Balancing method and grinding wheel

Abstract

To provide a new balance adjustment method whereby the balance of the weight of a grinding wheel can be adjusted.SOLUTION: A balance adjustment method used for adjusting a weight balance of a grinding wheel including an annular wheel base having an annular first surface in which a bottomed bolt fastening hole is open and a plurality of grinding stones arranged on a side opposite to the first surface of the wheel base, includes: a measurement step of measuring a deviation between a rotation axis passing through a central region of the first surface and a center of gravity of the grinding wheel; and an adjustment step of adjusting, after the measurement step, a position of the center of the gravity of the grinding wheel so as to cancel the deviation. In the adjustment step, the position of the center of the gravity of the grinding wheel is adjusted by attaching a weight to the bolt fastening hole, forming a recessed part open to the bottom of the bolt fastening hole, or attaching a weight to the recessed part open to the bottom of the bolt fastening hole.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a balance adjustment method used for adjusting the balance of the weight of a grinding wheel.

Background Art

[0002] In order to realize a small and lightweight device chip, there is an increasing opportunity to thinly process a disk-shaped wafer on which devices such as integrated circuits are provided on the surface side. For example, while holding the surface side of the wafer by a chuck table and rotating an annular grinding wheel to which a grinding stone containing abrasive grains is fixed and the chuck table relative to each other, and pressing the grinding stone against the back surface of the wafer while supplying a liquid such as pure water, the wafer is ground and thinned.

[0003] The above-described grinding wheel is attached, for example, by bolts or the like to a disk-shaped mount connected to a spindle serving as a rotation axis (see, for example, Patent Document 1). However, if the center of gravity of the grinding wheel is displaced from the rotation axis in a state where the grinding wheel is attached to the mount, the grinding wheel vibrates when the spindle is rotated, and the wafer is not properly ground. Therefore, before the grinding wheel is shipped, the balance of the weight of the grinding wheel is adjusted by shaving the side surface of the grinding wheel to provide a depression.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with the conventional balancing method described above, a recess is formed on the side of the grinding wheel, making it easy for grinding debris to accumulate in the recess. When debris accumulates in the recess, the weight balance of the grinding wheel deteriorates. In addition, the debris accumulated in the recess can fall during grinding, causing poor grinding of workpieces such as wafers, and contamination of the chuck table.

[0006] Therefore, the object of the present invention is to provide a new balancing method that can adjust the weight balance of a grinding wheel, and a grinding wheel whose weight balance has been adjusted by this balancing method. [Means for solving the problem]

[0007] According to one aspect of the present invention, a balancing method is provided for adjusting the weight balance of a grinding wheel, which includes an annular wheel base having an annular first surface with a bolt-fastening hole having a bottom, and a plurality of grinding wheels arranged on the opposite side of the wheel base from the first surface, the balancing method comprising: a measurement step of measuring the deviation between a rotation axis passing through a central region of the first surface and the center of gravity of the grinding wheel; and an adjustment step, after the measurement step, adjusting the position of the center of gravity of the grinding wheel to cancel out the deviation, wherein the adjustment step adjusts the position of the center of gravity of the grinding wheel by attaching a weight to the bolt-fastening hole, forming a recess opening at the bottom of the bolt-fastening hole, or attaching a weight to a recess opening at the bottom of the bolt-fastening hole.

[0008] Preferably, in the adjustment step, the weight is mounted in the recess opening at the bottom of the bolt hole, and the distance from the first surface to the bottom of the bolt hole is greater than the sum of the distance from the first surface to the deepest position reached by the bolt mounted in the bolt hole and the height of the weight.

[0009] Preferably, in the adjustment step, a weight is attached to the bolt fastening hole, and the distance from the first surface to the bottom of the bolt fastening hole is greater than the sum of the distance from the first surface to the deepest position that the bolt fitted into the bolt fastening hole can reach, and the height of the weight.

[0010] According to another aspect of the present invention, the present invention includes an annular wheel base having a first surface from which a bolt fastening hole with a bottom is opened, and a plurality of grinding wheels arranged on the opposite side of the first surface of the wheel base, wherein the bottom of the bolt fastening hole is Screw threads are provided on the inner wall surface. A grinding wheel with an open recess is provided. Preferably, a weight is fitted into the recess opening at the bottom of the bolt fastening hole.

[0011] According to yet another aspect of the present invention, the present invention includes an annular wheel base having a first surface from which a bolt fastening hole with a bottom is opened, and a plurality of grinding wheels arranged on the opposite side of the first surface of the wheel base, wherein a recess is opened at the bottom of the bolt fastening hole. A weight is fitted into the recess. A grinding wheel is provided. [Effects of the Invention]

[0012] In one aspect of the present invention, the balance of the grinding wheel's weight is adjusted by utilizing bolt fastening holes, which are fastened with bolts while mounted on the spindle and are not exposed to the outside. Specifically, the center of gravity of the grinding wheel is adjusted by attaching weights to the bolt fastening holes, forming recesses that open at the bottom of the bolt fastening holes, or attaching weights to recesses that open at the bottom of the bolt fastening holes. This prevents the accumulation of grinding debris in the recesses, unlike in conventional balancing methods where the formed recesses are exposed to the outside.

[0013] Therefore, the possibility of debris accumulating on the grinding wheel and worsening the weight balance of the grinding wheel can be kept to a minimum. In addition, the possibility of debris accumulated on the grinding wheel falling off during grinding and causing poor grinding of the workpiece or contamination of the chuck table can be kept to a minimum. Thus, according to one aspect of the present invention, a new balance adjustment method is provided that can adjust the weight balance of the grinding wheel. [Brief explanation of the drawing]

[0014] [Figure 1]FIG. 1 is a perspective view schematically showing a grinding device. [Figure 2] FIG. 2 is a perspective view schematically showing a grinding wheel. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a grinding wheel. [Figure 4] FIG. 4 is a cross-sectional view schematically showing a part of the grinding wheel fixed to a mount. [Figure 5] FIG. 5 is a cross-sectional view schematically showing a state where the position of the center of gravity of the grinding wheel is adjusted. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a part of the grinding wheel after the weight balance is adjusted. [Figure 7] FIG. 7 is a cross-sectional view schematically showing a part of the grinding wheel whose weight balance is adjusted by the balance adjustment method according to the first modification. [Figure 8] FIG. 8 is a cross-sectional view schematically showing a part of the grinding wheel after the weight balance is adjusted by the balance adjustment method according to the first modification. [Figure 9] FIG. 9 is a cross-sectional view schematically showing a part of the grinding wheel whose weight balance is adjusted by the balance adjustment method according to the second modification. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a state where the position of the center of gravity of the grinding wheel is adjusted. [Figure 11] FIG. 11 is a cross-sectional view schematically showing a part of the grinding wheel after the weight balance is adjusted by the balance adjustment method according to the second modification.

MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing a grinding device 2 used in the present embodiment. In FIG. 1, some elements constituting the grinding device 2 are represented by functional blocks. Further, the X-axis (first axis), Y-axis (second axis), and Z-axis (third axis) used in the following description are perpendicular to each other.

[0016] As shown in FIG. 1, the grinding apparatus 2 includes a base 4 that supports various elements constituting the grinding apparatus 2. An opening 4a that is long in a direction generally parallel to the X-axis (front-rear direction) is formed on the upper surface of the base 4. A ball screw type X-axis movement mechanism 6 is disposed in the opening 4a. The X-axis movement mechanism 6 includes a motor or the like (not shown) connected to a ball screw and a moving table (not shown), and moves the moving table back and forth along the X-axis.

[0017] Above the moving table is covered by a table cover 8. Also, bellows-shaped dust and splash-proof covers 10 that can expand and contract according to the movement of the moving table (table cover 8) are attached to the front and rear of the table cover 8. On the upper part of this moving table, a chuck table 12 configured to hold a plate-shaped workpiece 11 is disposed in a manner partially exposed from the table cover 8.

[0018] The workpiece 11 is, for example, a disk-shaped wafer made of a semiconductor material such as silicon. That is, the workpiece 11 has a circular surface 11a and a circular back surface 11b on the side opposite to the surface 11a. The surface 11a side of the workpiece 11 is partitioned into a plurality of small regions by a plurality of streets (lines to be divided) that intersect each other, and a device such as an integrated circuit (IC) is formed in each small region.

[0019] The grinding apparatus 2 of the present embodiment is used, for example, when grinding the back surface 11b side of the workpiece 11. When grinding the back surface 11b side of the workpiece 11, a protective member represented by a protective tape made of a material such as resin can be attached to the surface 11a side of the workpiece 11. By attaching the protective member to the surface 11a side of the workpiece 11, the impact applied to the surface 11a side during grinding of the back surface 11b side is alleviated, and the devices and the like of the workpiece 11 are protected.

[0020] Furthermore, in this embodiment, a disc-shaped wafer made of a semiconductor material such as silicon is used as the workpiece 11, but the material, shape, structure, size, etc. of the workpiece 11 are not limited to this embodiment. For example, substrates made of other semiconductors, ceramics, resins, metals, etc. can be used as the workpiece 11. Similarly, the type, quantity, shape, structure, size, arrangement, etc. of devices are not limited to the above embodiment. Devices do not need to be formed on the workpiece 11.

[0021] The chuck table 12 is connected to a rotational drive source (not shown), such as a motor, and rotates around a rotation axis parallel to the Z-axis, or a rotation axis slightly inclined with respect to the Z-axis. A portion of the upper surface 12a of the chuck table 12 is made of, for example, a porous material, and this portion of the upper surface 12a serves as a holding surface that holds the lower side of the workpiece 11. In other words, the chuck table 12 has a holding surface on its upper part for holding the workpiece 11.

[0022] The holding surface of the chuck table 12 is connected to a suction source (not shown), such as an ejector, which can generate negative pressure, via a suction passage (not shown) formed inside the chuck table 12. The workpiece 11, when placed on the chuck table 12, is sucked from the bottom by the negative pressure from the suction source acting on the holding surface. In this way, the chuck table 12 holds the workpiece 11 by sucking its bottom surface with the holding surface.

[0023] When the X-axis movement mechanism 6 described above moves the moving table back and forth along the X-axis, the chuck table 12 also moves back and forth along the X-axis. More specifically, the X-axis movement mechanism 6 moves the chuck table 12 between, for example, the loading / unloading area in front where the workpiece 11 is loaded into the chuck table 12, and the grinding area behind the loading / unloading area.

[0024] A columnar support structure 14 is provided behind the grinding area (i.e., behind the X-axis movement mechanism 6). A Z-axis movement mechanism 16 is positioned on the front side of the support structure 14. The Z-axis movement mechanism 16 is equipped with a pair of guide rails 18 that are long in a direction roughly parallel to the Z-axis (vertical direction), and a movable plate 20 is attached to this pair of guide rails 18 in a manner that allows it to slide.

[0025] A nut portion (not shown) that constitutes a ball screw is provided on the rear side of the movable plate 20, and a screw shaft 22, which is generally parallel to the Z axis, is connected to this nut portion in a manner that allows it to rotate. A motor 24 or the like is connected to one end of the screw shaft 22. By rotating the screw shaft 22 with the motor 24 or the like, the movable plate 20 moves up and down along the guide rail 18.

[0026] A support 26 is provided on the front of the movable plate 20. This support 26 supports a grinding unit 28 capable of grinding a workpiece 11 held by the chuck table 12 in the grinding area. The grinding unit 28 includes a spindle housing 30 fixed to the support 26. The spindle housing 30 houses a spindle 32 having a rotation axis parallel to the Z axis, or a rotation axis slightly inclined with respect to the Z axis, in a manner that allows it to rotate around its axis.

[0027] The lower end of the spindle 32 is exposed from the lower end surface of the spindle housing 30, and a disc-shaped mount 34 is fixed to this lower end of the spindle 32. For example, the outer edge of the mount 34 is provided with a number of holes (not shown) that penetrate the mount 34 in the direction of its thickness, and a bolt 36 is inserted into each hole.

[0028] The grinding wheel 38 is fixed to the lower surface of the mount 34 by the bolt 36 described above. In other words, the grinding wheel 38 is mounted on the spindle 32 via the mount 34, etc. The spindle housing 30 also houses a motor (not shown) connected to the upper end of the spindle 32. Power from this motor, etc., causes the grinding wheel 38 to rotate together with the spindle 32.

[0029] Figure 2 is a schematic perspective view of the grinding wheel 38, Figure 3 is a schematic cross-sectional view of the grinding wheel 38, and Figure 4 is a schematic cross-sectional view of a part of the grinding wheel 38 fixed to the mount 34. In Figure 4, for ease of explanation, some elements are represented by dashed lines.

[0030] As shown in Figures 2 and 3, the grinding wheel 38 includes an annular wheel base 40 made of a metal such as stainless steel or aluminum, with an outer diameter approximately the same as the diameter of the mount 34. The wheel base 40 has an annular upper surface (first surface) 40a that faces the lower surface of the mount 34 when attached to the mount 34, and an annular lower surface (second surface) 40b opposite to the upper surface 40a.

[0031] The edge of the upper surface 40a located on the outside of the grinding wheel 38 and the edge of the lower surface 40b located on the outside of the grinding wheel 38 are connected to each other by the outer surface 40c. Furthermore, the edge of the upper surface 40a located on the inside of the grinding wheel 38 and the edge of the lower surface 40b located on the inside of the grinding wheel 38 are connected to each other by the inner surface 40d. This inner surface 40d defines an opening that penetrates the wheel base 40 vertically.

[0032] An annular groove is opened on the lower surface 40b of the wheel base 40, and multiple grinding wheels 42, each containing abrasive grains such as diamond dispersed in a binder such as vitrified or resinoid, are arranged circumferentially in this groove. In other words, the multiple grinding wheels 42 are arranged on the lower surface 40b side of the wheel base 40. Each grinding wheel 42 is fixed to the wheel base 40 by adhesive or the like. The size of the abrasive grains and the type of binder are appropriately set according to the required quality of the workpiece 11 after grinding.

[0033] The wheel base 40 has a plurality (six in this embodiment) of bolt fastening holes 40e on its upper surface 40a, each having an open end and a bottom 40f (Figure 4) at the other end, spaced at approximately equal angles. The inner wall surface of each bolt fastening hole 40e is provided with threads corresponding to the threads of the bolt 36. The positions of each bolt fastening hole 40e correspond to the positions of the holes provided in the mount 34, and when fixing the grinding wheel 38 to the mount 34, the bolts 36 are fastened through the holes in the mount 34 to the corresponding bolt fastening holes 40e.

[0034] As shown in Figure 4, the distance d1 from the upper surface 40a of the wheel base 40 to the bottom 40f of the bolt fastening hole 40e is sufficiently larger than the distance d2 from the upper surface 40a of the wheel base 40 to the tip 36a of the bolt 36 when fastened in the bolt fastening hole 40e. That is, the distance d1 from the upper surface 40a to the bottom 40f is sufficiently larger than the distance d2 from the upper surface 40a to the deepest position that the bolt 36, when installed in the bolt fastening hole 40e, can reach. Therefore, when the grinding wheel 38 is fixed to the mount 34, the tip 36a of the bolt 36 does not come into contact with the bottom 40f of the bolt fastening hole 40e.

[0035] Below the grinding unit 28, a nozzle (not shown) is positioned to supply a liquid (grinding fluid) such as pure water to the part where the workpiece 11 and the grinding wheel 42 come into contact. Alternatively, or in conjunction with the nozzle, a liquid supply port may be provided on the grinding wheel 38 or the like for supplying the liquid.

[0036] Furthermore, a thickness measuring device 44 is provided next to the grinding area, which is used to measure the thickness of the workpiece 11 during grinding. The thickness measuring device 44 includes a first height gauge 46 that can measure the height of the upper surface 12a of the chuck table 12, and a second height gauge 48 that can measure the height of the upper surface of the workpiece 11 held on the chuck table 12. The difference between the measurement value of the first height gauge 46 and the measurement value of the second height gauge 48 is adopted as the thickness of the workpiece 11.

[0037] A controller (control unit) 50 is connected to each element of the grinding apparatus 2. This controller 50 is composed of a computer, for example, a processing unit 52 and a storage device 54, and controls the operation of each element of the grinding apparatus 2 described above so that the workpiece 11 is properly ground.

[0038] The processing unit 52 is typically a CPU (Central Processing Unit) and performs various processes necessary to control the elements described above. The storage device 54 includes, for example, a main memory such as DRAM (Dynamic Random Access Memory) and an auxiliary storage device such as a hard disk drive or flash memory. The functions of the controller 50 are realized, for example, by the operation of the processing unit 52 according to a program stored in the storage device 54.

[0039] An input device 56 is connected to the controller 50. The input device 56 is, for example, a touchscreen, which inputs commands from the operator to the controller 50. This touchscreen also serves as a display device that shows information output from the controller 50. A keyboard or mouse may also be used as the input device 56.

[0040] A portion of the storage device 54, which includes a non-temporary recording medium readable by a computer or the like, stores a program that causes the processing device 52 to execute a series of procedures necessary for grinding the workpiece 11. The processing device 52 performs various procedures necessary for grinding the workpiece 11 according to this program.

[0041] When grinding the workpiece 11, for example, the controller 50 moves the chuck table 12, which is holding the workpiece 11, from the discharge area to the grinding area. Then, the controller 50 rotates the chuck table 12 and the grinding wheel 38 relative to each other, and lowers the grinding unit 28 while supplying liquid from the nozzle. As a result, the grinding wheel 42 comes into contact with the upper surface of the workpiece 11 held in the chuck table 12, and the workpiece 11 is ground.

[0042] By the way, if the center of gravity of the grinding wheel 38, which is mounted on the mount 34 of the grinding device 2, is misaligned with the axis of rotation (more specifically, the axis of rotation of the spindle 32), the grinding wheel 38 will vibrate when the spindle 32 is rotated, and the workpiece 11 will not be properly ground. Therefore, in this embodiment, the weight balance of the grinding wheel 38 is adjusted by the following balance adjustment method.

[0043] In the balancing method according to this embodiment, first, the deviation between the rotation axis (the axis of the spindle 32) passing through the central region of the upper surface 40a of the grinding wheel 38 and the center of gravity of the grinding wheel 38 is measured (measurement step). For measuring this deviation, for example, three or more vibration sensors (not shown) are used, which are arranged at different positions along the circumferential direction of the mount 34. However, the specific method for measuring the deviation between the rotation axis and the center of gravity of the grinding wheel 38 is not limited to the method using such vibration sensors.

[0044] When measuring the deviation between the rotation axis and the center of gravity of the grinding wheel 38 using vibration sensors, first, information regarding the amplitude of vibration output by each vibration sensor is acquired while the spindle 32 is rotating at a predetermined speed. Then, based on the information regarding the amplitude of vibration output by each vibration sensor, the position (angle, direction) along the circumference of the grinding wheel 38 where the vibration amplitude is greatest, and the magnitude of the vibration amplitude at that position are identified.

[0045] The position identified in this way corresponds to the direction of the displacement of the center of gravity of the grinding wheel 38 relative to the rotation axis, and the magnitude of the amplitude at the identified position corresponds to the amount (distance) of the displacement of the center of gravity from the rotation axis. If there is no significant fluctuation in the amplitude of the vibration output by each vibration sensor while the spindle 32 is rotating, it is determined that there is no substantial displacement between the rotation axis and the center of gravity of the grinding wheel 38, and the following steps are omitted.

[0046] After measuring the discrepancy between the rotation axis and the center of gravity of the grinding wheel 38, the position of the center of gravity of the grinding wheel 38 is adjusted to cancel out this discrepancy (adjustment step). Figure 5 is a schematic cross-sectional view showing how the position of the center of gravity of the grinding wheel 38 is adjusted. As shown in Figure 5, in this embodiment, the position of the center of gravity of the grinding wheel 38 is adjusted by attaching a weight 58 to the bolt fastening hole 40e.

[0047] More specifically, the weight balance of the grinding wheel 38 is adjusted by selecting one or more bolt fastening holes 40e so as to cancel out the measured deviation of the center of gravity, and by attaching a weight 58 of appropriate weight to the selected bolt fastening holes 40e. The weight 58 is typically a grub screw (set screw) with a diameter corresponding to the bolt fastening hole 40e, and its outer surface has threads corresponding to the threads of the bolt fastening hole 40e.

[0048] Thus, when a grub screw is used as the weight 58, the weight 58 can be fastened and fixed to the bolt fastening hole 40e, so the problem of the weight 58 shifting position within the bolt fastening hole 40e does not occur. Of course, if the position of the weight 58 does not shift, a weight 58 without threads may be used.

[0049] Here, the distance from the upper end 58a to the lower end 58b of the weight 58, i.e., the height h1 of the weight 58, is set to be smaller than the value obtained by subtracting the distance d2 from the distance d1 mentioned above. In other words, the distance d1 from the upper surface 40a of the grinding wheel 38 to the bottom 40f of the bolt fastening hole 40e is greater than the sum of the distance d2 from the upper surface 40a to the deepest position reached by the bolt 36 installed in the bolt fastening hole 40e, and the height h1 of the weight 58.

[0050] Therefore, for example, if the weight 58 is positioned at a depth such that its lower end 58b contacts the bottom 40f of the bolt fastening hole 40e, the bolt 36 fastened to the bolt fastening hole 40e and the weight 58 will not interfere with each other. Figure 6 is a schematic cross-sectional view showing a part of the grinding wheel 38 after the weight balance has been adjusted. As shown in Figure 6, a predetermined gap is formed between the upper end 58a of the weight 58, which is positioned sufficiently deep in the bolt fastening hole 40e, and the tip 36a of the bolt 36.

[0051] As described above, in the balancing method of this embodiment, the weight balance of the grinding wheel 38 is adjusted by using the bolt fastening hole 40e, which is not exposed to the outside and is fastened with a bolt 36 while the grinding wheel 38 is mounted on the spindle 32. Specifically, by attaching a weight 58 to the bolt fastening hole 40e, the position of the center of gravity of the grinding wheel 38 is adjusted, so that, unlike conventional balancing methods in which the formed recess is exposed to the outside, grinding debris does not accumulate in the formed recess.

[0052] Therefore, the possibility of debris accumulating on the grinding wheel 38 and worsening the weight balance of the grinding wheel 38 can be kept to a minimum. In addition, the possibility of debris accumulated on the grinding wheel 38 falling off during grinding and causing poor grinding of the workpiece 11 or contamination of the chuck table 12 can be kept to a minimum. Thus, according to the balance adjustment method of this embodiment, the weight balance of the grinding wheel 38 is appropriately adjusted.

[0053] Next, the balance adjustment method according to the first modified example will be described. Figure 7 is a schematic cross-sectional view showing a part of the grinding wheel 38 whose weight balance is adjusted by the balance adjustment method according to the first modified example. The structure of the grinding wheel 38 according to the first modified example is the same as the structure of the grinding wheel 38 according to the embodiment described above, except for the part associated with the bolt fastening hole 40g. Therefore, the same reference numerals are used for the same elements as in the grinding wheel 38 according to the embodiment described above, and their detailed explanations are omitted below.

[0054] In the wheel base 40 of the grinding wheel 38 according to the first modified example, a plurality (six in this embodiment) of bolt fastening holes 40g are provided on the upper surface 40a, with one end open and the other end having a bottom 40h, at approximately equal angular intervals. The inner wall surface of each bolt fastening hole 40g is provided with threads corresponding to the threads of the bolt 36. Furthermore, the positions of each bolt fastening hole 40g correspond to the positions of the holes provided in the mount 34, and when fixing the grinding wheel 38 to the mount 34, the bolts 36 are fastened through the holes in the mount 34 to the corresponding bolt fastening holes 40g.

[0055] Here, the distance d3 from the upper surface 40a of the wheel base 40 to the bottom 40h of the bolt fastening hole 40g is approximately the same as, or slightly larger than, the distance d2 (Figure 4, etc.) from the upper surface 40a of the wheel base 40 to the tip 36a of the bolt 36 fastened in the bolt fastening hole 40g. In other words, in the first modified example, the distance d3 from the upper surface 40a to the bottom 40h is approximately the same as, or slightly larger than, the distance d2 from the upper surface 40a to the deepest position that the bolt 36 installed in the bolt fastening hole 40g can reach.

[0056] In the first modified balance adjustment method, the deviation between the rotation axis (axis of the spindle 32) passing through the central region of the upper surface 40a of the grinding wheel 38 and the center of gravity of the grinding wheel 38 is first measured (measurement step). This deviation is measured, for example, in the same procedure as the balance adjustment method according to the embodiment described above.

[0057] After measuring the discrepancy between the rotation axis and the center of gravity of the grinding wheel 38, the position of the center of gravity of the grinding wheel 38 is adjusted to cancel out this discrepancy (adjustment step). Figure 8 is a schematic cross-sectional view showing a part of the grinding wheel 38 after the weight balance has been adjusted using the balance adjustment method according to the first modified example. As shown in Figure 8, in the first modified example, the position of the center of gravity of the grinding wheel 38 is adjusted by forming a recess 40i that opens into the bottom 40h of the bolt fastening hole 40g.

[0058] More specifically, the weight balance of the grinding wheel 38 is adjusted by selecting one or more bolt fastening holes 40g so as to cancel out the measured deviation of the center of gravity, and then partially grinding off the bottom 40h of the selected bolt fastening holes 40g with a tool such as a drill to form a recess 40i of an appropriate size.

[0059] In this first modified balance adjustment method, the weight balance of the grinding wheel 38 is adjusted by utilizing the bolt fastening hole 40g, which is not exposed to the outside and is fastened with a bolt 36 while the grinding wheel 38 is mounted on the spindle 32. Specifically, the position of the center of gravity of the grinding wheel 38 is adjusted by forming a recess 40i that opens at the bottom 40h of the bolt fastening hole 40g. This prevents the accumulation of debris generated during grinding in the recess, unlike in conventional balance adjustment methods where the formed recess is exposed to the outside.

[0060] Therefore, the possibility of debris accumulating on the grinding wheel 38 and worsening the weight balance of the grinding wheel 38 can be kept to a minimum. In addition, the possibility of debris accumulated on the grinding wheel 38 falling off during grinding and causing poor grinding of the workpiece 11 or contamination of the chuck table 12 can be kept to a minimum. In this way, the weight balance of the grinding wheel 38 can also be appropriately adjusted by the first modified balance adjustment method.

[0061] Next, a balance adjustment method according to the second modified example will be described. Figure 9 is a schematic cross-sectional view showing a part of the grinding wheel 38 whose weight balance is adjusted by the balance adjustment method according to the second modified example. The structure of the grinding wheel 38 according to the second modified example is the same as the structure of the grinding wheel 38 according to the embodiment described above, except for the part associated with the bolt fastening hole 40j. Therefore, the same reference numerals are used for the same elements as in the grinding wheel 38 according to the embodiment described above, and their detailed explanations will be omitted below.

[0062] In the second modified example, the wheel base 40 of the grinding wheel 38 also has a plurality (six in this embodiment) of bolt fastening holes 40j on its upper surface 40a, each having an open end and a bottom 40k at the other end, spaced at approximately equal angles. The inner wall surface of each bolt fastening hole 40j is provided with threads corresponding to the threads of the bolt 36. Furthermore, the positions of each bolt fastening hole 40j correspond to the positions of the holes provided in the mount 34, and when fixing the grinding wheel 38 to the mount 34, the bolts 36 are fastened through the holes in the mount 34 to the corresponding bolt fastening holes 40j.

[0063] Here, the distance d4 from the upper surface 40a of the wheel base 40 to the bottom 40k of the bolt fastening hole 40j is approximately the same as, or greater than, the distance d2 (Figure 4, etc.) from the upper surface 40a of the wheel base 40 to the tip 36a of the bolt 36 fastened in the bolt fastening hole 40j. In other words, in the second modified example, the distance d4 from the upper surface 40a to the bottom 40k is approximately the same as, or greater than, the distance d2 from the upper surface 40a to the deepest position that the bolt 36 installed in the bolt fastening hole 40j can reach.

[0064] On the other hand, the grinding wheel 38 according to the second modified example is provided with a plurality of recesses 40l that open into the bottom 40k of each bolt fastening hole 40j. The diameter of the opening of each recess 40l is smaller than the diameter of the bolt fastening hole 40j. For example, screw threads are provided on the inner wall surface of each recess 40l.

[0065] In the second modified balance adjustment method, first, the deviation between the rotation axis (axis of the spindle 32) passing through the central region of the upper surface 40a of the grinding wheel 38 and the center of gravity of the grinding wheel 38 is measured (measurement step). This deviation is measured, for example, in the same procedure as the balance adjustment method according to the embodiment described above.

[0066] After measuring the discrepancy between the rotation axis and the center of gravity of the grinding wheel 38, the position of the center of gravity of the grinding wheel 38 is adjusted to cancel out this discrepancy (adjustment step). Figure 10 is a schematic cross-sectional view showing how the position of the center of gravity of the grinding wheel 38 is adjusted. As shown in Figure 10, in the second modified example, the position of the center of gravity of the grinding wheel 38 is adjusted by attaching a weight 60 to a recess 40l that opens at the bottom 40k of the bolt fastening hole 40j.

[0067] More specifically, the weight balance of the grinding wheel 38 is adjusted by selecting one or more bolt fastening holes 40j so as to cancel out the measured deviation of the center of gravity, and by attaching a weight 60 of appropriate weight to a recess 40l that opens at the bottom 40k of the selected bolt fastening hole 40j. The weight 60 is typically a grub screw (set screw) with a diameter corresponding to the recess 40l, and its outer surface has threads corresponding to the threads of the recess 40l.

[0068] Thus, when a grub screw is used as the weight 60, the weight 60 can be fastened and fixed to the recess 40l, so the problem of the weight 60 shifting position within the recess 40l does not occur. Of course, if the position of the weight 60 does not shift, a weight 60 without threads may be used.

[0069] Here, the distance from the upper end 60a to the lower end 60b of the weight 60, i.e., the height h2 of the weight 60, is typically greater than the depth of the recess 40l (the distance from the bottom 40k of the bolt fastening hole 40j to the bottom of the recess 40l). In this case, by positioning the weight 60 at a depth such that the lower end 60b of the weight 60 contacts the bottom of the recess 40l, interference between the bolt 36 fastened in the bolt fastening hole 40j and the weight 60 placed in the recess 40l is avoided. Figure 11 is a schematic cross-sectional view showing a part of the grinding wheel 38 after the weight balance has been adjusted using the balance adjustment method according to the second modified example.

[0070] Furthermore, in this second modified example, it is desirable that the distance d4 from the top surface 40a to the bottom 40k of the bolt fastening hole 40j is greater than the sum of the distance d2 from the top surface 40a to the deepest position that the bolt 36 fitted into the bolt fastening hole 40j can reach, and the height h2 of the weight 60. In this case, the bolt fastening hole 40j becomes sufficiently deep, so even if the upper end 60a of the weight 60 is positioned above the bottom 40k of the bolt fastening hole 40j, the bolt 36 fastened into the bolt fastening hole 40j and the weight 60 will not interfere with each other.

[0071] In this second modified balance adjustment method, the weight balance of the grinding wheel 38 is adjusted by utilizing the bolt fastening hole 40j, which is not exposed to the outside and to which the bolt 36 is fastened while the grinding wheel 38 is mounted on the spindle 32. Specifically, the position of the center of gravity of the grinding wheel 38 is adjusted by attaching a weight 60 to a recess 40l that opens at the bottom 40k of the bolt fastening hole 40j. This prevents the accumulation of debris generated during grinding in the recess, unlike in conventional balance adjustment methods where the formed recess is exposed to the outside.

[0072] Therefore, the possibility of debris accumulating on the grinding wheel 38 and worsening the weight balance of the grinding wheel 38 can be kept to a minimum. In addition, the possibility of debris accumulated on the grinding wheel 38 falling off during grinding and causing poor grinding of the workpiece 11 or contamination of the chuck table 12 can be kept to a minimum. In this way, the weight balance of the grinding wheel 38 can also be appropriately adjusted by the second modified balance adjustment method.

[0073] It should be noted that the present invention is not limited to the embodiments described above and can be implemented with various modifications. For example, in the balance adjustment methods according to the embodiments and each of the modifications described above, a grinding wheel having six bolt fastening holes is used, but the grinding wheel only needs to have three or more bolt fastening holes.

[0074] Furthermore, the structures, methods, etc., of the embodiments and modifications described above may be modified as appropriate, as long as they do not deviate from the scope of the present invention. [Explanation of Symbols]

[0075] 2: Grinding equipment 4: Base 4a: Opening 6:X-axis movement mechanism 8: Table cover 10: Dustproof and splashproof cover 12: Chuck Table 12a:Top surface 14:Support structure 16:Z-axis movement mechanism 18: Guide rail 20: Mobile Plate 22: Screw shaft 24: Motor 26: Support 28: Grinding Unit 30: Spindle housing 32: Spindle 34: Mount 36: Bolt 36a: Tip 38: Grinding Wheel 40: Wheel base 40a:Top surface (first surface) 40b: Bottom surface (second surface) 40c: Outer surface 40d: Inner surface 40e: Bolt fastening hole 40f: bottom 40g: Bolt fastening hole 40h: bottom 40i: recessed 40j: Bolt fastening hole 40k :bottom 40L: recess 42: Grinding Wheel 44: Thickness measuring instrument 46: First height gauge 48: Second height gauge 50: Controller (control unit) 52: Processing Unit 54: Storage device 56: Input device 58: Hammer 58a: Upper end 58b: Lower end 60: Hammer 60a: upper end 60b: Lower end 11: Workpiece 11a: Surface 11b: Inside

Claims

1. A balancing method used for adjusting the weight balance of a grinding wheel, comprising an annular wheel base having an annular first surface with a bolt fastening hole with a bottom, and a plurality of grinding wheels arranged on the opposite side of the first surface of the wheel base, A measurement step of measuring the deviation between the rotation axis passing through the central region of the first surface and the center of gravity of the grinding wheel, The measurement step is followed by an adjustment step of adjusting the position of the center of gravity of the grinding wheel to counteract the misalignment, A balancing method for adjusting the center of gravity of a grinding wheel, wherein the adjustment step involves attaching a weight to the bolt fastening hole, forming a recess opening at the bottom of the bolt fastening hole, or attaching a weight to a recess opening at the bottom of the bolt fastening hole.

2. In the adjustment step, the weight is attached to the recess that opens at the bottom of the bolt fastening hole, The balance adjustment method according to claim 1, wherein the distance from the first surface to the bottom of the bolt fastening hole is greater than the sum of the distance from the first surface to the deepest position reached by the bolt installed in the bolt fastening hole and the height of the weight.

3. In this adjustment step, a weight is attached to the bolt fastening hole, The balance adjustment method according to claim 1, wherein the distance from the first surface to the bottom of the bolt fastening hole is greater than the sum of the distance from the first surface to the deepest position reached by the bolt installed in the bolt fastening hole and the height of the weight.

4. An annular wheel base having a first surface with a bolt fastening hole with a bottom, The wheel base includes a plurality of grinding wheels arranged on the side opposite to the first surface, A grinding wheel having a recess with threads on its inner wall opening at the bottom of the bolt fastening hole.

5. The grinding wheel according to claim 4, wherein a weight is fitted into the recess opening at the bottom of the bolt fastening hole.

6. An annular wheel base having a first surface from which bolt fastening holes with a bottom are opened, The wheel base includes a plurality of grinding wheels arranged on the side opposite to the first surface, A grinding wheel having a recess opening at the bottom of the bolt fastening hole, into which a weight is fitted.

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