TW201332691A - Method and apparatus of laser cutting by varying laser focus conditions - Google Patents

Abstract

The invention relates to a method and an apparatus of laser cutting. The apparatus includes a laser head, a movable platform for carrying a workpiece, an optical system and a control unit. The optical system is configured to adjust the focal length of a laser beam emitted from the laser head. When the workpiece is moved by the platform, the control unit controls output energy and the focal point of the laser beam with the optical system so as to form a plurality of breaking points along a waveform curve on a predetermined cutting surface inside the workpiece. In this way, the workpiece can be easily cut along the predetermined cutting surface defined by these breaking points.

Description

Variable focus laser cutting method and device

The present invention relates to a laser cutting device and method for cutting hard and brittle materials, such as germanium wafers, glass, quartz, ceramics, etc., and more particularly to a laser breaking point that uses varying focus to form different depths to Its splitting.

Generally, laser cutting is irradiated with laser light of a wavelength that can be absorbed by a workpiece material, and the workpiece is cracked from the surface cut portion by absorbing laser light. However, because of the large heat affected zone (Heat Affected Zone), in addition to adversely affecting the processing quality, material properties change around the processing area. Therefore, in the case of the surface of the workpiece, the surrounding area other than the cutting line of the workpiece may also be thermally melted or destroyed, and the processing precision is limited.

The conventional method for preventing the surface of the workpiece from melting can be referred to Taiwan Patent No. I250060, which uses a pulsed laser with a high peak power density (higher than 1×108 W/cm 2 ) to collect light at a target processing position inside the workpiece. It produces nonlinear multi-photon absorption, because the action time is extremely short (less than 1μ, or even less than 1ns), the energy is too late to diffuse, so only the inside of the workpiece (concentration point) forms a thunder. The cracking point or the modified area is shot, and the surface of the workpiece is not hot melted.

Furthermore, the above patent mentions a conventional laser cutting method as shown in the fifth figure, which uses a laser beam L to be laterally distributed inside the workpiece and in a straight line along a cutting path 2 on the surface of the workpiece 1. Arranged laser damage points 3, however, these break points are not easy to break the workpiece, and it is often necessary to perform a cooling operation immediately after the cutting operation to cause the workpiece to split from the break points and when cooling When the thermal shock generated by the operation is too large, the surface of the workpiece may be unintentionally cracked. This unnecessary cracking will affect the components on the workpiece (such as a semiconductor wafer, a liquid crystal display device or an electrode pattern). ) causing damage, resulting in inaccurate processing accuracy.

In order to improve the cutting precision, Taiwan Patent No. I250060 further refers to the improved laser cutting method as shown in the sixth figure, which firstly forms the first row of laser damage points 3a at the bottom of the workpiece by the same method as above, after which A second row of laser damage points 3b is formed at the top thereof, so that only a small force is applied to cut the workpiece along the cracks between the break points 3a, 3b (seventh figure). The face is split. However, if the workpiece material itself is difficult to cut (or has a large thickness), a third row of laser damage points 3c may be formed inside the workpiece, as shown in the eighth figure, so that the workpiece is more easily cut from the cut. The cracks open, but the continuous processing of the back and forth makes the process more time consuming and complicated.

The present invention provides a laser cutting processing method and apparatus capable of performing high-precision cutting quickly and efficiently.

In detail, a laser cutting method of the present invention mainly uses a laser beam to form a plurality of damage points arranged along a waveform or a sawtooth on a predetermined cut surface inside a workpiece, and then The stress naturally generated (or additional cooling or bending) causes the workpiece to break along the predetermined cut surface. Compared to the laser damage points of the dot matrix arrangement in the prior art, the laser damage point of the present invention is a waveform curve or a jagged arrangement, allowing the laser processing to achieve a sufficiently good number of laser damage points. Cracking effect to improve processing efficiency.

In addition, during laser cutting, the peak power density and pulse width of the focus of the laser beam are controlled to at least an extent sufficient to cause nonlinear multiphoton absorption inside the workpiece to form the lasers. Break the point. Since the photochemical processing mechanism of nonlinear multiphoton absorption has extremely low heat-affected zone and high-resolution processing characteristics, the surface of the workpiece is not thermally melted, and the splitting effect is excellent.

In order to achieve the above laser cutting method, the laser cutting device of the present invention comprises a laser light source, a moving platform, an optical system and a control unit. The laser source is used to excite a laser beam. The mobile platform is used to transfer a workpiece. The optical system is used to adjust the focal length of the laser beam. The control unit is configured to control the optical system to change the focus position of the laser beam and the output of the laser light source during the movement of the workpiece by the moving platform, so that the laser beam of the laser source is A predetermined cut surface inside the workpiece forms a plurality of break points arranged along a wave curve or a zigzag shape.

Preferably, the optical system comprises a polygon mirror and at least one focusing lens. The polygon mirror is disposed between the laser light source and the focusing lens, and the polygon mirror can rotate with its long axis as an axis, so that the polygon mirror of the polygon mirror rotates the laser emitted by the laser source The beam is reflected to the focusing lens. The focusing lens is configured to focus the laser beam reflected by the polygon mirror into the workpiece to form the damage points. In this way, the optical system can change the focal length of the laser beam back and forth while rotating the polygon mirror.

Other inventive aspects and more detailed technical and functional descriptions of the present invention are disclosed in the following description.

The first through third figures show a preferred embodiment of the laser cutting apparatus 100 of the present invention. The laser cutting device 100 is mainly used for cutting hard and brittle materials, such as workpieces such as tantalum wafers, glass, quartz, and ceramics, to be broken along a predetermined cut surface 80. The laser cutting apparatus 100 includes a laser light source 4, a moving platform 5, an optical system 6, and a control unit 7 (third diagram). The mobile platform 5 is for transferring a workpiece 8 . The incident direction of the laser beam excited by the laser light source 4 is perpendicular to the surface of the workpiece 8, that is, the angle θ with the moving direction of the moving platform 5 is 90°, as shown in the second figure. However, the angle θ between the incident direction of the laser beam and the moving direction of the moving platform may be other angles so that the laser beam is incident from the surface of the workpiece in an inclined manner. However, regardless of the angle from which the light is incident on the surface of the workpiece, the incident direction of the laser beam is zero with respect to the predetermined cut surface 80 of the workpiece 8.

The optical system 6 is used to adjust the laser beam excited by the laser light source 4 to focus on different positions inside the workpiece 8. The control unit 7 is connected to the laser light source 4, the moving platform 5 and the optical system 6.

While the moving platform 5 laterally moves the workpiece 8, the control unit 7 controls the optical system 6 to change the output of the laser beam and the focus position back and forth so that the laser beam is inside the workpiece 8 A plurality of break points 81 are formed on the cut surface 80 at different depths and arranged along a wavy curve or zigzag. Preferably, the control unit 7 controls the peak power density and the pulse width of the focus of the laser beam to be at least sufficient to cause nonlinear multiphoton absorption inside the workpiece 8 to form the damage points, thereby avoiding the workpiece. 8 surface hot melt, improve processing accuracy.

The optical system 6 includes a rotary polygon mirror 61 and at least one focusing lens 62 in order to form a complex curve 81 of a waveform curve or a zigzag arrangement. The polygon mirror 61 is disposed between the laser light source 4 and the focus lens 62, and the polygon mirror 61 can rotate with its long axis as an axis to rotate the plurality of mirrors 610 of the polygon mirror 61. The laser beam emitted from the laser source 4 is reflected to the focus lens 62. The focusing lens 62 continues to focus the reflected laser beam inside the workpiece 8 to form the break points of the waveforms arranged in a single waveform. Compared with the laser damage point of the dot matrix arrangement in the prior art, the number of laser damage points arranged by the waveform of the present invention is small enough to achieve an excellent splitting effect, and thus the processing efficiency is high.

In conjunction with the above-described laser cutting device 100, the laser cutting method of the present invention mainly forms a laser beam along a predetermined cut surface 80 inside the workpiece 8 as shown in the first or second figure along the waveform curve. Or a plurality of sawtooth array break points 81 (step 101), and then the workpiece 8 is broken along the predetermined cut surface by a naturally occurring (or additional cooling or bending) stress (step 102). During the cutting process, the peak power density and the pulse width of the focus of the laser beam are controlled to be at least sufficient to cause nonlinear multiphoton absorption inside the workpiece 8, thereby forming the damage points therein for processing. The surrounding area of the cut-off is not damaged, which is especially important for the micro-machining of precision components.

Specifically, the laser cutting method includes the following steps: first, controlling the optical system 6 to focus the laser beam emitted by the laser light source 4 to a first target position of a predetermined depth inside the workpiece 8, and then The laser light energy output controlling the laser source 4 is at least sufficient to cause nonlinear multiphoton absorption inside the workpiece such that the laser beam forms a first break point at the first target location of the workpiece. Then, the polygon mirror 61 of the optical system 6 is slightly rotated to change the focus position of the laser beam, and the workpiece 8 is laterally moved by the moving platform 5, so that the laser beam is focused on the inside of the workpiece 8 a second target position of a predetermined depth. At this time, the laser light energy output corresponding to the adjustment of the laser light source 4 is at least sufficient to generate nonlinear multiphoton absorption inside the workpiece, so that the laser beam forms a second position at the second target position of the workpiece 8. Two break points. The focus position of the laser beam is changed by the same method, and the workpiece 8 is laterally moved, so that the laser beam is focused on a third target position of another predetermined depth inside the workpiece 8; and the laser beam is adjusted correspondingly. The output is such that the laser beam forms a third break point at the third target location of the workpiece 8. Subsequently, one or more laser damage points may be sequentially struck according to the material or the thickness, so that the workpiece 8 naturally generates stress (or slightly applies an external force) and the predetermined cut surface 80 formed along the break points. disconnect. It should be noted that, in the preferred embodiment, the lateral movement of the laser beam and the workpiece is achieved by moving the mobile platform 5, but not limited thereto, and may be borrowed in other examples. The purpose of mutual movement is achieved by moving the laser light source 4 and the optical system 6.

In summary, the laser cutting method of the present invention applies a laser beam unidirectionally along a cutting path on the workpiece 8, and changes the focus position of the laser beam itself during the unidirectional cutting process. A plurality of breaking points 81 of different depths are formed inside the workpiece, and finally the workpiece 8 is broken along the cracks formed by the breaking points. This method not only does not produce hot melt on the surface of the workpiece, but also has high processing precision, especially the processing efficiency is improved.

In any event, anyone can obtain sufficient teaching from the description of the above examples, and it is understood that the present invention is indeed different from the prior art, and is industrially usable and progressive. It is the invention that has indeed met the patent requirements and has filed an application in accordance with the law.

100. . . Laser cutting device

4. . . Laser source

5. . . mobile platform

6. . . Optical system

61. . . Polygonal mirror

610. . . Mask

62. . . Focusing lens

7. . . control unit

8. . . Machined parts

80. . . Scheduled cut surface

81. . . Destruction point

L. . . Laser beam

1. . . Machined parts

2. . . Cutting path

3, 3a, 3b, 3c. . . Laser damage point

The first figure is a schematic perspective view of a preferred embodiment of a laser cutting apparatus according to the present invention.

The second figure is a schematic cross-sectional view of the structure shown in the first figure.

The third figure is a block diagram of the structure shown in the first figure.

The fourth figure is a flow chart of a preferred embodiment of the laser cutting method of the present invention.

The fifth figure shows a conventional laser cutting method.

The sixth figure shows another way of conventional laser cutting.

The seventh figure shows the phenomenon that the laser cutting point of the sixth figure forms a crack.

The eighth figure shows another way of conventional laser cutting.

100. . . Laser cutting device

4. . . Laser source

5. . . mobile platform

6. . . Optical system

61. . . Polygonal mirror

610. . . Mask

62. . . Focusing lens

8. . . Machined parts

80. . . Scheduled cut surface

81. . . Destruction point

Claims (10)

A laser cutting method comprising the steps of forming a plurality of break points arranged along a wavy curve or a zigzag with a laser beam on a predetermined cut surface inside a workpiece. The laser cutting method of claim 1, wherein a peak power density and a pulse width of a focus of the laser beam are controlled to be at least sufficient to generate a nonlinear photon absorption inside the workpiece. These break points are formed. The laser cutting method of claim 1, wherein an incident angle of the laser beam and the predetermined cut surface are zero. The laser cutting method of claim 1, wherein the workpiece is arranged to move laterally relative to the laser beam and perpendicular to an incident direction of the laser beam; and the laser beam is arranged to be longitudinally back and forth. The focus is varied to form the breakpoints of the waveform or jagged arrangement described above. A laser cutting method, the method comprising: applying a laser beam unidirectionally along a cutting path on the workpiece, and changing a focus position of the laser beam itself during the unidirectional cutting process to The interior forms complex damage points of different depths. A laser cutting method comprising the steps of: (a) focusing a laser beam at a first target position of a predetermined depth inside a workpiece; (b) controlling an output of the laser beam to cause the mine The beam of light forms a break point at the first target position of the workpiece; (c) modulating the focus position of the laser beam and laterally moving the workpiece relative to the laser beam such that the laser beam is focused on the processing a second target position of another predetermined depth inside the piece; (d) correspondingly adjusting the output of the laser beam such that the laser beam forms another breaking point at the second target position of the workpiece; (e). Rechanging the focus position of the laser beam and laterally moving the workpiece relative to the laser beam such that the laser beam is focused on a third target position of another predetermined depth inside the workpiece; and (f). The output of the laser beam is adjusted such that the laser beam forms a further break point at the third target location of the workpiece; wherein the three break points together form a predetermined cut surface of the workpiece. The laser cutting method of claim 6, wherein in steps (b), (d), (f), the peak power density and the pulse width of the focus of the laser beam are controlled to be at least sufficient These non-photon absorptions are generated inside the workpiece to form the fracture points. A laser cutting device comprising: a laser light source for exciting a laser beam; a moving platform for transferring a workpiece; an optical system for adjusting a focus position of the laser beam; and a control unit And controlling the optical system to change the output of the laser beam and the focus position in a process of moving the workpiece in the moving platform, so that the laser beam is formed on a predetermined cut surface inside the workpiece. A plurality of break points arranged along a wavy curve or zigzag. The laser cutting device of claim 8, wherein the optical system comprises a polygon mirror and at least one focusing lens; the polygon mirror is disposed between the laser source and the focusing lens, and The polygon mirror can rotate with its long axis as an axis, so that the polygon mirror of the polygon mirror alternately reflects the laser beam emitted by the laser source to the focusing lens; the focusing lens is used for the polygon mirror The reflected laser beam is focused inside the workpiece to form the break points. The laser cutting device of claim 8, wherein the control unit controls the peak power density and the pulse width of the focus of the laser beam to be at least sufficient to generate nonlinear multiphoton absorption inside the workpiece, These break points are formed.