JP2016107389A - Grinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize a crack of a plate-like workpiece and prevent a crack of a subsequent plate-like workpiece by suppressing deterioration of a grind stone.SOLUTION: A grinder (1) comprises: a chuck table (21) for holding a plate-like workpiece (W); grind means (41) for grinding the plate-like workpiece with a grind stone (48); and thickness measurement means (51) for detecting a crack of the plate-like workpiece. In the thickness measurement means, measurement light emitted from an irradiation part (52) is reflected by a top face (81) and a bottom face (82) of the plate-like workpiece and received by a light reception part (53). The crack of the plate-like workpiece is detected if the light reception amount of the reflected light exceeds a predetermined allowable range.SELECTED DRAWING: Figure 3

Description

The present invention relates to a grinding apparatus for grinding a hard plate-like workpiece such as sapphire (Al ₂ O ₃ ) or silicon carbide (SiC).

  In grinding a hard plate-like workpiece such as sapphire or silicon carbide, the plate-like workpiece may be broken by a grinding load. If the grinding process is continued in a state where the plate-like workpiece is cracked, the grinding wheel is chipped, and the grinding force of the grinding wheel is reduced. The reduction of the grinding force makes it difficult for the plate-like workpiece to be reduced in thickness, and an excessive load is applied to the plate-like workpiece, which further deteriorates cracks and causes many chips on the grinding wheel. As a result, the scraps of the plate-like workpiece adhere to the holding surface of the chuck table, and the subsequent plate-like workpiece is ground with a grinding wheel that does not have a normal grinding force. It was.

  For this reason, the method of specifying the crack of a plate-shaped workpiece regularly is proposed so that grinding may not be continued in the state where a crack occurred in a plate-shaped workpiece (for example, refer to patent documents 1 and 2). In the method described in Patent Document 1, when the protective tape is peeled off from the plate-shaped workpiece, the crack of the plate-shaped workpiece is transferred to the protective tape. Specific cracks. In the method described in Patent Document 2, a plate-like workpiece on the chuck table is irradiated from a light emitting portion provided in the chuck table, and light leaking from a crack in the plate-like workpiece is imaged to identify a crack in the plate-like workpiece. doing.

JP2013-131537A JP 2014-154708 A

  However, any of the methods for identifying cracks in a plate-like workpiece described in Patent Documents 1 and 2 determines whether or not the plate-like workpiece is cracked after grinding. That is, the method described in Patent Document 1 cannot identify cracks unless the protective tape is peeled off from the plate-shaped workpiece. The method described in Patent Document 2 does not stop the grinding process until the surface of the plate-shaped workpiece is stopped. I can't take an image. Therefore, until the grinding of the plate workpiece is completed, the grinding process is continued even if the plate workpiece is cracked. There was a problem that cracks occurred in the plate workpiece.

  The present invention has been made in view of the above points, and a grinding apparatus capable of preventing the cracking of a subsequent plate-shaped workpiece by suppressing the degradation of the grinding wheel while minimizing the cracking of the plate-shaped workpiece. The purpose is to provide.

  The grinding apparatus of the present invention uses a grinding wheel to grind a chuck table for holding a plate-like workpiece, a rotating means for continuously rotating the chuck table, and a plate-like workpiece for holding the chuck table continuously rotated by the rotating means. A cracking means for detecting cracks in the plate-like workpiece held by the chuck table to be ground by the grinding means, the crack detection means comprising: An irradiation unit that irradiates measurement light from above toward the upper surface of the plate-shaped workpiece, a light-receiving unit that receives reflected light reflected from the plate-shaped workpiece by the measurement light irradiated from the irradiation unit, and the light reception unit And a determination unit that determines that the light is received when the amount of light received by the unit exceeds a preset allowable range.

  According to this configuration, the measurement light is irradiated toward the plate-shaped workpiece, and the crack of the plate-shaped workpiece is determined from the change in the amount of reflected light received. Since the change in the amount of received light is monitored while the grinding process is continued, it is possible to immediately determine the crack of the plate workpiece. Therefore, the cracking of the plate-like workpiece can be kept to a minimum, and the grinding process can be stopped before the grinding wheel of the grinding means deteriorates. It is possible to prevent the workpiece from cracking.

  Further, in the grinding apparatus of the present invention, the crack detection means is a thickness measuring means provided with a thickness calculation unit for calculating the thickness of the plate-shaped workpiece, and the irradiation unit is provided above the plate-shaped workpiece from the upper surface of the plate-shaped workpiece. The light receiving unit receives the reflected light reflected by the upper surface of the plate-shaped workpiece and the reflected light reflected by the lower surface of the plate-shaped workpiece, and the thickness calculating unit receives the measured light. The thickness of the plate-like workpiece is calculated from the reflected light reflected from the upper surface and the lower surface, and the determination unit receives the reflected light reflected from the upper surface received by the light receiving unit or the reflected light reflected from the lower surface. Is determined to be cracked when it exceeds a preset tolerance.

  According to the present invention, by irradiating the plate-shaped workpiece with measurement light, and judging the crack of the plate-shaped workpiece from the change in the amount of reflected light received, the crack of the plate-shaped workpiece is kept to a minimum, Deterioration of the grinding wheel can be suppressed, and the subsequent plate-like workpiece can be prevented from cracking.

It is a perspective view of the grinding device concerning this embodiment. It is explanatory drawing of the grinding operation which concerns on this Embodiment. It is a schematic diagram of the thickness measurement means which concerns on this Embodiment. It is explanatory drawing which shows the relationship between the crack of the plate-shaped workpiece | work which concerns on this Embodiment, and light-receiving amount. It is explanatory drawing of the thickness measurement of a plate-shaped workpiece | work which concerns on this Embodiment, and a crack detection. It is a schematic diagram of the height measurement means which concerns on a modification.

  Hereinafter, the grinding apparatus according to the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a grinding apparatus according to the present embodiment. Note that the grinding apparatus according to the present embodiment is not limited to the apparatus configuration dedicated to the grinding process as shown in FIG. 1, and for example, a series of processes such as a grinding process, a polishing process, and a cleaning process are performed fully automatically. It may be incorporated into a fully automatic type processing apparatus. In the following drawings, for convenience of explanation, the description of a BG (Back-Grinding) tape is omitted.

  As shown in FIG. 1, the grinding apparatus 1 is configured to grind the plate-like workpiece W held on the chuck table 21 by using a grinding wheel 46 in which a large number of grinding wheels 48 are arranged in an annular shape. . In the grinding apparatus 1, the rotation axis of the chuck table 21 and the rotation axis of the grinding wheel 46 are decentered, and the grinding wheel 48 arranged in an annular shape passes through the upper surface 81 of the plate-like workpiece W, so that the plate-like workpiece W has an arc shape. It is cut and thinned. The plate-like workpiece W is not limited to a hard plate-like workpiece such as sapphire or silicon carbide, but may be a semiconductor substrate such as silicon or gallium arsenide, or a substrate formed of resin or metal.

  A rectangular opening extending in the X-axis direction is formed on the upper surface of the base 11 of the grinding apparatus 1, and this opening is covered with a movable plate 12 that can move together with the chuck table 21 and a bellows-shaped waterproof cover 13. ing. Below the waterproof cover 13, ball screw type advance / retreat means (not shown) for moving the chuck table 21 in the X-axis direction and rotation means 22 for continuously rotating the chuck table 21 are provided. On the surface of the chuck table 21, a holding surface 23 for adsorbing the plate-like workpiece W by a porous porous material is formed. The holding surface 23 is connected to a suction source (not shown) through a flow path in the chuck table 21, and the plate-like workpiece W is sucked and held by the negative pressure generated on the holding surface 23.

  The column 14 on the base 11 is provided with a grinding feed means 31 that moves the grinding means 41 toward and away from the chuck table 21 in the grinding feed direction (Z-axis direction). The grinding feed means 31 has a pair of guide rails 32 arranged in the column 14 and parallel to the Z-axis direction, and a motor-driven Z-axis table 33 slidably installed on the pair of guide rails 32. . Nut portions (not shown) are formed on the back side of the Z-axis table 33, and a ball screw 34 is screwed to these nut portions. The ball screw 34 is rotationally driven by a drive motor 35 connected to one end of the ball screw 34, whereby the grinding means 41 is moved along the guide rail 32 in the Z-axis direction.

  The grinding means 41 is attached to the front surface of the Z-axis table 33 via a housing 42, and is configured by providing a mount 44 at the lower end of a cylindrical spindle 43. The spindle 43 is provided with a flange 45, and the grinding means 41 is supported on the housing 42 via the flange 45. The lower surface of the mount 44 holds a grinding wheel 46 in which a plurality of grinding wheels 48 are mounted on a wheel base 47 in a circular shape. The plurality of grinding wheels 48 are constituted by, for example, segment grindstones in which diamond abrasive grains are hardened with a bonding agent such as metal bond.

  In the vicinity of the grinding means 41, a thickness measuring means 51 for measuring the thickness of the plate-like workpiece W is provided. The thickness measuring means 51 measures the thickness of the plate-like workpiece W by, for example, a non-contact type interference spectroscopy method, and the plate-like workpiece W is determined by the optical path difference of the reflected light from the upper surface 81 and the lower surface 82 of the plate-like workpiece W. Measure the thickness. Further, the grinding apparatus 1 is provided with a control means 61 that controls each part of the apparatus. The control unit 61 includes a processor that executes various processes, a memory, and the like. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application.

  In the grinding apparatus 1 configured as described above, the plate-like workpiece W is first held on the chuck table 21. In FIG. 1, the holding surface 23 is drawn flat. However, as shown in FIG. 2, the actual holding surface 23 has a conical shape with a gentle inclination with the center of rotation of the chuck table 21 as a vertex. Is also held conically along the holding surface 23. After the inclination of the chuck table 21 is adjusted so that the upper surface of the conical plate-like workpiece W is parallel to the grinding surface of the grinding wheel 48, the grinding wheel 48 and the plate-like workpiece W are supplied while grinding water is supplied. Grinding by rotating contact. During the grinding process, the thickness of the plate-like workpiece W is measured in real time by the thickness measuring means 51, and the feed amount of the grinding means 41 is controlled based on the measurement result of the thickness measuring means 51.

  By the way, in grinding processing of the hard plate-like workpiece W, the above-described grinding apparatus 1 is used to gradually finer the grain size of the grinding stone in three stages, for example, Z1-axis processing, Z2-axis processing, and Z3-axis processing. And can be brought close to the target thickness. In the Z2 axis machining, the plate-like workpiece W is easily cracked by the grinding load, and the grinding wheel 48 may be scraped by the abrasive grains that have entered the crack of the plate-like workpiece W, and the grinding wheel 48 may be chipped. If the grinding of the plate-like workpiece W is continued with the grinding wheel 48 in which the chip has occurred, the plate-like workpiece W is more likely to be cracked. There is a problem in that the crack of the plate-shaped workpiece W and the chipping of the grinding wheel 48 are repeated, so that the deterioration of the grinding wheel 48 proceeds, and the subsequent plate-shaped workpiece W is likely to be cracked.

  When the present inventor examined the relationship between the amount of light received by the plate-like workpiece W and the crack of the plate-like workpiece W, the measurement light from the thickness measuring means 51 is diffusely reflected by the crack of the plate-like workpiece W and becomes the amount of received light. I have found that changes occur. Therefore, in the present embodiment, the thickness of the plate-like workpiece W is measured by the thickness measuring means 51 while the grinding process is continued, and the crack of the plate-like workpiece W is detected from the change in the amount of received light. . Thereby, the crack of the plate-like workpiece W can be detected immediately, and it is possible to prevent the subsequent plate-like workpiece W from cracking by suppressing deterioration of the grinding wheel 48 at an early stage.

  Here, the thickness measuring means will be described with reference to FIGS. FIG. 3 is a schematic diagram of thickness measuring means according to the present embodiment. FIG. 4 is an explanatory diagram showing the relationship between the crack of the plate-like workpiece and the amount of received light according to the present embodiment. In addition, the thickness measuring unit according to the present embodiment is not limited to the configuration shown in FIG. 3, and may be configured in any manner as long as it is a configuration that can measure the thickness of the plate-like workpiece with an optical method.

  As shown in FIG. 3, the thickness measuring unit 51 includes an irradiation unit 52 that irradiates measurement light from above the plate-like workpiece W toward the upper surface 81 of the plate-like workpiece W, and the measurement light is reflected by the plate-like workpiece W. And a light receiving portion 53 for receiving the reflected light. The measurement light emitted from the irradiation unit 52 is reflected by the upper surface 81 and the lower surface 82 of the plate-like workpiece W and received by the light receiving unit 53, respectively. Further, the thickness measuring means 51 is provided with a thickness calculating section 54 that calculates the thickness of the plate-like workpiece W from the reflected light reflected by the upper surface 81 and the lower surface 82 of the plate-like workpiece W. The thickness calculation unit 54 calculates the thickness of the plate-like workpiece W based on the optical path difference of the reflected light from the upper surface 81 and the lower surface 82 of the plate-like workpiece W.

  The thickness measuring means 51 has a function of detecting cracks in the plate-like workpiece W in addition to the function of measuring the thickness of the plate-like workpiece W. As described above, when cracks occur in the plate-like workpiece W, the measurement light is diffusely reflected by the plate-like workpiece W. Therefore, the thickness measuring unit 51 uses the change in the amount of received light due to this diffuse reflection to obtain the plate-like workpiece. W cracking is detected. In order to detect the crack of the plate-like workpiece W, the thickness measuring unit 51 is provided with a determination unit 55 that determines the crack of the plate-like workpiece W from the amount of received light of the reflected light received by the light receiving unit 53. In the determination unit 55, an allowable range of the amount of received light that is a determination criterion for cracking of the plate-like workpiece W is set.

  The determination unit 55 breaks into the plate-shaped workpiece W when the amount of light reflected by the upper surface 81 of the plate-shaped workpiece W or the amount of reflected light reflected by the lower surface 82 of the plate-shaped workpiece W exceeds a preset allowable range. Is determined to have occurred. The allowable range is determined, for example, by obtaining the relationship between the crack of the plate-like workpiece W and the amount of received light in advance. Further, the allowable range may be set in common for the reflected light from the upper surface 81 of the plate-like workpiece W and for the reflected light from the lower surface 82 of the plate-like workpiece W, or may be set individually. The calculation result of the thickness calculation unit 54 and the determination result of the determination unit 55 are output to the control unit 61 and used for controlling the grinding operation of the grinding unit 41.

  During the grinding process, the thickness calculation unit 54 calculates the thickness of the plate workpiece W in real time, and the grinding means so that the plate workpiece W approaches the target finish thickness based on the calculation result of the thickness calculation unit 54. The feed amount 41 is controlled. Further, during the grinding process, the crack detection of the plate-like workpiece W by the determination unit 55 is also performed in real time, and the drive and stop of the grinding means 41 are controlled based on the determination result of the determination unit 55. Grinding is continued while the determination unit 55 does not determine that the plate-like workpiece W is cracked. If the determination unit 55 determines that the plate-like workpiece W is cracked, the grinding means 41 is stopped and the plate-like workpiece W is stopped. The operator is informed of the crack of the workpiece W.

  As shown in FIG. 4A, the crack 83 of the plate-like workpiece W occurs from the outer edge of the plate-like workpiece toward the center, passes through the center, and then occurs from the center of the plate-like workpiece W toward the outer edge of the radial direction. Tend to. Therefore, the thickness measuring means 51 detects the crack 83 generated in the plate-like workpiece W without overlooking it by rotating the plate-like workpiece W in a state where the measurement light is irradiated to a predetermined position in the radial direction of the plate-like workpiece W. It is possible to do. The thickness measuring unit 51 may detect the cracks 83 at a plurality of locations in the radial direction of the plate-like workpiece W while changing the position in the radial direction of the plate-like workpiece W.

  As shown in FIG. 4B, when the measurement light is reflected by the crack 83 of the plate-like workpiece W, the amount of received light changes greatly due to the diffuse reflection of the measurement light. The amount of received light changes so as to increase greatly after greatly decreasing at the angular position where the crack 83 of the plate-like workpiece W occurs. The crack 83 of the plate-like workpiece W is detected according to whether or not the amount of received light exceeds the allowable range. Since the change (peak) in the amount of received light appears periodically, it may be detected that the plate-like workpiece W is cracked when the change in the amount of received light appears multiple times. Further, when the amount of received light exceeds one of the upper limit and the lower limit of the allowable range, it may be determined as a crack 83 of the plate-like work W, or when both the upper limit and the lower limit of the allowable range are exceeded, the plate-like work W. The crack 83 may be determined.

  Then, with reference to FIG. 5, the thickness measurement of a plate-shaped workpiece | work by a thickness measurement means and crack detection are demonstrated. FIG. 5 is an explanatory diagram of the thickness measurement and crack detection of the plate-like workpiece according to the present embodiment. In addition, since the thickness measurement process and the crack detection process shown in FIG. 5 show an example, it is not limited to this structure. Further, although the holding surface of the chuck table is described as being flat, it is actually formed in a slowly inclined cone shape. Further, for convenience of explanation, the Z2 axis grinding apparatus and the Z3 axis grinding apparatus are assigned the same reference numerals.

  As shown in FIG. 5A, the plate-like workpiece W after the Z1-axis machining (coarse grinding) is carried into the Z2-axis grinding machine and held so that the center of the plate-like workpiece W is aligned with the center of the chuck table 21. Is done. Then, the grinding wheel 46 is rotated around the Z-axis and brought close to the plate-like workpiece W, and the grinding wheel 48 and the plate-like workpiece W are slid relative to each other so that the plate-like workpiece W is Z2-axis processed. In Z2-axis machining (medium grinding), grinding is performed using a grinding wheel 48 having a finer particle size than Z1-axis machining. During the grinding process, the thickness of the plate-like workpiece W is measured and the crack of the plate-like workpiece W is detected in real time while air is blown by the thickness measuring means 51.

  Based on the thickness of the plate-like workpiece W from the thickness measuring means 51, the plate-like workpiece W is ground until the thickness of the plate-like workpiece W reaches the target thickness. When the thickness measuring means 51 detects a crack in the plate workpiece W during grinding, the grinding operation is stopped and the operator is prompted to remove the plate workpiece W on the chuck table 21. As described above, when the plate-like workpiece W is cracked, the grinding process is immediately stopped. Therefore, the grinding is not continued in the state where the plate-like workpiece W is broken, and the grinding wheel 48 is further deteriorated. Nor. Therefore, since the deterioration of the grinding wheel 48 is suppressed, the subsequent plate-like workpiece W can be prevented from cracking.

  On the other hand, when a crack is not detected in the plate-like workpiece W during the grinding process, it is carried into a Z3-axis grinding apparatus, and Z3-axis machining (finish grinding) is performed. In the Z3-axis machining, the plate-like workpiece W is finish-ground on the chuck table 21 by the contact-type thickness measuring device 63. In this way, the subsequent grinding process is performed only for the plate-like workpiece W having no cracks. In Z3-axis machining, grinding is performed using a grinding wheel 48 having a finer grain size than Z2-axis machining. Moreover, in this Embodiment, although it was set as the structure which implements the measurement of the thickness of the plate-shaped workpiece W, and the detection of the crack of the plate-shaped workpiece W simultaneously, You may make it the structure which inserts the detection of a crack regularly.

  Furthermore, it may be configured to detect a crack in the plate-like workpiece W after the Z2-axis machining of the plate-like workpiece W is completed. In this case, the crack of the plate-like workpiece W may be detected after the Z2 axis machining by the Z2 axis grinding apparatus, or the plate before the Z3 axis machining by the Z3 axis grinding apparatus as shown in FIG. 5B. A crack of the workpiece W may be detected. Even in this configuration, the subsequent Z3-axis grinding is not performed in a state where the plate-like workpiece W is cracked, and the deterioration of the grinding wheel 48 can be suppressed, and the subsequent plate-like workpiece W can be prevented from cracking. In addition, it is not restricted to the structure which detects the crack of the plate-shaped workpiece W in either Z2 or Z3-axis machining, You may detect the crack of the plate-shaped workpiece W in all of Z1, Z2, and Z3-axis machining. In Z1 axis machining, cracks may occur. In Z1 axis machining, cracks may enter the outer peripheral edge of the plate-like workpiece W, and cracks may occur during Z2 axis grinding or Z3 axis grinding. For this reason, you may make it attach the optical sensor only for a crack detection also about the grinding apparatus of Z1-axis processing.

  As described above, in the grinding apparatus 1 according to the present embodiment, the measurement light is irradiated toward the plate-like workpiece W, and the crack of the plate-like workpiece W is determined from the change in the amount of reflected light received. Since the change in the amount of received light is monitored while grinding is continued, it is possible to immediately determine whether the plate-like workpiece W is cracked. Therefore, the crack of the plate-like workpiece W can be minimized, and the grinding process can be stopped before the grinding wheel 48 of the grinding means 41 deteriorates. It is possible to prevent the subsequent plate-like workpiece W from being cracked due to the above.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, in the above-described embodiment, the thickness detection unit is used as the crack detection unit to detect a crack in the plate-like workpiece. However, the present invention is not limited to this configuration. If the crack detection means is configured to receive the reflected light reflected from the plate-shaped workpiece by the measurement light emitted from the irradiation section, and detect the crack of the plate-shaped workpiece from the amount of light received, how It may be configured. For example, the crack detection means may be a detection device configured exclusively for detection of cracks in a plate-like workpiece, or may be configured by a height measurement means 71 such as a non-contact type height gauge as shown in FIG. Also good.

  In the head of the height measuring means 71, a reference reflecting surface 76 is provided as a measurement standard for the upper surface height of the plate-like workpiece W. The height measuring means 71 measures the upper surface height by the reflected light from the reference reflecting surface 76 in the head and the reflected light from the upper surface 81 of the plate-like workpiece W. The height measuring means 71 includes an irradiation unit 72 that irradiates measurement light from above the plate-like workpiece W, a light receiving unit 73 that receives reflected light reflected by the plate-like workpiece W, and a reference reflection surface 76. A height calculation unit 74 is provided for calculating the upper surface height of the plate-like workpiece W from the reflected light of the plate-like workpiece W and the reflected light from the upper surface 81 of the plate-like workpiece W.

  In addition, the height calculation unit 74 is provided with a determination unit 75 that determines whether the plate-like workpiece W is cracked from the amount of reflected light received by the light receiving unit 73, as in the thickness measuring unit 51 described above. The determination unit 75 determines that a crack has occurred in the plate-like workpiece W when the amount of reflected light reflected by the upper surface 81 of the plate-like workpiece W exceeds a preset allowable range. Even with such a configuration, it is possible to immediately detect a crack in the plate-like workpiece W and stop the grinding process before the deterioration of the grinding wheel 48 of the grinding means 41 proceeds. Can be prevented.

  In the above-described embodiment, the configuration for detecting cracks in the plate-like workpiece W when performing in-feed grinding has been described. However, it is also possible to detect cracks in the plate-like workpiece W during creep-feed grinding. is there.

  As described above, the present invention has the effect of minimizing the cracking of the plate-like workpiece, suppressing the deterioration of the grinding wheel, and preventing the subsequent plate-like workpiece from cracking. It is useful for a grinding apparatus for grinding a hard plate-like workpiece such as sapphire or silicon carbide.

DESCRIPTION OF SYMBOLS 1 Grinding device 21 Chuck table 22 Rotating means 41 Grinding means 46 Grinding wheel 48 Grinding wheel 51 Thickness measuring means (crack detecting means)
52, 72 Irradiation unit 53, 73 Light receiving unit 54 Thickness calculation unit 55, 75 Judgment unit 71 Height measurement means (crack detection means)
74 Height calculator 81 Upper surface of plate workpiece 82 Lower surface of plate workpiece 83 Crack of plate workpiece W Plate workpiece

Claims (2)

A chuck table for holding a plate-shaped workpiece, a rotating means for continuously rotating the chuck table, and a grinding means for grinding the plate-shaped workpiece holding the chuck table by continuously rotating the chuck table with a grinding wheel. A grinding device,
A crack detecting means for detecting a crack in the plate-like workpiece held by the chuck table to be ground by the grinding means;
The crack detection means receives an irradiation unit that emits measurement light from above the plate-shaped workpiece toward the upper surface of the plate-shaped workpiece, and reflected light that is reflected from the plate-shaped workpiece by the measurement light emitted from the irradiation unit. A grinding apparatus comprising: a light receiving unit; and a determination unit that determines that the reflected light is cracked when an amount of light received by the light receiving unit exceeds a preset allowable range. The crack detection means is a thickness measurement means provided with a thickness calculation unit for calculating the thickness of the plate-like workpiece,
The irradiation unit emits measurement light from above the plate-shaped workpiece toward the upper surface of the plate-shaped workpiece, and the light-receiving unit reflects the reflected light reflected by the upper surface of the plate-shaped workpiece and the lower surface of the plate-shaped workpiece. The thickness calculation unit calculates the thickness of the plate-like workpiece from the reflected light reflected by the upper surface and the lower surface of the plate-like workpiece,
The grinding apparatus according to claim 1, wherein the determining unit determines that the light is reflected when the light reflected by the upper surface received by the light receiving unit or the amount of reflected light reflected by the lower surface exceeds a preset allowable range. .

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