Method for grinding a workpiece

Abstract

To prevent a specific workpiece from being ground twice when performing creep feed grinding in the state that the workpiece is held on each of a plurality of holding surfaces of a chuck table.SOLUTION: Creep feed grinding of a workpiece held on a first holding surface is performed in the state that the first holding surface is positioned on a grinding unit side seen from the center of a reference level of a chuck table including the first holding surface and a second holding surface arranged at mutually point symmetrical positions in a planar view. In so doing, creep feed grinding of a workpiece held on the second holding surface is not performed. By rotating the chuck table at a prescribed angle, creep feed grinding of the workpiece held on the second holding surface is performed after the second holding surface is positioned on the grinding unit side seen from the center of the reference level. In so doing, creep feed grinding of the workpiece held on the first holding surface is not performed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for grinding a workpiece by creep feed grinding. [Background technology]

[0002] Device chips such as IC (Integrated Circuit) and LSI (Large Scale Integration) are essential components in various electronic devices such as mobile phones, personal computers, etc. Such chips are manufactured, for example, by dividing a wafer on which a large number of devices are formed into regions each containing an individual device.

[0003] Furthermore, the wafer is often thinned before being divided in order to reduce the size and weight of the chips. One method for thinning the wafer is grinding using a grinding device. The grinding device includes, for example, a chuck table having a holding surface for holding the wafer, and a grinding unit provided above the chuck table and having a detachable spindle at the bottom end thereof, the grinding wheel having a plurality of grinding stones arranged in a circular pattern.

[0004] In such a grinding device, the wafer may be thinned by a grinding method also called creep feed grinding (see, for example, Patent Document 1). In this grinding method, the front side of the wafer is first held on the holding surface of the chuck table. Next, with the grinding unit positioned behind the chuck table, the lower surface of each of the multiple grinding wheels is positioned at a height between the rear surface (upper surface) and the front surface (lower surface) of the wafer.

[0005] Then, while the chuck table and the grinding unit are moved relative to each other in the front-rear direction, multiple grinding wheels located in front of the rotating grinding wheel are brought into contact with the upper surface (back surface) of the wafer held on the chuck table from its rear side. This causes the multiple grinding wheels to grind the upper surface (back surface) of the wafer from its rear end to its front end. As a result, the wafer is thinned to a specified finishing thickness. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-28550 A Summary of the Invention [Problem to be solved by the invention]

[0007] Grinding machines are used not only to thin disk-shaped wafers, but also to thin workpieces such as rectangular parallelepiped package substrates, such as CSP (Chip Size Package) substrates and QFN (Quad Flat Non-leaded package) substrates. Grinding machines used to grind such workpieces generally include a chuck table having a plurality of holding surfaces, each of which has the same shape (e.g., rectangular) and is parallel to one another and arranged in the front-rear direction.

[0008] When creep feed grinding is performed while the workpieces are held by each of the multiple holding surfaces, the workpieces are ground in order from the rear end, resulting in each of the multiple workpieces being thinned to a predetermined finishing thickness.

[0009] However, when multiple workpieces are thinned in this manner, only the workpiece located at the rear end of the multiple workpieces may be ground twice. Specifically, the workpiece may be first ground by multiple grinding wheels located in front of the rotating grinding wheel, and then ground again by multiple grinding wheels located behind the rotating grinding wheel.

[0010] In this case, there is a risk that the thickness of the multiple workpieces after grinding will vary, and there is also a risk that unintended saw marks will be formed on the top surface of the workpiece located at the rear end of the multiple workpieces, causing scratches or cracks on the workpiece.

[0011] In view of this, an object of the present invention is to prevent a particular workpiece from being ground twice when creep feed grinding is performed with the workpiece held on each of the multiple holding surfaces of the chuck table. [Means for solving the problem]

[0012] According to the present invention, there is provided a grinding unit including a chuck table including a reference surface, a first holding surface and a second holding surface which are arranged at positions point-symmetrical with respect to the center of the reference surface in a plan view, and which holds a workpiece on each of the first holding surface and the second holding surface; a grinding unit having a spindle at the tip of which a grinding wheel having a plurality of grinding stones arranged in a ring shape is attached; Le Along a first direction parallel to each of the first holding surface and the second holding surface Movea first moving mechanism for relatively moving the chuck table and the grinding unit along a second direction perpendicular to each of the first holding surface and the second holding surface, and a rotation mechanism for rotating the chuck table around a straight line along the second direction and passing through the center of the reference surface as a rotation axis, the method comprising the steps of: holding the workpiece on each of the first holding surface and the second holding surface while the chuck table and the grinding unit are spaced apart from each other in the first direction; a first positioning step for, after the holding step, positioning the first holding surface on the grinding unit side as viewed from the center of the reference surface, and positioning the positions of the tip surfaces of each of the plurality of grinding wheels in the second direction between the front surface and the back surface of the workpiece held on the first holding surface; Le Along the first direction Move a first grinding step in which the workpiece held on the first holding surface is ground from one end to the other end in the first direction, and the workpiece held on the second holding surface is not ground; after the first grinding step, the chuck table and the grinding unit are moved relatively along the second direction, and then the chuck table is The rule Along the first direction Move a separating step of separating the chuck table and the grinding unit in the first direction by moving the chuck table so that the chuck table and the grinding unit do not overlap in the second direction; a rotating step of rotating the chuck table by a predetermined angle after the separating step so that the second holding surface is positioned on the grinding unit side as viewed from the center of the reference surface; a second positioning step of positioning the positions in the second direction of the tip surfaces of each of the plurality of grinding wheels between the front and back surfaces of the workpiece held on the second holding surface after the separating step; Le Along the first direction Movea second grinding step of moving a grinding tool on the second holding surface to grind the workpiece held on the second holding surface from one end to the other end in the first direction, and not grinding the workpiece held on the first holding surface. Effect of the Invention

[0013] In the present invention, creep feed grinding is first performed on a workpiece held on the first holding surface in a state where the first holding surface is positioned on the grinding unit side as viewed from the center of a reference surface of a chuck table including a first holding surface and a second holding surface arranged at point-symmetrical positions to each other in a plan view. At this time, creep feed grinding is not performed on a workpiece held on the second holding surface.

[0014] Then, by rotating the chuck table by a predetermined angle, the second holding surface is positioned on the grinding unit side as viewed from the reference surface, and creep feed grinding is performed on the workpiece held on the second holding surface. At this time, creep feed grinding is not performed on the workpiece held on the first holding surface. Therefore, in the present invention, it is possible to prevent the workpieces held on the first holding surface and the second holding surface from being ground twice. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1(A) is a top view that illustrates an example of a chuck table, and FIG. 1(B) is a side view that illustrates an example of the chuck table. [Diagram 2] FIG. 2 is a partial cross-sectional side view that illustrates a schematic diagram of an example of a grinding apparatus that includes the chuck table shown in FIG. 1(A) and FIG. 1(B). [Diagram 3] FIG. 3 is a flow chart that illustrates a schematic example of a method for grinding a workpiece using the grinding apparatus illustrated in FIG. [Figure 4]FIG. 4(A) is a side view showing a schematic diagram of the holding step, FIG. 4(B) is a side view showing a schematic diagram of the first positioning step, and FIG. 4(C) is a side view showing a schematic diagram of the first grinding step. [Diagram 5] Figure 5(A) is a side view diagrammatically illustrating the separation step, Figure 5(B) is a side view diagrammatically illustrating the rotation step and the second positioning step, and Figure 5(C) is a side view diagrammatically illustrating the second grinding step. [Figure 6] FIG. 6(A) is a top view that shows a schematic diagram of a modified example of the chuck table, and FIG. 6(B) is a side view that shows a schematic diagram of the modified example of the chuck table. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a top view showing an example of a chuck table, and Fig. 1(B) is a side view showing an example of the chuck table. The chuck table 2 shown in Fig. 1(A) and Fig. 1(B) has a disk-shaped base portion 4 made of, for example, ceramics.

[0017] The base portion 4 has a flat upper surface (reference surface) 4a. The reference surface 4a is provided with a plurality of (for example, four) rectangular parallelepiped holders 6, 8, 10, and 12 arranged along a first direction (D1) parallel to the reference surface 4a and protruding along a second direction (D2) perpendicular to the reference surface 4a.

[0018] Each of the multiple holding parts 6, 8, 10, 12 has a rectangular parallelepiped frame 6a, 8a, 10a, 12a made of ceramics or the like, and a recess is formed in the upper part of each of the frames 6a, 8a, 10a, 12a. A rectangular parallelepiped porous plate 6b, 8b, 10b, 12b made of ceramics or the like is fixed in this recess.

[0019] Furthermore, the porous plates 6b, 8b, 10b, and 12b have upper surfaces parallel to the reference plane 4a. Furthermore, inside the base part 4 and the multiple holding parts 6, 8, 10, and 12, respectively, suction paths are provided to connect the lower surfaces of the porous plates 6b, 8b, 10b, and 12b to a suction source such as an ejector.

[0020] When the suction source is operated with the suction passage connected to it, negative pressure is generated in the space near the upper surfaces of the porous plates 6b, 8b, 10b, and 12b, and therefore the upper surfaces 6c, 8c, 10c, and 12c of the multiple holders 6, 8, 10, and 12 function as holding surfaces for holding the workpiece.

[0021] The reference surface 4a of the base portion 4 is provided so as to surround the upper surfaces (holding surfaces) 6c, 8c, 10c, and 12c of the holders 6, 8, 10, and 12 in a plan view. Each of the multiple holding surfaces 6c, 8c, 10c, and 12c is parallel to the reference surface 4a. The heights of the multiple holding surfaces 6c, 8c, 10c, and 12c from the reference surface 4a are approximately equal.

[0022] The holding surfaces 6c, 8c, 10c, and 12c have the same shape. Specifically, each of the holding surfaces 6c, 8c, 10c, and 12c has a rectangular shape having a pair of short sides extending along the first direction and a pair of long sides extending along a third direction (D3) perpendicular to the first and second directions.

[0023] Furthermore, the holding surface 6c and the holding surface 12c are disposed at positions that are point-symmetrical with respect to each other with respect to the center C of the reference surface 4a in a plan view. That is, the holding surface 6c and the holding surface 12c are provided so that when the holding surface 6c (holding surface 12c) is rotated 180° with the center C as the reference, the holding surface 6c and the holding surface 12c (holding surface 6c) overlap with each other.

[0024] Similarly, the holding surface 8c and the holding surface 10c are disposed at positions that are point-symmetrical with respect to each other with respect to the center C of the reference surface 4a in a plan view. That is, the holding surface 8c and the holding surface 10c are provided so that when the holding surface 8c (holding surface 10c) is rotated 180° with the center C as the reference, the holding surface 8c and the holding surface 10c overlap with each other.

[0025] Fig. 2 is a partial cross-sectional side view showing a schematic diagram of an example of a grinding device including a chuck table 2. Note that the X-axis direction (front-back direction) and the Y-axis direction (left-right direction) shown in Fig. 1 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction (up-down direction) is a direction (vertical direction) perpendicular to the X-axis and Y-axis directions.

[0026] The grinding device 14 shown in Fig. 2 includes a base 16 that supports or houses each of the components. A rectangular parallelepiped opening 16a is provided on the upper surface side of the base 16. An X-axis moving mechanism (first moving mechanism) 18 is provided inside the opening 16a. This X-axis moving mechanism 18 is connected to the chuck table 2 as described below, and moves the chuck table 2 along the X-axis direction.

[0027] The X-axis movement mechanism 18 is fixed to the bottom surface of the opening 16a and has a pair of guide rails 20 extending along the X-axis direction. A moving plate 22 is connected to the upper surface sides of the pair of guide rails 20 in a manner that allows it to slide along the pair of guide rails 20.

[0028] A screw shaft 24 extending along the X-axis direction is disposed between the pair of guide rails 20. A motor 26 for rotating the screw shaft 24 is connected to one end (rear end) of the screw shaft 24. In addition, a nut portion 28 for accommodating balls that roll on the surface of the rotating screw shaft 24 is provided on the surface of the screw shaft 24 on which a spiral groove is formed, thereby forming a ball screw.

[0029] That is, when the screw shaft 24 rotates, the balls circulate inside the nut portion 28, and the nut portion 28 moves along the X-axis direction. The nut portion 28 is fixed to the lower surface side of the moving plate 22. Therefore, when the screw shaft 24 is rotated by the motor 26, the moving plate 22 moves along the X-axis direction together with the nut portion 28.

[0030] A cylindrical support member 30 is provided on the upper surface side of the moving plate 22 to support the chuck table 2 in a rotatable manner. In Fig. 2, the chuck table 2 is attached to the support member 30 so that the first direction (D1), second direction (D2), and third direction (D3) are parallel to the X-axis direction, Y-axis direction, and Z-axis direction, respectively.

[0031] The support member 30 has a rotation mechanism including a cylindrical spindle (not shown) extending along the Z-axis direction and a rotation drive source (not shown) such as a motor that rotates the spindle. The upper end of the spindle is removably connected to the lower part of the chuck table 2. When the rotation drive source rotates the spindle, the chuck table 2 rotates together with the spindle along the Z-axis direction, with the axis of rotation being a straight line passing through the center C of the reference surface 4a.

[0032] Furthermore, the grinding device 14 has a built-in suction source (not shown), which is connected to suction paths provided inside the base 4 and each of the multiple holding parts 6, 8, 10, and 12 via a valve (not shown) or the like. Therefore, by opening the valve while the suction source is in operation, the workpiece can be held on the holding surfaces 6c, 8c, 10c, and 12c of the multiple holding parts 6, 8, 10, and 12.

[0033] A rectangular parallelepiped support structure 32 is provided behind the chuck table 2 and the X-axis moving mechanism 18 (on the right side of the paper in FIG. 2). A Z-axis moving mechanism (second moving mechanism) 34 is provided on the surface (front surface) side of the support structure 32. This Z-axis moving mechanism 34 is connected to a grinding unit 46 (described later) and moves the grinding unit 46 along the Z-axis direction.

[0034] The Z-axis movement mechanism 34 is fixed to the front surface side of the support structure 32 and has a pair of guide rails 36 extending along the Z-axis direction. A moving plate 38 is connected to the front sides of the pair of guide rails 36 in a manner that allows it to slide along the pair of guide rails 36.

[0035] A screw shaft 40 extending along the Z-axis direction is disposed between the pair of guide rails 36. A motor 42 for rotating the screw shaft 40 is connected to one end (upper end) of the screw shaft 40. In addition, a nut portion 44 for accommodating balls that roll on the surface of the rotating screw shaft 40 is provided on the surface of the screw shaft 40 on which a spiral groove is formed, thereby forming a ball screw.

[0036] That is, when the screw shaft 40 rotates, the balls circulate inside the nut portion 44, and the nut portion 44 moves along the Z-axis direction. The nut portion 44 is fixed to the back surface (rear surface) side of the moving plate 38. Therefore, when the screw shaft 40 is rotated by the motor 42, the moving plate 38 moves along the Z-axis direction together with the nut portion 44.

[0037] A grinding unit 46 is provided on the surface (front) side of the moving plate 38. The grinding unit 46 has a hollow, cylindrical support member 48 fixed to the surface side of the moving plate 38. A hollow, cylindrical housing 50 is accommodated in the support member 48. The housing 50 is fixed to the bottom wall of the support member 48 via a connecting member 52 provided on the lower surface thereof.

[0038] A cylindrical spindle 54 extending along the Z-axis direction is rotatably accommodated in the housing 50. The tip (lower end) of the spindle 54 is exposed from the housing 50 and protrudes downward from the bottom surface of the support member 48 through an opening provided in the bottom wall of the support member 48. In addition, a disk-shaped mount 56 made of metal or the like is fixed to the tip of the spindle 54.

[0039] The diameter of this mount 56 is about 80% of the diameter of the chuck table 2 (the diameter of the reference surface 4a of the base portion 4). In addition, an annular grinding wheel 58 is attached in a removable manner to the underside of the mount 56. This grinding wheel 58 has an annular wheel base 60 made of a metal such as aluminum or stainless steel, and the outer diameter of this wheel base 60 is approximately equal to the diameter of the mount 56.

[0040] The upper surface of the wheel base 60 is fixed to the lower surface of the mount 56 by fasteners such as bolts. A plurality of grinding wheels 62 are fixed to the lower surface of the wheel base 60 and are arranged in a circular pattern. Each of the grinding wheels 62 has, for example, a rectangular parallelepiped shape, and is arranged at approximately equal intervals along the circumferential direction of the wheel base 60.

[0041] The grinding wheel 62 is formed by fixing abrasive grains made of diamond, cBN (cubic boron nitride), or the like, with a bonding material (bond material) made of metal bond, resin bond, vitrified bond, or the like. However, there are no limitations on the material, shape, structure, size, etc., of the grinding wheel 62. In addition, the number of the multiple grinding wheels 62 can be set arbitrarily.

[0042] A rotary drive source (not shown) such as a motor for rotating the spindle 54 is connected to the base end (upper end) of the spindle 54. When this rotary drive source rotates the spindle 54 about a rotation axis along the Z-axis direction, the mount 56 and the grinding wheel 58 (the wheel base 60 and the multiple grinding stones 62) rotate together with the spindle 54.

[0043] Fig. 3 is a flow chart showing a schematic example of a method for grinding a workpiece using the grinding device 14. In this method, first, the workpiece is held on each of the multiple holding surfaces 6c, 8c, 10c, and 12c of the chuck table 2 (holding step: S1). Fig. 4(A) is a side view showing a schematic view of the holding step (S1).

[0044] In this holding step (S1), first, the X-axis moving mechanism 18 is operated to position the chuck table 2 at a position separated from the grinding unit 46 in the X-axis direction. Next, a plurality of workpieces 11 are loaded onto each of the plurality of holding surfaces 6c, 8c, 10c, and 12c of the chuck table 2.

[0045] The workpiece 11 is, for example, a rectangular parallelepiped package substrate such as a CSP substrate or a QFN substrate, and the shapes of its front surface (upper surface) and back surface (lower surface) are substantially the same as the shapes of the plurality of holding surfaces 6c, 8c, 10c, 12c. Next, while a suction source communicating with a suction path provided inside the chuck table 2 via a valve or the like is in operation, the valve is opened. This completes the holding step (S1).

[0046] After the holding step (S1), the grinding unit 46 is positioned at a predetermined position (first positioning step: S2). Fig. 4(B) is a side view showing the first positioning step (S2) in a schematic manner. In this first positioning step (S2), the Z-axis movement mechanism 34 adjusts the position of the grinding unit 46 so that the height (position in the Z-axis direction) of each of the tip surfaces (lower surfaces) of the multiple grinding wheels 62 is positioned between the front surface (upper surface) and the back surface (lower surface) of the workpiece 11 held by the holding surfaces 6c and 8c.

[0047] After the first positioning step (S2), creep feed grinding is performed on the workpiece 11 held on the predetermined holding surfaces (holding surfaces 6c, 8c) (first grinding step: S3). Fig. 4(C) is a side view that shows a schematic view of the first grinding step (S3).

[0048] In this first grinding step (S3), first, the rotation drive source connected to the base end of the spindle 54 is operated so as to rotate the grinding wheel 58 together with the spindle 54. Next, while keeping the grinding wheel 58 rotating, the X-axis moving mechanism 18 is operated so as to move the chuck table 2 backward along the X-axis direction.

[0049] At this time, the X-axis movement mechanism 18 moves the chuck table 2 so that the upper surface of the workpiece 11 held on the holding surfaces 6c, 8c from one end to the other end in the X-axis direction is ground by the multiple grinding wheels 62 located in front of the grinding wheel 58. Then, the X-axis movement mechanism 18 stops the chuck table 2 so that the multiple grinding wheels 62 located in front of the grinding wheel 58 do not come into contact with the workpiece 11 held on the holding surfaces 10c, 12c.

[0050] In order to grind the workpiece 11 held by the holding surfaces 6c, 8c in this manner and not to grind the workpiece 11 held by the holding surfaces 10c, 12c, it is necessary to position the holding surfaces 6c, 8c on the grinding unit 46 side (rear side of the chuck table 2) when viewed from the center C of the reference surface 4a prior to the first grinding step (S3).

[0051] Here, since the holding surfaces 6c, 8c are positioned in advance on the grinding unit 46 side (rear side of the chuck table 2) when viewed from the center C of the reference surface 4a, there is no need to adjust the position of the chuck table 2 prior to the first grinding step (S3). However, if the holding surfaces 6c, 8c are positioned on the front side of the chuck table 2, in the first positioning step (S2), the rotation mechanism adjusts the position of the chuck table 2 so that the holding surfaces 6c, 8c are positioned on the rear side.

[0052] After the first grinding step (S3), the chuck table 2 and the grinding unit 46 are separated (separating step: S4). FIG. 5(A) is a side view that shows the first grinding step (S3) in a schematic manner. In this separating step (S4), the Z-axis moving mechanism 34 is operated to raise the grinding unit 46, and then the X-axis moving mechanism 18 is operated to move the chuck table 2 forward. As a result, the chuck table 2 and the grinding unit 46 are separated in the X-axis direction until the chuck table 2 and the grinding unit 46 no longer overlap each other in the Z-axis direction.

[0053] After the separation step (S4), the chuck table 2 is rotated by a predetermined angle (rotation step: S5), and the grinding unit 46 is positioned at a predetermined position (second positioning step: S6). The order of the rotation step (S5) and the second positioning step (S6) is not limited. Fig. 5(B) is a side view that shows a schematic view of the rotation step (S5) and the second positioning step (S6).

[0054] In this rotation step (S5), the rotation mechanism connected to the chuck table 2 is operated so that the holding surfaces 10c, 12c are positioned on the grinding unit 46 side as viewed from the center C of the reference surface 4a. Specifically, the rotation mechanism rotates the chuck table 2 180° around a straight line that is along the Z-axis direction and passes through the center C of the reference surface 4a as the rotation axis.

[0055] Also, in this second positioning step (S6), the Z-axis moving mechanism 34 adjusts the position of the grinding unit 46 so that the height (position in the Z-axis direction) of the tip surface (lower surface) of each of the multiple grinding wheels 62 is positioned between the front surface (upper surface) and back surface (lower surface) of the workpiece 11 held by the holding surfaces 10c, 12c.

[0056] After the rotating step (S5) and the second positioning step (S6), creep feed grinding is performed on the workpiece 11 held on another holding surface (holding surfaces 10c, 12c) (second grinding step: S7). Fig. 5(C) is a side view showing the second grinding step (S7) in a schematic manner.

[0057] In this second grinding step (S7), first, the rotation drive source connected to the base end of the spindle 54 is operated so as to rotate the grinding wheel 58 together with the spindle 54. Next, while keeping the grinding wheel 58 rotating, the X-axis moving mechanism 18 is operated so as to move the chuck table 2 backward along the X-axis direction.

[0058] At this time, the X-axis movement mechanism 18 moves the chuck table 2 so that the upper surface of the workpiece 11 held on the holding surfaces 10c, 12c from one end to the other end in the X-axis direction is ground by the multiple grinding wheels 62 located in front of the grinding wheel 58. Then, the X-axis movement mechanism 18 stops the chuck table 2 so that the multiple grinding wheels 62 located in front of the grinding wheel 58 do not come into contact with the workpiece 11 held on the holding surfaces 6c, 8c.

[0059] 3, first, creep feed grinding is performed on the workpiece 11 held on the holding surfaces 6c, 8c in a state where the holding surfaces 6c, 8c are positioned on the grinding unit 46 side as viewed from the reference surface 4a of the chuck table 2, which includes the holding surfaces 6c, 8c and the holding surfaces 10c, 12c that are point symmetrical to each other in a plan view. At this time, creep feed grinding is not performed on the workpiece 11 held on the holding surfaces 10c, 12c.

[0060] Then, by rotating the chuck table 2 by 180°, the holding surfaces 10c, 12c are positioned on the grinding unit 46 side as viewed from the reference surface 4a, and creep feed grinding is then performed on the workpiece 11 held on the holding surfaces 10c, 12c. At this time, creep feed grinding is not performed on the workpiece 11 held on the holding surfaces 6c, 8c. Therefore, in the grinding method of the workpiece shown in Fig. 3, it is possible to prevent the workpiece 11 held on the holding surfaces 6c, 8c and the holding surfaces 10c, 12c from being ground twice.

[0061] The above is one aspect of the present invention, and the present invention is not limited to the above. For example, in the chuck table used in the present invention, the shape of the multiple holding surfaces is not limited to a rectangle, and may be a polygon having three or five or more corners, a circle, or an ellipse.

[0062] In addition, in the chuck table used in the present invention, the base portion 4 may be a rectangular parallelepiped or an elliptical plate. In addition, in the chuck table used in the present invention, it is sufficient that a plurality of holding surfaces are provided that are point symmetrical with each other, and the arrangement of the plurality of holding surfaces is not limited to the arrangement of the plurality of holding surfaces 6c, 8c, 10c, and 12c shown in FIG.

[0063] Fig. 6(A) is a top view showing a modified example of the chuck table, and Fig. 6(B) is a side view showing a modified example of the chuck table. Chuck table 64 shown in Fig. 6(A) and Fig. 6(B) has a disk-shaped base portion 66 made of a metal material such as stainless steel.

[0064] The base portion 66 has a flat upper surface (reference surface) 66a. A plurality of (for example, four) rectangular parallelepiped holders 68, 70, 72, and 74 are provided on the reference surface 66a so as to protrude along a second direction (D2) perpendicular to the reference surface 66a.

[0065] Each of the multiple holding parts 68, 70, 72, 74 has a rectangular parallelepiped frame 68a, 70a, 72a, 74a made of a metal material such as stainless steel, and a recess is formed in the upper part of each of the frames 68a, 70a, 72a, 74a. A rectangular parallelepiped porous plate 68b, 70b, 72b, 74b made of ceramics or the like is fixed in this recess.

[0066] Furthermore, the porous plates 68b, 70b, 72b, and 74b have upper surfaces parallel to the reference surface 66a. Furthermore, suction paths are provided inside the base portion 66 and the multiple holding portions 68, 70, 72, and 74, respectively, for connecting the lower surfaces of the porous plates 68b, 70b, 72b, and 74b to a suction source such as an ejector.

[0067] When the suction source is operated with the suction passage connected to it, negative pressure is generated in the space near the upper surfaces of the porous plates 68b, 70b, 72b, and 74b. Therefore, in each of the multiple holding parts 68, 70, 72, and 74, the upper surfaces 68c, 70c, 72c, and 74c function as holding surfaces for holding the workpiece.

[0068] The reference surface 66a of the base portion 66 is provided so as to surround the upper surfaces (holding surfaces) 68c, 70c, 72c, and 74c of the holding portions 68, 70, 72, and 74 in a plan view. Each of the holding surfaces 68c, 70c, 72c, and 74c is parallel to the reference surface 66a. The heights of the holding surfaces 68c, 70c, 72c, and 74c from the reference surface 66a are approximately equal.

[0069] Furthermore, the multiple holding surfaces 68c, 70c, 72c, and 74c have the same shape and are arranged at positions that are point-symmetrical to one another with respect to the center C of the reference surface 66a in a plan view. That is, the multiple holding surfaces 68c, 70c, 72c, and 74c are provided so that when the holding surface 68c is rotated 90° with respect to the center C, it overlaps with the holding surface 70c, when rotated 180° it overlaps with the holding surface 72c, and when rotated 270° it overlaps with the holding surface 74c.

[0070] When grinding workpieces held on each of the multiple holding surfaces 68c, 70c, 72c, 74c of the chuck table 64, for example, after performing the above-mentioned holding step (S1) and first positioning step (S2), the rotation angle of the chuck table 2 in the above-mentioned rotation step (S4) is set to 90°, and the above-mentioned separation step (S3) to second grinding step (S7) are repeated three times.

[0071] When the workpieces held on each of the multiple holding surfaces 68c, 70c, 72c, and 74c are ground in this manner, as described above, it is possible to prevent the workpieces from being ground twice. Furthermore, in this case, multiple workpieces are not ground at the same time. Therefore, even when a grinding wheel 58 having a relatively short diameter (for example, a grinding wheel 58 having a diameter of 60% or less of the diameter of the chuck table 2) is used, it is possible to prevent the workpieces held on each of the multiple holding surfaces 68c, 70c, 72c, and 74c from being ground twice.

[0072] In addition, in the grinding device used in the present invention, the X-axis moving mechanism 18 may be replaced with an X-axis moving mechanism that moves the grinding unit 46 along the X-axis direction. That is, in the grinding device used in the present invention, it is only necessary that the chuck table 2 and the grinding unit 46 can move relatively along the X-axis direction, and the components therefor are not limited.

[0073] Similarly, in the grinding device used in the present invention, the Z-axis movement mechanism 34 may be replaced with a Z-axis movement mechanism that moves the chuck table 2 along the Z-axis direction. That is, in the grinding device used in the present invention, it is only necessary that the chuck table 2 and the grinding unit 46 can move relatively along the Z-axis direction, and the components therefor are not limited.

[0074] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0075] 2: Chuck table 4: Base part (4a: Top surface (reference surface)) 6: Holding part (6a: frame body, 6b: porous plate, 6c: top surface (holding surface)) 8: Holding part (8a: frame body, 8b: porous plate, 8c: top surface (holding surface)) 10: Holding part (10a: frame body, 10b: porous plate, 10c: top surface (holding surface)) 12: Holding part (12a: frame body, 12b: porous plate, 12c: top surface (holding surface)) 14: Grinding equipment 16: Base (16a: opening) 18:X-axis movement mechanism (first movement mechanism) 20: Guide rail 22: Moving plate 24: Screw shaft 26: Motor 28: Nut part 30: Support member 32:Support structure 34:Z-axis movement mechanism (second movement mechanism) 36: Guide rail 38: Moving plate 40: Screw shaft 42: Motor 44: Nut part 46: Grinding unit 48: Support member 50: Housing 52: Connection parts 54: Spindle 56: Mount 58: Grinding wheel 60: Wheel base 62: Grinding wheel 64: Chuck table 66: Base part (66a: Top surface (reference surface)) 68: Holding part (68a: frame body, 68b: porous plate, 68c: top surface (holding surface)) 70: Holding part (70a: frame body, 70b: porous plate, 70c: top surface (holding surface)) 72: Holding part (72a: frame body, 72b: porous plate, 72c: top surface (holding surface)) 74: Holding part (74a: frame body, 74b: porous plate, 74c: top surface (holding surface))

Claims

[Claim 1] a chuck table including a reference surface, and a first holding surface and a second holding surface that are arranged at positions point-symmetrical with respect to a center of the reference surface in a plan view, the first holding surface and the second holding surface holding a workpiece, respectively; a grinding unit having a spindle on the tip of which a grinding wheel having a plurality of grinding stones arranged in a circular manner is attached; a first moving mechanism that moves the chuck table along a first direction parallel to each of the first holding surface and the second holding surface; a second moving mechanism that relatively moves the chuck table and the grinding unit along a second direction perpendicular to each of the first holding surface and the second holding surface; a rotation mechanism that rotates the chuck table about a rotation axis that is along the second direction and that passes through a center of the reference surface, a holding step of holding the workpiece on each of the first holding surface and the second holding surface while the chuck table and the grinding unit are separated from each other in the first direction; a first positioning step of positioning the first holding surface on the grinding unit side as viewed from the center of the reference surface after the holding step, and positioning the positions of the tip surfaces of each of the plurality of grinding wheels in the second direction between the front surface and the back surface of the workpiece held on the first holding surface; a first grinding step in which, after the first positioning step, the chuck table is moved along the first direction while rotating the spindle, and the workpiece held on the first holding surface is ground from one end to the other end in the first direction, and the workpiece held on the second holding surface is not ground; a separating step of, after the first grinding step, moving the chuck table and the grinding unit relatively along the second direction, and then moving the chuck table along the first direction, thereby separating the chuck table and the grinding unit in the first direction until the chuck table and the grinding unit do not overlap each other in the second direction; a rotating step of rotating the chuck table by a predetermined angle so that the second holding surface is positioned on the grinding unit side as viewed from the center of the reference surface after the separating step; a second positioning step of positioning the positions of the tip surfaces of each of the plurality of grinding wheels in the second direction between the front surface and the back surface of the workpiece held on the second holding surface after the separating step; a second grinding step of moving the chuck table along the first direction after the rotating step and the second positioning step, grinding the workpiece held on the second holding surface from one end to the other end in the first direction, and not grinding the workpiece held on the first holding surface; A method for grinding a workpiece, comprising:

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