JP2001246484A - Laser material processing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve processing speed by eliminating restriction on the speed caused by transfer between processing points. SOLUTION: The device includes a monitoring means for monitoring the energy condition of a leaser beam for each processing point, an X-Y galvano- scanner 19 for irradiating a laser beam to a desired point on a workpiece 16, and a controller 10 for controlling the galvano-scanner in accordance with a result from the monitoring means. The controller, upon completion of the laser beam irradiation on one machining point, makes the galvano-scanner start transferring to the next machining point with the start of the monitoring of the energy condition by the monitoring means; and, if the monitoring result is abnormal, the controller controls the galvano-scanner so as to return to the previous one machining point as the irradiation position of the laser beam so that the irradiation is performed again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method and a processing apparatus, and more particularly to a laser processing method and a processing apparatus which are mainly used for drilling and which are improved so that the processing speed can be improved.

[0002]

2. Description of the Related Art A laser processing apparatus mainly for drilling is generally provided with a so-called XY stage capable of horizontally moving a stage on which a work is mounted in an X-axis direction and a Y-axis direction. . This laser processing apparatus changes the irradiation position of a pulsed laser beam by moving a workpiece by an XY stage. For this reason, it takes time for positioning by the XY stage, and there is a limit to the processing speed. For convenience, this laser processing apparatus is referred to as a first method.

On the other hand, there is provided a laser processing apparatus in which the processing speed is improved by oscillating a laser beam using a galvano scanner. Briefly, a laser beam output from a laser oscillator is guided to an XY galvano scanner after passing through a mask for defining its cross-sectional shape. As is well known, an XY galvano scanner is an X-axis galvanometer mirror for oscillating an incident laser beam in the X-axis direction on a work arranged in a processing area, and an XY galvano mirror for oscillating in an Y-axis direction. And a Y-axis galvanometer mirror. With such an XY galvano scanner, the laser light is swung over the entire predetermined region set on the work through the fθ lens. The work is an XY movable in the X-axis direction and the Y-axis direction.
It is mounted on the stage. For convenience, this laser processing apparatus is referred to as a second method.

In the second method, after processing is performed by oscillating a laser beam on a predetermined area on a work, X
-The next work is arranged in the processing area by the Y stage.
According to the second method, the processing speed can be improved by combining the XY galvano scanner and the XY stage as compared with the first method.

By the way, in the above-mentioned laser processing, processing is performed while monitoring the energy state of the laser beam at each processing point. This will be described for the case of the first method with reference to FIGS.

In FIG. 3, a pulse laser beam from a laser oscillator 21 passes through bending mirrors 22 and 23 to reach a partially transmitting bending mirror 24, where about 9
9% is a processed lens 2 which is reflected and is also called an fθ lens.
The work 26 is irradiated through the reference numeral 5. Work 26 is X
It is mounted on an XY stage 30 movable in the axial direction and the Y-axis direction. About 1% transmitted through bending mirror 24
Is introduced into the energy monitor 27, and the pulse energy is detected for each pulse. The detected pulse energy is sent to the energy comparison circuit 28. The energy comparison circuit 28 can arbitrarily change the threshold value according to the processing conditions, for example, the material and the processed thickness of the work 26, compare the detected pulse energy with the threshold value, and determine the detected pulse energy. When the value is lower, a signal indicating this is output to the trigger pulse generator 29. Upon receiving this signal, the trigger pulse generator 29 outputs a trigger pulse to the laser oscillator 21.
Generate additional pulsed laser light.

[0007] The above operation will be explained by exemplifying specific numerical values.
I will tell. Pulse rate per processing point depending on processing conditions
The number of the lights is determined. For example, 0.4 per shot
(J) pulsed laser light with pulse energy
Per hole (formation of through hole)
It is assumed that one pulse laser beam is irradiated. In the light path
Assuming that there is no energy loss, the energy monitor
The normal pulse energy detection value at 27 is 4 (mJ)
Becomes In consideration of this, the threshold value V _SLWhen
Therefore, it is assumed that 2.5 (mJ) is set. The first
In drilling holes, the energy of the pulsed laser beam
Shhold value V_SLAnd the work 26 has a normal hole
It shall be formed.

In the second drilling, the energy of the pulse laser light is low due to the laser oscillator 21,
If the value falls below the threshold value V _SL , the hole formed in the work 26 does not become a through hole. Energy comparison circuit 28 detects and outputs a signal to the trigger pulse generator 29 to the pulse energy is below the threshold value V _SL. Trigger pulse generator 29
Outputs a trigger pulse to the laser oscillator 21 upon receiving this signal. Upon receiving this trigger pulse, the laser oscillator 21 outputs an additional pulse laser beam at the same cycle as a normal pulse laser beam. As a result, a through-hole completely penetrating the work 26 is formed.

Next, referring to FIG. 4, a case where two pulse laser beams are irradiated for one drilling (through hole formation) processing by a pulse laser beam having a pulse energy of 0.4 (J) per one shot. I will explain. This is because the number of pulsed laser beams per processing point is determined by processing conditions. In this case, assuming that there is no energy loss in the optical path, the normal pulse energy detection value of the energy monitor 27 is 4 (m
J). In consideration of this, the threshold value V
It is assumed that 2.5 (mJ) is set as _SL . In the first drilling, the first pulse laser light P
1, P2 exceeds the threshold value V _SL both holes properly is formed in the workpiece 26.

In the second drilling, the first and second pulsed laser light P
3, P4 are both pulse energy is low, especially 2 shot th pulse energy to below the threshold value V _SL, holes formed in the workpiece 26 is not a through hole. Energy comparison circuit 28 detects and outputs a signal to the trigger pulse generator 29 to the pulse energy is below the threshold value V _SL. Upon receiving this signal, the trigger pulse generator 29
A trigger pulse is output to 1. Upon receiving this trigger pulse, the laser oscillator 21 outputs an additional pulse laser beam P5 at the same period as the normal pulse laser beam. As a result, a through-hole completely penetrating the work 26 is formed.

When the number of pulses per hole is two, as described above, the laser oscillator 21 outputs the second pulse laser beam and then outputs the second pulse laser beam for a fixed time shorter than the period of the pulse laser beam. The presence or absence of a trigger pulse is monitored, and if there is no trigger pulse, the process proceeds to the next processing. Of course, as described with reference to FIG. 4, even after the additional pulse laser light is output, the presence or absence of a trigger pulse is monitored for a certain period of time, and if there is no trigger pulse, the process proceeds to the next processing.

FIGS. 3 and 4 show the case where the above-described first method is adopted. In the case of the second method, an XY galvano scanner is used instead of the bending mirror 24. The operation itself does not change.

[0013]

Here, heretofore,
The above operation is performed for one processing point, and after the processing is determined to be normal, the processing is moved to the next processing point. When an XY galvano scanner is used, it usually takes 2 msec to move from one processing point to the next processing point, depending on the distance between adjacent processing points.
c. This will be described with reference to FIG.

In FIG. 5, at a time T1, the laser beam moves to a certain processing point and is irradiated with a pulse laser beam. For example, 1
When irradiating one pulse laser beam to one hole, when the pulse laser beam is radiated, the energy monitor 27 and the energy comparison circuit 28 determine whether or not the hole is normal. The time required for this determination is about 150 μsec. Then, the movement to the next machining point is started only at time T2 when it is determined that the processing is normal.

However, when the above-mentioned laser processing apparatus is used for drilling a resin layer of a printed wiring board, for example, a hole having a diameter of several tens of μm is formed in a square region having a side of several cm. Drilling is performed such that a large number, for example, several thousands, are provided at a pitch. In such a drilling process, as described above, in the method in which the processing at one processing point is determined to be normal and then the processing is moved to the next processing point, there is a restriction on the improvement of the processing speed.

An object of the present invention is to provide a laser processing method capable of improving the processing speed by eliminating the restriction on the processing speed caused by the movement between the processing points.

Another object of the present invention is to provide a laser processing apparatus suitable for the above-described laser processing method.

[0018]

According to the present invention, there is provided a laser processing method for performing processing while monitoring the energy state of laser light at each processing point when irradiating a workpiece with laser light. When the irradiation of the laser beam to one processing point is completed, the movement to the next processing point is started with the start of the monitoring of the energy state. There is provided a laser processing method characterized by performing irradiation.

According to the present invention, in a laser processing apparatus for performing processing by irradiating a laser beam from a laser oscillator onto a workpiece, a monitoring means for monitoring an energy state of the laser beam for each processing point; A galvano scanner for irradiating a desired processing point on the workpiece; and a control device for controlling the galvano scanner in accordance with a monitoring result from the monitoring means, wherein the control device includes a laser for one processing point. When the light irradiation ends, the monitoring unit starts moving to the next processing point with the monitoring of the energy state by the monitoring unit. Laser beam irradiation again by returning the laser beam irradiation position to the one processing point. The laser processing apparatus is provided, characterized by controlling so as to.

In the above laser processing apparatus, the monitoring means is a detection means for detecting the energy of the laser beam applied to one processing point, and the energy value detected by the detection means is set in advance. Comparing means for comparing with a threshold value and outputting a signal indicating that the detected energy value is not normal when the detected energy value is lower than the threshold value.

[0021]

1 and 2, an embodiment of a laser processing apparatus according to the present invention will be described. 1, the laser processing apparatus according to the present embodiment includes an XY galvano scanner 19 in addition to the configuration described in FIG. 3, and includes a control device 10 instead of the trigger pulse generator 29. Other configurations are the same as those shown in FIG. That is, the pulsed laser light from the laser oscillator 11 reaches the partially transmitting bending mirror 14 via the bending mirrors 12 and 13, where about 99% is reflected and enters the XY galvano scanner 19. As described above, the XY galvanometer scanner 19 includes an X-axis galvanometer mirror for oscillating the incident pulse laser light on the work 16 in the X-axis direction, and a Y-axis galvanometer for oscillating the incident laser beam in the Y-axis direction. Consists of a mirror. By such an XY galvano scanner 19, the pulse laser light is swung through the processing lens (fθ lens) 15 so as to cover the entire predetermined region set on the work 16. The work 16 is mounted on an XY stage 20 movable in the X-axis direction and the Y-axis direction. XY stage 20 is XY
Since the scanning range of the galvano scanner 19, that is, the processing area is limited, it is used when shifting the processing area. Although not shown, a mask for defining the cross-sectional shape of the laser beam applied to the work 16 is usually arranged in the optical path between the laser oscillator 11 and the XY galvano scanner 19. .

About 1% transmitted through the bending mirror 14
Is introduced into the energy monitor 17, and the pulse energy is detected for each pulse. The detected pulse energy is sent to the energy comparison circuit 18. The energy comparison circuit 18 can arbitrarily change the threshold value according to the processing conditions, for example, the material and the processing thickness of the work 16, compare the detected pulse energy with the threshold value, and determine the detected pulse energy. When the value is lower, a signal indicating this is output to the controller 10.

The controller 10 causes the XY galvano scanner 19 to start moving to the next processing point as soon as the irradiation of one processing point is completed. When a signal indicating that the pulse energy is lower is received, the irradiation position of the pulse laser light with respect to the XY galvanometer
By returning to one processing point and outputting a trigger pulse to the laser oscillator 11 to generate additional pulsed laser light, control is performed so that the one processing point is irradiated with laser light again.

The above operation will be described with reference to FIG. 2 using specific numerical values. For example, 0.
4 (J) pulsed laser light with pulse energy of 1 (per hole)
It is assumed that one pulse laser beam is irradiated. Assuming that there is no energy loss in the optical path, the normal pulse energy detected value by the energy monitor 17 is 4 (mJ).
Becomes In consideration of this, it is assumed that the threshold value V _SL is set to 2.5 (mJ). In FIG. 2, in the first drilling, the energy of the pulsed laser beam exceeds the threshold value _VSL and the work 16
A hole is formed normally in. The determination by the energy monitor 17 and the energy comparison circuit 18 requires about 150 μsec as described above.
0 controls the XY galvano scanner 19 to move the laser beam irradiation to the next processing point as soon as the irradiation of the pulse laser beam for the first hole is completed without waiting for this determination result. I do. Hereinafter, it is assumed that the second and third drilling operations are normally performed.

Subsequently, in the fourth drilling, if the energy of the pulsed laser beam is low due to the laser oscillator 11 and falls below the threshold value V _SL , the hole formed in the work 16 becomes a through hole. No. Energy comparison circuit 18 detects and outputs a signal to the controller 10 that the pulse energy is below the threshold value V _SL.

The control device 10 causes the XY galvano scanner 19 to start moving to the next processing point as soon as the laser beam irradiation for the fourth hole processing is completed. Receiving the signal indicating that the detected pulse energy is lower, the XY galvano scanner 19 is caused to return the irradiation position of the pulse laser light to the fourth hole processing position, and furthermore, the laser oscillator 1
By outputting a trigger pulse to 1 to generate additional pulsed laser light, the fourth hole processing position is again irradiated with laser light. Upon receiving a trigger pulse from the control device 10, the laser oscillator 11 outputs an additional pulse laser beam at the same cycle as a normal pulse laser beam. As a result, a through hole that completely penetrates the work 16 is formed.

The above operation is the same when two or more pulsed laser beams are irradiated to one hole. For example, a case will be described in which two pulsed laser beams are irradiated for one drilling (forming of a through hole) by a pulsed laser beam having a pulse energy of 0.4 (J) per shot. In this case, assuming that there is no energy loss in the optical path, the energy monitor 17
Is 4 (mJ). In view of this, it is assumed that 2.5 as threshold value V _SL (mJ) is set. 1 shot first in the first drilling, beyond the 2 shot th pulse laser beam both threshold value V _SL, a hole normally is formed in the workpiece 16. The determination by the energy monitor 17 and the energy comparison circuit 18 is performed as described above.
Although it takes about 0 μsec, the control device 10 controls the XY galvano scanner 19 to move the laser beam irradiation to the next processing point without waiting for this determination result.

Next, in the second drilling, the pulse energy of both the first pulse laser light and the second pulse laser light is low due to the laser oscillator 11, and especially the second pulse energy has a threshold value V _{If it} is less than _SL , the hole formed in the work 16 will not be a through hole. Energy comparison circuit 18 detects and outputs a signal to the controller 10 that the pulse energy is below the threshold value V _SL. The control device 10 causes the XY galvano scanner 19 to start moving to the next processing point immediately after the second laser beam irradiation for the second hole processing is completed. When a signal indicating that the detected pulse energy is lower is received from the control unit 18, the irradiation position of the pulse laser beam is returned to the second hole processing position with respect to the XY galvano scanner 19. By outputting a trigger pulse to 11 and generating additional pulse laser light, the second hole processing position is again irradiated with laser light. Upon receiving a trigger pulse from the control device 10, the laser oscillator 11 outputs an additional pulse laser beam at the same cycle as a normal pulse laser beam. As a result, a through hole that completely penetrates the work 16 is formed.

For example, the moving time from one processing point to the next processing point by the XY galvano scanner 19 is 2 msec.
The determination time in the energy monitor 17 and the energy comparison circuit 18 is set to 150 μsec, and 100,000
Assuming the case of performing individual drilling, in the case of the method described with reference to FIG. 3, the total processing time is (2 msec + 0.
15 msec) × 100,000 = 215 sec.
On the other hand, in the case of the method according to the present embodiment, assuming that the probability of occurrence of an additional shot due to energy shortage is 1/100000,
Total processing time is (2msec × 100,000) +
(2mse re-moving time required for additional shots
c × 2), which is about 200 sec. As a result, about 1
A processing time reduction of 5 seconds can be realized.

As described above, such a reduction in the processing time is achieved by forming a hole having a diameter of several tens of μm in a square area having a side of several cm in the hole drilling in the resin layer of the printed wiring board. This is very effective in the case where a large number of holes, for example, several thousand holes are formed continuously at a pitch of μm.

In the above description, the case where the energy comparison circuit 18 makes a comparison for each pulse laser beam has been described. Alternatively, the determination may be made by adding the pulse energies for two shots and comparing this with the threshold value for two shots.

[0032]

As described above, according to the present invention, it is possible to improve the processing speed by eliminating the restriction on the processing speed caused by the movement between the processing points.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a laser processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the relationship between the determination of the energy of the pulse laser beam and the travel time between processing points in the laser processing apparatus shown in FIG.

FIG. 3 is a diagram showing a schematic configuration of a conventional laser processing apparatus.

FIG. 4 is a diagram for explaining an operation of determining the energy of a pulse laser beam in the laser processing apparatus shown in FIG. 3;

5 is a diagram for explaining the relationship between the determination of the energy of a pulse laser beam and the travel time between processing points in the laser processing apparatus shown in FIG. 3;

[Explanation of symbols]

 Reference Signs List 10 control device 11, 21 laser oscillator 12, 13, 22, 23 bending mirror 14, 24 partially transmitting bending mirror 15, 25 processing lens 16, 26 work 17, 27 energy monitor 18, 28 energy comparison circuit 19 X- Y galvanometer scanner 20, 30 XY stage

Claims (3)

[Claims] In a laser processing method for performing processing while monitoring the energy state of a laser beam for each processing point when performing processing by irradiating a laser beam to a workpiece, laser light irradiation to one processing point is completed. Then, the movement to the next processing point is started with the start of the monitoring of the energy state, and if the monitoring result is not normal, the processing is returned to the one processing point and the laser beam irradiation is performed again. Method. 2. A laser processing apparatus for performing processing by irradiating a laser beam from a laser oscillator onto a workpiece, wherein a monitoring means for monitoring an energy state of the laser beam for each processing point; A galvano scanner for irradiating a processing point, and a control device for controlling the galvano scanner according to a monitoring result from the monitoring means, wherein the control device is configured to terminate laser light irradiation on one processing point. In accordance with the start of monitoring of the energy state by the monitoring means, the galvano scanner is caused to start moving to the next processing point, and if the result of the monitoring is not normal, the galvano scanner is irradiated with laser light. Control to return the position to the one processing point and perform laser beam irradiation again The laser processing apparatus according to claim Rukoto. 3. A laser processing apparatus according to claim 2, wherein said monitoring means detects energy of a laser beam applied to one processing point, and detects an energy value detected by said detection means in advance. A laser processing apparatus comprising: a comparing unit that compares the detected energy value with a set threshold value and outputs a signal indicating that the detected energy value is not normal when the detected energy value is lower than the threshold value.