Grinding method of tabular workpiece and grinding device

Abstract

To improve workability at the time of grinding a tabular workpiece having a warp projecting at a center.SOLUTION: The present invention is a grinding method of a tabular workpiece of grinding a tabular workpiece (W) projecting at a center by a grindstone (97). This grinding method includes: a first holding step of sucking and holding the tabular workpiece by a holding surface (46) having a shape in which a center of a first chuck table (41) projects more than an outer periphery; a reaction force reduction grinding step of grinding a center portion (W3) of the tabular workpiece by the grindstone to reduce a reaction force when the tabular workpiece is made to be flat; a second holding step of sucking and holding the tabular workpiece by a holding surface (56) parallel to a lower surface of the grindstone of the second chuck table (42); and a finish grinding step of finish-grinding the tabular workpiece by the grindstone.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for grinding a plate-shaped workpiece using a chuck table for holding the plate-shaped workpiece. [Background technology]

[0002] Patent Document 1 discloses a grinding method for grinding a warped plate-shaped workpiece with a rotating grinding wheel. In Patent Document 1, in order to hold the warped plate-shaped workpiece on a chuck table, tape is attached to the outer periphery of the surface of the plate-shaped workpiece that becomes concave due to the warp. By attaching the tape in this way, a space is formed between the tape and the concave surface, and the plate-shaped workpiece is held on the chuck table via the tape with this space formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-062460 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned method of applying the tape involves the burden of forming a closed space at the same time as the application, which reduces workability.

[0005] The present invention has been made in consideration of these points, and one of its objects is to provide a method and a grinding device for plate-shaped workpieces that can improve workability when grinding plate-shaped workpieces that are warped so that the center is raised. [Means for solving the problem]

[0006] One embodiment of the method for grinding a plate-shaped workpiece of the present invention is a method for grinding a plate-shaped workpiece with a raised center using a grinding wheel, and includes a first holding step in which the plate-shaped workpiece is suction-held on a holding surface of a first chuck table, the holding surface of which is raised higher than the outer periphery in the center, a reaction force reduction grinding step in which the central portion of the plate-shaped workpiece is ground with the grinding wheel to reduce the reaction force when flattening the plate-shaped workpiece, a second holding step in which the plate-shaped workpiece is suction-held on a holding surface of a second chuck table, the holding surface being parallel to the underside of the grinding wheel, and a finish grinding step in which the plate-shaped workpiece is finish-ground with the grinding wheel.

[0007] One embodiment of the present invention provides a grinding device for plate-shaped workpieces that enables the above-mentioned grinding method for plate-shaped workpieces, and includes at least a first chuck table having a holding surface that is raised relative to the underside of the grinding wheel, a second chuck table having a holding surface that is parallel to the underside of the grinding wheel, and a grinding mechanism that grinds the plate-shaped workpiece held by suction on the first chuck table and the second chuck table.

[0008] Another embodiment of the method for grinding a plate-shaped workpiece according to the present invention is a method for grinding a plate-shaped workpiece with a raised center using a grinding wheel, and includes a first holding step in which the plate-shaped workpiece is suction-held with the raised center by a holding surface of a chuck table that is parallel to the underside of the grinding wheel; a reaction force reduction grinding step in which the central portion of the plate-shaped workpiece is ground with the grinding wheel to reduce the reaction force when flattening the plate-shaped workpiece; a second holding step in which the plate-shaped workpiece is suction-held with the holding surface of the chuck table with no gap between the holding surface and the underside of the plate-shaped workpiece; and a finish grinding step in which the plate-shaped workpiece is finish-ground with the grinding wheel.

[0009] Another aspect of the grinding device of the present invention is a grinding device that enables the above-mentioned method for grinding a plate-shaped workpiece, and includes at least the chuck table having the holding surface, a suction path connecting the holding surface to a suction source, a pressure adjustment unit disposed in the suction path for adjusting the negative pressure value of the holding surface, and a grinding mechanism for grinding the plate-shaped workpiece held by suction on the chuck table.

[0010] Yet another aspect of the grinding device of the present invention is a grinding device that enables the above-mentioned method for grinding a plate-shaped workpiece, and includes at least a chuck table having at least two holding surfaces, namely, a concentric central holding surface and an outer peripheral holding surface, a central suction path that connects the central holding surface to a suction source, an outer peripheral suction path that connects the outer peripheral holding surface to the suction source, an area change unit that changes the area of ​​the holding surface, and a grinding mechanism that grinds the plate-shaped workpiece held by suction on the chuck table. [Effects of the Invention]

[0011] According to the present invention, a plate-shaped workpiece is held by a holding surface having a shape in which the center is raised higher than the outer periphery, or the plate-shaped workpiece is held in a raised state at the center, and then the center portion of the plate-shaped workpiece can be ground with a grinding wheel. This reduces the reaction force when flattening the plate-shaped workpiece before grinding it flat, allowing for finish grinding. This makes it possible to grind a plate-shaped workpiece with a raised center without applying tape to form an enclosed space as in the past. Therefore, the present invention improves workability when grinding a plate-shaped workpiece that is warped so that the center is raised. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. [Figure 2] 1 is a schematic perspective view of a grinding device according to a first embodiment. [Figure 3] 3A and 3B are schematic cross-sectional views of the first chuck table and its periphery according to the first embodiment. [Figure 4] 4A and 4B are schematic cross-sectional views of the second chuck table and its periphery according to the first embodiment. [Figure 5] 5A and 5B are schematic cross-sectional views of the chuck table and its surroundings according to the second embodiment. [Figure 6] 6A and 6B are schematic cross-sectional views of the chuck table and its periphery according to the second embodiment. [Figure 7] 7A and 7B are schematic cross-sectional views of a universal chuck table and its periphery according to the third embodiment. [Figure 8] 8A and 8B are schematic cross-sectional views of the universal chuck table and its periphery according to the third embodiment. [Figure 9] 9A and 9B are schematic cross-sectional views of the chuck table and its periphery according to the fourth embodiment. [Figure 10] 10A and 10B are schematic cross-sectional views of the chuck table and its periphery according to the fourth embodiment. [Figure 11] 11A and 11B are schematic cross-sectional views of a modified chuck table and its surroundings. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] A method and apparatus for grinding a plate-shaped workpiece according to a first embodiment will be described below with reference to the accompanying drawings. First, a plate-shaped workpiece W to be ground will be described, as shown in FIG. 1. The plate-shaped workpiece W is, for example, a disc-shaped wafer having a thickness of 2.5 mm. FIG. 1 is a cross-sectional view of the plate-shaped workpiece W before grinding. As shown in FIG. 1, the plate-shaped workpiece W has a warp that rises in the center, and a first surface W1, which is one surface in the thickness direction, is formed convexly, and a second surface W2, which is the other surface in the thickness direction, is formed concavely. Furthermore, although the plate-shaped workpiece W is not particularly limited, in this embodiment, a workpiece having elasticity that generates a reaction force against a force applied to flatten the workpiece before grinding is used. For example, for a plate-shaped workpiece W having a thickness of 2.5 mm, the warp amount at the center where the warp is greatest is set to 2 mm.

[0014] Next, we will explain the grinding device 10 that performs grinding on the plate-shaped workpiece W. Fig. 2 is a schematic perspective view of the grinding device of the first embodiment. The X-axis, Y-axis, and Z-axis directions shown in each drawing are perpendicular to one another. The X-axis and Y-axis directions are approximately horizontal, and the Z-axis direction is the up-down direction. Of the two arrows indicating the X-axis direction, the +X side is the right side and the -X side is the left side. Of the two arrows indicating the Y-axis direction, the +Y side is the rear side and the -Y side is the front side. Of the two arrows indicating the Z-axis direction, the +Z side is the up side and the -Z side is the down side.

[0015] The grinding device 10 is configured to fully automatically perform a series of operations, including a loading process, grinding process, cleaning process, and unloading process, on a plate-shaped workpiece W. The plate-shaped workpiece W is loaded into the grinding device 10 while being housed in a cassette 11.

[0016] Two cassettes 11 capable of accommodating a plurality of plate-shaped workpieces W are placed on the −Y direction side of the base 12 of the grinding device 10. One cassette 11 accommodates plate-shaped workpieces W before grinding, and the other cassette 11 accommodates plate-shaped workpieces W after grinding. A robot hand 14 is provided behind the cassettes 11 to put the plate-shaped workpieces W into and take them out of the cassettes 11.

[0017] The grinding device 10 is equipped with a control unit 16 that is configured with a processor that executes various processes, a memory that stores programs, etc. The grinding device 10 is configured to fully automatically perform a series of operations such as loading, grinding, cleaning, and unloading of the plate-shaped workpiece W by control signals that the control unit 16 sends to each unit in accordance with the program stored in the memory of the control unit 16.

[0018] A positioning mechanism 18 for placing the plate-shaped workpiece W before grinding and a spinner cleaning device 19 for cleaning the ground plate-shaped workpiece W are provided diagonally to the left and right of the robot hand 14. The robot hand 14 transports the plate-shaped workpiece W before grinding from the cassette 11 to the positioning mechanism 18, and transports the ground plate-shaped workpiece W from the spinner cleaning device 19 to the cassette 11.

[0019] The positioning mechanism 18 is configured by arranging a plurality of positioning pins 23 around the temporary placement table 22, which are movable toward and away from the center of the temporary placement table 22. In the positioning mechanism 18, the plurality of positioning pins 23 abut against the outer peripheral edge of the plate-shaped workpiece W placed on the temporary placement table 22, thereby positioning the center of the plate-shaped workpiece W to the center of the temporary placement table 22.

[0020] The spinner cleaning device 19 cleans the ground plate-shaped workpiece W by supplying cleaning liquid from a cleaning nozzle 25 to the ground plate-shaped workpiece W and rotating a spinner table 26 holding the plate-shaped workpiece W at high speed using a motor (not shown).

[0021] A support block 28 extending in the Y-axis direction is provided between the positioning mechanism 18 and the spinner cleaning device 19 on the base 12, and a column 29 is erected at the rear of the base 12. Here, the grinding device 10 includes a transport mechanism 30 provided on the support block 28, and a holding device 40 provided on the base 12 between the transport mechanism 30 and the column 29. The holding device 40 includes a first chuck table 41 and a second chuck table 42 arranged on a turntable 43.

[0022] The transport mechanism 30 transports the plate-shaped workpiece W onto the first chuck table 41 and the second chuck table 42, and transports the plate-shaped workpiece W from the first chuck table 41 and the second chuck table 42. The transport mechanism 30 transports the plate-shaped workpiece W between the first chuck table 41 or the second chuck table 42, which is positioned at a forward loading / unloading position, the temporary placement table 22, and the spinner table 26.

[0023] The transport mechanism 30 includes a transport pad 31 capable of suction-holding the top surface of the plate-shaped workpiece W, and a rotating unit 32 that rotates (pivots) the transport pad 31 around an axis extending in the Z-axis direction. It also includes a lifting mechanism 33 that supports the transport pad 31 so that it can move up and down in the Z-axis direction, and a Y-axis moving mechanism 34 that moves the transport pad 31 in the Y-axis direction. The rotating unit 32 is supported by the lifting mechanism 33, which in turn is supported by a Y-axis moving unit 37 (described later) of the Y-axis moving mechanism 34. The transport pad 31 is supported on the tip side of an arm 35 that extends horizontally from the lower end of the rotating unit 32. The rotating unit 32 and the lifting mechanism 33 each rotate and lift the arm 35 using the driving forces of a motor or actuator (not shown).

[0024] The Y-axis movement mechanism 34 includes a pair of guide rails 36 that are disposed on the surface of the support block 28 on the +X-direction side and extend in the Y-axis direction, a Y-axis movement unit 37 that is supported via the pair of guide rails 36 so as to be movable in the Y-axis direction, a ball screw 38 that extends in the Y-axis direction and is threadedly engaged with a threaded portion (not shown) of the Y-axis movement unit 37, and a motor 39 that rotates the ball screw 38. When the ball screw 38 is rotated by the driving of the motor 39, the Y-axis movement unit 37 moves in the Y-axis direction. When the Y-axis movement unit 37 moves in the Y-axis direction, the arm 35 that is supported by the Y-axis movement unit 37 via the rotation unit 32 and the lifting mechanism 33 also moves in the Y-axis direction, and as a result, the position of the transport pad 31 changes in the Y-axis direction.

[0025] The transport mechanism 30 moves the transport pad 31 horizontally by using the rotational movement of the rotating unit 32 and the movement in the Y-axis direction by the Y-axis movement mechanism 34. The transport mechanism 30 also moves the transport pad 31 up and down in the Z-axis direction by using the lifting mechanism 33 to lift the transport pad 31. These movements make it possible to transport the plate-shaped workpiece W between the first chuck table 41 or the second chuck table 42 positioned at the loading / unloading position, the temporary placement table 22, and the spinner table 26.

[0026] The turntable 43 in the holding device 40 is disk-shaped and supported rotatably about an axis extending in the Z-axis direction. The turntable 43 rotates by driving a motor of a turntable rotation mechanism (not shown).

[0027] The first chuck table 41 and the second chuck table 42 are arranged in positions symmetrical to each other with respect to the rotation center of the turntable 43 (the centers of the first chuck table 41 and the second chuck table 42 are positioned 180° apart from each other in the rotation direction of the turntable 43). The first chuck table 41 and the second chuck table 42 are positioned at grinding positions located on the +Y direction side and +X direction side of the rotation center of the turntable 43, and at loading / unloading positions located on the -Y direction side and -X direction side of the rotation center of the turntable 43. The grinding positions are positions for grinding the first surface W1 of the plate-shaped workpiece W by a grinding mechanism 90, which will be described later.

[0028] The grinding device 10 further includes an elevator device 80 provided on the column 29, and a grinding mechanism 90 that is moved up and down in the Z-axis direction by the elevator device 80.

[0029] The lifting device 80 includes a pair of guide rails 81 that are disposed on the front side of the column 29 and extend in the Z-axis direction, a lifting table 82 that is installed so as to be movable in the Z-axis direction relative to the pair of guide rails 81, and a ball screw 83 that extends in the Z-axis direction and screws into a screw-type portion (not shown) of the lifting table 82. The ball screw 83 is rotated by the driving force of a motor 84 that is connected to one end of the ball screw 83, thereby moving the lifting table 82 in the Z-axis direction.

[0030] The grinding mechanism 90 is attached to the front surface of the lift table 82 via a holder 91, and rotatably supports a spindle 93 with respect to a spindle housing 92 supported by the holder 91. The spindle 93 rotates around an axis in the Z-axis direction by the driving force of a spindle motor 94.

[0031] A mount 95 is connected to the lower end of the spindle 93, and a grinding wheel 96 is attached to the mount 95. A plurality of grinding stones 97 are provided in an annular shape on the underside of the grinding wheel 96. The grinding mechanism 90 grinds the first surface W1 of the plate-shaped workpiece W held by suction on each of the chuck tables 41, 42 with the grinding stones 97.

[0032] 3A and 3B are schematic cross-sectional views of the first chuck table and its periphery according to the first embodiment. 4A and 4B are schematic cross-sectional views of the second chuck table and its periphery according to the first embodiment. The first chuck table 41 and the second chuck table 42 have the same configuration except for the shapes of the holding surfaces 46 and 56.

[0033] The first chuck table 41 in Fig. 3 includes a first frame 44 and a disk-shaped first porous plate 45 attached in a recess on the upper surface of the first frame 44, with the upper surface of the first porous plate 45 forming a holding surface 46. The second chuck table 42 in Fig. 4 includes a second frame 54 and a disk-shaped second porous plate 55 attached in a recess on the upper surface of the second frame 54, with the upper surface of the second porous plate 55 forming a holding surface 56. Each of the porous plates 45, 55 is made of a porous material such as ceramics, and has fine pores formed throughout.

[0034] The holding device 40 further includes a first table rotation mechanism 47 and a second table rotation mechanism 57. Each of the table rotation mechanisms 47, 57 is configured with a motor, a pulley structure, etc. (not shown). The first table rotation mechanism 47 enables the first chuck table 41 to rotate around the central axis C1 of the holding surface 46, and the second table rotation mechanism 57 enables the second chuck table 42 to rotate around the central axis C2 of the holding surface 56.

[0035] The holding device 40 includes a suction source 60, a first suction path (suction path) 61 connected to the first porous plate 45 of the first chuck table 41 and communicating with the holding surface 46, and a second suction path (suction path) 62 connected to the second porous plate 55 of the second chuck table 42 and communicating with the holding surface 56. The suction source 60 is formed of a vacuum generating device such as a vacuum pump or an ejector, for example.

[0036] The first suction passage 61 is connected to a suction source 60 via a first on-off valve 63, and the second suction passage 62 is connected to the suction source 60 via a second on-off valve 64. When the first on-off valve 63 is opened, the suction source 60 and the holding surface 46 of the first chuck table 41 communicate with each other via the first suction passage 61, air is sucked from the holding surface 46, and negative pressure is applied, making it possible to suck and hold the plate-shaped workpiece W on the holding surface 46. When the second on-off valve 64 is opened, the suction source 60 and the holding surface 56 of the second chuck table 42 communicate with each other via the second suction passage 62, air is sucked from the holding surface 56, and negative pressure is applied, making it possible to suck and hold the plate-shaped workpiece W on the holding surface 56. The suction sources 60 communicating with the suction passages 61 and 62 may be common, or may be provided separately for each of the suction passages 61 and 62.

[0037] Next, the shapes of the holding surfaces 46, 56 will be described in the order of the holding surface 56 of the second chuck table 42 and the holding surface 46 of the first chuck table 41.

[0038] The holding surface 56 of the second chuck table 42 is a conical surface whose apex is located on the central axis C2 that is the rotation center of the second chuck table 42 and whose slope is gradually decreased toward the outer periphery, and whose slope is so slight that it is not discernible by visual inspection. The radial portion of the plate-shaped workpiece W held on such holding surface 56 becomes a grinding region that comes into contact with the annularly arranged grinding wheels 97, and the portion of the holding surface 56 directly below the grinding region is formed parallel to the lower surface 971 of the grinding wheel 97.

[0039] The holding surface 46 of the first chuck table 41 includes a central region 461 and an outer circumferential region 462 formed outside the central region 461. The central region 461 is a conical surface whose apex is located on the central axis C1, which is the rotation center of the first chuck table 41, and which gradually becomes lower toward the outer periphery, and is formed with approximately the same inclination as the holding surface 56 of the second chuck table 42. The outer circumferential region 462 is also a conical surface that gradually becomes lower toward the outer periphery, but the taper angles of the conical surface are different between the outer circumferential region 462 and the central region 461. More specifically, the outer circumferential region 462 is formed so that the taper angle is smaller than that of the central region 461.

[0040] As a result, the holding surface 46 of the first chuck table 41 has a shape in which the center is raised higher than the outer periphery, compared to the holding surface 56 of the second chuck table 42. Furthermore, the holding surface 46 of the first chuck table 41 is positioned such that the outer periphery region 462 is farther away from the lower surface 971 of the grinding wheel 97 than the central region 461 (see FIG. 3B), and the holding surface 46 is raised higher than the lower surface 971 of the grinding wheel 97.

[0041] The operation of each part of the grinding device 10 is controlled by a control unit 16 (see FIG. 2). A program for controlling the operation of, for example, the holding device 40, the grinding mechanism 90, etc. is stored in the memory of the control unit 16 as part of the control program. For example, the control unit 16 controls the opening and closing operation of each of the opening and closing valves 63, 64, and controls suction at each of the holding surfaces 46, 56. Regarding the operation of each part of the grinding device 10 described below, unless a control entity is specified, it is assumed that the operation is controlled by a control signal sent from the control unit 16.

[0042] The grinding method for a plate-shaped workpiece in this embodiment will be described below. The grinding method for a plate-shaped workpiece in this embodiment is carried out in the order of a first holding step, a reaction force reduction grinding step, a second holding step, and a finish grinding step. Figure 3A shows the first holding step, Figure 3B shows the reaction force reduction grinding step, Figure 4A shows the second holding step, and Figure 4B shows the finish grinding step.

[0043] [First holding step] In the first holding step, the plate-shaped workpiece W is transported and placed on the first chuck table 41 by the transport mechanism 30 (see FIG. 2). At this time, as shown in FIG. 3A, the warped plate-shaped workpiece W is oriented such that the first convex surface W1 faces upward and the second concave surface W2 faces downward. Then, the first opening / closing valve 63 is opened to connect the suction source 60 to the holding surface 46 of the first chuck table 41, and air is sucked from the holding surface 46, creating a negative pressure, whereby the plate-shaped workpiece W is suction-held on the holding surface 46.

[0044] The holding surface 46 of the first chuck table 41 has a shape that is raised in the center, and the second surface W2 of the plate-shaped workpiece W faces downward, so that when the plate-shaped workpiece W is placed on the holding surface 46, the second surface W2 of the plate-shaped workpiece W roughly conforms to the holding surface 46. Then, as a result of the application of negative pressure from the holding surface 46, the holding surface 46 and the second surface W2 of the plate-shaped workpiece W come into surface contact and are held by suction, while the shape of the plate-shaped workpiece W that is raised in the center is maintained.

[0045] [Reaction force reduction grinding process] After the first holding step, a reaction force reduction grinding step is carried out to reduce the reaction force when flattening the plate-shaped workpiece W. As shown in Fig. 3B, the reaction force reduction grinding step is carried out by grinding a first surface W1, which will be the top surface of the plate-shaped workpiece W, using a grinding mechanism 90.

[0046] In the reaction force reduction grinding process, the turntable 43 (see FIG. 2) is rotated to position the first chuck table 41 below the grinding wheel 96 in the grinding mechanism 90. In this positioning, the outer peripheral edges of the annularly arranged grinding stones 97 pass through the central axis C1 of the first chuck table 41.

[0047] In this state, the first chuck table 41 and the plate-shaped workpiece W held by suction are rotated by the first table rotation mechanism 47, and the grinding mechanism 90 is lowered by the lifting device 80 (see FIG. 2) while the grinding wheel 97 is rotated via the spindle 93. In this way, the grinding wheel 97 and the plate-shaped workpiece W held by suction on the first chuck table 41 are brought into contact with each other while rotating.

[0048] At this time, the holding surface 46 of the first chuck table 41 and the center of the plate-shaped workpiece W are raised, so the grinding region where the grinding wheel 97 comes into contact with the plate-shaped workpiece W is a partial region corresponding to directly above the central region 461. In other words, the region corresponding to directly above the outer peripheral region 462 of the holding surface 46 is not in contact with the lower surface 971 of the grinding wheel 97 because the taper angle is smaller. Therefore, in the reaction force reduction grinding process, the central portion W3 of the first surface W1, which is a portion of the plate-shaped workpiece W, is ground, and the region outside the central portion W3 is not ground. As a result, the central portion W3 of the plate-shaped workpiece W is made thinner than the outer regions, and the reaction force exerted against the force used to flatten the workpiece W is reduced.

[0049] [Second holding process] After the reaction force reduction grinding process, a second holding process is performed in which the chuck table holding the plate-shaped workpiece W is changed from the first chuck table 41 to the second chuck table 42. In the second holding process, the plate-shaped workpiece W on the first chuck table 41 is held by the transfer pad 31 (see FIG. 2) of the transfer mechanism 30, and then the turntable 43 is rotated 180° to place the plate-shaped workpiece W on the second chuck table 42. At this time, as shown in FIG. 4A, the orientation of the plate-shaped workpiece W is maintained such that the first surface W1 faces upward and the second surface W2 faces downward. Then, the second opening / closing valve 64 is opened to connect the suction source 60 to the holding surface 56 of the second chuck table 42, and air is sucked from the holding surface 56, creating a negative pressure, thereby suction-holding the plate-shaped workpiece W on the holding surface 56.

[0050] Since the holding surface 56 of the second chuck table 42 is parallel to the lower surface 971 of the grinding wheel 97, when a plate-shaped workpiece W is placed on the holding surface 56, the second surface W2 may become concave, creating a space between the holding surface 56. Even in this case, a force is applied in a direction that brings the second surface W2 closer to the holding surface 56 due to air suction at the holding surface 56, and the reaction force against this force is reduced by grinding the central portion W3, so that the holding surface 56 and the second surface W2 of the plate-shaped workpiece W are in surface contact and held by suction.

[0051] [Finishing grinding process] After the second holding step, a finish grinding step is carried out, as shown in Fig. 4B. The finish grinding step is carried out by the grinding mechanism 90 in the same manner as in the reaction force reduction grinding step, except that the chuck table that holds the plate-shaped workpiece W is changed from the first chuck table 41 to the second chuck table 42. In the finish grinding step, the plate-shaped workpiece W is finish-ground with a grinding wheel 97 until it has a predetermined uniform thickness.

[0052] More specifically, since the reaction force reduction grinding process has made the central portion W3 of the plate-shaped workpiece W thinner than the outer regions, in the finish grinding process, a greater amount of grinding is performed on the outer regions of the plate-shaped workpiece W than on the central portion W3. When grinding is performed until the lower surface 971 of the grinding wheel 97 contacts the entire radial area of ​​the plate-shaped workpiece W, the first surface W1 of the plate-shaped workpiece W is ground so as to be parallel to the lower surface 971 of the grinding wheel 97. At this time, the second surface W2 of the plate-shaped workpiece W is held by suction in surface contact with the holding surface 56 of the second chuck table 42, and is therefore parallel to the lower surface 971 of the grinding wheel 97. As a result, the first surface W1 and the second surface W2 of the plate-shaped workpiece W become parallel, and the plate-shaped workpiece W is formed to a uniform thickness.

[0053] According to the first embodiment, the plate-shaped workpiece W is suction-held with its center raised above its outer periphery, and then the central portion W3 of the plate-shaped workpiece W is ground in the reaction force reduction grinding process. This reduces the reaction force when flattening the plate-shaped workpiece W before suction-holding the plate-shaped workpiece W in the second holding process, allowing the second surface W2 of the plate-shaped workpiece W to be ground in the finish grinding process while being suction-held parallel to the lower surface 971 of the grinding wheel 97. This eliminates the need for a conventional process of applying tape to create a space between the plate-shaped workpiece W and the concave surface of the plate-shaped workpiece when grinding the plate-shaped workpiece W with a raised center. Therefore, the first embodiment improves workability when grinding a plate-shaped workpiece W that is warped so that its center is raised.

[0054] Next, other embodiments of the present invention will be described. In the following description, the same reference numerals may be used to designate components that are the same as or equivalent to those in the embodiments described before the embodiment, and the description thereof may be omitted or simplified.

[0055] [Second embodiment] A second embodiment of the present invention will be described with reference to Figures 5 and 6. Figures 5A, 5B, 6A, and 6B are schematic cross-sectional views of the chuck table and its periphery according to the second embodiment. Figure 5A shows the first holding step, Figure 5B shows the reaction force reduction grinding step, Figure 6A shows the second holding step, and Figure 6B shows the finish grinding step.

[0056] 5 and 6, in the second embodiment, the first chuck table 41 of the first embodiment is not used, and a chuck table 101 having the same configuration as the second chuck table 42 is used to grind a warped plate-shaped workpiece W. Therefore, in the following description, the same reference numerals will be used to designate the same components of the chuck table 101 as those of the second chuck table 42.

[0057] The holding device 40 in the second embodiment further includes a pressure adjustment unit 102 disposed in the second suction path 62 to adjust the negative pressure value on the holding surface 56 of the chuck table 101. The pressure adjustment unit 102 includes an air source 104, an air supply path 105 connected to the second suction path 62 between the second opening / closing valve 64 and the chuck table 101, and an adjustment valve 106 configured by a throttle valve or the like disposed in the air supply path 105. The pressure adjustment unit 102 is configured to be able to adjust the flow rate of air supplied from the air source 104 and the negative pressure value inside the second suction path 62 and on the holding surface 56 by opening the second opening / closing valve 64 to adjust the aperture of the adjustment valve 106.

[0058] The adjustment by the pressure adjusting unit 102 is controlled by the control unit 16 (see FIG. 2) based on the negative pressure value inside the second suction path 62 and on the holding surface 56 measured by the pressure gauge 107. For example, the control unit 16 stores a predetermined first range for forming a gap S (described later) and a predetermined second range that is higher in the negative pressure direction than the first range, and controls the operation of the adjusting valve 106 via the control unit 16 so that the negative pressure value measured by the pressure gauge falls within either range.

[0059] In the first holding step of the second embodiment, the second surface W2 of the plate-shaped workpiece W having a warped portion with a raised center is placed downward on the holding surface 56 of the chuck table 101. At this time, a gap S is formed between the holding surface 56, which is parallel to the lower surface 971 of the grinding wheel 97, and the second surface W2 of the plate-shaped workpiece W, which is concave.

[0060] With the gap S formed, by opening the second opening / closing valve 64, the suction source 60 and the holding surface 56 of the chuck table 101 are communicated with each other via the second suction path 62. At this time, the flow rate of air supplied from the air source 104 to the second suction path 62 is adjusted by the adjustment valve 106 of the pressure adjustment unit 102.

[0061] For this adjustment, the control unit 16 controls the operation of the regulating valve 106 so that the negative pressure value of the holding surface 56 measured via the pressure gauge 107 falls within the first range described above. As a result, air is sucked from the holding surface 56, reducing the pressure inside the gap S, and a force is applied to correct the warp of the plate-shaped workpiece W, but the plate-shaped workpiece W is suction-held on the holding surface 56 while maintaining the warp or keeping it slightly corrected. In other words, the first range is set to a pressure value (e.g., −50 to −40 MPa) at which the plate-shaped workpiece W warps to form the gap S and the plate-shaped workpiece W can be suction-held on the holding surface 56. Therefore, in the first holding step of the second embodiment, the center of the suction-held plate-shaped workpiece W is maintained in a raised state, as in the first embodiment.

[0062] In the second embodiment, after the first holding step, as shown in FIG. 5B, a reaction force reduction grinding step is performed in the same manner as in the first embodiment. In the reaction force reduction grinding step, the plate-shaped workpiece W is maintained in a warped state with a gap S formed therein, as in the first holding step. Then, as shown in FIG. 6A, the second holding step after the reaction force reduction grinding step is performed on the chuck table 101, as in the first holding step. In the second holding step, the operation of the adjusting valve 106 is controlled so that the negative pressure value of the holding surface 56 measured via the pressure gauge 107 falls within the second range described above. As a result, air is sucked from the holding surface 56 into the gap S, eliminating the gap S between the holding surface 56 and the second surface W2 of the plate-shaped workpiece W, resulting in surface contact and suction-holding by the holding surface 56. In other words, the second range is set to a pressure value (e.g., -90 to -80 MPa) that can correct the warp of the plate-shaped workpiece W after the reaction force reduction grinding process and can suction-hold the holding surface 56 and the second surface W2 of the plate-shaped workpiece W so that they are in surface contact.

[0063] 6B, in the second embodiment, as in the first embodiment, grinding can be performed in a state in which the second surface W2 is flat in the finish grinding process. This improves the workability when grinding a plate-shaped workpiece W that is warped so that the center is raised. Furthermore, the first holding process, the reaction force reduction grinding process, the second holding process, and the finish grinding process can be performed using a single chuck table 101.

[0064] [Third embodiment] A third embodiment of the present invention will be described with reference to Fig. 7 and Fig. 8. Fig. 7A, Fig. 7B, Fig. 8A, and Fig. 8B are schematic cross-sectional views of the universal chuck table and its periphery according to the third embodiment. Fig. 7A shows the first holding step, Fig. 7B shows the reaction force reduction grinding step, Fig. 8A shows the second holding step, and Fig. 8B shows the finish grinding step.

[0065] 7 and 8, in the third embodiment, a plate-shaped workpiece W is suction-held by a universal chuck table 110. The universal chuck table 110 includes a frame body 111 and a circular porous plate 112 attached to a recess of the frame body 111.

[0066] The universal chuck table 110 includes partitions 115 that radially divide the porous plate 112. The partitions 115 are made of an air-impermeable material and are arranged concentrically around the central axis C2 of the universal chuck table 110. The partitions 115 divide the porous plate 112 into a central region and an outer region surrounding the central region, like a Baumkuchen. This division allows the universal chuck table 110 to have two concentric holding surfaces. Specifically, the universal chuck table 110 includes a central holding surface 116 formed by the upper surface of the porous plate 112 inside the partitions 115, and an outer peripheral holding surface 117 formed by the upper surface of the porous plate 112 outside the partitions 115. Similar to the holding surface 56 of the first embodiment, each of the holding surfaces 116 and 117 is formed parallel to the lower surface 971 of the grinding wheel 97.

[0067] The holding device 40 of the third embodiment includes a suction source 60, a central suction path 121, a peripheral suction path 122, and an area change section 123. The central suction path 121 is connected to the suction source 60 and the porous plate 112 located inside the partition section 115, and connects the central holding surface 116 and the suction source 60. The peripheral suction path 122 is connected to the suction source 60 and the porous plate 112 located outside the partition section 115, and connects the peripheral holding surface 117 and the suction source 60.

[0068] The area changing unit 123 includes a central opening / closing valve 125 disposed in the central suction path 121 and a peripheral opening / closing valve 126 disposed in the peripheral suction path 122. When the central opening / closing valve 125 is opened, the suction source 60 and the central holding surface 116 communicate with each other via the central suction path 121, air is sucked from the central holding surface 116, negative pressure is applied, and the plate-shaped workpiece W can be sucked and held on the central holding surface 116. When the peripheral opening / closing valve 126 is opened, the suction source 60 and the peripheral holding surface 117 communicate with each other via the peripheral suction path 122, air is sucked from the peripheral holding surface 117, negative pressure is applied, and the plate-shaped workpiece W can be sucked and held on the peripheral holding surface 117.

[0069] The area changing unit 123 changes the area of ​​the holding surface of the entire universal chuck table 110 depending on whether only one of the central opening / closing valve 125 and the outer peripheral opening / closing valve 126 is opened or whether both the opening / closing valves 125 and 126 are opened. The change in the area of ​​the holding surface is performed by controlling the opening and closing of the opening / closing valves 125 and 126 using the control unit 16 (see FIG. 2).

[0070] In the first holding step of the third embodiment, similarly to the second embodiment, the second surface W2 of the plate-shaped workpiece W having a warped portion with a raised center is placed downward on each of the holding surfaces 116, 117 of the universal chuck table 110. At this time, a gap S is formed between each of the holding surfaces 116, 117, which are parallel to the lower surface 971 of the grinding wheel 97, and the second surface W2 of the plate-shaped workpiece W, which is concave.

[0071] With the gap S formed, the periphery opening / closing valve 126 is opened, so that the suction source 60 and the periphery holding surface 117 communicate with each other via the periphery suction path 122. As a result, the periphery portion W4 of the plate-shaped workpiece W that overlaps the periphery holding surface 117 in the vertical direction is suction-held by the periphery holding surface 117.

[0072] At this time, the central opening / closing valve 125 remains closed, and the negative pressure at the central holding surface 116 does not act on the central portion W3 of the plate-shaped workpiece W that overlaps vertically with the central holding surface 116, so that the plate-shaped workpiece W is not sucked. As a result, the outer peripheral portion W4 of the plate-shaped workpiece W is sucked and held on the outer peripheral holding surface 117 while maintaining or slightly correcting the warpage of the plate-shaped workpiece W. Therefore, in the first holding step of the third embodiment, as in the first and second embodiments, the center of the suction-held plate-shaped workpiece W is maintained in a raised state.

[0073] In the third embodiment, after the first holding step, a reaction force reduction grinding step is carried out in the same manner as in the first embodiment, as shown in Fig. 7B. In the reaction force reduction grinding step, the state in which the plate-shaped workpiece W is warped and the gap S is formed is maintained, as in the first holding step.

[0074] 8A, the second holding process after the reaction force reduction grinding process is performed on the universal chuck table 110, as in the first holding process. In the second holding process, both the central opening / closing valve 125 and the outer peripheral opening / closing valve 126 are controlled to be open, and the suction source 60 is connected to both the central holding surface 116 and the outer peripheral holding surface 117. As a result, air is sucked from the central holding surface 116 into the gap S, eliminating the gap S between both holding surfaces 116, 117 and the second surface W2 of the plate-shaped workpiece W, resulting in surface contact, and the plate-shaped workpiece W is suction-held by both holding surfaces 116, 117.

[0075] 8B, the third embodiment also makes it possible to perform grinding in a state in which the second surface W2 is flat in the finish grinding process, as in the first and second embodiments. This improves the workability when grinding a plate-shaped workpiece W that is warped so that the center is raised. Furthermore, the first holding process, the reaction force reduction grinding process, the second holding process, and the finish grinding process can be performed using a single universal chuck table 110.

[0076] [Fourth embodiment] A fourth embodiment of the present invention will be described with reference to Figures 9 and 10. Figures 9A, 9B, 10A, and 10B are schematic cross-sectional views of the chuck table and its periphery in the fourth embodiment. Figure 9A shows the first holding step, Figure 9B shows the reaction force reduction grinding step, Figure 10A shows the second holding step, and Figure 10B shows the finish grinding step.

[0077] 9 and 10, in a pressure adjustment unit 102 of the fourth embodiment, instead of the air source 104 of the second embodiment, a third on-off valve 131 is provided in an air supply path 105. In addition, in the fourth embodiment, one end of the air supply path 105 is open to the atmosphere, and opening and closing the third on-off valve 131 switches between suction of the atmosphere into the second suction path 62 and stopping suction.

[0078] The pressure adjusting unit 102 in the fourth embodiment adjusts the opening degree of the adjusting valve 106 by opening the second opening / closing valve 64 and the third opening / closing valve 131, thereby sucking the atmosphere from the air supply path 105 using the suction source 60 and adjusting the air flow rate in the second suction path 62. In this way, the negative pressure value inside the second suction path 62 and on the holding surface 56 is adjustable.

[0079] In the first holding step of the fourth embodiment, the second opening / closing valve 64 and the third opening / closing valve 131 are opened with the plate-shaped workpiece W placed on the holding surface 56 of the chuck table 101. This allows the suction source 60 to communicate with the holding surface 56 of the chuck table 101 via the second suction path 62, and at the same time, the flow rate of air flowing from the atmosphere through the air supply path 105 into the second suction path 62 is adjusted by the adjustment valve 106.

[0080] For this adjustment, the control unit 16 controls the operation of the adjusting valve 106 so that the negative pressure value of the holding surface 56 measured via the pressure gauge 107 falls within a first range (for example, −50 to −40 MPa). As a result, as shown in FIG. 9B, a gap S is formed between the warped plate-shaped workpiece W and the holding surface 56, and the plate-shaped workpiece W is suction-held by the holding surface 56, and the center of the suction-held plate-shaped workpiece W is maintained in a raised state, similar to the second embodiment.

[0081] In this state, the reaction force reduction grinding process is carried out after the first holding process, as in the second embodiment. Then, in the second holding process after the reaction force reduction grinding process, the third opening / closing valve 131 is closed, and then the operation of the adjusting valve 106 is controlled so that the negative pressure value of the holding surface 56 measured via the pressure gauge 107 falls within a second range (for example, −90 to −80 MPa). As a result, as shown in FIG. 10A, warping of the plate-shaped workpiece W after the reaction force reduction grinding process is corrected, and the plate-shaped workpiece W is held by suction so that the holding surface 56 and the second surface W2 of the plate-shaped workpiece W are in surface contact with each other.

[0082] 10B, in the fourth embodiment, grinding can be performed in a state in which the second surface W2 is flattened in the finish grinding process. This improves the workability when grinding a plate-shaped workpiece W that is warped so that the center is raised, as in the second embodiment, and makes it possible to perform the first holding process, the reaction force reduction grinding process, the second holding process, and the finish grinding process using a single chuck table 101.

[0083] The present invention is not limited to the above-described embodiments, and various modifications can be made to the embodiments. In the above-described embodiments, the size and shape shown in the accompanying drawings are not limited to these, and can be modified as appropriate within the scope of the effects of the present invention. In addition, the present invention can be modified as appropriate without departing from the scope of the object of the present invention.

[0084] In the above-described embodiments, the central portion W3 including the center of the plate-shaped workpiece W is ground into a circular shape in the reaction force reduction grinding process, but this is not limited to this. For example, the central portion of the central portion W3 may be left unground and ground into an annular shape concentric with the plate-shaped workpiece W, thereby reducing the reaction force exerted against the force used to flatten the plate-shaped workpiece W. When grinding the plate-shaped workpiece W into such an annular shape, the contact area between the grinding wheel 97 and the first surface W1 of the plate-shaped workpiece W is adjusted by adjusting the inclination of the central axes of the chuck tables 41, 101, 110 and the inclination of the central axis of the spindle 93.

[0085] Furthermore, the shape of the holding surface 46 of the first chuck table 41 in the first embodiment may be changed as long as the shape is raised in the center, and an example is forming it into a gently curved shape so that the center is raised higher than the outer periphery.

[0086] Furthermore, the shape of the plate-shaped workpiece W held and ground in each of the above embodiments is merely an example, and various modifications are possible, such as a circle, a rectangle, a polygon other than a rectangle, or a shape with curved sides.

[0087] Furthermore, although two chuck tables 41 and 42 are arranged on the turntable 43, three or more chuck tables may be arranged on the turntable 43.

[0088] Furthermore, in the second and fourth embodiments, the opening degree of the regulating valve 106 is adjusted by the control unit 16, but the opening degree of the regulating valve 106 may be adjusted by an operator.

[0089] In the second and fourth embodiments, the adjustment valve 106 may be changed to a fixed throttle valve having a fixed opening and a predetermined orifice diameter. When the adjustment valve 106 is changed to a fixed throttle valve in the second and fourth embodiments, an opening / closing valve is further provided in the air supply path 105, and the negative pressure value applied to the holding surface 56 is adjusted by the opening / closing valve.

[0090] Furthermore, the first chuck table 41 in the first embodiment may be modified to the configuration shown in Fig. 11. Figs. 11A and 11B are schematic cross-sectional views of the first chuck table and its periphery in this modified example. Fig. 11A shows the first holding step, and Fig. 11B shows the reaction force reduction grinding step.

[0091] 11A and 11B, the holding surface 46 of the first chuck table 41 in the first embodiment is formed in the same shape as the holding surface 56 of the second chuck table 42, and a pressure adjustment unit 132 is provided. The pressure adjustment unit 132 includes an air supply path 133 provided in the first frame 44 of the first chuck table 41, and an adjustment valve 134 provided in the air supply path 133. Although the modification in FIG. 11 is configured such that an open / close valve is not provided in the air supply path 133, such an open / close valve may be provided.

[0092] One end of the air supply path 133 is connected to the first porous plate 45 to communicate with the holding surface 46, and the other end is open to the atmosphere. The adjustment valve 134 functions in the same manner as the adjustment valve 106 of the fourth embodiment. Therefore, in the pressure adjustment unit 132 of the modified example, by opening the first opening / closing valve 63 to adjust the aperture of the adjustment valve 134, the air sucked from the atmosphere via the suction source 60 through the air supply path 133 is adjusted, and the negative pressure value inside the first suction path 61 and on the holding surface 46 is adjustable.

[0093] 11, in the first holding step using the first chuck table 41, the first opening / closing valve 63 is opened with the plate-shaped workpiece W placed on the holding surface 46. This allows the suction source 60 and the holding surface 46 to communicate with each other via the first suction path 61, and at the same time, the flow rate of air flowing from the atmosphere to the holding surface 46 via the air supply path 133 and the first porous plate 45 is adjusted by the adjustment valve 134.

[0094] For this adjustment, the control unit 16 controls the operation of the adjusting valve 134 so that the negative pressure value of the holding surface 46 measured via the pressure gauge 107 falls within a first range (e.g., −50 to −40 MPa). As a result, a gap S is formed between the warped plate-shaped workpiece W and the holding surface 46, and the plate-shaped workpiece W is suction-held by the holding surface 46, and the center of the suction-held plate-shaped workpiece W is maintained in a raised state, as in the second and fourth embodiments (see FIG. 11B). In this state, a reaction force reduction grinding process is performed, as in the second and fourth embodiments, and then a second holding process and a finish grinding process are performed, as in the first embodiment.

[0095] 11 may be used in the first holding step and the reaction force reduction grinding step, and the chuck table 101 may be used in the second holding step and the finish grinding step as described above. In this case, the pressure adjustment unit 102 of the second and fourth embodiments may be omitted, and further, a configuration may be adopted in which the adjustment valve 134 is replaced with a fixed throttle valve. In such a configuration, when the plate-shaped workpiece W is held on the holding surface 46 of the first chuck table 41, the negative pressure applied to the holding surface 46 is weakened by the opening of the fixed throttle valve. Therefore, the plate-shaped workpiece W warps between the holding surface 46 and the plate-shaped workpiece W, forming a gap S, and the pressure is set to a value that allows the plate-shaped workpiece W to be suction-held on the holding surface 46. [Industrial Applicability]

[0096] As described above, the present invention has the effect of preventing machining chips from adhering to the exposed holding surface and becoming trapped between the plate-shaped workpiece and the holding surface when selectively holding and processing plate-shaped workpieces of different shapes. [Explanation of symbols]

[0097] 10: Grinding equipment 41: First chuck table (chuck table) 42: Second chuck table (chuck table) 46: Holding surface 56: Holding surface 60: Suction source 61: 1st suction path (suction path) 62:Second suction path (suction path) 90: Grinding mechanism 97: Grinding wheel 971: Bottom surface 101: Chuck table 102: Pressure adjustment unit 110: Universal chuck table (chuck table) 116: Central holding surface (holding surface) 117: Outer retaining surface (retaining surface) 121: Central suction tract 122: Peripheral suction path 123: Area change section 132: Pressure adjustment unit S: Gap W: Plate-shaped workpiece W3: Central part

Claims

1. A method for grinding a plate-shaped workpiece having a raised center using a grinding wheel, comprising: a first holding step of suction-holding the plate-shaped workpiece with a holding surface of a first chuck table, the center of which is raised higher than the outer periphery; a reaction force reduction grinding step in which a central portion of the plate-shaped workpiece is ground with the grinding wheel to reduce a reaction force when the plate-shaped workpiece is flattened; a second holding step of suction-holding the plate-shaped workpiece on a holding surface of a second chuck table that is parallel to the lower surface of the grinding wheel; a finish grinding step of finish-grinding the plate-shaped workpiece with the grinding wheel.

2. A grinding device that enables the grinding method for a plate-shaped workpiece according to claim 1, the first chuck table having a holding surface raised relative to the lower surface of the grinding wheel; the second chuck table having a holding surface parallel to a lower surface of the grinding wheel; a grinding mechanism that grinds the plate-shaped workpiece held by suction on the first chuck table and the second chuck table.

3. A method for grinding a plate-shaped workpiece having a raised center using a grinding wheel, comprising: a first holding step of suction-holding the plate-shaped workpiece with the center of the plate-shaped workpiece raised by a holding surface of a chuck table that is parallel to the lower surface of the grinding wheel; a reaction force reduction grinding step in which a central portion of the plate-shaped workpiece is ground with the grinding wheel to reduce a reaction force when the plate-shaped workpiece is flattened; a second holding step of suction-holding the plate-shaped workpiece on the holding surface of the chuck table without any gap between the holding surface and the underside of the plate-shaped workpiece; a finish grinding step of finish-grinding the plate-shaped workpiece with the grinding wheel.

4. A grinding apparatus that enables the grinding method for a plate-shaped workpiece according to claim 3, the chuck table having the holding surface; a suction path that communicates the holding surface with a suction source; a pressure adjusting unit disposed in the suction path and adjusting the negative pressure value of the holding surface; a grinding mechanism that grinds the plate-shaped workpiece held by suction on the chuck table.

5. A grinding apparatus that enables the grinding method for a plate-shaped workpiece according to claim 3, a chuck table having at least two holding surfaces, i.e., a central holding surface and an outer peripheral holding surface, which are concentric; a central suction passage communicating the central holding surface with a suction source; an outer periphery suction path communicating the outer periphery holding surface with the suction source; an area changing unit that changes the area of ​​the holding surface; and a grinding mechanism that grinds the plate-shaped workpiece held by suction on the chuck table.

Images