Grinding wheel and grinding method

Abstract

To provide a grinding wheel and a grinding method which can prevent adhesion of grinding chips to the inner peripheral surface of pipe grindstone, and can prevent a deep flaw from damaging workpiece due to lowering of grinding force by grinding chips.SOLUTION: In a grinding wheel 25 having an annular base 25A, a plurality of pipe grindstones 25B annularly arranged on the annular base 25A, and a grinding water supply part for supplying grinding water to the pipe grindstones 25B, the grinding water supply part includes a ring-shaped grinding water accumulation part S1 formed between the mounting surface and an opposite surface of the annular base 25A, a water supply hole 8 opened in the mounting surface, and a water sending hole 9 making the grinding water accumulation part S1 and the inside of the pipe grindstone 25B communicate with each other. A grinding method is a method for temporarily accumulating grinding water in the grinding water accumulation part S1 of the annular base 25A by centrifugal force by rotation of the grinding wheel 25, and grinding a resin R (workpiece) by the pipe grindstone 25B while supplying the accumulated grinding water to the inside of the pipe grindstone 25B.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a grinding wheel for grinding a workpiece with a plurality of pipe grindstones, and a grinding method for grinding a workpiece held on a chuck table using the grinding wheel.

Background Art

[0002] In the manufacturing process of semiconductor devices such as ICs and LSIs used in various electronic devices, in order to miniaturize and lighten the semiconductor devices, the back surface of the wafer is ground by a grinding device to be thinned to a predetermined thickness. In such a grinding device, a grinding wheel that grinds a wafer by bringing the lower surfaces of a plurality of pipe grindstones annularly arranged on an annular base into contact with the wafer is attached to the tip of a spindle (see, for example, Patent Documents 1 and 2). In such a grinding device, when grinding a wafer, grinding water is supplied into each pipe grindstone to cool the contact portion (grinding portion) between the pipe grindstone and the wafer with the grinding water, and at the same time, the grinding chips generated by grinding the wafer are washed away with the grinding water.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the grinding water supplied to the inside of each pipe grinding wheel is subjected to the centrifugal force caused by the rotation of the grinding wheel, the grinding water flows down in a state where it is biased radially outward of the grinding wheel inside each pipe grinding wheel. As a result, grinding chips enter the inside from the lower end of the pipe grinding wheel and adhere to the inner peripheral surface of each pipe grinding wheel. This adhered grinding chip is sandwiched between the lower end of each pipe grinding wheel and the upper surface of the workpiece, resulting in a problem that the grinding force of the pipe grinding wheel is reduced and a deep scratch is made on the upper surface of the workpiece.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a grinding wheel and a grinding method capable of preventing the adhesion of grinding chips to the inner peripheral surface of a pipe grinding wheel and preventing the workpiece from being deeply scratched due to a reduction in grinding force caused by the grinding chips.

Means for Solving the Problems

[0006] The present invention for achieving the above object includes an annular base whose mounting surface is mounted on a spindle mount, a plurality of pipe grinding wheels annularly arranged on the opposite surface of the annular base opposite to the mounting surface, and a grinding water supply unit that supplies grinding water to the pipe grinding wheels. It is a grinding wheel for grinding a workpiece with the pipe grinding wheels, and the grinding water supply unit includes an annular grinding water retention portion formed between the mounting surface and the opposite surface of the annular base, a water supply hole opening on the mounting surface, and a water supply hole communicating the grinding water retention portion with the inside of the pipe grinding wheel.

[0007] Further, the present invention is a grinding method for grinding a workpiece with the pipe grinding wheels while supplying grinding water to the inside of the plurality of pipe grinding wheels of the grinding wheel. The grinding water is temporarily retained in the grinding water retention portion by the centrifugal force caused by the rotation of the grinding wheel, and the retained grinding water is supplied from the upper end of the pipe grinding wheel into the inside of the pipe grinding wheel while grinding the workpiece with the lower end of the pipe grinding wheel.

Effects of the Invention

[0008] According to the present invention, the grinding water ejected from the water supply holes of the annular base is temporarily retained in the grinding water retention part by the centrifugal force caused by the rotation of the grinding wheel and then supplied to the inside of each pipe grindstone. Therefore, the grinding water is uniformly supplied to each pipe grindstone, and the adhesion of the grinding chips contained in the grinding water to the inner surface of each pipe grindstone is suppressed. As a result, the adhesion of the grinding chips to the inner peripheral surface of the pipe grindstone is prevented, and the effect that the grinding chips can prevent the workpiece from being deeply scratched due to the reduction of the grinding force can be obtained.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

[0011] [Configuration of Grinding Apparatus] First, the configuration of a grinding apparatus equipped with a grinding wheel according to the present invention will be described with reference to FIGS. 1 to 3. In the following description, the directions of the arrows shown in FIG. 1 are defined as the X-axis direction (left-right direction), the Y-axis direction (front-back direction), and the Z-axis direction (up-down direction), respectively.

[0012] The grinding apparatus 1 shown in FIG. 1 is for grinding a resin R (see FIG. 2), which is a workpiece covering the upper surface of a disk-shaped wafer W, and includes the following components. That is, the grinding apparatus 1 includes a chuck table 10 that holds the wafer W and rotates around its axis, a grinding unit 20 that grinds the resin R covering the wafer W held and sucked by the chuck table 10, a thickness measuring device 30 that measures the thickness of the wafer W including the resin R during grinding, a lifting mechanism 40 that raises and lowers the grinding unit 20 in the vertical direction (Z-axis direction) with respect to the holding surface 10a of the chuck table 10, a horizontal movement mechanism 50 that moves the chuck table 10 in the horizontal direction (Y-axis direction) with respect to the holding surface 10a, and a grinding water supply unit 60 that supplies grinding water to the grinding portion of the resin R as main components.

[0013] Here, the wafer W is a thin disk-shaped member made of a single-crystal silicon base material. As shown in FIG. 2, a plurality of devices D are mounted on its upper surface, and these devices are coated and protected by the resin R. Also, a tape T is attached to the lower surface of the wafer W. Then, the wafer W is sucked and held on the holding surface 10a of the chuck table 10 via the tape T, and the resin R on the upper surface is ground by the grinding unit 20.

[0014] Next, the configurations of the main components of the grinding apparatus 1, namely, the chuck table 10, the grinding unit 20, the thickness measuring device 30, the lifting mechanism 40, the horizontal movement mechanism 50, and the grinding water supply unit 60, will be described respectively.

[0015] (Chuck Table) The chuck table 10 is a disk-shaped member, and a disk-shaped porous member 10A is incorporated in the upper central portion thereof as shown in FIG. 2. Here, the porous member 10A is made of a porous ceramic or the like, and its upper surface constitutes a holding surface 10a for sucking and holding the disk-shaped wafer W. The porous member 10A of the chuck table 10 is selectively connected to a suction source 13 such as a vacuum pump via suction paths 2 and 3 formed at the respective axial centers of the chuck table 10 and a rotary shaft 11 that rotatably supports the chuck table 10, and a pipe 12 connected to the suction path 3. An on-off valve V1 for selectively connecting the porous member 10A to the suction source 13 is provided in the pipe 12.

[0016] The chuck table 10 is rotationally driven at a predetermined speed around its axis by a rotation mechanism (not shown). That is, in the chuck table 10, the rotary shaft 11 is rotationally driven at a predetermined speed by a rotation mechanism (not shown).

[0017] Further, as shown in FIG. 1, the grinding apparatus 1 includes a rectangular box-shaped base 100 that is long in the Y-axis direction (front-rear direction). The chuck table 10 faces a rectangular opening 100a that is long in the Y-axis direction and opens in the base 100. The periphery of the chuck table 10 in the opening 100a is covered by a rectangular plate-shaped cover 14, and the front and rear (-Y direction and +Y direction) portions of the cover 14 in the opening 100a are respectively covered by bellows-shaped expansion and contraction covers 15 and 16 that move and expand and contract together with the cover 14.

[0018] (Grinding unit) As shown in FIG. 1, the grinding unit 20 includes a spindle motor 22 housed in a holder 21, a vertical spindle 23 rotationally driven around its axis by the spindle motor 22, a disk-shaped spindle mount 24 coupled to the lower end of the spindle 23, and a grinding wheel 25 whose mounting surface (upper surface) is detachably mounted on the lower surface of the spindle mount 24 by a plurality of bolts 26 (see FIGS. 2 and 3).

[0019] Here, as shown in FIG. 2, supply paths 4 and 5 are respectively formed vertically at the axial centers of the spindle 23 and the spindle mount 24. In the spindle mount 24, a plurality of supply paths 6 that extend horizontally and radially outward from the supply path 5 are formed, and supply paths 7 that extend vertically downward from each supply path 6 are formed. Although not shown, a supply path is also formed vertically at the axial center of the rotor of the spindle motor 22.

[0020] Next, the details of the configuration of the grinding wheel 25 according to the present invention will be described below with reference to FIGS. 2 to 6.

[0021] As shown in FIGS. 4 and 5, the grinding wheel 25 is composed of an annular base 25A and a plurality of pipe grinding wheels 25B which are cutting tools vertically attached to the lower surface (the opposite surface to the mounting surface on the upper surface) of the annular base 25A. Here, in the present embodiment, as shown in FIG. 5, 24 pipe grinding wheels 25B are annularly arranged on the opposite surface (the upper surface in FIG. 5) of the annular base 25A at an equal angular pitch (15° pitch) in the circumferential direction.

[0022] By the way, as shown in FIGS. 3 and 6, a tapered circular hole-shaped space S is formed between the mounting surface (upper surface) and the opposite surface (lower surface) of the annular base 25A of the grinding wheel 25. An annular grinding water retention portion S1 for temporarily retaining the grinding water flowing radially outward by the centrifugal force due to the rotation of the grinding wheel 25 is formed on the outer peripheral portion of this space S. Here, the grinding water retention portion S1 is annularly formed by a tapered surface 25a that defines the space S of the annular base 25A, a vertical surface 25b continuous with the tapered surface 25a, and a bottom surface 25c. The inner peripheral surface of the grinding water retention portion S1 forms an annular opening S11 that opens to the atmosphere. Further, in the present embodiment, as shown in FIG. 6, the vertical surface 25b of the annular base 25A that defines the grinding water retention portion S1 and a part of the inner peripheral surface of each pipe grinding wheel 25B coincide.

[0023] Then, as shown in FIG. 3, the annular base 25A is vertically formed with a plurality of circular water supply holes 8 that communicate with the respective supply paths 7 formed in the spindle mount 24. Each water supply hole 8 opens to the mounting surface (upper surface) of the annular base 25A and the grinding water retention portion S1, respectively. Here, in the present embodiment, as shown in FIG. 4, 24 water supply holes 8 are opened on the mounting surface (upper surface) of the annular base 25A at an equal angular pitch (15° pitch) in the circumferential direction.

[0024] Also, as shown in FIGS. 3 and 6, a plurality of circular water delivery holes 9 that communicate the grinding water retention portion S1 and the inside of each pipe grindstone 25B are formed at the bottom of the annular base 25A. Here, the grinding water retention portion S1 formed inside the annular base 25A of the grinding wheel 25, the plurality of water supply holes 8 and water delivery holes 9 formed in the annular base 25A constitute a grinding water supply portion for supplying grinding water to the inside of each pipe grindstone 25B. Note that, as shown in FIG. 4, the annular base 25A is formed with a plurality (eight in the illustrated example) of screw holes 27 into which bolts 26 (see FIGS. 2 and 3) for fastening the annular base 25A to the spindle mount 24 are screwed at an equal angular pitch (45° pitch) in the circumferential direction.

[0025] (Thickness measuring device) The thickness measuring device 30 is a measuring device that measures the thickness of the wafer W including the resin R being ground and held on the chuck table 10, and includes a first probe 31 that contacts the upper surface of the resin R and a second probe 32 that contacts the upper surface of the chuck table 10. Here, in the thickness measuring device 30, the upper surface height of the resin R being ground is measured by the first probe 31, and the thickness of the wafer W including the resin R and the tape T is obtained by the difference between the upper surface height of the resin R measured by the first probe 31 and the upper surface height of the chuck table 10 measured by the second probe 32.

[0026] (Lifting mechanism) The elevating mechanism 40 raises and lowers the grinding unit 20 along the direction (Z-axis direction) perpendicular to the holding surface 10a of the chuck table 10. As shown in Fig. 1, it is arranged on the -Y-axis direction end face (front face) of a rectangular box-shaped column 110 vertically erected on the +Y-axis direction end part (rear end part) of the upper surface of the base 100. This elevating mechanism 40 raises and lowers a rectangular plate-shaped elevating plate 41 attached to the back surface of the holder 21 of the grinding unit 20 along the Z-axis direction along a pair of left and right guide rails 42 together with the holder 21, the spindle 23 held by the holder 21, and the grinding wheel 25. Here, the pair of left and right guide rails 42 are arranged vertically and parallel to each other on the front face of the column 110.

[0027] Also, between the pair of left and right guide rails 42, a rotatable ball screw 43 is vertically erected along the Z-axis direction (vertical direction). The upper end of the ball screw 43 is connected to a servo motor 44 that can rotate forward and backward, which is a drive source. Here, the servo motor 44 is mounted vertically on the column 110 via a rectangular plate-shaped bracket 45 attached to the upper surface of the column 110. Also, the lower end of the ball screw 43 is rotatably supported by the column 110. A nut member (not shown) that protrudes horizontally rearward (+Y-axis direction) from the back surface of the elevating plate 41 is screwed onto this ball screw 43.

[0028] Therefore, if the servo motor 44 is activated to rotate the ball screw 43 forward and backward, the elevating plate 41 to which a nut member (not shown) screwed onto the ball screw 43 is attached moves up and down along the pair of guide rails 42 together with the grinding unit 20. Thus, the grinding unit 20 moves up and down, and the grinding amount (grinding cost) of the pipe grinding wheel 25B with respect to the resin R is set.

[0029] (Horizontal movement mechanism) The horizontal movement mechanism 50 is a mechanism that moves the chuck table 10 in the horizontal direction (Y-axis direction) with respect to the holding surface 10a. As shown in FIG. 1, it is disposed on a rectangular block-shaped inner base 120 housed inside the base 100. This horizontal movement mechanism 50 includes a block-shaped slider 51, and this slider 51 is slidable in the Y-axis direction along a pair of left and right guide rails 52 arranged in parallel to each other along the Y-axis direction (front-rear direction). Therefore, the chuck table 10 supported by this slider 51 is movable along the Y-axis direction together with the slider 51.

[0030] And between the pair of left and right guide rails 52 on the inner base 120, a rotatable ball screw 53 extending in the Y-axis direction (front-rear direction) is disposed. One end of the ball screw 53 in the Y-axis direction (the left end in FIG. 1) is connected to a servomotor 54 capable of normal and reverse rotation, which is a drive source. Also, the other end of the ball screw 53 in the Y-axis direction (the right end in FIG. 1) is rotatably supported by the inner base 120 by a bearing 55 erected on the inner base 120. And a nut member (not shown) protruding downward from the slider 51 is screwed onto this ball screw 53.

[0031] Therefore, when the servomotor 54 is activated to rotate the ball screw 53 forward and backward, the nut member (not shown) screwed onto this ball screw 53 slides along the ball screw 53 in the Y-axis direction (front-rear direction) together with the slider 51. As a result, the chuck table 10 also moves integrally along the Y-axis direction together with the slider 51. Consequently, the wafer W sucked and held on the holding surface 10a of the chuck table 10 also moves along the Y-axis direction.

[0032] (Grinding water supply unit) The grinding water supply unit 60 supplies grinding water to a plurality of pipe grindstones 25B of the grinding wheel 25, precisely to the contact portion (grinding portion) between the resin R being ground and the pipe grindstone 25B. As shown in Fig. 1, it includes a grinding water supply source 61 and a pipe 62 that extends from the grinding water supply source 61 and is connected to the axial center of the spindle motor 22 of the grinding unit 20. An on-off valve V2 is provided in the pipe 62. Note that pure water is preferably used as the grinding water.

[0033] [Operation of the grinding device] Next, the operation of the grinding device 1 configured as described above, that is, the method of grinding the resin R covering the upper surface of the wafer W, will be described.

[0034] When grinding the resin R with the grinding device 1 shown in Fig. 1, as shown in Fig. 2, the wafer W is placed on the holding surface 10a of the chuck table 10 with the tape T facing down. Then, when the on-off valve V1 provided in the pipe 12 shown in Fig. 2 is opened, the porous member 10A of the chuck table 10 is evacuated by the suction source 13, so a negative pressure is generated in the porous member 10A, and the wafer W placed on the holding surface 10a of the porous member 10A via the tape T is suction-held on the holding surface 10a by the negative pressure.

[0035] From the above state, the horizontal movement mechanism 50 shown in Fig. 1 is driven to move the chuck table 10 in the +Y-axis direction (rearward), and the wafer W suction-held by the chuck table 10 is positioned below the grinding wheel 25 of the grinding unit 20. That is, when the servo motor 54 is activated to rotate the ball screw 53, a slider 51 to which a nut member (not shown) screwed onto the ball screw 53 is attached slides in the +Y-axis direction along a pair of left and right guide rails 52 together with the chuck table 10 and the like, so the wafer W held on the holding surface 10a of the chuck table 10 is positioned below the grinding wheel 25 of the grinding unit 20. At this time, the horizontal positional relationship between the two is adjusted so that the lower surface (processing surface) of the pipe grindstone 25B passes through the center of the wafer W (resin R).

[0036] Thereafter, a rotation mechanism (not shown) is driven to rotate the chuck table 10, and the wafer W held on the holding surface 10a of the chuck table 10 is rotated at a predetermined speed together with the resin R. At the same time, the spindle motor 22 of the grinding unit 20 is driven to rotate the grinding wheel 25 at a predetermined speed.

[0037] As described above, with the wafer W and the grinding wheel 25 rotating, the lifting mechanism 40 is driven to lower the grinding wheel 25 in the -Z axis direction. Then, the lower surface (grinding surface) of the pipe grindstone 25B of the grinding wheel contacts the resin R covering the upper surface of the wafer W, and as the pipe grindstone 25B descends at a constant feed rate, the entire upper surface of the resin R covering the upper surface of the wafer W is ground. Note that the thicknesses of the wafer W including the tape T and the resin R during the grinding process are measured by the thickness measuring device 30.

[0038] Also, as described above, when the entire upper surface of the resin R covering the upper surface of the wafer W is being ground by the lower surface (grinding surface) of the pipe grindstone 25B while rotating the grinding wheel 25, grinding water is supplied by the grinding water supply unit 60 to the contact portion (grinding portion) between the resin R and the pipe grindstone 25B. That is, when the on-off valve V2 provided in the pipe 62 of the grinding water supply unit 60 is opened, grinding water is supplied from the grinding water supply source 61 to the grinding unit 20 via the pipe 62. The grinding water supplied to the grinding unit 20 is supplied to the grinding wheel 25 from a supply path (not shown) formed on the axis of the spindle motor 22 and a supply path 4 formed on the axis of the spindle 23. Then, the grinding water supplied to the grinding wheel 25 flows through a plurality of supply paths 6, 7 from the supply path 5 formed on the spindle mount 24 and jets out from a plurality of water supply holes 8 formed on the annular base 25A toward the space S formed on the annular base 25A, as indicated by the arrows in FIGS. 2 and 3.

[0039] Since the grinding wheel 25 is rotating at a predetermined speed, centrifugal force acting radially outward is applied to the grinding water ejected from the plurality of water supply holes 8 of the annular base 25A toward the space S. Due to this centrifugal force, the grinding water hits the vertical surface 25b of the ring-shaped grinding water retention part S1 on the outer peripheral part of the space S of the annular base 25A, and the flow of the grinding water can be temporarily stopped. The grinding water is temporarily retained in the grinding water retention part S1. Then, the grinding water temporarily retained in the grinding water retention part S1 of the annular base 25A is supplied into the interior of each pipe grinding stone 25B through the plurality of water supply holes 9. That is, since the flow of the grinding water toward the radially outer side of the grinding wheel 25 is stopped by the vertical surface 25b, the grinding water flowing into the interior of the pipe grinding stone 25B flows down inside the pipe grinding stone 25B in a state where it is slightly more toward the rear in the rotation direction of the grinding wheel 25 due to the rotation of the grinding wheel 25. Therefore, adhesion of grinding chips to the portion of the inner side surface of the pipe grinding stone 25B that hits the rear in the rotation direction of the grinding wheel 25 is prevented.

[0040] Also, when the amount of the grinding water temporarily retained in the grinding water retention part S1 of the annular base 25A increases beyond a predetermined amount, a part of the grinding water overflows into the atmosphere from the ring-shaped annular opening S11 formed on the inner peripheral surface of the grinding water retention part S1. Then, as indicated by the arrows in FIGS. 3 and 6, the grinding water that has overflowed into the atmosphere is scattered radially outward under the centrifugal force caused by the rotation of the grinding wheel 25 and is supplied to the outer peripheral surfaces of the respective pipe grinding stones 25B.

[0041] As described above, when the grinding water is supplied to the interior of each pipe grinding stone 25B and the outer peripheral surfaces of the respective pipe grinding stones 25B, it is supplied to the contact part (grinding part) between each pipe grinding stone 25B and the resin R, which is the workpiece. The contact part is cooled by the grinding water, and the grinding chips generated by grinding are washed away by the grinding water and removed from the surface of the resin R.

[0042] Thus, according to the grinding wheel 25 according to the present embodiment, without directly supplying grinding water to each pipe grindstone as in the prior art, the grinding water is temporarily retained in the grinding water retention portion S1 of the annular base 25A by the centrifugal force generated by the rotation of the grinding wheel 25, and is supplied from the grinding water retention portion S1 into the interior of each pipe grindstone 25B. At the same time, the grinding water that has overflowed from the grinding water retention portion S1 is supplied to the outer peripheral surface of each pipe grindstone 25B. Therefore, grinding water is supplied to both the inside and outside of each pipe grindstone 25B, and the adhesion of grinding chips to the inner and outer surfaces of each pipe grindstone 25B is suppressed. As a result, the adhesion of grinding chips to the inner peripheral surface of the pipe grindstone 25B is prevented, and it is possible to prevent the resin R, which is the workpiece, from being deeply scratched by the grinding chips.

[0043] Next, modified examples of the grinding wheel 25 according to the present invention will be described with reference to FIGS. 7 to 9, respectively. In FIGS. 7 to 9, the same reference numerals are given to the same elements as those shown in FIG. 6, and the repeated description thereof will be omitted below.

[0044] <First Modified Example> In the grinding wheel 25X according to the first modified example shown in FIG. 7, each pipe grindstone 25B is obliquely attached with its center line CL inclined radially outward (to the right in FIG. 7) by the illustrated angle α with respect to the vertical line N, and the other configuration is the same as that of the grinding wheel 25 shown in FIG. 6. Note that the lower end surface (grinding surface) of each pipe grindstone 25B constitutes a horizontal plane.

[0045] Thus, also in the grinding wheel 25X according to this modified example, the grinding water ejected from the water supply hole 8 of the annular base 25A into the space S is temporarily retained in the grinding water retention portion S1 by the centrifugal force generated by the rotation of the grinding wheel 25X, and is supplied from the grinding water retention portion S1 into the interior of each pipe grindstone 25B. At the same time, the grinding water that has overflowed from the grinding water retention portion S1 is supplied to the outer peripheral surface of each pipe grindstone 25B. Therefore, grinding water is supplied to both the inside and outside of each pipe grindstone 25B, and the adhesion of grinding chips to the inner surface of each pipe grindstone 25B is suppressed. As a result, the adhesion of grinding chips to the inner peripheral surface of the pipe grindstone 25B is prevented, and the effect of preventing the upper surface of the resin R, which is the workpiece, from being deeply scratched can be obtained.

[0046] And in the grinding wheel 25X according to this modification example, since each pipe grindstone 25B is attached such that its center line CL is inclined radially outward (to the right in FIG. 7) by the illustrated angle α with respect to the vertical line N, particularly when the workpiece is a soft resin R as in this embodiment, the inclined pipe grindstone 25B can efficiently grind the surface of the resin R.

[0047] Also, when each pipe grindstone 25B is attached such that its center line CL is inclined radially outward by the illustrated angle α with respect to the vertical line N, a component force F1 = F·sinα of the horizontal outward centrifugal force F acting on the grinding water flowing obliquely downward along the inner peripheral surface of these pipe grindstones 25B in the direction along the inner peripheral surface of each pipe grindstone 25B acts. However, due to the vertical surface 25b, the grinding water flows downward in the vertical direction, so that the grinding water is also supplied to the radially inner side of the grinding wheel 25 on the inner side surface of the pipe grindstone 25B and to the rear side in the rotation direction of the grinding wheel 25 on the inner side surface of the pipe grindstone 25B. The grinding water is efficiently supplied to the contact portion (grinding portion) between the pipe grindstone 25B and the resin R, and the effect of preventing the adhesion of grinding chips to the inner side surface of the pipe grindstone 25B is also obtained.

[0048] <Second Modification Example> In the grinding wheel 25Y according to the second modification example shown in FIG. 8, similar to the grinding wheel 25 shown in FIG. 6, each pipe grindstone 25B is vertically attached to the opposite surface (lower surface) of the annular base 25A. However, a part of the grinding water retention portion S1 formed in the annular base 25A is not open to the atmosphere (the annular opening S11 in the grinding wheel 25 shown in FIG. 6 is not provided). Therefore, the grinding water supplied from each water supply hole 8 of the annular base 25A is temporarily retained in the grinding water retention portion S1 by the centrifugal force due to the rotation of the grinding wheel 25Y, and all of it is supplied from the water supply hole 9 to the inside of each pipe grindstone 25B.

[0049] Therefore, in the grinding wheel 25Y according to this modification example, the grinding water supplied from the water supply hole 8 of the annular base 25A is temporarily retained in the grinding water retention part S1 by the centrifugal force caused by the rotation of the grinding wheel 25Y, and then supplied to the inside of each pipe grindstone 25B. As a result, the grinding water is uniformly supplied to each pipe grindstone 25B, and the adhesion of the grinding chips contained in the grinding water to the inner surface of each pipe grindstone 25B is suppressed. As a result, the adhesion of the grinding chips to the inner peripheral surface of the pipe grindstone 25B is prevented, and the effect of preventing the resin R, which is the workpiece, from being deeply scratched by the grinding chips can be obtained.

[0050] <Third Modification Example> The grinding wheel 25Z according to the third modification example shown in FIG. 9 is characterized in that, in the grinding wheel 25Y shown in FIG. 8, similar to the grinding wheel 25X shown in FIG. 7, each pipe grindstone 25B is attached with its center line CL inclined radially outward (to the right in FIG. 9) by the illustrated angle α with respect to the vertical line N. Other configurations are the same as those of the grinding wheel 25Y shown in FIG. 8.

[0051] Thus, according to the grinding wheel 25Z according to this modification example, in addition to the effect obtained by the grinding wheel 25Y shown in FIG. 8, the component force F1 = F·sinα of the horizontal outward centrifugal force F acting on the grinding water flowing obliquely downward along the inner peripheral surface of each pipe grindstone 25B in the direction along the inner peripheral surface of each pipe grindstone 25B acts. However, due to the vertical surface 25b, the grinding water flows downward in the vertical direction, so that the grinding water is also supplied to the radially inner side of the inner surface of the pipe grindstone 25B of the grinding wheel 25 and the rear side in the rotation direction of the grinding wheel 25. The grinding water is efficiently supplied to the contact part (grinding part) between the pipe grindstone 25B and the resin R, and the effect of preventing the adhesion of the grinding chips to the inner surface of the pipe grindstone 25B is also obtained.

[0052] In the above embodiments, the case of grinding the resin covering the upper surface of the wafer as the workpiece has been described as an example. However, the present invention can also be applied to the case of grinding a wafer or any other object as the workpiece to be ground.

[0053] In addition, in the above-described embodiment, as the grinding method, an infeed grinding method is adopted in which a grinding wheel is disposed at a position passing through the center of the wafer, and the grinding wheel is lowered to grind the workpiece. However, the present invention is not limited to this grinding method, and a creep feed grinding method may be adopted in which the workpiece and the grinding wheel are relatively moved in the horizontal direction to grind the upper surface of the workpiece so as to shave it off.

[0054] In addition, the present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible within the scope of the technical idea described in the claims, the specification, and the drawings.

Explanation of Reference Numerals

[0055] 1: Grinding device, 2, 3: Suction paths, 4 to 7: Supply paths, 8: Water supply port, 9: Water delivery port, 10: Chuck table, 10A: Porous member, 10a: Holding surface, 11: Rotation shaft, 12: Pipe, 13: Suction source, 14: Cover, 15, 16: Telescopic cover, 20: Grinding unit, 21: Holder, 22: Spindle motor, 23: Spindle, 24: Spindle mount, 25, 25X, 25Y, 25Z: Grinding wheels, 25A: Annular base, 25B: Pipe grindstone, 25a: Tapered surface, 25b: Vertical surface, 25c: Bottom surface, 26: Bolt, 27: Threaded hole, 30: Thickness measuring device, 31: First probe, 32: Second probe, 40: Lifting mechanism, 41: Lifting plate, 42: Guide rail, 43: Ball screw, 44: Servo motor, 45: Bracket, 50: Horizontal movement mechanism, 51: Slider, 52: Guide rail, 53: Ball screw, 54: Servo motor, 55: Bearing, 60: Grinding water supply unit, 61: Grinding water supply source, 62: Pipe, 100: Base, 100a: Opening of the base, 110: Column, 120: Inner base, CL: Center line of the pipe grindstone, D: Device, N: Vertical line, R: Resin (workpiece), S: Space, S1: Grinding water retention part, S11: Annular opening, T: Tape, V1, V2: On-off valves, W: Wafer, α: Tilt angle of the pipe grindstone

Claims

1. An annular base whose mounting surface is mounted on a spindle mount, a plurality of pipe grindstones annularly arranged on the opposite surface of the annular base opposite to the mounting surface, and a grinding water supply unit for supplying grinding water to the pipe grindstones. A grinding wheel for grinding a workpiece with the pipe grindstones, wherein the grinding water supply unit, a ring-shaped grinding water retention part formed between the mounting surface and the opposite surface of the annular base, a water supply hole opening to the mounting surface, a water delivery hole communicating the grinding water retention part with the inside of the pipe grindstone, and characterized in that it comprises the above.

2. The grinding wheel according to claim 1, wherein the grinding water retention part has a ring-shaped annular opening opening to the atmosphere on its inner peripheral surface.

3. A grinding method for grinding a workpiece with the pipe grindstones while supplying grinding water to the inside of the plurality of pipe grindstones of the grinding wheel according to claim 1, characterized in that the grinding water is temporarily stored in the grinding water retention part by the centrifugal force caused by the rotation of the grinding wheel, and the stored grinding water is supplied from the upper end of the pipe grindstone to the inside of the pipe grindstone while grinding the workpiece with the lower end of the pipe grindstone.

4. The grinding method according to claim 3, characterized in that the grinding water is supplied from the grinding water retention part to the inside of the pipe grindstone, and the grinding water overflowing from the grinding water retention part is supplied to the outer peripheral surface of the pipe grindstone.

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