JP2004098121A - Method and apparatus for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for laser beam machining which realize shortening of machining time of a work to be machined. <P>SOLUTION: A pulse laser beam propagating along a first optical path is divided into a laser beam propagating along a second optical path and a laser beam propagating along a third optical path. The pulse laser beam propagating along the second optical path is made incident on a first work to be machined and the work is machined. At least one of the pulses of the pulse laser beam propagating along the third optical path is divided into a plurality of pulses on a time base and made incident on a second work to be machined and the work is machined. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a processing method and a processing apparatus using a laser beam.
[0002]
[Prior art]
A conventional processing method of a substrate having two metal layers (two-metal substrate) will be described with reference to FIGS. FIG. 3A is a cross-sectional view schematically showing a two-metal substrate. For example, a two-metal substrate in which a copper layer 52 is disposed on the surface of a resin layer 51 made of polyimide and an electrode layer 53 formed of copper inside is processed with an ultraviolet pulse laser beam 54. The thickness of the copper layer 52 is, for example, 9 to 18 μm, and in the two metal substrate, it is 9 μm. The thickness of the portion of the resin layer 51 sandwiched between the electrode layer 53 and the copper layer 52 is, for example, 20 to 50 μm, and 50 μm in this two-metal substrate. The ultraviolet pulse laser beam is emitted with an output of 12 W and a frequency of 12 kHz, for example. The pulse energy per pulse is 1 mJ / pulse.
[0003]
As shown in FIG. 3B, the copper layer 52 is irradiated with an ultraviolet pulse laser beam 54, and a hole 52a for exposing the resin layer 51 is formed. In order to make the hole 52 a in the copper layer 52, an energy density of about 10 to 20 J / cm ² is required on the surface of the copper layer 52. Here, irradiation is performed with an energy density of 20 J / cm ² . When the energy density of the laser beam applied to the surface of the copper layer 52 is 20 J / cm ² , the etching rate per pulse of the copper layer 52 is about 1.5 μm / pulse. Therefore, in the case of the copper layer 52 having a thickness of 9 μm, the holes 52a can be formed by irradiating 6 shots of the pulse laser beam. The processing time required to form the hole 52a is about 0.5 ms.
[0004]
As shown in FIG. 3 (C), following the drilling of the hole 52a, the pulse energy of the ultraviolet pulse laser beam 54 is reduced by, for example, an attenuator, and a hole 51a reaching the electrode layer 53 is drilled in the resin layer 51. The pulse energy per pulse is attenuated to 0.05 mJ / pulse, for example. In order to make the hole 51 a in the resin layer 51, an energy density of about 1 to ² J / cm ² is required on the surface of the resin layer 51. Here, irradiation is performed with an energy density of 1 J / cm ² . When the energy density of the laser beam applied to the surface of the resin layer 51 is 1 J / cm ² , the etching rate per pulse of the resin layer 52 is about 1 μm / pulse. Therefore, in the case of the resin layer 52 having a thickness of 50 μm, the hole 51a can be formed by irradiating the pulse laser beam of 50 shots. The processing time required to form the hole 51a is about 4.2 ms. The time required to continuously open the hole 51a and the hole 52a is about 4.7 ms.
[0005]
For example, instead of adjusting the pulse energy with an attenuator, the output and frequency of the laser oscillator that emits the ultraviolet pulse laser beam may be changed between the processing of the copper layer 52 and the processing of the resin layer 51.
[0006]
When a hole is made in the copper layer 52, for example, a pulse laser beam is emitted at an output of 12 W and a frequency of 12 kHz. The pulse energy per pulse is 1 mJ / pulse. When the hole 52a is formed in the 9 μm thick copper layer 52 with a 6-shot pulse laser beam, the required processing time is about 0.5 ms.
[0007]
Next, a hole 51 a is made in the resin layer 51. For example, an ultraviolet pulse laser beam is emitted with an output of 3 W, a frequency of 60 kHz, and a pulse width of 100 ns. The pulse energy per pulse is 0.05 mJ / pulse. When the hole 51a is opened in the 50 μm thick resin layer 51 with a 50-shot pulse laser beam, the required processing time is about 0.83 ms. The time required to continuously open the hole 51a and the hole 52a is about 1.33 ms.
[0008]
Furthermore, high quality processing is difficult with conventional methods.
[0009]
This will be described with reference to FIG. Since the processing of the copper layer 52 and the resin layer 51 is continuously performed, the heat transmitted to the resin layer 51 during the processing of the copper layer 52 and the heat remaining in the copper layer 52 during the processing of the resin layer 51 are affected, thereby causing an undercut. Defects such as 51b are likely to occur. Therefore, the resin layer 51 is actually perforated, as in the hole 51c, the resin layer 51 immediately below the periphery of the hole 52a is damaged and the side surface has a bulge. Further, simply waiting for the heat at the time of processing the copper layer 52 to dissipate increases the time required for drilling.
[0010]
[Problems to be solved by the invention]
The objective of this invention is providing the laser processing method and laser processing apparatus which can shorten the time which processes a process target object.
[0011]
[Means for Solving the Problems]
According to one aspect of the present invention, a pulse laser beam propagating along the first optical path is changed into a pulse laser beam propagating along the second optical path and a pulse laser beam propagating along the third optical path. A step of branching, a step of processing a pulse laser beam propagating along the second optical path to be incident on the first object to be processed, and at least a pulse laser beam propagating along the third optical path There is provided a laser processing method including a step of dividing one pulse into a plurality of pulses on the time axis and causing the pulse to enter a second object to be processed.
[0012]
According to this laser processing method, it is possible to shorten the time for processing the object to be processed.
[0013]
According to another aspect of the present invention, a laser light source that emits a pulse laser beam, and the pulse laser beam emitted from the laser light source is branched into a first pulse laser beam and a second pulse laser beam. And a first optical system that causes the first pulse laser beam to be incident on a workpiece in the first processing region, and the second pulse laser beam is incident on the first pulse laser beam. A laser having a second optical system that divides at least one pulse into a plurality of pulses on a time axis and makes a pulsed laser beam divided into the plurality of pulses incident on an object to be processed in the second processing region. A processing apparatus is provided.
[0014]
When this laser processing apparatus is used, it is possible to perform processing in the second processing region simultaneously with processing in the first processing region. The first optical system and the second optical system branch the laser beam or reduce the second pulse laser beam so as to reduce the difference in processing time between the first and second processing regions. The processing time can be shortened by dividing.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic view of a laser processing apparatus used in a laser processing method according to an embodiment of the present invention. The laser light source 1 is, for example, an Nd: YAG laser including a wavelength conversion unit. From the Nd: YAG laser including the wavelength conversion unit, for example, a third harmonic (wavelength 355 nm) of the Nd: YAG laser is emitted. For example, the output is 12 W, the frequency is 6 kHz, the pulse width is 100 ns, and the pulse energy is 2 mJ / pulse.
[0016]
The emitted laser beam is shaped into, for example, a circle by the mask 2 having a through hole, and is incident on the beam splitter 3. The beam splitter 3 splits the incident pulse laser beam into a pulse laser beam traveling on the optical path A and a pulse laser beam traveling on the optical path B. The laser beams traveling in the two optical paths are branched so that, for example, the pulse energies are equal. That is, the pulse energy per pulse of the laser beam traveling along the optical path A and the optical path B is both about 1 mJ / pulse.
[0017]
The pulse laser beam traveling in the optical path A is incident on the galvano scanner 4. The galvano scanner 4 includes a pair of swingable reflecting mirrors, and scans the pulse laser beam in a two-dimensional direction. The pulsed laser beam scanned by the galvano scanner 4 passes through the fθ lens 5 and enters the substrate 6 that is the object to be processed. The substrate 6 is placed on the movable surface of the XY stage 14. The fθ lens 5 images the through hole of the mask 2 on the substrate 6.
[0018]
The pulsed laser beam traveling along the optical path B is incident on the pulse chopper 10. The pulse chopper 10 forms a plurality of pulse laser beams having a shorter pulse width from the incident one-shot pulse laser beam. This will be described in detail later.
[0019]
A pulse laser beam having a short pulse width formed by the pulse chopper 10 is reflected by a reflection mirror 11 arranged as necessary, and enters a substrate 7 as a processing object through a galvano scanner 12 and an fθ lens 13. To do. The substrate 7 is placed on the movable surface of the XY stage 14. The actions of the galvano scanner 12 and the fθ lens 13 are the same as those of the galvano scanner 4 and the fθ lens 5 arranged in the optical path A, respectively.
[0020]
The board | substrate 6 and the board | substrate 7 are 2 metal substrates which showed the cross section in FIG. 3 (A) in description of a prior art, for example. The laser beam traveling along the optical path A is incident on the copper layer 52 of the substrate 6 and opens a hole 52 a that exposes the surface of the resin layer 51. In order to open the hole 52a, as described above, a 6-shot pulse laser beam is required, and the time required for the drilling process is about 0.5 ms. The substrate 6 with the hole 52 a formed in the copper layer 52 is moved to the laser beam processing region traveling on the optical path B by the XY stage 14, and the hole 51 a reaching the electrode layer 53 is formed in the resin layer 51.
[0021]
Processing with a laser beam traveling in the optical path B will be described in detail. A hole 52a is formed in the copper layer 52 of the substrate 6 by the laser beam traveling on the optical path A, and at the same time, the substrate 7 is processed in the processing region of the laser beam traveling on the optical path B. The substrate 7 is a substrate in which a hole 52 a that exposes the surface of the resin layer 51 is already formed in the copper layer 52 by a laser beam traveling in the optical path A.
[0022]
The pulse chopper 10 will be described with reference to FIG. The pulse chopper 10 includes, for example, an EOM (electric optical modulator), and forms a plurality of pulse laser beams having a shorter pulse width from the incident one-shot pulse laser beam as described above.
[0023]
FIG. 2A is a schematic graph showing the relationship between the pulse width and the pulse energy density of one shot pulse laser beam before entering the pulse chopper 10. A laser beam having a pulse width of 100 ns enters the pulse chopper 10.
[0024]
FIG. 2B is a schematic graph showing the relationship between the pulse width and the pulse energy density of a plurality of pulse laser beams emitted from the pulse chopper 10. The hatched portions indicate a plurality of pulse laser beams emitted from the pulse chopper 10. 10 shots of a pulse laser beam having a pulse width of 5 ns are formed from one shot laser beam having a pulse width of 100 ns and emitted from the pulse chopper 10. The pulse energy of each shot to be emitted is 0.05 mJ / pulse.
[0025]
A pulse laser beam having a pulse width of 5 ns emitted from the pulse chopper 10 enters the resin layer 51 of the substrate 7. In order to form the hole 51a reaching the electrode layer 53 in the resin layer 51, as described above, a pulse laser beam of 50 shots is necessary, and the time required for drilling is about 0.83 ms.
[0026]
The time required for drilling the copper layer 52 of the substrate 6 by the laser beam traveling on the optical path A was about 0.5 ms. The time required for drilling the resin layer 51 of the substrate 7 by the laser beam traveling on the optical path B is about 0.83 ms. Since these processes are performed at the same time, the time required to process the laser beam into the optical path A and the optical path B and perform the process with each of the branched laser beams is 0.83 ms. This is shorter than the processing time required to perform the same processing by the conventional laser processing method.
[0027]
Further, when the laser processing method according to the present embodiment is used, the processing quality can be improved. The substrate 6 is moved to the processing region of the laser beam traveling on the optical path B by the XY stage 14 after the hole 52a is made in the copper layer 52 by the laser beam traveling on the optical path A. For this reason, the heat at the time of processing the hole 52a is dissipated during this time, and the vicinity of the hole 52a is cooled. Therefore, defects such as the undercut 51b are less likely to occur.
[0028]
Further, in the processing of the resin layer 51, when the energy of the irradiated laser beam is the same, it is possible to perform high quality processing by shortening the pulse width. Therefore, by using a pulse laser beam having a pulse width of 5 ns formed using the pulse chopper 10, high-quality drilling can be performed.
[0029]
In this embodiment, the splitting of the pulse laser beam by the beam splitter 3 is performed so that the pulse energy of the laser beam traveling along the optical paths A and B is equally divided. Further, the pulse chopper 10 obtained a 10-shot pulse laser beam from the 1-shot laser beam. The ratio of the pulse energy splitting of the laser beam by the beam splitter 3 and the number of pulse divisions by the pulse chopper 10 are such that the time required for processing performed by the laser beam traveling in the optical path A and that in the optical path B are substantially equal. Preferably it is determined. Of the time for forming the hole penetrating the copper layer 52 and the time for forming the hole penetrating the resin layer 51, the beam splitter 3 is set so that the shorter time is 50% or more of the longer time. It is preferable to divide the pulse laser beam with or to split the pulse laser beam with the pulse chopper 10. For example, as in this embodiment, if the energy density required to open the hole 51a in the resin layer 51 is 1/10 to 1/20 times that required to open the hole 52a in the copper layer 52, The ratio of beam energy branching may be 1: 1 and the number of pulse divisions may be 10.
[0030]
Furthermore, the laser beam used in the laser processing method according to the embodiment is not limited to the third harmonic of the Nd: YAG laser, and may be a fundamental wave or a second harmonic. A CO ₂ laser or the like can also be used.
[0031]
Here, an example of a mask imaging optical system that forms an image of the through hole of the mask 2 on the surface of the substrate 6 has been described, but this is a condensing optical system that focuses the pulsed laser beam on the substrate 6 using a focusing lens. It may be.
[0032]
As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0033]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a laser processing method and a laser processing apparatus capable of reducing the time for processing a workpiece.
[Brief description of the drawings]
FIG. 1 is a schematic view of a laser processing apparatus used in a laser processing method according to an embodiment of the present invention.
FIGS. 2A and 2B are schematic graphs showing a relationship between a pulse width and a pulse energy density of a pulse laser beam. FIGS. 3A to 3D are views of a substrate. It is sectional drawing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser light source 2 Mask 3 Beam splitter 4 Galvano scanner 5 f (theta) lens 6 Board | substrate 7 Substrate 10 Pulse chopper 11 Reflection mirror 12 Galvano scanner 13 f (theta) lens 14 XY stage 51 Resin layer 51a, c hole 51b Undercut 52 Copper layer 52a Hole 53 Electrode Layer 54 Ultraviolet pulsed laser beam

Claims (6)

Branching the pulse laser beam propagating along the first optical path into a pulse laser beam propagating along the second optical path and a pulse laser beam propagating along the third optical path;
A step of causing a pulse laser beam propagating along the second optical path to enter the first object to be processed;
A laser processing method including a step of dividing at least one pulse of a pulsed laser beam propagating along the third optical path into a plurality of pulses on the time axis and causing the laser beam to enter a second object to be processed. The first object to be processed has a resin member and a metal film in close contact with the surface of the resin member, and the second object to be processed is in close contact with the surface of the resin member and the resin member. And a step of processing the first object to be processed forms a hole penetrating the metal film in the metal film of the first object to be processed. The process of processing a said 2nd processing object including a process includes the process of forming a hole in the resin member exposed to the bottom face of the hole which penetrates the metal film of this 2nd processing object. The laser processing method as described in. Of the time for forming the hole penetrating the metal film of the first object to be processed and the time for forming the hole penetrating the resin member of the second object to be processed, the longer time is the first time. A laser beam propagating along the first optical path so that the second time is 50% or more of the first time, where the shorter time is the second time. The laser processing method according to claim 2, wherein the pulse laser beam that is branched or propagated along the third optical path is divided. A laser light source for emitting a pulsed laser beam;
The pulse laser beam emitted from the laser light source is branched into a first pulse laser beam and a second pulse laser beam, and the first pulse laser beam is applied to a processing object in the first processing region. A first optical system for incidence;
The second pulse laser beam is incident, at least one pulse of the second pulse laser beam is divided into a plurality of pulses on a time axis, and the pulse laser beam divided into the plurality of pulses is A laser processing apparatus comprising: a second optical system that is incident on a processing target in a processing region. The laser processing apparatus according to claim 4, wherein the first optical system is capable of changing a pulse energy ratio between the first pulse laser beam and the second pulse laser beam. 6. The laser processing apparatus according to claim 4, wherein the second optical system can change the number of divisions for dividing the pulse of the second pulse laser beam. 7.

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