Grinding device and grinding method for workpiece

Abstract

To downsize a grinding device.SOLUTION: While a grinding stone 340 is continuously lowered, a chuck table 2 on which workpieces 17 that are held by a plurality of first holding parts 20 is continuously rotated, and the workpieces are ground to a first thickness set in advance. After that, a rotating speed of the chuck table 2 is made to be slower than that in the first step, and the grinding stone 340 is positioned at a different height for each of the workpieces 17 held by the plurality of first holding parts 20, and the workpieces are ground to a second thickness set in advance for each of the workpieces 17. In a grinding device 1, the first holding parts 20 are arranged in a circumferential direction, and since a gap between the workpiece 17 ground previously and the workpiece 17 to be ground next is provided between the first holding parts 20, the grinding device 1 can be downsized.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a grinding apparatus and a method for grinding a workpiece. [Background technology]

[0002] As disclosed in Patent Document 1, a grinding device that performs creep feed grinding on a workpiece positions the underside of a grinding wheel below the top surface of the workpiece held on a chuck table, moves the chuck table in a direction parallel to the underside of the grinding wheel, and grinds the workpiece with the side of the grinding wheel. As grinding progresses, the grinding wheel wears out, so the grinding wheel is lowered by the amount of wear to grind the workpiece to a specified thickness.

[0003] Furthermore, as disclosed in Patent Document 2, when creep feed grinding is performed on multiple workpieces and the ground workpieces are finished to different thicknesses, the height of the grinding wheel is changed for each workpiece. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Publication No. 1985-109859 [Patent Document 2] Japanese Patent Publication No. 2020-089930 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, a gap is provided between the workpiece that has been creep-feed ground previously and the workpiece to be creep-feed ground next so that the grinding wheel does not come into contact with the workpiece. This poses a problem of the creep-feed grinding device becoming larger. Therefore, a creep-feed grinding device that finishes multiple workpieces to different thicknesses faces the challenge of making the device smaller. [Means for solving the problem]

[0006] The grinding method of the present invention is a method for grinding a workpiece using a grinding device including a chuck table that rotates around its center axis, a table rotation mechanism that rotates the chuck table, a holding section having a plurality of holding surfaces arranged circumferentially around the radius of the chuck table and holding the workpiece, a grinding mechanism in which a grinding wheel is arranged to grind the top surface of the workpiece held in the holding section, a lifting mechanism that raises and lowers the grinding wheel in a direction perpendicular to the holding surface, and a control unit that controls the lifting mechanism.The method includes a first grinding step in which the chuck table, with the workpiece held in the holding section, is continuously rotated while continuously moving the grinding wheel downward, thereby grinding the workpiece to a predetermined first thickness, and a second grinding step in which the rotation speed of the chuck table is slower than in the first grinding step, the grinding wheel is positioned at a different height for each workpiece, and the workpiece is ground to a second thickness that is predetermined for each workpiece. [Effects of the Invention]

[0007] In the present invention, a plurality of first holding units are arranged in a ring on a stage, and the workpiece is creep-feed ground by rotating the chuck table. Therefore, unlike conventional creep-feed grinding machines, there is no need to move the chuck table linearly during creep-feed grinding, and the length of the chuck table movement mechanism can be shortened. Furthermore, shortening the movement mechanism allows for a smaller machine base, which in turn allows for a more compact grinding machine, which is advantageous.

[0008] According to the present invention, by controlling the lifting mechanism with the control unit and appropriately changing the height of the grinding wheel, it is possible to finish each workpiece held on each holding surface to a different finished thickness. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective view illustrating the entire grinding device. [Figure 2] FIG. 2 is a top view illustrating an example of a chuck table. [Figure 3] FIG. 2 is a top view illustrating an example of a chuck table. [Figure 4] FIG. 2 is a top view illustrating an example of a chuck table. [Figure 5] FIG. 2 is a top view illustrating an example of a chuck table. DETAILED DESCRIPTION OF THE INVENTION

[0010] The grinding apparatus 1 shown in FIG. 1 is a grinding apparatus that grinds a workpiece 17 using a grinding mechanism 3. The workpiece 17 has, for example, a first layer 18 having a substantially rectangular parallelepiped shape and a second layer 19 having a substantially rectangular parallelepiped shape superimposed on an upper surface 180 of the first layer 18. In this embodiment, the first layer 18 is formed to be larger in the longitudinal direction than the second layer 19. The grinding apparatus 1 grinds a plurality of workpieces 17, and the first layers 18 of the plurality of workpieces 17 do not all have the same thickness. Furthermore, the second layers 19 of the plurality of workpieces 17 do not all have the same thickness.

[0011] The following describes the grinding device 1. As shown in Fig. 1, the grinding device 1 includes a base 10 extending in the Y-axis direction, and a column 11 erected on the +Y direction side of the base 10.

[0012] A chuck table 2 is disposed on the base 10. The chuck table 2 includes a disk-shaped stage 21 and a frame 22 that supports the stage 21. An upper surface 210 of the stage 21 is provided with a first area 91, a second area 92, a third area 93, and a fourth area 94 that are circumferentially separated. Each area is provided with four substantially rectangular parallelepiped first holding portions 20 that are arranged circumferentially on the radius portion of the chuck table 2. In this embodiment, the four first holding portions 20 of the same shape are arranged at equal intervals of approximately 90 degrees in the circumferential direction so as to have rotational symmetry. As shown in Figure 2, lines 80 and 81 connecting points at equal distances from adjacent first holding units 20 form an angle of 90 degrees, and the first holding unit 20 is configured so that the angle θ formed by one apex angle 202 on the inside of the first holding unit 20, the center 2100 of the stage 21, and the other apex angle 203 on the inside of the first holding unit 20 is smaller than 90 degrees.

[0013] The above-mentioned radial portion of the chuck table 2 refers to the portion from the outer periphery of the stage 21 to the center 2100. The first holding parts 20 are sized to fit within the portion from the outer periphery of the stage 21 to the center 2100, and the first holding parts 20 are arranged so as not to overlap each other. The first holding parts 20 have a holding surface 200 that holds the workpiece 17. The holding surface 200 has a shape that is substantially identical to the top surface 180 of the first layer 18 of the workpiece 17. The top surface 220 of the frame 22 is formed flush with the holding surface 200.

[0014] A suction source (not shown) is connected to each holding surface 200. By operating the suction source, a suction force is transmitted to the holding surface 200, which is the upper surface of the first holding part 20. For example, by exerting the suction force of the suction source while the workpiece 17 is placed on the holding surface 200, the workpiece 17 can be sucked and held by the holding surface 200.

[0015] 1, an internal base 100 is disposed inside the base 10. A horizontal movement mechanism 5 that moves the chuck table 2 in the horizontal direction (Y-axis direction) is disposed on the internal base 100.

[0016] The horizontal movement mechanism 5 includes a ball screw 50 having a rotation axis 55 in the Y-axis direction, a pair of guide rails 51 arranged parallel to the ball screw 50, a Y-axis motor 52 connected to the ball screw 50 and rotating the ball screw 50 around the rotation axis 55, and a movable plate 53 whose bottom nut is threaded onto the ball screw 50 and moves in the Y-axis direction along the guide rails 51.

[0017] In the horizontal movement mechanism 5, when the ball screw 50 is driven by the Y-axis motor 52 and rotates about the rotation axis 55, the movable plate 53 moves in the Y-axis direction while being guided by the guide rail 51.

[0018] A table rotation mechanism 26 that rotatably supports the chuck table 2 is disposed on an upper surface 530 of the movable plate 53, and an annular base 23 is disposed around the table rotation mechanism 26.

[0019] For example, three (two are shown in FIG. 1) through-holes 230 are formed at equally spaced positions on the same circumference of the base 23, and three (two are shown in FIG. 1) support pillars 24 that support the base 23 are erected on the upper surface 530 of the movable plate 53. Each through-hole 230 is penetrated by a corresponding support pillar 24, and the support pillars 24 are supported on the upper surface 530 of the movable plate 53. A height adjustment mechanism 240 is disposed between each support column 24 and the upper surface 530 of the movable plate 53. The height adjustment mechanism 240 includes, for example, a piezoelectric actuator. The height adjustment mechanism 240 can adjust the inclination of the chuck table 2 by appropriately raising and lowering each support column 24 in the Z-axis direction. The height adjustment mechanism 240 may include a ball screw.

[0020] The table rotation mechanism 26 includes, for example, a motor (not shown). By operating the motor, the chuck table 2 can be rotated around a rotation axis 25 in the Z-axis direction that passes through the center 2100 of the upper surface 210 of the stage 21.

[0021] Furthermore, when the horizontal movement mechanism 5 moves the movable plate 53 in the Y-axis direction, the table rotation mechanism 26 and the chuck table 2 move integrally with the movable plate 53 in the Y-axis direction.

[0022] A cover 27 and a bellows 28 connected to the cover 27 so as to be freely expandable and contractible are disposed around the periphery of the chuck table 2. When the chuck table 2 moves in the Y-axis direction, the cover 27 moves in the Y-axis direction together with the chuck table 2, causing the bellows 28 to expand and contract.

[0023] An elevation mechanism 4 that supports the grinding mechanism 3 so that it can be raised and lowered is disposed on the side surface on the -Y direction side of the column 11. The grinding mechanism 3 includes a spindle 30 having a rotation axis 35 in the Z-axis direction, a housing 31 that rotatably supports the spindle 30, a spindle motor 32 that rotates and drives the spindle 30 around the rotation axis 35, a mount 33 connected to the lower end of the spindle 30, and a grinding wheel 34 that is detachably attached to the underside of the mount 33.

[0024] The grinding wheel 34 includes a wheel base 341 and a plurality of grinding stones 340 each having a substantially rectangular parallelepiped shape and arranged in a ring shape on the underside of the wheel base 341. A lower surface 342 and a side surface 343 of the grinding stone 340 are surfaces that come into contact with the workpiece 17 when the workpiece 17 is ground.

[0025] When the spindle 30 is driven by the spindle motor 32 and rotates, the mount 33 connected to the spindle 30 and the grinding wheel 34 attached to the underside of the mount 33 rotate together.

[0026] The lifting mechanism 4 includes a ball screw 40 having a rotation axis 45 in the Z-axis direction, a pair of guide rails 41 arranged parallel to the ball screw 40, a Z-axis motor 42 that rotates the ball screw 40 around the rotation axis 45, a lifting plate 43 whose internal nut is threaded onto the ball screw 40 and whose side is in sliding contact with the guide rails 41, and a holder 44 connected to the lifting plate 43 and supporting the grinding mechanism 3.

[0027] When the ball screw 40 is driven by the Z-axis motor 42 and rotates around the rotation shaft 45, the lifting plate 43 is guided by the guide rail 41 and moves up and down in the Z-axis direction together with the holder 44. Accordingly, the grinding wheel 340 of the grinding mechanism 3 held by the holder 44 moves up and down in the Z-axis direction, which is a direction perpendicular to the holding surface 200.

[0028] The grinding apparatus 1 includes a control unit 8 that controls various operations of the grinding apparatus 1. For example, the control unit 8 controls the lifting operation of the grinding mechanism 3 by the lifting mechanism 4. The control unit 8 also has a function of storing a target thickness of the workpiece 17 to be ground after grinding.

[0029] The grinding apparatus 1 is equipped with a thickness measurement mechanism 7. The thickness measurement mechanism 7 may include, for example, a non-contact upper surface height gauge 70 that measures the height of the upper surface 190 of the second layer 19 of the workpiece 17 and a non-contact holding surface height gauge 71 that measures the height of the holding surface 200, and the thickness of the workpiece 17 can be measured by calculating the difference between the heights measured by the two height gauges. The upper surface height gauge 70 and the holding surface height gauge 71 may be contact-type. The thickness measurement mechanism 7 may also be capable of receiving light reflected by the upper surface 190 of the second layer 19 of the workpiece 17 and light reflected by the lower surface of the second layer 19, and measuring the thickness of the second layer 19 from the optical path difference.

[0030] (First grinding process) When grinding workpieces 17 using the grinding device 1 shown in FIG. 1, first, an operator sets the first thickness and the second thickness of the plurality of workpieces 17 in advance, and stores the set first thickness and second thickness in the control unit 8.

[0031] Here, the first thickness is the thickness after the first grinding process, and is a thickness of a common size for the plurality of workpieces 17. The second thickness is the thickness after the second grinding process (described later), and is a so-called finishing thickness. The second thickness is a thickness that is set as a different size for each of the plurality of workpieces 17.

[0032] Next, the operator or control unit 8 places the workpiece 17 on each of the multiple holding surfaces 200 of the chuck table 2 so that the first layer 18 of the workpiece 17 contacts the holding surface 200, and activates the suction source. As a result, the holding surface 200 of each of the first holding parts 20 of the chuck table 2 suction-holds the first layer 18 side of the workpiece 17.

[0033] With the workpiece 17 held on each holding surface 200, the control unit 8 moves the chuck table 2 an appropriate distance in the +Y direction using the horizontal movement mechanism 5. As a result, the grinding wheel 340 is positioned above the workpiece 17, as shown in FIG. At this time, the grinding stone 340 is disposed outside the center 2100 of the upper surface 210 of the stage 21 of the chuck table 2. In other words, the grinding stone 340 is disposed in a horizontal position so as not to overlap with the center 2100 of the stage 21 of the chuck table 2.

[0034] Next, the control unit 8 rotates the grinding wheel 340 around the rotation shaft 35 by the spindle motor 32 shown in FIG.

[0035] Then, while the grinding wheel 340 is rotating around the rotation shaft 35, the control unit 8 causes the lifting mechanism 4 to lower the grinding mechanism 3 in the −Z direction at an appropriate speed.

[0036] Furthermore, the control unit 8 causes the table rotation mechanism 26 to rotate the chuck table 2 counterclockwise around the center 2100 of the stage 21 as an axis at a speed of, for example, 300 rpm. As a result, the workpieces 17 held on each holding surface 200 also rotate counterclockwise around the center 2100 of the stage 21 as an axis.

[0037] In this way, the control unit 8 continuously moves the grinding wheel 340 downward (in the -Z direction) while continuously rotating the chuck table 2 on which the workpiece 17 is held by the first holding unit 20. As a result, the lower surface 342 of the grinding wheel 340 comes into contact with the workpiece 17 held by the four holding surfaces 200 in turn, and performs in-feed grinding on the upper surface 190 of the second layer 19 of each workpiece 17. During grinding, the control unit 8 uses the thickness measurement mechanism 7 to measure the thickness of the workpiece 17 held on the holding surface 200. Then, the control unit 8 grinds the second layer 19 of the workpiece 17 until the thickness of the workpiece 17 reaches the preset first thickness. Therefore, the second layer 19 of the workpiece 17 does not have the same thickness after grinding.

[0038] (Second grinding process) Next, the control unit 8 controls the table rotation mechanism 26 to stop the rotation of the chuck table 2 so that the arc-shaped grinding area 344 of the grinding wheel 340 is positioned between the first area 91 and the fourth area 94. Here, the grinding area 344 is the area of ​​the grinding wheel 340 that comes into contact with the second layer 19 of the workpiece 17 during creep feed grinding of the workpiece 17. The control unit 8 controls the lifting mechanism 4 to lower the grinding wheel 340 an appropriate distance in the -Z direction. As a result, the lower surface 342 of the grinding wheel 340 is positioned at a height corresponding to the second thickness of the workpiece 17 held on the holding surface 200 of the first area 91, and the lower surface 342 of the grinding wheel 340 is positioned below the upper surface 190 of the second layer 19 of the workpiece 17. Thereafter, the control unit 8 controls the table rotation mechanism 26 to change the rotation speed of the chuck table 2 to a speed slower than the rotation speed of the chuck table 2 in the first grinding step, and rotates the chuck table 2 again. At this time, the control unit 8 sets the rotation speed of the chuck table 2 to, for example, 10 rpm and rotates the chuck table 2. As the chuck table 2 rotates, the workpiece 17 held on the holding surface 200 of the first area 91 and the grinding wheel 340 approach each other in the horizontal direction, and the side surface 343 of the grinding wheel 340 comes into contact with the side surface 193 of the second layer 19 of the workpiece 17 held on the holding surface 200 of the first area 91, thereby creep feed grinding the upper surface 190 of the second layer 19 of the workpiece 17. The holding surface 200 is formed so as to be parallel to the lower surface 342 of the grinding area 344 of the grinding wheel 340 . In the second grinding process, when the thickness measurement mechanism 7 measures the thickness of only the second layer 19, the thickness of the second layer 19 of each workpiece 17 is set as the second thickness, and the grinding wheel 340 is raised and lowered for each workpiece 17 to position the lower surface 342 of the grinding wheel 340 at a height position for each workpiece 17 so that the thickness of the second layer 19 measured by the thickness measurement mechanism 7 becomes the set second thickness. Furthermore, when the thickness measurement mechanism 7 measures the thickness of the workpieces 17 and the thickness of the second layer 19 of each workpiece 17, the thickness of each workpiece 17 and the thickness of the second layer 19 of each workpiece 17 may be measured before the second grinding process is started, and the thickness of the first layer 18 for each workpiece 17 and the grinding order of the workpieces 17 according to the rotation direction of the chuck table 2 may be stored. The thickness of each workpiece 17 may then be measured by the thickness measurement mechanism 7, and the thickness of the second layer 19 may be calculated by subtracting the stored thickness of the first layer 18 from the measured thickness of the workpiece, while the second layer 19 of each workpiece 17 is ground to a uniform thickness. The thickness of the first layer 18 may be measured and stored before the first grinding step. The thickness of the first layer 18 of the workpiece 17 held in the first holding part 20 may be stored in the grinding device 1 in advance by an operator or the like.

[0039] 2, the first holding unit 20 is disposed so that the angle θ shown in FIG. 2 is smaller than 90 degrees. Therefore, when the chuck table 2 rotates by 90 degrees after the side surface 343 of the grinding wheel 340 begins to contact the workpiece 17 held on the holding surface 200 of the first area 91, the workpiece 17 passes the grinding wheel 340, and the grinding wheel 340 grinds the entire upper surface 190 of the second layer 19 of the workpiece 17. Thereafter, the grinding area 344 of the grinding wheel 340 is positioned between the first area 91 and the second area 92.

[0040] Here, the control unit 8 raises and lowers the grinding wheel 340 using the lifting mechanism 4, and positions the lower surface 342 of the grinding wheel 340 at a height position corresponding to the second thickness of the workpiece 17 held on the holding surface 200 in the second area 92.

[0041] Thereafter, as the chuck table 2 rotates, the side surface 343 of the grinding wheel 340 comes into contact with the workpiece 17 held on the holding surface 200 of the second area 92. After the side surface 343 of the grinding wheel 340 begins to come into contact with the workpiece 17, the chuck table 2 rotates by 90 degrees, causing the workpiece 17 to pass through the grinding wheel 340, which then grinds the entire surface of the second layer 19 of the workpiece 17. The grinding area 344 of the grinding wheel 340 is then positioned between the second area 92 and the third area 93.

[0042] Thereafter, the control unit 8 grinds the workpiece 17 in the third area 93 and the fourth area 94 in the same manner. That is, the control unit 8 positions the lower surface 342 of the grinding wheel 340 at a height position corresponding to the second thickness of the workpiece 17 held on the holding surface 200 of the third area 93. As a result, as the chuck table 2 rotates 90 degrees, the entire upper surface 190 of the workpiece 17 is ground, and the grinding area 344 of the grinding wheel 340 is positioned between the second area 92 and the third area 93. Thereafter, the control unit 8 positions the lower surface 342 of the grinding wheel 340 at a height position corresponding to the second thickness of the workpiece 17 held on the holding surface 200 of the fourth area 94, and grinds the entire upper surface 190 of the workpiece 17.

[0043] In this way, as the chuck table 2 rotates, each time a workpiece 17 held on each holding surface 200 passes over the grinding wheel 340, the control unit 8 changes the height position of the grinding wheel 340 using the lifting mechanism 4, positions the grinding wheel 340 at a different height for each workpiece 17, and adjusts the finishing thickness for each workpiece 17.

[0044] During the grinding process, the control unit 8 measures the thickness of the workpiece 17 using the thickness measurement mechanism 7. The control unit 8 may repeatedly perform the grinding process until the thickness of the workpiece 17 held on each holding surface 200 of the first area 91, the second area 92, the third area 93, and the fourth area 94 reaches a second thickness, which is a predetermined desired finish thickness of each workpiece 17. In other words, the lower surface 342 of the grinding area 344 of the grinding wheel 340 may be lowered in stages, and the chuck table 2 may be rotated each time the lower surface 342 of the grinding wheel 340 is lowered, to grind the second layer 19 of the workpiece 17.

[0045] As described above, by grinding a plurality of workpieces 17 using the grinding method using the grinding device 1, the workpieces 17 held on each holding surface 200 can be finished to a second thickness that differs for each workpiece 17.

[0046] Furthermore, according to the above-described grinding method using the grinding device 1, even if the thickness of the first layer 18 and the thickness of the second layer 19 of each workpiece 17 are different, the control unit 8 controls the lifting mechanism 4 to appropriately change the height of the grinding wheel 340 and appropriately change the amount of grinding for each second layer 19, thereby making it possible to finish the thickness of the second layer 19 of each workpiece 17 to the same thickness. For example, if the second layer 19 of the workpiece 17 is a semiconductor layer and the first layer 18 is a protective layer, the grinding method using the grinding device 1 can grind only the semiconductor layer to the same thickness in multiple workpieces 17. This type of grinding process makes it possible to manufacture workpieces with protective members of different thicknesses but semiconductor layers of the same thickness, which is significant from the perspective of product diversification, etc.

[0047] The grinding apparatus 1 also includes a plurality of first holding units 20 arranged in a ring shape on the stage 21, and creep feed grinds the workpiece 17 by rotating the chuck table 2. Therefore, unlike conventional creep feed grinding apparatuses, there is no need to move the chuck table 2 linearly during creep feed grinding, and the length of the horizontal movement mechanism 5 in the Y-axis direction can be shortened. Furthermore, shortening the length of the horizontal movement mechanism 5 in the Y-axis direction makes it possible to reduce the size of the base 10, and therefore the size of the grinding apparatus, which is preferable.

[0048] Furthermore, if the lower surface 342 of the grinding wheel 340 is parallel to the holding surface 200 of the first holding portion 20 of the chuck table 2, and if the grinding wheel 340 can grind the entire upper surface 190 of the second layer 19 of the workpiece 17 held on the holding surface 200 as the chuck table 2 rotates, the positional relationship between the grinding wheel 340 and the center 2100 of the upper surface 210 of the stage 21 during creep feed grinding may be such that the center 2100 of the upper surface 210 of the stage 21 of the chuck table 2 is positioned inside the ring formed by the grinding wheel 340, or such that the center 2100 of the upper surface 210 of the stage 21 overlaps with the grinding wheel 340.

[0049] The grinding device 1 may be provided with a large diameter grinding wheel 36 as shown in FIG. The large diameter grinding wheel 36 includes a second grinding stone 360 ​​arranged to form a ring having a diameter larger than the radius of the stage 21 . The second grinding wheel 360 has a grinding area 364 that comes into contact with the workpiece 17 during creep feed grinding of the workpiece 17. In the grinding area 364, the lower surface of the second grinding wheel 360 is parallel to the holding surface 200 of the first holding part 20 of the chuck table 2.

[0050] 4 shows how the workpiece 17 held on the holding surface 200 of the first area 91 is creep feed ground by the second grinding wheel 360. With the center 2100 of the upper surface 210 of the stage 21 of the chuck table 2 positioned inside the ring formed by the second grinding wheel 360, the grinding area 364 of the second grinding wheel 360 is brought into contact with the workpiece 17, thereby creep feed grinding the workpiece 17.

[0051] The stage 21 of the chuck table 2 may be formed in a conical shape with its center 2100 as its apex. Alternatively, the stage 21 may be formed in a truncated conical shape having a small circular flat area 211 including the center 2100. In this way, when the stage 21 is formed in a conical or truncated conical shape, a plurality of first holding parts 20 having inclined holding surfaces 200 are arranged on the upper surface 210 of the stage 21. In this case as well, in the grinding area 364 , the lower surface of the second grinding wheel 360 is arranged parallel to the holding surface 200 of the first holding part 20 of the chuck table 2 .

[0052] The holding surface 200 of each first holding portion 20 may be formed flush with the upper surface 210 of the stage 21.

[0053] Furthermore, when the second grinding wheel 360 is used, the lower surface 362 of the second grinding wheel 360 may be arranged to overlap the center 2100 of the stage 21 of the chuck table 2 during creep feed grinding.

[0054] As shown in Fig. 5, the grinding apparatus 1 may include six second holding portions 29 arranged circumferentially on the radial portion of the chuck table 2 and having holding surfaces 290 for holding the workpiece 17. In the example of Fig. 5, six second holding portions 29 of the same shape are arranged at equal intervals in the circumferential direction so as to have rotational symmetry. The second holding portions 29 are formed so as to extend from a center 2100 of the upper surface 210 of the stage 21 in the radial direction of the circle of the stage 21. Each second holding portion 29 has a size that can fit within the portion from the outer periphery of the stage 21 to the center 2100, and is arranged on the radial portion of the chuck table 2 so as not to overlap each other. Even in this case, the workpiece 17 is held on the holding surface 290, which is the upper surface of each second holding portion 29, and the first grinding process and the second grinding process are performed, so that the workpieces 17 held on each holding surface 290 can be finished to have different finished thicknesses. [Explanation of symbols]

[0055] 1: Grinding device 10: Base 11: Column 17: Workpiece 18: First layer 19: Second layer 100: Internal base 180: Top surface 190: Top surface 193: Side surface 2: Chuck table 20: First holding part 21: Stage 211: Flat area 22: Frame 23: Base 24: Support column 25: Rotating shaft 26: Table rotation mechanism 27: Cover 28: Bellows 29: Second holding part 200: Holding surface 210: Top surface 220: Top surface 230: Through hole 202: One of the inner vertices 203: The other inner vertex θ: Angle between one of the inner vertices, the center of the stage, and the other inner vertex 80: Straight line 81: Straight line 240: Height adjustment mechanism 29: Holding surface 2100: Center 3: Grinding mechanism 30: Spindle 31: Housing 32: Spindle motor 33: Mount 34: Grinding wheel 35: Rotating shaft 340: Grinding wheel 341: Wheel base 342: Underside 343: Side 36: Large diameter grinding wheel 360: Second grinding wheel 4: Lifting mechanism 40: Ball screw 41: Guide rail 42: Z-axis motor 43: Lifting plate 44: Holder 45: Rotating shaft 5: Horizontal movement mechanism 50: Ball screw 51: Guide rail 52: Y-axis motor 53: Movable plate 55: Rotating shaft 530: Top surface 7: Thickness measuring mechanism 70: Upper surface height gauge 71: Holding surface height gauge 8: Control unit 91: Area 1 92: Area 2 93: 3rd Area 94: 4th Area

Claims

[Claim 1] A method for grinding a workpiece using a grinding device including: a chuck table that rotates around a center axis; a table rotation mechanism that rotates the chuck table; a holding unit having a plurality of holding surfaces that are arranged circumferentially around a radial portion of the chuck table and that hold the workpiece; a grinding mechanism in which a grinding wheel is arranged to grind the top surface of the workpiece held in the holding unit; an elevation mechanism that raises and lowers the grinding wheel in a direction perpendicular to the holding surface; and a control unit that controls the elevation mechanism, a first grinding step in which the chuck table, with the workpiece held by the holding portion, is continuously rotated while the grinding wheel is continuously moved downward, thereby grinding the workpiece to a predetermined first thickness; a second grinding step in which the rotation speed of the chuck table is slower than that of the first grinding step, the grinding wheel is positioned at a different height for each workpiece, and the workpiece is ground to a second thickness that is preset for each workpiece; A method for grinding a workpiece, comprising:

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