Grinding wheels

Abstract

To suppress a load current value of a rotary driving source from increasing when a blade thickness becomes smaller due to ablation of a grinding stone.SOLUTION: A grinding wheel, which grinds a work-piece, includes an annular wheel base and a first grinding stone provided on one annular surface of the wheel base. The first grinding stone has a first attachment surface facing the annular one surface of the wheel base and a first grinding surface that contacts the work-piece, in which is formed a first groove exposed onto the first attachment surface, where the first groove is not exposed onto the first grinding surface before the first grinding stone is abraded and is exposed onto the first grinding surface when the first grinding stone is abraded beginning with the first grinding surface side. Preferably, a width of the first groove becomes smaller as going from the first attachment surface toward a bottom. Preferably, the grinding wheel further includes a second grinding stone, where a second groove, exposed to a second attachment surface, whose depth is different from a depth of the first groove is formed in the second grinding stone.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a grinding wheel that is mounted on a grinding device that grinds workpieces such as semiconductor wafers, and that includes a grinding stone that comes into contact with the workpiece to grind it. [Background technology]

[0002] Device chips to be mounted on electronic devices are formed, for example, by dividing a disk-shaped semiconductor wafer. Individual device chips can be produced by setting multiple dividing lines that intersect with each other on the surface of the semiconductor wafer, forming devices such as ICs in each area defined by the dividing lines, and dividing the semiconductor wafer along the dividing lines.

[0003] In recent years, there has been a remarkable trend toward miniaturization of electronic devices, and there has also been an increasing demand for smaller and thinner device chips mounted on electronic devices. Therefore, in order to manufacture thin device chips, the semiconductor wafer is ground by a grinding device before being divided, and the semiconductor wafer is thinned to a predetermined thickness.

[0004] The grinding device includes a chuck table capable of holding a semiconductor wafer and a grinding wheel arranged above the chuck table so as to be movable up and down. The grinding wheel includes grinding stones arranged in an annular shape on its underside facing the upper surface of the chuck table. The grinding stones are formed by dispersing abrasive grains, such as diamond, in a binder.

[0005] When grinding a semiconductor wafer with a grinding device, the semiconductor wafer is fixed on a chuck table, and the chuck table is rotated around an axis perpendicular to the upper surface of the chuck table, and the grinding wheel is also rotated in the same manner, and the grinding wheel is then lowered.

[0006] Then, the grinding wheel moving on the circular track comes into contact with the semiconductor wafer. Abrasive grains are exposed from the binder at the contact surface (grinding surface) of the grinding wheel that comes into contact with the semiconductor wafer, and the semiconductor wafer is ground when the exposed abrasive grains come into contact with the semiconductor wafer. When grinding a workpiece with a grinding device, grinding water made of pure water or the like is supplied to the grinding surface of the workpiece. The grinding water removes processing debris and heat generated by grinding (see, for example, Patent Document 1 and Patent Document 2).

[0007] In a grinding machine, the load current value of a rotary drive source, such as a motor that rotates a grinding wheel, is monitored to quickly detect any abnormalities that may occur during grinding. While the grinding machine is smoothly grinding a workpiece, this load current value remains stable within an allowable range without significant fluctuations. However, if an abnormality occurs in the grinding machine, the load current value may fluctuate drastically or exceed the allowable range. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-209080 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-124690 Summary of the Invention [Problem to be solved by the invention]

[0009] When a workpiece is ground using a grinding machine, the grinding wheel wears out and the cutting edge thickness gradually decreases. It has been confirmed that, even if no abnormalities occur in the grinding machine, the load current value of the rotary drive source that rotates the grinding wheel tends to gradually increase. Therefore, as the grinding machine grinds multiple workpieces one after another, the load current value increases and exceeds the allowable range, increasing the possibility of false detection of an abnormality.

[0010] In recent years, with the diversification of device chips and other products formed from workpieces, high-rigidity workpieces are often ground using grinding machines. Because the load current value of the rotary drive source tends to be high when grinding high-rigidity workpieces, the load current value of the rotary drive source tends to fall outside the allowable range when the grinding wheel wears and the load current value of the rotary drive source increases. While this problem could be solved by, for example, changing the allowable range of the load current value, this creates another problem: it becomes difficult to detect abnormalities when they occur in the grinding machine.

[0011] The present invention has been made in consideration of such problems, and its purpose is to provide a grinding wheel in which the increase in the load current value of the rotary drive source is suppressed when the grinding stone wears and the cutting edge thickness becomes smaller. [Means for solving the problem]

[0012] According to one aspect of the present invention, a grinding wheel for grinding a workpiece includes an annular wheel base and a first grinding stone provided on one annular surface of the wheel base, the first grinding stone having a first mounting surface facing the annular surface of the wheel base and a first grinding surface that contacts the workpiece, and a first groove exposed on the first mounting surface is formed, the first groove not being exposed on the first grinding surface before the first grinding stone is worn, and the first groove being exposed on the first grinding surface when the first grinding stone is worn from the first grinding surface side. From the bottom A grinding wheel is provided that is characterized by an exposed surface.

[0013] Preferably, the width of the first groove narrows from the first mounting surface to the bottom.

[0014] Preferably, the wheel base further includes a second grinding wheel provided on the annular surface of the wheel base, the second grinding wheel having a second mounting surface facing the annular surface of the wheel base and a second grinding surface in contact with the workpiece, and a second groove exposed to the second mounting surface and having a depth different from that of the first groove is formed thereon, the second groove not being exposed to the second grinding surface before the second grinding wheel is worn out, and being exposed to the second grinding surface when the second grinding wheel is worn out from the second grinding surface side. From the bottom To be exposed.

[0015] More preferably, the first grinding wheel has a third groove formed thereon that is exposed to the first mounting surface, and the third groove is not exposed to the first grinding surface before the first grinding wheel is worn out, and when the first grinding wheel is worn out from the first grinding surface side, the third groove is exposed to the first grinding surface. From the bottom To be exposed. [Effects of the Invention]

[0016] A grinding wheel according to one aspect of the present invention includes an annular wheel base and a first grinding stone mounted on one annular surface of the wheel base. The first grinding stone has a first mounting surface facing the annular surface of the wheel base and a first grinding surface that contacts a workpiece. The first grinding stone has a first groove formed therein and exposed on the first mounting surface. Before the grinding wheel is used, the first groove of the first grinding stone is not exposed on the first grinding surface.

[0017] When this grinding wheel is used to grind successive workpieces, the first grinding wheel wears out from the first grinding surface side, gradually reducing the cutting edge thickness. The bottom of the first groove is then worn away, exposing the first groove on the first grinding surface. At this time, the area of ​​the first grinding surface of the first grinding wheel is reduced by the size of the first groove. As the area of ​​the first grinding surface of the first grinding wheel that contacts the workpiece surface decreases, the load current value of the rotary drive source that rotates the grinding wheel also decreases.

[0018] Therefore, the load current value of the rotary drive source increases as the first grinding wheel wears and the cutting edge thickness decreases, but decreases as the area of ​​the first grinding surface of the first grinding wheel decreases. In other words, the increase in the load current value of the rotary drive source is suppressed, and appropriate detection of abnormalities in the grinding device based on the load current value is not hindered.

[0019] Therefore, the present invention provides a grinding wheel in which the increase in the load current value of the rotary drive source when the grinding stone is worn and the cutting edge thickness becomes smaller is suppressed. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 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(A) is a cross-sectional view that schematically shows a grinding wheel, and FIG. 3(B) is a cross-sectional view that schematically shows a grinding wheel whose grinding stone has been worn out. [Figure 4] FIG. 4(A) is a cross-sectional view schematically showing a grinding wheel according to one example, FIG. 4(B) is a cross-sectional view schematically showing a grinding wheel according to another example, and FIG. 4(C) is a cross-sectional view schematically showing a grinding wheel according to yet another example. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described with reference to the drawings. A grinding wheel according to this embodiment is mounted on a grinding device that grinds a workpiece when used. FIG. 1 is a perspective view that schematically shows a grinding device 2. FIG. 1 also schematically shows a partial configuration of the grinding device 2, a grinding wheel 16 according to this embodiment, and a workpiece 1 to be ground. First, the workpiece 1 to be ground by the grinding wheel 16 will be described.

[0022] The workpiece 1 is a wafer made of, for example, Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor material, or a wafer made of a composite oxide such as LT (lithium tantalate) or LN (lithium niobate).

[0023] Alternatively, the workpiece 1 may be a substantially disk-shaped substrate made of a material such as sapphire, glass, or quartz. Examples of the glass include alkali glass, alkali-free glass, soda-lime glass, lead glass, borosilicate glass, and quartz glass. Alternatively, the workpiece 1 may be a package substrate formed by arranging multiple device chips vertically and horizontally and sealing them with resin. The following description will be given taking the case where the workpiece 1 is a semiconductor wafer as an example, but the workpiece 1 is not limited to this.

[0024] The surface 1a of the workpiece 1 is partitioned by a plurality of planned division lines (not shown) that intersect with each other. Devices (not shown), such as ICs and LSIs, are formed in each of the areas partitioned by the planned division lines on the surface 1a of the workpiece 1. There are no restrictions on the type, number, or arrangement of the devices. By dividing the workpiece 1 along the planned division lines, individual device chips each containing a device can be formed. By first grinding the workpiece 1 from the back surface 1b side to thin it, thin device chips can finally be formed.

[0025] Next, we will explain the grinding device 2 that grinds the workpiece 1. The grinding device 2 includes a chuck table 4 that holds the workpiece 1 by suction, and a grinding unit 8 that grinds the workpiece 1 held on the chuck table 4. A grinding wheel 16 according to this embodiment is attached to the grinding unit 8.

[0026] In the grinding device 2, the back surface 1b of the workpiece 1 is ground in a state where the back surface 1b is exposed upward. In order to protect the front surface 1a when the workpiece 1 is ground, a tape-like protective member 3 is attached to the front surface 1a of the workpiece 1 in advance.

[0027] The chuck table 4 has a suction passage (not shown) inside, one end of which is connected to a suction source (not shown), and the other end of which is connected to a holding surface 6, which is the upper surface of the chuck table 4. When the workpiece 1 is placed on the holding surface 6, the chuck table 4 can suck and hold the workpiece 1 by activating the suction source and applying negative pressure through the holding surface 6. The chuck table 4 is rotatable around a table rotation axis that is perpendicular to the holding surface 6. The table rotation axis, for example, passes through the center of the holding surface 6 in the vertical direction.

[0028] In the grinding apparatus 2, the grinding unit 8 moves up and down above the chuck table 4. The grinding unit 8 includes a spindle 10 extending vertically and a rotary drive source (not shown) such as a motor connected to the upper end of the spindle 10. A disk-shaped wheel mount 12 is disposed at the lower end of the spindle 10, and a grinding wheel 16 is fixed to the underside of the wheel mount 12. When the rotary drive source connected to the spindle 10 is operated, the grinding wheel 16 rotates together with the spindle 10.

[0029] Fig. 2 is a perspective view schematically showing a grinding wheel 16 according to this embodiment, and Fig. 3(A) is a cross-sectional view schematically showing the grinding wheel 16 according to this embodiment. The grinding wheel 16 includes an annular wheel base 18 made of a metal material such as aluminum, and a plurality of grinding stones 20 provided on one annular surface 18b of the wheel base 18. In order to facilitate understanding of the cross-sectional view shown in Fig. 3(A), the abrasive grains of the grinding stones 20 and part of the side surface of the grinding stones 20 that is exposed in the gaps between the grinding stones 20 are omitted.

[0030] 3(A), an accommodating recess 18d for accommodating the grinding wheel 20 is formed along the annular surface 18b of the wheel base 18. The grinding wheel 20 has an attachment surface 20a facing the annular surface 18b of the wheel base 18, and a grinding surface 20b that comes into contact with the workpiece 1.

[0031] The grinding wheels 20 are embedded in the storage recesses 18d from the mounting surface 20a side via an adhesive and are mounted on the wheel base 18. The portions of the grinding wheels 20 exposed from the storage recesses 18d come into contact with the workpiece 1 from the grinding surface 20b side and grind the workpiece 1.

[0032] 2, the wheel base 18 has an upper surface 18a opposite to the annular surface 18b provided with fastening holes 18c that are threadedly fitted with fasteners 14, such as bolts. The wheel mount 12 of the grinding unit 8 has through holes formed in an arrangement that corresponds to the arrangement of the fastening holes 18c of the wheel base 18. When the fasteners 14 are passed through the through holes and tightened into the fastening holes 18c of the wheel base 18, the grinding wheel 16 can be fixed to the wheel mount 12, as shown in FIG.

[0033] The grinding wheel 20 is formed by mixing abrasive grains such as diamond or cBN (cubic boron nitride) with a binder such as vitrified or resinoid, and then sintering the mixture. When a rotational drive source such as a spindle motor is operated to rotate the spindle 10 and the grinding wheel 16, the grinding wheel 20 rotates on a circular orbit.

[0034] When grinding the workpiece 1 with the grinding unit 8, first, the spindle 10 is rotated to move the grinding wheel 20 along the circular orbit, and the chuck table 4 is rotated around the table rotation axis that is approximately perpendicular to the holding surface 6. Then, the grinding unit 8 is lowered and the grinding wheel 20 is brought into contact with the back surface 1b of the workpiece 1 held on the chuck table 4, whereby the workpiece 1 is ground from the back surface 1b side.

[0035] The grinding device 2 is provided with a thickness measuring device (not shown) near the chuck table 4 that measures the thickness of the workpiece 1 to be ground by the grinding unit 8. This thickness measuring device calculates the thickness of the workpiece 1, for example, from the difference between the height of the back surface 1b of the workpiece 1 and the height of the holding surface 6 of the chuck table 4. The grinding device 2 grinds the workpiece 1 by lowering the grinding unit 8 until the workpiece 1 reaches a predetermined thickness, while referring to the thickness of the workpiece 1 measured by the thickness measuring device.

[0036] In the grinding device 2, in order to quickly detect any abnormality that occurs during grinding, the load current value of the rotary drive source that rotates the spindle 10 to rotate the grinding wheel 16 is monitored. That is, the grinding device 2 is provided with an ammeter (not shown) that measures the load current value of the rotary drive source.

[0037] While the grinding of the workpiece 1 proceeds smoothly in the grinding device 2, the load current value of the rotary drive source does not fluctuate significantly and remains stable within an allowable range. On the other hand, if some abnormality occurs in the grinding device 2, the load current value may fluctuate drastically or may not fall within the allowable range. Therefore, by monitoring the load current value of the rotary drive source, abnormalities occurring in the grinding device 2 can be detected early.

[0038] Incidentally, when the workpiece 1 is ground by the grinding device 2, the grinding wheel 20 is worn and the cutting edge thickness gradually decreases. More specifically, the length of the portion of the grinding wheel 20 exposed from the housing recess 18d of the wheel base 18, i.e., the distance from the grinding surface 20b of the grinding wheel 20 to the housing recess 18d, becomes shorter.

[0039] When the grinding unit 8 is lowered while rotating the grinding wheel 16, and the grinding surface 20b of the grinding wheel 20 comes into contact with the back surface 1b of the workpiece 1, vibrations are generated due to the processing load. This vibration is absorbed by the grinding wheel 20 in an amount that depends on the rigidity of the grinding wheel 20. In other words, the vibration weakens depending on the rigidity of the grinding wheel 20. Therefore, the load current value of the rotary drive source that rotates the grinding wheel 16 when the workpiece 1 is ground depends on the rigidity of the grinding wheel 20.

[0040] From another perspective, this vibration is absorbed by the grinding wheel 20 in an amount that depends on the shape of the grinding wheel 20. The degree to which the shape of the grinding wheel 20 absorbs the vibration caused by the processing load is determined by the ratio between the blade thickness of the grinding wheel 20 and the area of ​​the grinding surface 20b.

[0041] More specifically, when comparing two grinding wheels 20 that differ only in blade thickness, the grinding wheel 20 with a larger blade thickness is more likely to absorb this vibration than the grinding wheel 20 with a smaller blade thickness. As a result, the intensity of the vibration is relatively small in the grinding wheel 20 with a larger blade thickness. Furthermore, when comparing two grinding wheels 20 that differ only in the area of ​​the grinding surface 20b, the grinding wheel 20 with a smaller grinding surface 20b is more likely to absorb this vibration than the grinding wheel 20 with a larger grinding surface 20b. As a result, the intensity of the vibration is relatively small in the grinding wheel 20 with a smaller grinding surface 20b.

[0042] As the grinding wheel 20 wears, the cutting edge thickness of the grinding wheel 20 decreases and the rigidity of the grinding wheel 20 increases. This makes it difficult for the grinding wheel 20 to absorb vibrations caused by the processing load. As the amount of vibration suppression by the grinding wheel 20 gradually decreases, it has been confirmed that the load current value of the rotary drive source that rotates the grinding wheel 16 tends to gradually increase as the grinding wheel 20 wears.

[0043] Therefore, when the grinding device 2 grinds multiple workpieces 1 one after another, the load current value rises and exceeds the allowable range, and the possibility of false detection of an abnormality even when no abnormality has occurred gradually increases.

[0044] In recent years, with the diversification of device chips and the like formed from workpieces 1, high-rigidity workpieces 1 are often ground by grinding devices 2. When grinding high-rigidity workpieces 1, the load current value of the rotary drive source tends to be high, and when the grinding wheel 20 wears out and the load current value of the rotary drive source increases, the load current value is particularly likely to fall outside the allowable range. In other words, when high-rigidity workpieces 1 are ground one after another, the possibility of false detection of an abnormality increases even more.

[0045] To solve this problem of false detection of abnormalities, it is conceivable to change the allowable range set for the load current value of the rotary drive source, for example. However, in this case, another problem arises in that it becomes difficult to detect an abnormality when it actually occurs in the grinding device 2.

[0046] Therefore, the grinding wheel 16 according to this embodiment is structurally designed to suppress the increase in the load current value of the rotary drive source due to wear of the grinding wheel 20. Below, the grinding wheel 16 will be described, focusing on the configuration that suppresses the increase in the load current value of the rotary drive source.

[0047] 1, 2, and 3(A), the grinding stone 20 of the grinding wheel 16 according to this embodiment has a groove 22 formed on the mounting surface 20a. The groove 22 is formed so as to penetrate the grinding stone 20 from the side surface on the outer periphery to the side surface on the inner periphery, for example.

[0048] However, the grooves 22 are not limited to this, and may be exposed on only one of the outer peripheral side surface and the inner peripheral side surface of the grinding wheel 20, or on neither. Also, the grooves 22 may be exposed on one or both of the side surface on the front side in the direction of travel of the grinding wheel 20 when the grinding wheel 16 is rotated and the side surface on the rear side in the direction of travel of the grinding wheel 20. In other words, the grooves 22 may be formed in the grinding wheel 20 along a circular orbit that serves as the path of travel of the grinding wheel 20.

[0049] The depth of the groove 22 from the mounting surface 20a is set so that the bottom 22a of the groove 22 reaches the portion of the grinding wheel 20 that is exposed from the accommodation recess 18d when the grinding wheel 20 is accommodated in the accommodation recess 18d of the wheel base 18. However, when the grinding wheel 20 is in an unused state, the bottom 22a of the groove 22 must not reach the grinding surface 20b, which is the bottom surface of the grinding wheel 20. In other words, the groove 22 is not exposed to the grinding surface 20b before the grinding wheel 20 is worn out.

[0050] As the grinding wheel 16 is used, the grinding stone 20 is worn from the grinding surface 20b side, and the cutting edge thickness of the grinding stone 20 gradually decreases. Accordingly, the load current value of the rotary drive source that rotates the grinding wheel 16 gradually increases.

[0051] The grinding wheel 20 is then worn from the grinding surface 20b side, and when the wear has progressed to a predetermined extent, the grooves 22 are exposed on the grinding surface 20b. FIG. 3(B) is a cross-sectional view schematically showing a grinding wheel 16 used to grind multiple workpieces 1. FIG. 3(B) schematically shows the grinding wheel 20 with the grooves 22 exposed on the grinding surface 20b side. In the cross-sectional view shown in FIG. 3(B), the abrasive grains of the grinding wheel 20 and some of the side surfaces of the grinding wheel 20 are omitted to make the drawing easier to understand.

[0052] When the grooves 22 are exposed on the grinding surface 20b, the area of ​​the grinding surface 20b decreases, and the ratio between the blade thickness of the grinding wheel 20 and the area of ​​the grinding surface 20b changes. In other words, the grinding wheel 20 can more easily absorb vibrations caused by the processing load. From another perspective, when the grooves 22 are exposed on the grinding surface 20b, the contact area of ​​the grinding wheel 20 with the workpiece 1 decreases, and the processing load itself caused by grinding decreases.

[0053] This reduces the load current value of the rotary drive source, which had increased due to the reduction in the blade thickness of the grinding wheel 20. In other words, the reduction in the area of ​​the grinding surface 20b offsets the increase in the load current value caused by the reduction in the blade thickness of the grinding wheel 20.

[0054] Now, let us consider another aspect. The grinding wheel 20, which moves along the circular orbit, contacts one end of the back surface 1b of the workpiece 1, grinds the workpiece 1 while moving over the back surface 1b, and then proceeds out of the workpiece 1 from the other end of the back surface 1b of the workpiece 1. During this process, when the grinding wheel 20 comes into contact with one end of the back surface 1b of the workpiece 1, the end of the grinding wheel 20 on the grinding surface 20b on the front side in the traveling direction (hereinafter referred to as the edge of the grinding wheel 20) collides with the workpiece 1, and the grinding wheel 20 is worn out more than at other times.

[0055] When the grooves 22 are formed from the outer peripheral side surface of the grinding wheel 20 to the inner peripheral side surface, when the grooves 22 are exposed on the grinding surface 20b, in addition to the existing edge portions of the grinding wheel 20, new edge portions of the grinding wheel 20 are generated at the lower ends of the grooves 22. In other words, the number of edge portions of the grinding wheel 20 increases in the grinding wheel 16.

[0056] Therefore, after the grooves 22 are exposed on the grinding surface 20b, the amount of wear of the grinding wheel 20 increases. At this time, the wear of the grinding wheel 20 consumes more of the processing load generated by grinding the workpiece 1, and the load current value of the rotation drive source decreases.

[0057] When the grooves 22 are exposed on the grinding surface 20b due to these factors, the load current value of the rotary drive source decreases. Therefore, when the grinding wheel 16 is used in this embodiment, the increase in the load current value that accompanies a decrease in the cutting thickness of the grinding wheel 20 is suppressed, preventing erroneous detection of an abnormality based on the load current value. In other words, when the grinding wheel 16 is used in this embodiment, the accuracy of detecting an abnormality in the grinding device 2 does not decrease, and when an abnormality occurs in the grinding device 2, the abnormality can be more appropriately detected.

[0058] For example, when the distance from the accommodation recess 18d to the grinding surface 20b of the grinding wheel 20 is the blade thickness of the grinding wheel 20, the bottom 22a of the groove 22 is preferably located at a height position that is 40% to 70% of the blade thickness above the grinding surface 20b. In particular, the bottom 22a of the groove 22 is preferably located at a height position that is 45% or more of the blade thickness above the grinding surface 20b, more preferably at a height position that is 50% or more of the blade thickness above the grinding surface 20b, and most preferably at a height position that is about 60% of the blade thickness above the grinding surface 20b.

[0059] If the distance between the bottom 22a of the groove 22 and the grinding surface 20b is less than 40% of the blade thickness, that is, if the groove 22 is too deep, it is difficult to ensure the strength required for the grinding wheel 20. In addition, there is little need to expose the groove 22 to the grinding surface 20b while the increase in the load current value of the rotational drive source of the grinding wheel 16 is small.

[0060] On the other hand, if the distance between the bottom 22a of the groove 22 and the grinding surface 20b is greater than 70% of the blade thickness, i.e., if the groove 22 is too shallow, the effect of reducing the load current value of the rotary drive source is not fully realized. In other words, even if the load current value of the rotary drive source increases and the need to suppress this increases, the groove 22 is not exposed to the grinding surface 20b, and the state in which the load current value increases continues for a long time.

[0061] A specific example will be described. For example, the thickness of the portion of the grinding wheel 20 exposed from the accommodation recess 18d of the grinding wheel 16, i.e., the blade thickness, is set to 7 mm. In this case, the bottom of the groove 22 should be positioned at a height that is 4 mm higher than the grinding surface 20b. However, the thickness of the grinding wheel 20, the blade thickness of the grinding wheel 20, and the height position of the bottom of the groove 22 are not limited to this example.

[0062] Furthermore, when the grooves 22 are formed on both the inner and outer peripheral side surfaces of the grinding wheel 20, the length of the grooves 22 in the front-to-rear direction of the annular orbit of the grinding wheel 20, i.e., the width of the grooves 22, is preferably 5% to 20% of the length of the grinding wheel 20 in the front-to-rear direction of the annular orbit. In particular, the width of the grooves 22 is preferably 7.5% to 15% of the length of the grinding wheel 20, and most preferably about 10% of the length of the grinding wheel 20.

[0063] More specifically, when the length of the grinding wheel 20 in the front-to-rear direction of the annular track is 20 mm, the width of the groove 22 exposed on the mounting surface 20a of the grinding wheel 20 is preferably 3 mm. However, the length of the grinding wheel 20 and the width of the groove 22 are not limited to this example.

[0064] In the grinding wheel 16 according to this embodiment, the shape of the grooves 22 may be the same for all of the multiple grinding wheels 20 mounted on the wheel base 18. That is, the depth and width of the grooves 22 may be the same for all of the multiple grinding wheels 20. Conversely, the shapes of the grooves 22, such as the depth and width, may not be the same for all of the multiple grinding wheels 20. The grinding wheel 16 may include multiple types of grinding wheels 20 with grooves 22 of different shapes.

[0065] Fig. 4(A) is a cross-sectional view schematically showing a grinding wheel 24 equipped with a plurality of types of grinding stones each having a different groove shape. In order to make the cross-sectional view shown in Fig. 4(A) easier to understand, the abrasive grains of each grinding stone and some of the side surfaces of the grinding stones are omitted.

[0066] An upper surface 26a of the wheel base 26 of the grinding wheel 24 faces the wheel mount 12 of the grinding unit 8 of the grinding device 2. An annular surface 26b opposite to the upper surface 26a of the wheel base 26 is formed with an accommodating recess 26d for accommodating each grinding wheel. An attachment surface 28a of each grinding wheel faces the annular surface 26b of the wheel base 26 inside the accommodating recess 26d.

[0067] 4(A) includes nine types of grinding stones, two of each type, each with a different groove depth. That is, the grinding wheel 24 includes a total of 18 grinding stones. The grinding stones of the same type are arranged in a point-symmetric (rotationally symmetric) pattern on the annular surface 26b of the wheel base 26.

[0068] The cross-sectional view shown in Figure 4(A) depicts a pair of first grinding wheels 28, 46 having first grooves 48a, 48j of the same depth, as well as one each of other grinding wheels of different types.

[0069] More specifically, the cross-sectional view shown in FIG. 4(A) depicts the second grinding wheel 30 having the second groove 48b formed therein, the third grinding wheel 32 having the third groove 48c formed therein, the fourth grinding wheel 34 having the fourth groove 48d formed therein, the fifth grinding wheel 36 having the fifth groove 48e formed therein, the sixth grinding wheel 38 having the sixth groove 48f formed therein, the seventh grinding wheel 40 having the seventh groove 48g formed therein, the eighth grinding wheel 42 having the eighth groove 48h formed therein, and the ninth grinding wheel 44 having the ninth groove 48i formed therein.

[0070] 4(A), the first grooves 48a and 48j, the second groove 48b, the third groove 48c, the fourth groove 48d, the fifth groove 48e, the sixth groove 48f, the seventh groove 48g, the eighth groove 48h, and the ninth groove 48i become shallower in this order. In this case, as the grinding wheel 24 continues to grind the workpiece 1, each groove is successively exposed on the grinding surface 28b in this order as the grinding stone wears.

[0071] For example, in the grinding wheel 16 shown in FIG. 3(A), in which the depths of the grooves 22 of each grinding wheel 20 are uniform, all of the grooves 22 are exposed to the grinding surface 20b almost simultaneously as each grinding wheel 20 wears. In this case, the reduction in the load current value of the rotary drive source increases sharply over a short period of time. On the other hand, in the grinding wheel 24 shown in FIG. 4(A), the reduction in the load current value of the rotary drive source increases gradually over a long period of time. Therefore, the transition in the load current value becomes more stable, with smaller fluctuations.

[0072] 4(A), the total area of ​​the grinding surfaces 28b of the grinding stones changes gradually, so the grinding environment of the workpiece 1 also changes gradually. Therefore, sudden changes in the processing results are unlikely to occur.

[0073] Although the grooves 22 formed in the grinding wheel 20 have not been described so far as having a shape in which the width varies with height, the grooves 22 of the grinding wheel 20 according to this embodiment may have a shape in which the width varies with height. For example, the width of the grooves 22 narrows from the mounting surface 20a toward the bottom.

[0074] More specifically, as in the grinding wheel 50 shown in Fig. 4(B), the grooves 56 may be V-shaped when viewed from the side of the grinding wheel 54. In the cross-sectional view shown in Fig. 4(B), the abrasive grains of the grinding wheel 54 and part of the side surface of the grinding wheel 54 are omitted to make the drawing easier to understand.

[0075] 4(B) faces the wheel mount 12 of the grinding unit 8 of the grinding device 2. An annular surface 52b of the wheel base 52 opposite the upper surface 52a is formed with an accommodating recess 52d for accommodating each grinding wheel 54. The mounting surface 54a of each grinding wheel 54 faces the annular surface 52b of the wheel base 52 inside the accommodating recess 52d.

[0076] As the grinding wheel 50 grinds a plurality of workpieces 1 one after another, the grinding stone 54 wears out from the grinding surface 54b side, and the load current value of the rotary drive source that rotates the grinding wheel 50 gradually increases. As the grinding stone 54 wears out, the V-shaped groove 56 becomes exposed on the grinding surface 54b side. At this time, the width of the groove 56 on the grinding surface 54b is extremely small, so the reduction in the load current value of the rotary drive source is small.

[0077] As wear of the grinding wheel 54 progresses further, it is expected that the load current value of the rotary drive source will further increase. However, the width of the grooves 56 on the grinding surface 54b will also gradually increase, and the area of ​​the grinding surface 54b of the grinding wheel 54 will gradually decrease, so the effect of reducing the load current value of the rotary drive source will gradually increase. As a result, even if wear of the grinding wheel 54 progresses further, the change in the load current value of the rotary drive source will become smaller, and no significant change will occur in the machining environment of the workpiece 1.

[0078] While the above description has been given of the case where the number of grooves 22, 56 formed in each grinding wheel 20, 54 is one, the number of grooves 22, 56 in each grinding wheel 20, 54 is not limited to this. For example, as in the grinding wheel 58 shown in Fig. 4(C), each grinding wheel 62 may have a plurality of grooves 64. In the cross-sectional view shown in Fig. 4(C), the abrasive grains of the grinding wheel 62 and some of the side surfaces of the grinding wheel 62 are omitted to make the drawing easier to understand.

[0079] 4(C) faces the wheel mount 12 of the grinding unit 8 of the grinding device 2. An annular surface 60b of the wheel base 60 opposite the upper surface 60a is formed with an accommodating recess 60d for accommodating each grinding wheel 62. The mounting surface 62a of each grinding wheel 62 faces the annular surface 60b of the wheel base 60 inside the accommodating recess 60d.

[0080] When multiple grooves 64 are formed in the grinding wheel 62, as the grinding wheel 62 wears out, the multiple grooves 64 become exposed on the grinding surface 62b, and new edge portions of the grinding wheel 62 are generated at the bottom end of each groove 64 in a number more than twice the number of edge portions of the grinding wheel 62 that existed up until then. In other words, the number of edge portions of the grinding wheel 62 increases dramatically in the grinding wheel 58.

[0081] Therefore, after the grooves 64 are exposed on the grinding surface 62b, the amount of wear of the grinding wheel 62 increases dramatically. At this time, the wear of the grinding wheel 62 consumes even more of the processing load generated by grinding the workpiece 1, and the load current value of the rotation drive source drops significantly.

[0082] Note that, for the grinding wheels 16, 24, 50, 58 according to this embodiment, modified examples of the grooves 22, 56, 64 of the grinding stones 20, 54, 62 have been described, but these modified examples may be combined with each other. The grinding wheels according to this embodiment may have multiple grooves in the grinding stones, and the depths of the grooves may not be uniform, and the grooves may be V-shaped. The grinding wheels according to this embodiment will be summarized below to cover the basic example and each modified example described above. The above description can be referenced as appropriate for the general description below.

[0083] The grinding wheels 16, 24, 50, 58 according to this embodiment include wheel bases 18, 26, 52, 60 and first grinding wheels 20, 28, 54, 62. The first grinding wheels 20, 28, 54, 62 have first mounting surfaces 20a, 28a, 54a, 62a and first grinding surfaces 20b, 28b, 54b, 62b that contact the workpiece 1. The first grinding wheels 20, 28, 54, 62 have first grooves 22, 48a, 56, 64 that are exposed on the first mounting surfaces 20a, 28a, 54a, 62a.

[0084] 3(A) and 3(B), the first grooves 22, 48a, 56, 64 are not exposed to the first grinding surfaces 20b, 28b, 54b, 62b before the first grinding wheels 20, 28, 54, 62 are worn. The first grooves 22, 48a, 56, 64 are exposed to the first grinding surfaces 20b, 28b, 54b, 62b when the first grinding wheels 20, 28, 54, 62 are worn from the first grinding surfaces 20b, 28b, 54b, 62b side.

[0085] 4(B), in the grinding wheel 50 according to this embodiment, the width of the first groove 56 of the first grinding stone 54 may be narrowed from the first mounting surface 54a toward the bottom. In other words, the first groove 56 may be V-shaped.

[0086] 4(A), the grinding wheel 24 according to this embodiment may further include a second grinding wheel 30 having a configuration different from that of the first grinding wheel 28. The second grinding wheel 30 has a second mounting surface (the upper surface of the second grinding wheel 30) and a second grinding surface (the lower surface of the second grinding wheel 30) that comes into contact with the workpiece 1.

[0087] The second grinding wheel 30 has a second groove 48b formed therein that is exposed on the second mounting surface. The depth of the second groove 48b is different from the depth of the first groove 48a of the first grinding wheel 28. The second groove 48b is not exposed on the second grinding surface before the second grinding wheel 30 is worn, and is exposed on the second grinding surface when the second grinding wheel 30 is worn from the second grinding surface side. The timing when the first groove 48a is exposed on the first grinding surface 28b of the first grinding wheel 28 does not coincide with the timing when the second groove 48b is exposed on the second grinding surface of the second grinding wheel 30.

[0088] 4(C), in the grinding wheel 58 according to this embodiment, one first grinding wheel 62 may have a groove 64 in addition to the first groove 64. In other words, a third groove 64 exposed on the first mounting surface 62a may be formed. The third groove 64 is not exposed on the first grinding surface 62b before the first grinding wheel 62 is worn. Then, when the first grinding wheel 62 is worn from the first grinding surface 62b side, the third groove 64 is exposed on the first grinding surface 62b. The first groove 64 and the third groove 64 may be exposed on the first grinding surface 62b at approximately the same time.

[0089] As explained above, in the grinding wheel according to this embodiment, when the grinding stone wears, the grooves become exposed on the grinding surface side of the grinding stone, reducing the area of ​​the grinding surface and increasing the edge portion of the grinding stone. As a result, the increase in the load current value due to wear of the grinding stone is suppressed for the rotary drive source that rotates the spindle to rotate the grinding wheel.

[0090] The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above-described embodiment, the grooves 22, 48a, 56, and 64 are formed in the grinding stones 20, 28, 54, and 62 of the grinding wheels 16, 24, 50, and 58. However, it is not necessary that the grooves 22, 48a, 56, and 64 are formed in all of the grinding stones 20, 28, 54, and 62 of the grinding wheels 16, 24, 50, and 58.

[0091] For example, the grooves 22, 48a, 56, 64 may not be formed in some of the grinding stones 20, 28, 54, 62 of the grinding wheels 16, 24, 50, 58. As long as the grooves 22, 48a, 56, 64 are formed in at least one of the grinding stones 20, 28, 54, 62, an increase in the load current value due to wear of the grinding stones 20, 28, 54, 62 is suppressed.

[0092] The ratio of the grinding stones 20, 28, 54, 62 in which the grooves 22, 48a, 56, 64 are formed to all the grinding stones 20, 28, 54, 62 in the grinding wheels 16, 24, 50, 58 can be selected appropriately depending on the type of workpiece 1, the processing conditions, etc. In addition, the shapes of the grooves 22, 48a, 56, 64, such as their depth and width, can also be selected appropriately depending on the application of the grinding wheels 16, 24, 50, 58.

[0093] The structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0094] 1 Workpiece 1a surface 1b back side 3 Protective materials 2 Grinding equipment 4 Chuck table 6 Holding surface 8 Grinding Unit 10 spindles 12 Wheel mount 14 Fixtures 16, 24, 50, 58 grinding wheels 18,26,52,60 Wheel base 18a,26a,52a,60a Top surface 18b,26b,52b,60b one side 18c fastening hole 18d, 26d, 52d, 60d Recessed portion 20,28,30,32,34,36,38,40,42,44,46,54,62 Grinding wheels 20a, 28a, 54a, 62a Mounting surface 20b, 28b, 54b, 62b grinding surface 22,48a,48b,48c,48d,48e,48f,48g,48h,48i,48j,56,64 groove 22a bottom

Claims

1. A grinding wheel for grinding a workpiece, A circular wheel base; a first grinding wheel provided on one annular surface of the wheel base; the first grinding wheel has a first mounting surface facing the annular surface of the wheel base and a first grinding surface that contacts the workpiece, and a first groove that is exposed on the first mounting surface; A grinding wheel characterized in that the first groove is not exposed on the first grinding surface before the first grinding wheel is worn out, and is exposed on the first grinding surface from its bottom side when the first grinding wheel is worn out from the first grinding surface side.

2. 2. The grinding wheel of claim 1, wherein the width of the first groove narrows from the first mounting surface to the bottom.

3. a second grinding wheel provided on one surface of the annular portion of the wheel base; the second grinding wheel has a second mounting surface facing the annular surface of the wheel base and a second grinding surface that contacts the workpiece, and a second groove is formed on the second mounting surface and has a depth different from that of the first groove; A grinding wheel as described in claim 1 or claim 2, characterized in that the second groove is not exposed on the second grinding surface before the second grinding wheel is worn, and is exposed on the second grinding surface from its bottom side when the second grinding wheel is worn from the second grinding surface side.

4. the first grinding wheel has a third groove formed therein and exposed on the first mounting surface; A grinding wheel as described in claim 1 or claim 2, characterized in that the third groove is not exposed on the first grinding surface before the first grinding wheel is worn, and is exposed on the first grinding surface from its bottom side when the first grinding wheel is worn from the first grinding surface side.

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