JP3604014B2 - Laser processing apparatus and processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing apparatus and a laser processing method, and more particularly to a laser processing apparatus and a laser processing method for processing by moving a laser irradiation position within a certain range on an object to be processed.
[0002]
[Prior art]
A laser drilling apparatus disclosed in Japanese Patent No. 3114533 will be described. The pulse laser beam emitted from the laser light source is split into two by a half mirror, one first pulse laser beam is incident on the first galvano scanner, and the other second pulse laser beam is incident on the second galvano scanner. To do. The first and second galvano scanners scan the first and second pulse laser beams in a two-dimensional direction, respectively. The scanned first and second pulse laser beams are incident on one fθ lens. The fθ lens converges the first and second pulse laser beams and makes them enter the object to be processed.
[0003]
Drilling can be performed by making a pulse laser beam incident on the object to be processed. By arranging two sets of galvano scanners for one expensive fθ lens, it is possible to reduce the processing time while suppressing an increase in apparatus cost.
[0004]
[Problems to be solved by the invention]
Conventionally, a CO ₂ gas laser in the infrared region has been used for drilling a copper foil. In the drilling method using a CO ₂ gas laser, the copper foil is thermally decomposed and sublimated by one shot irradiation. For this reason, the quality of the hole is likely to deteriorate due to heat. In addition, since the reflectance of copper in the wavelength region of the CO ₂ gas laser is high, the surface of the copper foil has to be roughened in order to increase the absorption rate of the laser beam.
[0005]
Attention has been focused on a technique for performing high-quality processing by eliminating a thermal influence by using a laser beam in the ultraviolet wavelength region. In order to process a copper foil using a laser beam in the ultraviolet wavelength region, it is necessary to set the pulse energy density on the surface of the copper foil to a threshold (about 10 to 20 J / cm ² ) or more necessary for the copper foil processing. is there. In order to shorten the processing time, when the laser beam is split into two by a half mirror, the pulse energy density is reduced to about half. For this reason, it becomes difficult to make the pulse energy density on the surface of the copper foil equal to or higher than the threshold value of the copper foil processing.
[0006]
An object of the present invention is to provide a laser processing apparatus and a processing method capable of maintaining a high pulse energy density on the surface of a workpiece and performing high-speed and high-quality processing.
[0007]
[Means for Solving the Problems]
A holding table for holding the object to be processed, a converging lens for converging the incident laser beam and causing the converged laser beam to enter the object to be processed held by the holding table, and scanning the incident laser beam A plurality of scanning devices, wherein the plurality of scanning devices are arranged so that laser beams scanned by each of the scanning devices are incident on the object to be processed through the converging lens, and the plurality of scanning devices include the one converging lens. A plurality of scanning devices that perform a scanning operation for moving the incident position of the laser beam on the workpiece under common control and external control, a laser light source that emits a laser beam, and an emission from the laser light source The laser beam incident on a part of the scanning devices selected from the plurality of scanning devices, and changing the incident scanning device according to time, and The laser processing apparatus is provided with a control device for controlling the 査 device.
[0008]
Drilling is performed when the laser beam is incident on the workpiece. Focusing on a certain time, the laser beam passes only through some of the scanning devices. For this reason, the operation of the scanning device can be performed during a period in which the laser beam does not pass. Since a plurality of scanning devices share one converging lens, an increase in the number of converging lenses can be avoided.
[0009]
According to another aspect of the present invention, a laser beam emitted from a laser light source is incident on a part of scanning devices selected from a plurality of scanning devices, and a laser beam whose propagation direction is controlled by the selected scanning device is obtained. A process of converging with a single converging lens shared by the plurality of scanning devices, causing the converged laser beam to enter the processing object, and processing the processing object; and a laser through the selected scanning device Operating a scanning device that is not selected so that a position on the workpiece that the laser beam enters through a scanning device that is not selected moves during a period in which the beam is incident on the workpiece; At least a part of the scanning devices are selected from the scanning devices that have not been selected, and the incident destination of the laser beam emitted from the laser light source is changed from the scanning device that has been selected so far. The laser beam whose propagation direction is controlled by the newly selected scanning device is converged by the converging lens, and the converged laser beam is incident on the workpiece to be processed. And a laser processing method.
[0010]
By operating the scanning device during a non-selected period, it is possible to effectively use the laser beam using another scanning device during the operation period of one scanning device. Since one converging lens is shared by a plurality of scanning devices, an increase in the number of converging lenses can be prevented.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic diagram of a laser processing apparatus according to an embodiment of the present invention. A laser light source 1 emits a pulsed laser beam 2. The laser light source 1 includes, for example, an Nd: YAG laser oscillator and a nonlinear optical element, and emits, for example, a third harmonic (wavelength 355 nm) of an Nd: YAG laser.
[0012]
The pulse laser beam 2 is incident on the sorting device 10. The sorting apparatus 10 includes a half-wave plate 11, an electro-optical element 12 that exhibits the Pockels effect, and a polarizing plate 13. The half-wave plate 11 converts the pulse laser beam 2 emitted from the laser light source 1 into linearly polarized light that becomes a P wave with respect to the polarizing plate 13. This P wave enters the electro-optic element 12.
[0013]
The electro-optic element 12 rotates the polarization axis of the pulse laser beam based on the control signal sig ₀ sent from the control device 40. When the electro-optic element 12 is not applied with a voltage, the incident P wave is emitted as it is. When the electro-optical element 12 is in a voltage application state, the electro-optical element 12 rotates the polarization axis of the incident pulse laser beam by 90 degrees. Accordingly, the pulse laser beam emitted from the electro-optical element 12 becomes an S wave with respect to the polarizing plate 13.
[0014]
The polarizing plate 13 transmits the P wave as it is and reflects the S wave. The P wave transmitted through the polarizing plate 13 becomes a pulsed laser beam pl ₁ propagating along the optical axis 20. The S wave reflected by the polarizing plate 13 becomes a pulsed laser beam pl ₂ that propagates along the other optical axis 30. The pulsed laser beam pl ₁ propagating along the optical axis 20 is reflected by the folding mirror 21 and enters the first scanning device 17. The pulsed laser beam pl ₂ propagating along the other optical axis 30 is incident on the second scanning device 35.
[0015]
The first scanning device 25 includes an X galvanometer mirror 25X and a Y galvanometer mirror 25Y. By rotating the two galvanometer mirrors 25X and 25Y, the incident laser beam can be scanned in a two-dimensional direction. The rotational movement operation of the galvanometer mirror is called a scanning operation. The galvanometer mirrors 25X and 25Y are controlled by a control signal sig ₁ input from the control device 40. The second scanning device 35 includes a Y galvanometer mirror 35X and a Y galvanometer mirror 35Y, and scans the incident laser beam in a two-dimensional direction. The galvanometer mirrors 35X and 35Y are controlled by a control signal sig ₂ input from the control device 40.
[0016]
The pulse laser beam scanned by the first scanning device 25 and the pulse laser beam scanned by the second scanning device 35 are incident on the same fθ lens 38. The fθ lens 38 converges the incident pulse laser beam. The converged laser beam is incident on the workpiece 50 placed on the XY table 39. Instead of the fθ lens 38, another converging lens may be used.
[0017]
FIG. 2A shows a plan view of the workpiece 50. A plurality of unit processing areas 51 arranged in a matrix are defined in the surface of the processing object 50. Each of the unit machining areas 51 is divided into a first area 51a and a second area 51b.
[0018]
The first scanning device 25 shown in FIG. 1 can move the incident position of the laser beam to an arbitrary position in the first region 51a. The second scanning device 35 can move the incident position of the laser beam to an arbitrary position in the second region 51b. By operating the first and second scanning devices 25 and 35, the laser beam can be incident on an arbitrary position in one unit processing region 51. When the processing of one unit processing region 51 is completed, the other unit processing region 51 can be processed by driving the XY stage 39 shown in FIG.
[0019]
FIG. 2B shows a cross-sectional view of the workpiece 50. The workpiece 50 has a three-layer structure in which, for example, copper foils 52 and 54 each having a thickness of 9 μm are adhered to both surfaces of a resin base film 53 having a thickness of 50 μm. By making a plurality of shots of the pulse laser beam incident, the through hole 55 penetrating the three layers can be formed.
[0020]
Next, with reference to FIG. 3, the control method of the sorting device 10 and the first and second scanning devices 25 and 35 will be described.
[0021]
FIG. 3 shows a timing chart of the control signals sig ₀ , sig ₁ , sig ₂ and the pulse laser beams pl ₁ , pl ₂ . Based on the control signal sig ₀ , in the first period T1 in which the electro-optical element 12 is in the no-voltage application state, the pulse laser beam that has passed through the electro-optical element 12 shown in FIG. The pulse laser beam pl ₁ along the axis 20 is output, and the pulse laser beam pl ₂ along the optical axis 30 is not output. For this reason, drilling is performed by the pulse laser beam that has passed through the first scanning device 25.
[0022]
During the first period T1, the control device 40 transmits a control signal sig ₂ to the second scanning device 35 where the pulse laser beam is not incident. Accordingly, the second scanning device 35 is controlled so that the incident pulse laser beam is incident on a desired position on the workpiece 50.
[0023]
In the second period T2 after the first period T1, the electro-optical element 12 is in a voltage application state by the control signal sig ₀ . Therefore, during the second period T2, the pulse laser beam pl ₁ is not output and the pulse laser beam pl ₂ is output. During the previous first period T1, the galvanometer mirrors 35X and 35Y of the second scanning device 35 are driven and the incident position of the pulse laser beam is adjusted. Drilling can be performed at the position.
[0024]
Further, during the second period T2, the control device 40 transmits a control signal sig ₁ to the first scanning device 25 where the pulse laser beam is not incident. Thereby, the galvanometer mirrors 25X and 25Y of the first scanning device 25 are controlled so that the pulse laser beam is incident on a desired position on the workpiece 50.
[0025]
By alternately repeating the first period T <b> 1 and the second period T <b> 2, holes can be formed at a plurality of desired positions on the workpiece 50.
[0026]
In the above embodiment, the energy of each pulse of the pulse laser beam emitted from the laser light source 1 reaches the workpiece 50 without being divided. For this reason, it is easy to maintain the pulse energy density on the surface of the workpiece 50 above the threshold value required for copper foil processing. In the above embodiment, since the two scanning devices 25 and 35 share one fθ lens 38, an increase in device cost can be suppressed.
[0027]
Further, in the above-described embodiment, drilling is performed by the pulse laser beam that has passed through the second scanning device 35 during the second period T2 during which the first scanning device 25 is driven. Further, during the first period T <b> 1 during which the second scanning device 35 is driven, drilling is performed by the pulse laser beam that has passed through the first scanning device 25. For this reason, all the pulses of the pulse laser beam emitted from the laser light source 1 are effectively used for drilling.
[0028]
Consider a case in which a through hole 55 having a diameter of 50 μm is formed in the workpiece 50 shown in FIG. 2B using a laser light source having a pulse repetition frequency of 10 kHz and a third harmonic power of 10 W. The number of shots required to form a hole penetrating each of the 9 μm thick copper foils 52 and 54 is about 10. The number of shots required to form a hole penetrating the base film 53 having a thickness of 50 μm is about 5. For this reason, the through-hole 55 can be formed by performing irradiation of 25 shots.
[0029]
The time required to irradiate 25 shots of a pulsed laser beam with a pulse frequency of 10 kHz is 2.5 ms. That is, each of the periods T1 and T2 shown in FIG. 3 is 2.5 ms. The time required to drive the galvanometer mirror to move the incident position of the laser beam is about 1 ms. For this reason, the galvanometer mirror can be driven during the periods T1 and T2 to complete the preparation for laser beam irradiation.
[0030]
On the other hand, when processing is performed using only one scanning device, a time of 2.5 ms + 1 ms = 3.5 ms is required to form one through hole. Rather than dividing the pulse energy of the pulse laser beam as in the embodiment, the pulse energy density is reduced by distributing a plurality of pulses arranged on the time axis to a plurality of scanning devices on the time axis. No processing time can be shortened.
[0031]
In the above embodiment, an Nd: YAG laser is used as a laser light source, and the third harmonic is used for processing. However, other laser light sources that can punch holes in a processing target may be used. For example, harmonics of Nd: YLF laser or Nd: YVO ₄ laser may be used. In order to form fine and high-quality holes, it is preferable to use a laser beam in the ultraviolet region with a wavelength of 400 nm or less.
[0032]
In the above embodiment, the case where the through hole is formed in the laminated structure of the copper foil and the resin layer has been described, but also when the through hole is formed in the laminated structure of the metal foil other than copper and the resin layer, The laser processing apparatus according to the embodiment can be applied. Further, the present invention is not limited to the through hole, and can be applied to the case where a recess that does not penetrate is formed.
[0033]
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.
[0034]
【The invention's effect】
As described above, according to the present invention, the apparatus cost can be suppressed by sharing one converging lens among a plurality of scanning devices. In addition, by using a plurality of scanning devices and performing a scanning operation of another scanning device during a period in which the laser beam passes through a part of the scanning devices, processing with the laser beam is continued even during the scanning operation. It can be carried out. Thereby, it becomes possible to shorten processing time.
[Brief description of the drawings]
FIG. 1 is a schematic view of a laser processing apparatus according to an embodiment of the present invention.
2A and 2B are a plan view and a cross-sectional view of a workpiece.
FIG. 3 is a timing chart of a pulse laser beam and various control signals of a workpiece according to an embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser light source 2 Pulse laser beam 10 Sorting device 11 Half-wave plate 12 Electro-optic element 13 Polarizing plate 20 and 30 Optical axis 21 Folding mirror 25 and 35 Scanning device 38 f (theta) lens 39 XY table 40 Control apparatus 50 Processing target object 51 Unit processing Regions 52 and 54 Copper foil 53 Resin base film 55 Through hole

Claims (6)

A holding table for holding the workpiece;
One converging lens for converging an incident laser beam and causing the converged laser beam to be incident on a workpiece held by the holding table;
A plurality of scanning devices for scanning an incident laser beam, wherein the plurality of scanning devices are arranged such that a laser beam scanned by each of the scanning devices is incident on the object to be processed through the converging lens. A plurality of scanning devices that share the one converging lens and perform a scanning operation to move an incident position of the laser beam on the workpiece under external control;
A laser light source for emitting a laser beam;
A distribution device that causes a laser beam emitted from the laser light source to be incident on a part of the scanning devices selected from the plurality of scanning devices, and changes the scanning device of the incident destination according to time;
A laser processing apparatus having a control device for controlling the scanning device; The laser processing apparatus according to claim 1, wherein the control device controls the scanning device so that the scanning device to which the laser beam is not incident from the sorting device performs a scanning operation. The laser light source emits a pulsed laser beam;
The distribution device causes each of a plurality of pulses arranged on a time axis of a pulse laser beam emitted from the laser light source to enter one scanning device selected from the plurality of scanning devices. The laser processing apparatus as described in. The scanning device is divided into two groups, and the control device causes the second group of scanning devices to perform a scanning operation during a period in which the laser beam is incident on the first group of scanning devices. 4. The laser processing apparatus according to claim 1, wherein the first group of scanning devices performs a scanning operation during a period in which the laser beam is incident on the second group of scanning devices. The sorting device is
An electro-optic element that receives a laser beam emitted from the laser light source and changes a polarization direction of the laser beam according to an applied voltage;
The laser processing apparatus according to claim 1, further comprising: a polarizing plate on which a laser beam whose polarization direction is controlled by the electro-optic element is incident and which changes a traveling direction of the incident laser beam depending on the polarization direction. A laser beam emitted from a laser light source is incident on a part of scanning devices selected from a plurality of scanning devices, and a laser beam whose propagation direction is controlled by the selected scanning devices is shared by the plurality of scanning devices. A process of processing the object to be processed by causing the focused laser beam to be incident on the object to be processed;
The position on the workpiece that the laser beam passes through the non-selected scanning device is selected to move during a period in which the laser beam is incident on the workpiece through the selected scanning device. Operating a scanning device that is not,
Selecting at least a part of the scanning devices from the scanning devices that have not been selected, and switching the incident destination of the laser beam emitted from the laser light source from the scanning device that has been selected to the newly selected scanning device; A laser processing including a step of converging a laser beam, the propagation direction of which is controlled by a newly selected scanning device, with the converging lens, and causing the converged laser beam to enter the processing target and processing the processing target. Method.

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