JP3210934B2 - How to cut brittle materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a brittle material such as glass, ceramic or semiconductor material by utilizing thermal stress generated by irradiating the material with a laser beam.

[0002]

2. Description of the Related Art Conventionally, as a method of cutting a brittle material such as glass, there are grinding using an abrasive or fusing by a laser beam. However, according to any of these methods, thermal strain occurs at a processing point. There are drawbacks in that the material is deteriorated, for example, grinding cracks and the like are generated around the processing point due to mechanical structure destruction and the like, and the loss of material due to grinding or evaporation is inevitable.

In order to solve such a problem,
A so-called laser cleaving method has been proposed in which a material is cleaved using thermal stress due to laser beam irradiation. This method irradiates a brittle material with a laser beam, generates micro-cracks due to the thermal stress generated at the irradiation position, and induces the cracks in the direction along the processing line by the thermal stress of the laser beam. The method of cutting has the advantages that the processing energy is small and the material is not lost, as compared with the cutting using a laser beam.

[0004]

By the way, according to the above-described laser cutting method, an initial crack which is a starting point of processing is formed.
By irradiating the laser beam near the edge of the material, it is caused by local concentrated stress caused by a steep temperature gradient generated between the beam center and the periphery, for example, ambient temperature around the processing, Thermal stress (tensile stress) generated due to various conditions such as the scattering state on the material surface and the light absorption rate in the material may fluctuate, and the localized concentrated stress may not exceed the allowable stress of the material. There is a problem that the reliability of the generation of the initial crack is low.

In the laser cutting method, the crack is induced by moving the irradiation position of the laser beam along the expected cutting line, generating a thermal stress (tensile stress) behind the beam traveling direction and causing a stress at the tip of the crack. The mechanism is used to make the expansion factor exceed the fracture toughness of the material.However, if the laser beam travels at a high speed, there is a problem that the thermal stress for crack induction is not sufficient and the crack growth stops. The problems of the processing speed limit and the reproducibility of the above-mentioned initial crack generation hinder the practical use of the laser cutting method.

Further, in this type of laser cutting method, when a crack is induced, the crack may shift from the movement path of the irradiation position of the laser beam and follow the same, so that the problem of poor machining accuracy remains. I have.

[0007] The present invention has been made in view of such circumstances, and when performing the cutting of a brittle material using a laser beam, a method of generating a high initial crack rate at the processing starting point,
It is another object of the present invention to provide a cutting method capable of achieving an improvement in processing speed and accuracy.

[0008]

To achieve the above object, according to an aspect of the first method of the present invention, as shown in FIG. 1, corresponding to the embodiment, in the edge vicinity of the work piece W, and fracture Scheduled line
The laser beam is placed on both sides (two points P1, P2) of L
It is characterized by irradiating LB at the same time to generate an initial crack C.

The second method of the present invention, as shown in FIG. 2, irradiates a plurality of laser beams near a crack C near an edge of a workpiece W, and irradiates the plurality of laser beams. The positions of the laser beams are controlled and the beam irradiation positions S1 and S2 are moved along the planned cutting line L while the positions are set at positions in front of and behind the tip of the crack C. It is characterized by performing guidance.

[0010]

First, when the laser beam LB at two points near the edge of the workpiece W is irradiated simultaneously, a unique thermal stress distribution as shown in FIG. ,
The tensile stress due to this thermal stress distribution becomes larger than the tensile stress when the laser beam irradiation position is set to one point, and as a result, the local concentrated stress sufficiently exceeds the allowable stress of the material, An initial crack is definitely generated.

Next, when a laser beam LB is applied to the front position S1 and the rear position S2 of the tip of the generated crack C , respectively, the distance between the irradiation positions S1 and S2 is as shown in FIG.
A unique thermal stress distribution as shown in (b), that is, a thermal stress distribution in which the front side of the crack C is large occurs, and the tensile stress on the front side is larger than that in the case of laser beam irradiation at one point. Become. As a result, the stress intensity factor at the tip of the crack tends to exceed the fracture toughness value of the material. As a result, the growth of the crack is accelerated and the direction of growth of the crack is less likely to bend with respect to the planned cutting line L.

[0012]

FIG. 1 is an explanatory view of an embodiment of the present invention. First,
The apparatus used for carrying out the method of the present invention includes a biaxial moving stage (not shown) on which a workpiece W such as glass or alumina ceramic is placed, and two points on the surface of the material placed on this stage. Two laser oscillators (not shown) for simultaneously irradiating the laser beam LB are provided.

In these laser oscillators, the optical axis can be changed with respect to the stage, and the irradiation position of the laser beam LB on the workpiece W is set on the line in a direction orthogonal to the planned cutting line L. It is possible to selectively switch to either one of two points or two points on the planned cutting line L.

The working procedure of the embodiment of the present invention is as follows.
By aligning the optical axes of the two laser oscillators and the workpiece W, as shown in FIG.
The center of the spot is aligned with two points P1 and P2 that are symmetrical with each other across the planned cutting line L near the edge of the workpiece W. In this state, the laser beam LB is simultaneously applied to two points on the surface of the workpiece W. Irradiation generates a crack C near the edge of the workpiece W.

Assuming that the laser beam irradiation position on the material W to be processed is two, the distance between the beam irradiation positions is as follows.
An unusual thermal stress distribution occurs as shown in the analysis diagram of Fig. 1 (b), and the tensile stress is larger than the tensile stress when the laser beam irradiation position is set to one point. Occurs. The probability of the occurrence of the crack depends on various conditions such as the distance between the laser beam irradiation points P1 and P2 and the oscillation power of the laser. ) Has been confirmed at this stage.

Next, by changing the optical axis of the laser oscillator, as shown in FIG. 2A, the irradiation position of the laser beam LB is set to two points along the planned cutting line L. With the output of the LB controlled, the irradiation positions S1 and S2 of each laser beam LB are moved along the planned cutting line C by the movement of the stage to induce a crack C generated near the edge of the material W. go.

In the crack induction process, the irradiation position of the laser beam is set to the position S1 in front of the tip of the crack C and the position S2 behind, so that the irradiation position between these irradiation positions S1 and S2 is as shown in FIG. A unique thermal stress distribution as shown in the analysis diagram of FIG. 1 is generated, and the thermal stress distribution is large on the front side of the crack C. In other words, the tensile stress on the front side in the direction of propagation of the crack C is always large, so that the propagation of the crack C does not stop even if the traveling speed of the laser beam, that is, the processing speed is increased, and the crack C The probability that the direction of progress is bent with respect to the planned cutting line L is also reduced.

The processing speed is conventionally at most 30.
mm / s, it can be increased to 150 mm / s at this stage.
m: Conventionally, it has been confirmed at this stage by experiments and the like that the height can be increased to several tens μm (surface roughness).

Here, in the above embodiment, the distance between the two points P1 and P2 of laser beam irradiation when an initial crack is generated depends on the material and thickness of the material W to be processed, the output power of the laser, and the like. The distance between the two points is suitably about 3.0 mm to 3.6 mm if the spot diameter of the laser beam is about 2.0 mm. Further, the distance between the laser beam irradiation positions S1 and S2 when the crack C is induced may be the same as when the initial crack was generated.

Although not outside the scope of the present invention, the laser beam irradiation positions S1 and S2 at the time of crack induction are shown in FIG.
As shown in (1), a method is also conceivable in which positions near the tip end of the crack C are symmetrical with respect to the planned cutting line L. In this case, a thermal stress distribution occurs as shown in the analysis diagram of FIG.

Here, in the method of the present invention, the laser beam irradiation position on the material to be processed is not limited to two points but may be three.
Any number of points or more may be used, and if the number of irradiation positions is increased, if the positional relationship between the irradiation points is appropriately selected,
It is possible to generate a thermal stress distribution for further increasing the tensile stress, and thereby, it is possible to expect a more excellent effect, that is, an effect that the processing speed and accuracy are further improved as compared with the previous embodiment.

The method of the present invention can of course be applied to the processing of other brittle materials such as glass and alumina ceramics, as well as quartz and semiconductor materials. As a laser oscillator to be used, a CO ₂ laser, a YAG laser, or the like is appropriately selected depending on the material of the processing material.

[0023]

As described above, according to the method of the present invention, since at least two points on the surface of the material to be processed are irradiated with the laser beam, a unique thermal stress distribution occurs near the irradiation position. As a result, the tensile stress becomes larger than before, so that the probability of initial cracks
The accuracy is improved together. Thereby, the practical use of the laser cutting method can be achieved.

The irradiation position of the laser beam on the material is set at 2
By setting the number of points (multiple points), sufficient processing speed and accuracy can be obtained even if the temperature distribution due to beam irradiation is suppressed lower than in the case of ordinary one-point laser beam irradiation.
This also has the advantage that the effect of heat on the material to be processed can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of the method of the present invention.

FIG. 2 is an explanatory view of the embodiment.

[Explanation of symbols]

W Material to be processed L Expected line of cut LB Laser beam P1, P2 Point of laser beam irradiation at the time of initial crack generation S1, S2 Laser beam irradiation position of crack induction C Crack

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shunichi Maekawa 1-15 Kasugaoka, Itami-shi, Hyogo (72) Inventor Toshihiro Okiyama 1174-22, Gokunino-cho, Hyogo Prefecture, Japan (72) Inventor Hideyuki Shirahama, Nagasaki 199-3 Hiramachi (72) Inventor Toshiyuki Yokoyama 1011 Misaki-cho, Omura-city, Nagasaki Pref. Japanese Unexamined Patent Publication No. 54-153745 (JP, A)

Claims (2)

(57) [Claims] 1. A laser beam is applied to the vicinity of an edge of a brittle material, and a crack is generated by thermal stress generated at the position.
In the method of cutting the material, near the edge of the material to be processed
And cutting the brittle material by simultaneously irradiating a laser beam to positions on both sides of the planned cutting line . 2. A crack is generated by irradiating a laser beam near an edge of the brittle material, and a laser beam is irradiated near the crack. The irradiation position is moved to guide the crack along a predetermined cutting line. In the method of cleaving the material by performing, a plurality of laser beams are irradiated near the crack near the edge of the material to be processed, and the irradiation positions of the plurality of laser beams are set to positions in front of and behind the crack tip. And a method for cleaving a brittle material, wherein the cracks are induced by moving the irradiation positions of the laser beams along the planned cleavage line while controlling the output of each laser beam.