JP6737975B1 - Method for manufacturing high porosity vitrified grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a vitrified grindstone capable of stably manufacturing a vitrified grindstone having a high porosity by communicating pores. SOLUTION: By a freeze vacuum drying step P3, a molded body 28 in which a plurality of frozen particles 30 are generated is placed under vacuum, whereby the frozen particles 30 in the molded body 28 are sublimated and dried. After the sublimation of the frozen particles 30, the pores 32 communicating with each other are formed. Since the pores 32 formed in this way do not disappear during manufacturing and the shrinkage of the molded body 28 is suppressed, the high porosity vitrified grindstone 10 having a high porosity due to the communicating pores 32 is stably manufactured. it can. [Selection diagram]

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a vitrified grindstone having a high porosity due to continuous ventilation holes.

Generally, when grinding a semiconductor wafer, the abrasive grains are bonded by vitrified bonds to enhance the coercive force of the abrasive grains, and 75% by volume to 95% by volume of independent pores is generated in order to appropriately generate the self-generated action of the cutting edge of the abrasive grains. A multi-pore vitrified grindstone having a high porosity of about 10% has been proposed. For example, the vitrified grindstones described in Patent Document 1 and Patent Document 2 are such.

According to such a high porosity vitrified grindstone, since the porosity is high, the autogenous action of the cutting edge of the abrasive grains is obtained to enhance the grinding performance, and the high porosity is achieved by the independent porosity. Therefore, there is an advantage that the strength of the grindstone can be secured and the grinding can be performed with a sufficient grinding pressure.

By the way, the high-porosity vitrified grindstone as described in Patent Document 1 is formed into a molded body by press-molding a grindstone raw material obtained by kneading an abrasive grain and a vitrified bond with an organic pore-forming agent such as polystyrene particles, It is manufactured by burning the molded body to burn off the organic pore-forming agent. Therefore, in the high-porosity vitrified grindstone obtained by firing, a large part of the pores are independent pores, that is, closed pores. For this reason, the cutting waste generated in the grinding process may be accumulated in the independent pores and the grinding performance may not be sufficiently obtained.

On the other hand, in Patent Document 3, a surfactant is used instead of the pore-forming agent, and abrasive grains, vitrified bonds, a solidifying agent (gelling agent), water, and a surfactant are mixed to form a meringue-like foam. After the material is obtained, the foamed material is cooled in a molding die to form a molded body, and the dried molded body is fired and further immersed in a liquid resin to form a bond bridge which is an outer shell surrounding the pores. There has been proposed a manufacturing method for obtaining a vitrified grindstone having a high porosity of 50% by volume to 98% by volume, the strength of which is increased by coating a resin coating layer on the.

JP, 2006-001007, A JP, 2017-080847, A JP, 2007-290101, A

However, in the vitrified grindstone obtained by the above-mentioned manufacturing method, since it is not an independent pore, the deformation phenomenon of the bond bridge progresses in the process of drying the molded body molded from the meringue-shaped foam material, and the molded body is It may shrink, which makes it difficult to manufacture a product having a stable shape.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a vitrified grindstone capable of stably manufacturing a vitrified grindstone having a high porosity by continuous ventilation holes. Especially.

The present inventors have made various studies in the background of the above circumstances, abrasive grains, vitrified bond, and, after obtaining a grindstone raw material slurry by mixing a gelling agent in water and mixed, in the molding die A molded body is created by gelling the whetstone raw material slurry, and then a large number of frozen particles are generated in the frozen molded body by freezing the molded body, and the generated many frozen particles are sublimated under vacuum. It was found that a vitrified grindstone having a sufficient porosity and a high porosity can be obtained by forming a multi-pore molded body having continuous pores and firing the molded body. .. The present invention has been made based on such knowledge.

That is, the gist of the present invention is (1) a method for producing a high porosity vitrified grindstone including a plurality of pores communicating with each other, wherein (2) a gellable water-soluble polymer is dissolved. A grinding stone material adjusting step of obtaining a grinding stone raw material slurry which is a mixed fluid of abrasive grains, vitrified bonds and water, and (2) a molding step of obtaining a compact by gelling the grinding stone raw material slurry using a molding die. (3) After the molding step, the molded body is frozen to generate a plurality of frozen particles inside the molded body, and the molded body in which the frozen particles are generated is placed under a vacuum, whereby the frozen particles are Freeze vacuum drying step of sublimating and drying the molded body, and (4) firing the molded body after the freeze vacuum drying step to bond the abrasive grains by the vitrified bond to obtain the high porosity. And a firing step for obtaining a vitrified grindstone.

According to the method for producing a high-porosity vitrified grindstone of the present invention, the freeze-vacuum drying step causes the molded body in which a plurality of frozen particles are generated to be placed under vacuum, whereby the frozen particles in the molded body are sublimated. After being sublimated and dried, a plurality of pores communicating with each other are formed after the sublimation of the frozen particles. For this reason, shrinkage of the compact is suppressed, so that a vitrified grindstone having a high porosity due to a plurality of pores communicating with each other can be stably manufactured.

Here, it is preferable that the pores are formed in the place where the frozen particles were present in the grindstone raw material slurry after the frozen particles were sublimated in the freeze vacuum drying step. The pores formed in this way do not disappear, and the shrinkage of the molded body that has been molded is suppressed.

Further, preferably, in the freeze-vacuum drying step, the frozen particles are generated in the gel-like grindstone raw material slurry that constitutes the molded body, whereby the abrasive grains and the vitrified bond form the frozen particles. The bond bridge, which is an outer shell that surrounds the pores, is formed from the green body portion by being collected in the surrounding green body portion in the firing step. As a result, the strength of the bond bridge is increased without the coating of the reinforcing resin coating layer, and the vitrified grindstone can be ground even if it has a high porosity.

Further, preferably, the high porosity vitrified grindstone has a pore volume ratio of 65% by volume to 90% by volume. As described above, since the high porosity vitrified grindstone has a pore volume ratio of 65% by volume to 90% by volume, the grinding efficiency and the strength of the grindstone are compatible with each other.

Further, the specific gravity of the high-porosity vitrified grindstone is preferably 0.34 to 1.48. In this way, a relatively light porosity vitrified grindstone having a specific gravity of 0.34 to 1.48 can be obtained.

Further, it is preferable that the abrasive grains have a central particle diameter (median diameter) smaller than the thickness of the bond bridge forming the outer shell of the pores. For this reason, since the abrasive grains are significantly smaller than the thickness of the bond bridge corresponding to the outer shell of the pores, the bond bridge locally has a non-pore vitrified grindstone structure and the strength is enhanced, so that the high porosity vitrified grindstone Grinding performance is improved, and a surface roughness suitable for grinding a semiconductor wafer is obtained.

It is a figure explaining the cup grindstone of the type which the high porosity vitrified grindstone manufactured by the manufacturing method of the high porosity vitrified grindstone which is one Example of this invention was adhered to the base metal. It is process drawing explaining the principal part of the manufacturing method of the high porosity vitrified grindstone shown in FIG. FIG. 3 is a diagram schematically showing a structural change in a compact of a high porosity vitrified grindstone in the manufacturing process shown in FIG. 2, showing (a) a state in which a grindstone raw material slurry is adjusted by a grindstone material adjusting step, and (b) Shows a state in which frozen particles were generated in the molded body by freezing in the freeze vacuum drying step, (c) shows a state in which frozen particles were sublimated in the molded body by vacuum drying in the freeze vacuum drying step, and (d) shows a state by the firing step. It is the figure which showed the state where the molded object was baked. It is the figure which showed the circular test piece (molded body) at the time of the same drying as the freeze-vacuum drying process of FIG. 2 on the left side, and the circular test piece (molded body) at the time of normal pressure drying on the right side. The left side is an optical micrograph showing an enlarged pore structure of the molded body before the firing step in FIG. 2, and the right side is an enlarged optical microscope photograph showing the pore structure of the molded body after the firing step. It is a figure. 3 is an SEM photograph showing an enlarged pore structure of a molded body after the firing step of FIG. 2. 3 is a SEM photograph showing a further enlarged pore structure of the molded body after the firing step of FIG. 2. It is a figure which shows the principal part and grinding ratio of the grindstone structure of sample 1-sample 10 and the sample 11-sample 12 for comparison produced by the process similar to the process shown in FIG. It is the figure which showed the sample 1-sample 12 of FIG. 8 in the two-dimensional coordinate of the horizontal axis which shows Vg/Vb, and the vertical axis which shows specific gravity (rho).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that, in the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the respective parts are not necessarily drawn accurately.

FIG. 1 shows a plurality of segment grindstones 10 which are an example of a high porosity vitrified grindstone according to an embodiment of the present invention. It is a perspective view which shows the cup grindstone 14 which was connected and fixed to. The segment grindstones 10 each include a grinding surface 16 continuous in an annular shape on the outer peripheral portion of the lower surface of the base metal 12.

The base metal 12 is made of a thick metal disc and is attached to a spindle of a grinding device (not shown) to rotate the cup grindstone 14. The cup grindstone 14 has an outer diameter of about 250 mm, for example, and the segment grindstone 10 has a width dimension of about 3 mm and a thickness dimension of about 5 mm, for example. In the segment grindstone 10, the grinding surface 16 is brought into sliding contact with a work material, for example, a silicon wafer as the base metal 12 rotates to grind or polish the work material to a thickness of the work material.

The segment grindstone 10 is manufactured, for example, by the manufacturing process shown in FIG. In the grindstone material adjusting step P1, the grindstone raw material slurry 18 of the segment grindstone 10 is adjusted. The grindstone raw material slurry 18 includes 17% by mass of superabrasive grains, for example, diamond abrasive grains 20, 15% by mass of vitrified bond 22, 3% by mass of water-soluble polysaccharide gelling agent 24 functioning as a primary binder, and functions as a pore forming agent. Water 26 is mixed at a ratio of 65% by mass, and the water-soluble polysaccharide gelling agent 24 is dissolved in the water 26 by heating at a melting temperature of about 90° C. or more, so that the water 26 has fluidity. Adjusted. The water-soluble polysaccharide gelling agent 24 corresponds to the gelable water-soluble polymer of the present invention.

FIG. 3A schematically shows the grindstone raw material slurry 18. The water-soluble polysaccharide gelling agent 24 dissolved in the water 26 is a fibrous polysaccharide molecule and is schematically shown in FIG. The polysaccharide molecules (the water-soluble polysaccharide gelling agent 24) are entangled with each other and stick to each other to form a network structure, so that many microscopic spaces for containing the water 26 are formed. Further, due to the entanglement of the polysaccharide molecules (the water-soluble polysaccharide gelling agent 24), when the temperature is lowered from the heating temperature, it loses fluidity and becomes a gel. As the water-soluble polysaccharide gelling agent 24, for example, curdlan, tamarind seed gum, kitansan gum+locust zane gum, sodium alginate, gelanga, pectin, carrageenan, gelatin, agar and the like are used.

The composition of the vitrified bond 22 is, for example, SiO ₂ of 50 wt% or more and 54 wt% or less, Al ₂ O ₃ of 13 wt% or more and 15 wt% or less, and B ₂ O ₃ of 17.5 wt% or more of 20. 5 wt% or less, RO (RO is one or more kinds of oxides selected from CaO, MgO, BaO, ZnO) 0.7 wt% or more and 6.5 wt% or less, R ₂ O (R ₂ O is One or more kinds of oxides selected from LiO ₂ , Na ₂ O and K ₂ O) is 0.0 wt% or more and 9.0 wt% or less, and P ₂ O ₅ is 0.7 wt% or more and 1.3 wt% or less. It is as follows.

Subsequently, in the molding step P2, the grinding stone raw material slurry 18 having fluidity in a warmed state is poured into a molding cavity provided in the molding die in a predetermined shape, for example, a similar shape slightly larger than the segment grinding stone 10, By lowering the temperature below the melting temperature of the water-soluble polysaccharide gelling agent 24, for example, to room temperature, a fluidized grindstone raw material slurry 18 is gelled or solidified to obtain a compact 28, which is taken out of the mold. FIG. 3A shows the state after gelation.

Next, in the freeze vacuum drying step P3, the molded body 28 is placed in the chamber of the freeze vacuum dryer. As a result, the molded body 28 is frozen at a preset freezing temperature of, for example, −15° C. or less, whereby a plurality of frozen particles 30 of a predetermined size are precipitated from the water 26 in the molded body 28, and the frozen particles are frozen. The frozen particles 30 are grown to a predetermined size by being maintained for a preset freezing time. FIG. 3B schematically shows this state. In this frozen state, the particles of the diamond abrasive grains 20 and the vitrified bond 22 are driven to the interface of the frozen particles 30. That is, the diamond abrasive grains 20 and the vitrified bonds 22 gather in the base portion 34 surrounding the frozen particles 30.

Next, in the freeze vacuum drying step P3, a plurality of frozen particles 30 in the molded body 28 are slowly sublimated by being set to a vacuum state for a predetermined time at a preset vacuum value below 610 Pa, for example, 10 Pa. As described above, vacuum drying is performed at, for example, 35° C., and a plurality of pores 32 are formed in the portion where the plurality of frozen particles 30 were located. FIG. 3C schematically shows this state. In this state, the diamond abrasive grains 20 and the vitrified bond 22 particles are dispersed in a fibrous polysaccharide molecule (water-soluble polysaccharide gelling agent 24) that surrounds the pores 32. Since the plurality of freezing particles 30 in the molded body 28 are in contact with each other in the process of growing, many of the plurality of pores 32 formed after sublimation of the plurality of freezing particles 30 communicate with each other. It is a continuous ventilation hole.

FIG. 4 shows a molded body formed into a circular test piece, which has been subjected to the same steps until frozen particles are grown to a predetermined size by being frozen at the preset freezing temperature and freezing time. In the photograph, the one dried under vacuum in a frozen state is shown on the left side, and the one dried at 50° C. under atmospheric pressure is shown on the right side. The molded body after freeze-vacuum drying shown on the left side of FIG. 4 did not lose its shape and had a strength that could be easily grasped by hand. On the other hand, the molded body after drying under normal pressure shown on the right side of FIG. 4 had a large shape collapse, and it was impossible to manufacture a high porosity vitrified grindstone.

In the firing step P4, the molded body 28 in which the plurality of pores 32 are formed is fired at a firing temperature set to the softening temperature of the vitrified bond 22 or higher, for example, a firing temperature of 500°C to 1000°C. As a result, the fibrous polysaccharide molecules (the water-soluble polysaccharide gelling agent 24) surrounding the pores 32 are burned down, and at the same time, the diamond abrasive grains 20 and the vitrified bonds 22 are sintered to bond the bond bridge 36 surrounding the pores 32. Is formed. Thereby, the segment grindstone 10 which is a high porosity vitrified grindstone is obtained. FIG. 3D schematically shows this state.

The bond bridge 36 has a thickness of, for example, about 10 μm and holds the diamond abrasive grains 20 having a center particle diameter of several μm, which is smaller than the thickness, and therefore has a dense structure like a non-pore-free vitrified grindstone. And the strength of the bond bridge 36 is increased without the coating of the reinforcing resin coating layer. Here, the central particle diameter of the diamond abrasive grains 20 is a median diameter (median diameter) defined by Japanese Industrial Standards (JIS Z 8825:2013), and is a value of D50 by volume conversion.

FIG. 5 shows, on the left side, an optical micrograph showing an enlarged pore structure of the compact 28 before the firing step P4, and the pore structure of the compact 28 after the firing step P4, that is, the high-porosity vitrified grindstone 10. An optical micrograph showing a magnified image is shown on the right side. As is clear from FIG. 5, in the pore structure of the molded body 28 that has undergone the firing step P4, no change due to the firing step P4 is observed, and the pore structure before the firing step P4 is maintained.

FIG. 6 is an SEM photograph showing the pore structure of the compact 28 (that is, the high porosity vitrified grindstone 10) after the firing step P4 in a further enlarged manner. The white line in FIG. 6 shows the bond bridge 36 surrounding the pore 32. FIG. 7 is an SEM photograph showing the bond bridge 36 in a further enlarged manner. As shown in FIG. 7, the bond bridge 36 has a dense structure. The fine particles on the bond bridge 36 are the diamond abrasive grains 20. The diamond abrasive grains 20 have a central particle diameter of 1/50 or more of the thickness of the bond bridge 36 and equal to or less than that.

Returning to FIG. 2, in the bonding/finishing step P5, the plurality of segment grindstones 10 baked in the baking step P4 are bonded to the base metal 12 as shown in FIG. Then, the segment grindstone 10 bonded to the base metal 12 is finished by using a dresser.

In the following, the present inventors have changed the proportions of diamond abrasive grains, vitrified bonds, water-soluble polysaccharide gelling agent, and water to produce chip shapes obtained by the same steps as those shown in FIG. Sample 1 to sample 10 (Example product) which are vitrified grindstones (40 mm×3 mm×5 mm), the central particle diameter of the diamond abrasive grains, the volume ratio Vg (volume %) of the diamond abrasive grains, and the volume ratio Vb of the vitrified bond. The ratio value (=Vg/Vb), the specific gravity ρ, the pore volume ratio Vp (volume %), and the grinding ratio GR are shown in FIG. Samples 1 to 10 (samples of Comparative Example), which are chip-shaped vitrified grindstones (40 mm x 3 mm x 5 mm) created in the step of forming pores using a conventional pore-forming agent, were also sample 1 to sample 10. Similarly to FIG. In addition, FIG. 9 is a diagram in which the points indicating Sample 1 to Sample 12 in FIG. 8 are plotted on the two-dimensional coordinates of the horizontal axis indicating Vg/Vb and the vertical axis indicating specific gravity ρ. Here, the specific gravity ρ of the grindstone is a value obtained by dividing the mass of the grindstone by the grindstone volume obtained from the size of the grindstone. The volume ratio Vg of the abrasive grains is a value obtained by dividing the abrasive grain volume obtained by dividing the mass of the abrasive grains by the specific gravity of the abrasive grains by the volume of the grindstone. The volume ratio Vb of the bond is a value obtained by dividing the bond volume obtained by dividing the mass of the bond by the specific gravity of the bond by the volume of the grindstone. The pore volume ratio Vp is a value obtained by dividing the pore volume by the grindstone volume.

As shown in FIG. 8 and FIG. 9, there are clear differences between Samples 1 to 10 and Samples 11 to 12 especially regarding the pore volume ratio Vp and the grinding ratio GR. Samples 1 to 10 have a pore volume ratio Vp of 65% by volume to 90% by volume and thus are larger than the samples 11 to 12, and have a grinding ratio GR of 11 to 750. large.

In the following, a grinding test 1 using the grindstones of Sample 9 (Example product) and Sample 11 (Comparative product), and grinding using the grindstones of Sample 3 (Example product) and Sample 12 (Comparative product) Test 2 will be described in detail. Grinding test 2 is for rough finishing, and grinding test 1 is for finishing.

(Grinding test 1)
· Vitrified bond composition SiO _2: 51.5 _{wt%, Al} 2 O 3: 14.7 _{wt%, B} 2 O 3: 18.9 _wt%, Na 2 O: 3.9 _{wt%, K} 2 O: It contains 3.8% by mass, MgO: 2.0% by mass, CaO: 1.9% by mass, BaO: 0.7% by mass, and P ₂ O ₅ : 0.9% by mass.
・Preparation of sample 9 Diamond abrasive grains having a central particle size of 0.2 μm: 17% by mass
Vitrified bond: 15% by mass
Water-soluble polysaccharide gelling agent (agar): 3% by mass
Water: 65 mass%
-Manufacturing method of sample 9 From the above formulation, the volume ratio Vg of diamond abrasive grains was 7.0 vol%, the volume ratio Vb of vitrified bonds was 8.6 vol%, and Vg/Vb=0. 8. A chip-shaped vitrified grindstone (Sample 9) having the same shape as the segment grindstone 10 and having a structure having a pore volume ratio Vp of 84.4% by volume and a specific gravity of 0.46 g/cm ³ was prepared.
-Manufacturing method of sample 11 Volume ratio Vg of diamond abrasive grains having a central particle diameter of 0.2 μm is 27.2% by volume, volume ratio Vb of vitrified bond similar to sample 9 is 17.3% by volume, Vg/Vb= A chip-shaped vitrified grindstone (sample 11) having a structure of 1.6, a pore volume ratio Vp of 55.5% by volume, and a specific gravity of 1.55 g/cm ³ was formed into a pore. It was prepared by a conventional process of forming pores by using an agent.

Grinding test method Grinding wheels in which the vitrified grindstones of Samples 9 and 11 were bonded to the lower surface of a base metal made of aluminum having an outer diameter of 300 mm as shown in FIG. Inch silicon wafers were each subjected to the following grinding processing conditions.
・Processing conditions for grinding test Grinding wheel rotation speed: 3000 rpm
Table (wafer) rotation speed: 395 rpm
Wheel feed rate: 0.5 μm/sec
Wafer removal allowance: Thickness 20 μm

・Result of grinding test with sample 9 Grinding wheel wear amount of sample 9: 1.7 μm
Machining current value: 19.0A
Surface roughness Ra: 1.2 nm
・Grinding test result by sample 11 Grinding wheel wear amount of sample 11: 35.3 μm
Machining current value: 18.9A
Surface roughness Ra: 1.2 nm

-Evaluation of Grinding Test Results Grinding using Sample 9 is not significantly different in grinding current value and surface roughness compared to grinding using Sample 11 according to the conventional manufacturing method. However, the grinding ratio when using sample 9 is 11.8 (=20 μm/1.7 μm), while the grinding ratio when using sample 11 is 0.57 (=20 μm/35.3 μm). ), the amount of abrasion of the grindstone when the sample 9 was used was significantly reduced.

(Grinding test 2)
· Vitrified bond composition SiO _2: 51.5 _{wt%, Al} 2 O 3: 14.7 _{wt%, B} 2 O 3: 18.9 _wt%, Na 2 O: 3.9 _{wt%, K} 2 O: It contains 3.8% by mass, MgO: 2.0% by mass, CaO: 1.9% by mass, BaO: 0.7% by mass, and P ₂ O ₅ : 0.9% by mass.
・Preparation of sample 3 Diamond abrasive grains having a central particle size of 6 μm: 21% by mass
Vitrified bond: 12% by mass
Water-soluble polysaccharide gelling agent (agar): 3% by mass
Water: 64% by mass
-Manufacturing method of sample 3 From the above formulation, the volume ratio Vg of diamond abrasive grains, the volume ratio Vb of vitrified bonds was 14.2 vol%, and Vg/Vb=1. 2. A chip-shaped vitrified grindstone (Sample 3) having the same structure as the segment grindstone 10 and having a structure having a pore volume ratio Vp of 68.5 volume% and a specific gravity of 0.96 g/cm ³ was prepared.
-Manufacturing method of sample 12 Volume ratio Vg of diamond abrasive grains having a central particle size of 6 μm is 40.9% by volume, volume ratio Vb of vitrified bond similar to sample 3 is 12.3% by volume, and Vg/Vb=3. 3, a chip-shaped vitrified grindstone (Sample 12) having a structure having a pore volume ratio Vp of 47.8 vol% and a specific gravity of 1.95 g/cm ³ and a pore-forming agent It was made by the conventional process of forming pores using.

-Grinding test method A grinding wheel in which the vitrified grindstones of Samples 3 and 12 are bonded to the bottom surface of an aluminum base metal having an outer diameter of 300 mm as shown in FIG. A 12-inch silicon wafer was ground under the following grinding processing conditions.
・Processing conditions for grinding test Grinding wheel rotation speed: 2000 rpm
Table (wafer) rotation speed: 300 rpm
Grindstone axis feed rate: 4.0 μm/sec
Wafer removal allowance: Thickness 150 μm

・Grinding result by sample 3 Grinding wheel wear amount of sample 3: 0.2 μm
Machining current value: 23.8A
Surface roughness Ra: 44.4 nm
・Grinding result by sample 12 Grinding wheel wear amount of sample 12: 164 μm
Machining current value: 14.2A
Surface roughness Ra: 39.1 nm

-Evaluation of Grinding Test Results Grinding using the sample 3 increases the machining current value as compared with grinding using the sample 12 by the conventional manufacturing method, but there is not much difference in surface roughness. However, the grinding ratio when using sample 3 is 750 (=150 μm/0.2 μm), whereas the grinding ratio when using sample 12 is 0.91 (=150 μm/164 μm). The wear amount of the grindstone when using Sample 3 was significantly reduced.

As described above, the method for manufacturing the high porosity vitrified grindstone 10 (segment grindstone 10) according to the present embodiment is a method for manufacturing the high porosity vitrified grindstone 10 including the plurality of pores 32 that communicate with each other, and is water-soluble. A grinding stone material adjusting step P1 for obtaining a grinding stone raw material slurry 18 in which a polysaccharide gelling agent 24 is dissolved, which is a mixed fluid of diamond grinding grains (abrasive grains) 20, vitrified bonds 22, and water 26, and a molding die are used. The forming step P2 in which the shaped material 28 is obtained by gelling the grindstone raw material slurry 18, and the shaped body 28 is frozen after the forming step P2 to generate a plurality of frozen particles 30 inside the shaped body 28, and A freeze-vacuum drying step P3 of sublimating the frozen particles 30 in the molded article 28 to dry the molded article 28 by placing the molded article 28 generated inside under vacuum, and molding after the freeze-vacuum drying step P3 A firing step P4 for obtaining the high-porosity vitrified grindstone 10 by firing the body 28 to bond the diamond abrasive grains 20 with the vitrified bond 22. In this way, in the freeze-vacuum drying step P3, the molded body 28 in which the plurality of frozen particles 30 are generated is placed under vacuum, so that the frozen particles 30 in the molded body 28 are sublimated and dried. After the freezing particles 30 are sublimated, the pores 32 communicating with each other are formed. For this reason, since there is no shrinkage of the molded body 28 due to the disappearance of bubbles, the high porosity vitrified grindstone 10 having a high porosity due to the communicating pores 32 is stably manufactured.

Further, according to the method of manufacturing the high porosity vitrified grindstone 10 of the present embodiment, the plurality of pores 32 communicating with each other are formed in the molded body 28 after the plurality of frozen particles 30 are sublimated in the freeze vacuum drying step P3. Are formed where the freezing particles 30 of FIG. The pores 32 formed in this way do not disappear, and the shrinkage of the molded body 28 that has been molded is suppressed.

Further, according to the method for manufacturing the high porosity vitrified grindstone 10 of the present embodiment, in the freeze-vacuum drying step P3, the frozen particles 30 are generated in the compact 28 in which the grindstone raw material slurry 18 is solidified into a gel. Then, the diamond abrasive grains 20 and the vitrified bond 22 are collected in the base portion 34 surrounding the frozen particles 30, and in the firing step P4, the bond bridge 36 which is the outer shell surrounding the pores 32 is formed by firing the base portion 34. Thus, the bond bridge 36 has a structure like a non-porous grindstone having no pores. As a result, the strength of the bond bridge 36 is increased even without the coating of the reinforcing resin coating layer, and the high porosity vitrified grindstone 10 can be ground even if it has a high porosity.

Further, according to the method for manufacturing the high porosity vitrified grindstone 10 of the present embodiment, the porosity volume ratio Vp of the high porosity vitrified grindstone 10 is 65% by volume to 90% by volume. As described above, since the high porosity vitrified grindstone 10 is configured with the porosity volume ratio Vp of 65% by volume to 90% by volume, the grinding efficiency and the strength of the grindstone are compatible with each other.

Further, according to the method of manufacturing the high porosity vitrified grindstone 10 of the present embodiment, the specific gravity of the high porosity vitrified grindstone 10 is 0.34 to 1.48. In this way, a relatively light porosity vitrified grindstone 10 having a specific gravity of 0.34 to 1.48 can be obtained.

Further, according to the method for manufacturing the high porosity vitrified grindstone 10 of the present embodiment, the grinding ratio of the high porosity vitrified grindstone 10 is 11 to 750. As described above, since the grinding ratio has a high value of 11 to 750, the durable high porosity vitrified grindstone 10 can be obtained.

Further, according to the method for manufacturing the high porosity vitrified grindstone 10 of the present embodiment, the diamond abrasive grains 20 have a central particle diameter smaller than the thickness of the bond bridge 36 forming the outer shell of the plurality of pores 32. is there. Thus, since the diamond abrasive grains 20 are significantly smaller than the thickness of the bond bridge 36 corresponding to the outer shell of the pores 32, the bond bridge 36 locally has a non-pore vitrified grindstone structure, so that the strength is increased. The grinding performance of the high porosity vitrified grindstone 10 is enhanced, and the surface roughness suitable for grinding a semiconductor wafer is obtained.

Further, according to the method for manufacturing the high porosity vitrified grindstone 10 of the present embodiment, the vitrified bond 22 is composed of 50 wt% to 54 wt% of SiO ₂ , 13 wt% to 15 wt% of Al ₂ O ₃ , and B ₂ O ₃ is 17.5 wt% to 20.5 wt %, and RO is 0.7 wt% to 6.5 wt% when RO is one or more oxides selected from CaO, MgO, BaO and ZnO. When R ₂ O is one or more kinds of oxides selected from LiO ₂ , Na ₂ O and K ₂ O, the R ₂ O is 0.0% by weight to 9.0% by weight and the P ₂ O ₅ is 0.7% by weight. % By weight to 1.3% by weight. Thereby, the high-strength vitrified bond 22 suitable for grinding a semiconductor wafer is obtained, and the durability of the high-porosity vitrified grindstone 10 is enhanced.

Although one embodiment of the present invention has been described in detail above with reference to the drawings, the present invention is not limited to this embodiment and can be implemented in other modes.

For example, in the above-described embodiment, the arc-shaped segment grindstone 10 fixed to the base metal 12 is described as a high-porosity vitrified grindstone, but the high-porosity vitrified grindstone is formed into a disc shape or other shapes. It may be a shaped grindstone.

Further, in the segment grindstone 10, a grindstone layer formed in a part related to grinding, for example, a part on the grinding surface 16 side may be a high porosity vitrified grindstone.

Further, although diamond abrasive grains are used as the abrasive grains in the above-described embodiments, the abrasive grains may not be diamond abrasive grains, and abrasive grains other than superabrasive grains may be used. Further, although the water-soluble polysaccharide gelling agent was used in the above-mentioned examples, it is not limited to the polysaccharide and any gelling water-soluble polymer may be used.

It should be noted that what has been described above is merely an embodiment, and other examples will not be given. However, the present invention can be carried out in a mode in which various modifications and improvements are made based on the knowledge of those skilled in the art without departing from the spirit of the invention. You can

10: Segment grindstone (high porosity vitrified grindstone)
12: Base metal 14: Cup grindstone 16: Grinding surface 18: Whetstone raw material slurry 20: Diamond abrasive grains (abrasive grains)
22: Vitrified bond 24: Water-soluble polysaccharide gelling agent (gelling water-soluble polymer)
26: Water 28: Molded body 30: Freezing particles 32: Porosity 34: Base part 36: Bond bridge

Claims (6)

A method for producing a high porosity vitrified grinding wheel containing a plurality of pores communicating with each other,
Abrasive grains, vitrified bonds, in which a gellable water-soluble polymer is dissolved, a grindstone material adjusting step of obtaining a grindstone raw material slurry that is a mixed fluid of water,
A forming step of obtaining a formed body by gelling the grindstone raw material slurry using a forming die;
After the molding step, the molded body is frozen to generate a plurality of frozen particles inside the molded body, and the molded body in which the frozen particles are generated is placed under vacuum to sublimate the frozen particles. A freeze vacuum drying step of drying the molded body,
And a firing step for obtaining the high porosity vitrified grindstone by firing the molded body after the freeze-vacuum drying step to bond the abrasive grains by the vitrified bond, and a high porosity vitrified Method of manufacturing whetstone. The high porosity according to claim 1, wherein the pores are formed in the place where the freezing particles were present in the grindstone raw material slurry after the freezing particles were sublimated in the freeze vacuum drying step. Method for manufacturing vitrified whetstone. In the freeze-vacuum drying step, the freezing particles are generated in the gel-like grindstone raw material slurry that constitutes the molded body, whereby the abrasive grains and the vitrified bonds are collected in a base portion surrounding the freezing particles. The method for producing a high-porosity vitrified grindstone according to claim 1 or 2, wherein, in the firing step, a bond bridge, which is an outer shell surrounding the pores, is formed from the base portion by firing the base portion. The method for producing a high-porosity vitrified grindstone according to any one of claims 1 to 3, wherein a porosity volume ratio of the high-porosity vitrified grindstone is 65% by volume to 90% by volume. The specific gravity of the high porosity vitrified grindstone is 0.34 to 1.48. The method for manufacturing a high porosity vitrified grindstone according to claim 1, wherein the specific gravity is 0.34 to 1.48. The method for producing a high-porosity vitrified grindstone according to claim 3, wherein the abrasive grains have a central particle diameter smaller than the thickness of the bond bridge forming the outer shell of the pores.