JP2013215769A - Laser beam machining apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus that prevents a risk in which a machining head is broken by the disturbance of a liquid column.SOLUTION: A laser beam machining apparatus includes: a holding means for holding a workpiece; and a laser beam emitting means comprising at least a laser oscillator and a machining head and emitting a laser beam onto the workpiece held with the holding means. The machining head is provided with: a condensing lens for condensing a laser beam oscillated from the laser oscillator; a liquid jetting means for forming a liquid column into which the laser beam condensed with the condensing lens is guided by jetting the liquid onto the workpiece; a pipe through which the liquid column formed by the liquid jetting means passes; a gas inflow path which makes the gas, for rectifying the liquid column by surrounding the liquid column, flow into the pipe; and a means for detecting the abnormality of the liquid column for detecting the abnormality of the gas, which flows in the gas inflow path, as the abnormality of the liquid column.

Description

  The present invention relates to a water jet laser processing apparatus.

  Conventionally, a so-called water jet that forms a liquid column by injecting a high-pressure liquid onto a workpiece and irradiates the workpiece with a laser beam transmitted (light-guided) into the liquid column to perform a required process. Laser processing apparatuses are widely known (see, for example, Patent Documents 1 to 3).

  Then, as disclosed in Patent Document 4, the present applicant has proposed a water jet laser processing apparatus that can form a laser processing groove width of, for example, 50 μm or less by rectifying the liquid column.

  In Patent Document 4, a laser beam is incident on a liquid chamber housing through a transparent window, and the laser beam is guided into a liquid column formed by an ejection nozzle provided on the liquid chamber housing.

  The liquid column is jetted onto the workpiece through the pipe, and the liquid column is rectified by the gas (air) sucked into the pipe through the gas inflow path surrounding the liquid column. Yes.

Japanese Patent Laid-Open No. 2-1621 JP 2001-321977 A JP 2006-255769 A JP 2011-125870 A

  In the conventional water jet laser processing apparatus, the liquid forming the liquid column is reflected from the upper surface of the workpiece and flows back through the liquid column, and may adhere to the inside of the pipe through which the liquid column passes or the inside of the injection nozzle. There is concern that this may disturb the newly formed liquid column.

  Further, due to the displacement of the assembly position of the optical component, the laser beam is applied to the edge of the injection nozzle, the injection nozzle is damaged, and the liquid column may be disturbed due to the damage of the injection nozzle.

  Furthermore, when a foreign substance is mixed in the liquid forming the liquid column, the liquid column may be disturbed by irradiating the foreign substance with a laser beam guided to the liquid column.

  As the liquid column is disturbed as described above, the condensing of the laser beam fluctuates, the laser beam is irradiated to the edge of the injection nozzle, the injection nozzle is damaged, or the transparent window is burned out. There is a risk.

  In addition, when the laser beam is irradiated onto the pipe due to the disturbance of the liquid column, there is a risk that the pipe is melted and the pipe hole is welded and closed. If the pipe hole is blocked by welding, there is a problem that the liquid ejected from the liquid chamber housing flows into the gas inflow path and the machining head itself is greatly damaged.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a laser processing apparatus that prevents the processing head from being damaged due to the disturbance of the liquid column.

  According to the first aspect of the present invention, the holding means for holding the workpiece, the laser beam irradiation means for irradiating the workpiece held by the holding means with a laser beam, comprising at least a laser oscillator and a machining head; The processing head includes a condensing lens for condensing the laser beam oscillated from the laser oscillator, and a liquid for guiding the laser beam condensed by the condensing lens by injecting liquid onto the workpiece. A liquid ejecting means for forming a column, a pipe through which a liquid column formed by the liquid ejecting means passes, a gas inflow passage for allowing a gas surrounding the liquid column and rectifying the liquid column to flow into the pipe, and a gas inflow There is provided a laser processing apparatus including a liquid column abnormality detecting means for detecting an abnormality of a gas flowing in a path as a liquid column abnormality.

  According to a second aspect of the present invention, the laser processing further comprises control means for stopping emission of the laser beam from the laser beam irradiation means when the liquid column abnormality detection means detects the disturbance of the liquid column. An apparatus is provided.

  According to the present invention, it is possible to detect abnormality of the gas flowing in the gas inflow path by the liquid column abnormality detecting means, and by using this detection result, the machining head is damaged due to the disturbance of the liquid column. The fear can be prevented.

  Specifically, by stopping the emission of the laser beam when the disturbance of the liquid column is detected, the part of the injection nozzle or pipe is damaged due to the laser beam being emitted while the liquid column is disturbed. It is possible to prevent the occurrence of problems such as

It is a longitudinal cross-sectional view of the processing head part which concerns on this invention embodiment. It is a block diagram of a laser beam generation unit. FIG. 2 is a partial longitudinal cross-sectional view of a processing head section taken in a direction perpendicular to the paper surface in FIG. 1. It is an expanded longitudinal cross-sectional view of the gas introduction part of a process head.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a longitudinal sectional view of a processing head portion of a laser processing apparatus according to an embodiment of the present invention. FIG. 3 is a partial longitudinal sectional view of the laser processing head, which is a cross section of FIG.

  The laser beam irradiation unit 10 of the laser processing apparatus includes a laser beam generation unit 12, a control unit 15 as a control means for controlling the laser beam generation unit 12, and a laser beam generated from the laser beam generation unit 12 as a semiconductor wafer. And a processing head 14 for irradiating the workpiece 11.

  As shown in FIG. 2, the laser beam generation unit 12 includes a laser oscillator 16 that oscillates a YAG laser or a YVO4 laser, a repetition frequency setting means 18, a pulse width adjustment means 20, and a power adjustment means 22. Is done. The laser beam generation unit 12 is configured to be controlled by the control unit 15. For example, the power adjustment unit 22 is controlled by the control unit 15, so that the laser output can be adjusted in magnitude or stopped. It has been made. The control unit 15 may be configured to be integrated with the laser beam generation unit 12, or may be configured to be incorporated in a control device provided in another part. It is not limited.

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 22 of the laser beam generating unit 12 is introduced into the machining head 14 from a beam inlet 27 formed in the housing 24 of the machining head 14 as shown in FIG. Is done.

  In the housing 24, a mirror 26 for reflecting the laser beam and a condenser lens 28 for condensing the laser beam are disposed. A liquid chamber housing 36 that defines the liquid chamber 34 of the liquid ejecting unit 30 integrally with the housing 24 is formed. The liquid chamber housing 36 includes a cylindrical side wall 38 and an upper wall 40 and a lower wall 42 that close the upper and lower surfaces of the side wall 38, respectively.

  A transparent window 46 is disposed on the upper wall 40 constituting the liquid chamber housing 36. An injection nozzle 48 is formed at the center of the lower wall 42 constituting the liquid chamber housing 36.

  A liquid inlet 44 that opens into the liquid chamber 34 is formed in the side wall 38, and the liquid inlet 44 is connected to the high-pressure liquid supply source 32. When high pressure liquid is supplied from the high pressure liquid supply source 32 into the liquid chamber 34, the high pressure liquid is ejected from the ejection port 48 a of the ejection nozzle 48 to form the liquid column 50.

  A gas introduction housing 52 is attached to the lower end of the liquid chamber housing 36. The gas introduction housing 52 includes a cylindrical wall 54 attached to the lower wall 42 of the liquid chamber housing 36, and an annular bottom wall 56 formed integrally with the lower end portion of the cylindrical wall 54.

  A through hole 60 is formed at the center of the annular bottom wall 56, and a pipe 62 is press-fitted into the through hole 60. A gas inflow path 64 is defined by a space surrounded by the cylindrical wall 54 and the annular bottom wall 56, and air flows into the gas inflow path 64 from gas inlets 66 and 67 formed in the cylindrical wall 54. The gas inlets 66 and 67 may be open to the atmosphere, or are connected to a high-pressure gas supply source (not shown) and the pressurized gas flows into the gas inflow path 64 through the gas inlets 66 and 67. It may be a thing.

  An annular suction port 68 is defined by an inner wall 58 formed on the lower surface of the annular bottom wall 56 of the gas introduction housing 52, and this suction port 68 communicates with an annular suction path 70, as shown in FIG. In addition, the annular suction path 70 is connected to a suction source 72 through a discharge port 71 formed in the cylindrical wall 54.

  As shown in the enlarged cross-sectional view of FIG. 4, the inner peripheral wall on the inlet side of the pipe 62 is formed in a tapered shape 62a extending toward the inlet side, and the inner peripheral wall on the outlet side is also formed in a tapered shape 62b extending toward the outlet side. ing.

  Reference numeral 13 denotes a holding table (chuck table) of the laser processing apparatus, and a workpiece 11 such as a semiconductor wafer is sucked and held on the holding table 13. Reference numeral 11 a denotes a processing point at which the workpiece 11 is irradiated with the laser beam 25 guided by the liquid column 50.

  In the laser processing apparatus configured as described above, the laser beam 25 adjusted to a predetermined power by the power adjusting means 22 of the laser beam generating unit 12 is supplied from the beam introduction port 27 (FIG. 1) of the processing head 14. Then, the light is reflected by the mirror 26 and condensed by the condenser lens 28 at the processing point 11a.

  On the other hand, a high-pressure liquid such as pure water supplied from the high-pressure liquid supply source 32 is introduced into the liquid chamber 34 from the liquid inlet 44 formed in the liquid chamber housing 36 of the liquid ejecting unit 30, and the liquid chamber housing 36 A liquid column 50 is formed by being sprayed from a spray nozzle 48 formed on the lower wall 42.

  The liquid column 50 passes through the pipe 62 press-fitted into the through hole 60 of the inner wall 58 of the gas introduction housing 52, collides with the processing point 11 a of the workpiece 11 and scatters. The laser beam 25 condensed by the condensing lens 28 is guided (guided) to the liquid column 50 passing through the pipe 62 and irradiated to the processing point 11 a to form a laser processing groove in the workpiece 11.

  Since the liquid column 50 formed by jetting high-pressure liquid from the jet nozzle 48 passes through the pipe 62 at high speed, a suction force is generated. Therefore, the gas (air) taken into the gas inflow path 64 through the gas inlets 66 and 67 is sucked into the pipe 62 as shown by an arrow A in FIG. Encloses the liquid column 50 and rectifies the liquid column.

  The liquid column 50 formed by being ejected from the ejection nozzle 48 is rectified by the gas and does not cause the liquid column 50 to expand, so that the laser beam is guided through the liquid column 50 and irradiated onto the workpiece 11. The width of the laser processing groove formed in the workpiece 11 can be suppressed to a narrow width of 50 μm or less without expanding the beam diameter of 25.

  The inner diameter of the pipe 62 is preferably 1 mm or less, more preferably about φ0.5 mm. The length of the pipe 62 is preferably 5 mm or more, more preferably about 20 mm. The distance from the outlet of the pipe 62 to the upper surface of the workpiece 11 is preferably about 0.4 to 5 mm. The diameter of the liquid column 50 is preferably 0.15 mm or less, and the flow rate of the liquid column 50 and the flow rate of the gas flowing into the pipe 62 are substantially the same.

  A part of the processing debris (debris) generated by the laser processing is taken into the liquid that forms the liquid column 50 that collides with the processing point 11a of the workpiece 11 and scatters, and the suction source 72 is operated. The liquid and gas containing the processing waste are sucked from the upper surface of the workpiece 11 through the suction port 68, and sucked to the suction source 72 through the suction path 70 and the discharge port 71.

  In the above-described embodiment, the pipe inner peripheral wall on the inlet side of the pipe 62 has a tapered shape 62a that spreads toward the inlet side, and the thickness of the pipe 62 is reduced on the inlet side, so that water droplets adhere to the inlet side of the pipe 62. It is possible to prevent the inflowing gas flow from being disturbed.

  In addition, since the pipe inner peripheral wall on the outlet side of the pipe 62 has a tapered shape 62b that widens toward the outlet side, it is possible to prevent the turbulence of the air flow that occurs due to a sudden change in diameter at the outlet end of the pipe 62. Furthermore, since the thickness of the pipe 62 is reduced at the outlet end, it is possible to prevent water droplets from adhering to the outlet side of the pipe 62 and disturbing the liquid column 50 due to dripping of the adhered water droplets.

The processing conditions when a silicon wafer is used as the workpiece 11 can be as follows, for example.
Light source: LD excitation Q switch Nd: YVO4 laser Wavelength: 532 nm
Average output: 100W
Repetition frequency: 40 kHz
Nozzle diameter: φ50μm
Liquid pressure: 30 MPa (water pressure for liquid column formation)
Processing feed rate: 100 mm / s

  In addition, in the above processing conditions, it was confirmed that a laser processing groove having a depth of 40 μm and a width of 47 μm can be formed on the silicon wafer when the distance between the nozzle outlet and the pipe upper end is 4 mm and the pipe length is 20 mm. ing.

  As described above, the laser processing apparatus of this embodiment includes at least the holding table (holding means) 13 that holds the workpiece 11, the laser oscillator 16, and the processing head 14, and the workpiece held by the holding table 13. A laser beam irradiation unit (laser beam irradiation means) 10 for irradiating the workpiece 11 with a laser beam. The processing head 14 includes a condensing lens 28 for condensing the laser beam oscillated from the laser oscillator 16, a target lens A liquid ejecting unit (liquid ejecting means) 30 that forms a liquid column 50 through which liquid is ejected onto the workpiece 11 and a laser beam condensed by the condensing lens 28 is guided, and the liquid ejecting unit 30 is formed. A pipe 62 through which the liquid column 50 passes and a gas inflow path 64 through which the gas surrounding the liquid column 50 and rectifying the liquid column 50 flows into the pipe 62. Has a configuration having a.

  Next, a configuration for preventing breakage of the machining head due to liquid column disturbance, which is a characteristic configuration of the present invention, will be described. In the present embodiment, as shown in FIG. 1, the liquid column abnormality detecting means for detecting an abnormality of the gas flowing through the gas inflow path 64 as an abnormality of the liquid column 50 is provided. It is going to be realized in.

  First, it is set as the structure by which the flow rate sensors 81 and 82 for detecting the gas flow volume are each provided in the gas inflow ports 66 and 67 installed in two places of the gas introduction housing 52. FIG. The flow rate sensors 81 and 82 can detect the flow rate of gas (air) flowing into the gas inlets 66 and 67.

  Further, the inner peripheral wall portion 54 a of the cylindrical wall 54 of the gas introduction housing 52 is configured to include an acoustic sensor 83 for detecting sound in the gas inflow passage 64. The acoustic sensor 83 can detect sound waves (dB (volume), frequency, etc.) of gas (air) flowing through the gas inflow path 64.

  Further, the inner peripheral wall portion 54 a of the cylindrical wall 54 of the gas introduction housing 52 is configured to include a pressure sensor 84 for detecting the pressure in the gas inflow passage 64. The pressure of the gas (air) flowing through the gas inflow path 64 can be detected by the pressure sensor 84.

  As shown in FIG. 2, each of the sensors 81 to 84 is connected to a control unit 15 that controls the laser beam generation unit 12. The control unit 15 includes a memory for storing data detected by various sensors and a memory for storing a program, an arithmetic device for processing the program, an input / output interface, and the like.

  The control unit 15 detects the disturbance of the liquid column 50 by the sensors 81 to 84 in order to prevent the machining head from being damaged due to the disturbance of the liquid column 50. The laser beam irradiation unit (laser beam irradiation means) 10 The emission of the laser beam from is stopped.

  As a specific method for detecting the disturbance of the liquid column 50, for example, detection is performed based on fluctuations in an actual measurement value (gas flow rate) at the gas inlet 66 detected by the flow sensor 81. That is, when a change in which the flow rate increases or decreases by a predetermined value or a rate is detected with reference to a predetermined reference value, it is specified as the disturbance of the liquid column 50. .

  For example, when the flow rate at the gas inlet 66 is reduced by 50 sccm from the reference value, it is considered that the emission of the laser beam is stopped because the liquid column 50 is disturbed.

  The “predetermined reference value” is, for example, a gas flow rate in a normal state in which the liquid column 50 is not disturbed, and this reference value is stored in the memory (control unit 15) as appropriate. It can be used for comparison with actual measurement values measured by the flow sensor 81.

  Also, the actual measurement values detected for the other sensors 82 to 84 can be used to detect the disturbance of the liquid column 50 as with the flow sensor 81. That is, the measured value of the flow sensor 82 can be used for comparison with the reference value (gas flow rate) in the same manner as the measured value of the flow sensor 81. The actual measurement value of the acoustic sensor 83 is used for comparison with the sound wave (dB (volume), frequency, etc.) of the gas (air) flowing through the gas inflow path 64 in a normal state where the liquid column 50 is not disturbed. it can. The measured value of the pressure sensor 84 can be used for comparison with the pressure of the gas (air) flowing through the gas inflow path 64 in a normal state where the liquid column 50 is not disturbed.

  As described above, the control unit 15 can detect the disturbance of the liquid column 50. When the disturbance of the liquid column 50 is detected, the control unit 15 stops the emission of the laser beam, thereby processing the liquid column 50 by the disturbance. The possibility that the head is damaged can be prevented. Specifically, it is possible to prevent the occurrence of problems such as damage to the injection nozzle 48 and the pipe 62 due to the laser beam being emitted while the liquid column is disturbed.

  In the above embodiment, the flow rate sensor 81 (first flow rate sensor) that detects the gas flow rate flowing into the gas inflow path 64 from the gas flow inlet 66 (first gas flow inlet), and the gas flow inlet 66 (second flow rate). A flow rate sensor 82 (second flow rate sensor) that detects the flow rate of gas flowing into the gas inflow path 64 from the gas inlet), an acoustic sensor 83 that detects sound waves generated by the disturbance of the liquid column flowing through the gas inflow path 64, and gas A total of four pressure sensors 84 that detect the pressure of the gas flowing through the inflow path 64 are provided, but any one of the sensors may be provided. In addition, for example, detecting abnormality by combining a plurality of measured values, such as stopping emission of a laser beam when disturbance of the liquid column 50 is detected in at least two of the four sensors. Also good.

DESCRIPTION OF SYMBOLS 10 Laser beam irradiation unit 11 Work piece 12 Laser beam generation unit 14 Processing head 15 Control unit 25 Laser beam 30 Liquid injection unit 48 Injection nozzle 50 Liquid column 62 Pipe 64 Gas inflow path 66 Gas inflow port 67 Gas inflow port 81 Flow rate sensor 82 Flow sensor 83 Acoustic sensor 84 Pressure sensor

Claims (2)

A laser processing device,
Holding means for holding the workpiece;
Comprising at least a laser oscillator and a machining head, and a laser beam irradiation means for irradiating a workpiece held by the holding means with a laser beam,
The processing head includes a condensing lens that condenses a laser beam oscillated from the laser oscillator;
Liquid ejecting means for ejecting liquid onto a workpiece and forming a liquid column through which the laser beam condensed by the condenser lens is guided;
A pipe through which the liquid column formed by the liquid ejecting means passes;
A gas inflow path for allowing a gas surrounding the liquid column and rectifying the liquid column to flow into the pipe;
A liquid column abnormality detecting means for detecting an abnormality of the gas flowing in the gas inflow path as an abnormality of the liquid column;
Laser processing equipment equipped with. Control means for stopping emission of the laser beam from the laser beam irradiation means when the liquid column abnormality detection means detects the disturbance of the liquid column,
The laser processing apparatus according to claim 1.

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