JP5879106B2 - Method for scribing a brittle material substrate - Google Patents

Description

  The present invention relates to a scribing method for a brittle material substrate, and more particularly, to a scribing method for forming a scribe groove along a planned cutting line of a brittle material substrate.

  As a method of forming a scribe groove for dividing in a glass substrate, there is a method of forming using a laser beam. In this case, a scribe groove is formed by melting and evaporating a part of the substrate by irradiating a laser beam along the division line. However, in this method, a part of the dissolved and evaporated substrate may adhere to the surface of the substrate, which may be accompanied by deterioration of quality. In addition, the scar formed in the melted and evaporated part causes a reduction in the strength of the substrate end face.

Therefore, as the cutting method other glass substrate processing method using a CO ₂ laser which is absorbed by the glass substrate surface is provided. Here, the substrate surface is heated by irradiating and scanning a laser on the glass substrate. And a crack is advanced by cooling this heating area | region with the cooling medium injected from a cooling nozzle. Thereby, a scribe groove | channel is formed along the parting plan line and a glass substrate is parted.

  However, in such a method, since the shape of the laser beam becomes an ellipse, it is difficult to form or divide a scribe groove along a curved line to be cut. In addition, since there are optimum machining conditions depending on the length and width of the beam, it is necessary to find these machining conditions. Furthermore, since a beam with a width of several millimeters is usually required under conditions of a practical processing speed of at least several millimeters / s, the distance from the substrate to the cutting line (hereinafter referred to as “ear width”) There are limitations. In other words, when the ear width is extremely small and becomes less than the beam width, it becomes impossible to divide along such a division line.

  In Patent Document 1, when a glass substrate or the like is divided along a curved dividing line, the strength of both ends of a linear beam spot having a predetermined length is remarkably increased, and both ends are divided. It is shown that the machining is performed by moving it so as to be positioned on the planned line.

Special table 2003-516236 gazette

  In the processing method disclosed in Patent Document 1, it is necessary to scan both ends of a linear beam spot along a planned dividing line. In order to perform such scanning, it is necessary to execute very complicated control. Moreover, the curve shape which can be divided | segmented is also limited, For example, it cannot cut along the curve with a small curvature. In addition, since the beam width cannot be reduced, the problem that the ear width that can be processed is limited cannot be solved.

  It is an object of the present invention to provide a scribing method that can be easily divided along a curved dividing line and that can reduce the width of the ear.

  The brittle material substrate scribing method according to the first aspect of the present invention is a method of forming a scribe groove along a planned cutting line of the brittle material substrate, and includes the following steps.

  Heating / cooling process: Condensing and irradiating a laser having a wavelength that absorbs and transmits with respect to the brittle material substrate so that the focal point is located within the range from the front surface to the back surface of the substrate, and the laser irradiation region A cooling medium is injected simultaneously with irradiation.

  Scanning step: A beam spot by laser irradiation and a cooling spot by jetting of a cooling medium are scanned along a line to be divided.

  Here, the substrate is irradiated with a laser having a certain degree of transparency and absorption with respect to the substrate. By this laser irradiation, the substrate is heated not only to the surface but also to the inside. Simultaneously with this heating, the heated portion is cooled by the cooling medium. For this reason, a temperature gradient is generated inside the substrate. Due to this temperature gradient, tensile stress is generated on the substrate surface, and compressive stress is generated inside the substrate. This causes a crack in the substrate. Then, by scanning the beam spot and the cooling spot as described above along the planned dividing line, the crack progresses along the planned dividing line and a scribe groove is formed.

  In this method, the focal point of the laser is focused between the front surface and the back surface of the substrate, that is, in the vicinity of the front surface, and the cooling spot is formed at the laser irradiation position simultaneously with the laser irradiation. The substrate can be easily scribed along the line. In addition, since there is almost no time difference from heating by laser irradiation to cooling by the cooling medium, the temperature spread to the surroundings becomes small. For this reason, even when the ear width is small, temperature asymmetry between the end side and the opposite side of the substrate hardly occurs. As a result, processing with a small ear width is possible as compared with the conventional processing method.

  The brittle material substrate scribing method according to the second invention is the method of the first invention, wherein an initial crack is formed as a pre-process of the heating / cooling step at the scanning start end of the line to be cut on the surface of the brittle material substrate. It further includes a forming step.

  Here, an initial crack is formed at the scanning start end of the line to be divided. Thereafter, a heating / cooling step and a scanning step are performed. In this case, the crack progresses along the planned split line from the initial crack, and a scribe groove is formed.

  The brittle material substrate scribing method according to the third invention is the method of the first or second invention, wherein the laser wavelength in the heating / cooling step is 2.7 μm or more and 4.0 μm or less.

  By using such a laser to irradiate, for example, a glass substrate, not only the surface of the glass substrate but also the inside can be heated.

  The brittle material substrate scribing method according to a fourth aspect of the present invention is the method according to any one of the first to third aspects, wherein the brittle material substrate is a glass substrate.

  The brittle material substrate scribing method according to a fifth aspect of the present invention is the method according to any one of the first to fourth aspects of the present invention, wherein the cooling medium is sprayed onto the substrate surface so that a jet processing trace by laser irradiation is located at the center of the jet trace. Is done.

  The brittle material substrate scribing method according to a sixth aspect of the present invention is the method according to any one of the first to fifth aspects, wherein a reflector for reflecting the laser is installed on the back surface of the brittle material substrate as a pre-process of the heating / cooling step. It further includes a preparation step.

  As described above, when the thickness of the substrate is thin, the substrate cannot sufficiently absorb the laser even when the laser is irradiated, and heating is insufficient. Therefore, in the fifth aspect of the invention, a reflecting plate that reflects the laser is installed on the surface of the substrate opposite to the surface on the laser irradiation side. By performing this step, the laser can be sufficiently absorbed even in a thin substrate, and the inside of the substrate can be sufficiently heated.

  As described above, according to the present invention, the cutting can be easily performed along the curved dividing line, and the ear width can be reduced.

The schematic block diagram of the apparatus for enforcing the scribe method by one Embodiment of this invention. The figure which shows the transmittance | permeability of soda glass with respect to a laser wavelength. The figure which shows the board | substrate transmittance | permeability and absorption factor of the laser for every plate | board thickness. The photograph which shows a laser irradiation area | region (irradiation trace) and a cooling spot (jetting trace). The figure for demonstrating the relationship between the focus position (a substrate surface, the inside, a back surface) of a laser, and a scribe margin. The figure for demonstrating the relationship between the focus position (above a board | substrate) of a laser, and a scribe margin. The figure which shows the deviation | shift amount from the parting plan line at the time of processing along the straight parting plan line by the processing method by one Embodiment of this invention. The figure which shows the deviation | shift amount from the parting plan line at the time of processing along the curvilinear parting plan line by the processing method by one Embodiment of this invention.

[Device configuration]
FIG. 1 is a diagram showing a schematic configuration of a scribing apparatus for carrying out a method according to an embodiment of the present invention. The scribing apparatus 1 is an apparatus for dividing a single mother substrate into a plurality of glass substrates, for example. The glass substrate here is, for example, a soda glass substrate.

  The scribing apparatus 1 includes a table 2 on which a glass substrate G to be processed is placed, a laser oscillator 3, a reflection mirror 4 that guides the laser from the laser oscillator 3 to the table 2, a condenser lens 5, and a cooling device. Nozzle 6.

  Here, the laser oscillator 3 outputs a laser having a wavelength having absorptivity and transparency to the glass substrate G. The condensing lens 5 condenses the laser so that the focal point is located between the front surface and the back surface of the glass substrate G. The cooling nozzle 6 injects a coolant supplied from a coolant source (not shown) onto the surface of the glass substrate G to form a cooling spot. Although not shown, a table moving mechanism that moves the table 2 on which the glass substrate G is placed in a horizontal plane and a lens moving mechanism that moves the condenser lens 5 up and down are provided. The table moving mechanism scans the laser irradiation area (beam spot) and the cooling spot along the planned dividing line.

  Although not shown here, an initial crack forming means for forming an initial crack serving as a starting point of scribing is provided at the end of the glass substrate G on the scanning start side. As the initial crack forming means, a mechanical tool such as an indenter or a cutter wheel is used, but it is also possible to form an initial crack by laser ablation processing.

[Scribe method]
First, using an initial crack forming means such as a cutter wheel, an initial crack serving as a starting point for scribing is formed at the end portion on the scanning start side of the division line of the glass substrate G.

  Next, the glass substrate G is irradiated with a laser. The laser is condensed by the condensing lens 5 so that the focal point is located on the front surface of the glass substrate G or between the front surface and the back surface. In addition, the cooling medium is jetted from the cooling nozzle 6 simultaneously with the laser irradiation and onto the region irradiated with the laser.

  Here, since a laser having a wavelength that absorbs and transmits the glass substrate G is used as the laser, the surface and the inside of the glass substrate G are heated by the laser irradiation. On the other hand, a cooling medium is injected into the laser irradiation region to be cooled. For this reason, a temperature gradient is generated inside the substrate, a tensile stress is generated on the surface of the glass substrate G, and a compressive stress is generated inside. This causes a crack in the substrate.

  By scanning the above laser spot and cooling spot along the planned dividing line, the crack progresses along the planned dividing line and a scribe groove is formed.

<Laser>
FIG. 2A shows the relationship between the wavelength of the laser (Er fiber laser) and the transmittance for soda glass having various thicknesses. Moreover, the transmittance | permeability and absorption factor for every board thickness are shown in FIG. 2B. The absorption rate is a calculated value.

  As is clear from these figures, in the wavelength range of 2.8 μm to 4.0 μm, the transmittance is 55% and 46% for glass substrates having thicknesses of 1.3 mm (solid line) and 1.8 mm (broken line), respectively. % And the absorption rate are 45% and 54%, respectively, and have some absorbency and permeability. With these thickness substrates, the irradiated laser was absorbed inside the substrate and could be scribed.

  Even if the absorptance is low due to a thin plate thickness or the like, if the absorptance is 10% or more, a higher output laser is used, or the surface opposite to the surface irradiated with the laser By providing a reflecting plate for reflecting the laser, the laser can be sufficiently absorbed inside the substrate. In addition, by performing cooling from the surface opposite to the laser irradiation surface, a temperature gradient sufficient for crack propagation can be provided inside the substrate.

  In the following experiments, an Er fiber laser having a wavelength of 2.8 μm is used.

<Beam spot and cooling spot>
FIG. 3 shows an enlarged photograph showing details of the processed portion. In FIG. 3, the portion indicated by the circle L at the center is the laser irradiation trace, and the portion indicated by the circle C is the jet trace of the cooling medium. As apparent from FIG. 3, the laser irradiation and the cooling medium injection are simultaneously performed so that the beam spot is positioned at the center of the cooling spot.

<Influence of focus position>
In FIG. 4, the focal position of the laser is the substrate surface (a), the substrate center (b), and the substrate back surface (c). The result of having experimented how a scribe margin changes is shown. The glass substrate used in this experiment is soda glass having a thickness of 1.3 mm.

  In FIG. 4, “◯” indicates that scribing is possible (a crack has progressed along the line to be divided from the initial crack), “×” indicates that scribing is not possible (a crack along the line to be divided does not progress from the initial crack), “ "Stop" is processing stop (crack along the planned split line progresses from the initial crack, but the crack progress stops during processing), and "first" is the first run (crack not along the planned split line has progressed) It is shown that.

  FIG. 4 shows that the scribe margin is almost the same even when the focal position is changed between the front surface and the back surface of the substrate.

  On the other hand, FIG. 5 shows experimental results obtained by processing a glass substrate similar to that shown in FIG. 4 with the focal position separated upward by 10 mm from the upper surface of the glass substrate. In this case, the beam diameter on the surface of the glass substrate is 660 μm. Therefore, the beam power density on the substrate surface is low, and the substrate temperature is not sufficiently high. For this reason, scribing cannot be performed unless the scanning speed is reduced and the laser output is increased.

  From the above experimental results, it can be seen that it is desirable to perform processing with the focal position of the laser set between the front surface and the back surface of the glass substrate.

<Deviation from the planned dividing line>
FIG. 6 is an experimental example showing how much the crack is formed from the planned dividing line when the processing method of the present embodiment is performed. The horizontal axis indicates the position along the dividing line (0 mm indicates the substrate end on the initial crack side), and the vertical axis indicates the amount of deviation from the planned dividing line. The glass substrate used in the experiment is soda glass with a thickness of 1.3 mm and a length of 55 mm. The laser output is 7.5 W and the scanning speed is 20 mm / s.

  As shown in FIG. 6, the amount of deviation from the parting planned line is +7 μm to −10 μm, and it can be seen that there is no significant deviation even by the processing method of this embodiment.

  In addition, when the processing method of this embodiment was implemented along the curvilinear division | segmentation scheduled line SL as shown in FIG. 7, the amount of deviation | shift of a maximum of 20 micrometers generate | occur | produced in the formed scribe groove | channel. However, since there is a tendency to shift to one side of the planned dividing line SL, it is possible to perform processing in consideration of this deviation.

[Feature]
(1) Since the focal point of the laser is set in the vicinity of the substrate surface and the cooling spot is formed at the laser irradiation position simultaneously with the laser irradiation, the substrate can be easily scribed along a curved cutting line.

  (2) Since heating and cooling are simultaneously performed on the same region of the substrate, the temperature spread to the surroundings is reduced. For this reason, even when the ear width is small, temperature asymmetry between the end side and the opposite side of the substrate hardly occurs. As a result, processing with a small ear width is possible as compared with the conventional processing method.

  (3) By using a laser having a wavelength of 2.8 μm or more and 4.0 μm or less with respect to the glass substrate, it can be effectively heated from the substrate surface to the inside. Therefore, a crack progresses smoothly and deviation from a parting schedule line is suppressed.

  (4) In a glass substrate having a plate thickness of 1.0 mm or more and 2.0 mm or less, by using a laser having a wavelength of 2.8 μm or more and 4.0 μm or less, it is possible to sufficiently heat the inside of the substrate. A scribe groove can be formed.

[Other Embodiments]
The present invention is not limited to the above-described embodiments, and various changes or modifications can be made without departing from the scope of the present invention.

  For example, in the said embodiment, although the experiment example was shown using soda glass as a brittle material substrate, as a brittle material substrate, it is not limited to soda glass.

2 Table 3 Laser oscillator 5 Condensing lens 6 Cooling nozzle

Claims (6)

A brittle material substrate scribing method for forming a scribe groove along a planned cutting line of a brittle material substrate,
A laser having a wavelength that absorbs and transmits light with respect to the brittle material substrate is focused and irradiated so that the focal point is located within the range from the front surface to the back surface of the substrate, and the laser irradiation region is simultaneously irradiated with the laser. A heating / cooling step in which a substrate is cracked by thermal stress by injecting a cooling medium to cool the laser irradiation region ;
A scanning step of causing the crack to propagate along the planned dividing line by scanning the beam spot generated by the laser irradiation and the cooling spot generated by jetting the cooling medium along the planned dividing line ;
Only including,
The laser spot and the cooling spot are irradiated and jetted so that the centers of both spots coincide.
A scribing method for a brittle material substrate.   The scribe method for a brittle material substrate according to claim 1, further comprising an initial crack forming step of forming an initial crack at a scanning start end of a line to be divided on the surface of the brittle material substrate as a pre-step of the heating / cooling step. .   The brittle material substrate scribing method according to claim 1 or 2, wherein a wavelength of the laser in the heating / cooling step is 2.7 µm or more and 4.0 µm or less. The brittle material substrate scribing method according to claim 1, wherein the brittle material substrate is a glass substrate.   The brittle material substrate scribing method according to claim 1, wherein the cooling medium is sprayed onto the substrate surface such that a jet processing trace by the laser irradiation is located at the center of the jet trace. The preparatory step of the heating / cooling step further includes a preparatory step of installing a reflector that reflects the laser on the surface opposite to the laser irradiation side of the brittle material substrate. The brittle material substrate scribing method described.