JP2011177782A - Laser beam machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method for machining without causing any crack or the like by suppressing heat accumulation even when cutting a brittle material having high residual stress. <P>SOLUTION: This invention relates to a method for machining by irradiating a workpiece W with a laser beam, and the method includes a laser beam irradiation step where the laser beam is subjected to pulse oscillation to irradiate the workpiece W with the laser beam on a fixed cyclic frequency, and scanning the workpiece. A resin film 7 is adhered to a machining surface of the workpiece W, a metal film 8 is adhered to an opposing surface to the machining surface of the workpiece, the metal film 8 is tightly adhered to a mounting tool 4 to fix the workpiece W to the mounting tool 4, and the machining surface is irradiated with the laser beam from above the resin film 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser processing method suitable for cutting a brittle material, for example.

  In general, cutting of a brittle material such as a fired ceramic sheet is performed by a mechanical method such as grinding with a grindstone. However, since sintered ceramic sheets and the like generate high residual stress inside by sintering, the lower the substrate thickness, the higher the residual stress and the occurrence of cracks at the start of processing. It was difficult to process so that there was no.

  In addition, a method of performing processing such as cutting by irradiating a fired ceramic sheet or the like with laser light in order to obtain desired processing properties is also known. For example, conventionally, Patent Document 1 discloses a method of placing a ceramic green sheet on a sheet holding plate and irradiating the ceramic green sheet with a laser to perform drilling or cutting, wherein the sheet holding plate is It has a vacuum suction means for sucking and holding an object placed on its surface, an auxiliary sheet is interposed between the sheet holding plate and the ceramic green sheet, and a carrier film on the back surface of the ceramic green sheet And a method of processing a carrier film together with a ceramic green sheet by the laser has been proposed.

Moreover, in patent document 2, it had a base material and the adhesive layer provided in one surface of this base material as an adhesive sheet for laser processing used for the cutting process of the semiconductor wafer using a laser beam. Things are listed.
In these laser processing, a film is bonded to the back surface of a workpiece to support the workpiece during dicing.

Japanese Patent No. 3858382 JP 2009-297734 A

The following problems remain in the conventional technology.
In other words, even when using the conventional method of irradiating laser light, repeatedly scanning, inserting and scribing scribe grooves, cracks in unexpected directions during scribing due to thermal effects during processing and the dispersion of impurities Has occurred and has been divided. In particular, the processing heat generated by the laser light is stored in the processing object, and the stress of the processing object changes to cause a crack or a crack.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a laser processing method that can be processed without causing cracks by suppressing heat storage even in cutting processing of a brittle material having high residual stress. And

  The present invention employs the following configuration in order to solve the above problems. That is, the laser processing method of the present invention is a method of processing by irradiating a processing target with a laser beam, wherein the laser beam oscillates and irradiates the processing target with a constant repetition frequency. An irradiation step, and a resin film is bonded to the processed surface of the processing object, a metal film is bonded to the opposite surface of the processing object, and the metal film is closely attached to a mounting jig The processing object is fixed to an attachment jig, and the processing surface is irradiated with laser light from the resin film.

  In this laser processing method, a resin film is bonded to the processed surface of the processing object, a metal film is bonded to the opposite surface of the processing object, and the processing surface is irradiated with laser light from the resin film. Excess energy other than the center of the incident laser beam is absorbed by the resin film on the front surface, and heat during processing is dissipated to the mounting jig through the metal film on the back surface with high thermal conductivity, so that the brittle material It is possible to prevent heat storage on the processing object such as. In addition, the object to be processed can be mechanically held on both sides by the resin film and the metal film, and generation of cracks, cracks, and the like can be suppressed.

Moreover, the laser processing method of the present invention is characterized in that the irradiation is performed while circulating a coolant in the mounting jig.
That is, in this laser processing method, irradiation is performed while circulating the cooling liquid inside the mounting jig, so that the processing heat by the laser light is absorbed from the metal film on the back via the mounting jig by the circulating cooling liquid. Furthermore, it is possible to prevent heat accumulation on a workpiece such as a brittle material.

The present invention has the following effects.
That is, according to the laser processing method according to the present invention, the resin film is bonded to the processed surface of the object to be processed, and the metal film is bonded to the opposite surface of the processed surface. As a result, it is possible to absorb the excess energy of the laser beam and prevent heat accumulation on the workpiece, and to dynamically hold the workpiece on both sides, thereby suppressing the occurrence of cracks, cracks, etc. Can do.
Therefore, even when cutting a brittle material having a high residual stress, a stable process can be performed without causing cracks or cracks.

In one Embodiment of the laser processing method which concerns on this invention, it is a simple whole block diagram which shows a laser processing apparatus. In this embodiment, it is sectional drawing which shows a workpiece and an attachment jig. In this embodiment, it is explanatory drawing which shows the scanning method of a laser beam.

  Hereinafter, an embodiment of a laser processing method according to the present invention will be described with reference to FIGS. 1 to 3. In each drawing used for the following description, the scale is appropriately changed in order to make each member recognizable or easily recognizable.

  A laser processing apparatus 1 used in the laser processing method of the present embodiment is an apparatus for processing by irradiating a workpiece W with a laser beam L as shown in FIGS. Then, the laser beam irradiation mechanism 2 that irradiates and scans the workpiece W at a constant repetition frequency, the moving mechanism 3 that can move while holding the workpiece W, and the workpiece to be processed that is installed on the moving mechanism 3 An attachment jig 4 for attaching and fixing the object W, a cooling mechanism 5 for circulating the coolant 5a inside the attachment jig 4, and a control unit 6 for controlling them are provided.

The workpiece W is a brittle material having a high residual stress such as a ceramic sintered substrate.
At the time of processing, as shown in FIG. 2, the resin film 7 is adhered to the processing surface (surface) of the processing target W, and the processing surface is irradiated with the laser light L from the resin film 7. Further, the metal film 8 is bonded to the opposite surface (back surface) of the processing object W, and the metal film 8 is brought into close contact with the mounting jig 4 to fix the processing object W to the mounting jig 4. And then irradiate.

As the resin film 7, a polytetrafluoroethylene film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, a polymethylpentene film, a plastic film such as polyvinyl chloride, an ultraviolet transmissive film such as polyolefin, and the like can be used.
The metal film 8 may be a metal tape such as aluminum, copper, stainless steel (SUS). The metal film 8 is bonded to the workpiece W with an adhesive mainly composed of acrylic rubber, urethane resin, silicone resin or the like.

In addition, as these resin film 7 and metal film 8, it is preferable to employ | adopt the film of the low thermal expansion coefficient from which the thermal expansion coefficient is the same as or close to the workpiece W, and the thermal expansion difference at the time of a process does not produce easily. For example, as the workpiece W, alumina (Al ₂ O ₃ ) having a thermal expansion coefficient of 8.8 × 10 ⁻⁶ / K or lanthanum gallate having a thermal expansion coefficient of 10.8 × 10 ⁻⁶ / K is processed. In this case, a low thermal expansion coefficient special resin (for example, low thermal expansion polyimide) having a thermal expansion coefficient of 6 to 10 × 10 ⁻⁶ / K is employed as the resin film 7. In this case, the metal film 8 is preferably SUS304 having a thermal expansion coefficient of 13.6 × 10 ⁻⁶ / K.

  The moving mechanism 3 includes an X-axis stage portion 3x that can move in the X direction parallel to the horizontal plane, and a moving direction in the Y direction that is provided on the X-axis stage portion 3x and that is perpendicular to the X direction and parallel to the horizontal plane. A Y-axis stage unit 3y and a Z-axis stage unit 3z provided on the Y-axis stage unit 3y and capable of holding the workpiece W by fixing the mounting jig 4 and moving in a direction perpendicular to the horizontal plane And is composed of.

The laser beam irradiation mechanism 2 includes a laser light source 9 having an optical system that oscillates a laser beam L in response to a trigger signal of a Q switch and condenses it in a spot shape, a galvano scanner 10 that scans the irradiated laser beam L, and a holding unit. And a CCD camera 11 that captures an image to confirm the processing position of the processed object W.
As the laser light source 9, one that can irradiate a laser beam L having a wavelength of 190 to 550 nm can be used. For example, in the present embodiment, a laser beam that can oscillate and emit a laser beam L having a wavelength of 355 nm is used. Yes.

The galvano scanner 10 is disposed immediately above the moving mechanism 3. The CCD camera 11 is installed adjacent to the galvano scanner 10.
The cooling mechanism 5 has a structure in which, for example, cooling water is circulated as a coolant 5a in a flow passage 5b provided in the mounting jig 4, and a supply source ( (Not shown) are connected.

  In addition, the attachment jig 4 has a plurality of suction holes 4a formed on the attachment surface (upper surface) of the workpiece W, and these suction holes 4a are supplied from a vacuum source via a cavity 4b formed inside the jig. (Not shown). That is, the workpiece W placed on the mounting surface can be held by vacuum suction through the suction holes 4a. Thus, the attachment jig 4 is a water-cooled adsorption jig having a water-cooling function and a vacuum adsorption function.

  The laser beam irradiation mechanism 2 has a repetition frequency of H, a beam diameter of the laser beam L, a, a scanning frequency of the laser beam L on the same processing line, n, and a moving distance L per irradiation of the pulsed laser beam L of n. / 2 × a, the scanning speed S of the laser beam L is set to L / (1 / H), and the irradiation start position of the first laser beam L is set to L1, and the nth laser beam is scanned. The irradiation start position Ln is set to L1 + (L / n) × (n−1) so that irradiation is performed with the irradiation start position shifted for each scan.

At this time, the time per one laser beam is 1 / H. The number of scans n is an arbitrary number that does not cause cracks and the like, and is set in a range in which the scan speed S can be controlled.
Further, the laser light irradiation mechanism 2 sets the laser output slightly higher than the processing threshold value of the processing object W.

  More specifically, as shown in FIG. 3, when the number of scans is 3 (n = 3), the scan is started from the irradiation start position L1 at the first scan, and the movement distance L is left on the processing line. Laser light L is irradiated at a set repetition frequency H and scanning speed S. For example, when the beam diameter a is 20 μm and the repetition frequency H is 10 kHz, the scanning speed S is set to 300 mm / sec. In the first scanning, since the machining is performed with an interval on the machining line, the workpiece W is connected between the machining points.

  Next, at the time of the second scanning, the irradiation start position of the laser beam L is set to L1 + (L / 2) and is shifted from the first irradiation starting position to scan on the same processing line as the first time. Further, at the time of the last third scanning, the irradiation start position of the laser beam L is set to L1 + (L / 3) × 2 and is shifted from the first and second irradiation start positions on the same processing line as the first time. Scan with. By the three scans, the workpiece W is completely cut on the machining line.

  As described above, in the present embodiment, the resin film 7 is bonded to the processed surface of the workpiece W, and the metal film 8 is bonded to the opposite surface of the processed surface of the workpiece W. Is applied to the processed surface, so that excess energy other than the center of the laser beam L incident by the resin film 7 on the front surface is absorbed, and heat during processing through the metal film 8 on the back surface having high thermal conductivity. Can be radiated to the mounting jig 4 to prevent heat accumulation on the workpiece W such as a brittle material. Further, the workpiece W being processed can be mechanically held on both sides by the resin film 7 and the metal film 8, and generation of cracks, cracks, and the like can be suppressed.

  Further, since the irradiation is performed while circulating the cooling liquid 5a inside the mounting jig 4, the processing heat is absorbed from the metal film 8 on the back surface through the mounting jig 4 by the circulating cooling liquid 5a, and further the brittle material It is possible to prevent heat storage on the workpiece W such as.

  Note that the scanning speed S of the laser beam L is L / (1 / H), the irradiation start position of the laser beam L with the first scanning count is L1, and the irradiation start position Ln of the laser beam L with the scanning count of n. , L1 + (L / n) × (n−1) is performed by shifting the irradiation start position for each scan, so that the stress of the workpiece W is prevented from changing suddenly and cracks and the like are generated. Processing becomes possible.

  That is, in order to overlap the processing by scanning the same processing line one after another while shifting the irradiation start position so as to fill the moving distance L that is the spot interval of the laser light L irradiated as a pulse to the workpiece W. Since the machining points are spaced apart during a single scan, the workpieces W are connected with a gap during the scan, and are difficult to break. In addition, when scanning is performed so that the processing points by the laser beam continuously overlap as in the conventional case, since the connected grooves are cut and extended, a sudden stress change occurs. On the other hand, in the present embodiment, the machining points are not continuous during one scan, and a rapid stress change can be suppressed.

Next, an embodiment when actually processed by the laser processing method according to the present invention will be specifically described.
In this example, a ceramic sintered body (thickness: 250 μm) was processed as a processing target with a laser beam having a wavelength of 355 nm using the laser processing method of the present embodiment. At that time, a polyimide resin film (thickness: 0.1 mm) as a resin film was adhered to the surface of the ceramic sintered body with an acrylic adhesive, and an aluminum film (thickness: 0.05 mm) as a metal film was adhered to the back side as a silicone film. Bonded with an adhesive. The workpiece in this state was adsorbed on the mounting jig.

The laser beam output was set to 1.3 W, the repetition frequency H was set to 125 kHz, and the beam spot was measured. As a result, the beam diameter was 20 μm, so the galvano scanner was used to set the scanning speed S to 3750 mm / sec. Processing was performed three times.
As a result, a good cut surface without cracks could be obtained.

  The laser processing method of the present invention is particularly suitable for cutting a brittle material having a high residual stress.

  DESCRIPTION OF SYMBOLS 1 ... Laser processing apparatus, 2 ... Laser beam irradiation mechanism, 4 ... Mounting jig, 5 ... Cooling mechanism, 5a ... Cooling liquid, 7 ... Resin film, 8 ... Metal film, L ... Laser beam, W ... Work object

Claims (2)

A method of processing by irradiating a processing object with laser light,
A laser irradiation step of oscillating and irradiating the workpiece with a constant repetition frequency by oscillating a laser beam;
While adhering a resin film to the processed surface of the object to be processed, and adhering a metal film to the opposite surface of the processed surface of the object to be processed,
A laser processing method, wherein the metal film is brought into close contact with a mounting jig, the object to be processed is fixed to the mounting jig, and the processing surface is irradiated with laser light from the resin film. The laser processing method according to claim 1,
A laser processing method, wherein the irradiation is performed while circulating a coolant in the mounting jig.

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