JP2005161329A - Method and apparatus for regulating output of laser machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for adjusting the output of a laser machine capable of maintaining the predetermined machining quality by maintaining the predetermined output of laser beams even when using a laser whose parameters (the frequency and the pulse width) must be changed following the change of the laser output. <P>SOLUTION: Laser beams 11 emitted from a laser 10 are made incident on an acousto-optical element (AO) 12, and the transmittance η of laser beams by the acousto-optical element is changed. The output of the laser beams emitted from the acousto-optical element 12 is set to be a predetermined value thereby. The transmittance of the laser beams by the acousto-optical element 12 is corrected by detecting laser beams 19 emitted from the acousto-optical element 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for adjusting the output of a laser processing apparatus, and more particularly to a laser parameter (pulse) which is suitable for use in a laser drill machine for drilling a printed circuit board using a laser beam. The present invention relates to an output adjustment method and apparatus for a laser processing apparatus using a laser that needs to be changed.

  In a laser drill machine that uses a laser beam to make a hole in a printed circuit board or the like, this occurs due to, for example, deterioration of a laser medium or a primary light source as exemplified by the solid line A in FIG. As the laser output P decreases with time, a laser that needs to change laser parameters (pulse width and frequency) may be used.

  Conventionally, for laser parameters that can be set by voltage or current in addition to pulse width and frequency, by monitoring the light output from the laser and controlling the set current value or set voltage value from the outside, The output on the machined surface could be maintained.

  However, as described above, in the laser of the type that adjusts the output by changing the pulse width or the frequency, there is only a means for changing these two parameters related to the processing. Was changing. That is, when the pulse height H as shown in FIG. 2A decreases, the pulse width W is increased as shown in FIG. 2B or the pulse height H shown in FIG. When the frequency is increased and the number of pulses is increased as described above, the heating time of the surface to be processed becomes longer, the thermal effect becomes larger, and the processing time becomes longer when waiting until it cools or cools down.

  In order to solve such a problem, an optical attenuator may be inserted on the laser output side.

  Further, as similar to the present invention, in Patent Documents 1 and 2, an acoustic-optic modulator (AOM) is used to make the rise and fall of the laser light irradiated to the processing surface abrupt. Thus, it is described that the pulse width is shortened by making it a substantially rectangular wave or increasing the modulation frequency.

  Further, Patent Document 3 discloses that a laser on a processed surface is obtained by a variable attenuator using an optical element having an angle dependency when processing AlTiC (a composite sintered body of aluminum oxide and titanium oxide) by an excimer laser. It is described that the energy density is controlled within a set range to keep the machined surface smooth.

JP 2000-263271 A Japanese National Patent Publication No. 11-500962 Japanese translation of PCT publication No. 7-100672

  However, the optical attenuator has a slow response by manual switching, and feedback control cannot be performed.

  In Patent Documents 1 to 3, it has not been considered to adjust the change in output of the laser processing apparatus over time.

  The present invention has been made to solve the above-mentioned conventional problems, and constantly maintains the output on the processing surface without changing the laser parameters such as the pulse width and frequency, so that the processing quality is constant. Keep it a challenge.

  The present invention relates to an output adjustment method of a laser processing apparatus using a laser that needs to change a laser parameter in accordance with a change in the output of the laser. By changing the transmittance of the laser beam by the optical element, the output of the laser beam emitted from the acoustooptic element is made constant, thereby solving the above-mentioned problem.

  Further, the laser beam emitted from the acoustooptic element is detected, and the transmittance of the laser beam by the acoustooptic element is corrected.

  The present invention also provides an acoustooptic device to which a laser emitted from a laser is incident in an output adjusting device of a laser processing apparatus using a laser that needs to change a laser parameter in accordance with a change in the output of the laser; And a means for changing the transmittance of the laser light from the acoustooptic device, and the output of the laser light emitted from the acoustooptic device is made constant to solve the above problem.

  Further, the apparatus further includes correcting means for detecting the laser beam emitted from the acoustooptic device and correcting the transmittance of the laser beam by the acoustooptic device.

  The correction means includes a pinhole into which leakage light from a processing mirror that reflects laser light toward a processing target is incident, and leakage light detection means to detect laser light that has passed through the pinhole, The transmissivity of the laser beam by the acoustooptic device is changed according to the output of the leak light detection means.

  According to the present invention, when the laser output decreases due to changes over time, the output of the processing point is kept constant without changing the laser parameters (pulse width and frequency), and the processing quality on the processing surface is kept constant. It becomes possible to keep.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In this embodiment, as shown in FIG. 3, an acoustooptic device (AO) 12 for shaping laser light 11 emitted from a laser 10 into a pulse shape suitable for irradiation to the workpiece 8, and the AO12. In a laser drill machine comprising a mirror 18 that changes the direction of the laser beam 13 that has passed through and a condensing lens 20 for condensing the laser beam reflected by the mirror 18 onto the processing surface 8A of the workpiece 8 The transmittance η of the AO 12 is variable, and the intensity of the laser beam 13 that has passed through the AO 12 is always constant regardless of the decrease in the output of the laser 10.

  As the AO 12, in addition to the AOM in which the angle of outgoing light (deflection angle) is fixed, an acousto-optic deflector (AOD) having a variable deflection angle can also be used.

  The laser beam 11 emitted from the laser 10 passes through the AO 12, is guided to the condenser lens 20 by the mirror 18, and is condensed on the workpiece 8. On the other hand, the signal of the RF frequency f and the applied voltage V supplied to the AO amplifier 32 is transmitted to the AO 12 by the amplifier (AO amplifier) 32. The transmittance η of the AOM 12 is variable by the signal of the applied voltage V as illustrated in FIG.

  The laser leakage light 19 transmitted through the mirror 18 is received by the photodiode 42 and detected by the detector 44. The level P3 of the laser leakage light 19 detected by the detector 44 is converted into the level P1 of the laser light 13 by the following equation according to the distribution ratio α (for example, 99%) of the mirror 18.

    P1 = {1 / (1-α)} P3 (1)

  The output P0 monitored inside the laser 10 is monitored by the detector 44, and the converted output P1 is compared by the output comparator 46, so that the output monitored by the detector 44 is constant. V is calculated. The applied voltage calculated here is supplied to the AO amplifier 32.

  Assuming that the output of the laser beam 11 output from the laser 10 is P0, the output P1 of the light passing through the AO 12 (transmittance η) can be expressed by the following equation.

    P1 = η × P0 (2)

  Here, as already described, P1 is obtained by detecting and converting the output P3 of the laser leakage light 19 with the photodiode 42 and the detector 44. Therefore, the machining point output P2 is simultaneously measured in advance and the distribution ratio α is calibrated in advance.

  Hereinafter, the operation will be described with reference to FIG.

(1) Prior Adjustment First, the initial transmittance η ₀ of the AO 12 is set by the AO amplifier 32, and a predetermined loss is set (step 100). Therefore, the output P0 oscillated from the laser 10 is set to be P0 × eta ₀ by passing through the AO12.

(2) Output Adjustment The output P0 monitored inside the laser 10 decreases as shown by the solid line A in FIG. 1 due to deterioration of the laser medium or the primary light source. In this case, if the transmittance η (here, η ₀ ) of the AO 12 is constant, the machining point outputs P1 and P2 also decrease (step 200). Here, the machining point output P1 is converted from the laser leakage light 19 described above (step 210), and from this and the laser internal output P0, the output comparator 46 transmits the transmittance η for keeping P1 constant. And a predetermined applied voltage V is supplied to the AO amplifier 32 (step 230). As a result, the transmittance η of the AO 12 is constantly controlled as indicated by the broken line B in FIG. 1, and a constant output P2 can be obtained as indicated by the alternate long and short dash line C in FIG. 1 (step 250).

  In this embodiment, since the transmittance η of the AO 12 is controlled as compared with the output P0 inside the laser 10, it is possible to control to quickly settle. Note that it may be compared with a set value instead of P0.

  In this embodiment, since the pulse shaping AOM is used as the AO 12, the configuration is simple. Note that an AOM for output adjustment can be provided separately, or an AOD can be used.

  Further, the application target is not limited to the laser drill machine.

Diagram showing an example of laser output over time Time chart for explaining the problem of reduced output in conventional laser drill machines An optical path diagram including a partial block diagram showing a configuration of an embodiment of the present invention A diagram showing an example of the relationship between the applied voltage V of the AOM used in the embodiment and the transmittance η Flow chart showing operation procedure of the embodiment

Explanation of symbols

8 ... Workpiece 8A ... Processed surface 10 ... Laser 11, 13 ... Laser beam 12 ... Acousto-optic element (AO)
DESCRIPTION OF SYMBOLS 18 ... Mirror 19 ... Laser leak light 32 ... AO amplifier 42 ... Photodiode 44 ... Detector 46 ... Output comparator

Claims (5)

In the method of adjusting the output of a laser processing apparatus using a laser that needs to change the parameters of the laser in accordance with the change in the output of the laser,
The laser beam emitted from the laser is incident on the acoustooptic device,
By changing the transmittance of the laser light by the acoustooptic device,
An output adjustment method for a laser processing apparatus, characterized in that the output of laser light emitted from the acoustooptic device is made constant.   The method of adjusting an output of a laser processing apparatus according to claim 1, wherein the laser beam emitted from the acoustooptic element is detected and the transmittance of the laser beam by the acoustooptic element is corrected. In an output adjustment device of a laser processing apparatus using a laser that needs to change a laser parameter in accordance with a change in laser output,
An acoustooptic device on which a laser emitted from the laser is incident;
Means for changing the transmittance of the laser light by the acoustooptic device,
An output adjustment device for a laser processing apparatus, wherein the output of the laser light emitted from the acoustooptic element is made constant.   4. The output of the laser processing apparatus according to claim 3, further comprising correction means for detecting laser light emitted from the acoustooptic element and correcting the transmittance of the laser light by the acoustooptic element. Adjustment device. The correcting means is
A pinhole into which leakage light of a processing mirror that reflects laser light toward a processing target is incident;
A leakage light detecting means for detecting the laser light passing through the pinhole,
5. The output adjusting device for a laser processing apparatus according to claim 4, wherein a transmittance of the laser light by the acoustooptic device is changed in accordance with an output of the leakage light detecting means.

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