TWI577482B - Laser processing device and laser processing method - Google Patents

Description

Laser processing device and laser processing method

The present invention relates to a laser processing apparatus and a laser processing method for performing laser processing by sequentially injecting a pulsed laser beam onto a plurality of processed points defined on a surface of a workpiece.

Patent Document 1 listed below discloses a technique of performing hole drilling on a wiring substrate using a pulsed laser beam. In the method disclosed in Patent Document 1, when a laser pulse having a pulse energy smaller than an allowable value is incident on a wiring board, an insufficient amount of pulse energy can be compensated by injecting an additional laser pulse into the portion.

In the method disclosed in Patent Document 2 below, the energy of the rising portion of the laser pulse is detected. When the detection result is within the allowable range, the subsequent portion of the laser pulse is incident on the object to be processed. If the detection result is out of the allowable range, the laser pulse is not incident on the object to be processed. Thereby, it is possible to prevent a defective laser pulse having insufficient energy or excessive energy from entering the object to be processed.

(previous technical literature) (Patent Literature)

Patent Document 1: Japanese Patent No. 2858236

Patent Document 2: Japanese Laid-Open Patent Publication No. 2009-148812

In order to accurately determine the allowable range of the pulse energy of the laser pulse or the allowable range of the energy of the rising portion of the laser pulse, various evaluation tests are required with different pulse energies. The allowable range of pulse energy can also be determined according to the deviation of the pulse energy when the laser light source is normally operated. This method makes it easy to determine the allowable range.

The pulse energy depends on the repetition frequency of the pulse (hereinafter referred to as "frequency"). Therefore, if the frequency at the time of laser processing varies, the variation in pulse energy becomes large. If the deviation of the pulse energy becomes large, even if the laser light source operates normally, the pulse energy may exceed the allowable range determined initially. If the laser pulse is judged to be good or bad based on the allowable range determined initially, the laser pulse output during normal operation may be judged to be defective.

An object of the present invention is to provide a laser processing apparatus and a laser processing method capable of accurately determining the goodness and the poorness of a laser pulse even if the frequency fluctuates.

According to an aspect of the present invention, a laser processing apparatus is provided having: a laser light source outputting a pulsed laser beam; a stage that holds the object to be processed, and a beam scanner that causes the pulsed laser beam outputted from the laser light source to be incident on the object to be processed, and moves an incident position on a surface of the object to be processed; a photodetector, Detecting a physical quantity of each of the laser pulses of the pulsed laser beam outputted from the laser light source, which is dependent on the pulse energy; and a path switch, the path of the pulsed laser beam outputted from the laser light source is incident on the processing The first path of the object is switched between the first path and the second path not incident on the object to be processed, and the control device stores the position and processing order of the plurality of processed points on the surface of the object to be processed, and is processed according to the foregoing. Controlling the beam scanner and the path switch by the position of the dot, the processing sequence, and the detection result of the photodetector, the control device executing a pre-processing preparation process, and controlling the beam scanner in the pre-processing preparation process to Having the aforementioned pulsed laser beam incident on the position of the processed point according to the processing order, The photodetector detects the physical quantity of each laser pulse depending on the pulse energy, and determines an allowable range of the physical quantity according to the distribution of the physical quantity. After the pre-processing preparation process, the control device is in the processing object. And transmitting at least a portion of the laser pulse whose physical quantity is detected within the allowable range by the photodetector along the first path, and transmitting the lightning beyond the allowable range along the second path along the first path Shoot the pulse.

According to another aspect of the present invention, there is provided a laser processing method having a process of controlling a beam scanner to cause a pulsed laser beam to be incident on a predetermined point to be processed in a predetermined processing order while measuring each of the mines a process in which a pulse pulse is dependent on a physical quantity of pulse energy; a process for determining an allowable range of the physical quantity based on the measured distribution of the physical quantity; and the aforementioned processing of causing the pulsed laser beam to be incident on the object to be processed according to the processing order The position of the point and the laser processing process, in the foregoing laser processing process, measuring the physical quantity of each laser pulse of the pulsed laser beam, and the laser pulse is obtained when the measurement result is within the allowable range At least a part of the object is incident on the object to be processed, and when the measurement result exceeds the allowable range, the laser pulse is not incident on the object to be processed.

Since the pulsed laser beam is actually output while controlling the beam scanner, and the physical quantity depending on the pulse energy is measured, the deviation of the pulse energy due to the deviation of the frequency of the pulsed laser beam during processing is reflected in the allowable range. Decided. Therefore, it is possible to accurately determine the goodness and the poorness of the laser pulse.

10‧‧‧Laser light source

11‧‧‧Optical optical system

13‧‧‧ aperture

15‧‧‧Path Switcher

16‧‧‧Processing path

17‧‧‧Damper path

18‧‧‧Return mirror

20‧‧‧beam scanner

21‧‧‧ Objective lens

23‧‧‧stage

24‧‧‧Mobile agencies

30‧‧‧Partial mirror

31‧‧‧ Beam damper

32‧‧‧Photodetector

40‧‧‧Processing objects

41‧‧‧Processed points

50‧‧‧Control device

51‧‧‧Storage device

Lp1, Lp2, Lp3‧‧‧ laser pulses

Con‧‧‧ control signal

Det‧‧‧detection signal

Trg‧‧‧trigger signal

R0‧‧‧Normal range

R1‧‧‧allowable range

Fig. 1 is a schematic view showing a laser processing apparatus of an embodiment.

Figure 2 shows the trigger signal trg, the laser pulse Lp1 incident on the path switcher, the laser pulse Lp2 transmitted on the processing path, the laser pulse Lp3 transmitted on the damper path, the control signal con of the control path switcher, And a timing chart of the detection signal det transmitted from the photodetector to the control device, and a graph of an example of the waveform.

Fig. 3A is a timing chart when a laser pulse is outputted from a laser light source at a constant frequency, and Fig. 3B is a histogram of the determination energy when a laser pulse is output at a constant frequency.

Fig. 4A is a schematic plan view of the object to be processed, Fig. 4B is a timing chart of laser pulses during processing, and Fig. 4C is a histogram of determination energy of laser pulses during processing.

Figure 5 is a flow chart of a laser processing method of an embodiment.

Fig. 6A is a timing chart of the laser pulse outputted from the laser light source in step S1, and Fig. 6B is a histogram of the determination energy of the laser pulse outputted at the timing shown in Fig. 6A.

Fig. 7 is a graph showing the correspondence relationship between the arrangement pattern of the processed points and the allowable range.

Fig. 1 is a schematic view of a laser processing apparatus according to an embodiment. The laser processing apparatus of the embodiment is, for example, a laser drilled hole for drilling a wiring board. The laser light source 10 outputs a pulsed laser beam by receiving a trigger signal trg from the control device 50. The laser light source 10 uses, for example, a carbon dioxide laser.

The pulsed laser beam output from the laser light source 10 is incident on the illumination optical system 11. The illumination optical system 11 changes at least one of the diffusion angle and the beam diameter of the pulsed laser beam. The pulsed laser beam transmitted through the illumination optical system 11 is incident on the aperture 13. The illumination optical system 11 also has a function of uniformizing the beam distribution at the position of the aperture 13. The aperture 13 shapes the beam section.

The pulsed laser beam transmitted through the aperture 13 is incident on the path switch 15. The path switcher 15 switches the path of the pulsed laser beam between the processing path 16 and the damper path 17 by receiving the control signal con from the control device 50. The path switcher 15 uses, for example, an Acousto-Optic Deflector (AOD). The path in which the input laser pulse Lp1 advances linearly corresponds to the damper path 17, and the path of the laser pulse diffraction corresponds to the processing path 16.

The laser pulse Lp2 transmitted along the processing path 16 is deflected by the folding mirror 18 and incident on the beam scanner 20. The beam scanner 20 is controlled by the control device 50 to change the direction of travel of the pulsed laser beam into a two-dimensional direction. The beam scanner 20 uses, for example, a pair of current scanners.

The pulsed laser beam that has passed through the beam scanner 20 passes through the objective lens 21 and enters the object 40. The objective lens 21 uses, for example, an f θ lens. The object 40 to be processed is, for example, a wiring board to be subjected to drilling. The object 40 is held on the stage 23 . The stage 23 is moved in a two-dimensional direction parallel to the surface of the object 40 by the moving mechanism 24. The moving mechanism 24 is controlled by the control device 50.

By the objective lens 21, the opening of the aperture 13 is reduced and projected onto the object to be processed. The surface of the object 40. The direction in which the pulsed laser beam travels is changed by the beam scanner 20, whereby the incident position of the pulsed laser beam can be moved on the surface of the object 40.

The laser pulse Lp3 transmitted along the damper path 17 is incident on the partial mirror 30. The laser pulse transmitted through the partial mirror 30 is incident on the beam damper 31. The laser pulse reflected by the partial mirror 30 is incident on the photodetector 32. The photodetector 32 uses, for example, an energy meter having sensitivity to a wavelength region of a pulsed laser beam output from the laser light source 10. The detection signal det based on the photodetector 32 is input to the control device 50.

The control device 50 includes a storage device 51. The storage device 51 stores position information, processing order, and various information required for control of a plurality of processed points of the object 40 to be processed.

The second diagram shows the trigger signal trg, the laser pulse Lp1 incident on the path switch 15, the laser pulse Lp2 transmitted on the processing path 16, the laser pulse Lp3 transmitted on the damper path 17, and the control path switcher 15. An example of a timing chart and a waveform of the control signal con and the detection signal det transmitted from the photodetector 32 to the control device 50.

At time t1, if the trigger signal trg rises, the laser pulse Lp1 rises later at time t2. At this moment, the output path of the path switcher 15 is switched to the damper path 17. Therefore, the laser pulse Lp3 transmitted on the damper path 17 rises.

The photodetector 32 detects the laser pulse Lp3 and transmits the detection signal det to the control device 50. The size of the detection signal det is approximately proportional to the power of the laser pulse Lp3. The control device 50 passes through one from the rising time t2 The detection signal det is integrated at time t3 after the fixed time. The integration result is stored in the storage device 51.

At time t4, the control device 50 transmits a control signal con switched to the processing path 16 to the path switcher 15. The output path of the path switcher 15 is switched by the damper path 17 to the machining path 16, whereby the laser pulse Lp3 is lowered and the laser pulse Lp2 is raised. Since the laser pulse Lp3 falls, the detection signal det of the photodetector 32 also becomes zero.

At time t5, the control device 50 transmits a control signal con switched to the damper path 17 to the path switcher 15. The output path of the path switcher 15 is switched by the machining path 16 to the damper path 17, whereby the laser pulse Lp3 rises and the laser pulse Lp2 falls. As the laser pulse Lp3 rises, the detection signal det of the photodetector 32 also rises.

At time t6, the trigger signal trg drops. Thereby, the laser pulse Lp1 and the laser pulse Lp3 are lowered. As the laser pulse Lp3 falls, the detection signal det of the photodetector 32 also drops.

The value obtained by integrating the detection signal det of the photodetector 32 from time t2 to t3 (the area of the hatched portion in Fig. 2) corresponds to the energy of the rising portion of the laser pulse Lp1. If the pulse width of the laser pulse Lp2 cut out from the laser pulse Lp1 is constant for processing, the pulse energy of the laser pulse Lp2 is correlated with the energy of the rising portion of the laser pulse Lp1. Therefore, it is possible to determine whether or not the pulse energy of the laser pulse Lp2 is normal by the energy of the rising portion of the laser pulse Lp1. The energy of the rising portion of the laser pulse Lp1 is referred to as "determination energy". The energy is determined to be a physical quantity that depends on the pulse energy.

The time from the time t2 to the time t3 is determined in accordance with the average rise time of the laser pulse Lp1. As the time from the time t2 to the time t3, the average time until the power of the laser pulse Lp1 reaches the steady state can be used, and the average time until the power of the laser pulse Lp2 reaches 90% of the steady state power can be used.

As the physical quantity depending on the pulse energy, the power of the rising portion of the laser pulse Lp1 may be used instead of the energy of the rising portion. In the rising portion, the power of only one point on the time axis is used as the physical quantity depending on the pulse energy, and the reliability of the pulse energy estimated from the power is lowered. By using the power of a plurality of parts on the time axis as the physical quantity depending on the pulse energy in the rising portion, the reliability of the pulse energy estimated from the power can be improved.

A timing chart when the laser light 10 outputs the laser pulse Lp1 at a constant frequency from the laser light source 10 is shown in Fig. 3A.

Fig. 3B shows a histogram of the determination energy when the laser pulse Lp1 is output at a constant frequency. The horizontal axis represents the determination energy, and the vertical axis represents the number of times. When the laser light source 10 operates normally, it is determined that the distribution of energy is substantially in accordance with the normal distribution. If m is used to represent the average value of the determination energy, and σ is the standard deviation, the determination energy of the vast majority of the laser pulse Lp1 is in the range of m ± 3σ (hereinafter referred to as the normal range R0).

4A is a schematic plan view of the object 40 to be processed. A plurality of processed points 41 are defined on the surface of the object 40. The hole drilling process is performed by causing the laser pulse Lp2 (Fig. 1) to be incident on the workpiece 41. The processing order of the processed points 41 is determined in advance. In Figure 4A, with arrows An example of the processing sequence is shown. As shown in FIG. 4A, the distance from the processed workpiece 41 to the workpiece 41 to be processed next time is not constant, but varies. If the moving distance of the incident position of the pulsed laser beam becomes long, the adjustment time of the beam scanner 20 also becomes long. Therefore, during the processing of the object 40, the frequency of the pulsed laser beam is not constant, but varies depending on the moving distance of the incident position of the pulsed laser beam.

An example of a timing chart of the pulsed laser beam output from the laser light source 10 during the processing period is shown in Fig. 4B. As shown in Fig. 4B, the frequency of the pulsed laser beam is deviated.

Fig. 4C is a histogram of the determination energy when the frequency of the pulsed laser beam is deviated. For convenience of comparison, a histogram of the determination energy when the frequency of the pulsed laser beam is constant is indicated by a broken line. Generally, the pulse energy of the pulsed laser beam output from the laser source 10 is frequency dependent. For example, in a carbon dioxide laser, if the frequency becomes high, there is a tendency for the pulse energy to decrease.

The deviation of the determination energy when the frequency is deviated is superimposed on the variation of the determination energy due to the deviation of the frequency when the frequency is constant. Therefore, if the frequency is deviated, it is determined that the deviation of the energy is increased. When the frequency is not constant, even if the laser light source 10 operates normally, it may occur that the determination energy exceeds the normal range R0.

When a laser pulse in which only the determination energy is within the normal range R0 is used for the control of the laser processing, even if the laser light source 10 operates normally, a laser pulse having a determination energy exceeding the normal range R0 is not used. plus work. Therefore, the utilization efficiency of the laser energy is lowered. In the embodiment described below, it is possible to suppress a decrease in the utilization efficiency of the laser energy due to the variation in the determination energy under the condition that the laser light source 10 is normally operated.

Fig. 5 is a flow chart of the laser processing method of the embodiment. In step S1, the laser light source 10 and the beam scanner 20 are controlled in accordance with the position of the processed object 41 (Fig. 4A) of the object 40 and the processing order, thereby outputting the pulsed laser beam from the laser light source 10. At this time, the path switcher 15 maintains the state in which the output path is switched to the damper path 17. Therefore, no pulsed laser beam is incident on the stage 23. However, since the beam scanner 20 is controlled, the frequency of the pulsed laser beam reflects the deviation of the adjustment time of the beam scanner 20.

Fig. 6A is a timing chart of the laser pulse Lp1 output from the laser light source 10 in step S1. The frequency of the pulsed laser beam in step S1 is deviated in the same manner as the frequency of the pulsed laser beam in the processing period shown in Fig. 4B. The beam scanner 20 is controlled in accordance with the position and processing order of the actual workpiece 41, so that the degree of deviation of the frequency of the pulsed laser beam in step S1 is the same as the degree of deviation of the frequency of the pulsed laser beam during processing.

The detection result of the photodetector 32 is input to the control device 50. The control device 50 obtains the determination energy of each of the laser pulses Lp1, and stores the obtained determination energy in the storage device 51.

In step S2, the allowable range R1 of the determination energy is determined in accordance with the distribution of the determination energy.

Refer to Figure 6B for the determination method of the allowable range R1 of the determination energy. Be explained. Figure 6B is a histogram of the determination energy. For convenience of comparison, the distribution of the determination energy when the frequency of the pulsed laser beam is constant is indicated by a broken line. The average value of the distribution of the determination energy obtained in step S1 is represented by m1, and σ1 represents the standard deviation. As an example, the upper limit of the allowable range R1 is m1 + 3σ1, and the lower limit is m1-3σ1. The allowable range R1 when the frequency is deviated becomes wider depending on the deviation width of the determination energy than the normal range R0 when the frequency is constant.

In step S3 (fifth diagram), the object 40 is placed on the stage 23 (Fig. 1). In step S4, the beam scanner 20 is operated and waits until the beam scanner 20 of the pulsed laser beam is stabilized. After the beam scanner 20 is stabilized, one laser pulse Lp1 is output from the laser light source 10 in step S5. At the start of the output of the laser pulse Lp1, the output path of the path switch 15 is switched to the damper path 17. Therefore, the detection signal det based on the light intensity of the photodetector 32 is input to the control device 50. The control device 50 calculates the determination energy based on the detection signal det input from the photodetector 32.

In step S6, it is determined whether or not the determination energy is within the allowable range R1. When it is determined that the energy exceeds the allowable range R1, the laser pulse Lp1 falls, and the process returns to step S5, and the next laser pulse Lp1 is output. When it is determined that the energy is within the allowable range R1, in step S7, the laser beam Lp2 (second drawing) is cut out from the laser pulse Lp1 by the control path switch 15, and transmitted along the processing path 16. The laser pulse Lp2 is incident on the object 40 and is subjected to drilling.

In step S8, it is determined whether or not all of the processed points 41 have been processed. End. When the unprocessed workpiece 41 is left, the process returns to step S4, and the processing of the next processed point 41 is performed. When a plurality of laser pulses are incident on each of the processed points 41 for processing, cyclic mode processing or trigger mode processing can be applied.

In the cyclic mode processing, when one laser pulse is incident on each of the pair of processed points 41, the incident position is moved to the next processed point 41. The order in which one laser pulse is incident on all of the processed points 41 is taken as one cycle, and by repeating the cycle several times, the laser pulse of the desired number of times of emission can be incident on the processed point 41. When the loop mode processing is performed, when the loop of the desired number of times is repeated in step S8, it is determined that the machining is completed.

In the trigger mode processing, after one laser beam having a desired number of shots is continuously incident on one of the processed points 41, the processing of the processed point 41 to be processed next is performed. When the trigger mode processing is performed, when the last laser pulse and the next laser pulse are incident on the same processed point 41, it is not necessary to operate the beam scanner 20 in step S4.

When the machining of all the machining points 41 is completed, it is determined in step S9 whether or not the unprocessed machining object 40 having the same arrangement pattern of the machining points 41 is left. When the unprocessed object 40 is left, the process returns to step S3, and the object 40 to be processed next time is placed on the stage 23. When there is no unprocessed object 40, the processing is terminated.

When the object 40 having the arrangement pattern different from the arrangement pattern of the workpiece 41 to be processed of the object 40 to be processed is processed, the pre-processing preparation process of steps S1 to S2 is executed, and the permission is again determined. Range R1.

In the above embodiment, even in the case of the laser pulse Lp1 having the determination energy exceeding the normal range R0 shown in Fig. 6B, the laser pulse having the energy within the allowable range R1 can be used for processing. Therefore, it is possible to suppress a decrease in the utilization efficiency of the laser energy. Further, when the operation of the laser light source 10 becomes unstable and the determination energy exceeds the allowable range R1, the laser pulse Lp1 cannot be used for processing. Therefore, it is possible to prevent a decrease in processing quality due to insufficient pulse energy or excessive incident laser pulse Lp2.

In the above-described embodiment, before the processing of the plurality of processing objects 40 having the same arrangement pattern of the machining points 41, the pre-machining process of steps S1 to S2 (Fig. 5) is performed, and the allowable range R1 is determined. A correspondence relationship between the determined allowable range R1 and the arrangement pattern of the processed point 41 may be stored in the storage device 51.

An example of this correspondence is shown in Fig. 7. The lower limit value and the upper limit value of the allowable range R1 are stored in accordance with the arrangement pattern of each of the processed points 41. When the arrangement pattern of the workpieces 41 to be processed 40 to be processed next time is stored in the correspondence table of Fig. 7, steps S1 to S2 (second diagram) can be omitted. In step S6, it is only necessary to determine whether or not the determination energy stored in the storage device 51 is within the allowable range R1.

The present invention has been described by the above embodiments, but the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various changes, modifications, combinations and the like can be made.

Claims (7)

A laser processing apparatus characterized by comprising: a laser light source outputting a pulsed laser beam; a stage holding the object to be processed; and a beam scanner for causing the pulsed laser beam outputted from the laser source to be incident on the foregoing Processing an object and moving an incident position on a surface of the object to be processed; and a photodetector detecting a physical quantity of each of the laser pulses of the pulsed laser beam outputted from the laser light source depending on pulse energy; the path switcher And switching a path of the pulsed laser beam output from the laser light source between a first path incident on the object to be processed and a second path not incident on the object to be processed; and a control device storing the foregoing Controlling the position and processing order of the plurality of processed points on the surface of the object, and controlling the beam scanner and the path switch according to the position of the processed point, the processing order, and the detection result of the photodetector, the control The device performs a pre-processing preparation process, and controls the aforementioned beam scanner in the aforementioned pre-processing preparation process so that The pulsed laser beam is incident on the position of the processed point according to the processing sequence, and the aforementioned physical quantity of each laser pulse dependent on the pulse energy is detected by the photodetector, and the physical quantity is determined according to the distribution of the physical quantity. The allowable range, after the pre-processing preparation process, the control device transmits the light along the first path during the processing of the object to be processed The detector detects at least a portion of the laser pulse having the physical quantity within the allowable range, and transmits a laser pulse that exceeds the allowable range along the second path. The laser processing apparatus according to claim 1, wherein the control device determines an upper limit value and a lower limit value of the allowable range based on a standard deviation of the physical quantity. The laser processing apparatus according to the first or second aspect of the invention, wherein the control device is arranged at a processing point of a workpiece to be processed next time and a processed point of the workpiece to be processed last time. When the arrangement pattern is different, the pre-processing preparation process is executed and the allowable range is newly determined before the processing of the object to be processed next. The laser processing apparatus according to claim 1 or 2, wherein the physical quantity is energy of a rising portion of the laser pulse. A laser processing method characterized by having the following process: controlling a beam scanner to cause a pulsed laser beam to be incident on a predetermined processed point in accordance with a predetermined processing order, while measuring pulse-dependent energy of each laser pulse a process for determining a physical quantity; a process for determining an allowable range of the physical quantity based on the measured distribution of the physical quantity; and causing the pulsed laser beam to be incident on the object to be processed according to the processing order The position of the processed point above and the laser processing process, in the laser processing process described above, measuring the physical quantity of each laser pulse of the pulsed laser beam, and the measurement result is within the allowable range At least a part of the laser pulse is incident on the object to be processed, and when the measurement result exceeds the allowable range, the laser pulse is not incident on the object to be processed. The laser processing method according to claim 5, wherein the upper limit and the lower limit of the allowable range are determined based on a standard deviation of the physical quantity. The laser processing method according to claim 5, wherein the physical quantity is energy of a rising portion of the laser pulse.