Grinding wheel and method for producing the same

Abstract

To provide a grinding wheel that achieves longer life while securing required grinding performance, and a method for producing the same.SOLUTION: A grinding wheel 1 includes a plurality of abrasive grains 2, bond bridges 3 that interconnect the abrasive grains 2, and pore regions 4 arranged between the abrasive grains 2. The bond bridges 3 are composed of vitrified bond. The volume ratio of the pore regions 4 relative to the entire grinding wheel 1 is 50 vol.% or more. The pore regions 4 include a plurality of hollow bodies 41 and a plurality of simple pores 42. The hollow bodies 41 have an outer shell 411 composed of ceramics. The simple pores 42 are enclosed, at least in part, by the bond bridges 3.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a grinding wheel and a method for manufacturing the same. [Background technology]

[0002] For example, a grinding wheel with high porosity used for grinding semiconductor wafers is known, as disclosed in Patent Document 1. The grinding wheel described in Patent Document 1 includes abrasive grains, bond bridges that bond the abrasive grains together, and pores surrounded by the bond bridges, and has a pore volume ratio of 65 to 90 volume %. By making the grinding wheel have a high porosity, it is possible to ensure the desired grinding performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6737975 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the grinding wheel described in Patent Document 1, the pores are surrounded by bond bridges. Therefore, if the pore volume ratio of the grinding wheel is set to 50 volume % or more in order to improve the grinding performance, the grinding wheel is easily worn. The wear of the grinding wheel shortens the life of the grinding wheel. Therefore, it can be said that there is room for further improvement in terms of suppressing the wear of the grinding wheel and extending the life of the grinding wheel.

[0005] The present invention has been made in view of the above background, and aims to provide a grinding wheel that can achieve a long life and ensure the desired grinding performance, and a manufacturing method thereof. [Means for solving the problem]

[0006] One aspect of the present invention is a method for manufacturing a grinding machine comprising: a bond bridge formed of a vitrified bond and bonding the abrasive grains together; a pore region disposed between the abrasive grains; A grinding wheel comprising: The volume ratio of the pore region to the entire grinding wheel is 50 volume % or more, The pore region is A plurality of hollow bodies each having an outer shell made of ceramics; a plurality of simple pores at least partially surrounded by said bond bridges; The grinding wheel has a

[0007] Another aspect of the present invention is a method for producing the grinding wheel, comprising the steps of: a mixing step of mixing the abrasive grains, the vitrified bond, the hollow body, and a pore-forming agent to obtain a mixture; A firing step of firing the mixture at a temperature equal to or higher than the softening point of the vitrified bond, In the firing step, the pore-forming agent disappears, thereby forming the simple pores. Effect of the Invention

[0008] In the grinding wheel, the volume ratio of the pore region to the entire grinding wheel is 50% by volume or more. The pore region has hollow bodies in addition to simple pores. Therefore, when the volume ratio of the pore region to the entire grinding wheel is set to 50% by volume or more, the wear of the grinding wheel can be suppressed by forming a part of the pore region with hollow bodies, compared to when the pore region is formed only of simple pores. As a result, the life of the grinding wheel can be extended.

[0009] If the pore region were composed only of hollow bodies, the pressure on the abrasive grains would be reduced due to the shell of the hollow bodies coming into contact with the workpiece. The reduced pressure on the abrasive grains would result in a reduction in grinding performance. However, in the grinding wheel, the pore region includes not only hollow bodies but also simple pores. Therefore, compared to when the pore region is entirely composed of hollow bodies, the pore region is composed of hollow bodies and simple pores, which makes it possible to suppress the reduction in grinding performance caused by the shell of the hollow bodies. In other words, the desired grinding performance can be ensured.

[0010] The method for manufacturing a grinding wheel uses both a hollow body and a pore-forming agent to manufacture the grinding wheel. Therefore, the porous region of the manufactured grinding wheel has hollow bodies in addition to simple pores. Therefore, even if the volume ratio of the porous region to the entire grinding wheel is set to 50 volume % or more, the wear of the grinding wheel can be suppressed. Therefore, a grinding wheel that can be extended in life can be manufactured. Furthermore, the desired grinding performance can be ensured.

[0011] As described above, according to the above-described aspect, it is possible to provide a grinding wheel that can have a long life and ensure desired grinding performance, and a manufacturing method thereof. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing how the back surface of a semiconductor wafer is ground by a wafer grinding wheel having a grinding stone fixed thereto in the first embodiment. [Diagram 2] FIG. 4 is an external view of the wafer grinding wheel to which a grinding stone is fixed in the first embodiment, taken along the line II in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2 . [Figure 4] FIG. 2 is an enlarged cross-sectional view of a grinding wheel according to the first embodiment. [Diagram 5] 3 is a flowchart showing a method for manufacturing a grinding wheel in the first embodiment. [Figure 6]4 is a graph showing the relationship between the porosity of the grinding wheel and the wear rate of the grinding wheel in Experimental Example 1. [Figure 7] 13 is a graph showing the relationship between the hollow body ratio and the bending strength of the grinding wheel in Experimental Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Embodiment 1) 1. Applications of grinding wheels The grinding wheel is applied to a wafer grinding wheel used for grinding semiconductor wafers. The semiconductor wafer to be ground is a wafer having a high Knoop hardness and Young's modulus, such as a SiC wafer. The semiconductor wafer to be ground can be a wafer having a Knoop hardness and Young's modulus similar to that of a SiC wafer, in addition to a SiC wafer.

[0014] 2. Configuration of wafer grinding wheel 10 A wafer grinding wheel 10 to which a grinding stone 1 is applied will be described with reference to Figures 1 to 3. As shown in Figure 1, the wafer grinding wheel 10 is used to grind a semiconductor wafer 11 such as a SiC wafer.

[0015] 2 and 3, the wafer grinding wheel 10 includes a base metal 101 and a plurality of grinding stones 1 fixed to the base metal 101. The base metal 101 is formed into a disk shape from a metal material such as steel, titanium alloy, aluminum alloy, etc. The base metal 101 is formed with a shaft hole 102 that is fitted onto a rotating shaft of a grinding device (not shown).

[0016] Each of the grinding wheels 1 is formed in an arc shape. The grinding wheels 1 are arranged in a circumferential direction in an annular shape on the outer periphery of the surface of the base metal 101 that faces one side of the opening direction of the shaft hole 102.

[0017] 1, a wafer grinding wheel 10 is rotated around the rotation axis of the grinding device to rotate a semiconductor wafer 11 fixed to a chuck table 12. Then, the wafer grinding wheel 10 is moved in the direction of arrow M in Fig. 1, and the grinding stone 1 is brought into sliding contact with the back surface of the semiconductor wafer 11, thereby grinding the semiconductor wafer 11.

[0018] 3. Overview of the composition of grinding wheel 1 The outline of the configuration of the grinding wheel 1 will be described with reference to Fig. 4. As shown in Fig. 4, the grinding wheel 1 of this embodiment includes a plurality of abrasive grains 2, bond bridges 3 that bond the abrasive grains 2 together, and porous regions 4 arranged between the abrasive grains 2. The volume ratio of the porous regions 4 to the entire grinding wheel 1 is 50 volume % or more. The porous regions 4 include a plurality of hollow bodies 41 having an outer shell 411 made of ceramics, and a plurality of simple pores 42 at least partially surrounded by the bond bridges 3.

[0019] 4. Detailed configuration of grinding wheel 1 The detailed configuration of the grinding wheel 1 will be described with reference to FIG. 4. For example, diamond grains or CBN (cubic boron nitride) grains can be used as the abrasive grains 2 constituting the grinding wheel 1. When the target semiconductor wafer 11 is a SiC wafer, diamond grains are suitable for the abrasive grains 2. In this embodiment, the abrasive grains 2 are diamond grains. The median diameter of the abrasive grains 2 can be, for example, 5 to 15 μm.

[0020] In order to ensure the desired grinding performance for the hard semiconductor wafer 11, it is preferable that the abrasive grains 2 have a space between each other. Therefore, the volume ratio of the abrasive grains 2 to the entire grinding wheel 1 (hereinafter, simply referred to as "abrasive grain ratio") is set to 25 volume % or less. Moreover, the abrasive grain ratio is 4 volume % or more.

[0021] The bond bridge 3 is made of a vitrified bond. As shown in Fig. 4, the bond bridge 3 made of a vitrified bond bonds the abrasive grains 2 together. In particular, the bond bridge 3 bridges between the abrasive grains 2. Therefore, a part of the surface of the abrasive grain 2 is bonded to the bond bridge 3. In this manner, the abrasive grain 2 is held by the bond bridge 3. The bond bridge 3 can be mainly composed of, for example, silicate glass or borosilicate glass.

[0022] The volume ratio of the bond bridge 3 to the entire grinding wheel 1 (hereinafter, simply referred to as "bond ratio") is 10 volume % or more and 30 volume % or less.

[0023] The pore regions 4 are disposed between the abrasive grains 2. The volume ratio of the pore regions 4 to the entire grinding wheel 1 (hereinafter, simply referred to as "pore ratio") is 50 volume % or more. The pore ratio is preferably 60 volume % or more, and more preferably 70 volume % or more. Moreover, the pore ratio is 85 volume % or less.

[0024] The pore region 4 has a plurality of hollow bodies 41 and a plurality of simple pores 42. In other words, the pore volume is the sum of the volume of the outer shape of the plurality of hollow bodies 41 and the volume of the plurality of simple pores 42.

[0025] The hollow body 41 has an outer shell 411 made of ceramics. In the hollow body 41, the inside of the outer shell 411 is filled with a predetermined gas such as air or nitrogen. The outer shell 411 of the hollow body 41 is made of, for example, a mullite material or a glass material. In this embodiment, the outer shell 411 is made of a mullite material. In addition, the outer shell 411 has a strength higher than that of the bond bridge 3.

[0026] In this embodiment, the outer shell 411 of the hollow body 41 is spherical. The hollow body 41 has an outer shell 411 having only one type of outer diameter. In this case, all the hollow bodies 41 have the same outer diameter. However, the hollow bodies 41 may have a plurality of outer diameters.

[0027] In this embodiment, the outer diameter of hollow body 41 is larger than the median diameter of abrasive grains 2. Moreover, the outer diameter of hollow body 41 is preferably larger than the maximum grain size of abrasive grains 2. The outer diameter of hollow body 41 may be, for example, 40 to 90 μm. Moreover, the thickness of outer shell 411 of hollow body 41 is 1 to 7 μm.

[0028] The hollow bodies 41 are joined by bond bridges 3 formed of a vitrified bond. Therefore, the hollow bodies 41 are bridged between other hollow bodies 41 or abrasive grains 2 by the bond bridges 3. Some of the hollow bodies 41 may be in contact with the abrasive grains 2.

[0029] The simple pores 42 are formed by the disappearance of a pore-forming agent, which will be described later. The simple pores 42 do not have a component such as the outer shell 411 of the hollow body 41, and are composed of pores only. The simple pores 42 may be configured to form continuous pores that are continuous with other pores, or may be configured to form independent pores. A part of the simple pores 42 may be configured to form continuous pores, and the remaining part of the simple pores may be configured to form independent pores.

[0030] In this embodiment, the simple pore 42 is surrounded by any one of the abrasive grains 2, the bond bridge 3, and the hollow body 41, which are other elements constituting the grinding wheel 1. In other words, the outer wall of the simple pore 42 is any one of the abrasive grains 2, the bond bridge 3, and the hollow body 41. At least a part of the simple pore 42 is surrounded by the bond bridge 3. That is, a part of the simple pore 42 is adjacent to the bond bridge 3 and surrounded by the surface of the bond bridge 3. Also, a part of the simple pore 42 is adjacent to the abrasive grains 2 and surrounded by the surface of the abrasive grains 2. Also, a part of the simple pore 42 is adjacent to the hollow body 41 and surrounded by the surface of the outer shell 411 of the hollow body 41.

[0031] The maximum inscribed circle diameter in at least a portion of the cross section of the simple pores 42 constituting the continuous pores or the closed pores is larger than the median diameter of the abrasive grains 2. Furthermore, the maximum inscribed circle diameter in at least a portion of the cross section of the simple pores 42 constituting the continuous pores or the closed pores is larger than the maximum grain size of the abrasive grains 2. The maximum inscribed circle diameter in at least a portion of the cross section of the simple pores 42 constituting the continuous pores or the closed pores can be, for example, 20 to 100 μm.

[0032] The pore ratio is as described above. The volume ratio of the hollow bodies 41 to the entire pore region 4 is equal to or less than the volume ratio of the simple pores 42 to the entire pore region 4. More specifically, the volume ratio of the hollow bodies 41 to the entire pore region 4 is 10 to 35 volume %. Preferably, the volume ratio of the hollow bodies 41 to the entire pore region 4 is 18 to 30 volume %.

[0033] 5. Overview of manufacturing method for grinding wheel 1 Next, an outline of the manufacturing method of the grinding wheel 1 of this embodiment will be described with reference to FIG. 5. The manufacturing method of the grinding wheel 1 of this embodiment includes at least a mixing step S1 and a firing step S3. In the mixing step S1, a mixture is obtained by mixing the abrasive grains 2, a vitrified bond made of glass, a hollow body 41, and a pore-forming agent (not shown). In the firing step S3, the mixture obtained in the mixing step S1 is fired at a temperature equal to or higher than the softening point of the vitrified bond. In the firing step S3, the pore-forming agent disappears, thereby forming simple pores 42. The simple pores 42 include, in addition to the pores formed by the disappearance of the pore-forming agent in the firing step S3, for example, pores formed in the mixture in the mixing step S1 that remain in the grinding wheel 1 manufactured through the firing step S3.

[0034] 6. Detailed manufacturing method of grinding wheel 1 A detailed manufacturing method of the grinding wheel 1 will be described with reference to Fig. 5. In this embodiment, the manufacturing method of the grinding wheel 1 includes a mixing step S1, a molding step S2, and a firing step S3.

[0035] In the mixing step S1, a mixture is obtained by mixing the abrasive grains 2, a vitrified bond made of glass, hollow bodies 41, and a pore-forming agent. In the mixing step S1, a binder can be added as necessary. In the mixture obtained in the mixing step S1, the ratio of the total volume of the hollow bodies 41 and the pore-forming agent to the total volume of the mixture is 40 volume% or more. The ratio of the total volume is preferably 50 volume% or more, and more preferably 60 volume% or more. The ratio of the total volume is 80 volume% or less.

[0036] Moreover, the outer diameter of the pore-forming agent is larger than the median diameter of the abrasive grains 2. Moreover, the outer diameter of the pore-forming agent is larger than the maximum particle diameter of the abrasive grains 2. As the pore-forming agent, for example, carbon, resin balls made of synthetic resin, walnut powder, etc. can be adopted. In this embodiment, the pore-forming agent is carbon. Moreover, in this embodiment, the pore-forming agent is composed of only one type of outer diameter.

[0037] In the mixture obtained in the mixing step S1, the volume of the hollow bodies 41 is equal to or less than the volume of the pore-forming agent. More specifically, in the mixture obtained in the mixing step S1, the volume ratio of the hollow bodies 41 to the total volume of the hollow bodies 41 and the pore-forming agent is 20 to 55 volume %, and preferably 30 to 50 volume %. Here, by adjusting the ratio of the hollow bodies 41 and the pore-forming agent contained in the mixture in the mixing step S1, the volume ratio of the hollow bodies 41 to the entire pore region 4 of the grinding wheel 1 to be manufactured can be set to a desired ratio. Note that the standard for the volume of the hollow bodies 41 added as a material is the volume including the outer shell 411.

[0038] Next, in the molding step S2, the mixture obtained in the mixing step S1 is filled into a mold of a desired shape, and then pressure-molded using a press device.

[0039] Next, in the firing step S3, the mixture compact formed in the forming step S2 is fired at a temperature equal to or higher than the softening point of the vitrified bond. In the firing step S3, the pressurized compact is fired at a temperature equal to or higher than the softening point of the vitrified bond, thereby manufacturing the grinding wheel 1. In this embodiment, the softening temperature of the outer shell 411 of the hollow body 41 is higher than the softening temperature of the vitrified bond. In other words, the firing temperature in the firing step S3 is equal to or higher than the softening temperature of the vitrified bond and lower than the softening temperature of the outer shell 411 of the hollow body 41.

[0040] As described above, in the firing step S3, the pore-forming agent disappears, and simple pores 42 are formed in the areas where the pore-forming agent was present. As a result, the grinding wheel 1 described above is completed.

[0041] 7. Effects Next, the effects of this embodiment will be described. In the grinding wheel 1, the porosity is 50% by volume or more. The porosity region 4 has hollow bodies 41 in addition to simple pores 42. Therefore, when the porosity is 50% by volume or more, the wear of the grinding wheel 1 can be suppressed by forming a part of the porosity region 4 with the hollow bodies 41, compared to when the porosity region 4 is formed only with simple pores 42. In other words, even when the bond bridge 3 has a relatively thin portion, the strength of the grinding wheel 1 can be improved by the outer shell 411 of the hollow bodies 41. Therefore, the life of the grinding wheel 1 can be extended.

[0042] If the pore region 4 were composed only of the hollow bodies 41, the outer shell 411 of the hollow bodies 41 would come into contact with the workpiece, which could reduce the pressure on the abrasive grains 2. The reduction in pressure on the abrasive grains 2 could reduce the grinding performance. However, in the grinding wheel 1, the pore region 4 includes not only the hollow bodies 41 but also the simple pores 42. Therefore, compared to the case where the entire pore region 4 is composed of the hollow bodies 41, the pore region 4 is composed of the hollow bodies 41 and the simple pores 42, which can suppress the reduction in grinding performance caused by the outer shell 411 of the hollow bodies 41. In other words, the desired grinding performance can be ensured.

[0043] The porosity is 60% by volume or more. Therefore, the increase in the surface pressure applied to the grinding wheel 1 during grinding can be suppressed, and the load during grinding can be suppressed from becoming too large. In addition, the relatively high porosity makes it easier to discharge chips. As a result, the grinding performance can be further improved. In other words, the sharpness of the grinding wheel 1 can be further improved.

[0044] In this embodiment, the porosity is 70% by volume or more, which can further improve the grinding performance.

[0045] The porosity is 85% by volume or less, which ensures the strength of the grinding wheel 1.

[0046] The volume ratio of the hollow bodies 41 to the entire porous region 4 is equal to or less than the volume ratio of the simple pores 42 to the entire porous region 4. Therefore, it is possible to suppress a decrease in grinding performance caused by an excessively high volume ratio of the hollow bodies 41 to the entire porous region 4. As a result, it is possible to reliably ensure grinding performance. In addition, it is possible to suppress an excessive amount of the hollow bodies 41 added as a material when manufacturing the grinding wheel 1, so that it is possible to suppress cracking of the hollow bodies 41 during the manufacturing process. Therefore, it is possible to improve the manufacturability of the grinding wheel 1.

[0047] In this embodiment, the volume ratio of the hollow bodies 41 to the entire pore region 4 is 10 to 35 volume %. Therefore, as described in Experimental Example 2 below, the strength and abrasive grain retention of the grinding wheel 1 can be increased. As a result, wear of the grinding wheel 1 and the falling off of the abrasive grains 2 can be suppressed, and the life of the grinding wheel 1 can be extended. In addition, since the volume ratio of the hollow bodies 41 to the entire pore region 4 is 35 volume % or less, the amount of the hollow bodies 41 added as a material when manufacturing the grinding wheel 1 can be prevented from becoming too large, and the hollow bodies 41 can be prevented from cracking during the manufacturing process of the grinding wheel 1. In addition, the reduction in grinding performance caused by the volume ratio of the hollow bodies 41 to the entire pore region 4 becoming too high can be suppressed. Therefore, the grinding performance can be reliably ensured.

[0048] Moreover, the volume ratio of the hollow bodies 41 to the entire pore region 4 is preferably 18 to 30% by volume. In this case, as will be described in Experimental Example 2 below, it is possible to more reliably achieve a longer life.

[0049] The outer diameter of the hollow body 41 is larger than the median diameter of the abrasive grains 2. This makes it easier to increase the distance between the abrasive grains 2 and to reduce the grinding resistance during grinding. As a result, it is easier to improve the grinding performance.

[0050] Moreover, the outer diameter of the hollow body 41 is preferably larger than the maximum grain size of the abrasive grains 2. In this case, it is easier to further increase the intervals between the abrasive grains 2, and the grinding performance can be further improved.

[0051] The outer diameter of the hollow body 41 can be set to 40 to 90 μm. In this case, the strength of the grinding wheel 1 can be ensured while increasing the intervals between the abrasive grains 2.

[0052] The thickness of the outer shell 411 of the hollow body 41 is 1 to 7 μm. Therefore, the effect of the outer shell 411 during grinding can be reduced, while the shape retention of the grinding wheel 1 can be sufficiently ensured. As a result, grinding performance can be reliably ensured, and a long life can be reliably achieved.

[0053] The abrasive grain ratio is 25 volume % or less, which makes it easy to increase the intervals between the abrasive grains 2 and to reduce the grinding resistance during grinding.

[0054] The abrasive grain ratio is 4 volume % or more. Therefore, the number of abrasive grains 2 acting on the workpiece during grinding can be secured. As a result, the desired grinding performance can be secured.

[0055] The bond ratio is 10% by volume or more and 30% by volume or less. Therefore, the porosity ratio can be increased reliably while reliably ensuring the strength of the grinding wheel 1. As a result, the life span can be extended reliably and the grinding performance can be improved reliably.

[0056] The hollow body 41 has an outer shell 411 having only one type of outer diameter. Therefore, the uniformity of the grindstone texture can be improved, and the processing quality during grinding can be stabilized.

[0057] Moreover, the pore region 4 has simple pores 42. This can reliably ensure the self-sharpening action of the grinding wheel 1. As a result, it is easy to reliably ensure grinding performance.

[0058] In this embodiment, some of the simple pores 42 are adjacent to the hollow body 41 and are surrounded by the surface of the outer shell 411 of the hollow body 41. This makes it easier to increase the porosity ratio, which in turn makes it easier to improve the grinding performance.

[0059] The maximum inscribed circle diameter in at least a part of the cross section of the simple pore 42 is larger than the median diameter of the abrasive grains 2. This makes it easier to further increase the intervals between the abrasive grains 2. As a result, it is easier to further improve the grinding performance.

[0060] In this embodiment, the maximum inscribed circle diameter in the cross section of at least a portion of the simple pore 42 is larger than the maximum grain size of the abrasive grains 2. Therefore, it is easier to make the intervals between the abrasive grains 2 larger.

[0061] In the manufacturing method of the grinding wheel 1, the grinding wheel 1 is manufactured using both the hollow bodies 41 and the pore-forming agent. Therefore, the porous region 4 of the manufactured grinding wheel 1 has the hollow bodies 41 in addition to the simple pores 42. Therefore, even if the porosity is set to 50 volume % or more, the wear of the grinding wheel 1 can be suppressed. Therefore, it is possible to manufacture a grinding wheel 1 that can achieve a long life. Furthermore, it is possible to ensure the desired grinding performance.

[0062] In this embodiment, the pore region 4 is formed by the hollow bodies 41 and the pore-forming agent. Therefore, in the manufactured grinding wheel 1, the sizes of the hollow bodies 41 and the simple pores 42 can be easily controlled to desired sizes. As a result, the uniformity of the grinding wheel structure can be improved, and the processing quality in grinding can be stabilized.

[0063] The outer diameter of the pore-forming agent is larger than the median diameter of the abrasive grains 2. Therefore, it is easy to increase the intervals between the abrasive grains 2 of the grinding wheel 1 to be manufactured.

[0064] In the mixture obtained in the mixing step S1, the volume of the hollow bodies 41 is equal to or less than the volume of the pore-forming agent, so that the volume ratio of the hollow bodies 41 to the entire pore region 4 becomes too high in the manufactured grinding wheel 1, thereby preventing a decrease in grinding performance.

[0065] In the mixture obtained in the mixing step S1, the volume ratio of the hollow bodies 41 to the total volume of the hollow bodies 41 and the pore forming agent is 20 to 55 volume %. Therefore, as will be described in Experimental Example 2 below, the strength and abrasive grain retention of the grinding wheel 1 to be manufactured can be reliably increased. In addition, the amount of the hollow bodies 41 added as a material when manufacturing the grinding wheel 1 can be prevented from becoming too large, and the hollow bodies 41 can be prevented from cracking during the manufacturing process of the grinding wheel 1. In addition, the deterioration of grinding performance caused by the volume ratio of the hollow bodies 41 to the entire pore region 4 becoming too high can be prevented.

[0066] In the mixture obtained in the mixing step S1, the ratio of the total volume of the hollow body 41 and the pore-forming agent to the total volume of the mixture is 40% by volume or more. Therefore, in the grinding wheel 1 to be manufactured, the porosity ratio is likely to be 50% by volume or more. Therefore, the grinding performance of the grinding wheel 1 to be manufactured can be improved. In addition, in the mixture obtained in the mixing step S1, the ratio of the total volume of the hollow body 41 and the pore-forming agent to the total volume of the mixture is preferably 50% by volume or more. In this case, the grinding performance of the grinding wheel 1 to be manufactured can be further improved. In addition, in the mixture obtained in the mixing step S1, the ratio of the total volume of the hollow body 41 and the pore-forming agent to the total volume of the mixture is more preferably 60% by volume or more. In this case, the grinding performance of the grinding wheel 1 to be manufactured can be further improved.

[0067] The outer shell 411 of the hollow body 41 is spherical. Therefore, the strength of the outer shell 411 can be made relatively high, and the hollow body 41 is less likely to crack during the manufacture of the grinding wheel 1. As a result, the productivity can be improved.

[0068] As described above, according to the present embodiment, it is possible to provide a grinding wheel 1 capable of achieving a long life and ensuring desired grinding performance, and a manufacturing method thereof.

[0069] (Experimental Example 1) In this example, as shown in the graph of Fig. 6, the grinding wheel of the example having a hollow body and simple pores with the same basic structure as in the first embodiment, and the grinding wheel of the comparative example having the same basic structure as in the first embodiment but with the pore region formed only by simple pores were used to obtain the relationship between the pore ratio and the grinding wheel wear rate in grinding a semiconductor wafer, which is a workpiece. In addition, the value of a predetermined feed rate was set to a feed rate index 1, and an experiment was performed at the feed rate index 1 or the feed rate index 2, which is a feed rate twice as fast as the feed rate index 1. In addition, the grinding wheel wear rate is the ratio of the thickness (mm) worn by the grinding wheel by grinding divided by the thickness (mm) removed by grinding of the semiconductor wafer. For example, when the worn thickness of the grinding wheel is 1 / 2 of the thickness removed by grinding of the semiconductor wafer, the grinding wheel wear rate is 50%.

[0070] In this example, the grinding wheel of the embodiment having a hollow body and simple pores is a grinding wheel manufactured using both a hollow body and a pore forming agent. In the grinding wheel of the embodiment, the volume ratio of the hollow body to the entire pore region is 18 to 30 volume %. In addition, the grinding wheel of the comparative example in which the pore region is formed only by simple pores is a grinding wheel manufactured using a pore forming agent without using a hollow body.

[0071] As shown in the graph of FIG. 6, when the porosity ratio is about 74% by volume, the grinding wheel of the embodiment has a significantly smaller grinding wheel wear rate than the grinding wheel of the comparative example. In addition, when the porosity ratio is 74% by volume or more, the grinding wheel of the comparative example has a grinding wheel wear rate of 50% or more, and some grinding wheels have a grinding wheel wear rate that is significantly more than 100%, while all grinding wheels of the embodiment have a grinding wheel wear rate of less than 40%. From this result, it is considered that the strength of the grinding wheel is improved by providing a hollow body in the porosity region. In other words, it can be said that in the grinding wheel, by providing a hollow body in the porosity region, even if the porosity ratio is relatively high, the wear of the grinding wheel can be suppressed and the life can be extended.

[0072] (Experimental Example 2) In this example, as shown in the graph of FIG. 7, a relationship between the hollow body ratio and bending strength was obtained using a plurality of grinding wheels having the same basic structure as in the first embodiment but different hollow body ratios. Here, the hollow body ratio means the ratio of the volume of the hollow body to the total volume of the hollow body and the pore forming agent added as materials when manufacturing the grinding wheel. The bending strength was obtained by a four-point bending test based on "JISR1601:2008 Room Temperature Bending Strength Test Method for Fine Ceramics". In general, the higher the bending strength value, the higher the tissue strength of the grinding wheel and the abrasive grain retention force. Therefore, in this example, as shown in FIG. 7, a predetermined bending strength value is set as a bending strength index of 1, and a bending strength index of 1 or more is used as a standard indicating that the wheel has sufficient tissue strength and abrasive grain retention force when used as a grinding wheel for semiconductor wafer grinding. Therefore, the hollow body ratio that satisfies the standard was obtained from the results of this experiment.

[0073] In this example, the porosity of each sample was also confirmed. The porosity was determined by measuring the volume and weight of the grinding wheel produced. In the graph of FIG. 7, the circles represent plots of the porosity of each sample, and the squares represent plots of the bending strength of each sample. The graph of FIG. 7 also shows approximation curves for these plots. Specifically, the approximation curve for the porosity is shown by a dashed line, and the approximation curve for the bending strength is shown by a solid line.

[0074] From the results shown in the graph of FIG. 7, it can be seen that the bending strength does not meet the above criteria in both cases where the hollow body ratio is too low and where the hollow body ratio is too high. On the other hand, from the approximation curve of bending strength shown in the graph of FIG. 7, it is presumed that the above criteria will be met by setting the hollow body ratio to 20-55% by volume, even when the porosity ratio is 70% by volume or more. Therefore, it is presumed that the strength and abrasive grain retention of the grinding wheel manufactured by setting the hollow body ratio to 20-55% by volume can be strengthened, and a long life can be achieved. Also, from the graph of FIG. 7, it can be seen that the above criteria will be met by setting the hollow body ratio to 30-50% by volume, even when the porosity ratio is 70% by volume or more. Therefore, by setting the hollow body ratio to 30-50% by volume, it is possible to reliably strengthen the strength and abrasive grain retention of the grinding wheel manufactured by volume. As a result, a long life can be reliably achieved. Furthermore, since it is possible to prevent the amount of hollow bodies added when manufacturing the grinding wheel from becoming too large, it is possible to prevent the hollow bodies from cracking during the manufacturing process of the grinding wheel.

[0075] In addition, it was estimated that the volume ratio of the hollow bodies to the entire pore region of a grinding wheel manufactured with a hollow body ratio of 20 to 55% by volume was 10 to 35% by volume. Therefore, it was estimated that the strength and grain retention of the grinding wheel can be increased when the volume ratio of the hollow bodies to the entire pore region is 10 to 35% by volume. In addition, the volume ratio of the hollow bodies to the entire pore region of a grinding wheel manufactured with a hollow body ratio of 30 to 50% by volume was 18 to 30% by volume. Therefore, when the volume ratio of the hollow bodies to the entire pore region is 18 to 30% by volume, the strength and grain retention of the grinding wheel can be reliably increased.

[0076] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist of the present invention. [Explanation of symbols]

[0077] 1...grinding wheel, 2...abrasive grain, 3...bond bridge, 4...pore region, 41...hollow body, 42...simple pore, 411...outer shell, S1...mixing step, S3...firing step

Claims

1. A plurality of abrasive grains; a bond bridge formed of a vitrified bond and bonding the abrasive grains together; a pore region disposed between the abrasive grains; A grinding wheel comprising: The volume ratio of the pore region to the entire grinding wheel is 50 volume % or more, The pore region is A plurality of hollow bodies each having an outer shell made of ceramics; a plurality of simple pores at least partially surrounded by said bond bridges; A grinding wheel having the above structure.

2. 2. The grinding wheel according to claim 1, wherein a portion of said simple pore is adjacent to said hollow body and surrounded by a surface of said outer shell of said hollow body.

3. 3. The grinding wheel according to claim 1, wherein an outer diameter of the hollow body is larger than a median diameter of the abrasive grains.

4. 4. The grinding wheel according to claim 3, wherein an outer diameter of the hollow body is larger than a maximum grain size of the abrasive grains.

5. The grinding wheel according to claim 3 , wherein a maximum inscribed circle diameter in a cross section of at least a part of the simple pores is larger than a median diameter of the abrasive grains.

6. 3. The grinding wheel according to claim 1, wherein a volume ratio of said hollow bodies to the entire pore region is equal to or less than a volume ratio of said simple pores to the entire pore region.

7. 7. The grinding wheel according to claim 6, wherein a volume ratio of said hollow bodies to the entire pore region is 10 to 35 volume %.

8. 3. The grinding wheel according to claim 1, wherein a volume ratio of the porous region to the entire grinding wheel is 70 volume % or more.

9. 3. The grinding wheel according to claim 1, wherein the thickness of the outer shell of the hollow body is 1 to 7 μm.

10. 3. The grinding wheel according to claim 1, wherein the hollow body has the outer shell having only one outer diameter.

11. A method for producing the grinding wheel according to claim 1 or 2, comprising the steps of: a mixing step of mixing the abrasive grains, the vitrified bond, the hollow body, and a pore-forming agent to obtain a mixture; A firing step of firing the mixture at a temperature equal to or higher than the softening point of the vitrified bond, In the firing step, the pore-forming agent is eliminated, thereby forming the simple pores.

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