Grindstone

Abstract

To provide a grindstone that can suppress a processing failure.SOLUTION: A grindstone for processing a workpiece includes abrasive grains and a binder for fixing the abrasive grains. The binder includes volume expansion particles expanding the volume during processing of a workpiece.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a grinding wheel for machining a workpiece. [Background technology]

[0002] A wafer on which a plurality of devices are formed is divided and diced to produce device chips each including a device. A package substrate is formed by mounting a plurality of device chips on a predetermined substrate and covering and sealing the mounted device chips with a resin layer (mold resin). A package device including a plurality of packaged device chips is manufactured by dividing and dicing the package substrate. The device chips and package devices are incorporated into various electronic devices such as mobile phones and personal computers.

[0003] A cutting device is used to divide workpieces such as wafers and package substrates. The cutting device includes a chuck table that holds the workpiece, and a cutting unit that performs cutting processing on the workpiece. The cutting unit is fitted with an annular cutting blade having a grinding wheel (cutting edge) that comes into contact with the workpiece and cuts it. The workpiece is held on the chuck table, and the grinding wheel is cut into the workpiece while the cutting blade is rotated, cutting and dividing the workpiece (see Patent Document 1).

[0004] In recent years, with the miniaturization of electronic devices, there is a demand for thinner device chips and package devices. Therefore, a grinding device may be used to grind and thin wafers and package substrates before division. The grinding device includes a chuck table for holding the workpiece and a grinding unit for grinding the workpiece. The grinding unit is equipped with an annular grinding wheel having a plurality of grindstones (grinding wheels) that come into contact with the workpiece and grind it. The workpiece is held by the chuck table, and the grindstones are brought into contact with the workpiece while rotating the chuck table and the grinding wheel, thereby grinding and thinning the workpiece (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-87282 A [Patent Document 2] JP 2006-1007 A Summary of the Invention [Problem to be solved by the invention]

[0006] The grinding stone of a cutting blade or grinding wheel is formed by fixing abrasive grains made of diamonds or the like with a binder. The abrasive grains exposed from the binder collide with the workpiece, and the workpiece is subjected to a crushing process such as cutting or grinding. Furthermore, when the grinding stone continues to process the workpiece, the binder of the grinding stone wears out, and the abrasive grains exposed from the binder fall off, and a phenomenon called self-sharpening occurs in which the abrasive grains embedded inside the binder are newly exposed. This self-sharpening blade keeps the grinding stone in good condition and maintains the grinding stone's processing ability.

[0007] However, depending on the material of the workpiece, the material of the binder of the grinding wheel, the processing conditions, etc., the abrasive grains may not fall off due to wear of the binder, and self-sharpening may be stagnant. If the processing of the workpiece continues without self-sharpening occurring at an appropriate frequency, problems such as dulling, in which the abrasive grains exposed from the binder are worn down and smoothed by contact with the workpiece, and clogging, in which the chips (processing chips) generated by processing adhere to the abrasive grains or gaps between the abrasive grains and prevent the abrasive grains from being exposed, are likely to occur. This causes the condition of the grinding wheel to deteriorate and the processing capacity to decrease.

[0008] If the processing of the workpiece continues with the grindstone's processing ability reduced, the pressure (processing load) applied to the workpiece increases while the grindstone is processing the workpiece, making processing defects more likely to occur. In particular, when processing a workpiece made of a material that is difficult to process by cutting or grinding (such as SiC wafers, GaN wafers, and sapphire wafers) with a grindstone, processing defects due to the increased processing load are more likely to occur.

[0009] The present invention has been made in consideration of such problems, and has an object to provide a grinding wheel that can suppress the occurrence of processing defects. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a grinding wheel for processing a workpiece, the grinding wheel comprising abrasive grains and a binder for fixing the abrasive grains, the binder containing volume-expanding particles whose volume expands during processing of the workpiece.

[0011] Preferably, the content of the volume expansion particles is 3.0 vol % or more and 14.0 vol % or less. Also, preferably, the average particle size of the volume expansion particles is smaller than the average particle size of the abrasive grains. Effect of the Invention

[0012] The grindstone according to one aspect of the present invention includes a binder containing volume-expanding particles that expand in volume during machining of a workpiece. This promotes self-sharpening during machining of the workpiece, maintains the condition of the grindstone in good condition, and suppresses the occurrence of machining defects. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1(A) is a perspective view showing a washer-type cutting blade, and FIG. 1(B) is a perspective view showing a hub-type cutting blade. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a cross-sectional view showing a part of the grindstone. [Figure 4]FIG. [Diagram 5] FIG. 2 is a cross-sectional view showing a part of the grindstone. [Figure 6] 1 is a graph showing the wear rate of a cutting blade. [Figure 7] 4 is a graph showing a current value of a spindle motor during machining of a workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (Embodiment 1) Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. First, a configuration example of a grindstone according to the present embodiment will be described. The grindstone according to the present embodiment is used as a cutting edge of a cutting blade, which is a processing tool that cuts a workpiece.

[0015] 1(A) is a perspective view showing a cutting blade 10. The cutting blade 10 is a washer-type cutting blade (washer blade) whose entirety functions as an annular cutting blade.

[0016] The cutting blade 10 is composed only of an annular grindstone (cutting edge) 12. The grindstone 12 includes a first surface (front surface) 12a and a second surface (back surface) 12b that are generally parallel to each other. In addition, a circular through hole 12c is provided in the center of the grindstone 12, penetrating the grindstone 12 in the thickness direction from the first surface 12a to the second surface 12b.

[0017] 1(B) is a perspective view showing the cutting blade 20. The cutting blade 20 is a hub-type cutting blade (hub blade) that includes an annular hub base 22 and an annular grinding wheel (cutting blade) 24 provided along the outer periphery of the hub base 22.

[0018] For example, the hub base 22 is made of a metal such as an aluminum alloy, and includes a first surface (front surface) 22a and a second surface (back surface) 22b. A circular through-hole 22c is provided in the center of the hub base 22, penetrating the hub base 22 in the thickness direction from the first surface 22a to the second surface 22b of the hub base 22. In addition, an annular protrusion 22d is provided around the through-hole 22c, protruding from the first surface 22a of the hub base 22 in the thickness direction of the hub base 22.

[0019] On the second surface 22b side of hub base 22, an annular grindstone 24 is formed in an annular shape along the outer periphery of hub base 22. The outer diameter of grindstone 24 is larger than the outer diameter of hub base 22, and grindstone 24 is disposed so as to protrude from the outer periphery of hub base 22 radially outward from hub base 22.

[0020] Fig. 2 is a perspective view showing a cutting device 30 that cuts a workpiece 11. In Fig. 2, the X1 axis direction (processing feed direction, first horizontal direction) and the Y1 axis direction (indexing feed direction, second horizontal direction) are perpendicular to each other. The Z1 axis direction (height direction, up-down direction, vertical direction) is perpendicular to the X1 axis direction and the Y1 axis direction. The cutting blade 10 (see Fig. 1(A)) and the cutting blade 20 (see Fig. 1(B)) are attached to the cutting device 30 and cut the workpiece 11.

[0021] For example, the workpiece 11 is a disk-shaped wafer made of a semiconductor material such as Si, GaAs, InP, GaN, or SiC, and has a front surface 11a and a back surface 11b that are generally parallel to each other. The workpiece 11 is divided into a plurality of rectangular regions by a plurality of streets (planned division lines) 13 that are arranged in a lattice pattern so as to intersect with each other.

[0022] Devices 15 such as ICs (Integrated Circuits), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), MEMS (Micro Electro Mechanical Systems) devices, etc. are formed on the front surface 11a side of the areas partitioned by the streets 13. The workpiece 11 is cut and divided along the streets 13 with the cutting blade 10 or the cutting blade 20, thereby producing a plurality of device chips each including a device 15.

[0023] However, there are no limitations on the material, shape, structure, size, etc. of the workpiece 11. For example, the workpiece 11 may be a substrate (wafer) made of glass, sapphire, ceramics, resin, metal, etc. In addition, there are no limitations on the type, number, shape, structure, size, arrangement, etc. of the devices 15, and the devices 15 do not have to be formed on the workpiece 11.

[0024] Furthermore, the workpiece 11 may be a package substrate such as a CSP (Chip Size Package) substrate or a QFN (Quad Flat Non-leaded package) substrate. For example, a package substrate is formed by mounting a plurality of device chips on a predetermined substrate and covering and sealing the mounted device chips with a resin layer (molding resin). By cutting and dividing the package substrate with the cutting blade 10 or the cutting blade 20, a plurality of package devices each including a plurality of packaged device chips are manufactured.

[0025] When processing the workpiece 11 with the cutting device 30, the workpiece 11 may be supported by an annular frame 17 for ease of handling (transporting, holding, etc.) the workpiece 11. The frame 17 is an annular member made of a metal such as SUS (stainless steel), and a circular opening 17a is provided in the center of the frame 17, penetrating the frame 17 in the thickness direction. The diameter of the opening 17a is larger than the diameter of the workpiece 11.

[0026] A circular sheet 19 is fixed to the workpiece 11 and the frame 17. For example, a tape having a circular film-like base material and an adhesive layer (glue layer) provided on the base material is used as the sheet 19. Also, a thermo-compression sheet that does not have an adhesive layer and can be thermo-compression bonded to the workpiece 11 and the frame 17 can be used as the sheet 19.

[0027] With the workpiece 11 placed inside the opening 17a of the frame 17, the center of the sheet 19 is affixed to the back surface 11b of the workpiece 11, and the outer periphery of the sheet 19 is affixed to the frame 17. As a result, the workpiece 11 is supported by the frame 17 via the sheet 19.

[0028] The workpiece 11 is carried into the cutting device 30 while being supported by the frame 17, and is cut by the cutting blade 10 or the cutting blade 20. The cutting device 30 includes a chuck table (holding table) 32 that holds the workpiece 11, and a cutting unit 34 that performs cutting on the workpiece 11 held by the chuck table 32.

[0029] The upper surface of the chuck table 32 is a flat surface roughly parallel to the horizontal plane (X1Y1 plane) and constitutes a circular holding surface that holds the workpiece 11. The holding surface of the chuck table 32 is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like provided inside the chuck table 32. In addition, the chuck table 32 is connected to a ball screw type moving mechanism (not shown) that moves the chuck table 32 along the X1 axis direction, and a rotation drive source (not shown) such as a motor that rotates the chuck table 32 around a rotation axis roughly parallel to the Z1 axis direction.

[0030] A cutting unit 34 is disposed above the chuck table 32. The cutting unit 34 includes a cylindrical housing 36, and a columnar spindle (not shown) disposed along the Y1-axis direction is accommodated in the housing 36. A tip end (one end) of the spindle is exposed to the outside of the housing 36, and a rotation drive source (not shown), such as a spindle motor, is connected to a base end (the other end) of the spindle.

[0031] A cutting blade 10 (see FIG. 1(A)) or cutting blade 20 (see FIG. 1(B)) is attached to the tip of the spindle. In this embodiment, as a representative example, a case where the cutting blade 10 is attached to the cutting unit 34 will be described. When the rotation drive source is operated with the cutting blade 10 attached to the tip of the spindle, the cutting blade 10 rotates around a rotation axis roughly parallel to the Y1 axis direction due to the power transmitted from the rotation drive source via the spindle.

[0032] The cutting blade 10 attached to the tip of the spindle is covered by a blade cover 38 fixed to a housing 36. The blade cover 38 includes a pair of connection parts 40 connected to a tube (not shown) through which a liquid (machining fluid) such as pure water is supplied, and a pair of nozzles 42 connected to the connection parts 40 and disposed on both sides of the cutting blade 10. Each of the pair of nozzles 42 is provided with an injection port (not shown) that opens toward the cutting blade 10.

[0033] When machining fluid is supplied to the connection portion 40, the machining fluid is sprayed from the nozzles of the pair of nozzles 42 toward both sides of the cutting blade 10. The machining fluid cools the workpiece 11 and the cutting blade 10, and washes away chips (machining chips) generated by the cutting process.

[0034] Further, a ball screw type moving mechanism (not shown) that moves the cutting unit 34 is connected to the cutting unit 34. This moving mechanism moves the cutting unit 34 along the Y1 axis direction and raises and lowers it along the Z1 axis direction. The moving mechanism adjusts the positions of the cutting blade 10 in the Y1 axis direction and the Z1 axis direction.

[0035] When the workpiece 11 is machined using the cutting device 30, first, the workpiece 11 is held by the chuck table 32. For example, the workpiece 11 is placed on the chuck table 32 so that the front surface 11a faces upward and the back surface 11b (the sheet 19 side) faces the holding surface. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface, the workpiece 11 is sucked and held by the chuck table 32 via the sheet 19.

[0036] Next, the chuck table 32 is rotated to align the length direction of the predetermined street 13 with the X1 axis direction. The position of the cutting unit 34 in the Y1 axis direction is adjusted so that the cutting blade 10 is positioned on an extension line of the predetermined street 13. Furthermore, the height of the cutting unit 34 is adjusted so that the lower end of the cutting blade 10 is positioned lower than the back surface 11b of the workpiece 11 (the upper surface of the sheet 19). The difference in height between the front surface 11a of the workpiece 11 and the lower end of the cutting blade 10 at this time corresponds to the cutting depth of the cutting blade 10 into the workpiece 11.

[0037] Then, while rotating the cutting blade 10, the chuck table 32 is moved along the X1 axis direction. As a result, the chuck table 32 and the cutting blade 10 move relatively along the X1 axis direction (processing feed), and the cutting blade 10 cuts into the workpiece 11 along the predetermined streets 13. As a result, the workpiece 11 is cut and divided along the predetermined streets 13. Thereafter, by repeating the same procedure, the workpiece 11 is divided along all of the streets 13. As a result, a plurality of device chips each including a device 15 are obtained.

[0038] However, the content of the cutting process performed on the workpiece 11 is appropriately set according to the purpose of the process. For example, by setting the cutting depth to less than the thickness of the workpiece 11, a cutting groove having a depth less than the thickness of the workpiece 11 can be formed on the surface 11a side of the workpiece 11 (half cut). Also, instead of the cutting blade 10, a cutting blade 20 (see FIG. 1(B)) may be attached to the cutting unit 34, and the workpiece 11 may be cut with the cutting blade 20. In this case, the grindstone 24 of the cutting blade 20 is caused to cut into the workpiece 11, thereby cutting the workpiece 11.

[0039] 3 is a cross-sectional view showing a part of the grinding wheel 12 constituting the cutting blade 10. The grinding wheel 12 includes abrasive grains 14 made of diamond, cubic boron nitride (cBN), or the like, and a bonding material (bonding agent) 16, such as a resin bond, a metal bond, or a vitrified bond, that fixes the abrasive grains 14.

[0040] When the cutting blade 10 is rotated and cut into the workpiece 11 (see FIG. 2), the abrasive grains 14 exposed from the binder 16 collide with the workpiece 11, cutting the workpiece 11. Furthermore, as the grindstone 12 continues to cut the workpiece 11, the binder 16 gradually wears away due to contact with the workpiece 11. As a result, a phenomenon known as self-sharpening occurs, in which the abrasive grains 14 exposed from the binder 16 fall off and the abrasive grains 14 embedded inside the binder 16 are newly exposed. This self-sharpening keeps the condition of the grindstone 12 in order, and the cutting ability (sharpness) of the grindstone 12 is maintained.

[0041] However, depending on the material of the workpiece 11, the material of the binder 16, the processing conditions, etc., the abrasive grains 14 may not easily fall off due to wear of the binder 16, and the self-sharpening may be stagnant. If the processing of the workpiece 11 is continued without self-sharpening occurring at an appropriate frequency, problems such as dulling, in which the abrasive grains 14 exposed from the binder 16 are worn and smoothed by contact with the workpiece 11, and clogging, in which processing debris adheres to the abrasive grains 14 or gaps between the abrasive grains 14 and prevents the exposure of the abrasive grains 14, are likely to occur. As a result, the cutting ability of the grindstone 12 decreases, the processing load increases, and there is a risk of processing defects occurring.

[0042] Therefore, in this embodiment, as shown in Fig. 3, volume expansion particles 18, which expand in volume during processing of the workpiece 11, are contained in the binder 16 of the grindstone 12. This makes it easier for the binder 16 to wear during processing of the workpiece 11, promotes spontaneous cutting, and suppresses the occurrence of processing defects.

[0043] Specifically, the volume expansion particles 18 have the property of expanding in volume due to heat generation by the grindstone 12 during processing of the workpiece 11. When the workpiece 11 is cut with the grindstone 12, frictional heat is generated by contact between the grindstone 12 rotating at high speed and the workpiece 11, causing the grindstone 12 to heat up. Then, the increase in temperature of the grindstone 12 heats the volume expansion particles 18, causing them to expand.

[0044] When the volume expansion particles 18 expand, stress acts on the binder 16 around the volume expansion particles 18, causing microcracks in the binder 16. Then, wear of the binder 16 is induced starting from the cracks, promoting spontaneous sharpening of the grinding wheel 12. This prevents or eliminates dulling and clogging, maintaining the condition of the grinding wheel 12 in good condition, and suppresses a decrease in the cutting ability of the grinding wheel 12.

[0045] Particles that expand when heated (thermally expandable particles) can be used as the volume-expanding particles 18. For example, microcapsules that expand when heated (thermally expandable microcapsules) are used as the volume-expanding particles 18. An example of a commercially available thermally expandable microcapsule is Kureha Microsphere (registered trademark) manufactured by Kureha Corporation.

[0046] However, it is sufficient that the volume expansion particles 18 have the property of expanding when the workpiece 11 is processed. For example, the volume expansion particles 18 may be particles such as metal powder (oxidation expansion particles) whose volume expands as a result of oxidation being promoted by frictional heat between the workpiece 11 and the grindstone 12. In this case, the Pilling-Bedworth ratio (PB ratio) of the volume expansion particles 18 is preferably 2.0 or more, and more preferably 2.5 or more. The PB ratio is expressed as the volume of metal per metal atom, V m , where the volume of oxide per metal ion is V0, V0 / V m For example, Nb particles (powder) can be used as the volume expansion particles 18.

[0047] In the case where the volume expansion particles 18 are oxidized expansion particles, the volume expansion particles 18 exposed from the binder 16 are oxidized when the workpiece 11 is cut with the grindstone 12. The volume expansion particles 18 are also heated by frictional heat between the workpiece 11 and the grindstone 12, accelerating the oxidation of the volume expansion particles 18. As a result, the volume of the volume expansion particles 18 increases, causing stress to act on the binder 16, accelerating the wear of the binder 16.

[0048] For the volume expansion particles 18, a substance is selected that can expand to an extent that accelerates wear of the binder 16 due to heat generation from the grindstone 12 during processing. For example, when cutting the workpiece 11 with the grindstone 12, the temperature in the contact area between the workpiece 11 and the grindstone 12 rises from room temperature (15 to 25°C) to about 100 to 300°C due to frictional heat. For this reason, it is preferable to use, as the volume expansion particles 18, a substance whose volume increases (preferably by at least two times, more preferably by at least three times) when the temperature rises from room temperature to 100 to 300°C.

[0049] The content of the volume expansion particles 18 is appropriately set so as to promote spontaneous cutting while ensuring the overall strength of the grinding wheel 12 required for cutting the workpiece 11. In particular, the content of the volume expansion particles 18 is preferably 3.0 vol% or more and 14.0 vol% or less, and more preferably 4.0 vol% or more and 8.0 vol% or less. This makes it possible to effectively generate spontaneous cutting due to wear of the binder 16 while avoiding damage to the grinding wheel 12 during processing of the workpiece 11. The content (vol%) of the volume expansion particles 18 corresponds to the ratio of the volume of the volume expansion particles 18 to the overall volume of the grinding wheel 12 (the sum of the volumes of the abrasive grains 14, the binder 16, and the volume expansion particles 18).

[0050] Moreover, the average particle size of the volume expansion particles 18 is preferably smaller than that of the abrasive grains 14. This prevents the volume expansion particles 18 from contacting the workpiece 11 excessively, and prevents the cutting of the workpiece 11 by the abrasive grains 14 from being hindered by the volume expansion particles 18. Specifically, the average particle size of the volume expansion particles 18 is preferably 80% or less, more preferably 60% or less, of the average particle size of the abrasive grains 14. For example, the average particle size of the abrasive grains 14 is 10 μm or more and 60 μm or less, preferably 20 μm or more and 50 μm or less. Moreover, the average particle size of the volume expansion particles 18 is set to be smaller than the average particle size of the abrasive grains 14, for example, within the range of 5 μm or more and 45 μm or less.

[0051] The relationship in average particle size between the abrasive grains 14 and the volume-expansion particles 18 can be confirmed by measuring the average particle size of the abrasive grains 14 and the average particle size of the volume-expansion particles 18 using the same measurement method and comparing the results of both measurements. For example, the average particle size values ​​of the abrasive grains 14 and the volume-expansion particles 18 described above correspond to the particle size at 50% cumulative of the particle size distribution (median diameter, d50, 50% diameter) measured by a laser diffraction / scattering method.

[0052] As described above, by including the volume expansion particles 18 in the binder 16, wear of the binder 16 is accelerated during cutting of the workpiece 11, and self-sharpening of the grindstone 12 is facilitated. This maintains the condition of the grindstone 12 in good condition, and suppresses the occurrence of processing defects.

[0053] The grindstone 12 containing the volume expansion particles 18 can be manufactured by incorporating the volume expansion particles 18 in a binder together with abrasive grains in a conventional cutting blade manufacturing method. For example, the grindstone 12 and the volume expansion particles 18 are mixed with a resin such as phenol, and the resin is baked and thermally cured using a hot press method or the like, thereby manufacturing the grindstone 12 containing the grindstone 12 and the volume expansion particles 18 in the binder 16 (resin bond).

[0054] The grindstone 12 can also be manufactured by electrolytic plating. In this case, a plating solution containing the abrasive grains 14 and the volume-expansion particles 18 is first stored in a plating bath. As the plating solution, for example, an electrolytic solution containing Ni is used. Then, a base on which a plating layer is to be electrodeposited and a plate-shaped electrode made of Ni are immersed in the plating solution. Note that a mask having an annular opening corresponding to the shape of the cutting blade 10 (see FIG. 1(A)) is formed in advance on the base.

[0055] Next, while stirring the plating solution, the base is connected to the negative terminal (negative electrode) of a DC power supply, and the electrode is connected to the positive terminal (positive electrode) of the DC power supply. As a result, the base functions as a cathode and the electrode functions as an anode, and a DC current flows through the plating solution. Then, a nickel plating layer containing abrasive grains 14 and volume-expanding particles 18 is electrodeposited on the annular region of the base that is not covered by the mask. As a result, a grinding wheel 12 is manufactured in which the abrasive grains 14 and volume-expanding particles 18 are contained in the binder 16 (nickel plating layer).

[0056] As described above, the grindstones 12, 24 of the cutting blades 10, 20 according to this embodiment include the binder 16 containing volume expansion particles 18 whose volume expands during processing of the workpiece 11. This promotes spontaneous cutting during processing of the workpiece 11, maintains the condition of the grindstones 12, 24 in good condition, and suppresses the occurrence of processing defects.

[0057] In the above, the grinding wheel 12 of the cutting blade 10 (see Figs. 1(A) and 3) has been described as a representative example. However, the structure and function of the grinding wheel 24 of the cutting blade 20 are similar to those of the grinding wheel 12 of the cutting blade 10 (see Fig. 3). For example, a binder 16 (nickel plating layer) containing abrasive grains 14 and volume expansion particles 18 is annularly electrodeposited along the outer periphery of the hub base 22 by electrolytic plating.

[0058] In addition, the structures, methods, etc. according to the present embodiment can be modified as appropriate without departing from the scope of the object of the present invention.

[0059] (Embodiment 2) In the above embodiment 1, the grindstone according to the present invention is used as a cutting edge of a cutting blade. However, the grindstone according to the present invention can also be used for other processing tools. In this embodiment, the grindstone according to the present invention is used for a grinding wheel that grinds a workpiece 11.

[0060] Fig. 4 is a perspective view showing a grinding device 50 that grinds a workpiece 11. In Fig. 4, the X2 axis direction (first horizontal direction) and the Y2 axis direction (second horizontal direction) are perpendicular to each other. The Z2 axis direction (up-down direction, height direction, vertical direction) is perpendicular to the X2 axis direction and the Y2 axis direction.

[0061] The grinding device 50 grinds and thins the workpiece 11 with a grinding wheel 60. For example, before dividing the workpiece 11 along the streets 13 with the cutting device 30 (see FIG. 2), the back surface 11b side of the workpiece 11 is ground to thin the workpiece 11, thereby making it possible to manufacture a thinned device chip.

[0062] The grinding device 50 includes a chuck table (holding table) 52 that holds the workpiece 11. The upper surface of the chuck table 52 is a flat surface that is approximately parallel to the horizontal plane (X2Y2 plane) and constitutes a holding surface 52a that holds the workpiece 11. The holding surface 52a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like provided inside the chuck table 52. In addition, the chuck table 52 is connected to a moving mechanism (not shown) that moves the chuck table 52 along the horizontal direction (X2Y2 plane direction) and a rotation drive source (not shown) such as a motor that rotates the chuck table 52 around a rotation axis that is approximately parallel to the Z2 axis direction.

[0063] A grinding unit 54 that performs grinding on the workpiece 11 is provided above the chuck table 52. The grinding unit 54 includes a cylindrical spindle 56 arranged along the Z2-axis direction. A rotation drive source (not shown), such as a spindle motor, that rotates the spindle 56 is connected to a base end (upper end) of the spindle 56.

[0064] A disk-shaped wheel mount 58 made of metal or the like is fixed to the tip (lower end) of the spindle 56. An annular grinding wheel 60 for grinding the workpiece 11 is removably attached to the lower surface side of the wheel mount 58. For example, the grinding wheel 60 is fixed to the wheel mount 58 by a fastener such as a bolt.

[0065] The grinding wheel 60 includes an annular wheel base 62. The wheel base 62 is made of a metal such as aluminum or stainless steel, and is formed to have approximately the same diameter as the wheel mount 58. The upper surface side of the wheel base 62 is fixed to the lower surface side of the wheel mount 58. In addition, a plurality of grindstones (grinding wheels) 64 are fixed to the lower surface side of the wheel base 62. For example, the grindstones 64 are formed in a rectangular parallelepiped shape, and are arranged in a ring shape at approximately equal intervals along the circumferential direction of the wheel base 62. However, there are no limitations on the shape, structure, size, etc. of the grindstones 64, and the number of grindstones 64 can be set arbitrarily.

[0066] The grinding wheel 60 rotates about a rotation axis roughly parallel to the Z2 axis direction by power transmitted from a rotation drive source (not shown) via the spindle 56 and the wheel mount 58. When the grinding wheel 60 rotates, each of the multiple grindstones 64 revolves around the rotation axis of the grinding wheel 60 along a circular revolution orbit (revolution path) roughly parallel to the horizontal plane (X2Y2 plane).

[0067] A ball screw type moving mechanism (not shown) that moves (lifts and lowers) the grinding unit 54 along the Z2 axis direction is connected to the grinding unit 54. When the grinding unit 54 is lifted and lowered by the moving mechanism, the grinding wheel 60 moves relative to the chuck table 52, and the holding surface 52a and the grinding wheel 60 move closer to or away from each other.

[0068] A machining fluid supply path (not shown) for supplying a liquid (machining fluid) such as pure water is provided inside or near the grinding unit 54. When the workpiece 11 is ground with the grinding wheel 60, the machining fluid is supplied to the workpiece 11 and the grindstone 64. This cools the workpiece 11 and the grindstone 64, and washes away chips (machining chips) generated by the grinding process.

[0069] When grinding the workpiece 11 with the grinding device 50, the workpiece 11 is first held by the chuck table 52. For example, the workpiece 11 is placed on the chuck table 52 so that the front surface 11a faces the holding surface 52a and the back surface 11b (surface to be ground) is exposed upward. When the suction force (negative pressure) of the suction source is applied to the holding surface 52a in this state, the workpiece 11 is sucked and held by the chuck table 52. Note that a protective sheet for protecting the workpiece may be fixed to the front surface 11a side of the workpiece 11.

[0070] Next, the positional relationship between the chuck table 52 and the grinding wheel 60 is adjusted. For example, the chuck table 52 is positioned below the grinding wheel 60 so that the rotation path of the grinding wheel 64 overlaps with the center of the workpiece 11 in the Z2-axis direction. Then, while rotating the chuck table 52 and the spindle 56, the grinding unit 54 is lowered at a predetermined speed to bring the grinding wheel 60 closer to the workpiece 11. When the grinding wheel 64 comes into contact with the back surface 11b of the workpiece 11, the back surface 11b side of the workpiece 11 is scraped off, and the workpiece 11 is ground and thinned.

[0071] 5 is a cross-sectional view showing a portion of a grinding wheel 64 of a grinding wheel 60. The grinding wheel 64 includes abrasive grains 66 made of diamond, cubic boron nitride, or the like, and a bonding material (bonding agent) 68, such as a resin bond or a vitrified bond, that fixes the abrasive grains 66.

[0072] When the grinding wheel 60 is rotated and the grindstone 64 is brought into contact with the workpiece 11 (see FIG. 4), the abrasive grains 66 exposed from the binder 68 collide with the workpiece 11, grinding the workpiece 11. Furthermore, as grinding of the workpiece 11 with the grindstone 64 continues, the binder 68 gradually wears away due to contact with the workpiece 11, causing the grindstone 64 to self-sharpen. This keeps the condition of the grindstone 64 in order, and the grinding ability of the grindstone 64 is maintained.

[0073] The binder 68 of the grindstone 64 contains volume-expanding particles 70 whose volume expands during machining of the workpiece 11. The type, material, characteristics (PB ratio, etc.), content, average particle size, etc. of the volume-expanding particles 70 are similar to those of the volume-expanding particles 18 (see FIG. 3) contained in the binder 16 of the grindstones 12, 24 (see FIGS. 1(A) and 1(B)). The size relationship between the average particle size of the abrasive grains 66 and the average particle size of the volume-expanding particles 70 can also be set in the same way as the abrasive grains 14 and the volume-expanding particles 18 (see FIG. 3).

[0074] When the workpiece 11 is ground with the grindstone 64, frictional heat is generated by contact between the grindstone 64 rotating at high speed and the workpiece 11, causing the grindstone 64 to heat up. As the temperature of the grindstone 64 rises, the volume-expanding particles 70 are heated and expand. When the volume-expanding particles 70 expand, stress acts on the binder 68 around the volume-expanding particles 70, causing tiny cracks to form in the binder 68. Wear of the binder 68 is then induced starting from the cracks, promoting the self-sharpening of the grindstone 64. This maintains the condition of the grindstone 64 in good condition, and suppresses a decrease in the grinding ability of the grindstone 64.

[0075] The grindstone 64 containing the volume expansion particles 70 can be manufactured by incorporating the volume expansion particles 70 in a binder together with abrasive grains in a conventional manufacturing method for grinding wheels. For example, the grindstone 64 and the volume expansion particles 70 are mixed with a resin such as phenol, and the resin is baked and thermally cured using a hot press method or the like, thereby manufacturing the grindstone 64 containing the grindstone 64 and the volume expansion particles 70 in the binder 68 (resin bond).

[0076] As described above, the grindstone 64 of the grinding wheel 60 according to this embodiment includes the binder 68 containing the volume expansion particles 70 whose volume expands during processing of the workpiece 11. This promotes spontaneous cutting during processing of the workpiece 11, maintains the condition of the grindstone 64 in good condition, and suppresses the occurrence of processing defects.

[0077] The structure, method, and the like according to this embodiment can be modified as appropriate without departing from the scope of the present invention. Furthermore, matters that are not described in this embodiment are the same as those in the first embodiment.

[0078] (Example) Next, the results of machining a workpiece using the grindstone according to the present invention will be described. In this test, the workpiece was cut with a washer-type cutting blade made of a grindstone (Fig. 3) containing volume expansion particles in the binder, and the frequency of self-sharpening and the machining load were evaluated.

[0079] A rectangular glass epoxy copper-clad laminate (length 150 mm, width 150 mm, thickness 1 mm) was used as the workpiece. A cutting blade A according to a comparative example (conventional example) and a cutting blade B according to the embodiment were prepared. As cutting blades A and B, a washer-type cutting blade (see FIG. 1(A)) consisting of a circular grindstone (outer diameter 59 mm, thickness 0.25 mm) was used.

[0080] Cutting blades A and B were formed by fixing abrasive grains with a binder. Diamond grains (average grain size 40 μm) were used as the abrasive grains, and a resin bond with phenolic resin as the main component was used as the binder.

[0081] The grindstone of the cutting blade A according to the comparative example was formed without adding volume expansion particles to the binder. On the other hand, the grindstone of the cutting blade B according to the embodiment was formed by adding volume expansion particles to the binder. As the volume expansion particles, a commercially available thermally expandable microcapsule (Kureha Microsphere (registered trademark), manufactured by Kureha Corporation, particle size 12 μm) was used. The content of the volume expansion particles was set to 6.0 vol%.

[0082] Then, using a cutting device (see FIG. 2), the workpiece was cut with the cutting blade A according to the comparative example and the cutting blade B according to the embodiment. Specifically, the spindle rotation speed (cutting blade rotation speed) was set to 25,000 rpm, the processing feed rate was set to 30 mm / s, and the cutting blade's cutting depth into the workpiece was set to 1 mm (full cut), and the cutting blade was caused to cut into the workpiece, cutting and dividing the workpiece along the linear processing line, and the procedure was repeated. Then, the wear rates of the cutting blades A and B and the current value of the spindle motor during cutting of the workpiece were measured.

[0083] FIG. 6 is a graph showing the wear rate of the cutting blade. The wear rate of the cutting blade corresponds to the average amount of reduction in the outer diameter of the grinding wheel per 1 m of the cutting distance (length of the processing line) of the workpiece. As shown in FIG. 6, the wear rate of the cutting blade B according to the embodiment is 0.203 μm / m, which is about 30% higher than the wear rate (0.158 μm / m) of the cutting blade A according to the comparative example. From this result, it was confirmed that by including volume expansion particles in the binder, the binder of the grinding wheel becomes more easily worn, and self-sharpening of the edge is promoted.

[0084] Figure 7 is a graph showing the current value of the spindle motor during machining of the workpiece. A spindle motor that rotates the spindle is connected to the spindle of the cutting device. In this test, the current value of the spindle motor was measured while rotating the spindle with the spindle motor to cut cutting blades A and B into the workpiece.

[0085] When the rotating cutting blades A and B come into contact with the workpiece, a load is applied to the cutting blades A and B. As a result, the spindle torque required to maintain the rotation of the cutting blades A and B increases, and the current value of the spindle motor also increases. Furthermore, if the condition of the cutting blades A and B deteriorates due to dulling or clogging while cutting the workpiece, the cutting ability (sharpness) of the cutting blades A and B decreases, the load (processing load) applied to the workpiece and the cutting blades A and B during cutting increases, and the current value of the spindle motor also increases. In other words, the current value of the spindle motor reflects the change in the processing load during cutting.

[0086] As shown in Fig. 7, it was confirmed that the current value of the spindle motor was lower when the cutting blade B according to the embodiment was used than when the cutting blade A according to the comparative example was used. This is presumably due to the fact that the self-sharpening of the cutting edge was promoted by including volume expansion particles in the binder, and the cutting ability of the cutting blade was well maintained during cutting of the workpiece.

[0087] From the above test results, it was confirmed that the use of the grindstone according to the present invention promotes self-sharpening, reduces the processing load, and effectively suppresses the occurrence of processing defects. [Explanation of symbols]

[0088] 11 Workpiece 11a surface 11b Back side 13th Street (Planned division line) 15 Devices 17 Frame 17a aperture 19 sheets 10 Cutting blade 12 Grindstone (cutting blade) 12a 1st side (front) 12b Side 2 (back) 12c through hole 14 Abrasive grain 16 Bonding material (bonding agent) 18 Volume expansion particles 20 Cutting blade 22 Hub Base 22a 1st side (front) 22b 2nd side (back side) 22c through hole 22d Convex 24 Grindstone (Cutting Blade) 30 Cutting equipment 32 Chuck table (holding table) 34 Cutting unit 36 Housing 38 Blade Cover 40 Connection 42 Nozzle 50 Grinding Equipment 52 Chuck table (holding table) 52a Holding surface 54 Grinding unit 56 Spindle 58 Wheel mount 60 Grinding Wheel 62 Wheel base 64 Grinding wheel (grinding wheel) 66 Abrasive grain 68 Bonding material (bonding agent) 70 Volume expansion particles

Claims

1. A grindstone for processing a workpiece, The abrasive grains include a binder that fixes the abrasive grains, The grinding wheel is characterized in that the binder contains volume expansion particles whose volume expands during machining of the workpiece.

2. 2. The grindstone according to claim 1, wherein the content of the volume expansion particles is 3.0 vol % or more and 14.0 vol % or less.

3. 3. The grindstone according to claim 1, wherein the average particle size of the volume-expansion particles is smaller than the average particle size of the abrasive grains.

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