JP7685852B2 - Vitrified tool and manufacturing method thereof - Google Patents

Description

The present invention relates to vitrified tools and their manufacturing methods.

A vitrified tool comprises a base material and a bond layer made of glass that holds countless abrasive grains. The bond layer holding countless abrasive grains may be manufactured as a chip and the chip may be fixed onto the base material, or the bond layer holding countless abrasive grains may be fixed directly onto the base material. The bond layer may or may not contain pores. Patent Document 1 discloses a technology for impregnating the pores in the bond layer with resin to improve the abrasive grain retention of this vitrified tool.

For example, this vitrified tool is embodied as a grinding tool and is used in grinding processes. Vitrified tools have the characteristic that the surface density of the abrasive grains on the grinding surface and the size of the abrasive grains can be easily adjusted during manufacturing.

International Publication No. WO 2006/090527

However, since vitrified tools are used to process difficult-to-cut materials such as semiconductor wafers, cemented carbide, and ceramics, if diamond, which has the highest hardness, is used, the surface roughness of the mating material after grinding is low and scratches are likely to occur. This is because the wettability of diamond with glass is low and the holding condition between diamond and the bond layer is likely to differ, so the diamonds are scattered and the grinding condition is likely to vary.

The present invention was made in consideration of the above-mentioned conventional situation, and the problem to be solved is to provide a vitrified tool that uses diamond as an abrasive grain, while providing a high surface roughness for the mating material after polishing, and is less likely to cause scratches.

The vitrified tool of the present invention comprises a base material and a tip provided on the base material,
The tip includes a number of abrasive grains and a bond layer made of glass that holds the abrasive grains,
each said abrasive grain being diamond;
The bond layer is characterized by containing 10.6 mol % or more of bismuth oxide, 4.8-25.4 mol % of SiO ₂ , 0.8-4.4 mol % of Al ₂ O ₃ , 21.0-31.1 mol % of B ₂ O ₃ , 0.1-0.2 mol % of alkali oxides, and 27.0-34.4 mol % of alkaline earth oxides.

According to the inventor's test, the vitrified tool of the present invention has diamond grains, but the glassy bond layer contains 10.6 mol% or more of bismuth oxide (Bi ₂ O ₃ ), and the glassy material contains 4.8-25.4 mol% SiO ₂ , 0.8-4.4 mol% Al ₂ O ₃ , 21.0-31.1 mol% B ₂ O ₃ , 0.1-0.2 mol% alkali oxide, and 27.0-34.4 mol% alkaline earth oxide, so that the bond layer exhibits high wettability to diamond. Therefore, the holding state of diamond and the bond layer is unlikely to differ, and diamond is likely to be evenly distributed, so that the grinding state is unlikely to vary.

The method for producing a vitrified tool of the present invention includes the following steps: a first step of preparing _a mixture containing a composition that forms a glass material and contains at least 10.6 mol % bismuth oxide, _4.8 to 25.4 mol % _{SiO2 ,} 0.8 to 4.4 mol % _Al2O3 , 21.0 to 31.1 mol % B2O3, 0.1 to 0.2 mol % alkali oxides, and 27.0 to 34.4 mol % alkaline earth oxides, and a countless number of abrasive grains made of diamond;
A second step of obtaining a molded body of the mixture;
The method is characterized by comprising a third step of firing the molded body in an oxidizing atmosphere to form a bond layer that holds the abrasive grains with the vitreous material made of the composition, and providing a tip having the abrasive grains and the bond layer on a substrate to obtain a vitrified tool.

The manufacturing method of the present invention makes it possible to manufacture the vitrified tool of the present invention.

The vitrified tool of the present invention uses diamond as an abrasive grain, yet the surface roughness of the mating material after polishing is high and scratches are less likely to occur.

FIG. 1 is a schematic enlarged cross-sectional view of a chip according to an embodiment of the present invention. FIG. 2 is a graph showing the relationship between temperature and elongation of the compositions used in the examples. FIG. 3 shows the results of XRD measurement showing the crystallinity of the compositions used in the examples. FIG. 4 is a perspective view of a grinding tool as an example of a vitrified tool according to an embodiment. FIG. 5 is a micrograph showing the side of the bond layer in Test 2 using the slurry of Test Sample 1. FIG. 6 is a photomicrograph showing a cross section of the bond layer in Test 2 using the slurry of Test Piece 1. FIG. 7 is a micrograph showing the side of the bond layer formed using the slurry of test sample 6 in test 2. FIG. 8 is a micrograph showing a cross section of the bond layer using the slurry of test piece 6 in test 2. FIG. 9 is a perspective view of another grinding tool. FIG. 10 is a perspective view of another grinding tool.

In addition to rigid substrates, substrates that are flexible enough not to deform the bond layer holding the countless abrasive grains can be used. Rigid substrates include ceramics such as alumina, silicon nitride, silicon carbide, zirconia, and mullite, metals such as iron, SUS, and copper, and glass with a strain point of 600°C or higher. Flexible substrates include sheets made of woven or nonwoven fabrics made of fibers such as natural fibers, synthetic fibers, and carbon fibers, and single-layer or multi-layer films made of synthetic resins such as polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyimide (PI), polyethylene naphthalate (PEN), and aramid, and metals such as aluminum and copper.

The vitreous bond layer can be a composition containing a frit such as borosilicate glass. The composition can be a slurry or a powder. A mixture containing the composition and numerous abrasive grains of diamond can also be a slurry or a powder. The mixture is formed into a molded body, the molded body is dried as necessary, and the composition is melted and solidified, so that the composition forms a vitreous body.

The mixture ratio (volume) of glass to diamond in the bond layer is preferably 80:20 to 10:90, and more preferably 60:40 to 25:75. To adjust the porosity of the bond layer, a pore-forming material may be added to the mixture.

The abrasive grains used in the vitrified tool of the present invention are diamond. The grain size of the diamond is set in various ways depending on the application of the vitrified tool.

According to the inventor's test results, the effect of the present invention can be obtained if the bond layer contains 10.6 mol% or more of bismuth oxide, but it is more preferable that the bond layer contains 28.6 mol% or more of bismuth oxide. In terms of mass%, the effect of the present invention can be obtained if the bond layer contains 40.6 mass% or more of bismuth oxide, but it is more preferable that the bond layer contains 71.1 mass% or more of bismuth oxide. In this case, the bond layer has high wettability with diamond.

_{The bond layer may contain SiO2, Al2O3, B2O3 , alkali oxides} and alkaline earth oxides in addition to bismuth oxide. _SiO2 is preferably 4.8 _mol % or more and 25.4 mol% or less. In terms of mass%, _SiO2 is preferably 1.4 mass% or more and 12.6 mass% or less. _Al2O3 is preferably 0.8 mol% or more and 4.4 mol% or less. In terms of mass%, _{Al2O3 is} preferably 0.4 mass% or more and 3.7 mass% or less. _B2O3 is preferably _21.0 mol% or more and 31.1 mol% or less. In terms of mass%, _{B2O3 is} preferably 7.8 mass% or more and less than 14.4 mass _% . The alkali oxide is preferably 0.1 mol% or more and 0.2 mol% or less. In terms of mass%, the alkali oxide is preferably 0.1 mass% or less, the alkaline earth oxide is preferably 27.0 mol% or more and 34.4 mol% or less, and the alkaline earth oxide is preferably 10.7 mass% or more and 28.7 mass% or less.

According to the inventor's test results, the bond layer preferably has a softening point of 391°C or higher and 549°C or lower. The bond layer preferably has a softening point of 522°C or lower, and more preferably 436°C or lower. In this case, the bond layer has high wettability with diamond.

Furthermore, according to the inventor's test results, it is preferable that the bond layer has a crystallinity of 90% or less. In this case, the bond layer has high wettability with diamond. It is more preferable that the bond layer has a crystallinity of 70% or less, and even more preferable that it is 8% or less.

According to the inventor's test results, in the manufacturing method of the present invention, it is preferable that the oxidizing atmosphere does not introduce a reducing gas such as hydrogen into the firing chamber, and that the oxygen concentration is 0.01 to 20%. If a reducing gas is introduced into the firing chamber or the oxygen concentration is less than 0.01%, the bismuth oxide in the composition is reduced, and the bond layer cannot exhibit suitable wettability with the diamond abrasive grains. If the oxygen concentration exceeds 20%, the diamond abrasive grains are likely to disappear, depending on the firing time.

In the manufacturing method of the present invention, in the third step, it is preferable to sinter the base material compact at 585°C or less. This is because, according to the inventor's test results, the vitrified tool of the present invention was obtained with a composition whose yield point is 585°C. In this case, although it depends on the relationship with the sintering time, the diamond abrasive grains are less likely to disappear, and the bond layer has high wettability with diamond. In the third step, it is more preferable to sinter the base material compact at 467°C or less.

The present invention will be explained below using Tests 1 to 3, along with Examples 1 to 5 and a Comparative Example.

(Test 1)
In Test 1, the composition of the composition was changed in various ways, and chips 20 were manufactured using diamond as the abrasive grains 1, as shown in Figure 1. Each chip 20 has countless abrasive grains 1 held in a bond layer 5 made of glass. The bond layer 5 contains pores 7 and has multiple layers of abrasive grains 1.

First, in the first step, compositions 1 to 7, countless abrasive grains 1 (diamond, average particle size: 0.5 μm), binder resin (acrylic resin), and solvent (alcohol) were prepared. The glass-equivalent mol% of compositions 1 to 7 is shown in Table 1, and the mass% is shown in Table 2. The lower row of Table 1 shows the mol% of the alkali oxides and alkaline earth oxides, and the lower row of Table 2 shows the mass% of the alkali oxides and alkaline earth oxides.

TMA measurements were performed on each of compositions 1 to 7. As shown in Figure 2, each of compositions 1 to 7 melts when heated, and therefore shows a softening point Tg (°C) and a yield point Ts (°C). In addition, each of compositions 1 to 7 was evaluated using an XRD evaluation device ("Smartlab" manufactured by Rigaku) as shown in Figure 3 to determine the degree of crystallinity. These results are shown in Table 3.

Compositions 1 to 7 and abrasive grains 1 were placed in a ball mill and the ball mill was rotated. In this way, slurries for test pieces 1 to 7 were obtained. The mixture ratio (volume) of the glassy material of the bond layer 5 to the abrasive grains 1 was 30:70.

In the second step, each slurry was formed into a chip shape, and the solvent was evaporated to form a compact.

In the third step, each molded body was fired for a predetermined time to obtain chips 20. It was not possible to manufacture chips 20 using the slurry of test sample 7. The gas type, oxygen concentration (%), and atmosphere in the firing chamber at this time are shown in Table 4.

As shown in Figure 4, the chips 20 obtained from the slurries of test pieces 1 to 5 were bonded to an aluminum alloy base metal 15 as a substrate to form a grinding tool. In one cutting tool, chips 20 made from the same slurry were bonded.

(Test 2)
In Test 2, the wettability between the abrasive grains 1 and the bond layer 5 was confirmed. First, the slurries of the test pieces 1 to 6 were applied to an alumina substrate to a thickness of about 10 μm, and the abrasive grains 1 made of diamond with an average particle size of 12 μm were placed on the film, and sintering was performed in the same manner as in Test 1. After sintering, the extent to which the abrasive grains 1 were embedded in the bond layer 5 made of the slurries of the test pieces 1 to 6 was evaluated according to the following criteria.
⊚: The bond layer 5 is 50% or more of the diameter of the abrasive grain 1. ◯: The bond layer 5 is 10% or more of the diameter of the abrasive grain 1. ×: The bond layer 5 is less than 10% of the diameter of the abrasive grain 1.

Figure 4 shows a micrograph of the side of the bond layer 5 using the slurry of test sample 1, and Figure 5 shows a micrograph of its cross section. Figure 6 shows a micrograph of the side of the bond layer 5 using the slurry of test sample 6, and Figure 7 shows a micrograph of its cross section.

As shown in Figures 4 and 5, when the slurry of test sample 1 is used, it can be seen that the black diamond abrasive grains 1 are embedded in the white bond layer 5. It can also be seen that when the slurry of test sample 1 is used, the bond layer 5 is well coated around the abrasive grains 1. This is because the bond layer 5 made of the slurry of comparative example 1 has high wettability with respect to the diamond abrasive grains 1. The same is true when the slurries of test samples 2 to 5 are used.

On the other hand, as shown in Figures 6 and 7, when the slurry of test sample 6 was used, the abrasive grains 1 were exposed from the bond layer 5. Also, when the slurry of test sample 6 was used, there were some areas where the abrasive grains 1 were scattered, which shows that the grinding condition is prone to variation.

(Test 3)
Grinding tools for evaluation were prepared using each tip 20 obtained with the slurries of test samples 1 to 6. The grinding tools for evaluation using each tip 20 obtained with the slurries of test samples 1 to 5 were the vitrified tools of Examples 1 to 5, and the grinding tool for evaluation using each tip 20 obtained with the slurry of test sample 6 was the vitrified tool of the comparative example. A Si wafer was ground with each of the grinding tools for evaluation, and the surface roughness of the wafer after grinding was confirmed with a surface roughness meter (Zygo) and evaluated under the following conditions.
◎: Sa = less than 2 nm ◯: Sa = less than 3 nm ×: Sa = 3 nm or more

In addition, the wafers after grinding were checked for the presence or absence of scratches of 20 nm or more in depth, and were rated as ◯ if none were present and × if present. The results are shown in Table 5.

As is clear from Table 5, the bond layers 5 of the evaluation grinding tools of Examples 1 to 5 have excellent wettability, even though the abrasive grains 1 are diamond. In particular, the bond layers 5 of the evaluation grinding tools of Examples 1 and 2, in which the bond layers 5 contain 28.6 mol% or more of bismuth oxide, exhibit excellent wettability. Therefore, it can be seen that the vitrified tools using the tips 20 having these bond layers 5 have excellent polishing and scratch resistance while using diamond as the abrasive grains 1. This is because they contain a specific amount or more of bismuth oxide. In addition, these bond layers 5 have a softening point of 391°C or more and 549°C or less, and a crystallinity of 90% or less.

The tips 20 of Examples 1 to 5 can also be embodied in the grinding tools of Figures 9 and 10. The grinding tool shown in Figure 9 employs a rod-shaped base metal 17, with multiple tips 20 bonded to the peripheral surface of this base metal 17. The grinding tool shown in Figure 10 employs a plate-shaped base metal 19, with multiple tips 20 bonded to one surface of this base metal 19.

Therefore, the vitrified tools of Examples 1 to 5 are capable of machining difficult-to-cut materials with high-speed rotating tools.

Although the present invention has been described above with reference to Tests 1 to 3 and Examples 1 to 5, it goes without saying that the present invention is not limited to the above Tests 1 to 3 and Examples 1 to 5, and can be modified as appropriate without departing from the spirit of the present invention.

In the above embodiment, the bond layer 5 holding countless abrasive grains 1 is manufactured as the chip 20, and the chip 20 is fixed onto the substrate. However, the vitrified tool of the present invention may have the bond layer 5 holding countless abrasive grains 1 directly fixed onto the substrate. The bond layer 5 may have multiple layers of abrasive grains 1 on the substrate as in the embodiment, or may have only a single layer of abrasive grains 1 on the substrate. Furthermore, in the above embodiment, the bond layer 5 has pores 7, but the bond layer 5 may have no pores 7 and be dense. In the vitrified tool of the present invention, if the abrasive grains are only fixed onto the substrate in a single layer, it is preferable to use a dense bond layer that is substantially free of pores.

The present invention can be used for grinding tools, etc.

15...Base material (base metal)
5... Bond layer 1... Abrasive grain

Claims (6)

A substrate and a chip provided on the substrate,
The tip includes a number of abrasive grains and a bond layer made of glass that holds the abrasive grains,
each said abrasive grain being diamond;
1. A vitrified tool, wherein the bond layer contains 10.6 mol % or more of bismuth oxide, 4.8 to 25.4 mol % of SiO ₂ , 0.8 to 4.4 mol % of Al ₂ O ₃ , 21.0 to 31.1 mol % of B ₂ O ₃ , 0.1 to 0.2 mol % of alkali oxides, and 27.0 to 34.4 mol % of alkaline earth oxides. A vitrified tool according to claim 1, wherein the bond layer has a crystallinity of 70% or less. A vitrified tool according to claim 2, wherein the bond layer has a crystallinity of 8% or less. A vitrified tool according to any one of claims 1 to 3, wherein the bond layer contains bismuth oxide at 28.6 mol% or more. A first step of preparing a mixture containing a composition for forming a glass material, the composition containing 10.6 mol % or more of bismuth oxide, _4.8 to 25.4 mol % _{of SiO2} , 0.8 to 4.4 mol % _{of Al2O3} , 21.0 to 31.1 mol % of B2O3, 0.1 to 0.2 mol % of an alkali oxide, and 27.0 to 34.4 mol % of an alkaline earth oxide, and a countless number of abrasive grains made of diamond;
A second step of obtaining a molded body of the mixture;
a third step of firing the molded body in an oxidizing atmosphere to form a bond layer that holds the abrasive grains with the vitreous material made of the composition, and providing a tip having the abrasive grains and the bond layer on a substrate to obtain a vitrified tool. The method for manufacturing a vitrified tool according to claim 5, wherein the oxidizing atmosphere has an oxygen concentration of 0.01 to 20%.

Images