KR20150112814A - Laser processing apparatus and laser processing method - Google Patents

Abstract

A laser processing apparatus capable of appropriately determining whether a laser pulse is good or bad even when a frequency is changed is provided. A beam injector injects a pulse laser beam to a processing object and moves an injection movement on a surface. An optical detector measures physical parameters depending on the pulse energy of each laser pulse. A path switch switches the path of a pulse laser beam between the first path of injection to the processing object and a second path of no injection to the processing object. A control device measures physical parameters depending on pulse energy while controlling the beam injector to inject a pulse laser beam to a position of a processing target point on the basis of processing sequence, and determines an allowable range of the physical parameters on the basis of distribution of the physical parameters. During processing, at least a part of the laser pulse in which the physical parameters measured by the optical detector fall within the allowable range is allowed to propagate along the first path, and a laser pulse deviating from the allowable range is allowed to propagate along the second path.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a laser processing apparatus and a laser processing method,

The present application claims priority based on Japanese Patent Application No. 2014-064974 filed on March 27, 2014. The entire contents of which are incorporated herein by reference.

The present invention relates to a laser machining apparatus and a laser machining method for performing laser machining by sequentially applying a pulsed laser beam to a plurality of machining points defined on the surface of an object to be machined.

A technique for punching a printed substrate using a pulsed laser beam is disclosed in Patent Document 1 below. 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 printed circuit board, an additional laser pulse is incident on the portion, thereby compensating for the shortage of pulse energy.

In the method disclosed in the following Patent Document 2, the energy of the rising portion of the laser pulse is detected. If the detection result is within the permissible range, the succeeding portion of the laser pulse is made incident on the object to be machined. When the detection result is out of the permissible range, the laser pulse is not incident on the object to be processed. This makes it possible to prevent a deficient laser pulse of energy shortage or energy from being incident on the object to be processed.

Japanese Patent Publication No. 2858236 JP-A-2009-148812

Various evaluation experiments must be performed with different pulse energies in order to appropriately determine the allowable range of the pulse energy of the laser pulse and the allowable range of the energy of the rising portion of the laser pulse. It is also possible to determine the permissible range of the pulse energy based on the non-uniformity of the pulse energy when the laser light source is normally operating. With this method, the allowable range can be easily determined.

The pulse energy depends on the repetition frequency of the pulse (hereinafter simply referred to as "frequency"). As a result, if the frequency at the time of laser processing is nonuniform, the nonuniformity of the pulse energy becomes large. If the nonuniformity of the pulse energy is large, the pulse energy may deviate from the initially determined allowable range even if the laser light source operates normally. Judging whether the laser pulse is good or bad based on the initially determined allowable range, the laser pulse output during normal operation may be judged to be defective.

An object of the present invention is to provide a laser machining apparatus and a laser machining method capable of appropriately determining a good or bad laser pulse even when the frequency varies.

According to one aspect of the present invention,

A laser light source for outputting a pulsed laser beam,

A stage for supporting an object to be processed,

A beam syringe for causing the pulsed laser beam outputted from the laser light source to enter the object to be processed and moving the incident position on the surface of the object,

A photodetector for measuring a physical quantity depending on pulse energy of each laser pulse of the pulse laser beam output from the laser light source;

A path switching unit for switching the path of the pulse laser beam output from the laser light source between a first path for entering the object to be processed and a second path for not entering the object to be processed,

Wherein the position of the plurality of processing points on the surface of the object to be processed and the machining order are memorized and based on the position of the machining point, the machining order, and the detection result of the photodetector, Control device for controlling the switching device

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The control device includes:

The beam detector is controlled so that the pulse laser beam is incident on the position of the processing point based on the machining order, and the physical quantity depending on each pulse energy of the laser pulse is measured by the optical detector, Executes a preprocess preparation procedure for determining an allowable range of the physical quantity based on the distribution,

Wherein the physical quantity measured by the photodetector propagates at least a part of the laser pulse falling within the allowable range along the first path during the machining of the object after the preprocessing preparation procedure, The laser processing apparatus is provided for causing an outgoing laser pulse to propagate along the second path.

According to another aspect of the present invention,

A step of measuring a physical quantity depending on pulse energy of each laser pulse while controlling the beam syringe so that the pulsed laser beam is incident on a predetermined processing position at a predetermined processing order;

Determining a permissible range of the physical quantity based on the measured distribution of the physical quantity;

A step of irradiating a pulse laser beam to the position of the work point on the object to be processed in the machining order to perform laser machining

To have,

In the step of performing the laser processing, the physical quantity of each laser pulse of the pulse laser beam is measured. When the measurement result falls within the allowable range, at least a part of the laser pulse is incident on the object, And when the measurement result is out of the allowable range, the laser pulse is not incident on the object to be processed.

The pulse laser beam is actually outputted while controlling the beam syringe to measure the physical quantity depending on the pulse energy. Therefore, the non-uniformity of the pulse energy due to the non-uniformity of the frequency of the pulsed laser beam at the time of processing is reflected in the determination of the allowable range. This makes it possible to appropriately judge whether the laser pulse is good or bad.

1 is a schematic view of a laser machining apparatus according to an embodiment.
Fig. 2 is a schematic diagram showing the configuration of the laser control apparatus according to the first embodiment of the present invention. The laser pulse Lp1 is a laser pulse Lp1 which propagates through a machining path, a laser pulse Lp3 which propagates a damper path, (con), and a detection chart (det) transmitted from the photodetector to the control apparatus.
In Fig. 3, Fig. 3A is a timing chart when laser pulses are output from a laser light source at a constant frequency, and Fig. 3B is a histogram of judgment energy when laser pulses are 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 judgment energy of laser pulses during processing.
5 is a flowchart of a laser machining method according to the embodiment.
6A is a timing chart of laser pulses output from the laser light source in step S1, and FIG. 6B is a histogram of determination energy of laser pulses output at the timing shown in FIG. 6A.
7 is a chart showing the correspondence relationship between the arrangement pattern of the machining points and the allowable range.

Fig. 1 shows a schematic view of a laser machining apparatus according to an embodiment. The laser machining apparatus according to the embodiment is, for example, a laser drill for punching a printed substrate. The laser light source 10 outputs the pulse laser beam by receiving the trigger signal trg from the control device 50. [ For the laser light source 10, for example, a carbon dioxide gas laser is used.

The pulse laser beam output from the laser light source 10 is incident on the irradiation optical system 11. [ The irradiation optical system 11 changes at least one of the diffusing angle and the beam diameter of the pulse laser beam. The pulse laser beam transmitted through the irradiation optical system 11 is incident on the aperture 13. The irradiation optical system 11 also has a function of making the beam profile at the position of the aperture 13 uniform. The aperture 13 shapes the beam cross-section.

The pulse laser beam transmitted through the aperture 13 is incident on the path switcher 15. [ The path switcher 15 switches the path of the pulsed laser beam between the machining path 16 and the damper path 17 by receiving the control signal con from the control device 50. [ As the path switcher 15, for example, an acousto-optic device (AOD) is used. The path through which the input laser pulse Lp1 goes straight corresponds to the damper path 17 and the path through which the laser pulse is diffracted corresponds to the machining path 16. [

The laser pulse Lp2 propagating along the processing path 16 is deflected by the fold mirror 18 and enters the beam syringe 20. [ The beam syringe 20 is controlled by the control device 50 to change the traveling direction of the pulsed laser beam to the two-dimensional direction. For the beam syringe 20, for example, a pair of galvano scanners are used.

The pulse laser beam having passed through the beam syringe 20 is transmitted through the objective lens 21 and is incident on the object to be processed 40. For the objective lens 21, for example, an f? Lens is used. The object to be processed 40 is, for example, a printed substrate to be subjected to punching processing. The object to be processed 40 is supported on a stage 23. The stage 23 is moved in the 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.

The aperture of the aperture 13 is reduced and projected onto the surface of the object 40 by the objective lens 21. The incident position of the pulsed laser beam can be moved on the surface of the object 40 by changing the traveling direction of the pulsed laser beam by the beam syringe 20. [

The laser pulse Lp3 propagating along the damper path 17 is incident on the partial reflection mirror 30. The laser pulse transmitted through the partial reflection mirror 30 is incident on the beam damper 31. The laser pulse reflected by the partial reflection mirror 30 is incident on the photodetector 32. An energy meter having sensitivity to the wavelength range of the pulsed laser beam output from the laser light source 10 is used as the photodetector 32, for example. The detection signal det detected by the photodetector 32 is input to the control device 50. [

The control device (50) includes a storage device (51). The storage device 51 stores positional information of a plurality of processing points of the object 40, processing order, and various information necessary for control.

A laser pulse Lp1 that propagates through the machining path 16; a laser pulse Lp3 that propagates through the damper path 17; A timing chart and waveforms of a control signal con for controlling the path switching unit 15 and a detection signal det transmitted from the photodetector 32 to the control device 50 are shown.

At time t1, when the trigger signal trg rises, the laser pulse Lp1 rises slightly at time t2. At this point of time, the output path of the path switching unit 15 is switched to the damper path 17. As a result, the laser pulse Lp3 propagating through 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 magnitude of the detection signal det is approximately proportional to the power of the laser pulse Lp3. The control device 50 integrates the detection signal "det" from the rising time t2 to a time t3 when a predetermined time has elapsed. The integration result is stored in the storage device 51.

At time t4, the control device 50 transmits the control signal con to be switched to the machining path 16 to the path switching device 15. [ The output path of the path switcher 15 is switched from the damper path 17 to the machining path 16 so that the laser pulse Lp3 falls and the laser pulse Lp2 rises. As the laser pulse Lp3 falls, the detection signal det of the photodetector 32 also becomes zero.

At time t5, the control device 50 transmits the control signal con to switch to the damper path 17 to the path switching device 15. [ The output path of the path switcher 15 is switched from the machining path 16 to the damper path 17 so that 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 falls. As a result, the laser pulse Lp1 and the laser pulse Lp3 fall. As the laser pulse Lp3 falls, the detection signal det of the photodetector 32 also falls.

The value obtained by integrating the detection signal det of the photodetector 32 from the time t2 to the time t3 (the area of the hatched portion in Fig. 2) corresponds to the energy of the rising portion of the laser pulse Lp1. The pulse energy of the laser pulse Lp2 and the energy of the rising portion of the laser pulse Lp1 have a correlation when the pulse width of the laser pulse Lp2 cut out from the laser pulse Lp1 for processing is constant. Therefore, the steady state of the pulse energy of the laser pulse Lp2 can be determined by the energy of the rising portion of the laser pulse Lp1. The energy of the rising portion of the laser pulse Lp1 is assumed to be "determination energy ". The determination energy is a physical quantity that depends on the pulse energy.

The time from time t2 to time t3 is determined based on the average rise time of the laser pulse Lp1. The average time until the power of the laser pulse Lp1 reaches the steady state may be employed as the time from the time t2 to the time t3 and the power of the laser pulse Lp2 may reach 90% May be employed.

As the physical quantity depending on the pulse energy, the power of the rising portion of the laser pulse Lp1 may be employed instead of the energy of the rising portion. If only one point of power on the time axis among the rising portions is employed as a physical quantity depending on the pulse energy, the reliability of the pulse energy estimated from the power is lowered. The reliability of the pulse energy estimated from the power can be enhanced by employing a plurality of power sources on the time axis as physical quantities depending on the pulse energy.

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

Fig. 3B shows a histogram of judgment energy when the laser pulse Lp1 is outputted at a constant frequency. The horizontal axis represents determination energy, and the vertical axis represents frequency. In the case where the laser light source 10 is operating normally, the distribution of the judgment energy is substantially in accordance with the normal distribution. The determination energy of most of the laser pulses Lp1 falls within the range of m 占 σ (hereinafter, referred to as the normal range R0) when the average value of the determination energy is represented by m and the standard deviation is represented by?.

Fig. 4A shows a schematic plan view of the object 40. Fig. A plurality of processing points 41 are defined on the surface of the object 40. [ And the laser pulse Lp2 (FIG. 1) is incident on the processing point 41, whereby punching processing is performed. The machining sequence of the machining point 41 is predetermined. In Fig. 4A, an example of the machining sequence is indicated by an arrow. As shown in Fig. 4A, the distance from the machined machining point 41 to the machining point 41 to be machined next is not constant and is non-uniform. If the moving distance of the incident position of the pulsed laser beam is long, the correction time of the beam syringe 20 becomes long. Thus, during 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.

4B shows an example of a timing chart of the pulse laser beam output from the laser light source 10 during the machining period. As shown in Fig. 4B, the frequency of the pulsed laser beam is non-uniform.

Fig. 4C shows a histogram of judgment energy when the frequency of the pulse laser beam is non-uniform. For comparison, the histogram of the judgment energy when the frequency of the pulsed laser beam is constant is shown by a broken line. Generally, the pulse energy of the pulsed laser beam output from the laser light source 10 depends on the frequency. For example, in a carbon dioxide gas laser, as the frequency becomes higher, the pulse energy tends to decrease.

Unevenness of the judgment energy when the frequency is uneven is superimposed on non-uniformity of the judgment energy when the frequency is constant and non-uniformity of the judgment energy due to non-uniformity of the frequency. As a result, if the frequency is not uniform, unevenness of determination energy becomes large. In the case where the frequency is not constant, even when the laser light source 10 is normally operating, the determination energy may deviate from the normal range R0.

A laser pulse having a determination energy deviating from the normal range R0 is used even when the laser energy is within the normal range R0 and only the laser pulse included in the normal range R0 is used for laser processing. It is not used for processing. As a result, the utilization efficiency of the laser energy is lowered. In the embodiments described below, it is possible to suppress the deterioration of the utilization efficiency of the laser energy due to the non-uniformity of the determination energy under the condition that the laser light source 10 normally operates.

Fig. 5 shows a flowchart of a laser machining method according to the embodiment. The laser light source 10 and the beam syringe 20 are controlled based on the position of the processing object 41 (Fig. And outputs the pulsed laser beam. At this time, the path switching unit 15 keeps the output path in a state of being switched to the damper path 17. [ As a result, the pulse laser beam does not enter the stage 23. However, since the beam syringe 20 is controlled, the variation in the correction time of the beam syringe 20 is reflected in the frequency of the pulsed laser beam.

6A shows a timing chart of the laser pulse Lp1 outputted from the laser light source 10 in step S1. The frequency of the pulse laser beam in step S1 is not uniform, as is the frequency of the pulse laser beam in the machining period shown in Fig. 4B. Since the beam syringe 20 is controlled on the basis of the actual position of the processing point 41 and the processing order, the degree of unevenness of the frequency of the pulsed laser beam in step S1 is controlled by the pulse laser Which is equal to the degree of non-uniformity of the frequency of the beam.

The result of the measurement of the photodetector 32 is input to the control device 50. The control device 50 obtains the determination energy of each laser pulse 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 based on the distribution of the determination energy.

A method of determining the allowable range R1 of the determination energy will be described with reference to Fig. 6B. Fig. 6B shows a histogram of judgment energy. For comparison, the distribution of the determination energy when the frequency of the pulsed laser beam is constant is shown by a broken line. The mean value of the distribution of the determination energy obtained in step S1 is denoted by m1, and the standard deviation is denoted by? 1. As an example, the upper limit value of the permissible range R1 is m1 + 3σ1, and the lower limit value is m1-3σ1. The allowable range R1 when the frequency is uneven is wider than the normal range R0 when the frequency is constant in accordance with the diffusion of the non-uniformity of the judgment energy.

In step S3 (Fig. 5), the object to be processed 40 is placed on the stage 23 (Fig. 1). In step S4, the beam syringe 20 is operated to wait until the beam syringe 20 of the pulsed laser beam is corrected. When the beam syringe 20 is corrected, one laser pulse Lp1 is outputted 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 switching unit 15 is switched to the damper path 17. [ Due to this, the detection signal det of the light intensity by the photodetector 32 is inputted 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 falls within the allowable range R1. If the determination energy is out of the allowable range R1, the process returns to step S5 after the fall of the laser pulse Lp1 to output the next laser pulse Lp1. 2) from the laser pulse Lp1 and cuts off the laser beam Lp2 (Fig. 2) by controlling the path switching unit 15 in step S7, . The laser pulse Lp2 enters the object to be processed 40 and punching is performed.

In step S8, it is determined whether machining of all the machining points 41 has been completed. If the machining point 41 remains unprocessed, the process returns to step S4 and the next machining point 41 is machined. In the case where a plurality of laser pulses are incident upon one machining point 41 to perform machining, cycle mode machining or burst mode machining is applied.

In the cycle mode processing, the incident position is moved to the next processing point 41 every time one laser pulse is incident on one processing point 41. It is possible to make laser pulses of a desired number of shots enter the working point 41 by repeating this cycle a plurality of times by setting one cycle of a laser pulse of one shot to all the processing points 41 . When the cycle mode machining is to be performed, it is judged that the machining is finished when the cycle is repeated a desired number of times in step S8.

In the burst mode machining, the laser beam of a desired number of shots is successively incident on one machining point 41, and then the machining point 41 to be machined is machined. When performing the burst mode machining, when the immediately preceding laser pulse and the next laser pulse are incident on the same processing point 41, it is not necessary to operate the beam syringe 20 in step S4.

When all of the machining points 41 have been machined, it is determined in step S9 whether or not the machining object 40 having the same arrangement pattern of the machining points 41 remains. When the raw workpiece 40 remains, the process returns to step S3, and the workpiece 40 to be machined is placed on the stage 23. When the raw workpiece 40 is not left, the machining procedure is terminated.

In the case of machining the object 40 having an arrangement pattern different from the arrangement pattern of the processing points 41 of the immediately processed object 40, the preprocessing preparation procedure of steps S1 to S2 is executed, The allowable range R1 is newly determined.

In the above embodiment, even if the laser pulse Lp1 having the determination energy deviates from the normal range R0 shown in Fig. 6B, the laser pulse whose determination energy falls within the allowable range R1 is used for processing. As a result, the deterioration of the utilization efficiency of the laser energy can be suppressed. When the operation of the laser light source 10 becomes unstable and the determination energy deviates from the allowable range R1, the laser pulse Lp1 is not used for machining. This makes it possible to prevent the deterioration of the machining quality due to the incidence of the laser pulse Lp2 in which the pulse energy is insufficient or excessive.

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

Fig. 7 shows an example of this correspondence relationship. The lower limit value and the upper limit value of the allowable range R1 are stored for each arrangement pattern of the processing point 41. [ In the case where the arrangement pattern of the processing points 41 of the object 40 to be machined next is stored in the correspondence table in Fig. 7, steps S1 to S2 (Fig. 2) can be omitted. In step S6, it may be determined whether or not the determination energy falls within the allowable range R1 stored in the storage device 51. [

While the present invention has been described with reference to the above embodiments, the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like are possible.

10 laser light source
11 irradiation optical system
13 Aperture
15 Path switcher
16 machining path
17 Damper path
18 fold mirror
20 beam syringe
21 objective lens
23 stage
24 mobile device
30 partial reflection mirror
31 beam damper
32 photodetector
40 Object to be processed
41 Work point
50 control device
51 Memory
Lp1, Lp2, Lp3 laser pulses
con control signal
det detection signal
trg trigger signal
R0 normal range
R1 allowable range

Claims (7)

A laser light source for outputting a pulsed laser beam,
A stage for supporting an object to be processed,
A beam syringe for causing the pulsed laser beam outputted from the laser light source to enter the object to be processed and moving the incident position on the surface of the object,
A photodetector for measuring a physical quantity depending on pulse energy of each laser pulse of the pulse laser beam output from the laser light source;
A path switching unit for switching the path of the pulse laser beam output from the laser light source between a first path for entering the object to be processed and a second path for not entering the object to be processed,
Wherein the position of the plurality of processing points on the surface of the object to be processed and the machining order are memorized and based on the position of the machining point, the machining order, and the detection result of the photodetector, Control device for controlling the switching device
Lt; / RTI &
The control device includes:
The beam detector is controlled so that the pulse laser beam is incident on the position of the processing point based on the machining order, and the physical quantity depending on each pulse energy of the laser pulse is measured by the optical detector, Executes a preprocess preparation procedure for determining an allowable range of the physical quantity based on the distribution,
Wherein the physical quantity measured by the photodetector propagates at least a part of the laser pulse falling within the allowable range along the first path during the machining of the object after the preprocessing preparation procedure, And deviating the laser pulse along the second path. The method 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 method according to claim 1 or 2,
The control device performs processing of the object to be processed next when the arrangement pattern of the processing point of the object to be processed next is different from the arrangement pattern of the processing point of the object to be processed immediately before Wherein the pre-machining preparation procedure is executed beforehand to newly determine the allowable range. The method according to claim 1 or 2,
Wherein the physical quantity is the energy of the rising portion of the laser pulse. A step of measuring a physical quantity depending on pulse energy of each laser pulse while controlling the beam syringe so that the pulsed laser beam is incident on a predetermined processing position at a predetermined processing order;
Determining a permissible range of the physical quantity based on the measured distribution of the physical quantity;
A step of irradiating a pulse laser beam to the position of the work point on the object to be processed in the machining order to perform laser machining
To have,
In the step of performing the laser processing, the physical quantity of each laser pulse of the pulse laser beam is measured. When the measurement result falls within the allowable range, at least a part of the laser pulse is incident on the object, And when the measurement result is out of the allowable range, the laser pulse is not incident on the object to be processed. The method of claim 5,
And the upper limit value and the lower limit value of the allowable range are determined based on the standard deviation of the physical quantities. The method according to claim 5 or 6,
Wherein the physical quantity is the energy of the rising portion of the laser pulse.

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