JP2011143434A - Laser beam drilling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide laser beam drilling (with a hole diameter of about 1 to 10 mm) for rapidly forming a hole in a glass substrate having a thickness of about 1-10 mm by using laser beam while the residual stress is suppressed. <P>SOLUTION: First, a hole is rapidly drilled in a glass substrate with CO<SB>2</SB>laser beam, and then an inner wall of the hole is finished with the removing width being ≥100 μm by using UV laser beam to the hole. Thus, the hole with less residual stress, and less burrs in the inner wall of the hole or the like can be formed in the glass substrate without using any drill. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser drilling method suitable for drilling a glass substrate with a laser.

Flat panel displays such as a plasma display (PDP), a liquid crystal display (LCD), a field emission display (FED), and an electroluminescence display (ELD) are attracting a great deal of attention as thin video display devices.
In the flat panel display, a plasma display (hereinafter referred to as a PDP) which is a self-luminous display device has a glass plate thickness of 1.8 mm to 2.8 mm, has heat resistance, and is not subject to thermal deformation and thermal contraction. Blue plate glass (soda lime glass) with a suppressed high strain point is used.
In general, a panel portion of a PDP is provided with a pair of electrodes regularly arranged on two opposing blue plate glass substrates, a discharge cell is formed between the barrier ribs, and a discharge gas is sealed between the barrier ribs. By applying a voltage between the electrodes and generating a discharge in a minute discharge cell sandwiched between barrier ribs, each discharge cell coated with a phosphor emits light to display an image.

  In the manufacturing process of the PDP panel, the discharge gas is sealed by attaching an exhaust pipe to a through-hole having a diameter of about 2 mm, which is previously opened at one corner of the glass substrate opposite to the display surface side, and exhausting from there. Thus, the inside of the panel is evacuated, and thereafter, discharge gas mainly containing Xe and Ne is sealed and sealed.

  Such a through hole having a diameter of about 2 mm to a glass substrate having a thickness of about 2 to 3 mm is generally formed by mechanical processing using a drill having diamond abrasive grains (see, for example, Patent Document 1 and Patent Document 2). However, the wear of the drill is severe, and drill replacement due to wear and adjustment after the replacement are frequently performed, and running cost becomes a bottleneck. For example, as disclosed in Patent Document 1, in the case of processing with a glass substrate thickness of 2.8 mm and a hole diameter of 4 mm, the number of holes to be drilled with one drill is less than 150 holes.

  In the drilling of a glass substrate, mechanical processing using a drill having diamond abrasive grains is the mainstream, but laser processing is also technically possible. The advantages of laser processing are as follows: (1) There is no frequent blade replacement due to drill wear and processing adjustment after replacement. (2) The laser oscillator replacement life varies depending on the model, but it has about 10,000 hours. Therefore, there may be little downtime throughout the year.

In the case of drilling with a laser on a general transparent blue plate glass substrate, the laser in the 1064 nm of YAG and YVO ₄ and the 532 nm (green laser) region of the second harmonic is considered from the relationship of the absorption rate of the laser beam to the glass substrate. Since light has a low absorption rate to the glass substrate, it is necessary to consider laser light absorption under a short pulse laser or special conditions in order to use laser light in these wavelength ranges. Drilling with a CO ₂ laser having a wavelength or a UV laser with a short wavelength near 355 nm is considered to be common (see, for example, Patent Document 3 and Patent Document 4).

  First, FIG. 10 shows an example of a laser processing apparatus that performs drilling using such a laser on such a glass substrate. FIG. 10 is a plan view of the laser processing apparatus. In the case of this processing apparatus, the laser beam 306 irradiated from the laser oscillator 302 changes the optical path by the reflection mirror 303, and irradiates the glass substrate 1 through the galvano scanner 304 and the condensing lens (fθ lens) 305 to form a through hole having a target size. It has a structure that can be formed. Although not shown, the actual apparatus is provided with a dust collector or the like for collecting shavings generated at the time of drilling at a peripheral position of the glass substrate 1 to which the laser beam 306 is irradiated.

  As the drilling process on the glass substrate by the laser processing apparatus, the glass substrate 1 is supplied and mounted on the stage 301 of the laser processing apparatus main body. The stage 301 is an XY axis movement table. As for the method of supplying the glass substrate 1 to the stage 301, when this apparatus is connected to the upstream apparatus and the transfer loader in the factory production line, the glass substrate is supplied from the transfer loader unit. If not connected by a transfer loader, it may be supplied by a transfer robot or the like. In the case of stand-alone installation in a laboratory or the like, it may be supplied by manual handling depending on the size of the substrate.

  The glass substrate 1 supplied and mounted on the stage 301 is chucked by a glass substrate holder (not shown), and the position of the glass substrate 1 can be changed through the movement of the stage by driving the XY axes of the stage. .

  The laser oscillator 306 is irradiated with laser light 306, the optical path is changed by the reflection mirror 303, and the glass substrate 1 is irradiated with the laser light 306 that has passed through the galvano scanner 304 and the condensing lens (fθ lens) 305. Form. The processing by the laser beam 306 generates dust when the glass at the position irradiated with the laser beam 306 is blown, and this is collected by a dust collector (not shown).

  In the case of the laser processing apparatus shown in this example, since the galvano scanner 304 is mounted, the stage is moved within the control range (about 50 mm □) of the galvano scanner 304 and the condenser lens (fθ lens) 305. And can be drilled at any position.

  This operation will be described with reference to the flowchart of FIG. The glass substrate 1 is transported and supplied to and mounted on the stage 301. The supplied glass substrate 1 is chucked by a glass substrate holding unit (not shown) (step 401), and can be changed through movement of the stage in the XY axis direction.

  When processing is started by an operator's instruction or the like, the glass substrate 1 is drilled at the irradiation point of a laser beam 306 from a galvano scanner 304 and a condenser lens (fθ lens) 305 (hereinafter collectively referred to as “processing head”). The movement of the stage 301 is controlled so that the positions match, and the glass substrate 1 is moved to a predetermined position (step 402). After the glass substrate 1 is moved and fixed to a predetermined position (step 403), irradiation with the laser beam 306 is started and a through hole having a target size is processed (step 404). After completion of the drilling process (step 405), the glass substrate chuck is released, and the glass substrate 1 is unloaded and processed from the stage (step 406).

As described above, a CO ₂ laser or a UV laser is used as a laser for processing. However, although the CO ₂ laser has a high speed of glass hole processing, the quality of the inner wall of the hole is inferior to the processing by the UV laser, and the periphery of the hole There is a problem that the residual stress is also larger than that of the UV laser. In particular, stress concentration occurs at the hole entrance and exit, and cracks are likely to occur.

On the other hand, the UV laser has a very good quality of the inner wall of the glass hole processing and hardly generates residual stress around the hole, but has a problem that the processing time is extremely longer than that of the CO ₂ laser.

As a method for solving such a laser processing problems, poor hole wall quality but performs rough drilling fast CO ₂ laser processing speed at a high speed, good hole wall machining quality as hole wall finish immediately after rough drilling Patent Document 5 discloses a method of performing a finishing process with a UV laser that can remove the deteriorated portion. However, this method has been developed for printed circuit boards, and there has been no example in which such a method has been applied to a glass substrate, and it has been questioned whether it has a residual stress relaxation effect.

JP 2001-172035 A

JP 2006-305672 A

JP-A-6-79486 (paragraph 0008, paragraph 0011)

JP 2003-183054 A (paragraph 0021, paragraph 0044)

JP-A-2-182390

  An object of the present invention is to provide a drilling process (hole diameter of about 1 mm to 10 mm) using a laser and suppressing residual stress on a glass substrate having a plate thickness of about 1 mm to 10 mm.

In order to solve the above-mentioned problems, first, a glass substrate is drilled at high speed with a CO ₂ laser, and then the inner wall of the hole is finished with a UV laser to remove the removal width to 100 μm or more. As a result, it was found that the inner wall of the hole can be deburred and the residual stress around the hole can be reduced.

  The laser drilling method of the present invention has an advantage that holes with less residual stress and burrs on the inner wall of the hole can be machined without using a drill.

It is a schematic view of a preferred laser processing apparatus for laser drilling method according to the invention, showing a case of processing with a CO ₂ laser. It is the schematic of the laser processing apparatus suitable for the laser drilling method by this invention, and shows the case where it processes with UV laser. 3 is a flowchart of a laser drilling method according to the present invention. It is the drawing substitute photograph which showed the hole shape by the laser drilling method by this invention, and the conventional method. Example 1 4 is a drawing-substituting photograph showing measurement results of residual stresses by a laser drilling method according to the present invention and a conventional method. Example 1 It is explanatory drawing which showed typically the hole shape by the laser drilling method by this invention. Example 1 It is explanatory drawing which showed typically the hole cross-sectional shape by the other laser drilling method by this invention. (Example 2) It is explanatory drawing which showed typically the UV finishing process by the other laser drilling method by this invention. (Example 2) It is the D section enlarged view of FIG. (Example 2) It is explanatory drawing which showed the laser processing apparatus used for the conventional laser drilling method. It is a flowchart of the conventional laser drilling method.

  1 and 2 show a laser processing apparatus suitable for a method of drilling a glass substrate with a laser according to the present invention. 1 and 2 are both front views, FIG. 1 shows a procedure 1 of the machining process according to the present invention, and FIG. 2 shows a procedure 2 of the machining process.

  This laser processing apparatus includes a laser oscillator 102 for rough drilling and a laser oscillator 112 for finishing the inner wall of the hole in the same apparatus. The stage 101 and the glass substrate 1 can be mounted in the XY axis direction and can be mounted on the glass substrate 1. A machining head composed of galvano scanners 104 and 114 condensing lenses (fθ lenses) 105 and 115 corresponding to the rough hole drilling laser 102 and the hole inner wall finishing laser 112, respectively, is installed immediately above the laser beam. Reflecting mirrors 103 and 113 for allowing light to enter, and a dust collector (not shown) for collecting glass shavings generated during drilling of the glass substrate 1 are provided around the processing head.

  This operation will be described with reference to the flowchart of FIG. The glass substrate 1 is conveyed and supplied to and mounted on the stage 101. The supplied glass substrate 1 is chucked by a glass substrate holding unit (not shown) (step 201), and can be changed through movement of the stage in the XY axis direction.

  When the processing is started by an operator's instruction or the like, the stage is set so that the drilling position of the glass substrate 1 is aligned with the irradiation point of the laser beam 106 from the processing head constituted by the galvano scanner 104 and the condenser lens (fθ lens) 105. 101 is controlled to move the glass substrate 1 to a predetermined position (step 202). After the glass substrate 1 is moved and fixed to a predetermined position (step 203), irradiation with the laser beam 106 is started and a through hole smaller than the target size is processed (step 204). In addition, the hole processing at this time is a rough hole forming processing in which processing speed is emphasized.

  After completion of rough machining (step 205), the stage 101 is moved so that the drilling position of the glass substrate 1 is aligned with the laser irradiation point where a different type of laser oscillator is mounted and the machining head is installed for finishing the inner wall of the hole. The glass substrate 1 is moved to a predetermined position (step 206). After the glass substrate 1 is moved and fixed to a predetermined position (step 207), irradiation with the laser beam 116 is started, and finishing of the inner wall of the hole is performed so as to obtain a target hole size (step 208).

  After finishing (step 209), the glass substrate chuck is released, and the glass substrate 1 is unloaded and processed from the stage (step 210).

  In the case of the laser processing apparatus shown in this example, the galvano scanner 104 and the condenser lens (fθ lens) 105 or the galvano scanner 114 and the condenser lens (fθ lens) 115 are within the respective control ranges (about 50 mm □). Can be drilled to any position without moving the stage.

  An example of drilling with a laser on a glass substrate according to the present invention will be described with reference to FIG. FIGS. 4A and 4C are examples of through-hole formation in a glass substrate by a conventional processing method, and FIG. 4B is an example of through-hole formation by a laser in a glass substrate according to the present invention. The glass substrate is a general blue plate glass having a thickness of about 2 mm, and the through hole diameter is about 3 mm.

FIG. 4A shows a processing example using a CO ₂ laser. The processing conditions at this time are shown below.
Processing mode: Trepanning processing Wavelength: 9400nm
Pulse repetition frequency: 600 Hz
Pulse width: 100 μs
Average output: 22W
Beam shape: Gaussian beam Beam diameter: 180 μm
Beam pitch (circumferential direction): 90 μm
Beam shift (radial direction): 66 μm
Processing hole diameter (hole exit): 3.0mmφ
Here, see FIG. 9 for beam pitch and beam shift.

In the processing with the CO ₂ laser, burrs existed on the inner wall of the hole and were rough, but the processing time at this time was about 85 seconds.

FIG. 4C shows an example of processing using a UV laser. The processing conditions at this time are shown below.
Processing mode: Trepanning processing Wavelength: 355nm
Pulse repetition frequency: 30 kHz
Pulse width: 25 ns
Average output: 4W
Beam shape: Gaussian beam Beam diameter: 25 μm
Beam pitch (circumferential direction): 4 μm
Beam shift (radial direction): 10 μm
Processing hole diameter (hole exit): 3.0mmφ

  In the processing by UV laser, there is no burr on the inner wall of the hole compared to FIG. 4 (a), but the surface is clean, but the processing time is about 750 seconds, which is about 9 times longer than that of FIG. 4 (a). did.

FIG. 4B shows an example of processing performed in the processing process according to the present invention shown in FIG. 3 with the laser used in FIGS. 4A and 4C. The conditions for rough hole machining with a CO ₂ laser (wavelength: 9400 nm) are set to 2.4 mmφ (hole exit diameter) only for the machining hole diameter in consideration of the removal width in the next step UV finishing, and 3.0 mmφ after UV finishing. (Hole exit diameter). The other conditions are the same as those in FIG.

  In the finishing process using a UV laser (wavelength: 355 nm), the removal width (W) was set to 300 μm, and other conditions were the same as those in FIG. Here, it is known that the removal width (W) by the UV laser should be 100 μm or more in order to relieve the residual stress. However, in this embodiment, the stress is more reliably relieved and the processing time is shortened. Therefore, the removal width (W) was set to 300 μm. The beam diameter may be 25 to 30 μm, the beam pitch may be 3 to 5 μm, and the beam shift may be 10 to 15 μm.

  By the above drilling process, there is no burr on the inner wall of the hole, and the processing time is about 120 seconds, which is reduced to about 1/6 compared with the case where all holes are formed by UV laser as shown in FIG. .

FIG. 5 shows an example in which the stress state remaining in the periphery of the machining hole in FIGS. 4A to 4C is visualized and the residual stress is measured by the photoelastic method. While the residual stress around the processing hole in the case of processing with the CO ₂ laser in FIG. 5A was about 0.37 MPa, the rough hole processing in FIG. 5B was performed with the CO ₂ laser, The residual stress when the hole inner wall finishing was performed with a UV laser was about 0.19 MPa, which was the same level as in the case of a hole processed with only the UV laser shown in FIG.

6A and 6B are a plan view and a cross-sectional view schematically showing the holes after drilling in FIGS. 4A and 4B. The mechanism of drilling the glass substrate 1 by the laser is based on a series of flows in which (1) the glass of the irradiated part is melted and (2) the molten part is evaporated by laser irradiation. In the case of drilling with a CO ₂ laser shown in FIG. 6A, since the machining pulse is as long as 100 μs, the glass melting time in the laser irradiation part becomes long, and the heat-affected zone of the hole inner wall glass is large. As a result, the drilling speed is fast, but the melted and solidified part is larger than when the UV laser is used. As a result, the inner wall of the hole becomes rough, and stress concentration occurs there, so the residual stress after completion of drilling also increases. End up.

On the other hand, when the hole inner wall is finished with the UV laser after the hole machining with the CO ₂ laser shown in FIG. 6B, the hole inner wall after the hole machining with the CO ₂ laser is rough on the hole inner wall for the above reason. However, in the processing with the UV laser, the processing pulse is 25 ns, which is very short compared to the CO ₂ laser. Therefore, the melting time of the glass in the laser irradiation part is short, and the heat-affected part on the inner wall of the hole can be small. As a result, the drilling speed is reduced, but is much smaller than when the melt-solidified portion is a CO ₂ laser. That is, in the processing of a UV laser after CO ₂ laser processing, by removing the coarse portion of the hole wall generated by the CO ₂ laser processing, it can speed machining than the through holes only by UV laser, also holes Since there is no stress concentration part by removing the inner wall rough part, the residual stress after completion of drilling can be reduced.

FIG. 7 is a cross-sectional view schematically showing after drilling according to another embodiment. First, rough hole machining is performed with a CO ₂ laser (wavelength: 9400 nm) under the same conditions as in FIG. 4A, and hole inner wall finishing is performed using a UV laser (wavelength: 355 nm) with a hole inlet (range A) and outlet ( The case where only range C) is performed is shown. The removal width by the UV laser was 120 μm at the entrance (W1) and 80 μm at the exit (W3), and other conditions were the same as in FIG. 4 (c).

FIG. 8 shows the relationship in the plan view of the removal width of the UV finishing process, and FIG. 9 shows an enlarged view of the D part. As can be seen from FIG. 8, the hole processing diameter (hole exit) with the CO ₂ laser was set to 3.0 mmφ after the UV finishing processing in consideration of the removal width by the UV finishing processing in the next step. FIG. 9 shows the state of trepanning processing of the hole entrance part (removal width W1) and the hole exit part (removal width W3) for two rounds, but in actuality, as calculated from the removal width and beam pitch, The inlet portion (removal width W1) has 10 turns, and the hole outlet portion (removal width W3) has 7 turns. Here, it is known that the removal width (W1) of the hole entrance portion is 100 μm or more, and the removal width (W3) of the hole exit portion is 60 μm or more, which has a stress relaxation effect. Similarly to the case of FIG. 4B, the beam diameter may be 25 to 30 μm, the beam pitch may be 3 to 5 μm, and the beam shift may be 10 to 15 μm.

  The central part of the inner wall of the hole (range B in FIG. 7) has a shape in which stresses cancel each other (stress stable distribution) in the adjacent glass melt-solidified part, but no cracks occur, but near the surface of the hole inlet / outlet (range in FIG. 7) In the melted and solidified portion in A and range C), the effect of canceling out the residual stress cannot be obtained (stress instability distribution), and this is the main cause of cracks at the hole entrance and exit.

Therefore, the rough portion (melted and solidified portion) of the inner wall (range A and range C in FIG. 7), which is the main cause of the occurrence of cracks due to the residual stress described above, has a pulse width of 25 ns (1 of the CO ₂ laser). When processed and removed with a UV laser of / 1000 or less), since the melting time was short, the melted and solidified portion was small, the residual stress was reduced, and it was confirmed that no cracks were generated even if the entire hole sidewall was not processed. Moreover, it was found that the processing time for UV finishing can be reduced by about 50% compared to the case of processing the entire inner wall of the hole.

  In addition, although the present embodiment tried to finish with a UV (355 nm) laser having a pulse repetition frequency of 100 kHz, a pulse width of 35 ns, and an average output of 16 W, the same effect was obtained and the UV finishing time was further shortened. I was sure that.

1 Glass substrate 101 Glass substrate stage (XY axis moving table)
102 Laser oscillator (for rough drilling)
103 Reflective mirror 104 Galvano scanner 105 Condensing lens (fθ lens)
106 Laser light 112 Laser oscillator (for finishing the inner wall of the hole)
113 Reflecting mirror 114 Galvano scanner 115 Condensing lens (fθ lens)
116 Laser light 301 Glass substrate stage (XY axis moving table)
302 Laser oscillator 303 Reflecting mirror 304 Galvano scanner 305 Condensing lens (fθ lens)
306 Laser light

Claims (3)

In a laser drilling method for a glass substrate, laser drilling is characterized by drilling a glass substrate at high speed with a CO ₂ laser for rough drilling, and finishing the inner wall of the hole with a UV laser. Method.   2. The laser drilling method according to claim 1, wherein a removal width by the UV laser is 100 μm or more in the inner wall finishing of the hole.   2. The laser drilling method according to claim 1, wherein in finishing the inner wall of the hole, only the inlet portion and the outlet portion of the hole are processed.