JP4490410B2 - Laser irradiation apparatus and laser processing method - Google Patents

Description

  The present invention relates to a laser irradiation apparatus and a laser processing method, and more particularly to a laser irradiation apparatus that irradiates a workpiece with a plurality of laser beams branched from one laser beam, and a laser processing method using the laser irradiation apparatus.

  A laser beam is used for drilling a printed wiring board or the like. In order to improve productivity, a technique for branching one laser beam emitted from a laser oscillator into a plurality of laser beams and simultaneously forming holes at a plurality of processing points is disclosed in Patent Documents 1 and 2 below. Is disclosed.

JP-A-2005-74479 Japanese Patent Laid-Open No. 2002-11484

  When one laser beam is branched, the intensity per laser beam decreases. When drilling with a pulsed laser beam, the energy density per pulse (pulse energy density) must be greater than or equal to the minimum pulse energy density (threshold) required for drilling. In the case of processing a material that can be easily processed (material having a low threshold value), the processing time can be shortened by performing processing by branching one laser beam into a plurality of laser beams. However, a single laser beam can secure a pulse energy density that is equal to or higher than the threshold value, but if it is branched into two, a material that causes the pulse energy density of each laser beam to become less than the threshold value is processed. In this case, the processing cannot be performed by branching into two.

  When a material that can be processed by only one laser beam and a material that can be processed by a plurality of branched laser beams are mixed in one object to be processed, a state in which one laser beam is incident; It is convenient if it is possible to switch between a state in which a plurality of branched laser beams are incident. In the conventional laser processing apparatus, in order to perform this switching, it is necessary to change the arrangement of various optical elements. If the arrangement of the optical elements is changed, it takes time to adjust the optical axis and the like, leading to a reduction in the operating rate of the apparatus.

  An object of the present invention is to provide a laser irradiation apparatus capable of easily switching between a state where one laser beam is not branched and a state where one laser beam is branched. Another object of the present invention is to provide a method of performing laser processing using this laser irradiation apparatus.

According to one aspect of the invention,
A beam path switch that switches between a first state in which a laser beam emitted from a laser light source is propagated to the first path and a second state in which the laser beam is propagated to the second path is switched by a control signal;
A first beam splitter for branching a part of the laser beam propagating through the second path into a third path and a remaining component propagating through the second path ;
There is provided a laser irradiation apparatus including a first beam combiner that combines a laser beam propagating through the third path with a laser beam propagating through the first path.

According to another aspect of the invention,
Preparing a workpiece on which a surface layer made of a material in which holes are relatively difficult to be formed by a laser beam on a base member made of a material in which holes are relatively easily formed by a laser beam;
With the beam path switch of the laser irradiation apparatus described above in the first state, the laser beam propagating through the first path is incident on the first workpiece point on the workpiece, and the first workpiece Removing the surface layer of the processing point;
The beam path switch is maintained in the first state, a laser beam propagating through the first path is incident on a second workpiece point on the workpiece, and the second workpiece point is Removing the surface layer;
The beam path switching unit is set to the second state, and a laser beam propagating through the first path after being synthesized by the first beam combiner is incident on the first processing point at the same time. A laser beam propagating through the second path after being branched by the two beam splitters is incident on the second workpiece point to form holes in the base members of the first and second workpiece points. There is provided a laser processing method having a process.

  When the beam path switch is in the first state, the laser beam is emitted along the first path. In the second state, two laser beams are emitted along the first path and the second path. Processing using one laser beam and processing using two laser beams can be easily switched.

  FIG. 1 shows a schematic view of a laser irradiation apparatus according to the first embodiment. A laser light source 1 emits a linearly polarized laser beam. A laser beam emitted from the laser light source 1 enters the beam propagation optical system 10. As the laser light source 1, various laser oscillators such as a carbon dioxide laser, an Nd: YAG laser, and an excimer laser can be used. Further, the laser oscillator may be continuously oscillated or pulsed.

  The beam propagation optical system 10 emits the laser beam emitted from the laser light source 1 along the first path p1 and the second path p2, and the first state where the laser beam is emitted along the first path p1. The second state can be switched. The laser beam emitted along the first path p1 enters the workpiece 40 via the first galvano scanner 31 and the first fθ lens 33. The laser beam emitted along the second path p <b> 2 enters the workpiece 40 at a different position via the second galvano scanner 32 and the second fθ lens 34. The workpiece 40 is held on the XY stage 35.

  The first and second galvano scanners 31 and 32 scan the laser beams propagating through the first path p1 and the second path p2 in a two-dimensional direction, respectively. The first and second fθ lenses 33 and 34 focus the laser beam on the surface of the workpiece 40.

  The beam propagation optical system 10 includes an acousto-optic deflector (beam path switcher) 11, a half-wave plate 17, a first partial reflector 14, and a first polarization beam splitter (first beam combiner) 18. . The acousto-optic deflector is composed of an acousto-optic deflector (AOD), and the first beam combiner 18 is composed of a polarization beam splitter. The laser beam emitted from the laser light source 1 enters the acousto-optic deflector. It is assumed that the polarization direction of the incident laser beam is parallel to the paper surface of FIG. The control device 20 transmits a control signal sig to the acousto-optic deflector. During the period when the control signal sig is not input, the laser beam incident on the acousto-optic deflector travels straight and propagates along the first path p1. This state is referred to as a “first state”. During the period when the control signal sig is input, the laser beam incident on the acousto-optic deflector is diffracted and propagates along the second path p2. This state is referred to as a “second state”. In general, since the diffraction efficiency is not 100%, some leakage components are emitted to the first path p1 in the second state.

  The laser beam propagating through the first path p1 is reflected by the folding mirror 13. On the first path p1 between the folding mirror 13 and the first galvano scanner 31, the first polarization beam splitter 18 is arranged. The first polarization beam splitter 18 is arranged in such a posture that the laser beam propagating through the first path p1 becomes p-polarized light. For this reason, the laser beam propagating through the first path p 1 passes through the first polarization beam splitter 18 and enters the first galvano scanner 31.

  The laser beam propagating through the second path p <b> 2 is reflected by the folding mirror 12 and enters the half-wave plate 17. The half-wave plate 17 rotates the polarization direction of the laser beam by 90 °. That is, the polarization direction of the laser beam propagating through the half-wave plate 17 and propagating along the second path p2 is perpendicular to the paper surface.

  A part of the component of the laser beam that has passed through the half-wave plate 17 is transmitted through the first partial reflection mirror 14 and propagates along the second path p2, and the other component is transmitted through the first partial reflection mirror. 14 and propagates along the third path p3. The laser beam transmitted through the first partial reflection mirror 14 is incident on the second galvano scanner 32.

  The laser beam reflected by the first partial reflection mirror 14 and propagating along the third path p3 enters the first polarization beam splitter 18. The first polarization beam splitter 18 is arranged in such an attitude that the laser beam propagating through the third path p3 is reflected and merged with the laser beam propagating through the first path p1. The half-wave plate 17 may be disposed on either the second path p2 or the third path p3 from the acoustooptic deflector 11 to the first polarizing beam splitter 18.

  FIG. 2A shows the propagation path of the laser beam when the acoustooptic deflector 11 is in the first state, and FIG. 2B shows the propagation path of the laser beam when the acoustooptic deflector 11 is in the second state. FIG. 3 shows an example of a timing chart. The path of the laser beam incident on the acoustooptic deflector 11 is A, the path of the laser beam that has traveled straight through the acoustooptic deflector 11 is B, the path of the laser beam diffracted by the acoustooptic deflector 11 is C, and the first polarization A path that exits from the beam propagation optical system 10 via the beam splitter 18 is denoted as D, and a path that passes through the first partial reflection mirror 14 and exits from the beam propagation optical system 10 is denoted as E.

  As shown in FIG. 3, the pulse laser beam has a constant repetition frequency on the path incident on the acoustooptic deflector 11.

  As shown in FIG. 2A, when the acoustooptic deflector 11 is in the first state, the laser beam incident on the acoustooptic deflector 11 travels straight along and propagates along the path B. Thereafter, the light is reflected by the folding mirror 13 and passes through the polarization beam splitter 18. Thereby, the light is emitted from the beam propagation optical system 10 along the path D. Since the laser beam does not propagate along the path C, the laser beam is not emitted along the path E.

  As shown in FIG. 2B, when the acousto-optic deflector 11 is in the second state, most of the laser beam incident on the acousto-optic deflector 11, for example, about 90% of the component is diffracted and appears in the path C. The remaining leakage component, for example about 10%, appears in path B. The leakage component propagating along the path B is incident on the first polarization beam splitter 18. The polarization direction of the laser beam propagating along the path C is changed by 90 ° by the half-wave plate 17. A part of the laser beam transmitted through the half-wave plate 17 is transmitted through the first partial reflection mirror 14 and emitted from the beam propagation optical system 10 along the path E. The other components are reflected by the first partial reflection mirror 14, propagate along the third path p <b> 3, and enter the first polarization beam splitter 18. Since the laser beam propagating along the third path p3 is s-polarized with respect to the first polarization beam splitter 18, it is reflected by the first polarization beam splitter 18 and propagates along the path B. To join. The merged laser beam is emitted along the path D from the beam propagation optical system 10.

  If the reflectivity of the first partial reflection mirror 14 is set to 44%, the intensity of the laser beam emitted along the path D and the intensity of the laser beam emitted along the path E become substantially equal. . As described above, by adjusting the reflectance of the first partial reflection mirror 14 in accordance with the diffraction efficiency of the acoustooptic deflector 11, the intensities of the two laser beams emitted from the beam propagation optical system 10 are substantially reduced. Can be equal.

  In the first embodiment, the path of one laser beam out of two laser beams emitted from the beam propagation optical system 10 when the acoustooptic deflector 11 is in the second state is used for acoustooptic deflection. It can be made to coincide with the path of one laser beam emitted from the beam propagation optical system 10 when the device 11 is in the first state. Furthermore, in the first embodiment, when the acoustooptic deflector 11 is in the first state, the component leaking to the first path p1 can also be used effectively.

  In the first embodiment, since the first state and the second state are switched by the control signal sig applied to the acoustooptic deflector 11, the state can be switched instantaneously. More specifically, the state can be switched in a short time of 10 ns or less. Since the optical element is not replaced or moved when the state is switched, it is not necessary to readjust the optical axis.

  FIG. 4 shows a schematic view of a laser irradiation apparatus according to the second embodiment. Hereinafter, differences from the laser irradiation apparatus according to the first embodiment shown in FIG. 1 will be described.

  Another partial reflecting mirror 45 is further arranged on the second path p2 of the laser beam that has passed through the first partial reflecting mirror 14. The laser beam reflected by the partial reflection mirror 45 is reflected by the folding mirror 46 and emitted from the beam propagation optical system 10.

  When the acousto-optic deflector 11 is in the first state, one laser beam that has passed through the first polarization beam splitter 18 is emitted from the beam propagation optical system 10 as in the case of the first embodiment. . When the acousto-optic deflector is in the second state, the laser beam merged by the first polarization beam splitter 18, the laser beam transmitted through the partial reflection mirror 45, and the laser beam reflected by the folding mirror 46 A laser beam is emitted from the beam propagation optical system 10. In this manner, the state in which only one laser beam is emitted and the state in which three laser beams are emitted can be switched.

  By adjusting the reflectance of the first partial reflection mirror 14 and the reflectance of the second partial reflection mirror 45, the light intensities of the three laser beams can be made uniform.

  FIG. 5 shows a schematic diagram of a laser irradiation apparatus according to the third embodiment. Hereinafter, differences from the laser irradiation apparatus according to the first embodiment shown in FIG. 1 will be described.

  A second partial reflection mirror 51 is disposed on the first path p <b> 1 between the folding mirror 13 and the first polarization beam splitter 18. A part of the laser beam propagating along the first path p1 is reflected by the second partial reflecting mirror 52 and propagates along the fourth path p4. The laser beam propagating along the fourth path p4 is reflected by the folding mirror 52 and enters the second polarization beam splitter 60.

  A third partial reflection mirror 55 is disposed on the second path p <b> 2 between the half-wave plate 17 and the first partial reflection mirror 14. A part of the laser beam propagating along the second path p2 is reflected by the third partial reflecting mirror 55, propagates along the fifth path p5, and reflected by the folding mirror 56. A fourth partial reflection mirror 58 is disposed on the fifth path p5 after being reflected by the folding mirror 56. The fourth partial reflection mirror 58 reflects a part of the laser beam propagating along the fifth path p5 and propagates it along the sixth path p6.

  The laser beam propagating through the sixth path p6 enters the second polarization beam splitter 60. In the second polarizing beam splitter 60, the laser beam reflected by the folding mirror 52 and propagating through the fourth path p4 becomes p-polarized light, reflected by the fourth partial reflecting mirror 58, and propagated through the sixth path p6. The laser beam to be s-polarized is disposed. For this reason, the laser beam propagating through the sixth path p6 is reflected by the second polarization beam splitter 60 and merged with the laser beam propagating through the fourth path p4.

  When the acoustooptic deflector 11 is in the first state, a laser beam is emitted from the beam propagation optical system 10 along the first path p1 and the fourth path p4. By setting the reflectance of the second partial reflection mirror 51 to 50%, the two laser beams can have the same intensity. When the acoustooptic deflector 11 is in the second state, the laser beam is emitted from the beam propagation optical system 10 along the first path p1, the second path p2, the fourth path p4, and the fifth path p5. Emitted. When the diffraction efficiency of the acousto-optic deflector is 90%, the reflectance of the second partial reflection mirror 51 and the third partial reflection mirror 55 is 50%, and the first partial reflection mirror 14 and the fourth partial reflection mirror. If the reflectance of 58 is set to 44%, the intensity of the four laser beams can be made uniform.

  Thus, in the third embodiment, it is possible to switch between a state in which two laser beams are emitted and a state in which four laser beams are emitted.

  Next, a laser irradiation apparatus according to the fourth embodiment will be described with reference to FIGS. 6A and 6B.

  FIG. 6A shows a schematic diagram of the beam propagation optical system 10 of the laser irradiation apparatus according to the fourth embodiment. The beam propagation optical system 10 includes an electro-optic modulator 70, a first polarization beam splitter 71, a partial reflection mirror 77, and a second polarization beam splitter 75. The laser beam emitted from the laser light source 1 enters the electro-optic modulator 70. The laser beam emitted from the laser light source 1 is linearly polarized. It is assumed that the polarization direction is parallel to the paper surface of FIG. 6A. Under the control of the control device 20, the electro-optic modulator 70 can take either a first state in which the polarization direction of the laser beam is not changed or a second state in which the polarization direction is rotated by 90 °. 6A shows the path of the laser beam when the electro-optic modulator 70 is in the first state, and FIG. 6B shows the path of the laser beam when the electro-optic modulator 70 is in the second state.

  The laser beam transmitted through the electro-optic modulator 70 enters the first polarization beam splitter 71. When the electro-optic modulator 70 is in the first state, the first polarizing beam splitter 71 linearly moves the laser beam as shown in FIG. 6A, and when the electro-optic modulator 70 is in the second state, the first polarization beam splitter 71 is shown in FIG. 6B. As shown, the laser beam is arranged so as to reflect it.

  The laser beam that has traveled straight through the first polarization beam splitter 71 is reflected by the folding mirror 74, travels straight through the second polarization beam splitter 75, and is emitted from the beam propagation optical system 10.

  The laser beam reflected by the first polarization beam splitter 71 is branched into two laser beams by the partial reflection mirror 77. The laser beam transmitted through the partial reflection mirror 77 is emitted from the beam propagation optical system 10 as it is. The laser beam reflected by the partial reflection mirror 77 is reflected by the second polarization beam splitter 75 and emitted from the beam propagation optical system 10.

  The path of the laser beam transmitted through the second polarization beam splitter 75 when the electro-optic modulator 70 is in the first state, and the second polarization beam splitter when the electro-optic modulator 70 is in the second state. The attitude of the second polarization beam splitter 75 is adjusted so that the path of the laser beam reflected by 75 coincides.

  Also in the fourth embodiment, as in the first embodiment, the first state in which one laser beam is emitted from the beam propagation optical system 10 and the first state in which two laser beams are emitted. 2 state can be switched instantaneously. By setting the reflectance of the partial reflection mirror 77 to 50%, the intensity of the two laser beams can be made equal.

  Next, with reference to FIG. 7A to FIG. 7D, a method for drilling using the laser irradiation apparatus according to the first embodiment will be described. Even if the laser irradiation apparatus according to the fourth embodiment is used, processing can be performed by the same method.

  As shown in FIG. 7A, a workpiece 40 is prepared in which the machining points where holes are to be formed are arranged in a matrix. The workpiece 40 includes a base member made of a material that is relatively easily processed by a laser beam, and a surface layer made of a material that is relatively hard to process. The fact that the laser beam is easily processed means that the lower limit (threshold value) of the pulse energy density required for ablation is low. Examples of the processing object 40 include a printed wiring board in which a copper layer is formed on a resin layer. The workpiece 40 is placed on the XY stage 35 shown in FIG.

  As shown in FIG. 2A, the acousto-optic deflector 11 is set to the first state so that one pulse laser beam is emitted. In this state, the first galvano scanner 31 shown in FIG. 1 is driven while emitting a pulsed laser beam, thereby forming a hole in the surface layer of the work point 81a in the first row and exposing the underlying member. Let

  As shown in FIG. 7B, the XY stage 35 is driven to move the workpiece 40 in the row direction. The acoustooptic deflector 11 is maintained in the first state, and a hole is formed in the surface layer of the work point 81b in the second row to expose the base member.

  As shown in FIG. 7C, the first and second galvano scanners 31 and 32 are set while the acousto-optic deflector 11 is set to the second state and two laser beams are emitted from the beam propagation optical system 10. To work. Thus, holes are formed in the base member of the first row processed points 81a and the second row processed points 81b. Since the base member is formed of a material that is easier to process than the surface layer, a sufficient pulse energy density can be ensured even if the base member is branched into two laser beams.

  As shown in FIG. 7D, the workpiece 40 is moved to start machining the workpiece points 81c in the third row. The third row and fourth row processed points are processed in the same manner as the first row and second row processed points.

  In the above processing method, two rows are processed simultaneously in the step shown in FIG. 7C. 7B can be instantaneously shifted from the process of processing with one laser beam shown in FIG. 7B to the process of processing with two laser beams shown in FIG. 7C. For this reason, productivity can be improved. By moving the workpiece 40 from the first path p1 emitted from the beam propagation optical system 10 shown in FIG. 1 toward the second path p2 (from right to left in FIG. 1), processing is performed. Processing can be performed without returning the object 40. This method is particularly effective when processing is performed while moving the workpiece wound in a roll shape in one direction.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

It is the schematic of the laser irradiation apparatus by a 1st Example. (2A) is a schematic diagram showing a laser beam path when the AOD of the laser irradiation apparatus according to the first embodiment is in a first state, and (2B) is a laser when the AOD is in a second state. It is the schematic which shows the path | route of a beam. It is a timing chart of the laser irradiation apparatus by a 1st Example. It is the schematic of the laser irradiation apparatus by a 2nd Example. It is the schematic of the laser irradiation apparatus by a 3rd Example. It is the schematic of the laser irradiation apparatus by a 4th Example. It is a top view of the process target object in the middle stage which performs the process using the laser irradiation apparatus by a 1st Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 10 Beam propagation optical system 11 Acousto-optic deflector (beam path switching device)
12, 13 Folding mirror 14 First partial reflecting mirror (first beam splitter)
17 Half-wave plate 18 First polarization beam splitter (first beam combiner)
20 control device 31 first galvano scanner 32 second galvano scanner 33 first fθ lens 34 second fθ lens 35 XY stage 40 workpiece 45 other partial reflecting mirror 46 folding mirror 51 second partial reflecting mirror (Second beam splitter)
52 Folding mirror 55 Third partial reflecting mirror (third beam splitter)
56 Folding mirror 58 Fourth partial reflecting mirror (fourth beam splitter)
60 Second polarization beam splitter (second beam combiner)
81a, 81b, 81c Work point

Claims (6)

A beam path switch that switches between a first state in which a laser beam emitted from a laser light source is propagated to the first path and a second state in which the laser beam is propagated to the second path is switched by a control signal;
A first beam splitter for branching a part of the laser beam propagating through the second path into a third path and a remaining component propagating through the second path ;
A laser irradiation apparatus comprising: a first beam combiner that combines a laser beam propagating through the third path with a laser beam propagating through the first path. When the beam path switch is in the second state, the leakage component of the laser beam from the beam path switch propagates through the first path, and when in the first state, the second path the laser irradiation apparatus according to claim 1 having the property of leakage component of the laser beam does not propagate from the beam path switching device in the path. A beam path switch that switches between a first state in which a laser beam emitted from a laser light source is propagated to the first path and a second state in which the laser beam is propagated to the second path is switched by a control signal;
A first beam splitter for branching a part of the laser beam propagating through the second path into a third path;
A first beam combiner for combining a laser beam propagating through the third path with a laser beam propagating through the first path;
Have
When the beam path switch is in the second state, the leakage component of the laser beam from the beam path switch propagates through the first path, and when in the first state, the second path The path has a characteristic that the leakage component of the laser beam from the beam path switch does not propagate,
When the beam path switch is in the second state, the intensity of the laser beam after the leakage component propagating through the first path and the laser beam propagating through the third path are merged, the first of the second path after being branched by the beam splitter to be equal to the intensity of the laser beam propagating through said first beam splitter for branching ratio is adjusted Relais over tHE irradiation device. Furthermore, from said beam path switch to one of the second path and the third path until said first beam converging device, and the polarization direction control element to 90 ° turning the polarization direction of the laser beam is located ,
The laser irradiation apparatus according to claim 1, wherein the first beam combiner is a polarization beam splitter. A second beam splitter that branches a part of the laser beam propagating in the first path from the beam path switch to the first beam combiner into a fourth path;
A third beam splitter for branching a part of the laser beam propagating in the second path from the beam path switch to the first beam splitter into a fifth path;
A fourth beam splitter for branching a part of the laser beam propagating through the fifth path into a sixth path;
3. The laser irradiation apparatus according to claim 1, further comprising: a second beam combiner that combines the laser beam propagating through the fourth path with the laser beam propagating through the sixth path. Preparing a workpiece on which a surface layer made of a material in which holes are relatively difficult to be formed by a laser beam on a base member made of a material in which holes are relatively easily formed by a laser beam;
The beam path switch of the laser irradiation apparatus according to claim 1 is set to a first state, and a laser beam propagating through the first path is made incident on a first workpiece point on the workpiece. Removing the surface layer of the first workpiece point;
The beam path switch is maintained in the first state, a laser beam propagating through the first path is incident on a second workpiece point on the workpiece, and the second workpiece point is Removing the surface layer;
The beam path switching unit is set to the second state, and a laser beam propagating through the first path after being synthesized by the first beam combiner is incident on the first processing point at the same time. A laser beam propagating through the second path after being branched by the two beam splitters is incident on the second workpiece point to form holes in the base members of the first and second workpiece points. A laser processing method.

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