WO2013094025A1

WO2013094025A1 - Laser processing method

Info

Publication number: WO2013094025A1
Application number: PCT/JP2011/079539
Authority: WO
Inventors: 裕本木; 俊博森
Original assignee: 三菱電機株式会社
Priority date: 2011-12-20
Filing date: 2011-12-20
Publication date: 2013-06-27
Also published as: KR20130086388A; JP5100917B1; JPWO2013094025A1

Abstract

A laser processing method, including: a first machining step in which a laser light, that forms a beam cross-section having a first shape and forms upon an object to be machined a first irradiation area (21) corresponding to the beam cross-section having the first shape, is sequentially irradiated over the entirety of an excavation area (24); and a second machining step in which a laser light, that forms a beam cross-section having a second shape smaller than the first shape and forms upon the object to be machined a second irradiation area (22) corresponding to the beam cross-section having the second shape, is sequentially irradiated on the excavation area (24). In the first machining step, the laser light forming the first irradiation area (21) is sequentially irradiated so as to form an overlapping area (23) wherein sections in the first irradiation area (21) overlap each other. In the second machining step, the laser light forming the second irradiation area (22) is sequentially irradiated such that the second irradiation area (22) is included in an area in the excavation area (24) other than the overlapping area (23).

Description

Laser processing method

The present invention relates to a laser processing method for drilling a workpiece by laser light irradiation.

Drilling with a laser processing machine is applied to the formation of blind holes by drilling until reaching a desired depth without penetrating the workpiece. For example, in a printed wiring board including a surface resin layer and an inner copper foil layer, a blind hole may be formed by excavation from the resin layer to the copper foil layer. Copper is regarded as one of highly reflective materials that reflect laser light with high efficiency. When the laser light reaches the copper foil layer through excavation of the resin layer, the laser light is reflected by the copper foil layer, so that the progress of the laser processing beyond that is stopped. When the copper foil layer is exposed to the entire excavation area, the progress of the laser processing is stopped when the copper foil layer is exposed. In this case, a sufficient number of shots of laser light can be irradiated to perform uniform processing up to the copper foil layer.

In recent years, in the processing of printed wiring boards, there are an increasing number of cases where a blind hole having a wide bottom surface is formed in an area where a copper foil layer is formed. In this case, even if the copper foil layer is exposed by excavation of the resin layer, laser processing can proceed around the copper foil layer, making it difficult to form a blind hole having a uniform depth. When excavating a region wider than the beam cross section of the laser beam, laser processing is performed while moving the laser beam irradiation region relative to the workpiece. In this case, useless unevenness may be caused by a portion where the laser light irradiation regions in a plurality of shots overlap and a portion where they do not overlap. For example, Patent Document 1 proposes a technique of superimposing irradiation regions of laser light whose energy density distribution is controlled in order to suppress the occurrence of unevenness due to overlapping of laser light.

Japanese Patent Laid-Open No. 11-320156

When using a laser beam whose energy density is attenuated from the center of the beam cross section toward the periphery, in order to equalize the energy received on the workpiece, it is half of the width of the beam cross section. The laser beam is irradiated every time the relative movement is performed at the pitch. In this case, the relative movement of the laser light is performed for the entire excavation area so that the irradiation areas overlap in two consecutive shots. In order to enable uniform processing, it is necessary to strictly adjust the energy distribution of the laser light and the amount of overlapping of the laser light irradiation regions. The laser processing machine requires a special optical system for producing laser light having a desired energy distribution.

In the technique of Patent Document 1, a laser beam having a rectangular beam cross section that is inclined so that each side is inclined with respect to the scanning direction of the laser beam is used. When the workpiece is viewed in plan, a part of the irradiation area corresponding to the rectangular corner portion continuously remains on the outer edge of the excavation area. In order to obtain an excavation area having a straight side as an outer edge, additional work for shaping the outer edge of the excavation area is required. If the beam cross-section is further reduced in order to allow it to be regarded as a straight line even if the rectangular corner portion remains, the number of shots required for processing is further increased.

The present invention has been made in view of the above, and obtains a laser processing method capable of processing an excavation region wider than the beam cross section of the laser beam by reducing unevenness and making the depth uniform and efficiently. For the purpose.

In order to solve the above-described problems and achieve the object, the present invention sequentially irradiates the excavation area of a workpiece with laser light having a small beam cross section with respect to the excavation area, thereby processing the excavation area. A laser processing method, wherein a laser beam forming a first irradiation region corresponding to the beam cross-section of the first shape is formed on the workpiece with a beam cross-section of a first shape. The first processing step of sequentially irradiating the entire surface of the first and second beam sections smaller than the first shape, and a beam section corresponding to the second shape on the workpiece. A second processing step of sequentially irradiating the excavation region with laser light forming two irradiation regions, and in the first processing step, a part of the first irradiation regions overlap each other. Said first irradiation so as to form In the second processing step, the second irradiation region is formed so that the second irradiation region is included in a region other than the overlapping region in the excavation region. It is characterized by sequentially irradiating laser beams.

In the laser processing method according to the present invention, a first processing step of sequentially irradiating the entire excavation region with the laser light while overlapping a part of the irradiation region, and a second of sequentially irradiating the laser beam to the region other than the overlap region. The processing steps are performed. Generation of unevenness is suppressed by setting a region other than the overlapping region in which a part of the first irradiation region is overlapped as the second irradiation region. The distribution of the energy density of the laser light is arbitrary without adjustment, and the adjustment of the overlapping amount of the irradiation area of the laser light and the special optical system according to the energy distribution are not required. An excavation area having a straight side as an outer edge can be obtained without additional work for shaping the outer edge of the excavation area. As a result, the excavation area wider than the beam cross section of the laser beam can be processed efficiently by reducing the unevenness and making the depth uniform and efficiently.

FIG. 1 is a diagram showing a schematic configuration of a laser processing machine to which a laser processing method according to an embodiment of the present invention is applied. FIG. 2 is a diagram for explaining the irradiation region in the first processing step and the irradiation region in the second processing step. FIG. 3 is a schematic diagram for explaining the relationship between the first irradiation region and the second irradiation region and the state in which the workpiece is excavated. FIG. 4 is a diagram for explaining an example of the relationship between the position of the first irradiation region and the position of the second irradiation region. FIG. 5 is a diagram illustrating an example of the relationship between the position of the first irradiation region and the position of the second irradiation region.

Hereinafter, embodiments of the laser processing method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram showing a schematic configuration of a laser processing machine to which a laser processing method according to an embodiment of the present invention is applied. The laser processing machine 100 is an apparatus that performs laser processing on the workpiece 3 by irradiating the workpiece 3 with laser light L (pulse laser light).

The workpiece 3 is, for example, a printed wiring board including a surface resin layer and an inner copper foil layer. The laser processing machine 100 processes, for example, a surface resin layer. In the laser processing method of the present embodiment, any material may be processed as the workpiece 3.

The laser oscillator 1 emits a beam-shaped laser beam L. The beam shaping unit 10 shapes the beam cross section of the laser light L. The galvano scanner 11 rotates the galvanometer mirror 13. The galvanometer mirror 13 reflects the laser light L from the beam shaping unit 10. The galvanometer mirror 13 changes the traveling direction of the laser light L by rotating.

The galvano scanner 12 rotates the galvanometer mirror 14. The galvanometer mirror 14 reflects the laser light L from the galvanometer mirror 13. The galvanometer mirror 14 changes the traveling direction of the laser light L by rotating. The galvanometer mirrors 13 and 14 move the irradiation region of the laser beam L in the XY directions on the workpiece 3.

The fθ lens 15 is a condensing lens having telecentricity. The fθ lens 15 aligns the direction of the chief ray of the laser light L in the Z direction perpendicular to the XY plane. The XY table 16 is placed on the workpiece 3 and moves in the XY plane by driving an X-axis motor and a Y-axis motor (both not shown). Thereby, the XY table 16 moves the workpiece 3 in the X direction and the Y direction.

The processing control device 2 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The processing control device 2 controls the entire laser processing machine 100. The machining control device 2 performs NC (Numerical Control) control of the laser oscillator 1, the

galvano scanners

11 and 12, and the XY table 16 in accordance with the machining program.

The laser beam machine 100 forms a blind hole in the workpiece 3 by performing excavation until it reaches a desired depth without penetrating the workpiece 3. The laser processing machine 100 processes the excavation area by sequentially irradiating the laser beam L while moving the irradiation area in the excavation area of the workpiece 3. The excavation area is an area to be excavated by the laser beam L as a whole.

The laser processing machine 100 processes the excavation area of the workpiece 3 through the first processing step and the second processing step. In the first processing step, the laser processing machine 100 sequentially irradiates the entire excavation region with laser light having a first-shaped beam cross section. The first shape is, for example, a square. The first shape is smaller than the excavation area. In the first processing step, the laser processing machine 100 applies, for example, a mask having a first shape opening as the beam shaping unit 10.

In the second processing step, the laser processing machine 100 sequentially irradiates the excavation area with laser light having a second-shaped beam cross section. The second shape is smaller than the excavation area and smaller than the second shape. The second shape is, for example, a square. In the second processing step, the laser processing machine 100 applies, for example, a mask having a second shape opening as the beam shaping unit 10. In addition to the mask, the beam shaping unit 10 may be any optical element that can change the shape of the beam cross section of the laser light L to the first shape and the second shape.

FIG. 2 is a diagram for explaining the irradiation region in the first processing step and the irradiation region in the second processing step. FIG. 3 is a schematic diagram for explaining the relationship between the first irradiation region and the second irradiation region and the state in which the workpiece is excavated. The laser processing machine 100 may perform either the first processing step or the second processing step first.

In the first processing step, the laser beam L forms the first irradiation region 21 on the workpiece 3. The first irradiation region 21 corresponds to a beam cross section of the first shape. Due to the transfer limit when the image of the first shape, which is the opening of the mask, is transferred onto the workpiece 3, the first irradiation region 21 has a shape with rounded corners. The first irradiation area 21 is smaller than the excavation area 24.

In the first processing step, the laser processing machine 100 sequentially irradiates the entire excavation region 24 with the laser light L so as to form an overlapping region 23 in which parts of the first irradiation region 21 overlap each other. For example, the laser processing machine 100 sequentially moves the position of the laser beam L so that two first irradiation regions 21 in the X direction and two Y irradiation directions are formed with respect to the excavation region 24 having a shape close to a square. Let

In this case, a part of the first irradiation areas 21 adjacent in the X direction and a part of the first irradiation areas 21 adjacent in the Y direction constitute the overlapping area 23, respectively. The overlapping region 23 has a cross shape with the center of the excavation region 24 as an intersection in the XY plane.

In the first processing step, the workpiece 3 is dug deeply in the overlapping region 23 in the first irradiation region 21. In the overlapping region 23, the intersection portion where the four first irradiation regions 21 overlap is a superposition of a rounded corner portion of each first irradiation region 21, and thus other portions of the overlapping region 23. Compared to this, excavation is unlikely to progress greatly. On the other hand, excavation progresses greatly in the overlapping region 23 as compared with the portion other than the overlapping region 23 in the first irradiation region 21.

In the second processing step, the laser beam L forms the second irradiation region 22 on the workpiece 3. The second irradiation region 22 corresponds to a beam cross section having a second shape. Similar to the first irradiation region 21, the second irradiation region 22 has a rounded corner at a square due to the transfer limit when transferring the second shape image, which is the opening of the mask, onto the workpiece 3. It becomes a shape. The second irradiation area 22 is smaller than the excavation area 24 and smaller than the first irradiation area 21.

In the second processing step, the laser processing machine 100 sequentially irradiates the laser light L such that the second irradiation region 22 is included in the region other than the overlapping region 23 in the excavation region 24. Of the excavation area 24, the area other than the overlapping area 23 is divided into two in the X direction and two in the Y direction by the cross-shaped overlapping area 23. The laser beam machine 100 sequentially moves the position of the laser beam L so that the second irradiation region 22 matches each of the four regions. An interval corresponding to the width of the overlapping region 23 is provided between the second irradiation regions 22 adjacent in the X direction and between the second irradiation regions 22 adjacent in the Y direction.

In the second machining step, the workpiece 3 is dug in a portion other than the overlapping region 23. In the second processing step, the laser processing machine 100 excavates a depth corresponding to the difference between the depth of the overlapping region 23 and the depth of the portion other than the overlapping region 23 in the first processing step. The laser beam machine 100 excavates the second irradiation area 22 until it reaches the depth of the overlapping area 23. The laser beam machine 100 forms a blind hole in the workpiece 3 in which the entire excavation region 24 has a uniform depth by the first and second machining steps.

The laser processing machine 100 uses the laser beam L having the same energy in the first processing step and the second processing step, for example. In the first processing step, the laser processing machine 100 irradiates the entire excavation region 24 with the laser light L by a total of four shots, once for each of the four regions partially overlapping each other. In the second processing step, the laser processing machine 100 irradiates the laser light L by four shots, once for each of four regions that are spaced from each other in the excavation region 24.

In the second processing step, the laser processing machine 100 may irradiate each region with the laser beam L by a plurality of shots. The laser processing machine 100 sets the energy of the laser beam L in the second processing step to be smaller than the energy of the laser beam L in the first processing step. The laser processing machine 100 may appropriately adjust the number of shots and energy of the laser light L according to the finished state required for the blind hole obtained by the first processing step and the second processing step.

The laser processing method according to the present embodiment includes a first processing step in which parts of the first irradiation region 21 are overlapped with each other, and a second processing step in which the second irradiation region 22 is made to coincide with other than the overlapping region 23. Thus, the occurrence of unevenness in the excavation region 24 is suppressed. For the laser beam L, the laser beam L may be shaped in the beam cross section in the first processing step and the second processing step, and no special adjustment of the energy distribution is necessary.

According to the laser processing method according to the present embodiment, it is possible to obtain the excavation region 24 having a straight side as the outer edge without performing additional processing for shaping the outer edge of the excavation region 24. As a result, the excavation region 24 wider than the beam cross section of the laser light L can be processed efficiently by reducing the unevenness and making the depth uniform.

4 and 5 are diagrams for explaining an example of the relationship between the position of the first irradiation region and the position of the second irradiation region. For example, in the example illustrated in FIG. 4, the laser processing machine 100 includes one of the first irradiation regions 21 in the first processing step and one of the second irradiation regions 22 in the second processing step. Then, the center positions are matched.

In this example, the laser processing machine 100 can use a common coordinate as a target on which the laser beam L is incident in the first processing step and the second processing step. Thereby, the laser beam machine 100 can facilitate control.

In the example shown in FIG. 5, the laser processing machine 100 includes one of the first irradiation regions 21 in the first processing step and one of the second irradiation regions 22 in the second processing step. A part of the outer edge of the second irradiation region 22 is made to coincide with a portion of the first irradiation region 21 that constitutes the outer edge of the excavation region 24. Two sides in a direction perpendicular to each other in a substantially square formed by the first irradiation region 21 and two sides in a direction perpendicular to each other in a substantially square formed by the second irradiation region 22 are at the outer edge of the excavation region 24. Match.

In this example, the laser processing machine 100 matches the boundary of the region where excavation is performed in the first processing step and the boundary of the region where excavation is performed in the second processing step at the outer edge of the excavation region 24. Thereby, the laser beam machine 100 can reduce the occurrence of irregularities in the vicinity of the outer edge of the excavation region 24. Further, the laser processing machine 100 can form a tapered surface or the like on the outer edge of the excavation region 24.

The laser processing machine 100 determines the position of the first irradiation region 21 and the position of the second irradiation region 22 according to the shape required for the blind hole obtained by the first processing step and the second processing step. You may adjust suitably.

In the laser processing method of the present embodiment, a square is adopted as the first shape and the second shape for the substantially square excavation region 24, so that the second irradiation region 22 is provided in a region other than the overlapping region 23. Can be matched. By applying a shape similar to the shape of the excavation region 24 as the first shape and the second shape, the width occupied by the overlapping region 23 can be set to the minimum necessary in both the X direction and the Y direction.

The first shape and the second shape are not limited to a square shape, and can be appropriately modified. The first shape and the second shape may be rectangular, for example. In the laser processing method of the present embodiment, for the rectangular excavation region 24, the second irradiation region 22 is formed in a region other than the overlapping region 23 by adopting a rectangle as the first shape and the second shape. Can be matched. By adopting a rectangle as the first shape and the second shape, it is possible to obtain the excavation region 24 having a straight side as an outer edge.

The laser processing method according to the present invention is useful for processing for excavating a region larger than the beam cross section, and is suitable for, for example, drilling a printed wiring board, counterbore processing with a large diameter, and the like.

DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 Processing control apparatus 3 Workpiece 10

Beam shaping part

11, 12

Galvano scanner

13, 14 Galvano mirror 15 f (theta) lens 16 XY table 21 1st irradiation area 22 2nd irradiation area 23 Overlapping area 24 Excavation area 100 Laser processing machine L Laser light

Claims

A laser processing method of sequentially irradiating a laser beam having a small beam cross section with respect to the excavation region to the excavation region of a workpiece, and processing the excavation region,
A first cross section of a beam having a first shape is formed, and a laser beam forming a first irradiation region corresponding to the beam cross section of the first shape is sequentially irradiated on the entire workpiece. 1 processing step;
A laser beam forming a second irradiation region corresponding to the beam cross section of the second shape on the workpiece, the beam cross section having a second shape smaller than the first shape is formed on the workpiece. A second processing step of sequentially irradiating the
In the first processing step, a laser beam that forms the first irradiation region is sequentially irradiated so as to form an overlapping region in which parts of the first irradiation region overlap each other,
In the second processing step, the laser beam forming the second irradiation region is sequentially irradiated so that the second irradiation region is included in a region other than the overlapping region in the excavation region. Laser processing method.
2. The laser processing method according to claim 1, wherein both the first shape and the second shape are rectangular.
3. The laser processing method according to claim 1, wherein a center position of the second irradiation region is made to coincide with a center position of the first irradiation region.
3. The laser processing method according to claim 1, wherein a part of the outer edge of the second irradiation region is made to coincide with a portion of the first irradiation region that constitutes the outer edge of the excavation region.