JP2004042423A - Scribing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scribing apparatus suitable for scribing a brittle material substrate of a large plate. <P>SOLUTION: Whole formation necessary for forming a scribe line on the brittle material substrate of a laser beam oscillator 3, an optical unit 4, a bend mirror 5, a cooling jet 6, and a trigger mechanism 7 is fitted integrally to a support 2. In this way, in the scribing apparatus 1, even when each formation necessary for forming the scribe line is moved in relation to the surface of the brittle material substrate S, the occurrence of variation in the forming positions of a heating area and a cooling area is prevented. Accordingly, the formation of a stable scribe line can be maintained, and the stable quality of the disruption surface of the brittle material substrate S disrupted through a break process implemented after the scribe line is formed can be secured. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a scribing apparatus suitable for forming a scribe line on a large brittle material substrate.
[0002]
[Prior art]
In order to cut a brittle material substrate typified by a glass substrate or the like, a scribing process for forming a scribe line in which vertical cracks, which are cracks formed at a predetermined depth from the surface on the brittle material substrate, are continued in a desired direction. And, following this scribing process, a break process for dividing the brittle material substrate along a scribe line formed in the scribing process by applying a pressing force to the brittle material substrate is generally performed. It has become a method.
[0003]
In a scribing process performed when a brittle material substrate is cut, a method of forming a scribe line using a wheel cutter made of cemented carbide or sintered diamond is known. However, in the method using such a wheel cutter, the cullet generated during the formation of the scribe line may adhere to the surface of the brittle material substrate, which causes display defects when used in a display device or the like. Moreover, when performing the breaking process which divides | segments a brittle material board | substrate, an undesired chip | tip may arise in the edge part etc. of a brittle material board | substrate, and there exists a possibility that the quality of the brittle material board | substrate after division | segmentation may become defective.
[0004]
On the other hand, in recent years, a method of forming a scribe line using a laser beam has been put into practical use. In the method of forming a scribe line using this laser beam, the laser beam LB is irradiated from the laser oscillation device 61 to the brittle material substrate S to be scribed as shown in FIG. The laser beam LB irradiated from the laser oscillation device 61 forms a laser spot LS on the brittle material substrate S along a scribe line. The laser beam LB emitted from the laser oscillation device 61 is set so as to be relatively moved on the brittle material substrate S along a scribe line.
[0005]
Further, a cooling medium such as cooling water is sprayed from the cooling nozzle 62 so that a scribe line is formed in the vicinity of the irradiation region of the laser beam LB on the surface of the brittle material substrate S. On the surface of the brittle material substrate S irradiated with the laser beam LB, a compressive stress is generated by heating with the laser beam LB, and then a cooling medium is blown to generate a tensile stress. As described above, since tensile stress is generated in a region close to the region where the compressive stress is generated, a stress gradient based on each stress is generated between the two regions, and the brittle material substrate S has the brittle material substrate S. A continuous crack is generated along a planned scribe line from a cut TR formed in advance by a wheel cutter or the like at the end.
[0006]
In the method of forming a scribe line using the laser beam as described above, the occurrence of cullet is extremely small, and thermal strain stress is used for forming the scribe line. Therefore, a brittle material substrate is used when performing the breaking process. Chipping is less likely to occur on
[0007]
[Problems to be solved by the invention]
The above scribe line forming method using laser beam irradiation is mainly applied when scribing a small glass substrate or the like used in a liquid crystal display device, but also when scribing a large glass substrate. It is possible to scribe by the same principle.
[0008]
In a laser scribing apparatus for scribing a large glass substrate, a laser oscillator that oscillates a laser beam of a predetermined wavelength is installed at a position separated from the large glass substrate to be scribed, and a transmission system such as a mirror is used. Therefore, it is designed to transmit the energy of the beam to the optical system head installed on the scribe line forming surface of the large glass substrate. A cooling nozzle for spraying a cooling medium is provided in the vicinity of the optical head. When a scribe line is formed on a large glass substrate using this scribe device, the optical system head and the cooling system are arranged along a desired scribe line direction with respect to the fixed large glass substrate. The nozzle is scanned, and a crack is developed in advance from a cut formed in the end portion by heating by irradiation with a laser beam and cooling by a cooling medium from a cooling nozzle, thereby forming a desired scribe line.
[0009]
However, in such an apparatus configuration, it is necessary to move the optical head and the cooling nozzle on the large glass substrate in order to form a scribe line on the large glass substrate. As the cooling nozzle moves, the optical path of the laser beam with respect to the glass substrate surface changes, the beam shape formed on the glass substrate surface changes, and the spraying position of the cooling medium blown from the cooling nozzle is changed. fluctuate. For this reason, it is difficult to maintain the formation of a stable scribe line due to the occurrence of such fluctuations. Therefore, after breaking the glass substrate along the scribe line, the quality of the sectional surface of the stable glass substrate is reduced. There is a problem that it is difficult to ensure.
[0010]
Further, in the above scribing apparatus, it is difficult to install a plurality of optical heads on the same large glass substrate surface, so that it is difficult to shorten the processing time (tact). .
[0011]
The present invention has been made in view of the above circumstances, and in the case where a scribe line is formed using laser beam irradiation and cooling by a cooling medium, optical path variation with respect to the scribe line forming surface of the brittle material substrate is completely eliminated. In addition, since a plurality of optical heads can be installed, the processing time can be shortened, and a scribing apparatus suitable for scribing a large brittle material substrate is provided. For the purpose.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, a scribing apparatus of the present invention includes a heating unit that forms a heating region on a brittle material substrate, a cooling unit that forms a cooling region near the heating region, and a starting point of a scribe line. A scribing device that forms a scribe line that is a continuation of vertical cracks developed from the cut by a stress gradient generated between the heating region and the cooling region. Fixing means for integrally fixing the heating means, the cooling means, and the cut forming means, and the heating means, the cooling means, the cut forming means, and the brittle material substrate fixed to the fixing means. Are moved while maintaining a relatively constant positional relationship with each other at a predetermined relative speed.
[0013]
In the scribing apparatus of the present invention, the heating means includes a laser oscillator that oscillates a laser beam, an optical unit that shapes the laser oscillated by the laser oscillator into a predetermined shape and irradiates the brittle material substrate, and the laser A transmission means arranged between an oscillator and the optical unit and transmitting a laser beam emitted from the laser oscillator to the optical unit, the laser oscillator, the optical unit and the transmission means being fixed It is preferable to be integrally fixed to the means.
[0014]
In the scribing apparatus of the present invention, the cooling means and the cut forming means are respectively arranged on both sides of the moving direction with the heating means interposed therebetween, and the fixing means advances and moves with respect to the brittle material substrate. It is preferable that scribing is possible regardless of the direction of reverse travel.
[0015]
In the scribing apparatus of the present invention, it is preferable that a plurality of the fixing means are provided, and a scribe line is simultaneously formed at a plurality of locations on the brittle material substrate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the scribing apparatus of the present invention will be described in detail.
[0017]
(Embodiment 1)
FIG. 1 shows a schematic configuration of the scribing apparatus 1 according to the first embodiment. FIG. 1 (a) is a side view, FIG. 1 (b) is a plan view, and FIG. 1 (c) is a front view. Hereinafter, the scribing apparatus 1 according to the first embodiment will be described with reference to FIGS.
[0018]
This scribing device 1 has a support base 2 formed in a flat plate shape. A laser oscillator 3 that oscillates a laser beam having a predetermined irradiation energy is integrally attached to the support table 2 on the upper surface of the support table 2. In the support 2, an opening 2 a is formed on the laser beam emission side of the laser oscillator 3, and the laser beam emitted from the laser oscillator 3 is incident on the lower surface of the opening 2 a so as to be predetermined. The optical system unit 4 that emits light to the surface of the brittle material substrate S to be scribed is integrally attached to the support base 2. Further, two bend mirrors 5 that reflect the laser beam emitted from the laser oscillator 3 in the direction of the optical system unit 4 provided on the lower surface of the opening 2a are supported above the opening 2a of the support base 2. It is provided integrally with the base 2.
[0019]
A cooling jet 6 that blows a cooling medium onto the surface of the brittle material substrate S is integrally attached to the lower surface of the support table 2 in the vicinity of the optical system unit 4. In addition, a trigger mechanism 7 is provided on the opposite side of the cooling jet 6 across the optical system unit 4 to form a notch serving as a start point (trigger) of a scribe line at the end of the brittle material substrate S or the like. Yes.
[0020]
The cooling jet 6, the optical system unit 4, and the trigger mechanism 7 are arranged in this order so as to be on the same straight line along the scheduled scribe line. The cooling jet 6 and the optical system unit 4 are formed in a close positional relationship between a cooling region formed by spraying a cooling medium on the brittle material substrate S and a heating region formed by laser beam irradiation. Therefore, they are arranged close to each other. The trigger mechanism 7 may be close to or away from the heating region formed by the laser beam irradiation of the optical system unit 4 as long as it can form a vertical crack serving as the starting point of the scribe line. The installation position may be arbitrary.
[0021]
In addition, the support base 2 to which the laser oscillator 3, the bend mirror 5, the optical system unit 4, the cooling jet 6, and the trigger mechanism 7 are integrally attached can be moved along a planned scribe line by a drive mechanism (not shown). Thus, when the scribe line is formed, the support base 2 is moved in a direction in which the trigger mechanism 7 side becomes the head with respect to the brittle material substrate S. Further, the support 2 is adjusted to a suitable moving speed for forming a scribe line by this moving mechanism.
[0022]
The laser beam oscillated from the laser oscillator 3 melts the brittle material substrate S because the heating temperature of the heating region formed on the brittle material substrate S prevents the surface of the brittle material substrate S from melting. A material having an energy lower than the temperature, that is, lower than the softening point of the brittle material substrate S is used. In this case, since the softening point varies depending on the type of the brittle material substrate S to be scribed, the irradiation energy of the laser beam oscillated from the laser oscillator 3 is set to be changeable according to the type of the brittle material substrate S. Is preferable.
[0023]
In the optical system unit 4, the laser beam emitted from the laser oscillator 3 and incident through the two bend mirrors 5 has a desired shape suitable for forming a scribe line, for example, a long length along the scribe line direction. Shape it into a circle.
[0024]
The cooling medium blown out from the cooling jet 6 is typically cooling water because it is easy to use. However, a gaseous cooling medium such as a cooling CO ₂ gas, N ₂ gas, or He gas, or a cooling organic solvent. It is possible to change to a liquid cooling medium such as.
[0025]
The trigger mechanism 7 is provided with mechanical means such as a cutter wheel at an end portion close to the surface of the brittle material substrate S, and at a desired position of the brittle material substrate S, for example, at the end portion, the brittle material substrate S. By pressing against the surface, a cut is formed which becomes the starting point of the scribe line. This mechanical means needs to not press the brittle material substrate S except at a desired position on the brittle material substrate S, and the trigger mechanism 7 has a vertical movement mechanism (not shown) for moving the mechanical means up and down. ) Is provided. Further, as means for forming a cut in the surface of the brittle material substrate S, optical means such as YAG laser can be used in addition to mechanical means. In this case, since this optical means is not in contact with the surface of the brittle material substrate S, it is not necessary to provide a vertical movement mechanism.
[0026]
Next, a scribing method using the scribing apparatus 1 having the above configuration will be described.
[0027]
First, the brittle material substrate S to be scribed is placed below the optical system unit 4, the cooling jet 6, and the trigger mechanism 7 of the scribe device 1. At the time of this placement, the brittle material substrate S is aligned so that the direction of the scribe line on the surface of the brittle material substrate S coincides with the scribe direction of the scribe device 1.
[0028]
Next, the support base 2 to which the optical system unit 4, the cooling jet 6, and the trigger mechanism 7 are integrally attached is moved with respect to the brittle material substrate S by driving the moving mechanism. When the support base 2 is moved, first, the trigger mechanism 7 reaches the end of the brittle material substrate S. At this end position, a mechanical means such as a wheel cutter attached to the tip of the trigger mechanism 7 is pressed against the surface of the brittle material substrate S, thereby forming a break that becomes the starting point of the scribe line at this position.
[0029]
After the cut is formed on the surface of the brittle material substrate S, the mechanical means at the tip of the trigger mechanism 7 is not in contact with the surface of the brittle material substrate S so that unintended scratches or the like are not generated on the surface of the brittle material substrate S. The state of contact is set, and the movement of the support base 2 is continued. When the optical unit 4 and the cooling jet 6 on the lower surface of the support base 2 reach the surface of the brittle material substrate S, the laser oscillator 3 starts to be driven, and cooling medium such as cooling water is sprayed from the cooling jet 6. Start.
[0030]
When the laser oscillator 3 is driven, a laser beam having a predetermined energy is oscillated. The oscillated laser beam is reflected by the two bend mirrors 5 in the direction of the opening 2 a formed in the support 2, and the laser beam that has passed through the opening 2 a enters the optical system unit 4. In the optical system unit 4 on which the laser beam is incident, the laser beam is formed into a desired shape such as an oval shape and is irradiated toward the surface of the brittle material substrate S. On the surface of the brittle material substrate S, a heating region corresponding to the laser spot of the irradiated laser beam is formed.
[0031]
A cooling medium such as cooling water is sprayed from the cooling jet 6 onto the surface of the brittle material substrate S, and a cooling region is formed at a position near the heating region by laser beam irradiation.
[0032]
In the heating region formed on the surface of the brittle material substrate S, compressive stress is generated, and in the cooling region where the cooling medium is sprayed, tensile stress is generated. The compressive stress caused by the laser beam irradiation and the tensile stress in the cooling region due to the cooling medium formed behind the laser beam are formed on the scribe line on the brittle material substrate S, and the heating region and the cooling region are scheduled to be scribed. By sequentially moving on the line, vertical cracks are continuously formed from the cuts formed at the end of the brittle material substrate S, and a desired scribe line is formed.
[0033]
In the scribing apparatus 1 according to the first embodiment, all configurations necessary for forming a scribe line for the laser oscillator 3, the bend mirror 5, the optical system unit 4, the cooling jet 6, and the trigger mechanism 7 are provided on the support base 2. It is attached integrally. For this reason, even if each component is moved with respect to the surface of the brittle material substrate S, the optical path of the laser beam with respect to the surface of the brittle material substrate S is prevented from changing, and the surface of the brittle material substrate S is irradiated. The beam shape of the laser beam does not change. Moreover, the spraying position of the cooling medium sprayed from the cooling jet 6 does not change and is constant. Therefore, the formation of a stable scribe line can be maintained, and the quality of the stable sectional surface of the brittle material substrate S that is divided through the breaking process performed after the scribe line is formed can be ensured.
[0034]
In the first embodiment, the example in which the support base 2 moves has been described. However, the brittle material substrate S may be moved with respect to the support base 2.
[0035]
(Embodiment 2)
FIG. 2 is a side view showing the scribing apparatus 10 according to the second embodiment.
[0036]
The scribing device 10 has substantially the same configuration as the scribing device 1 of the first embodiment shown in FIG. 1 described above. In addition to the configuration of the scribing device 1 of the first embodiment, the trigger mechanism 7 and The cooling jets 6 are provided on both sides of the optical system unit 4, respectively, and a moving mechanism for moving the support base 2 is configured to be movable in both the front and rear directions. In this scribing apparatus 10, the same reference numerals are assigned to the same components as those of the scribing apparatus 1 described above.
[0037]
In the scribing apparatus 10 according to the second embodiment, the trigger mechanism 7 and the cooling jet 6 are provided on both the front and rear sides of the optical system unit 4 as described above, so that one scribing on the brittle material substrate S is completed. After that, by moving the position of the brittle material substrate S and moving the support base 2 in the direction opposite to the first scribe, a scribe line can be formed subsequently.
[0038]
Therefore, in addition to the effect obtained by the scribing apparatus 1 of the first embodiment, the scribing apparatus 10 of the second embodiment enables reciprocal cutting, and therefore further shortens the processing time. And can be suitable for forming a scribe line for a large brittle material substrate.
[0039]
In the second embodiment, the example in which the support base 2 moves has been described. However, the brittle material substrate S may be moved with respect to the support base 2.
[0040]
(Embodiment 3)
3-5 has shown schematic structure of the scribing apparatus 20 of Embodiment 3, FIG. 3 is the side view, FIG. 4 is the top view, FIG. 5 has shown the front view, respectively. Hereinafter, the scribing apparatus 20 according to the third embodiment will be described with reference to FIGS.
[0041]
The scribing device 20 has a support base 21 formed in a flat plate shape. A laser oscillator 22 that oscillates a laser beam having a predetermined irradiation energy is integrally attached to the support table 21 on the upper surface of the support table 21. In the support base 21, an opening 21a is formed on the laser beam emitting side of the laser oscillator 22, and the laser beam emitted from the laser oscillator 22 is incident on the lower surface of the opening 21a so as to be predetermined. After shaping into a shape, an optical system unit 23 that emits light to the surface of the brittle material substrate S to be scribed is integrally attached to the support base 21. Further, two bend mirrors 24 that reflect the laser beam emitted from the laser oscillator 22 in the direction of the optical system unit 23 provided on the lower surface of the opening 21a are positioned above the opening 21a of the support base 21. It is provided integrally with the support base 21.
[0042]
A cooling jet 25 that blows a cooling medium onto the surface of the brittle material substrate S is integrally attached to the lower surface of the support base 21 in the vicinity of the optical system unit 23. In addition, a trigger mechanism 26 is provided on the opposite side of the cooling jet 25 across the optical system unit 23 to form a notch serving as a scribe line start point (trigger) at the end of the brittle material substrate S or the like. Yes.
[0043]
In the third embodiment, there are provided a plurality of support bases 21 to which such a laser oscillator 22, a bend mirror 24, an optical system unit 23, a cooling jet 25, and a trigger mechanism 26 are integrally attached as one constituent unit. Thus, it is possible to form scribe lines on a single brittle material substrate S at a plurality of locations simultaneously by one scribe.
[0044]
That is, in the scribing device 20 of the third embodiment, a plurality of support bases 21 are installed on one moving mechanism 27. The moving mechanism 27 has a moving table portion 28 on which each support table 21 is installed. In the scribing device 20, a pair of guide rails 29 parallel to the planned scribe line are formed on both sides of the moving base portion 28 of the moving mechanism 27, and the moving base portion 28 is placed on the guide rail 29. , Can move on the scribe line. The moving table 28 is moved along the guide rail 29 by driving means (not shown).
[0045]
Alternatively, the movable table 28 provided with each support table 21 may be fixed, and the brittle material substrate S may be moved and scribed by a moving means (not shown).
[0046]
Further, as shown by the dotted lines in FIG. 4, each support table 21 provided on the moving table unit 28 can be positioned on the moving table unit 28 in a direction perpendicular to the planned scribe line, and is brittle. A scribe line can be formed at a desired position on the surface of the material substrate S.
[0047]
The details of the laser oscillator 22 and the like are the same as those of the laser oscillator 1 and the like of the first embodiment, and therefore, the description of the details of each configuration is omitted here.
[0048]
Further, the scribing method using the scribing apparatus 20 is also the same as the scribing method using the scribing apparatus 1 of the first embodiment, and detailed description thereof is omitted. However, in the third embodiment, since there are a plurality of support bases 21 provided with a configuration necessary for forming a scribe line such as the laser oscillator 22 as one unit, one brittle material substrate S has 1 A plurality of scribe lines can be formed simultaneously by one scribe.
[0049]
As described above, in the scribing apparatus 20 according to the third embodiment, a plurality of scribing lines can be formed at the same time by one scribing. Therefore, as compared with the scribing apparatus 1 according to the first embodiment, further processing is performed. It becomes possible to shorten the processing time.
[0050]
As described above, the scribing device 20 according to the third embodiment includes a plurality of support bases 21 that are simplified by integrally configuring the configuration of the laser oscillator 22 and the like necessary for scribing as one unit. A plurality of scribe lines can be simultaneously formed on the brittle material substrate S, which is suitable for forming a large number of scribe lines on a large brittle material substrate.
[0051]
In the third embodiment, each support base 21 has the same configuration as the support base 2 of the scribing apparatus of the first embodiment and can be scribed in only one direction. However, the scribing apparatus 10 described in the second embodiment is used. Similarly to the support base 2, the trigger mechanism 7 and the cooling jet 6 may be provided on both sides of the optical system unit 4, respectively, and the support base may be configured to be movable in both the front and rear directions. With this configuration, it is possible to scribe in both the front and rear directions, and the processing time can be further shortened.
[0052]
【The invention's effect】
The scribing apparatus of the present invention described above includes a heating unit that forms a heating region on a brittle material substrate, a cooling unit that forms a cooling region in a position close to the heating region, and a break that is the starting point of the scribe line. Fixing means for integrally fixing the cut forming means to be formed, and the fixing means maintains the fixed positional relationship between the heating means, the cooling means and the cut forming means with respect to the brittle material substrate. It is characterized by being moved while. In the scribing apparatus of the present invention, even if each component necessary for scribe formation is moved with respect to the surface of the brittle material substrate, it is possible to prevent fluctuations in the formation positions of the heating region and cooling region. Therefore, the formation of a stable scribe line can be maintained, and the quality of the stable sectional surface of the brittle material substrate S that is divided through the breaking process performed after the scribe line is formed can be ensured.
[0053]
Further, in another scribing apparatus of the present invention, the cooling means and the cut forming means are arranged on both sides in the traveling direction of the brittle material substrate across the heating means, and the fixing means is the brittle material substrate. On the other hand, it is possible to scribe the brittle material substrate regardless of whether it moves in the forward direction or the reverse direction. Thereby, it is possible to shorten the processing time and to be suitable for forming a scribe line of a large brittle material substrate.
[0054]
The scribing apparatus according to the present invention further includes a moving means that can install a plurality of fixing means that integrally fix the heating means, the cooling means, and the cut forming means, and can move each fixing means in the same direction. Then, the fixing means are moved in the same direction by the movement of the moving means so that scribe lines are formed simultaneously at a plurality of locations on the surface of the brittle material substrate. Accordingly, a plurality of scribe lines can be formed with one scribing on one brittle material substrate, and the processing time can be shortened. It can be suitable for forming a line.
[Brief description of the drawings]
1A and 1B show a schematic configuration of a scribing apparatus according to Embodiment 1, wherein FIG. 1A is a side view, FIG. 1B is a plan view, and FIG.
FIG. 2 is a side view showing a scribing apparatus according to a second embodiment.
FIG. 3 is a side view showing a scribing device according to a third embodiment.
4 is a plan view showing a scribing apparatus according to Embodiment 3. FIG.
FIG. 5 is a front view showing a scribing device according to a third embodiment.
FIG. 6 is a schematic diagram for explaining a method of dividing a brittle material substrate using laser beam irradiation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Scribe device 2 Support stand 3 Laser oscillator 4 Optical system unit 5 Bend mirror 6 Cooling jet 7 Trigger mechanism 10 Scribe device 20 Scribe device 21 Support stand 22 Laser oscillator 23 Optical system unit 24 Bend mirror 25 Cooling jet 26 Trigger mechanism 27 Movement mechanism 28 Moving base 29 Guide rail

Claims (4)

A heating unit that forms a heating region on the brittle material substrate, a cooling unit that forms a cooling region near the heating region, and a cut forming unit that forms a cut serving as a starting point of a scribe line, A scribing device that forms a scribe line that is a continuation of vertical cracks developed from the cut by a stress gradient generated between a heating region and the cooling region,
The heating means, the cooling means, and the cut forming means are provided with fixing means for integrally fixing the heating means, the cooling means, the cut forming means, and the brittle material substrate fixed to the fixing means. A scribing apparatus that moves while maintaining a relatively constant positional relationship at a predetermined relative speed. The heating means includes a laser oscillator that oscillates a laser beam, an optical unit that shapes the laser oscillated by the laser oscillator into a predetermined shape and irradiates the brittle material substrate, and a space between the laser oscillator and the optical unit. And a transmission means for transmitting the laser beam emitted from the laser oscillator to the optical unit, and the laser oscillator, the optical unit and the transmission means are integrally fixed to the fixing means. The scribing apparatus according to claim 1, wherein the scribing apparatus is provided. The cooling means and the cut forming means are respectively arranged on both sides of the moving direction with the heating means interposed therebetween, and the fixing means moves in either forward or backward direction with respect to the brittle material substrate. The scribing apparatus according to claim 1, wherein scribing is possible. The scribing apparatus according to any one of claims 1 to 3, wherein a plurality of the fixing means are provided, and a scribe line is simultaneously formed at a plurality of locations on the brittle material substrate.

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