KR100573259B1 - Laser cutting device using heat induced crack propagation - Google Patents

Abstract

 The present invention relates to a laser cutting device, and more particularly, to a laser cutting device for cutting the brittle material by causing a crack in the cutting site to the brittle material using a laser. The present invention provides a laser unit which emits a laser beam to heat a predetermined cutting line portion on a substrate, and an ejection slit elongated in the cutting line direction to spray a gas having a predetermined pressure into a predetermined portion on the substrate heated by the laser beam. And a conveying unit for moving a relative position of said laser unit and said cooling stream supply means with respect to said substrate along said predetermined cutting line. According to the present invention, it is possible to provide a laser cutting device using a heat-induced crack propagation method having a dry cooling system that provides high cooling efficiency and does not cause a problem of substrate contamination.

Laser cutting, cooling stream, discharge slit, preheating, complete cutting

Description

LASER CUTTING MACHINE USING THERMALLY INDUCED CRACK PROPAGATION TECHNIQUE}

Figure 1a is a diagram schematically showing a mechanism for cutting the base material using a conventional heat induced crack propagation method.

FIG. 1B is a view schematically showing a conventional laser cutting device using the wet cooling method.

FIG. 2 is a diagram schematically illustrating a conventional cutting mechanism that enables complete cutting of a substrate in a laser cutting device.

3 is a view schematically showing a laser cutting device according to a first embodiment of the present invention.

4 shows the cooling stream supply means of FIG. 3 in more detail.

5 is a view schematically showing a laser cutting device according to a second embodiment of the present invention.

6 is a view schematically showing a laser cutting device according to a third embodiment of the present invention.

7 is a view schematically showing a laser cutting device according to a fourth embodiment of the present invention.

8 is an enlarged view illustrating an irradiation section of each laser beam in the embodiment of the present invention described with reference to FIGS. 6 and 7.

<Short description of the symbols in the drawings>

10: cutting line 100: substrate

150: transfer and rotation stage 200: laser unit

210, 210A, 210B: laser source 211, 211A, 211B: laser beam

222, 222A, 222B, 222C, 222D: Focusing Lens

310: cooling stream inlet 400: cooling stream supply means

410: discharge slit 420: gas inlet

600: compressor

The present invention relates to a laser cutting device, and more particularly, to a laser cutting device for cutting the brittle material by causing a crack in the cutting site to the brittle material using a laser.

Many devices, such as LCD panels or semiconductor devices, are manufactured by cutting individual panels or devices from large area glass panels or wafers, such as silicon and sapphire, on which a plurality of devices or devices are formed.

Conventionally, the cutting of a base material, ie, a panel or a wafer, with a mechanical cutting device such as a diamond wheel has been used to cut individual panels or devices. However, the mechanical cutting method requires an additional cleaning process due to chipping or contamination by lubricating oil generated during the cutting process. In addition, the scribe area corresponding to the thickness of the wheel in the base material is wasted, which is uneconomical, and the wear of the wheel makes it difficult to standardize the cutting process.

As an alternative to the conventional mechanical cutting process, there is a cutting method using a laser ablation method. This method cuts the base material by locally heating and vaporizing it with a high power laser along a predetermined cutting line of the base material. However, this method also has a relatively large beam size of the laser beam, and there is a fear of contamination of the base metal by the melt vaporized gas. In particular, the laser ablation method is not satisfactory at the cutting speed because sufficient energy must be applied to vaporize the base material.

Another method of cutting the base material using a laser is a method of causing a crack in a portion to be cut of the base material and cutting the base material by controlling the crack to proceed along an arbitrary cutting line. This method has a relatively fast cutting speed and has the advantage of preventing contamination in the cutting process, attracting a lot of attention in recent years.

Figure 1a schematically shows a mechanism for cutting the base material by this method.

Referring to FIG. 1A, a laser beam 211 is generated from a laser unit (not shown) and irradiated to the substrate 100 through a suitable optical system (not shown). The irradiation area heated by the laser beam is subsequently cooled by injection of the cooling stream 310. Through this process, the laser beam irradiation area on the surface of the substrate 100 is placed under a very large thermal stress, and as a result, cracks are generated in the irradiation area. When the substrate 100 heats and cools the substrate S while moving relative to the laser beam 211 and the cooling stream 410 along the cutting line 10 of the substrate 100, the cracks It extends over the entire surface of the substrate 100 and is formed. After forming a crack over the entire substrate through the above-described process, it can be cut by applying a suitable tensile stress to the substrate 100.

Rapid cooling of the substrate is essential for the laser cutting technique described in connection with FIG. 1A. To this end, conventionally, a dry cooling method of spraying a gas stream such as He, Ne, Ar, CO _2, or compressed air on a substrate, or a wet cooling method of mixing the cooling gas and a cooling liquid and spraying the substrate on a substrate has been used. In the wet cooling method, the cooling liquid is preferable in that the heat capacity per unit volume is higher than that of the gas, thereby enabling more efficient cooling. However, there is a high possibility that the ejected cooling liquid is scattered on the substrate and contaminates the substrate.

1B schematically illustrates a conventional laser cutting device for cooling a substrate 100 using a coolant. As shown, the laser cutting device includes a laser unit 200, a coolant supply port 310, and a coolant suction port 410. The coolant suction port 410 sucks the coolant ejected from the coolant supply port 310 to the substrate 100. The coolant supply port 310 is formed at an appropriate position so that the coolant is not sucked before contacting the substrate 100. However, despite such measures, it is difficult to expect the coolant to be properly recovered by the inlet 410.

As described above, the laser cutting apparatus using the conventional thermally induced crack propagation method does not solve the problem of providing a cooling system that does not cause contamination of the substrate while providing an efficient cooling capacity.

On the other hand, with the above-described conventional laser cutting device, complete cutting of the substrate cannot be obtained. To cut the substrate, there must be other external means such as applying a tensile stress. In order to remedy this drawback, efforts have been made to provide a device that enables complete cutting of a substrate in a laser cutting device without a separate external force. One such attempt is Heokstra, US Pat. No. 6,420,678.

The method of the patent discloses a method of cutting a substrate with a laser cutting device having two laser beams. Referring to Figure 2, the method of the patent will be described in detail. First, a predetermined region of the surface of the substrate 100 is irradiated with a scribe beam 211A along a preset cutting line 10 to be heated. Subsequently, a coolant is supplied to the irradiation area through the cold air injection port 310, and thus microcracks are formed in the area. Next, a pair of braking beams 211B is irradiated to both sides of the cutting line 10 that has undergone the heating and cooling. The breaking beam 211B generates tensile stress on both surfaces of the cutting line 10, which acts as a driving force for propagating micro cracks formed in the cutting line 10. The scribe beam 211A, the cold air injection port 310 and the braking beam 211B move along the cutting line 10 of the substrate 100, thereby cutting the substrate 100 along the cutting line 10. .

As mentioned above, the patent considers the mechanism of breaking brittle materials in two stages. That is, cracks are generated using a scribe beam, and cracks are propagated using a breaking beam. However, even by the method of the patent, no complete cutting across the substrate thickness is achieved. This seems to be because the method of the patent does not provide enough energy to complete cutting of the substrate by the generation and propagation of cracks.

Therefore, there is an urgent need for a new laser cutting device and method for achieving complete cutting of brittle material by thermally induced crack propagation.

An object of the present invention is to provide a laser cutting device using a heat-induced crack propagation method having a dry cooling system that provides high cooling performance and does not cause substrate contamination.

In addition, an object of the present invention is to provide a laser cutting device using the heat-induced crack propagation method to ensure the complete cutting of the substrate.

It is also an object of the present invention to provide a laser cutting device having high precision and cutting speed while ensuring complete cutting of the substrate.

In order to achieve the above technical problem, the present invention provides a laser unit which emits a laser beam to heat a predetermined cutting line portion on a substrate, and injects a gas of a predetermined pressure into a predetermined portion on the substrate heated by the laser beam. And a cooling stream supply means having an elongated discharge slit in a cutting line direction and a conveying unit for moving a relative position of the laser unit and the cooling stream supply means with respect to the substrate along the predetermined cutting line. do.

According to a preferred embodiment of the present invention, the laser unit may further include a beam splitter for dividing the emitted laser beam into two beams having a predetermined interval. In addition, the apparatus may further include a compressor for supplying compressed gas to the cooling stream supply means, and may further include a cooling device for supplying cooling gas to the cooling stream supply means as necessary. In the present invention, the width of the discharge slit is preferably smaller than the width of the laser beam irradiation area in the substrate, the width of the discharge slit is preferably 10 ~ 200 ㎛. In addition, the discharge slit may have a structure inclined so that the width of the opening becomes narrower from the inner side to the outer side of the cooling stream supply means.

The present invention also relates to a laser unit that emits a first laser beam and a second laser beam that heat along a predetermined cutting line on a substrate at predetermined intervals, the predetermined cutting being heated by the first and second laser beams of incoming gas. Cooling stream supply means having an ejection slit elongated in the cutting line direction so as to spray to a predetermined portion on the line and a transfer unit for moving the relative position of the laser unit and the cooling stream supply end with respect to the substrate along the predetermined cutting line. It provides a laser cutting device comprising a.

In the present invention, the first and second laser beams emitted from the laser unit may be generated from different sources, respectively.

Alternatively, the laser unit may include a laser source, a beam splitter for dividing a laser generated from the laser source into the first laser beam and the second laser beam, and each of the first and second laser beams at the predetermined interval. And an optical system that focuses on the cut line.

According to a preferred embodiment of the present invention, each of the first and second laser beams heats a predetermined area along the predetermined cutting line on the substrate, and the heating area by the first laser beam is connected to the second laser beam. It is preferable to have an area larger than the heating area. The first and second laser beams each heat a predetermined area along the predetermined cutting line on the substrate, and the heating areas of the first and second laser beams are elongated along the predetermined cutting line. desirable. To this end, the optical system may comprise a first cylindrical lens for the first laser beam and a second cylindrical lens for the second laser beam.

Also in accordance with a preferred embodiment of the present invention, when each of the first and second laser beams heats a predetermined area along the predetermined cutting line on the substrate, the heating area of the first laser beam and the second laser beam The heating zones of can be configured to overlap slightly.

Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention with reference to the drawings. Like reference numerals in the accompanying drawings refer to like elements.

3 is a view schematically showing a laser cutting device according to an embodiment of the present invention. As shown, the laser cutting device of the present invention comprises a laser unit 200, a cooling stream supply means 400 and a conveying unit 500.

Although not specifically illustrated, the laser unit 200 includes a laser source 210 and optical systems 222 and 224 for guiding the laser beam 211 generated from the laser source 210 to the substrate S. FIG. Doing.

4 is a view showing in detail the cooling stream supply means 400 of the present invention. This will be described with reference to FIG. 4.

4 shows a cross-sectional view of the cooling stream supply means 400 of the present invention in the longitudinal direction, and the left view shows a front view of the baron seen from the outlet of the cooling stream. As shown in the cross-sectional view, the cooling stream supply means 400 has a gas inlet 420 connected at one end to a gas supply conduit. The introduced air passes through the inside of the cooling stream supply means 400 and is discharged through the discharge slit 410 installed at the other end. The discharge slit 410 has an elongated slit shape, the slit 410 is mounted to the laser cutting device so that the longitudinal direction is disposed in the direction of the cutting line of the substrate. A fixing means 460, such as a fixing jig, is provided along the outer circumference of the cooling stream supply means 400 to attach the cooling stream supply means 400 to the laser cutting device.

In the present invention, the width W _S of the slit is determined in consideration of the irradiation area formed by the laser beam on the substrate. The width W _S of the slit is preferably narrower than the width of the irradiation area of the laser beam in order to provide local thermal stress to the irradiation area of the laser beam. In the present invention, since the width of the irradiation area of the laser beam is preferably about 200 μm or less, the width of the slit is also preferably in the range of 10 μm to 200 μm. Such narrow width slits can be produced by ultrasonic lapping or laser processing.

In the present invention, the discharge slit 410 is not limited to the rectangle as shown, and may have any shape elongated, for example, elliptical.

On the other hand, the depth δ of the discharge slit can be appropriately adjusted to ensure the straightness of the discharged gas in the present invention. In addition, the discharge slit 410 may have a structure inclined so that the opening becomes narrower from the inner side to the outer side of the cooling stream supply means. Such a structure may give an effect of focusing the gas discharged to the discharge slit 410 on the cutting line of the substrate 100.

In the present invention, the slit 410 is the housing 200 of the laser unit so that the laser beam 211 is well aligned with the point on the substrate 100 to be irradiated during operation of the laser cutting device and the arrangement direction of the slit is not changed. It can be attached to. Of course, not limited to this, other methods may be used as long as the discharge slit can be aligned with the laser beam.

In the present invention, the type of gas introduced into the cooling stream supply means 400 is not limited, but it is preferable to use air in terms of economy. In addition, in the present invention, the air may be compressed air, and the compressed air may be supplied through a compressed air bombe. Alternatively, the compressor 600 as shown may be used to continuously supply a constant pressure of compressed air. In addition, the gas may be provided by being cooled, and for this purpose, a separate cooling device may be provided on the supply path of the gas flowing into the cooling stream supply means 400.

Laser cutting device of the present invention is provided with a transfer means 500 to move the laser unit 200 and the cooling stream supply means 400 along a predetermined cutting line (not shown) on the substrate 100 have. The transfer means 500 may transfer the laser unit 200 and the cooling stream supply means 400 in three axes (x-axis, y-axis, z-axis) direction. In the present invention, the transfer means 500 serves to support the laser unit 200 and the cooling stream supply means 400. However, the configuration of the present invention for the transport and support shown is merely exemplary. Alternatively, a substrate support (not shown) for fixing the substrate 100 may move.

The above-described apparatus of the present invention allows the present invention to transfer the laser unit and cooling stream supply means along any predetermined cutting line (not shown), and to continuously heat and cool the points on the substrate 100. Can be. Accordingly, microcracks may be formed on the surface of the substrate along the cutting line, and the substrate may be cut along the cutting line by applying tensile stress by a subsequent bending process or the like.

Advantages of the laser cutting device of the present invention described with reference to FIG. 4 are as follows.

Conventional dry laser cutting devices using compressed gas such as He, Ne, Ar, CO ₂ or compressed air as the cooling medium have used nozzles as the means for discharging the gas. However, when the gas is injected from the nozzle to reach the substrate, there is a problem that the width of the actual cooling region becomes very wide due to diffusion. As a result, not only the laser beam irradiation area but also the surrounding substrate area is cooled together and the cooling efficiency is inevitably decreased, and unnecessary areas are also cooled at a time, thereby providing a large thermal stress locally in a desired area. However, the discharge slit of the present invention has an elongated shape in the direction of the cutting line, and since the width thereof is very narrow, only the desired portion on the cutting line can be cooled, thereby increasing the cooling efficiency as well as applying rapid thermal stress to the cut part. Can provide.

In addition, in the case of using a compression means such as a compressor, crack formation can be facilitated by intensively spraying a high-pressure compressed gas into the discharge slit to impact the substrate.

5 is a view for explaining another embodiment of the present invention using the aforementioned cooling stream supply means.

As shown, in this embodiment, two laser beams are used to cut the substrate. The laser beam generated by one laser source 210 is divided into a scribe beam 211B and a breaking beam 211A by the beam splitter 226 and the reflector 224 to be irradiated onto the substrate. The cooling stream supply means 400 supplies a cooling stream between the region A1 on the substrate irradiated by the scribe beam 211B and the region A2 on the substrate irradiated by the breaking beam. The scribe beam 211B, cooling stream and the braking beam 211A are aligned with the cutting line 10 of the substrate. The substrate 100 is adapted to move relative to the scribe beam 211B, the breaking beam 211A and the cold air stream by a transfer unit (not shown). Therefore, any point on the substrate along the cut line will experience thermal history in the order of heating → cooling → heating. The scribe beam 211B and the cold air stream cause cracks, and the breaking beam 211A causes crack propagation.

In this embodiment, the lenses 222A and 222B that focus the two laser beams onto the substrate may be appropriately configured according to their respective purposes. For example, to form an elongated scribe beam 211B in the direction of the cutting line 10, a cylindrical lens having a longitudinal direction arranged in the direction of the cutting line of the substrate may be used, and a breaking beam having a large irradiation area may be used to fix the convex lens. It can obtain by arrange | positioning in a defocus position. Of course, the braking beam 211A can also be embodied as two elongated braking beams parallel to the cutting line, as described above in US Pat. No. 6,420,678, for which a lens system comprising a faceted lens can be used. Can be.

The gas supplied by the cooling stream supply means 400 with discharge slits in this embodiment not only provides sufficient stress for the generation of cracks, but also forms cracks of high energy state, thereby heating the subsequent breaking beam. Cracks propagate easily when tensile stress is applied, thereby facilitating complete cutting of the substrate.

The laser cutting device of the present invention described above with reference to FIGS. 3 to 5 may induce brittle fracture of a substrate by dividing each stage of generation of cracks and propagation of cracks.

6 is a view for explaining a laser cutting mechanism for achieving complete cutting of the substrate as another embodiment of the present invention.

Referring to FIG. 6, two laser beams 211A and 211B are used in the present invention. The two laser beams 211A and 211B are divided from one laser source 210. For this purpose, the laser cutting device of the present invention is provided with a beam splitter 226 and a reflector 224.

As shown, the first laser beam 222B and the second laser beam 222A are aligned at predetermined intervals with a predetermined cutting line 10 on the substrate. In addition, a cooling stream is provided spaced a predetermined distance from the second laser beam 222A along the cutting line 10. In the present invention, an interval formed by the first laser beam 222B, the second laser beam 222A, and the cooling stream may be appropriately controlled to achieve an optimal cutting speed.

By means of suitable conveying means (not shown), the section on the cut line through which the first laser beam 222B, the second laser beam 222A and the cooling stream are supplied changes on the cut line. The transfer may be accomplished by movement of the substrate or movement of the first laser beam 222B, the second laser beam 222A and the cooling stream.

Due to the above configuration, any point on the cutting line 10 of the substrate 100 is in the order of preheating by the first laser beam 211B, heating by the second laser beam 211A, and cooling by the cooling stream. Experience the heat history. Therefore, in consideration of the moving direction of the substrate 100 (see arrow), in the illustrated drawing, each point on the cutting line of the region A1 'is heated by the first laser beam, and each point of the region A2' is Each point of heating by the first and second laser beams, area A3 ', is in a state where it has experienced heating by the first and second laser beams and cooling by a cooling stream. Due to the transfer of the substrate, every point of the cutting properties of the substrate undergoes thermal history in the order of preheating, heating and cooling.

In the present invention, the surface of the substrate 100 on the cutting line is subjected to two heating stages: a preheating step by the first laser beam 211B and a heating step by the second laser beam 211A. The effect can be explained as follows.

In a conventional laser cutting method by heat-induced crack propagation, the surface of a substrate, such as a glass substrate, is locally heated by a laser beam above a softening temperature. However, according to the conventional one-step heating method, the depth to be heated in the substrate is inevitably very shallow. Long time heating is required to heat deeper areas from the substrate surface, but this inevitably leads to a reduction in cutting speed, and long time heating may cause melting of a portion of the substrate surface. In the present invention, by heating the substrate in two stages, it is possible to lengthen the time the substrate surface is exposed to the laser beam and to heat to a deeper point from the substrate surface. Thus, the thermal stresses generated at the substrate surface generated by subsequent substrate cooling will be much greater than those provided by conventional laser cutting mechanisms.

As described above, the two-step process of the present invention allows heating from the substrate surface to deep regions, so that a cooling stream for cooling the heated substrate requires higher heat removal capability. In this regard, the cooling stream supply means 400 of the present invention described above may be a preferred means for providing the cooling stream.

FIG. 7 illustrates another embodiment of implementing the cutting mechanism of the present invention described with reference to FIG. 6. As shown, the same as described with respect to FIG. 6 except that the two laser beams 211A, 211B are generated from different laser sources 210A, 210B.

FIG. 8 is an enlarged view of irradiation sections A1 ′ and A2 ′ of the first laser beam 211B and the second laser beam 211A on the substrate 100 in the embodiment shown in FIGS. 6 and 7. One drawing. As shown, it is preferable that the irradiation sections A1 'and A2' of the two laser beams formed on the substrate surface have an elongated shape along the cutting line 10, respectively. This is because the irradiation time of the first laser beam 211B and the second laser beam 211A can be increased to increase the depth at which heat penetrates into the substrate.

In order to form the elongated irradiation sections A1 'and A2', it is preferable to use a lens that focuses the laser beam linearly. To this end, in the present invention, an optical lens that focuses each laser beam 211A and 211B ( 222C and 222D, cylindrical lenses whose axial direction is aligned with the cutting line 10 direction of the substrate can be used.

In addition, it is preferable that the irradiation section A1 'of the first laser beam has a larger area than the irradiation section A2' of the second laser beam. This prevents a sudden rise of the substrate surface temperature by the first laser beam 211B intensively irradiating the substrate surface. For example, in the embodiment of the present invention illustrated in FIG. 8, the irradiation section A1 ′ has a wider width than the irradiation section A2 ′. In other words, the relationship W1> W2 is established. Such an irradiation section A2 ′ can be obtained by arranging the cylindrical lens 222C focusing the first laser beam in a defocused position in the above-described optical lens system.

Further, in order to increase the heating efficiency of the laser beam, it is preferable that any point on the substrate cutting line undergoes the preheating step and the heating step continuously. Therefore, in the present invention, the irradiation section A1 ′ of the first laser beam and the irradiation section A2 ′ of the second laser beam overlap each other, that is, d = 0 and the first laser beam 211B. It is preferable to adjust the interval S of the second laser beam 211A.

According to one aspect of the present invention, by discharging the cooling gas through the discharge slits having a long and narrow width in the direction of the cutting line of the substrate, it is possible to locally cool only the desired portion on the substrate, thereby increasing the cooling efficiency. It can also provide greater thermal stress to the substrate surface.

In addition, the application of a cooling stream supply means having discharge slits to a laser cutting device having a cutting mechanism including preheating and heating by a laser beam ensures a very fast cutting speed while ensuring complete cutting of the substrate.

In addition, the cutting mechanism of the present invention can be applied not only to amorphous glass substrates but also to polycrystalline substrates, and thus can be applied very widely throughout brittle materials.

Claims (20)

delete delete delete delete delete delete delete Generating a first laser beam and a second laser beam that heat along a predetermined cutting line on the substrate at predetermined intervals, each of the first and second laser beams heating a predetermined area along the predetermined cutting line on the substrate, A laser unit having a larger area than the heating area by the second laser beam; Cooling stream supply means having an ejection slit elongated in the cutting line direction to spray the introduced gas into a predetermined portion on the predetermined cutting line heated by the first and second laser beams; And And a transfer unit for moving a relative position of said laser unit and cooling stream supply means relative to said substrate along said predetermined cutting line. The method of claim 8, And the first and second laser beams emitted from the laser unit are each generated from different sources. The method of claim 8, The laser unit Laser source; A beam splitter dividing a laser generated from the laser source into the first laser beam and the second laser beam; And And an optical system for focusing each of the first and second laser beams on the predetermined cutting line at the predetermined intervals. delete The method according to any one of claims 8 to 10, Each of the first and second laser beams heats a predetermined area along the predetermined cutting line on the substrate, And the heating area of the first and second laser beams is elongated along the predetermined cutting line. The method of claim 10, And the optical system comprises a first cylindrical lens for the first laser beam and a second cylindrical lens for the second laser beam. The method of claim 13, And the second cylindrical lens defocuss the second laser beam onto the predetermined cutting line on the substrate. The method according to any one of claims 8 to 10, Each of the first and second laser beams heats a predetermined area along the predetermined cutting line on the substrate, And the heating area of the first laser beam and the heating area of the second laser beam overlap slightly. The method of claim 8, And the width of the discharge slit is smaller than the width of the second laser beam irradiation area in the substrate. The method of claim 16, The width of the discharge slit is a laser cutting device of 10 ~ 200 ㎛. The method of claim 8, And the discharge slit is inclined so that the width of the opening becomes narrower from the inside to the outside of the cooling stream supply means. The method of claim 8, And a compressor for supplying compressed gas to the cooling stream supply means. The method according to claim 8 or 19, And a cooling device for supplying cooling gas to said cooling stream supply means.

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