JP7704557B2 - Method for grinding curved plate-shaped workpiece - Google Patents

Description

The present invention relates to a method for grinding a curved plate-shaped workpiece using a grinding wheel.

For example, as disclosed in the following Patent Document 1, when a plate-shaped workpiece, whose outer periphery is held by suction on the holding surface of a chuck table and whose outer periphery has a force that causes it to warp, is ground with a grinding wheel, the frictional force caused by contact between the grinding wheel and the plate-shaped workpiece and the force that causes the plate-shaped workpiece to warp can cause the outer periphery of the plate-shaped workpiece to lift off the holding surface, causing the plate-shaped workpiece to separate from the holding surface.

And to prevent the curved plate-shaped workpiece from separating from the holding surface, a cutting groove is formed on the top surface of the plate-shaped workpiece, which is the surface to be ground, before grinding, correcting the curvature of the plate-shaped workpiece and reducing the force that causes it to warp upward.

JP 2015-223667 A

Conventionally, cutting wheels are used to make grooves in the plate-shaped workpiece. For this reason, the processing device is equipped with a cutting mechanism equipped with a cutting wheel that forms grooves in the plate-shaped workpiece, and a grinding mechanism equipped with a grinding wheel that grinds the plate-shaped workpiece to make it thinner. The worker may frequently replace the cutting wheel and the grinding wheel, which requires replacing two types of wheels and keeping two types of wheels in stock.

Therefore, when grinding a plate-shaped workpiece that has a curve that causes it to bend upward by reducing the force that causes the workpiece to separate from the holding surface of the chuck table of the grinding device due to the curve, there is a problem of reducing the frequency of the grinding wheel replacement work and eliminating the need to keep multiple types of grinding wheels in stock.

In order to solve the above-mentioned problems, the present invention provides a method for grinding a plate-shaped workpiece, using a grinding device including a chuck table having a holding surface, a horizontal movement unit for horizontally moving the chuck table in a direction parallel to the holding surface, a grinding unit having a plurality of grinding wheels arranged in a ring, and a lifting unit for lifting and lowering the grinding unit in a direction perpendicular to the holding surface, in which the upper surface of the plate-shaped workpiece having a force in a direction away from the holding surface of the chuck table is ground with an annular grinding wheel, the method comprising : pressing the entire lower surface of the plate-shaped workpiece against the holding surface, holding the plate-shaped workpiece with the holding surface in a state where the curvature is temporarily eliminated , and lifting and lowering the grinding wheel positioned above the plate-shaped workpiece held on the holding surface in a direction perpendicular to the holding surface. and cutting the grinding wheel into the upper surface of the plate-shaped workpiece without rotating the holding surface to form an arc-shaped groove; a table moving step in which the horizontal movement unit moves the chuck table in a direction parallel to the holding surface to position the grinding wheel at a position different from the position of the grinding wheel positioned with respect to the plate-shaped workpiece in the arc-groove forming step; a multiple groove forming step in which the arc-groove forming step and the table moving step are repeated to form a multiple number of grooves in the upper surface of the plate-shaped workpiece to correct curvature of the plate-shaped workpiece; and a grinding step in which, after forming a multiple number of grooves, the grinding wheel grinds the upper surface of the plate-shaped workpiece to remove the grooves and grind the plate-shaped workpiece to a predetermined thickness.

In the grinding method for a plate-shaped workpiece according to the present invention, the grinding process preferably comprises rotating the chuck table around the center of the holding surface as an axis, lowering the grinding wheel, which passes through the center of rotation of the plate-shaped workpiece held on the rotating holding surface, in a direction perpendicular to the holding surface by the lifting unit, so as to bring the lower surface of the grinding wheel into contact with the plate-shaped workpiece , thereby grinding the plate-shaped workpiece.

In the grinding method for a plate-shaped workpiece according to the present invention, the grinding process preferably involves positioning the lower surface of the grinding wheel outside the outer periphery of the plate-shaped workpiece held on the holding surface and below the upper surface of the plate-shaped workpiece, and moving the chuck table horizontally using the horizontal movement unit to grind the plate-shaped workpiece.

In the method for grinding a plate-shaped workpiece according to the present invention, the arc groove forming process preferably involves tilting the chuck table so that the front side in the direction of travel is lower than the rear side, and cutting into the upper surface of the plate-shaped workpiece held by the holding surface from the outer corner of the lower surface of the grinding wheel.

In the method for grinding a plate-shaped workpiece according to the present invention, the arc groove forming process preferably involves tilting the chuck table so that the front side in the direction of travel is higher than the rear side, and cutting into the upper surface of the plate-shaped workpiece held by the holding surface from the inner corner of the lower surface of the grinding wheel.

The method for grinding a plate-shaped workpiece according to the present invention, in which the upper surface of a curved plate-shaped workpiece, the outer periphery of which is held by the holding surface of the chuck table and has a force in a direction away from the holding surface, is ground with an annular grinding wheel. The grinding wheel is lowered in a direction perpendicular to the holding surface above the plate-shaped workpiece held by the holding surface, and the grinding wheel is cut into the upper surface of the plate-shaped workpiece without rotating the holding surface to form an arc groove. The grinding wheel is then slightly removed from the chuck table in order to position the grinding wheel at a position different from the position of the grinding wheel positioned relative to the plate-shaped workpiece in the arc groove forming step. By providing a grinding wheel moving process in which at least one of the grinding wheels is moved relatively in a direction parallel to the holding surface, a circular groove forming process, and a multiple groove forming process in which the grinding wheel moving process is repeated to form multiple grooves on the upper surface of the plate-shaped workpiece to correct the curvature of the plate-shaped workpiece, the force that causes the plate-shaped workpiece to separate from the holding surface is reduced before the plate-shaped workpiece is ground to thin it, so that after forming the multiple grooves, the upper surface of the plate-shaped workpiece is ground to remove the grooves, and the plate-shaped workpiece can be ground to a predetermined thickness while preventing the plate-shaped workpiece from separating from the holding surface and preventing the occurrence of vacuum leaks. In addition, since groove processing and grinding processing are performed using only the grinding wheel, the number of types of grinding wheels can be reduced, and it is no longer necessary to keep multiple types of grinding wheels in stock in the grinding device.

In the grinding process, the chuck table is rotated around the center of the holding surface, and a grinding wheel passing through the center of rotation of the plate-shaped workpiece held on the rotating holding surface is lowered in a direction perpendicular to the holding surface to grind the plate-shaped workpiece; in other words, by performing in-feed grinding, it is possible to remove grooves, flatten the top surface of the plate-shaped workpiece, and thin the plate-shaped workpiece to a specified thickness.

The grinding process involves positioning the bottom surface of the grinding wheel outside the outer periphery of the plate-shaped workpiece held on the holding surface and below the top surface of the plate-shaped workpiece, and then bringing the plate-shaped workpiece and the grinding wheel relatively close together in a direction parallel to the holding surface to grind the plate-shaped workpiece; in other words, creep feed grinding is performed, which removes grooves, flattens the top surface of the plate-shaped workpiece, and appropriately thins the plate-shaped workpiece to a specified thickness.

The arc groove forming process involves changing the inclination of the holding surface of the chuck table relative to the underside of the grinding wheel, and cutting the holding surface from the outer corner of the underside of the grinding wheel into the top surface of the plate-shaped workpiece being held, making it possible to properly form a groove that corrects the curvature of the plate-shaped workpiece.

The arc groove forming process changes the inclination of the holding surface of the chuck table relative to the underside of the grinding wheel, and cuts into the upper surface of the plate-shaped workpiece held by the holding surface from the inner circumferential angle of the underside of the grinding wheel, making it possible to properly form a groove that corrects the curvature of the plate-shaped workpiece. Also, in the grinding process carried out after the multiple groove forming process in which the arc groove forming process and the grinding wheel moving process are repeated, for example when creep feed grinding is performed, it becomes possible to prevent the outer surface of the grinding wheel, which is the area that mainly grinds the plate-shaped workpiece in creep feed grinding, from being worn down due to creep feed grinding.

FIG. 2 is a perspective view showing an example of a grinding device used in the grinding method. FIG. 11 is a cross-sectional view illustrating the curvature of a plate. FIG. 2 is a side view showing an example of a grinding device. 1 is a plan view illustrating an arc groove formed on the top surface of a plate-shaped workpiece by performing the arc groove forming process and grinding wheel moving process of embodiment 1, the arc groove running across from one outer periphery side of the plate-shaped workpiece to the other outer periphery side. FIG. This is a plan view illustrating a state in which a multiple groove forming process is carried out in which an arc groove is formed across the entire top surface of a plate-shaped workpiece by repeating an arc groove forming process and a grinding wheel moving process in embodiment 1, and the arc groove crosses from one outer periphery side to the other outer periphery side. This is an oblique view illustrating the state in which a multiple groove forming process in which an arc groove forming process and a grinding wheel moving process are repeated in embodiment 1, and an arc groove that crosses the plate-shaped workpiece from end to end is formed on the entire top surface. FIG. 11 is a side view showing a part of a grinding device in a state where the inclination of the holding surface of the chuck table with respect to the underside of the grinding wheel is changed relatively to cut into the upper surface of the held plate-shaped workpiece from the outer corner of the underside of the grinding wheel when performing the arc groove forming process of embodiment 2. FIG. 11 is a plan view illustrating the state in which arc grooves are formed in both ±X direction regions of the top surface of a plate-shaped workpiece by performing the arc groove forming process of embodiment 2 and the multiple groove forming process of repeating the grinding wheel moving process. 13 is a plan view illustrating a state in which arc grooves are formed over substantially the entire upper surface of a plate-shaped workpiece by performing the arc groove forming process of embodiment 2 and a multiple groove forming process in which the grinding wheel moving process is repeated. FIG. This is a plan view illustrating the state in which many arc grooves are formed on the top surface of a plate-shaped workpiece, particularly in the four corner regions, by performing the arc groove forming process of embodiment 3 and the multiple groove forming process of repeating the grinding wheel moving process. FIG. 13 is a side view showing a part of a grinding device in a state where the inclination of the holding surface of the chuck table with respect to the underside of the grinding wheel is changed relatively to the inner angle of the underside of the grinding wheel when performing the arc groove forming process of embodiment 4, so that the holding surface is set to cut into the upper surface of the held plate-shaped workpiece from the inner angle of the underside of the grinding wheel. FIG. 11 is a plan view illustrating a state in which many arc grooves are formed in both ±X direction regions of the top surface of a plate-shaped workpiece by performing the arc groove forming process of embodiment 4 and the multiple groove forming process of repeating the grinding wheel moving process. This is a plan view illustrating a state in which many arc grooves are formed in both ±X direction regions of the top surface of the plate-shaped workpiece by performing the arc groove forming process of embodiment 4 and the multiple groove forming process of repeating the grinding wheel moving process when the inner diameter of the grinding wheel is smaller than the length of the plate-shaped workpiece.

The grinding device 1 shown in Figure 1 is a device that grinds a plate-shaped workpiece 90 held by suction on a chuck table 3 using a grinding unit 16, and the front (-Y direction side) of an equipment base 10, whose longitudinal direction is the Y axis direction of the grinding device 1, is an attachment/detachment area where the plate-shaped workpiece 90 is attached to and detached from the chuck table 3, and the rear (+Y direction side) of the equipment base 10 is a grinding area where the grinding unit 16 grinds the plate-shaped workpiece 90 held by suction on the chuck table 3.
In addition, the grinding device used to carry out the grinding method of the present invention is not limited to a single-axis type grinding unit 16 like the grinding device 1, but may be a two-axis type that has a rough grinding unit and a finish grinding unit and can position the plate-shaped workpiece 90 below the rough grinding unit or the finish grinding unit on a rotating turntable.

In the plate-shaped workpiece 90 shown in Fig. 1, silicon chips are arranged at equal intervals on the upper surface of a rectangular substrate made of, for example, a PCB, and the upper surface of the substrate including the silicon chips is molded with epoxy resin or the like. The plate-shaped workpiece 90, which is rectangular in plan view, is curved as a whole due to the contraction force of the molded resin. That is, as shown in Fig. 2, the curvature of the plate-shaped workpiece 90 is, for example, a warp that gradually becomes higher from the central region of the lower surface 902 of the plate-shaped workpiece 90, which is held by suction, toward the outer peripheral region. The upper surface 904 of the plate-shaped workpiece 90 becomes the grinding surface to be ground, and a protective tape 9000 for protecting the lower surface 902 is attached to the lower surface 902 of the plate-shaped workpiece 90.
In this embodiment, the plate-shaped workpiece 90 is polygonal (rectangular), but is not limited to this, and may be a silicon wafer or the like that is circular in plan view.

The chuck table 3 shown in Figures 1 and 3 includes, for example, a porous portion 30 having a rectangular holding surface 302, and a frame body 31 that supports the porous portion 30. The holding surface 302 is connected to a suction source (not shown), such as a vacuum generator or an ejector mechanism.

As shown in FIG. 1, the chuck table 3 is surrounded by a cover 39 and can be rotated around the Z-axis by a table rotation mechanism 33, which is made up of a rotating shaft connected to the underside of the cover, a motor, an encoder that detects the rotation angle of the motor, etc.

As shown in FIG. 1, a horizontal movement unit 13 is disposed inside the device base 10 to move the chuck table 3 horizontally between a grinding position where the grinding wheel 164 grinds the plate-shaped workpiece 90 and a loading/unloading position where the plate-shaped workpiece 90 can be loaded onto or unloaded from the holding surface 302 of the chuck table 3.
The horizontal movement unit 13 includes a ball screw 130 having an axis in the Y-axis direction, a pair of guide rails 131 arranged parallel to the ball screw 130, a motor 132 connected to one end of the ball screw 130 and rotating the ball screw 130, and a movable plate 133 having an internal nut that screws onto the ball screw 130 and a bottom that slides against the guide rail 131. When the motor 132 rotates the ball screw 130, the movable plate 133 is guided by the guide rail 131 and moves linearly in the Y-axis direction, and as shown in FIGS. 1 and 3, the chuck table 3, which is arranged on the movable plate 133 via the inclination adjustment unit 37, the table rotation mechanism 33, and the chuck base 35 (not shown in FIG. 3), can be moved in the Y-axis direction.
The horizontal movement unit 13 may be a rotatable turntable having a plurality of chuck tables 3 arranged on its upper surface.

As shown in FIG. 1, the chuck table 3 is attached to the upper surface of a chuck base 35 , and the chuck base 35 is supported by an inclination adjustment portion 37 that adjusts the inclination of a holding surface 302 of the chuck table 3 .
As shown in Fig. 3, on the movable plate 133 of the horizontal movement unit 13, for example, two or more tilt adjustment units 37 are provided at equal intervals on a circumference centered on the center of the holding surface 302 of the chuck table 3 on the lower surface side of the chuck base 35. That is, for example, two tilt adjustment units 37 and a support column extending in the Z-axis direction (not shown) for fixing the chuck base 35 are arranged circumferentially at intervals of 120 degrees. The two tilt adjustment units 37 are, for example, electric cylinders or air cylinders in which piston rods 371 can move up and down in the Z-axis direction. By moving the piston rods 371 of the two tilt adjustment units 37 shown in Fig. 3 up and down, the tilt of the holding surface 302 with respect to the lower surface of the grinding wheel 1642 of the grinding unit 16 can be adjusted.
The inclination adjustment section may be provided on the grinding unit 16 side.

As shown in FIG. 1, a column 11 is erected in the grinding area, and a lifting unit 17 is disposed on the front surface of the column 11 on the -Y direction side, which moves the grinding unit 16 vertically, that is, in the Z-axis direction perpendicular to the holding surface 302 of the chuck table 3. The lifting unit 17 includes a ball screw 170 extending in the Z-axis direction, a pair of guide rails 171 disposed parallel to the ball screw 170, a lifting motor 172 connected to the upper end of the ball screw 170 and rotating the ball screw 170, and a lifting plate 173 whose internal nut is screwed into the ball screw 170 and whose side is in sliding contact with the guide rail 171. When the lifting motor 172 rotates the ball screw 170, the lifting plate 173 is guided by the guide rail 171 and moves back and forth in the Z-axis direction, and the grinding unit 16 fixed to the lifting plate 173 is ground and fed in the Z-axis direction.

The grinding unit 16, which grinds the plate-shaped workpiece 90 held on the chuck table 3, includes a rotating shaft 160 whose axial direction is the Z-axis direction, a housing 161 that rotatably supports the rotating shaft 160, a motor 162 that rotates and drives the rotating shaft 160, an annular mount 163 connected to the lower end of the rotating shaft 160, a grinding wheel 164 that is detachably attached to the lower surface of the mount 163, and a holder 165 that supports the housing 161 and is fixed to the lifting plate 173 of the lifting unit 17.

The grinding wheel 164 comprises a wheel base 1641 and a number of grinding stones 1642 of approximately rectangular parallelepiped shape arranged in a ring shape on the bottom surface of the wheel base 1641. The grinding stones 1642 are formed by, for example, fixing diamond abrasive grains with a resin bond, a vitrified bond, or the like. The blade width of the annular grinding stone 1642 is set to, for example, 1 mm to 3 mm.

For example, the diameter of the grinding wheel 164 is larger than that of the plate-shaped workpiece 90 so that the arc-shaped grinding stone 1642 can traverse from one side of the plate-shaped workpiece 90 to the opposite side with sufficient margin.
In addition, in the case where the arc groove forming process of the grinding direction according to the present invention in the embodiment 4 described later is not performed, the diameter of the grinding wheel 164 may be smaller than the size of the plate-shaped workpiece 90.

Inside the rotating shaft 160, a flow passage (not shown) that is connected to a grinding water supply source and serves as a passage for grinding water is provided, penetrating the axial direction of the rotating shaft 160. The flow passage (not shown) further passes through the mount 163 and opens at the bottom surface of the wheel base 1641 so that the grinding water can be sprayed toward the grinding wheel 1642.

In this embodiment, the grinding unit 16 and the lifting unit 17 can be moved back and forth in the X-axis direction by an X-axis moving unit 18 disposed on the front surface of the column 11, for example.
The X-axis moving unit 18 includes a ball screw 180 whose axial direction is in the X-axis direction, a pair of guide rails 181 arranged parallel to the ball screw 180, a motor 182 connected to one end of the ball screw 180 and rotating the ball screw 180, and a movable plate 183 whose internal nut screws into the ball screw 180 and whose side is in sliding contact with the guide rail 181. When the motor 182 rotates the ball screw 180, the movable plate 183 is guided by the guide rail 181 and moves back and forth in the X-axis direction, and the grinding unit 16 and the lifting unit 17 arranged on the movable plate 183 move back and forth in the X-axis direction.

1, a thickness measuring unit 104 that contact-type measures the thickness of the plate-shaped workpiece 90 is disposed adjacent to the grinding unit 16 when it has been lowered to the grinding position. The thickness measuring unit 104 measures the height position of the holding surface 302 serving as a reference surface, that is, in this embodiment, the height position of the upper surface of the frame 31 that is at the same height position as the holding surface 302, with a first linear gauge, and measures the height position of the upper surface 904 of the plate-shaped workpiece 90 to be ground with a second linear gauge, and calculates the difference between the measured values of both linear gauges, thereby making it possible to sequentially measure the thickness of the plate-shaped workpiece 90 during grinding.
The thickness measuring unit 104 may be of a non-contact type.

For example, in the attachment/detachment area on the device base 10 shown in FIG. 1, a pressing mechanism 4 is disposed at a position beside the movement path of the chuck table 3, which presses the plate-shaped workpiece 90 placed on the holding surface 302 of the chuck table 3 from above downward for suction holding.

The pressing mechanism 4 includes a lifting mechanism 40 such as an electric cylinder or air cylinder arranged on the device base 10, an arm portion 41 whose rear end is attached to the upper end side of a lifting rod (not shown) that moves up and down in the Z-axis direction of the lifting mechanism 40 and extends horizontally up to above the movement path of the chuck table 3, and a pressing pad 44 attached to the underside of the tip of the arm portion 41. The arm portion 41 can, for example, rotate about a rotation axis in the Z-axis direction in a horizontal plane (within the X-axis and Y-axis plane).

The pressing pad 44, which can be raised and lowered in the Z-axis direction by the lifting mechanism 40 and can be directly opposed to the center of the holding surface 302 of the chuck table 3 in the Z-axis direction, is formed, for example, in a rectangular shape that is the same size as the plate-shaped workpiece 90 in a plan view or slightly larger than the plate-shaped workpiece 90. The flat lower surface 443 of the pressing pad 44 comes into contact with the upper surface 904 of the plate-shaped workpiece 90.

Below, we will explain each process and the operation of each component of the grinding device 1 when carrying out the grinding method of the present invention and grinding a plate-shaped workpiece 90 held on the chuck table 3 by the grinding device 1 shown in Figure 1.
1 and 3 is moved in the -Y direction by the horizontal movement unit 13 to be positioned, for example, directly below the pressing pad 44 of the pressing mechanism 4 in the attachment/detachment area. In addition, the pressing pad 44 disposed at the tip of the arm portion 41 is rotated about the rotation shaft 45 passing through the center of the lifting mechanism 40, so that the shape of the pressing pad 44 and the shape of the holding surface 302 of the chuck table 3 approximately match.

Next, as shown in FIG. 3, for example, an operator places the plate-shaped workpiece 90 on the holding surface 302 of the chuck table 3 with their centers approximately aligned and with the shape of the holding surface 302 approximately aligned with the shape of the plate-shaped workpiece 90. Here, the plate-shaped workpiece 90 is placed on the holding surface 302 so that it gradually becomes higher from the central region of the lower surface 902 toward the outer peripheral region.

The suction force generated by the operation of a suction source (not shown) is transmitted to the holding surface 302, causing the chuck table 3 to first suction-hold the central region of the underside 902 of the plate-shaped workpiece 90 (in this embodiment, the central region of the underside of the protective tape 9000) on the holding surface 302.

Furthermore, the pressing pad 44 is lowered at a predetermined speed by the lifting mechanism 40 shown in FIG. 1. The pressing pad 44 presses the plate-shaped workpiece 90 so that the outer peripheral area of the lower surface 902 of the plate-shaped workpiece 90 corrects the curvature against the holding surface 302. Then, the plate-shaped workpiece 90 is sucked and held by the chuck table 3 without any vacuum leak, with the warping of the outer peripheral portion, i.e., the entire curvature, temporarily eliminated. Note that if the grinding wheel 1642 is kept in contact with the upper surface 904 of the plate-shaped workpiece 90 without forming a groove on the upper surface 904 of the plate-shaped workpiece 90, and the plate-shaped workpiece 90 rotated by the chuck table 3 is ground, for example, without forming a groove on the upper surface 904 of the plate-shaped workpiece 90, the curvature of the plate-shaped workpiece 90 may be restored during grinding due to the frictional force acting between the grinding wheel 1642 and the upper surface 904 of the plate-shaped workpiece 90, which may cause a vacuum leak or the like.

After the plate-shaped workpiece 90 is sucked and held on the chuck table 3 in a state where the curvature is temporarily eliminated, the pressing pad 44 rises and moves away from the plate-shaped workpiece 90.
Next, the horizontal movement unit 13 moves the chuck table 3 holding the plate-shaped workpiece 90 to below the grinding unit 16 shown in FIGS. 1 and 3, and the grinding wheel 164 and the plate-shaped workpiece 90 are aligned.

(1-1) Circular-arc groove forming process embodiment 1
The following describes the arc groove forming process of embodiment 1, in which the grinding wheel 1642 positioned above the plate-shaped workpiece 90 held by suction on the holding surface 302 of the chuck table 3 shown in Figure 3 is lowered in a direction perpendicular to the holding surface 302 (Z-axis direction), and the grinding wheel 1642 is cut into the upper surface 904 of the plate-shaped workpiece 90 without rotating the holding surface 302 to form an arc groove.

For example, in this embodiment 1, the inclination of the chuck base 35 and the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIG. 3, so that the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302 becomes approximately parallel to the lower surface of the grinding wheel 1642.

Then, the grinding unit 16 is moved in the X-axis direction by the X-axis moving unit 18 shown in Figures 1 and 3, and the grinding unit 16 and the chuck table 3 are aligned in the X-axis direction so that the center of the holding surface 302 of the chuck table 3 (i.e., the center of the plate-shaped workpiece 90) is positioned on a line extending in the imaginary Y-axis direction that passes through the center of the grinding wheel 164.

Then, the motor 132 of the horizontal movement unit 13 rotates the ball screw 130 by a predetermined angle and then stops for a certain period of time, repeating this operation, so that the chuck table 3 moves a predetermined distance in the Y-axis direction, stops, and then performs a step movement in which it moves again a predetermined distance in the Y-axis direction after a predetermined time has elapsed.

The +Y direction end area of the upper surface 904 of the plate-shaped workpiece 90, which is suction-held on the chuck table 3 which moves stepwise in the +Y direction by the horizontal movement unit 13, is positioned below the grinding wheel 1642, and the movement of the chuck table 3 stops for a moment.
Next, when the grinding unit 16 is lowered in the −Z direction at a predetermined grinding feed speed by the lifting unit 17 , the grinding wheel 1642 rotating at a predetermined rotational speed comes into contact with the upper surface 904 of the plate-shaped workpiece 90 .

At this time, in this embodiment, the grinding wheel 1642 cuts from the lower surface (flat surface) into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302. Then, by not rotating the holding surface 302 of the chuck table 3, a single arc-shaped groove 907 as shown in FIG. 4 is formed in the upper surface 904 of the plate-shaped workpiece 90. For example, the width of the arc-shaped groove 907 is approximately the same as the blade width of the grinding wheel 1642.

The grinding wheel 1642 shown in FIG. 3 cuts into the upper surface 904 to a position that is a predetermined height above the finishing thickness of the plate-shaped workpiece 90 to form an arc-shaped groove 907 of a predetermined depth as shown in FIG. 4. After that, the lifting unit 17 raises the grinding unit 16, and the grinding wheel 1642 is temporarily separated from the plate-shaped workpiece 90.

(2-1) Grinding Wheel Moving Step After Circular Arc Groove Forming Step of Embodiment 1 Next, in order to position the grinding wheel 1642 at a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the circular arc groove forming step of embodiment 1, at least one of the grinding wheel 1642 and the chuck table 3 is moved relatively in a horizontal direction that is a direction parallel to the holding surface 302. In this embodiment, the horizontal movement unit 13 shown in FIG. 3 moves the chuck table 3 in steps by a predetermined distance in the +Y direction, so that the grinding wheel 1642 of the grinding unit 16 is positioned above an area in which the groove 907 on the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302 has not yet been formed.

(3-1) Multiple groove forming process by repeating the arc groove forming process and grinding wheel moving process of embodiment 1 After the grinding wheel 1642 is newly positioned in the Y-axis direction relative to the upper surface 904 of the plate-shaped workpiece 90, the grinding unit 16 is again lowered in the -Z direction at a predetermined grinding feed speed by the lifting unit 17 shown in Figure 3, and the rotating grinding wheel 1642 cuts a predetermined depth into the upper surface 904 of the plate-shaped workpiece 90 from the lower surface, which is a flat surface, to form a second arc groove 907 as shown in Figure 4.
Then, the grinding wheel moving step is performed in the same manner as described above. In this manner, by repeating the arc groove forming step and the grinding wheel moving step, a plurality of arc grooves 907 are formed on the upper surface 904 of the plate-shaped workpiece 90 from the +Y direction side to the -Y direction side of the upper surface 904 of the plate-shaped workpiece 90. As a result, for example, as shown in Figures 5 and 6, a plurality of arc grooves 907 are formed at approximately equal intervals in the traveling direction (Y-axis direction) of the plate-shaped workpiece 90 over substantially the entire surface of the upper surface 904 of the plate-shaped workpiece 90.

The multiple arc grooves 907 correct the curvature of the plate-shaped workpiece 90, and even when the grinding wheel 1642 is kept in contact with the upper surface 904 of the plate-shaped workpiece 90 that is suction-held by the holding surface 302 to grind the plate-shaped workpiece 90 that rotates along with the rotation of the chuck table 3, the frictional force acting between the grinding wheel 1642 and the upper surface 904 of the plate-shaped workpiece 90 causes the curvature of the plate-shaped workpiece 90 to return to its original position during grinding, preventing vacuum leaks and the like.

(1-2) Circular-arc groove forming process embodiment 2
For example, instead of the arc groove forming step of the first embodiment, the arc groove forming step of the second embodiment described below may be carried out.
In the arc groove forming process of the second embodiment, for example, the inclination of the holding surface 302 of the chuck table 3 with respect to the lower surface of the grinding wheel 1642 is changed relatively, and the grinding wheel 1642 is caused to cut into the upper surface 904 of the plate-like workpiece 90 held by the holding surface 302 from the outer circumferential corner of the lower surface of the grinding wheel 1642. That is, the arc groove is formed by the outer blade of the grinding wheel 1642.

Specifically, the inclination of the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIG. 7, so that when the traveling direction of the plate-shaped workpiece 90 held by suction on the chuck table 3 relative to the grinding wheel 1642 is set to the +Y direction, the entire chuck table 3 is tilted so that the front side (+Y direction side) of the chuck table 3 is lower than the rear side (-Y direction side) of the chuck table 3.

Then, the grinding unit 16 is moved in the X-axis direction by the X-axis moving unit 18 shown in FIG. 7, and the grinding unit 16 and the chuck table 3 are aligned in the X-axis direction, for example, so that the area on the -X direction side (the back side of the page) of the upper surface 904 of the plate-shaped workpiece 90, which is held by suction on the holding surface 302 of the chuck table 3, is positioned on a line extending in the imaginary Y-axis direction that passes through the center of the grinding wheel 164.

The end area on the +Y side of the upper surface 904 of the plate-shaped workpiece 90, which is held by suction on the chuck table 3 that moves stepwise in the +Y direction by the horizontal movement unit 13, is positioned below the grinding wheel 1642 of the grinding unit 16, and the movement of the chuck table 3 stops once. Then, when the grinding unit 16 descends in the -Z direction at a predetermined grinding feed rate, the grinding wheel 1642 rotating at a predetermined rotation speed cuts into the upper surface 904 of the plate-shaped workpiece 90. At this time, in this embodiment, the holding surface 302 cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the outer peripheral corner (outer blade) of the lower surface of the grinding wheel 1642. Then, by not rotating the holding surface 302 of the chuck table 3, a single arc groove 908 shown in FIG. 8 is formed in the -X direction side area of the upper surface 904 of the plate-shaped workpiece 90.

The grinding wheel 1642 cuts into the upper surface 904 from the outer blade to a position that is a predetermined height above the finishing thickness of the plate-shaped workpiece 90, forming an arc-shaped groove 908 of a predetermined depth, and then the grinding wheel 1642 rises and moves away from the plate-shaped workpiece 90.

(2-2) Grinding Wheel Moving Step After Circular-Arrow Groove Forming Step of Embodiment 2 Next, the grinding wheel 1642 and the chuck table 3 are moved relatively in the horizontal direction to position the grinding wheel 1642 at a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the circular-arc groove forming step of embodiment 2. For example, the horizontal movement unit 13 shown in FIG. 7 moves the chuck table 3 in steps by a predetermined distance in the +Y direction, whereby the grinding wheel 1642 of the grinding unit 16 is positioned above an area in which the groove 908 has not yet been formed in the −X direction side area of the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302.

(3-2) Multiple groove forming process in which the arc groove forming process and the grinding wheel moving process of the second embodiment are repeated After the grinding wheel 1642 is newly positioned in the Y-axis direction, the grinding unit 16 descends again in the -Z direction at a predetermined grinding feed rate, and the rotating grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 to a predetermined depth from the outer blade on the lower surface, forming the second arc groove 908 shown in FIG. 8. Then, the grinding wheel moving process is performed in the same manner as described above. In this way, by repeating the arc groove forming process and the grinding wheel moving process, multiple arc grooves 908 are sequentially formed from the +Y direction side to the -Y direction side in approximately the entire area on the -X direction side of the upper surface 904 of the plate-shaped workpiece 90.

For example, after forming multiple arc-shaped grooves 908 as shown in FIG. 8 sequentially from the +Y direction side to the -Y direction side over substantially the entire area on the -X direction side of the upper surface 904 of the plate-shaped workpiece 90, the grinding unit 16 is moved in the +X direction by the X-axis moving unit 18 as shown in FIG. 7, and the grinding unit 16 and the chuck table 3 are aligned in the X-axis direction so that the area on the +X direction side of the upper surface 904 of the plate-shaped workpiece 90, which is held by suction on the holding surface 302 and where grooves 908 have not yet been formed, is positioned on a line extending in the imaginary Y-axis direction that passes through the center of the grinding wheel 164.

Then, by repeating the arc groove forming step and the grinding wheel moving step of the second embodiment described above, a plurality of arc grooves 908 are sequentially formed from the +Y direction side toward the -Y direction side in substantially the entire area of the -X direction side area of the upper surface 904 of the plate-shaped workpiece 90. In this embodiment, the central area is less curved than both areas of the ±X direction sides of the upper surface 904 of the plate-shaped workpiece 90 in which the arc grooves 908 are formed, so in the example shown in FIG. 8, the multiple groove forming step is completed in a state in which no grooves 908 are formed, but further, a plurality of arc grooves 908 may be formed in the central area of the upper surface 904 as shown in FIG. 9. Since the plate-shaped workpiece 90 is particularly curved at its four corners, it is preferable that the arc grooves 908 are formed in the four corners after the multiple groove forming step.
Additionally, the arcuate grooves 908 may be formed so that the arcuate grooves 908 intersect with each other.
The plurality of arcuate grooves 908 correct the curvature of the plate-shaped workpiece 90 .

(1-3) Circular-arc groove forming process embodiment 3
For example, instead of the arc groove forming step of the first embodiment, the arc groove forming step of the third embodiment described below may be carried out.
In the arc groove forming process of embodiment 3, for example, the inclination of the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in Figure 3, so that the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302 becomes approximately parallel to the lower surface of the grinding wheel 1642.
Also, a table rotation mechanism 33 is provided for rotating the chuck table 3 around the center of the chuck table 3 as an axis.

Next, the horizontal movement unit 13 shown in FIG. 3 moves the chuck table 3 holding the plate-shaped workpiece 90 to below the grinding unit 16, and the X-axis movement unit 18 moves the grinding unit 16 in the X-axis direction, aligning the grinding wheel 164 with the plate-shaped workpiece 90. In this alignment, for example, the center of rotation of the grinding wheel 1642 is shifted horizontally by a predetermined distance from the center of the holding surface 302 of the chuck table 3 (i.e., the center of the upper surface 904 of the plate-shaped workpiece 90).

After the above alignment is performed, the grinding unit 16 descends at a predetermined grinding feed rate, and the rotating grinding wheel 1642 comes into contact with the upper surface 904 of the plate-shaped workpiece 90. Then, the lower surface (flat surface) of the grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302. In addition, by not rotating the holding surface 302 of the chuck table 3, a circular arc groove 909 is formed that passes through the center of the upper surface 904 of the plate-shaped workpiece 90 and one or two of the four corner regions.

The grinding wheel 1642 cuts into the upper surface 904 to a position that is a predetermined height above the finishing thickness of the plate-shaped workpiece 90 in the grinding process, forming an arc-shaped groove 909 of a predetermined depth as shown in FIG. 10. After that, the grinding unit 16 rises in the +Z direction, and the grinding wheel 1642 moves away from the plate-shaped workpiece 90.

(2-3) Grinding Wheel Moving Step After Circular Arc Groove Forming Step of Embodiment 3 Next, the table rotation mechanism 33 rotates the chuck table 3 by a predetermined angle and then stops the rotation, thereby positioning the grinding wheel 1642 at a position different from the position of the grinding wheel 1642 positioned relative to the plate-shaped workpiece 90 in the circular arc groove forming step of embodiment 3. This movement of the position of the plate-shaped workpiece 90 relative to the grinding wheel 1642 is performed so that the rotation trajectory of the grinding wheel 1642 passes through the arc grooves 909 that form at least one to two of the four corner regions of the upper surface 904 of the plate-shaped workpiece 90. The grinding wheel 1642 may also be positioned relative to the plate-shaped workpiece 90 so that the rotation trajectory of the grinding wheel 1642 passes through the center of the plate-shaped workpiece 90.

(3-3) Multiple groove forming process by repeating the arc groove forming process and grinding wheel moving process of embodiment 3. The grinding wheel 1642 is positioned above the plate-shaped workpiece 90 and the chuck table 3 is rotated by a predetermined angle to newly position the grinding wheel 1642 relative to the upper surface 904 of the plate-shaped workpiece 90. Then, the grinding unit 16 is again lowered at a predetermined grinding feed speed, and the rotating grinding wheel 1642 cuts a predetermined depth into the upper surface 904 of the plate-shaped workpiece 90 from the underside, forming a second arc groove 909 as shown in FIG. 10.
Then, the grinding wheel moving step is carried out in the same manner as described above. In this manner, by repeating the arc groove forming step and the grinding wheel moving step of the third embodiment several times, the arc grooves 909 are formed so as to pass through the four corner regions of the top surface 904 of the plate-like workpiece 90 intensively, i.e., the regions with a stronger degree of curvature.
Then, by completing the multiple groove forming process, the curvature of the plate-shaped workpiece 90 is corrected by the multiple arc grooves 909.

(1-4) Circular-arc groove forming step 4
For example, instead of the arc groove forming step of the first embodiment, the arc groove forming step of the fourth embodiment described below may be carried out.
In the arc groove forming process of the fourth embodiment, for example, the inclination of the holding surface 302 of the chuck table 3 with respect to the lower surface of a grinding wheel 1642 having a diameter at least larger than the size of the plate-shaped workpiece 90 is changed relatively, and the holding surface 302 cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the grinding wheel 1642 from the inner peripheral angle of the lower surface of the grinding wheel 1642. That is, a circular groove is formed by the inner blade of the grinding wheel 1642.

Specifically, the inclination of the chuck table 3 is adjusted by the inclination adjustment unit 37 shown in FIG. 11, so that when the traveling direction of the plate-shaped workpiece 90 held by suction on the chuck table 3 relative to the grinding wheel 1642 is set to the +Y direction, the entire chuck table 3 is tilted so that the front side (+Y direction side) of the chuck table 3 is higher than the rear side (-Y direction side) of the chuck table 3.

The grinding unit 16 shown in FIG. 11 is then moved in the X-axis direction, and the grinding unit 16 and the chuck table 3 are aligned in the X-axis direction so that the center of the plate-shaped workpiece 90 on the holding surface 302 of the chuck table 3 is positioned on a line extending in the imaginary Y-axis direction that passes through the center of the grinding wheel 164.

Then, the end area, for example on the +Y direction side, of the top surface 904 of the plate-shaped workpiece 90, which is sucked and held on the chuck table 3 by the horizontal movement unit 13, is positioned below the grinding wheel 1642 of the grinding unit 16, and the step movement of the chuck table 3 stops once. Then, when the grinding unit 16 descends in the -Z direction at a predetermined grinding feed speed, the grinding wheel 1642, rotating at a predetermined rotational speed, comes into contact with the top surface 904 of the plate-shaped workpiece 90.

Then, the grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 held by the holding surface 302 from the inner peripheral corner (inner blade) side of the lower surface. Then, by not rotating the holding surface 302 of the chuck table 3, a single arc-shaped groove 906 is formed in both regions on the ±X direction sides of the upper surface 904 of the plate-shaped workpiece 90, as shown in FIG. 12. At this time, the grinding wheel 1642 does not come into contact with the central region in the X-axis direction of the upper surface 904 of the plate-shaped workpiece 90, so the arc-shaped groove 906 is not formed in the central region.

The grinding wheel 1642 cuts into the upper surface 904 from the inner blade side to a position that is a predetermined height above the finishing thickness of the plate-shaped workpiece 90, forming an arc-shaped groove 906 of a predetermined depth, and then the grinding wheel 1642 rises and moves away from the plate-shaped workpiece 90.

(2-4) Grinding Wheel Moving Step After Circular Arc Groove Forming Step of Embodiment 4 Next, the grinding wheel 1642 is moved relatively in the horizontal direction to a position different from the position of the grinding wheel 1642 positioned with respect to the plate-shaped workpiece 90 in the circular arc groove forming step of embodiment 4. Specifically, the chuck table 3 moves in steps a predetermined distance in the +Y direction, and the grinding wheel 1642 of the grinding unit 16 is positioned above an area in which the groove 906 has not yet been formed in both areas on the ±X direction sides of the upper surface 904 of the plate-shaped workpiece 90.

(3-4) Multiple groove forming process by repeating the arc groove forming process and the grinding wheel moving process of the fourth embodiment The grinding unit 16 descends again at a predetermined grinding feed rate, and the rotating grinding wheel 1642 cuts into the upper surface 904 of the plate-shaped workpiece 90 from the inner peripheral corner side of the lower surface to a predetermined depth, forming a second arc groove 906 in both areas of the ±X direction of the upper surface 904. Thereafter, the same grinding wheel moving process as above is performed. In this way, by repeating the arc groove forming process and the grinding wheel moving process of the fourth embodiment, multiple arc grooves 906 are sequentially formed in both areas of the ±X direction of the upper surface 904 of the plate-shaped workpiece 90 from the +Y direction side to the -Y direction side.

After the multiple groove forming step, the plate-shaped workpiece 90, which has a greater curvature on the outer periphery side, has its curvature corrected by the multiple arcuate grooves 906 shown in FIG.
In addition, when the inner diameter of the grinding wheel 1642 is smaller than the length of the plate-shaped workpiece 90, it is not possible to form an arc-shaped groove 906 as shown in Fig. 12 in the entire area of both areas on the ±X direction sides of the upper surface 904 after the grinding wheel 1642 has passed through the central area of the plate-shaped workpiece 90 in the Y-axis direction by simply moving the chuck table 3 one span in the +Y direction from the +Y direction to the -Y direction. Therefore, as shown in Fig. 13, an arc-shaped groove 9066 is formed in each half of the plate-shaped workpiece 90. Such arc grooves 9066 are formed by first dividing one of the two regions into two equal parts in the Y-axis direction (the direction of movement of the chuck table 3) across the center of the top surface 904 of the plate-shaped workpiece 90, by stepping the chuck table 3 in the +Y direction to form half of the arc grooves 9066 at equal intervals, and then rotating the chuck table 3 by 180 degrees to form the remaining half of the arc grooves 9066 over substantially the entire other region while stepping the chuck table 3. Alternatively, after forming the half of the arc groove 9066, the inclination of the chuck table 3 is changed to form the remaining arc groove 9066.
Furthermore, by performing the arc groove forming process, grinding wheel moving process, and multiple groove forming process of embodiment 4, it is possible to prevent the outer blade of the grinding wheel 1642 from wearing out, for example, before creep feed grinding is started in the next grinding process.

(4-1) Grinding step performing in-feed grinding After the multiple groove forming step is completed, the multiple arc grooves 907 shown in Fig. 5, the multiple arc grooves 908 shown in Fig. 8, the multiple arc grooves 909 shown in Fig. 10, or the multiple arc grooves 906 shown in Fig. 12 formed on the upper surface 904 of the plate-shaped workpiece 90 are removed by grinding the upper surface 904, and the plate-shaped workpiece 90 is ground to a predetermined thickness. For example, this grinding is performed by in-feed grinding.

For example, the tilt of the chuck table 3 is adjusted by the tilt adjustment unit 37 shown in Figures 1 and 3, so that the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302 becomes approximately parallel to the lower surface of the grinding wheel 1642. Next, the horizontal movement unit 13 moves the chuck table 3 holding the plate-shaped workpiece 90 by suction to below the grinding unit 16, and the center of rotation of the grinding wheel 1642 is shifted horizontally by a predetermined distance from the center of the upper surface 904 of the plate-shaped workpiece 90 held by suction on the holding surface 302, and the rotation trajectory of the grinding wheel 1642 is aligned so that it passes through the center of the plate-shaped workpiece 90.

After the above alignment is performed, the grinding unit 16 descends at a predetermined grinding feed rate, and the grinding wheel 1642, rotating at a predetermined rotational speed, comes into contact with the top surface 904 of the plate-shaped workpiece 90. As the chuck table 3 rotates at a predetermined rotational speed, for example in the same direction as the grinding wheel 1642, the plate-shaped workpiece 90 held on the holding surface 302 also rotates, so that the grinding wheel 1642 grinds the entire top surface 904 of the plate-shaped workpiece 90.

The curvature of the plate-shaped workpiece 90 is corrected in advance by the multiple arc grooves 907 shown in FIG. 5, the multiple arc grooves 908 shown in FIG. 8, the multiple arc grooves 909 shown in FIG. 10, the multiple arc grooves 906 shown in FIG. 12, or the multiple arc grooves 9066 shown in FIG. 13 formed on the upper surface 904. Therefore, the curvature of the plate-shaped workpiece 90 is restored during the grinding process for thinning the plate-shaped workpiece 90, and the plate-shaped workpiece 90 does not separate from the holding surface 302, causing a vacuum leak.

While the thickness of the plate-shaped workpiece 90 being ground is measured by the thickness measuring unit 104 shown in Figures 1 and 3, the multiple arc grooves 907 shown in Figure 5, the multiple arc grooves 908 shown in Figure 8, the multiple arc grooves 909 shown in Figure 10, the multiple arc grooves 906 shown in Figure 12, or the multiple arc grooves 9066 shown in Figure 13 formed on the upper surface 904 are removed by the above grinding, and the upper surface 904 of the plate-shaped workpiece 90 is formed into a flat surface. Then, when the plate-shaped workpiece 90 is ground to the desired thickness, the grinding unit 16 rises, the grinding wheel 1642 is released from the plate-shaped workpiece 90, and the grinding process is completed.

(4-2) Grinding process performing creep feed grinding Instead of in-feed grinding, the multiple arc grooves 907 shown in FIG. 5, the multiple arc grooves 908 shown in FIG. 8, the multiple arc grooves 909 shown in FIG. 10, the multiple arc grooves 906 shown in FIG. 12, or the multiple arc grooves 9066 shown in FIG. 13 formed on the upper surface 904 of the plate-shaped workpiece 90 may be removed by grinding the upper surface 904, and the plate-shaped workpiece 90 may be creep feed ground to a predetermined thickness.

For example, first, the lifting unit 17 lowers the grinding unit 16 until the height position of the lower surface of the grinding wheel 1642 reaches a height position for making the plate-shaped workpiece 90 have the desired thickness (finishing thickness). In addition, the tilt adjustment unit 37 shown in Figures 1 and 3 adjusts the tilt of the chuck table 3, so that the upper surface 904 of the plate-shaped workpiece 90, which is held by suction on the holding surface 302, becomes approximately parallel to the lower surface of the grinding wheel 1642.

Then, while the grinding wheel 164 rotates at a predetermined rotational speed, the horizontal movement unit 13 shown in FIG. 1 moves, for example, the chuck table 3 that holds the plate-shaped workpiece 90 by suction in the +Y direction at a low speed, so that the upper surface 904 of the plate-shaped workpiece 90 is ground mainly by the outer surface of the rotating grinding wheel 1642.

The curvature of the plate-shaped workpiece 90 is corrected in advance by the multiple arc grooves 907 shown in FIG. 5, the multiple arc grooves 908 shown in FIG. 8, the multiple arc grooves 909 shown in FIG. 10, the multiple arc grooves 906 shown in FIG. 12, or the multiple arc grooves 9066 shown in FIG. 13 formed on the upper surface 904. Therefore, the curvature of the plate-shaped workpiece 90 is restored during the creep feed grinding process, and the plate-shaped workpiece 90 does not separate from the holding surface 302, causing a vacuum leak.

By the above grinding, the multiple arc grooves 907 shown in FIG. 5, the multiple arc grooves 908 shown in FIG. 8, the multiple arc grooves 909 shown in FIG. 10, the multiple arc grooves 906 shown in FIG. 12, or the multiple arc grooves 9066 shown in FIG. 13 formed on the upper surface 904 are removed, and the upper surface 904 of the plate-shaped workpiece 90 is formed into a flat surface. Then, the chuck table 3 moves to a predetermined position in the Y-axis direction where the grinding wheel 1642 finishes passing over the upper surface 904 of the plate-shaped workpiece 90, and the entire upper surface 904 of the plate-shaped workpiece 90 is ground by the grinding wheel 1642.

As described above, the grinding method of the present invention for grinding the upper surface 904 of the curved plate-shaped workpiece 90, in which the outer peripheral portion held by the holding surface 302 of the chuck table 3 has a force in a direction away from the holding surface 302 (+Z direction), is performed by using the annular grinding wheel 1642. The grinding wheel 1642 positioned above the plate-shaped workpiece 90 held by the holding surface 302 is lowered in a direction perpendicular to the holding surface 302, and the grinding wheel 1642 is cut into the upper surface 904 of the plate-shaped workpiece 90 without rotating the holding surface 302 to form an arc groove. In the arc groove forming process, the grinding wheel 1642 is positioned at a position different from the position of the grinding wheel 1642 positioned relative to the plate-shaped workpiece 90 in the arc groove forming process. , a grinding wheel moving step in which at least one of the grinding wheel 1642 and the chuck table 3 is moved relatively in a direction parallel to the holding surface 302, and a multiple groove forming step in which the arc groove forming step and the grinding wheel moving step are repeated to form multiple grooves on the upper surface 904 of the plate-shaped workpiece 90 to correct the curvature of the plate-shaped workpiece 90. By providing this step, the force that causes the plate-shaped workpiece 90 to separate from the holding surface 302 is reduced by forming multiple grooves before grinding the plate-shaped workpiece 90 to thin it, so that the upper surface 904 of the plate-shaped workpiece 90 is ground to remove the grooves, and the plate-shaped workpiece 90 is prevented from separating from the holding surface 302, preventing the occurrence of vacuum leaks, while grinding the plate-shaped workpiece 90 to a predetermined thickness. In addition, since the formation of multiple grooves and the grinding process are performed using only the grinding wheel 1642, the number of types of grinding wheels can be reduced, and it becomes unnecessary to keep multiple types of grinding wheels in stock in the grinding device 1.

The method for grinding a plate-shaped workpiece according to the present invention is not limited to the above embodiment, and it goes without saying that it may be implemented in various different forms within the scope of its technical concept. In addition, the configuration of the grinding device 1 shown in FIG. 1 used when implementing the grinding method may be modified as appropriate within the scope of the effects of the present invention.

90: Plate-shaped workpiece 904: Upper surface of plate-shaped workpiece 902: Lower surface of plate-shaped workpiece 9000: Protective tape 1: Grinding device 10: Device base 13: Horizontal movement unit 130: Ball screw 132: Motor 3: Chuck table 30: Porous portion 302: Holding surface 31: Frame 37: Tilt adjustment portion 371: Piston rod 35: Chuck base 11: Column 17: Lifting unit 170: Ball screw 172: Motor 16: Grinding unit 160: Rotating shaft 162: Motor 164: Grinding wheel 1641: Wheel base 1642: Grinding stone 104: Thickness measurement portion 4: Pressing mechanism 44: Pressing pad 41: Arm portion 40: Lifting mechanism 45: Swivel shaft

Claims (5)

a grinding device including a chuck table having a holding surface, a horizontal movement unit for horizontally moving the chuck table in a direction parallel to the holding surface, a grinding unit having a plurality of grinding wheels arranged in an annular shape, and a lifting unit for lifting the grinding unit in a direction perpendicular to the holding surface;
A method for grinding a plate-shaped workpiece, the method comprising the steps of: grinding an upper surface of the plate-shaped workpiece, the upper surface of the plate-shaped workpiece exerting a force in a direction away from a holding surface of the chuck table, with an annular grinding wheel;
an arc groove forming process in which the entire lower surface of a plate-shaped workpiece is pressed against the holding surface, the plate-shaped workpiece is held by the holding surface in a state where the curvature is temporarily eliminated , the grinding wheel positioned above the plate-shaped workpiece held on the holding surface is lowered in a direction perpendicular to the holding surface by the lifting unit , and the grinding wheel is cut into the upper surface of the plate-shaped workpiece without rotating the holding surface to form an arc groove;
a table moving step in which the horizontal moving unit moves the chuck table in a direction parallel to the holding surface so as to position the grinding wheel at a position different from the position of the grinding wheel positioned with respect to the plate-shaped workpiece in the arc groove forming step;
a multiple groove forming step of repeating the arc groove forming step and the table moving step to form multiple grooves on the upper surface of the plate-shaped workpiece to correct the curvature of the plate-shaped workpiece;
The method for grinding a plate-shaped workpiece includes a grinding step in which, after forming a plurality of grooves, the grinding wheel grinds the upper surface of the plate-shaped workpiece to remove the grooves and grinds the plate-shaped workpiece to a predetermined thickness. 2. The method for grinding a plate-shaped workpiece according to claim 1, wherein the grinding process comprises rotating the chuck table around the center of the holding surface as an axis, lowering the grinding wheel, which passes through the center of rotation of the plate-shaped workpiece held on the rotating holding surface, in a direction perpendicular to the holding surface by the lifting unit , so that the lower surface of the grinding wheel comes into contact with the plate-shaped workpiece, thereby grinding the plate-shaped workpiece. 2. A method for grinding a plate-shaped workpiece as described in claim 1, wherein the grinding process includes positioning the lower surface of the grinding wheel outside the outer periphery of the plate-shaped workpiece held on the holding surface and below the upper surface of the plate-shaped workpiece, and horizontally moving the chuck table by the horizontal movement unit to grind the plate-shaped workpiece. The method for grinding a plate-shaped workpiece according to claim 1, 2, or 3, wherein the arc groove forming process includes tilting the chuck table so that the front side in the direction of travel is lower than the rear side, and cutting into the upper surface of the plate-shaped workpiece held by the holding surface from the outer corner of the lower surface of the grinding wheel. 4. The method for grinding a plate-shaped workpiece according to claim 1, 2, or 3, wherein the arc groove forming process includes tilting the chuck table so that the front side in the direction of travel is higher than the rear side, and causing the holding surface to cut into the upper surface of the plate-shaped workpiece held by the grinding wheel from the inner corner of the lower surface of the grinding wheel.

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