JP7158813B2 - grinding wheel - Google Patents

Description

The present invention relates to grinding wheels used for grinding workpieces.

Each device is included by dividing a plate-shaped workpiece represented by a semiconductor wafer on which devices such as IC (Integrated Circuit) and LSI (Large Scale Integration) are formed along dividing lines (street). A plurality of device chips are obtained. This device chip is built in various electronic devices, and in recent years, along with the miniaturization and thinning of electronic devices, the device chip is also required to be small and thin. Therefore, a method of thinning the workpiece by grinding it with a grinding wheel is used.

A grinding apparatus that includes a chuck table that holds the workpiece and a grinding unit that grinds the workpiece held by the chuck table is used for grinding the workpiece. The grinding unit of the grinding machine has a wheel mount fixed to the tip of a spindle that serves as a rotating shaft, and a grinding wheel equipped with a grinding wheel for grinding the workpiece is attached to the wheel mount ( For example, see Patent Document 1). The workpiece is ground by bringing the grinding surface of the grinding wheel into contact with the workpiece while rotating the grinding wheel.

JP-A-2000-288881

When a workpiece is ground with a grinding wheel, frictional heat is generated due to contact between the grinding surface of the grinding wheel and the workpiece, and this frictional heat tends to wear out the grinding wheel. In addition, when debris (grinding debris) generated by the grinding process enters between the grinding surface of the grinding wheel and the workpiece, the grinding wheel may be scraped by the grinding debris and worn out.

Therefore, grinding is generally performed while supplying a liquid (grinding fluid) to the grinding wheel. This grinding fluid cools the grinding wheel and washes away grinding dust. However, since the entire grinding surface of the grinding wheel contacts the workpiece during grinding, it is difficult to supply the grinding liquid between the grinding surface and the workpiece. As a result, the cooling of the grinding wheel and the discharge of the grinding dust become insufficient, resulting in the problem that the grinding wheel tends to wear out.

The present invention has been made in view of such problems, and an object of the present invention is to provide a grinding wheel capable of suppressing consumption of the grinding wheel.

According to one aspect of the present invention, there is provided a grinding wheel for grinding a workpiece with a grinding surface of a grinding wheel, comprising a base and a plurality of grinding wheels arranged in a ring on the base. A grinding wheel is provided on the grinding surface side of the grinding wheel, in which a plurality of concave portions serving as channels for the grinding fluid are formed so as to be exposed on the side surface of the grinding wheel , and the length of the grinding wheel and the A grinding wheel is provided that has different widths and the recesses are formed along the longitudinal direction of the grinding wheel and not along the direction perpendicular to the longitudinal direction of the grinding wheel.

In one aspect of the present invention, the recess may have a depth of 10 μm or more and a width of 120 μm or more. In one aspect of the present invention, the recess may have a depth of 1 mm or more.

A grinding wheel according to an aspect of the present invention includes a grinding wheel having recesses formed on the surface to be ground, and a grinding fluid is supplied between the surface to be ground and the workpiece through the recesses during grinding. configured as As a result, it is possible to suppress consumption of the grinding wheel caused by frictional heat due to contact between the grinding wheel and the workpiece or residual grinding dust generated by grinding.

It is a perspective view which shows a grinding apparatus. 1 is a perspective view of a grinding wheel; FIG. It is a perspective view which shows the structural example of a grinding wheel. It is a perspective view which shows the structural example of a grinding wheel. It is a perspective view which shows the structural example of a grinding wheel. 4 is a graph showing the relationship between the number of processed wafers and the amount of wear of a grinding wheel.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing a configuration example of a grinding device 2 to which a grinding wheel according to this embodiment is attached. The grinding device 2 grinds a plate-like workpiece, typically a semiconductor wafer on which devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integrations) are formed, with a grinding wheel.

The grinding device 2 includes a base 4 on which each component of the grinding device 2 is mounted, and a rectangular parallelepiped support structure 6 is provided at the rear end of the base 4 . An opening 4a is formed in the upper surface of the base 4 along the X-axis direction (front-rear direction).

A ball-screw type X-axis moving mechanism 8 and a dust/splash proof cover 10 covering a part of the X-axis moving mechanism 8 are arranged inside the opening 4a. The X-axis moving mechanism 8 has an X-axis moving table 8a, and moves this X-axis moving table 8a in the X-axis direction. Further, in front of the opening 4a, an operation panel 12 for inputting grinding processing conditions and the like is installed.

A chuck table 14 for holding a workpiece is provided on the X-axis moving table 8a, and a part of the upper surface of the chuck table 14 constitutes a suction surface 14a for sucking the workpiece. Note that FIG. 1 shows an example in which the chuck table 14 and the suction surface 14a are formed in a circular shape when viewed from above, assuming that a disk-shaped workpiece is held. It can be changed as appropriate according to the shape of the workpiece held by the chuck table 14 .

The suction surface 14 a is formed in a porous shape by porous ceramics or the like, and is connected to a suction source (not shown) through a suction path (not shown) formed inside the chuck table 14 . The workpiece is sucked and held by the chuck table 14 by applying the negative pressure of the suction source to the suction surface 14a while the workpiece is placed in contact with the suction surface 14a.

The chuck table 14 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the Z-axis direction (vertical direction). Also, the chuck table 14 moves in the X-axis direction together with the X-axis moving table 8a. Movement of the chuck table 14 is controlled by the X-axis movement mechanism 8 .

A Z-axis movement mechanism 16 is provided on the front side of the support structure 6 . The Z-axis moving mechanism 16 has a pair of Z-axis guide rails 18 arranged so that the longitudinal direction thereof extends along the Z-axis direction. It is mounted in a slidable manner along the direction. A nut portion (not shown) is provided on the rear surface side (rear surface side) of the Z-axis moving plate 20, and the Z-axis ball screw is arranged along a direction substantially parallel to the Z-axis guide rail 18 in this nut portion. 22 are screwed together.

A Z-axis pulse motor 24 is connected to one end of the Z-axis ball screw 22 . When the Z-axis ball screw 22 is rotated by the Z-axis pulse motor 24, the Z-axis moving plate 20 moves along the Z-axis guide rail 18 in the Z-axis direction.

A support 26 projecting forward is provided on the front side (front side) of the Z-axis movement plate 20 . The support 26 supports a grinding unit 28 for grinding the workpiece. The grinding unit 28 includes a spindle housing 30 fixed to the support 26, and a spindle 32 serving as a rotation shaft is rotatably accommodated in the spindle housing 30. As shown in FIG.

A tip (lower end) of the spindle 32 is exposed to the outside of the spindle housing 30 , and a disk-shaped wheel mount 34 is fixed to the tip of the spindle 32 . A disk-shaped grinding wheel 36 having approximately the same diameter as the wheel mount 34 is attached to the lower surface of the wheel mount 34 .

When grinding the workpiece, the chuck table 14 is sucked and held, and the X-axis moving mechanism 8 moves the chuck table 14 to position the chuck table 14 under the grinding wheel 36 . Then, while rotating the chuck table 14 and the spindle 32 in predetermined directions at a predetermined number of revolutions, the grinding wheel 36 is lowered at a predetermined speed to bring the grinding wheel 36 into contact with the workpiece. As a result, the grinding wheel 36 processes (grinds) the workpiece so as to scrape off a portion of the workpiece, thereby thinning the workpiece.

FIG. 2 is a perspective view showing a configuration example of the grinding wheel 36 according to this embodiment. The grinding wheel 36 has an annular base 40 made of a metal material such as stainless steel or aluminum.

The base 40 has a first surface (fixed end surface) 40a that is fixed to the wheel mount 34, and a second surface (free end surface) 40b that is arranged substantially parallel to the first surface and is not fixed to the wheel mount 34. Further, in the central portion of the base 40, an opening 40c having a truncated cone shape that penetrates the base 40 from the first surface 40a to the second surface 40b and whose diameter increases from the first surface 40a toward the second surface 40b. is formed.

An annular groove 40 d surrounding the opening 40 c is formed along the outer periphery of the base 40 on the second surface 40 b side of the base 40 . A plurality of rectangular parallelepiped grinding wheels 42 are arranged in a ring inside the groove 40d. The plurality of grinding wheels 42 are fixed at approximately equal intervals so that their longitudinal directions (longitudinal directions) extend along the circumferential direction of the base 40 .

The grinding wheel 42 is formed, for example, by fixing abrasive grains made of diamond, CBN (Cubic Boron Nitride) or the like with a bonding material such as metal bond, resin bond or vitrified bond. However, the material, shape, structure, size, etc. of the grinding wheel 42 are not limited. Also, any number of grinding wheels 42 can be fixed to the base 40 .

A grinding wheel 42 fixed to the base 40 has a rectangular grinding surface 42 a exposed on the side opposite to the base 40 . The ground surface 42a is a surface that comes into contact with the workpiece during grinding, and the workpiece is ground by the ground surface 42a.

The material, shape, structure, size, etc. of the workpiece to be ground by the grinding wheel 42 are not limited. For example, wafers made of materials such as semiconductors (silicon, GaAs, InP, GaN, SiC, etc.), glass, ceramics, resins, and metals can be used as workpieces. Further, the conditions such as the materials of the bonding material and the abrasive grains constituting the grinding wheel 42 can be appropriately selected according to the material of the workpiece.

Further, the base 40 is formed with a plurality of grinding liquid supply ports 40e penetrating through the base 40 from the first surface 40a toward the second surface 40b. The grinding liquid supply ports 40e are arranged so as to open at approximately equal intervals in a region of the second surface 40b located between the opening 40c and the groove 40d. When grinding the workpiece with the grinding wheel 42, a grinding liquid such as pure water is supplied to the grinding wheel 42 through the grinding liquid supply port 40e. There is no limit to the number of grinding fluid supply ports 40e.

Grinding wheel 36 is mounted on a wheel mount 34 fixed to the distal end of spindle 32 (see FIG. 1). The grinding wheel 36 is mounted, for example, by positioning the grinding wheel 36 so that the first surface 40a is in contact with the lower surface side of the wheel mount 34, and fixing the wheel mount 34 and the grinding wheel 36 using bolts or the like. .

Rotating the spindle 32 with the grinding wheel 36 mounted on the wheel mount 34 causes the grinding wheel 36 to rotate. The grinding surface 42a of the grinding wheel 42 provided on the rotating grinding wheel 36 is pressed against the grinding surface of the workpiece held by the chuck table 14, thereby grinding the workpiece.

When grinding the workpiece with the grinding wheel 42, a grinding liquid such as pure water is supplied to the grinding wheel 42 through the grinding liquid supply port 40e. However, since the entire grinding surface 42a of the grinding wheel 42 is in contact with the workpiece during grinding, it is difficult to supply the grinding fluid to the grinding surface 42a.

If the supply of the grinding liquid to the grinding surface 42a is insufficient, the grinding wheel 42 will be insufficiently cooled. As a result, the temperature of the grinding wheel 42 tends to rise due to the frictional heat generated by the friction between the grinding surface 42a and the workpiece, and the grinding wheel is quickly worn out.

Also, during the grinding process, debris (grinding debris) generated by grinding may enter between the grinding surface 42a of the grinding wheel 42 and the workpiece. At this time, if sufficient grinding fluid is not supplied to the grinding surface 42a, the grinding chips are likely to remain without being discharged. If the grinding process is performed while the grinding dust remains between the grinding surface 42a and the workpiece, the grinding dust may scrape the binding material of the grinding wheel 42, resulting in wear of the grinding wheel.

The grinding wheel 36 according to this embodiment includes a grinding wheel 42 having a recessed portion on the grinding surface 42a side. When the grinding liquid is supplied to the vicinity of the grinding wheel 42 during grinding, the concave portion formed on the side of the grinding surface 42a serves as a channel for the grinding liquid, and the grinding liquid is easily supplied to the entire grinding surface 42a. As a result, it is possible to suppress consumption of the grinding wheel due to frictional heat or residual grinding dust. Details of the grinding wheel 42 having recesses formed in the grinding surface 42a will be described below.

FIG. 3 is a perspective view showing a configuration example of the grinding wheel 42. As shown in FIG. The grinding wheel 42 is formed, for example, in a rectangular parallelepiped shape with different lengths and widths, and includes a grinding surface 42a and a mounting surface 42b that is substantially parallel to the grinding surface 42a and fixed to the base 40 (see FIG. 2).

The grinding surface 42a and the mounting surface 42b are respectively composed of side surfaces 42c and 42d arranged parallel to each other along the longitudinal direction (longitudinal direction) of the grinding wheel 42 and a direction perpendicular to the longitudinal direction of the grinding wheel 42 ( width direction) are connected to the side surfaces 42e and 42f arranged parallel to each other. However, the shape of the grinding wheel 42 is not limited as long as it can be fixed to the base 40 and has a grinding surface 42a that contacts the workpiece.

A plurality of recesses 42g are formed on the grinding surface 42a side of the grinding wheel 42 from the side surface 42e to the side surface 42f. Each of the plurality of concave portions 42g is linearly formed along the longitudinal direction of the grinding wheel 42 and is exposed on the side surfaces 42e and 42f. The plurality of recesses 42g are arranged at predetermined intervals along the direction perpendicular to the longitudinal direction of the grinding wheel 42 so as to be generally parallel to each other.

The recess 42g is formed so that its depth is less than the thickness of the grinding wheel 42 (the distance from the ground surface 42a to the mounting surface 42b). A region defined by the plurality of recesses 42g, that is, a region on the side of the grinding surface 42a of the grinding wheel 42 where the recesses 42g are not formed constitutes a grinding region 42h for grinding the workpiece.

The method of forming the recess 42g in the grinding wheel 42 is not limited. For example, to form the recess 42g, a chuck table capable of holding the grinding wheel 42 and a spindle equipped with an annular cutting blade formed by fixing abrasive grains such as diamond with a binding material such as metal are used. A cutting device provided can be used. With the grinding wheel 42 held by the chuck table, the cutting blade is rotated to cut into the grinding surface 42a of the grinding wheel 42, thereby forming a recess 42g corresponding to the shape of the cutting blade.

When performing the grinding process, the grinding wheel 36 to which the grinding wheel 42 is fixed is mounted on the wheel mount 34 (see FIG. 1), and the workpiece is held by the chuck table 14 . Then, the grinding wheel 36 and the chuck table are rotated, and the grinding surface 42a is brought into contact with the workpiece while supplying the grinding liquid around the grinding wheel 42 through the grinding liquid supply port 40e. At this time, since the recesses 42g are exposed on the side surfaces 42e and 42f of the grinding wheel 42, the grinding fluid supplied to the periphery of the grinding wheel 42 flows into the recesses 42g, and the grinding fluid is supplied to the inside of the grinding surface 42a. be done.

The grinding wheel 42 is fixed so that its longitudinal direction extends along the circumferential direction of the base 40 (see FIG. 2). Therefore, when the grinding wheel 42 shown in FIG. A grinding wheel 36 is obtained. By using the grinding wheel 36, the grinding fluid supplied from the grinding fluid supply port 40e to the gap between the adjacent grinding wheels 42 can be efficiently taken into the grinding surface 42a.

The number of the recesses 42g, the depth of the recesses 42g, the width of the recesses 42g, and the width of the grinding region 42h (interval between the recesses 42g) are determined by various factors such as the amount of grinding liquid supplied, the material of the workpiece, the material of the grinding wheel 42, and the like. It can be appropriately set in consideration of processing conditions. For example, it is preferable that the depth of the recess 42g is 10 μm or more and the width of the recess 42g is 120 μm or more so that the grinding fluid can flow smoothly inside the recess 42g. Also, the width of the grinding region 42h corresponding to the interval between the adjacent recesses 42g can be appropriately set.

If the grinding of the workpiece by the grinding wheel 42 is continued, the grinding surface 42a side of the grinding wheel 42 is worn and the depth of the concave portion 42g gradually decreases. Therefore, in order to sufficiently supply the grinding fluid to the grinding surface 42a even when the grinding wheel 42 is worn, it is preferable to form the recess 42g deeper. For example, the depth of the recess 42g can be 1 mm or more, more preferably 4 mm or more.

Although FIG. 3 shows the grinding wheel 42 in which a plurality of recesses are formed from the side surface 42e to the side surface 42f, the shape of the recesses is not limited to this. FIG. 4 is a perspective view showing another configuration example of the grinding wheel 42. As shown in FIG.

A plurality of recesses 42i extending from the side surface 42c to the side surface 42d are formed on the grinding surface 42a side of the grinding wheel 42 shown in FIG. Each of the plurality of recesses 42i is linearly formed along a direction perpendicular to the longitudinal direction of the grinding wheel 42, and is exposed on the side surfaces 42c and 42d. The plurality of recesses 42i are arranged at predetermined intervals along the longitudinal direction of the grinding wheel 42 so as to be substantially parallel to each other. A region defined by the plurality of recesses 42i constitutes a grinding region 42j for grinding the workpiece.

When the grinding wheel 42 formed with the recess 42i is fixed to the base 40 (see FIG. 2), the side 42c or the side 42d of the grinding wheel 42 faces the opening 40c of the base 40, and the recess 42i faces the base 40. are arranged along the radial direction of Therefore, when the grinding wheel 36 is rotated, the grinding fluid supplied radially outwardly of the base 40 from the grinding fluid supply port 40e by centrifugal force can be efficiently taken into the grinding surface 42a. can be done.

The number, depth and width of the recesses 42i can be appropriately set similarly to the recesses 42g (see FIG. 3). Also, the width of the grinding region 42j corresponding to the interval between adjacent recesses 42i can be set as appropriate.

3 and 4 show the grinding wheel 42 having a plurality of recesses formed along one direction, the grinding wheel 42 may be formed with a plurality of recesses intersecting each other. FIG. 5 is a perspective view showing another configuration example of the grinding wheel 42. As shown in FIG.

A plurality of recesses 42k extending from a side surface 42c to a side surface 42d and a plurality of recesses 42m extending from a side surface 42e to a side surface 42f are formed on the grinding surface 42a side of the grinding wheel 42 shown in FIG. Each of the plurality of recesses 42k is linearly formed along the direction perpendicular to the longitudinal direction of the grinding wheel 42, and is exposed at the side surfaces 42c and 42d. The plurality of recesses 42k are arranged at predetermined intervals along the longitudinal direction of the grinding wheel 42 so as to be substantially parallel to each other.

Each of the plurality of recesses 42m is linearly formed along the longitudinal direction of the grinding wheel 42 and exposed at the side surfaces 42e and 42f. The plurality of recesses 42m are arranged at predetermined intervals along the direction perpendicular to the longitudinal direction of the grinding wheel 42 so as to be substantially parallel to each other.

The recess 42k and the recess 42m intersect each other generally perpendicularly and are joined at the intersection. By forming the recesses 42k and 42m in this manner, the grinding wheel 42 having a plurality of recesses formed in a grid pattern on the grinding surface 42a can be obtained. A region defined by the plurality of recesses 42k and the plurality of recesses 42m constitutes a grinding region 42n for grinding the workpiece.

When the grinding wheel 42 having the recess 42k and the recess 42m is fixed to the base 40 (see FIG. 2), the side 42c or the side 42d where the recess 42k is exposed faces the opening 40c of the base 40. FIG. Moreover, the side surfaces 42e and 42f where the concave portion 42m is exposed face the gap between the grinding wheels 42 adjacent to each other. Therefore, the grinding fluid supplied from the grinding fluid supply port 40e toward the radially outer side of the base 40 and the grinding fluid supplied from the grinding fluid supply port 40e toward the gap between the adjacent grinding wheels 42 Both can be efficiently incorporated inside the ground surface 42a.

The number, depth, and width of the recesses 42k and 42m can be appropriately set similarly to the recesses 42g (see FIG. 3). Also, the width of the grinding region 42n in the direction perpendicular to the longitudinal direction of the grinding wheel 42 and the width of the grinding region 42n in the longitudinal direction of the grinding wheel 42 can be set as appropriate.

When the grinding wheel 42 having the recess 42k and the recess 42m is fixed to the base 40 (see FIG. 2) to grind the workpiece, frictional force acts on the grinding wheel 42 along its longitudinal direction. do. Therefore, the width of the grinding region 42n in the longitudinal direction of the grinding wheel 42 is set larger than the width of the grinding region 42n in the direction perpendicular to the longitudinal direction of the grinding wheel 42, so that the grinding region 42n is less likely to be damaged by friction. is preferred.

As described above, the grinding wheel 34 according to the present embodiment includes the grinding wheel 42 having a recessed portion formed on the grinding surface 42a side, and the grinding fluid flows through the recessed portion during the grinding process to the grinding surface 42a and the workpiece. is configured to be supplied between As a result, it is possible to suppress consumption of the grinding wheel 42 caused by frictional heat due to contact between the grinding wheel 42 and the workpiece or residual grinding debris generated by grinding.

Next, evaluation results of the grinding wheel according to this embodiment will be described. In this evaluation, the workpiece was ground using a grinding wheel equipped with a grinding wheel having recesses formed on the grinding surface, and the amount of consumption of the grinding wheel at that time was measured.

For the evaluation, a grinding wheel 36 in which rectangular parallelepiped grinding wheels 42 having a length of 20 mm, a width of 3 mm, and a thickness (height) of 7 mm were arranged in a ring as shown in FIG. 2 was used (grinding wheel A). . This grinding wheel 42 was formed by fixing diamond abrasive grains with an average grain size of 12 μm with a vitrified bond.

Also, on the grinding surface 42a side of the grinding wheel 42, grid-shaped recesses (linear recesses 42k and linear recesses 42m) as shown in FIG. 5 were formed. However, the number of recessed portions 42k was set to four, and the number of recessed portions 42m was set to one. The four recesses 42k were formed along a direction perpendicular to the longitudinal direction of the grinding wheel 42 so that the grinding surface 42a was divided into approximately five equal parts. One recess 42m is formed along the longitudinal direction of the grinding wheel 42 so that the grinding surface 42a is substantially divided into two halves. The width of the recess 42k and the width of the recess 42m were set to 120 μm, and the depth of the recess 42k and the depth of the recess 42m were set to 4 mm.

Further, as a comparative example, a grinding wheel (grinding wheel B) was formed in which grinding wheels having no recesses formed on the grinding surface were arranged in an annular shape. The structure of the grinding wheel of grinding wheel B was the same as that of grinding wheel A, except that no recesses were formed in the grinding surface.

Then, the grinding wheel A was used to grind a silicon wafer having a diameter of 8 inches by 50 μm in the thickness direction, and a total of 75 silicon wafers were ground. The grinding was performed while supplying pure water as a grinding fluid. Moreover, the consumption amount of the grinding wheel 42 was measured each time the grinding of each silicon wafer was completed. The amount of wear of the grinding wheel 42 was obtained by measuring the difference in thickness (height) of the grinding wheel before and after grinding.

Further, the grinding wheel B was similarly subjected to the grinding of the silicon wafer and the measurement of the wear amount. Then, the grinding wheel A and the grinding wheel B were compared in terms of grinding wheel consumption. FIG. 6 is a graph showing the relationship between the number of processed wafers and the consumption of the grinding wheel. In addition, FIG. 6 shows measured values obtained by measuring the wear amount of the grinding wheel with a predetermined accuracy using a measuring device provided in the grinding apparatus.

As shown in FIG. 6, the wear amount of the grinding wheel 42 (with recesses) of the grinding wheel A after grinding 75 silicon wafers is about 2/3 of the wear amount of the grinding wheel B (without recesses). is suppressed to This is because, when grinding a silicon wafer with the grinding wheel A, the grinding fluid is sufficiently supplied to the grinding surface 42a through the recesses formed in the grinding surface 42a, and the frictional heat and the residual grinding dust cause the grinding wheel 42 to This is thought to be because the consumption of the

Moreover, no breakage of the grinding wheel 42 was observed in the grinding wheel A after the evaluation, and it was confirmed that the grinding wheel 42 had the strength necessary for grinding.

From the above evaluation, it was confirmed that the consumption of the grinding wheel 42 can be suppressed by using the grinding wheel provided with the grinding wheel 42 having the concave portion formed on the grinding surface 42a side.

In this embodiment, as shown in FIGS. 3 to 5, the grinding wheel 42 having linear concave portions is shown, but the shape of the concave portions is not limited to this. For example, the grinding wheel 42 may have curved (sinusoidal, arcuate, etc.) or polygonal (zigzag, sawtooth, etc.) recesses.

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

2 Grinding device 4 Base 4a Opening 6 Support structure 8 X-axis movement mechanism 8a X-axis movement table 10 Dust and drip proof cover 12 Operation panel 14 Chuck table 14a Suction surface 16 Z-axis movement mechanism 18 Z-axis guide rail 20 Z-axis movement plate 22 Z-axis ball screw 24 Z-axis pulse motor 26 Support tool 28 Grinding unit 30 Spindle housing 32 Spindle 34 Wheel mount 36 Grinding wheel 40 Base 40a First surface 40b Second surface 40c Opening 40d Groove 40e Grinding liquid supply port 42 Grinding wheel 42a Grinded surface 42b Mounting surface 42c, 42d, 42e, 42f Side surface 42g, 42i, 42k, 42m Concave portion 42h, 42j, 42n Grinding area

Claims (3)

A grinding wheel for grinding a workpiece with a grinding surface of a grinding wheel,
A base and a plurality of grinding wheels arranged in a ring on the base,
A plurality of recesses serving as flow paths for a grinding fluid are formed on the grinding surface side of the grinding wheel so as to be exposed on the side surface of the grinding wheel ,
The grinding wheels have different lengths and widths,
A grinding wheel, wherein the recess is formed along the longitudinal direction of the grinding wheel and not along the direction perpendicular to the longitudinal direction of the grinding wheel. The recess has a depth of 10 μm or more,
2. The grinding wheel of claim 1, wherein the width of said recess is greater than 120 .mu.m. 3. A grinding wheel according to claim 1, wherein said recess has a depth of 1 mm or more.

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