JP2000061667A - Laser beam machining method for glass and glass formed parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly machine fine deep holes on glass without causing a crack with YAG laser beam. SOLUTION: Pulsed oscillation YAG laser beams are radiated to an object to be machined that is made of glass containing a component high in YAG laser beam absorptivity. The irradiation energy of YAG laser beam is set at a prescribed threshold or higher in accordance with the high YAG laser beam absorptivity component contained in the glass to be used. The focal position of the laser beam is set near the middle between the front and the rear faces of the object to be machined, more suitably in the part lower than such middle position, dispersing the irradiation energy uniformly in the thickness direction rather than concentrating in a specific position, and growing a through hole from both front and rear faces. Thus, simplification of the machining process and operation can be contrived as well as reduction in the machining time and cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method capable of forming fine holes, particularly through holes, in a transparent material such as glass by using laser light.

[0002]

2. Description of the Related Art Conventionally, in order to make fine holes in a transparent material such as glass, a processing method using a rotary grindstone, a drill, ultrasonic waves, or a mechanical processing such as a microblast method for spraying abrasive grains. Methods and chemical methods such as wet etching using a solution are generally adopted.
Further, recently, energy beam processing for irradiating an electron beam, an ion beam or a laser beam has been performed.

In laser processing, a gas laser such as an excimer laser or a CO 2 laser, which is generally ultraviolet light, is used. Furthermore, there is a research report that processing with visible light or near infrared light is possible by using a laser with a high peak output called a giant pulse. On the other hand, it is said that the YAG laser, which is relatively inexpensive, has good operability, and is easy to handle, is used for a wide range of purposes, and therefore cannot be processed because it generally has a low absorptance with respect to a glass material.

According to a paper by Junichi Ikeno et al. On YAG laser, “YAG laser processing of quartz glass using solution” (Precision Engineering Journal 55/2/1989, pp. 93-98), the solution containing metal ion is When it is dropped on the surface of a transparent quartz glass plate of 1.5 mm, or brought into contact with the back surface and irradiated with a pulsed YAG laser, the solution absorbs the laser light and generates high heat, which melts the quartz glass and penetrates it. It has been reported that holes can be formed. Further, in the same paper, in the case of general glass containing impurities, it is described that the through hole can be similarly laser-processed without applying the above-mentioned solution by simply applying a magic ink on the surface thereof.

However, according to another report by Ikeno et al. ("YAG laser processing of crystallized glass", 1997 Autumn Meeting of Precision Engineering Society, Annual Meeting, 232), the focus was on the surface of crystallized glass. When the laser light is irradiated together, the molten portion is formed inside the glass, and thus the crack is generated as soon as the output exceeds the threshold value, and the glass is broken.
Therefore, by applying a pigment to the glass surface and irradiating it with pulsed YAG laser light to form a fused portion on the surface and scattering and removing it to the outside, the problem of this cracking is eliminated, and the thickness is increased. Through holes are formed in a 4 mm crystallized glass plate.

Regarding this processing mechanism, Junichi Ikeno's paper "Three-dimensional drilling of glass using YAG laser" (Laser Society Research Group Report, No. RTM-98-4, Laser Society of Japan, January 1998) (Published 30th, pages 23-27)
According to the above, since the work-affected layer is observed in the work hole,
It is analyzed that the work-affected layer is formed when the pigment absorbs the YAG laser and the glass is melted, and the work-affected layer absorbs the next laser beam to proceed with the working.

[0007]

However, the above-mentioned conventional processing method has the following problems. First, in a mechanical processing method such as the microblast method, there is a limit to miniaturization of the processed hole, and chipping, that is, a minute chip is likely to occur around the opening of the processed hole, which may cause quality problems. In wet etching, the usable etching solution may be limited depending on the material of the work piece, and it is difficult to form a fine deep hole, resulting in a low processing speed. Similarly, a processing apparatus such as an electron beam or an ion beam is generally expensive and has a very low processing speed.

In the case of laser processing, the excimer laser has problems that the device is expensive, the running cost is high, and the maintainability of the device is poor. CO2 Since the laser performs thermal processing and has a large output, it is likely to cause cracks due to thermal strain over a wide range around the processed portion, which may impair the quality, and the wavelength is long, so the light-collecting property is low, Not suitable for fine processing. Similarly, the giant pulse laser is expensive and its peak output is too high, which may damage the optical system.

The YA described in the above paper by Ikeno et al.
In G laser processing, since it is necessary to bring a solution into contact with the surface of a workpiece or to apply a pigment or the like, the processing steps and work are complicated and troublesome, and time and labor are required, resulting in reduced productivity and cost. There is a risk of rising.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, using a YAG laser which is relatively inexpensive and easy to handle, and simplifies the processing steps and work and the processing time. The present invention provides a laser processing method capable of directly processing fine and deep holes in glass without cracks without coating a solution or a pigment on the surface of the laser.

[0011]

Means for Solving the Problems The present inventor has found that when a glass is irradiated with a pulsed YAG laser and the irradiation energy exceeds a certain threshold value, a through hole is formed in the glass without using the solution or pigment. It has been found that can be directly formed.

Therefore, according to the present invention, it comprises a process of irradiating a work piece made of glass with a pulsed YAG laser, wherein the glass contains a component having a high YAG laser absorptivity, and Provided is a laser processing method for glass, which is characterized by setting irradiation energy to a predetermined threshold value or more.

The component having a high YAG laser absorptivity contained in the glass of the workpiece absorbs the irradiation energy exceeding the threshold value, generates high heat, and melts the surrounding material, so that it is relatively easily volatilized. The components evaporate first and the composition of the melted portion changes, and the work-affected layer absorbs the laser light to proceed with the working and form a through hole. Further, in the pulsed YAG laser, since the melt is removed during the laser light irradiation, thermal strain does not remain, and as a result, cracks are unlikely to occur even in glass, which is a hard brittle material.

As such a glass, a glass in which the above-mentioned work-affected layer is formed by laser irradiation can be used, and a glass containing impurities is particularly preferable. Specifically, commercially available soda lime glass, hard glass (excluding quartz glass), crystal glass and the like are included. Components such as alumina contained in these glass materials easily absorb the YAG laser and generate high heat necessary for drilling by laser irradiation. Therefore, a solution or pigment is used on the glass surface as in the above-mentioned conventional laser processing. No need.

The threshold of the irradiation energy of the pulse oscillation YAG laser is determined by the pulse output of the laser, and the pulse output can be adjusted by the pulse width and the peak output. The specific threshold is the composition of the glass of the workpiece,
It depends on the type and amount (ratio) of the high YAG laser absorptance component contained therein.

When the focus position of the YAG laser is set near the middle of the surface and the back surface of the workpiece, the irradiation energy is dispersed in the thickness direction without being concentrated at a specific position, and the front and back surfaces are It is preferable because the through holes grow.
Especially, if the position is set lower than the intermediate position between the front surface and the back surface, the irradiation energy is more evenly distributed, which makes it possible to perform hole drilling with a more uniform hole diameter and with less cracks. .

Further, for example, by adjusting the beam diameter before focusing, the focal length of the focusing lens, etc., the irradiation conditions of the YAG laser are set so that both the front surface and the back surface of the workpiece are melted. It is advantageous that the drilled holes grow from both the front and back surfaces, and the drilling can be performed more efficiently, and the drilling can be performed more efficiently and without substantially or adversely affecting the portion other than the worked portion.

According to one embodiment, the work-affected layer is formed on the glass by first irradiating it with a first YAG laser with an irradiation energy equal to or higher than a first threshold value, and then the first The work-affected layer is melted and removed by irradiating the second YAG laser with an irradiation energy which is higher than the second threshold and which is higher than the second threshold. The first YAG laser does not process the through-holes, and it suffices if the work-affected layer can be efficiently formed. Therefore, the good or bad of the light converging property does not become a problem.
On the other hand, since the second YAG laser is used for finally processing the through hole, it is preferable to use laser light having a good converging property at a wavelength that is easily absorbed by the work-affected layer.

Further, according to the present invention, there is provided a glass molded product processed by the above-described laser processing method for glass.

[0020]

EXAMPLE Using the laser processing method of the present invention, a thin plate (thickness 1 mm) of borosilicate glass, which is a kind of hard glass and marketed under the trade name of "Pyrex" (trademark), was subjected to fine perforation processing. . First, the state of the machined hole with respect to the change of the laser irradiation energy was tested.

A pulsed YAG laser was used under the following processing conditions. Laser wavelength: 1064 nm Spread angle: 5 mrad Expander: × 3 Condenser lens: f50 mm Minimum beam diameter: φ0.25 mm Focus angle: 9.2 deg Irradiation pulse number: 1 Laser beam pulse width is 500 μs, 750 μs, 100
The peak output is 3.70 kW and 5.4 in 3 steps of 0 μs.
The power output of irradiation energy was determined as shown in the following table by changing the power in four steps of 4 kW, 7.70 kW, and 10.08 kW. The focus position of the laser light was fixed at an intermediate position between the front surface and the back surface of the glass thin plate.

[0022]

[Table 1]

(When the pulse width is 500 μs) As a result,
With a pulse width of 500 μs, the peak output is 10.08 kW
(Pulse output 5.04 J / pulse)
As shown in (A), the back surface 2 to the front surface 3 of the glass thin plate 1 are
The cylindrical hole 4 grew to a depth of about 1/3 of the plate thickness, but a large crack 5 was generated from the bottom of the processed hole 4 toward the surface, and the surface 3 was not processed at all. .
However, the formation of the work-affected layer 6 was recognized around the work hole 4 and from the bottom to the position where it did not reach the surface. As described above, the work-affected layer 6 can be easily confirmed by an optical microscope because the refractive index is changed at the portion where the composition of the glass, which is volatile, is first evaporated and the composition thereof is changed. It was

Peak output 7.70 kW (pulse output 3.
At 85 J / pulse, as shown in FIG. 1 (B), a slight circular hole 4 was formed in the back surface 2 of the glass thin plate, and only a crack 5 was formed from the bottom to the surface 3 side. A work-affected layer 6 was similarly formed around the circular hole 4 and from its bottom to the surface. With a peak output or irradiation energy smaller than this, the glass sheet was not processed on both the front surface and the back surface. However, at the peak output of 5.44 kW (pulse output of 2.72 J / pulse), as shown in FIG. 1C, formation of a small work-affected layer 6 was recognized on the back surface 2 side of the glass thin plate.

(When pulse width is 750 μs) Pulse width 7
At 50 μs, the through hole was not processed in any case. Peak output 10.08kW (pulse output 7.56J
2 / A), as shown in FIG. 2 (A), the cylindrical hole 4 grew from the back surface 2 of the thin glass plate 1 to a depth exceeding half of the plate thickness, but a large hole from the bottom of the processed hole 4 to the front surface 3 Cracks 5 were generated, and cracks were also found around the opening of the processed hole on the back surface of the glass thin plate. Formation of a work-affected layer 6 reaching the surface from the periphery of the processed hole 4 and its bottom was observed.

Peak output 7.70 kW (pulse output 5.
78 J / pulse), as shown in FIG. 2 (B), the pulse width is 500 μs and the peak output is 1 as shown in FIG. 1 (A).
Similar to the case of 0.08 kW (pulse output 5.04 J / pulse), a cylindrical hole 4 is formed from the back surface 2 of the glass thin plate to a depth of about 1/3 of the plate thickness, and the bottom surface of the hole 4 A large crack 5 up to 3 was generated. Also in this case, the work-affected layer 6 reaching the surface from the periphery of the processed hole 4 and the bottom thereof was similarly formed.

Peak output 5.44 kW (pulse output 4.
08J / pulse), as shown in FIG. 2 (C), the pulse width is 500 μs and the peak output is 7.
As with the case of 70 kW (pulse output of 3.85 J / pulse), a small number of circular holes 4 and cracks 5 and a work-affected layer 6 that did not reach the surface 3 were formed on the glass thin plate rear surface 2 side. Peak output 3.70 kW (pulse output 2.78J
/ Pulse), as shown in FIG. 2D, the glass thin plate 1 was not processed on both the front surface and the back surface, but it was confirmed that a slight work-affected layer 6 was formed on the back surface side.

When the pulse width is 1000 μs, the peak output is 10.08 kW when the pulse width is 1000 μs.
(Pulse output 10.08 J / pulse)
As shown in (A), the through hole 4 was formed. Further, the work-affected layer 6 was formed around the through hole 4. However, at lower peak powers, through holes could not be formed.

At 7.70 kW, as shown in FIG. 3 (B), the pulse width is 750 μs and the peak output is 10.08 kW (pulse output 7.56 J / pulse) as shown in FIG. 2 (A). A cylindrical processed hole 4 and a crack 5 reaching the surface 3 of the thin glass plate were formed on the surface. Further, the work-affected layer 6 reaching the surface from the periphery of the processed hole 4 and its bottom.
Were similarly formed.

Peak power 5.44 kW and 3.70 kW
At (pulse output 5.44 J / pulse and 3.70 J / pulse), as shown in FIGS. 3 (C) and 3 (D), respectively, the pulse width of 500 μm in FIGS.
s, peak outputs of 10.08 kW and 7.70 kW (pulse output of 5.04 J / pulse and 3.85 J / pulse), the processed holes 4, cracks 5 and work-affected layer 6 were formed to the same extent.

Judging from the above results, whether or not machining is possible and the growth of machined holes differ depending on the magnitude of the irradiation energy obtained by combining this with the pulse width, not just the peak output (or peak power density). It has been confirmed that the through hole can be formed when the threshold value (in the present embodiment, the pulse output of 10.08 J / pulse) is exceeded.

Next, a pulsed YAG laser is also used, pulse width is 1000 μs, and peak output is 10.08 k.
With W, make the pulse output constant at 10.08 J / pulse,
Fine drilling was performed on a 1 mm thick Pyrex glass sheet while changing the focal position of laser light. Other laser processing conditions are as follows. Laser wavelength: 1064nm Spread angle: 5mrad Expander: None Focusing lens: f50mm Minimum beam diameter: φ0.25mm Focusing angle: 9.2deg

As shown in FIGS. 4 (A) and 4 (B),
The focal position of the laser light 7 is divided into 10 evenly in the thickness direction of the glass thin plate 1 from the position a near the front surface to the position b near the back surface by shifting the position of the condenser lens 8, and the position a near the surface is set. The displacement amount x was set to 1 to 10 as the reference position. As a result, the displacement amount x = 2 from the reference position.
In the range up to, the cylindrical hole grew from the back surface side to a depth exceeding half the plate thickness, but only a crack from the bottom of the hole to the surface was generated, and the hole did not penetrate.

Through holes could be formed in the range of displacement x = 3 to 9. In particular, at positions of displacement amounts x = 7 and 8 which exceed the intermediate position between the front surface and the back surface of the thin glass plate, as shown in FIG. 5, a substantially cylindrical processed hole 4 having a substantially uniform hole diameter and no cracks is formed. did it. At other positions, the diameters of the through holes were nonuniform, and cracks were found inside the glass and around the openings of the holes.

At a position near the back surface of the glass thin plate where the displacement amount was x = 10, a conical deep hole grew from the front surface to the vicinity of the back surface, but the back surface formed a round recess and did not penetrate. Moreover, a large crack was generated in the vicinity of the recess on the back surface.

Judging from this result, when the focal position is set near the middle of the front surface and the back surface of the thin glass plate so that the irradiated laser light energy is uniformly dispersed in the thickness direction of the thin glass plate, a crack is generated. Such a rapid temperature rise inside the glass plate is avoided, and the processed hole grows and penetrates from both the front surface and the back surface, which is preferable. In particular, it is convenient to focus the laser light below the intermediate position because crack-free through holes having substantially the same hole diameter are formed.

In this embodiment, the beam diameter of the laser light is 6 mm.
However, when the beam diameter was expanded to 12 mm, a crack was generated at the same focal point, and the melt was ejected from this crack. This is because the energy density of the laser light is low due to the thick beam on the glass surface,
While it is difficult for the glass to soften, at the focal position inside the glass, the energy density is high, so the glass melts. It is considered that this is because the melt inside the glass cannot be smoothly eluted to the outside and stress is generated.

Further, in the vicinity of the openings of the respective through holes formed with the displacement amount x = 3 to 9, it was observed that the molten material was scattered and adhered or raised. This indicates that the temperature of the melt generated by laser irradiation in this example is relatively low. This melt could be easily removed by polishing both surfaces of the glass sheet 1 with an appropriate abrasive.

A molten portion 9 was raised around the opening of the processed hole 4 shown in FIG. 5, and the composition of this molten portion was analyzed.
The results shown in are obtained. That is, the composition ratio of the Al component that constitutes alumina, which easily absorbs the YAG laser light, has increased from about 2.3% of the original base material to about 4.4% on average, which is nearly double the YAG laser light. Si that does not absorb increases from about 93.1% to about 94.7% on average, and Na, which has a lower melting point and is easier to evaporate than Al, has an average value of about 4.5%.
From about 0.8%.

This is because the alumina contained in the glass material used absorbs the irradiation energy of laser light to generate high heat in the melting portion, whereby Na having a low melting point evaporates first, and the composition of the material itself. Indicates that a work-affected portion was formed. Due to this composition change, the work-affected portion has a higher alumina content and a higher laser absorptivity than the base material, so that the working speed is faster than other portions and the hole growth is promoted. It proves the processing mechanism.

In this embodiment using Pyrex glass as described above, by irradiating a laser beam having a pulse output or energy equal to or higher than a predetermined threshold value, alumina contained in the glass material absorbs the laser beam to generate high heat. Generated and surrounding materials are melted to evaporate easily volatilized components such as Na first, the composition is changed to form a work-affected layer, and this work-affected layer absorbs laser light to process the through hole. It became clear that it could be done. Moreover, in the pulsed YAG laser, since the molten material is removed during the laser light irradiation, thermal strain does not remain, and as a result, crack-free and high-quality drilling can be realized even for glass, which is a hard brittle material. .

[0042]

According to the present invention, a pulsed YAG laser is used as described above, and even if it is a commercially available general glass or the like, a high laser light absorptivity component contained in it is used to achieve high heat resistance. Since it is possible to directly perform microscopic drilling without cracks in the glass, the processing steps and operations can be simplified, and the processing time and the processing cost can be reduced.

[Brief description of drawings]

1A to 1C are peak widths of 10.08 kW and 7.70 kW at a pulse width of 500 μs, respectively.
It is sectional drawing which shows the processing state at the time of irradiating a pulse oscillation YAG laser as 5.44 kW.

2A to 2D show a peak output of 10.08 kW, 7.70 kW, and a pulse width of 750 μs, respectively.
It is sectional drawing which shows the processing state at the time of irradiating a pulse oscillation YAG laser as 5.44 kW and 3.70 kW.

3A to 3D show a peak output of 10.08 kW and 7.70 kW at a pulse width of 1000 μs.
It is sectional drawing which shows the processing state at the time of irradiating a pulse oscillation YAG laser as 5.44 kW and 3.70 kW.

FIGS. 4A and 4B are diagrams showing a state in which the focal position of the laser light is adjusted to a position near the front surface and a position near the back surface of the glass thin plate, respectively.

FIG. 5: Pulse width 1000 μs, peak output 10.08
It is sectional drawing which shows the processed hole at the time of irradiating a pulse oscillation YAG laser with the amount of displacement x = 8 of the focal position of laser light in kW.

FIG. 6 is a diagram showing a change in composition of a fusion zone.

[Explanation of symbols]

1 glass sheet 2 back side 3 surface 4 processed holes 5 cracks 6 Processed alteration layer 7 laser light 8 Condensing lens 9 Melting part

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01S 3/00 H01S 3/00 B (72) Inventor Issei Umezu 3-3-5 Yamato, Suwa City, Nagano Prefecture No. Seiko Epson Corporation F-term (reference) 3C060 AA08 CF16 4E068 AF01 CA02 CA03 CA11 CF01 DB13 5F072 AB01 JJ09 JJ12 RR01 SS06 YY06

Claims (9)

[Claims] 1. A process of irradiating a work piece made of glass with a pulsed YAG laser, wherein the glass contains a component having a high YAG laser absorptance, and
A laser processing method for glass, wherein irradiation energy of an AG laser is set to a predetermined threshold value or more. 2. The laser processing method for glass according to claim 1, wherein the glass contains impurities. 3. The laser processing method for glass according to claim 1, wherein the threshold value of the irradiation energy is determined by the pulse output of the YAG laser. 4. The laser processing method for glass according to claim 3, wherein the pulse output of the YAG laser is adjusted by the pulse width and the peak output. 5. The glass laser processing method according to claim 1, wherein the focus position of the YAG laser is set near the middle of the front surface and the back surface of the workpiece. 6. The laser processing method for glass according to claim 5, wherein the focus position of the YAG laser is set below an intermediate position between the front surface and the back surface of the workpiece. 7. The glass laser processing method according to claim 1, wherein irradiation conditions of the YAG laser are set so that both the front surface and the back surface of the workpiece are melted. . 8. The Y with irradiation energy above a first threshold value.
After the work-affected layer is formed on the glass by irradiating the AG laser, the work-affected layer is melted by irradiating the YAG laser with an irradiation energy which is larger than the first threshold and is equal to or higher than a second threshold. The laser processing method for glass according to claim 1, wherein the laser processing is performed. 9. A glass molded article, which is processed by the laser processing method for glass according to any one of claims 1 to 8.