JP2013063453A - Laser machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser machining method capable of cutting a workpiece formed by crystalline quartz with good dimensional accuracy, and of preventing the occurrence of damage on the outer surface of the workpiece.SOLUTION: A laser light L is focused onto the surface 3 of a crystalline quartz workpiece 1 as a laser light incident surface to form a modified region 7 along a planned cutting line 5 on the roughened back side 21 of the workpiece 1. Thereby, the occurrence of cracks exposed to the surface 3 is prevented, and the post-cutting dimensional accuracy of the workpiece 1 is improved. Further, since the processing threshold of the laser beam L is high, a large amount of energy of the laser beam L is consumed for formation of the modified region, and the laser beam L reaching the back side 21 being roughened scatters, resulting in less damage to the back side 21.

Description

  The present invention relates to a laser processing method for cutting a workpiece.

  As a conventional laser processing method, there is a method of condensing a laser beam on a processing object, forming a modified region along the planned cutting line on the processing target, and cutting the processing target along the planned cutting line. It is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2006-108459

  Here, in the laser processing method as described above, when a modified region is formed on a workpiece formed of quartz, generally, a processing threshold of laser light for forming the modified region is high. Therefore, the processing energy density of the focused laser beam is high. For this reason, cracks tend to extend from the modified region, and cracks exposed to the laser light incident surface tend to occur. In this regard, if a crack exposed on the laser light incident surface is generated, the crack is easy to meander due to, for example, the processing characteristics of the crystal, so that the dimensional accuracy (processing quality) of the workpiece after cutting is controlled. This is not easy, and it is difficult to improve the dimensional accuracy.

  Further, in the laser processing method as described above, it is preferable to prevent the outer surface of the processing target from being damaged by the irradiation of the processing target with the laser beam.

  Then, this invention makes it a subject to provide the laser processing method which can suppress that the outer surface is damaged while cut | disconnecting the workpiece formed with the quartz crystal with sufficient dimensional accuracy.

  In order to solve the above-described problems, a laser processing method according to the present invention cuts a workpiece to be processed having a surface formed of quartz and a back surface as a rough surface opposite to the surface along a planned cutting line. Forming a modified region along a planned cutting line on the back surface side of the processing object by condensing the laser beam on the processing object with the front surface being a laser light incident surface Including a process.

  In this laser processing method of the present invention, the modified region is formed on the back surface side opposite to the surface as the laser light incident surface. Therefore, it is possible to suppress the occurrence of cracks exposed on the laser light incident surface, and to increase the dimensional accuracy of the workpiece after cutting. At this time, since the modified region is formed on the back surface side, there is a concern about damage to the back surface, but since the processing threshold is high in quartz, the energy of the laser beam is greatly consumed in forming the modified region, Since the back surface is a rough surface, the laser light reaching the back surface is scattered, so that the back surface is rarely damaged. Therefore, according to the present invention, it is possible to cut a processing object formed of quartz with high dimensional accuracy and to prevent damage to the outer surface of the processing object.

  The center line average roughness on the back surface is preferably 0.05 μm or more. In this case, for example, it is possible to effectively cause scattering of laser light that has reached the back surface, thereby further suppressing damage to the back surface.

  In order to achieve the above-described effects, the thickness of the workpiece is specifically 100 μm or less. In the modified region forming step, the thickness of the workpiece is changed to 5 μm or less from the back surface. A quality region may be formed.

  Moreover, it is preferable to further include a cutting step of cutting the processing object from the modified region as a starting point of cutting by applying a force to the processing object from the outside along the scheduled cutting line. Thereby, it becomes possible to cut | disconnect a process target object along a cutting plan line reliably.

  According to the present invention, it is possible to cut a workpiece formed of crystal with high dimensional accuracy and to prevent damage to the outer surface.

It is a schematic block diagram of the laser processing apparatus used for formation of a modification area | region. It is a top view of the processing target object used as the object of formation of a modification field. It is sectional drawing along the III-III line of the workpiece of FIG. It is a top view of the processing target after laser processing. It is sectional drawing along the VV line of the workpiece of FIG. It is sectional drawing along the VI-VI line of the processing target object of FIG. It is a flowchart which shows the manufacturing process of the crystal oscillator which concerns on this embodiment. It is the schematic for demonstrating the process of cut | disconnecting a workpiece to a quartz chip.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

  In the laser processing method according to the present embodiment, the laser beam is focused on the object to be processed, and the modified region is formed along the planned cutting line. First, the formation of the modified region will be described with reference to FIGS.

  As shown in FIG. 1, a laser processing apparatus 100 includes a laser light source 101 that oscillates a laser beam L, a dichroic mirror 103 that is arranged so as to change the direction of the optical axis (optical path) of the laser beam L, and A condensing lens (condensing optical system) 105 for condensing the laser light L. Further, the laser processing apparatus 100 includes a support base 107 for supporting the workpiece 1 irradiated with the laser light L condensed by the condensing lens 105, and a stage 111 for moving the support base 107. A laser light source controller (control means) 102 for controlling the laser light source 101 in order to adjust the output, pulse width, pulse waveform, etc. of the laser light L, and a stage controller 115 for controlling the movement of the stage 111. ing.

  In this laser processing apparatus 100, the laser light L emitted from the laser light source 101 has its optical axis changed by 90 ° by the dichroic mirror 103, and the inside of the processing object 1 placed on the support base 107. The light is condensed by the condensing lens 105. At the same time, the stage 111 is moved, and the workpiece 1 is moved relative to the laser beam L along the planned cutting line 5. As a result, a modified region along the planned cutting line 5 is formed on the workpiece 1. Here, the stage 111 is moved in order to move the laser light L relatively, but the condensing lens 105 may be moved, or both of them may be moved.

  The processing object 1 is formed of quartz, and as shown in FIG. 2, a cutting line 5 for cutting the processing object 1 is set in the processing object 1. The planned cutting line 5 is a virtual line extending linearly. When the modified region is formed inside the workpiece 1, as shown in FIG. 3, the laser beam L is scheduled to be cut in a state where the focusing point (focusing position) P is aligned with the inside of the workpiece 1. It moves relatively along the line 5 (that is, in the direction of arrow A in FIG. 2). Thereby, as shown in FIGS. 4 to 6, the modified region 7 is formed inside the workpiece 1 along the planned cutting line 5, and the modified region 7 formed along the planned cutting line 5 is formed. It becomes the cutting start area 8.

  In addition, the condensing point P is a location where the laser light L is condensed. Further, the planned cutting line 5 is not limited to a straight line, but may be a curved line, a three-dimensional shape in which these lines are combined, or a coordinate designated. Further, the planned cutting line 5 is not limited to a virtual line but may be a line actually drawn on the surface 3 of the workpiece 1. The modified region 7 may be formed continuously or intermittently. Further, the modified region 7 may be in the form of a line or a dot. In short, the modified region 7 only needs to be formed at least inside the workpiece 1. In addition, a crack may be formed starting from the modified region 7, and the crack and the modified region 7 may be exposed on the outer surface (front surface 3, back surface 21, or outer peripheral surface) of the workpiece 1. Good. Further, the laser light incident surface when forming the modified region 7 is not limited to the front surface 3 of the workpiece 1 but may be the back surface 21 of the workpiece 1.

  Incidentally, the laser light L here passes through the workpiece 1 and is particularly absorbed near the condensing point inside the workpiece 1, thereby forming the modified region 7 in the workpiece 1. (Ie, internal absorption laser processing). Therefore, since the laser beam L is hardly absorbed by the surface 3 of the workpiece 1, the surface 3 of the workpiece 1 is not melted. In general, when a removed portion such as a hole or a groove is formed by being melted and removed from the front surface 3 (surface absorption laser processing), the processing region gradually proceeds from the front surface 3 side to the back surface side.

  By the way, the modified region formed in the present embodiment refers to a region where the density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings. Examples of the reforming region include a melting treatment region (meaning at least one of a region once solidified after melting, a region in a molten state, and a region in a state of being resolidified from melting), a crack region, There are dielectric breakdown regions, refractive index change regions, and the like, and there are also regions where these are mixed. Furthermore, as the modified region, there are a region where the density of the modified region in the material of the workpiece is changed compared to the density of the non-modified region, and a region where lattice defects are formed. Also known as the metastatic region).

In addition, the area where the density of the melt-processed area, the refractive index changing area, the modified area is changed compared to the density of the non-modified area, or the area where lattice defects are formed is In some cases, cracks (cracks, microcracks) are included in the interface between the non-modified region and the non-modified region. The included crack may be formed over the entire surface of the modified region, or may be formed in only a part or a plurality of parts. As the processing object 1, quartz (SiO ₂ ) or a material containing quartz is used.

  Further, in the present embodiment, the modified region 7 is formed by forming a plurality of modified spots (processing marks) along the planned cutting line 5. The modified spot is a modified portion formed by one pulse shot of pulsed laser light (that is, one pulse of laser irradiation: laser shot). Examples of the modified spot include a crack spot, a melting treatment spot, a refractive index change spot, or a mixture of at least one of these.

  Considering the required cutting accuracy, required flatness of the cut surface, thickness of the workpiece, type, crystal orientation, etc., the size of the modified spot and the length of the crack to be generated are appropriately determined. It is preferable to control.

  Next, this embodiment will be described in detail.

  The present embodiment is used, for example, as a method of manufacturing a crystal unit for manufacturing a crystal unit, and cuts a workpiece 1 formed of crystal that is a hexagonal column crystal into a plurality of crystal chips. To do. First, the overall manufacturing process flow of the crystal unit will be described with reference to FIG.

  First, the raw quartz crystal is cut out by, for example, diamond grinding and processed into a rod-shaped body (lumbard) of a predetermined size (S1). Subsequently, the cutting angle corresponding to the temperature characteristic requirement of the crystal resonator is measured by X-rays, and the lambard is cut into a plurality of wafer-like workpieces 1 by wire saw processing based on this cutting angle (S2). The workpiece 1 here has a rectangular plate shape of 10 mm × 10 mm, and has a crystal axis inclined by 35.15 ° with respect to the thickness direction.

  Subsequently, lapping is performed on the front surface 3 and the back surface 21 of the workpiece 1 and the thickness is set to a predetermined thickness (S3). Subsequently, the cutting angle is measured by X-rays at a minute angle level, and after selecting and classifying the workpiece 1, lapping processing similar to the above S3 is performed again on the front surface 3 and the back surface 21 of the workpiece 1. Then, the thickness of the workpiece 1 is finely adjusted (S4, S5).

  In S5, the workpiece 1 has a thickness of 100 μm or less, and preferably has an ultra-thin shape with a thickness of 35 μm. Further, the front surface 3 and the back surface 21 are subjected to lapping in S3 and S5, so that the front surface 3 and the back surface 21 are rough surfaces. Specifically, the front surface 3 and the back surface 21 are formed in, for example, a satin shape, and the center line average roughness Ra (hereinafter simply referred to as “roughness Ra”) is 0.05 μm or more, preferably 0.05 μm to It is 0.30 μm. In addition, roughness Ra means the centerline average roughness defined by Japanese Industrial Standard (JIS-B0601).

  Subsequently, as a cutting process and an outline process, the modified region 7 is formed on the workpiece 1, and the workpiece 1 is cut along the planned cutting line 5 using the modified region 7 as a starting point for cutting (S6: details). Is described later). As a result, a plurality of crystal chips having external dimensions with a dimensional accuracy of ± several μm or less are obtained. In the present embodiment, the line 5 to be cut is set in the processing object 1 in a lattice shape when viewed from the front surface 3, and the processing object 1 is cut as a rectangular plate-shaped crystal chip of 1 mm × 0.5 mm.

  Subsequently, the quartz chip is subjected to chamfering (convex machining) so as to have a predetermined frequency, and the thickness of the quartz chip is adjusted by etching so as to have a predetermined frequency (S7, S8). Thereafter, the crystal chip is assembled as a crystal resonator (S9). Specifically, an electrode is formed on the crystal chip by sputtering, this crystal chip is mounted in the mounter, heat-treated in a vacuum atmosphere, and then the crystal chip electrode is shaved by ion etching to adjust the frequency. Seal the seam. Thereby, the manufacture of the crystal unit is completed.

  FIG. 8 is a schematic diagram for explaining a process of cutting a workpiece into a quartz chip. In the drawing, for convenience of explanation, the cutting along one cutting scheduled line 5 is illustrated as an example. In the above-described step S6 for cutting the workpiece 1 into the crystal chip, first, the expand tape 31 is attached to the back surface 21 of the workpiece 1 and the workpiece 1 is placed on the support 107 (see FIG. 1). .

  Subsequently, the laser light source control unit 102 controls the laser light source 101 and the stage control unit 115 controls the stage 111, and the laser beam L is appropriately condensed on the workpiece 1 along the scheduled cutting line 5 and modified. The quality region 7 is formed (modified region forming step).

  Specifically, as shown in FIG. 8 (a), the condensing point is set on the back surface 21 side in the workpiece 1, and the laser beam L is irradiated from the front surface 3 side with an output of 0.2 W, for example. At the same time, the laser beam L is moved relative to the workpiece 1 at a speed of, for example, 135 mm / s (scanning). As a result, the modified region 7 including a plurality of modified spots having a pitch of 3 μm, for example, is formed along the planned cutting line 5 without forming a crack exposed on the surface 3 of the workpiece 1. One row is formed on the back surface 21 side. Then, the above scan is performed for all the cutting scheduled lines 5.

  Here, as a preferable case, the laser beam L is irradiated from the back surface 21 to the position of the half or less of the thickness of the workpiece 1 in the workpiece 1 and irradiated with the laser beam L, and the target location in the workpiece 1 is irradiated. A modified region 7 is formed along the planned cutting line 5. Alternatively, preferably, the processing object 1 is irradiated with the laser light L at a position within 0 to 10 μm (more preferably, 5 μm or less) from the back surface 21 within the processing object 1, and the position in the processing object 1. Then, the modified region 7 is formed along the cutting line 5. Further alternatively, preferably, a laser beam L is irradiated in the vicinity of the back surface 21 near the back surface 21 in the processing object 1, and a modified region is formed along the planned cutting line 5 near the back surface 21 in the processing object 1. 7 is formed.

  Subsequently, as shown in FIG. 8B, after the expanded tape 31 is transferred to the front surface 3, the knife edge along the planned cutting line 5 from the back surface 21 side with respect to the workpiece 1 through the expanded tape 31. 32 is pressed (cutting step). As a result, a force is applied to the workpiece 1 from the outside along the planned cutting line 5 so that the modified region 7 is opened (releasing stress), and a plurality of workpieces 1 are formed using the modified region 7 as a starting point for cutting. Cut into crystal chips. Then, as shown in FIG. 8C, the expanded tape 31 is expanded to ensure the chip interval. Thus, the workpiece 1 is cut as a plurality of crystal chips 10.

  By the way, when the laser beam L is condensed on the workpiece 1 formed of quartz and the modified region 7 is formed, it is necessary to increase the energy density of the laser beam L because the processing threshold is high. Cracks tend to extend from the material region 7 and cracks (half cuts) exposed on the surface 3 as the laser light incident surface are likely to occur. Since this half-cut is easy to meander due to the processing characteristics of quartz, for example, the cut surface is formed in a sawtooth shape, and it is not easy to control the dimensional accuracy (processing quality) of the workpiece 1 after cutting. . In this regard, in the present embodiment, as described above, the modified region 7 is formed on the back surface 21 side as the opposite surface of the front surface 3 that is the laser light incident surface, and thus half-cut is suppressed. be able to. As a result, the dimensional accuracy of the workpiece 1 after cutting can be increased.

  Here, when the modified region 7 is formed on the back surface 21 side, there is a concern that the back surface 21 may be damaged, and this concern becomes significant when the workpiece 1 is thin as in the present embodiment. On the other hand, in the present embodiment, the energy of the laser beam L is greatly consumed by the formation of the modified region 7 due to the high processing threshold of the crystal, and the back surface 21 is a rough surface. Since the laser beam L that has reached scatters, the back surface 21 is less likely to be damaged. Furthermore, even if the modified region 7 is formed on the back surface 21 side, since the workpiece 1 itself has a high hardness, there is little adverse effect on the bending strength.

  Therefore, according to this embodiment, when cutting the workpiece 1 formed of quartz, the workpiece 1 is cut with high dimensional accuracy while suppressing damage to the outer surface of the workpiece 1. As a result, the processing quality can be improved.

  In the present embodiment, as described above, since the roughness Ra of the back surface 21 is 0.05 μm or more, for example, scattering of the laser light L that has reached the back surface 21 is effectively generated. The damage to 21 can be further suppressed.

  Further, in the present embodiment, as described above, external stress is applied to the workpiece 1 along the planned cutting line 5 using the knife edge 32, and the workpiece 1 is set with the modified region 7 as a starting point of cutting. doing. Thereby, even if it is the process target object 1 formed with the crystal which is hard to cut | disconnect, it becomes possible to cut | disconnect the process target object 1 accurately along the cutting scheduled line 5 reliably.

  Note that, when the modified region 7 is formed on the surface 3 side as the laser beam incident surface in the workpiece 1, since the laser beam L needs a high energy density as described above, a half cut occurs. There is a great risk that the processing quality will deteriorate. Further, in this case, it is not easy to control the laser beam L so that half-cut does not occur, and so-called idling (the modified spot or modified region 7 is not formed even when the laser beam L is condensed on the workpiece 1). Phenomenon). Also in this respect, it can be said that the technical significance of the present embodiment in which the modified region 7 is formed on the back surface 21 side of the workpiece 1 is great.

  Incidentally, since a crystal resonator is a device that uses the characteristics of the crystal material itself, the dimensional accuracy of a crystal chip for a crystal resonator greatly affects temperature characteristics and resonator characteristics. Therefore, the above-described effect of cutting the workpiece 1 with high dimensional accuracy as a quartz chip becomes prominent when a quartz resonator is manufactured.

  Moreover, even if the front surface 3 and the back surface 21 are rough surfaces, there is little adverse effect on the piezoelectric effect. In addition, the thinner the quartz chip, the more preferably it can be used as a high frequency device. Therefore, it can be said that this embodiment which can cut the workpiece 1 as a thin quartz chip having a rough surface is particularly effective.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. May be.

  For example, in the above description, the numerical values of the thickness of the workpiece 1, the formation position of the modified region 7, and the roughness Ra allow for errors in processing, manufacturing, and design. In the above embodiment, the modified region 7 is formed inside the workpiece 1. However, the modified region 7 may be exposed from the back surface 21 that is the opposite surface of the laser light incident surface. The present invention can also be regarded as a crystal resonator manufacturing method or manufacturing apparatus for manufacturing a crystal resonator by the laser processing method described above, but is not limited to a crystal resonator manufacturing method and is formed of crystal. The present invention can be applied to various methods or apparatuses for cutting a workpiece.

  DESCRIPTION OF SYMBOLS 1 ... Processing object, 5 ... Planned cutting line, 7 ... Modified area | region, L ... Laser beam.

Claims (4)

A laser processing method for cutting an object to be processed having a front surface and a back surface as a rough surface opposite to the front surface formed of quartz, along a planned cutting line,
Including a modified region forming step of condensing a laser beam on the object to be processed with the surface as a laser beam incident surface and forming a modified region along the planned cutting line on the back surface side of the object to be processed. A laser processing method characterized by the above.   The laser processing method according to claim 1, wherein a center line average roughness of the back surface is 0.05 μm or more. The processing object has a thickness of 100 μm or less,
3. The laser processing method according to claim 1, wherein in the modified region forming step, the modified region is formed at a position of 5 μm or less from the back surface in the object to be processed.   2. The method according to claim 1, further comprising a cutting step of cutting the workpiece from the modified region as a starting point of cutting by applying a force to the workpiece from the outside along the scheduled cutting line. The laser processing method as described in any one of -3.

Images