JP2003275885A - Laser beam machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make openings of various sizes in a short time on a covering layer of an object to be worked. <P>SOLUTION: The object to be worked on which a covering layer of a material different from that of a surface layer part of a base member is formed is prepared on a surface of the base member. A first laser beam has properties of transmitting through a covering layer, reflected by a boundary between the covering layer and the base member and peeling the covering layer of a reflection position off the base member. The first laser beam is made incident on the object to be worked from the surface of the covering layer, part of the covering layer is peeled off the base member and a first opening is formed. The higher harmonic component is separated from the laser beam including a first component of the same wavelength as that of the first laser beam and a higher harmonic component of the first wavelength. The separated higher harmonic component is made incident on the object to be worked through the surface of the covering layer of the object to be worked and a second opening is formed in the covering layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method for irradiating a processing object having a coating layer with a laser beam to make a hole in the coating layer.

[0002]

2. Description of the Related Art There is known a method of forming a hole in a coating layer formed on a base member by condensing a pulsed laser beam in the ultraviolet wavelength range. If the pulse energy of the laser beam is set to a size such that the coating layer is ablated and the base member is not ablated, the through hole can be formed in the coating layer with almost no damage to the base member.

[0003]

However, when an attempt is made to open a large-area hole by the above-mentioned ablation process,
Even if a hole having a diameter of about 50 μm is made in a resin layer having a thickness of 50 μm, a pulse laser beam of about 100 shots is required, and it takes a long time for processing.

An object of the present invention is to provide a coating layer for an object to be processed,
It is an object of the present invention to provide a laser processing method capable of effectively making a hole in a short time. Another object of the present invention is to provide a laser processing method for making holes of various sizes in a coating layer of a processing target.

[0005]

According to one aspect of the present invention, there is prepared an object to be processed in which a coating layer made of a material different from the material of the surface layer of the base member is formed on the surface of the base member. And a first laser beam having a property of transmitting the coating layer, reflecting at the interface between the coating layer and the base member, and separating the coating layer at the reflection position from the base member. From the surface of the layer is incident on the object to be processed,
A step of peeling a part of the coating layer from the base member to form a first hole; a component of a first wavelength that is the same as the wavelength of the first laser beam and a harmonic of the first wavelength. Separating the higher harmonic component from the laser beam containing the component, causing the separated higher harmonic component to enter the object to be processed from the surface of the coating layer of the object to be processed, and forming a second hole in the coating layer. A laser processing method having the same is provided.

According to the laser processing method, a large hole can be formed by the laser beam of the first wavelength and a small hole can be formed by the harmonic component of the first wavelength.
It is possible to form holes of various sizes in a short time.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the first of the present invention.
FIG. 3 is a schematic view of a laser processing apparatus used in the laser processing method according to the example of FIG. A pulsed laser beam, for example, a fundamental wave (wavelength 1064 nm) of an Nd: YAG laser is emitted from the all-solid-state laser oscillator 1 with a pulse energy of 200 μJ. A nonlinear crystal (SHG, Second Harmonics Generator) for generating a second harmonic wave of this pulsed laser beam 2
Pass through. This makes it possible to generate the second harmonic (532 nm) of the Nd: YAG laser, but not all the incident fundamental waves are converted to the second harmonic.
From the non-linear crystal (SHG) for generating the second harmonic,
A mixed wave including two wavelength components different from the double harmonic is emitted.

The emitted mixed wave is incident on the third harmonic generating non-linear crystal (THG, Third Harmonics Generator) 3 to generate a third harmonic of the Nd: YAG laser. The frequency is the sum frequency of the fundamental wave and the second harmonic contained in the mixed wave emitted from the nonlinear crystal (SHG) for generating the second harmonic. A fundamental wave always remains in the laser beam emitted from the third-order harmonic generation nonlinear crystal (THG). That is, from the non-linear crystal (THG) for generating the third harmonic, the fundamental wave (wavelength 1064 nm) and the second harmonic (wavelength 532 nm)
A laser beam including three wavelength components different from the double harmonic (wavelength 355 nm) is emitted.

This laser beam is incident on the dichroic mirror 4. The dichroic mirror 4 splits the fundamental wave and the triple harmonic having different wavelengths into optical paths A,
Guide to optical path B. At this time, the second harmonic passes through the dichroic mirror 4 and travels to the optical path A together with the fundamental wave.

The pulse energy of the pulse laser beam of the fundamental wave that follows the optical path A is, for example, 0.9 mJ. The pulsed laser beam of the fundamental wave has, for example, a mask 5a for shaping the beam cross section into a circular shape, a reflection mirror 6a for reflecting the fundamental wave and transmitting a second harmonic, and a galvano scanner 7.
a, focusing the laser beam on the processing object 10a f
The object to be processed 10a mounted on the stage 9 is irradiated through the θ lens 8a. The processing object 10a is, for example, a multilayer substrate. The galvano scanner 7a is configured to include a pair of swingable reflecting mirrors and emits a laser beam with two beams.
Scan at high speed in the dimension. The reflection mirror 6a is
Most of the incident second harmonic wave is transmitted, but about 4% is reflected. Therefore, the two reflection mirrors 6
By the a, 0.16% of the second harmonic passed through the dichroic mirror 4 is applied to the processing object 10a, but the participation in the second harmonic processing can be ignored.

FIG. 2A is a sectional view of a multilayer substrate processed by the laser processing method according to the first embodiment. A supporting material (reinforcing material), for example, a supporting substrate 13 formed of an epoxy resin reinforced with glass fiber, a metal layer 12 as a base member made of a metallic material such as copper, a dielectric material such as an epoxy resin. The coating layer 11 is laminated in this order from the bottom. The thickness of the resin coating layer 11 is, for example, 50 μm.

Examples of the dielectric material of the resin coating layer 11 include epoxy resin, polyimide resin, phenol resin, PTFE (polytetrafluoroethylene), BT resin, BCB (benzocyclobutene) and the like.

Examples of the metal material of the metal layer 12 include copper, aluminum, gold, silver, palladium, nickel, titanium, tungsten, platinum, molybdenum, and the like.
The supporting substrate 13 is formed of a supporting material (reinforcing material) such as glass fiber, as well as a dielectric material reinforced with alumina fiber, aramid fiber, Kepler or the like.

From the top surface of the resin coating layer 11, Nd: YAG
Inject the fundamental wave of the laser. The fundamental wave of the Nd: YAG laser has a property of being transmitted through the resin coating layer 11 with almost no absorption and being mostly reflected by the metal layer 12. The laser beam causes a high pressure state at the interface between the resin coating layer 11 and the metal layer 12, and the pressure causes the resin coating layer 1 to have a high pressure.
A hole is formed in the resin coating layer 11 by inducing peeling of the resin coating layer 11 from the metal layer 12. This phenomenon is called a "lifting phenomenon", and processing performed by utilizing the "lifting phenomenon" is called a "lifting processing". One of the features of the lifting process is that it can make larger holes than the ablation process.

FIG. 2B shows a multilayer substrate shown in FIG. 2A after one shot of 0.9 mJ / pulse fundamental wave of Nd: YAG laser (wavelength 1064 nm) is incident on the multilayer substrate. FIG. Holes 11 a are formed in the resin coating layer 11. When the hole 11a has a circular shape, for example, its diameter can be set to 90 μm. Further, a beam of several shots is irradiated so as to widen the hole, and it is possible to open a hole having an arbitrary diameter exceeding 90 μm with a small number of shots and with almost no damage to the metal layer 12. If the pulse energy is set to 3 mJ, for example, a circular hole having a diameter of 1 mm can be made with one shot.

By the operation of the galvano scanner 7a, the incident position of the laser beam of the fundamental wave moves on the surface of the multi-layer substrate 10a, and the resin coating layer 11 has a diameter of 90 μm at a predetermined position.
Holes of a predetermined size of m or more are drilled one after another. These are holes formed by the lifting phenomenon.

A pulsed laser beam, which is converted into a tripled harmonic by a nonlinear crystal (THG) 3 for generating a tripled wave and is branched from a fundamental wave by a dichroic mirror 4, travels along an optical path B. The pulse energy of this laser beam is, for example, 1
It is 00 μJ / pulse. The laser beam of the third harmonic, for example, has a mask 5b for shaping the beam cross section into a circular shape, a reflecting mirror 6b, a galvano scanner 7b for scanning the laser beam at a high speed, and a laser beam to be focused on the object 10b. The object to be processed 10b mounted on the stage 9 is irradiated through the fθ lens 8b.
The galvano scanner 7b includes a pair of swingable reflecting mirrors, and scans a laser beam in a two-dimensional direction at high speed.

The object 10b to be processed is, for example, a multilayer substrate having a coating layer formed on the surface of an underlayer. It does not have to be the same as the processing object 10a. Here, the object 10b is processed such that the base layer is, for example, an aluminum layer,
A multi-layer substrate in which the coating layer is, for example, a polyimide resin layer having a thickness of 10 μm is used, and the third harmonic that has followed the optical path B is incident from the top surface of the polyimide resin layer.

Holes are formed in the polyimide resin layer by ablation. The operation of the galvano scanner 7b irradiates a number of shots of beam so as to deepen or widen one hole, and for example, a hole of a predetermined size penetrating the polyimide resin layer is opened. For example, when the shape of the hole formed is circular, the diameter is, for example, 25 μm or more and less than 90 μm. Then, similarly, a hole having a predetermined size is opened at a predetermined different position.

Irradiation with a triple harmonic of pulse energy of 100 μJ / pulse, for example, a diameter of 25 μm or more and 90 μm
Drill less than a circular hole. A circular hole having a diameter of 90 μm or more has a large number of shots, which is impractical in ablation processing.

The coating layer of one multi-layer substrate can be processed so as to have a circular hole having a diameter of 25 μm or more and less than 90 μm and a hole having a diameter of 90 μm or more, for example. This will be described below in the second embodiment.

Referring to FIG. The laser processing apparatus used in the laser processing method according to the second embodiment is the same as the laser processing apparatus used in the first embodiment. The stage 9 includes a moving mechanism that moves the object to be processed placed on the stage 9. The object to be processed is the resin coating layer 11 made of an epoxy resin having a thickness of 50 μm on the surface of the metal layer 12 made of, for example, copper, which is also used in the first embodiment.
2 is a multilayer substrate shown in FIG.

The fundamental wave (wavelength 1064 nm) of the Nd: YAG laser traveling along the optical path A enters from the surface of the resin coating layer 11 of the multilayer substrate. The fundamental wave is galvano scanner 7
The resin coating layer 11 is scanned at a high speed with a, and the resin coating layer 11 is scanned at predetermined positions within a region that can be scanned by the galvano scanner 7a. It is a lifting process. A circular hole with a diameter of 90 μm can be processed with one shot of the fundamental wave. Further, a beam of several shots may be irradiated so as to widen the hole to form a hole having an arbitrary hole diameter exceeding 90 μm.

When the processing within the scannable area by the galvano scanner 7a is completed, the multi-layer substrate is moved by the stage 9 and the other areas are processed. By repeating the scanning by the galvano scanner 7a and the movement of the multi-layer substrate by the stage 9, perforations are made at all positions on the multi-layer substrate where it is desired to make a circular hole having a diameter of 90 μm or more, for example.

The multilayer substrate perforated by the fundamental wave is conveyed to the processing target area of the galvano scanner 7b. Optical path B
3rd harmonic of Nd: YAG laser (wavelength 3
55 nm) is incident on the multi-layer substrate perforated with the fundamental wave to form a hole in the resin coating layer 11 at a position different from the hole processed with the fundamental wave. Some shots of the laser beam
By the operation of the galvano scanner 7b, irradiation is performed so as to widen or deepen one hole, and a hole having a predetermined size is formed at a predetermined position. When the perforations in the scannable area by the galvano scanner 7b are completed, the multi-layer substrate is moved by the stage 9 and the other areas are processed. By repeating the scanning by the galvano scanner 7b and the movement of the multi-layer substrate by the stage 9, for example, perforations are made at all positions on the multi-layer substrate where it is desired to make circular holes having a diameter of 25 μm or more and less than 90 μm.

In this way, the coating layer of one multi-layer substrate is
For example, a circular hole having a diameter of 25 μm or more and less than 90 μm,
It can also be processed to have a circular hole having a diameter of 90 μm or more.

In addition, in the second embodiment, the galvano scanner 7b is irradiated with triple harmonics in the scannable region to form a circular hole having a diameter of 25 μm or more and less than 90 μm on the multilayer substrate, and at the same time, the galvano scanner 7a is used. In the scannable area, the fundamental wave is irradiated to form a circular hole having a diameter of 90 μm or more on another multilayer substrate. Therefore, the work can be speeded up.

In the first and second embodiments,
In many cases, rather than lifting using the fundamental wave,
The ablation process using the 3rd harmonic will require a larger number of shots of the laser beam to be irradiated. In this case, after the processing by the fundamental wave is completed in the scanning area of the galvano scanner 7a, the galvano scanner 7a
The galvano scanner is adjusted so that the laser beam of the fundamental wave does not enter the multilayer substrate until the processing by the third harmonic in the scanning region of b is completed. Further, for example, a shutter that blocks the beam is used as the dichroic mirror 4
It may be provided on the optical path A between the substrate and the multilayer substrate.

As described above, in the first and second embodiments,
The third harmonic (355 nm) of the Nd: YAG laser was used for the ablation process, but the second harmonic (532 nm) was used.
Alternatively, it is possible to use a fourth harmonic (266 nm). When using the 2nd harmonic, 3 of the processing equipment of Fig. 1 is used.
The non-linear crystal (THG) 3 for generating a harmonic wave is unnecessary. When using the 4th harmonic, a nonlinear crystal (T
HG) 3 instead of 4th harmonic generation nonlinear crystal (FH
G, Forth Harmonics Generator) may be used. The harmonic component has a pulse width of 1 ps or more and 1 μs
A pulsed laser beam in the wavelength range of ultraviolet rays (wavelength 4 to 400 nm) of less than or less than 1 μm and a pulsed laser beam in the wavelength region of green color (wavelength 492 to 577 nm) having a pulse width of 1 ps or more and less than 1 ns can be used. In this range,
Good processing. In the case of a pulsed laser beam in the wavelength range of ultraviolet rays, if the pulse width is in the range of 1 μs or more, a long heat input time will have an adverse effect, so that high quality processing is difficult. In the case of a pulsed laser beam in the green wavelength region, when the pulse width is in the range of 1 ns or more, the resin coating layer has a high transmittance and copper is melted, so that high quality processing is difficult.

Although the Nd: YAG laser is used as the all-solid-state laser oscillator, an Nd: YLF laser may be used. A beam scanning optical system using a polygon mirror may be used instead of the galvano scanner.

Further, here, the diameter is 25 μm or more and 90 μm.
A circular hole with a diameter of less than m is processed with a triple harmonic, and a circular hole with a diameter of 90 μm or more is processed with a fundamental wave. The diameter of the hole formed by lifting is the pulse energy of the laser beam to be irradiated, the object to be processed. Since it can be decided according to the size of the beam spot focused on the surface, the characteristics of the processing object, etc., we will use the fundamental wave that is the lifting process as much as possible, and for the processing of small diameter holes that is impossible with the lifting process. If the triple harmonic is used, the total processing time can be minimized.

In the first and second embodiments,
Although a circular hole is processed, the shape of the hole may not be circular. Generally, processing by ablation is not suitable for making large holes. Therefore, conventionally, a large hole is processed by, for example, a CO ₂ laser, and a small hole is processed by, for example, N 2.
Using harmonics of an all-solid-state laser such as a d: YAG laser,
It was processed by ablation. In addition, when processing by ablation, the beam of the fundamental wave included when harmonics are generated is not usually used. The laser processing methods shown in the first and second embodiments make it possible to efficiently make large holes and small holes by using, for example, only an all-solid-state laser oscillator. In addition, it is possible to effectively use the fundamental wave that was not used in the past and that is included when harmonics are generated.

The present invention has been described above with reference to the embodiments, but the present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0034]

As described above, according to the present invention,
It is possible to make holes of various sizes in the coating layer of the object to be processed in a short time.

[Brief description of drawings]

FIG. 1 is a schematic view of a laser processing apparatus used in a laser processing method according to first and second embodiments of the present invention.

FIG. 2A is a cross-sectional view of a multilayer substrate processed by a laser processing method according to the first and second embodiments, and FIG.
FIG. 6 is a cross-sectional view of a multi-layered board that has been punched by the laser processing method according to the first and second embodiments.

[Explanation of symbols]

A, B optical path 1 All-solid-state laser oscillator Nonlinear crystal for generating 2nd harmonic (SHG) 3 Nonlinear crystal (THG) for 3rd harmonic generation 4 dichroic mirror 5a, b mask 6a, b Reflective mirror 7a, b Galvano scanner 8a, b fθ lens 9 stages 10a, b Object to be processed 11 Resin coating layer 11a hole 12 metal layers 13 support substrate

Claims (3)

[Claims] 1. A step of preparing an object to be processed in which a coating layer made of a material different from a material of a surface layer portion of the underlying member is formed on the surface of the underlying member; A first laser beam having a property of reflecting at an interface between a layer and the base member and separating the coating layer at a reflection position from the base member is incident on the object to be processed from the surface of the coating layer, A step of separating a part of the coating layer from the base member to form a first hole; a component of a first wavelength that is the same as the wavelength of the first laser beam and a harmonic of the first wavelength. Separating the higher harmonic component from the laser beam containing the component, causing the separated higher harmonic component to enter the object to be processed from the surface of the coating layer of the object to be processed, and forming a second hole in the coating layer. A laser processing method having. 2. The laser processing method according to claim 1, wherein the first hole and the second hole are formed at different positions of one processing object. 3. The pulsed laser beam in the ultraviolet wavelength range having a pulse width of 1 ps or more and less than 1 μs, or the pulsed laser beam in the green wavelength range having a pulse width of 1 ps or more and less than 1 ns. Alternatively, the laser processing method described in 2.