JPH07328781A - Splitting method of brittle material - Google Patents

Abstract

PURPOSE:To elevate a generating rate of initial crack at machining start point and to improve the machining speed and precision in executing splitting of brittle material with use of laser beam. CONSTITUTION:Generation of an initial crack C is executed while simultaneously irradiating two positions P1, P2 at least near the edge of a work W with laser beam, successively, while plural irradiating positions S1, S2 are controlled to the prescribed position relationship or a laser output of irradiating positions S1, S2 is controlled, the laser beam is traveled along a splitting planned line L, crack C is induced. By this method, peculiar heat stress distribution is generated between laser beam irradiating positions, its tensile stress is made larger as compared to that of irradiation of one point laser beam, splitting control is improved by controlling the generating state of stress.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaving a brittle material such as glass, ceramic or a 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 brittle materials such as glass, grinding using an abrasive or fusing by a laser beam has been known. However, according to these methods, thermal strain is generated at a processing point. However, there are drawbacks such as deterioration of the material such as grinding cracks around the processing point due to mechanical structural destruction, and loss of material due to grinding or evaporation.

Therefore, in order to solve such a problem,
A so-called laser cleaving method has been proposed in which a material is cleaved by utilizing thermal stress caused by laser beam irradiation. This method irradiates a brittle material with a laser beam, generates a microcrack due to the thermal stress generated at the irradiation position, and guides the material in the direction along the planned processing line by the thermal stress due to the laser beam. The cleaving method has the advantages that the processing energy is smaller than that of fusing using a laser beam and there is no material loss.

[0004]

By the way, according to the above-mentioned laser cutting method, the initial crack which is the starting point of processing is
Irradiating a laser beam in the vicinity of the edge of the material, it is generated by a localized concentrated stress caused by a steep temperature gradient generated between the beam center and the periphery, for example, the ambient temperature around the processing, The thermal stress (tensile stress) generated due to various conditions such as the scattering state on the surface of the material and the absorption rate of light in the material may vary, and the localized concentrated stress may not exceed the allowable stress of the material. There is a problem that the certainty of the initiation of cracks is low.

In the laser cleaving method, in order to induce a crack, the irradiation position of the laser beam is moved along the expected cleaving line, thermal stress (tensile stress) is generated behind the beam traveling direction, and stress at the tip of the crack is generated. The mechanism is such that the expansion factor exceeds the fracture toughness value of the material, but if the traveling speed of the laser beam is fast, there is a problem that the thermal stress for crack induction is not sufficient and the crack growth stops. The problems of the limit of processing speed and the reproducibility of the above-mentioned generation of initial cracks are obstacles to practical use of the laser cleaving method.

Further, in this type of laser cleaving method, when the crack is guided, the crack may deviate from the path of movement of the laser beam irradiation position and follow the crack. Therefore, there remains a problem that machining accuracy is poor. There is.

The present invention has been made in view of the above circumstances, and is a method in which, when a brittle material is cleaved by using a laser beam, the incidence of initial cracks at the starting point of processing is high,
It is also an object of the present invention to provide a cutting method capable of achieving improvement in processing speed and accuracy.

[0008]

In order to achieve the above-mentioned object, the first method of the present invention is, as shown in FIG. 1 corresponding to the embodiment, at least two points near the edge of the material W to be processed. P
It is characterized by simultaneously irradiating 1, P2 with a laser beam to generate an initial crack C.

Further, according to the second method of the present invention, as shown in FIG. 2, the crack C near the edge of the workpiece W is irradiated with a plurality of laser beams, and the output between the plurality of beams is output. It is characterized in that the crack C is guided by moving the beam irradiation positions S1 and S2 along the planned cutting line L in a state in which the position relationship between the beam irradiation position S1 and S2 is controlled.

[0010]

First, when two laser beams LB near the edge of the workpiece W are simultaneously irradiated, a peculiar thermal stress distribution as shown in Fig. 1 (b) is generated between the beam irradiation positions. ,
The tensile stress due to this thermal stress distribution becomes larger than the tensile stress when the laser beam irradiation position is one point, and as a result, the localized concentrated stress becomes a value that sufficiently exceeds the allowable stress of the material, The initial crack is surely generated.

Next, when the laser beam LB is irradiated to the position S1 in front of the tip of the crack C and the position S2 in the rear of the crack C, respectively, between the irradiation positions S1 and S2, as shown in FIG. A specific thermal stress distribution as shown in (1), 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 becomes larger than in the case of laser beam irradiation of one point. As a result, the stress intensity factor at the crack tip easily exceeds the fracture toughness value of the material. As a result, the crack progresses faster and the crack growth direction is less likely to bend with respect to the planned cleavage line L.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 is a two-axis moving stage (not shown) on which a material W to be processed 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.

The optical axes of these laser oscillators can be changed with respect to the stage, and the irradiation position of the laser beam LB on the material W to be processed is linear in the direction orthogonal to the planned cutting line L. It is possible to selectively switch to either of two points or two points on the planned cutting line L.

The processing procedure of the embodiment of the present invention is as follows.
After aligning the optical axes of the two laser oscillators with the workpiece W, the laser beams LB are aligned as shown in Fig. 1 (a).
The center of the spot is aligned with two points P1 and P2 which are symmetrical to each other with the planned dividing line L sandwiched in the vicinity of the edge of the workpiece W, and in this state, the laser beam LB is simultaneously applied to the two points on the surface of the workpiece W. Irradiation causes a crack C to occur near the edge of the workpiece W.

Assuming that there are two laser beam irradiation positions on the workpiece W in this way, between the beam irradiation positions,
A unique thermal stress distribution is generated as shown in the analysis diagram of Fig. 1 (b), and the tensile stress becomes larger than the tensile stress when the laser beam irradiation position is set to one point. Occurs in. The crack generation probability depends on various conditions such as the distance between the laser beam irradiation points P1 and P2 and the laser oscillation power. However, the probability is 100% (previously: about 90%) by experiments. ) Has been confirmed at this stage.

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

In this crack guiding process, the laser beam irradiation position is set to a position S1 in front of the tip of the crack C and a position S2 in the rear thereof, so that the position between the irradiation positions S1 and S2 is shown in FIG. 2 (b). A unique thermal stress distribution as shown in the analysis diagram of Fig. 3 is generated, and the thermal stress distribution becomes large on the front side of the crack C. That is, the tensile stress on the front side in the propagation direction of the crack C is always large, so that even if the traveling speed of the laser beam, that is, the processing speed is increased, the propagation of the crack C is not stopped, and the crack C The probability that the traveling direction bends with respect to the planned cleavage line L also decreases.

The processing speed is 30 at most in the conventional case.
Although it was about mm / s, it can be increased to 150 mm / s at the present stage, and the processing accuracy is several hundred μ.
m; Conventional → It has been confirmed at the present stage by experiments that the surface roughness can be increased to several tens of μm (surface roughness).

Here, in the above embodiment, the distance between the two points P1 and P2 of the laser beam irradiation when the initial crack is generated is determined by the material and thickness of the workpiece W, the laser output power, etc. However, if the spot diameter of the laser beam is about 2.0 mm, a suitable distance between the two points is about 3.0 mm to 3.6 mm. Further, the distance between the laser beam irradiation positions S1 and S2 at the time of guiding the crack C may be the same as that at the time of the initial crack generation.

Further, as shown in FIG. 2C, the laser beam irradiation positions S1 and S2 at the time of guiding the cracks may be symmetrical to each other with the planned splitting line L sandwiched between them near the tip of the crack C. Good. In this case, the thermal stress distribution as shown in the analysis diagram of FIG. 2 (d), that is, the thermal stress distribution equivalent to that of FIG. 1 (b) occurs and the tensile stress near the crack tip increases, so that the beam irradiation position S1, Even if S2 has such a positional relationship, the same effect as above can be achieved.

In the method of the present invention, the laser beam irradiation position on the material to be processed is not limited to two, but may be any number of three or more. If the number of irradiation positions is increased, By selecting the positional relationship of each irradiation point appropriately, it is possible to generate a thermal stress distribution for further increasing the tensile stress, which results in a better effect, namely, the processing speed.
It is also possible to expect an effect that the accuracy and the like are further improved as compared with the previous embodiment.

The method of the present invention can, of course, be applied to the processing of quartz and other brittle materials such as semiconductor materials in addition to glass and alumina ceramics. As the 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 peculiar thermal stress distribution is generated near the irradiation position. As a result of the tensile stress becoming larger than before, the probability of initial cracking increases and the processing speed
Both accuracy is improved. This makes it possible to put the laser cleaving method to practical use.

Further, the laser beam irradiation position on the material is set to 2
By setting the points (multi-points), sufficient processing speed and accuracy can be obtained even if the temperature distribution due to beam irradiation is suppressed to be lower than in the case of normal single point laser beam irradiation.
This also has the advantage that the influence of heat on the material to be processed can be reduced.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of the same embodiment.

[Explanation of symbols]

W Work material L Planned cutting line LB Laser beam P1, P2 Point to irradiate laser beam at initial crack generation S1, S2 Crack-induced laser beam irradiation position C Crack

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunichi Maekawa 1-15 Kasugaoka, Itami City, Hyogo Prefecture (72) Inventor Toshihiro Okiyama 1174-22 Ogiri, Mikunino Town, Hyogo Prefecture (72) Hideyuki Shirahama Nagasaki City, Nagasaki Prefecture Hiramachi 199-3 (72) Inventor Toshiyuki Yokoyama 1011 Mijo-cho, Omura-shi, Nagasaki Mijo Apertoy-206 (72) Inventor Hidenobu Onita 955-1 Mijo-cho, Omura-shi, Nagasaki

Claims (2)

[Claims] 1. A laser beam is irradiated near the edge of a brittle material, and a crack is generated by the thermal stress generated at that position,
In the method of cleaving a material, a method of cleaving a brittle material is characterized in that at least two points near an edge of a material to be processed are simultaneously irradiated with a laser beam to generate the crack. 2. A crack is generated by irradiating a laser beam in the vicinity of the edge of a brittle material with a laser beam, irradiating the laser beam in the vicinity of the crack, and moving the irradiation position to guide the crack along a planned cutting line. In the method of cleaving the material by irradiating a crack with a plurality of laser beams near the edge of the material to be processed, and controlling the output and the positional relationship between the plurality of beams, these beams A method for cleaving a brittle material, which comprises inducing the crack by moving an irradiation position along the planned cleavage line.