RU2582181C1 - Method for laser controlled thermal cleavage of sapphire plates - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to methods of cutting of fragile nonmetallic materials, particularly, of sapphire plates, by pulse laser light with a wave length of 1064 nanometers. Invention can be used in various engineering fields and technologies for wasteless and high-precision cutting (thermal splitting) of sapphire plates. Method of controlled laser thermal splitting of sapphire plates includes directing of a laser beam from a pulse solid-state Nd: YAG laser onto the surface of a sapphire plate. Beforehand, energy absorbing graphite layers are deposited on both sides of a sapphire plate in the direction of cutting, then the cutting line is heated with laser radiation with a pulse duration of 50-100 ns and average power of 80-100 W, and a separating through crack is formed in the material.

EFFECT: invention is aimed at solving the task of increasing efficiency and quality of cutting.

1 cl, 3 dwg

Description

The invention relates to methods for cutting brittle non-metallic materials, in particular sapphire wafers using pulsed laser radiation with a wavelength of 1064 nm. The invention can be used in various fields of engineering and technology for waste-free and high-precision cutting (thermal cracking) of sapphire plates.

The main methods for cutting sapphire plates are cutting with diamond disks with an external cutting edge, scribing substrates (face of a diamond pyramid, an ultraviolet laser), laser-controlled thermal cracking.

A known method of cutting sapphire wafers using ultraviolet laser radiation (Patent US 6580054 B1, V23K 26/03 V, 2003). Cutting involves the preliminary application of a shallow cut on the surface of the substrate using an ultraviolet laser with a wavelength of 150-560 nm and subsequent breaking. The presented method is based on the use of solid-state Nd: YVO ₄ or Nd: YAG lasers. The overlap of laser pulses during processing is from 50 to 99%. When cutting, the diameter of the laser spot on the surface of the sapphire plate is from 5 to 15 μm, and the speed of movement of the laser beam over the surface can vary in the range of 2-10 mm / s.

A common feature of the analogue, which coincides with the essential features of the proposed method, is the use of laser radiation from a solid-state Nd: YAG laser for cutting sapphire wafers at the same speed of movement of the laser beam.

The disadvantages of this method are the presence of an additional operation of mechanical breaking and low quality of the edges of the plate after laser cutting. In addition, the effective use of this laser cutting method is limited by the thickness of the substrate and is 80-200 microns.

A known method of cutting plates of brittle materials (RF Patent No. 2404931, IPC С03В 33/09, 2009), including applying a local cut on the edge of the workpiece with ultraviolet laser radiation, heating the cutting line with a laser elliptic CO ₂ laser beam and subsequent cooling of the heating zone using refrigerant (air-water aerosol) during relative movement of the plate and the laser beam with the refrigerant.

A common feature of the analogue, which coincides with the essential feature of the proposed method, is the implementation of laser-controlled thermal cracking of brittle non-metallic materials with the formation of a separating crack in the material.

The disadvantages of the analogue are the following operations: the need to apply local incisions on the edge of the workpiece, the need to cool the heating zone with the help of a refrigerant during relative movement of the plate and the laser beam.

The closest to the proposed invention in terms of technical nature and the achieved result (prototype) is a method of cutting transparent non-metallic materials (RF Patent No. 2226183, IPC S03B 33/00, V23K 26/38, 2004) by directing the laser beam from a pulsed laser, focusing laser radiation on the surface of the sample or in its thickness and the formation of a defect at the focal point, and then the application of mechanical force to the surface of the sample. Pulse laser radiation is used with a wavelength lying in the transparency region of the material, a pulse duration of 10-100 ps and an energy in pulse sufficient to produce a breakdown in the focus area.

A sign of the prototype, which coincides with the essential features of the proposed method, is the use of pulsed radiation from a solid-state Nd: YAG laser with a wavelength of about 1 μm for cutting sapphire wafers.

The disadvantage of the prototype is an additional technological operation, which consists in mechanically breaking the sample, which leads to low quality cutting lines, and there are also restrictions on the thickness of the material (from a few microns to 300-500 microns).

The claimed invention is aimed at solving the problem of increasing the efficiency and quality of cutting sapphire plates by eliminating the operations of mechanical breaking, applying preliminary cuts and additional cooling of the laser heating zone. The technical result of the claimed invention is achieved by preliminary applying energy-absorbing layers of graphite on both sides of the sapphire plate in the direction of the cut, local heating of the cut line by laser radiation with a pulse duration of 50-100 ns and an average power of 80-100 W, the formation of a through separating crack in the material. The layers of graphite absorb a significant part of the laser radiation (about 50%), causing local heating of the surface of the sapphire substrate, which ensures the initiation and propagation of separating cracks by laser controlled thermal cracking.

The proposed method is illustrated in FIG. 1-3. In FIG. 1 is a block diagram of a laser controlled thermal cracking of sapphire plates. A device for cutting sapphire plates contains a laser system 1, an optical-mechanical system for directing and focusing radiation 2, a mechanism for moving the focal spot of a laser over the surface of a sample 3, a computer and a controller for controlling all electronic systems of the installation 4, and a video camera for monitoring the process 5.

In FIG. 2 shows a focusing system for a laser controlled thermal cracking of sapphire plates. The focusing system consists of a homogenizer 1, an optical lens 2, a system of movable optical elements 3 (galvanometers), a F-Theta 4 focusing lens and a stage 5. Using the F-Theta lens, direct proportionality is achieved between the scanning angle and the distance to the working field, and also the focus of the laser beam is always on a flat surface. The homogenizer makes it possible to obtain a uniform intensity distribution over the cross section of the laser beam (U-shaped intensity distribution).

In FIG. Figure 3 shows a photograph of the cut line of a sapphire plate along the graphite layer by infrared laser radiation.

An example of the proposed method of laser controlled thermal cracking of the plates. At the initial stage, graphite layers with a thickness of the order of 10 μm and a width of 2 mm, indicating the direction of the cut (on both sides of the plate), were deposited on a 2.4 mm thick sapphire plate. Previously, the graphite powder was crushed and mixed with ethanol. The paste was applied by screen printing, and the resulting layer was dried for 10 minutes. Then, a plate with deposited layers of graphite was placed on a stage of a laser installation and processed with infrared radiation from a solid-state Nd: YAG laser. Using a computer and a controller to control all electronic systems of the installation, the following laser processing parameters were set: the speed of the laser beam 1 mm / s on the surface of the graphite layer, the average laser radiation power of 90 W, the exposure time of about 350 s. From FIG. Figure 3 shows the high quality of the cutting line of the sapphire plate.

The invention is aimed at improving the efficiency of cutting sapphire plates, namely:

- on more economical use of material and reduction of waste;

- the absence of mechanical effects on the material;

- to the exclusion of grinding and polishing operations;

- to increase the accuracy and reproducibility of the sizes of cut products;

- at a high cutting speed;

- the ability to perform cutting along a complex path.

The invention can be used for high-precision and high-performance cutting of sapphire plates, which can find its application in the creation of new devices in micro- and optoelectronics, electronic industry. Laser-controlled thermal cracking of sapphire plates with deposited layers of graphite can improve the efficiency and quality of cutting. At the same time, energy-absorbing layers of graphite have a significant effect on the laser cutting of sapphire.

Claims (1)

Method of laser controlled thermal cracking of sapphire wafers by directing a laser beam from a pulsed solid-state Nd: YAG laser with a wavelength of 1064 nm to the surface of a sapphire wafer, characterized in that preliminary energy-absorbing layers of graphite are applied on both sides of the sapphire wafer in the direction of the cut, local heating of the cut line laser radiation with a pulse duration of 50-100 ns and an average power of 80-100 W, the formation of a through separating crack in the material.

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