target pulse width has elapsed from the detection time of the laser pulse by the photodetector, the laser light source The laser processing apparatus according to claim 1, wherein a laser oscillation stop trigger is provided. In synchronization with the laser oscillation start trigger received from the controller starts laser oscillation, the laser light source to stop the laser oscillation in synchronization with the laser oscillation stop trigger, the steps of the control device gives the laser oscillation start trigger,
A step in which a photodetector detects a laser pulse emitted from the laser light source, and the control device detects a rising time of the laser pulse based on a detection result of the photodetector ;
A step of providing the laser light source with the laser oscillation stop trigger by the control device at a time when a time corresponding to a preset target pulse width has elapsed from a rise time of the laser pulse.

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