Vitrified bond grinding wheel

Abstract

To provide a vitrified bonded wheel having water resistance and strength which are above a certain level, which can be manufactured at a low sintering temperature.SOLUTION: The vitrified bonded wheel comprises abrasive grains and a binding material fixing the abrasive grains. The binding material is constituted to include a base material mainly composed of silicon dioxide (SiO2), sintering-auxiliary agent oxides and zinc oxides (ZnO), where contents of the zinc oxides (ZnO) are 11 wt% or more and 15 wt% or less in terms of weight ratio of the binding material. Preferably, contents of the sintering-auxiliary agent oxides are 20 wt% or more and 29 wt% or less. Preferably, the sintering-auxiliary agent oxides include one kind or more of sodium oxides (Na2O), calcium oxides (CaO), potassium oxides (K2O) and barium oxides (BaO). Further preferably, the binding material includes zirconium dioxide (ZrO2) whose contents are 3 wt% or more and 5 wt% or less in terms of weight ratio of the binding material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vitrified bond grinding wheel that is attached to a grinding wheel or the like provided in a grinding device that grinds a workpiece. [Background technology]

[0002] Device chips used in electronic devices such as mobile phones and personal computers are manufactured from wafers made of semiconductor materials such as silicon. Multiple devices are formed on the surface of the wafer, and the backside of the wafer is ground to thin the wafer to a specified thickness. The wafer is then divided into individual devices to produce individual device chips containing ICs, LSIs, and other devices.

[0003] A grinding device is used to grind the back surface of a wafer (see, for example, Patent Document 1). The grinding device includes an annular grinding wheel and a spindle that rotatably supports the grinding wheel. The grinding wheel includes an annular wheel base and a grinding stone that is annularly provided on one surface of the wheel base.

[0004] As a grinding wheel to be mounted on a grinding wheel, a grinding wheel called a vitrified bond grinding wheel is particularly widely used. A vitrified bond grinding wheel is formed by mixing and sintering a binder (a mixture of SiO2, Al2O3, and BO3) whose main component is glass with abrasive grains. The sintering temperature is high, at 1200°C to 1300°C, so the abrasive grains contained in the grinding wheel are easily carbonized and deteriorated. If a grinding process is performed using a grinding wheel with deteriorated abrasive grains, the grinding wheel will not be able to exhibit the expected performance.

[0005] In addition, when a workpiece is ground using a grinding wheel equipped with a grinding stone, the bond wears off to a certain extent, causing unused abrasive grains contained in the grinding stone to be exposed one after another, resulting in self-sharpening. This maintains the grinding ability of the grinding stone at a constant level. However, vitrified-bond grinding stones, which have a bond primarily composed of glass, are very hard and resistant to wear, making it difficult for self-sharpening to occur sufficiently, making it difficult to maintain a constant grinding ability.

[0006] Therefore, in order to make the grinding wheel brittle and make it more susceptible to self-sharpening, and to prevent deterioration of the abrasive grains, a technology has been implemented in which sintering aid oxides are added to the vitrified bond grinding wheel material to lower the sintering temperature. When the sintering temperature of a vitrified bond grinding wheel is lowered, the binder is consumed to a moderate extent, making the grinding wheel more susceptible to self-sharpening. Examples of sintering aid oxides include Na2O, CaO, KO, BaO, and Li2O. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-288881 Summary of the Invention [Problem to be solved by the invention]

[0008] However, these sintering aid oxides are easily soluble in water, which causes problems in that the water resistance and strength of a vitrified bond grinding wheel manufactured by adding and sintering a sintering aid oxide is likely to be low.When grinding a workpiece, grinding water is supplied to the grinding wheel and the workpiece, and a large force is applied to the grinding wheel, so a vitrified bond grinding wheel with low water resistance and strength is difficult to put into practical use.

[0009] The present invention has been made in view of these problems, and its object is to provide a vitrified bond grinding wheel that can be manufactured at a low sintering temperature and that has water resistance and strength above a certain level. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a vitrified bond grinding wheel having abrasive grains and a binder for fixing the abrasive grains, the binder comprising a matrix mainly composed of silicon dioxide (SiO2), a sintering aid oxide, and zinc oxide (ZnO), the content of the zinc oxide (ZnO) being 11 wt% or more and 15 wt% or less by weight of the binder. The binder contains zirconium dioxide (ZrO 2 ) is contained in the binder A vitrified bond grinding wheel is provided, characterized in that:

[0011] Preferably, the content of the sintering aid oxide is 20 wt % or more and 29 wt % or less in terms of weight ratio to the binder.

[0012] Preferably, the sintering aid oxide includes one or more of sodium oxide (Na2O), calcium oxide (CaO), potassium oxide (K2O), and barium oxide (BaO). [Effects of the Invention]

[0014] A vitrified bond grinding wheel according to one embodiment of the present invention comprises abrasive grains and a binder. The binder comprises a matrix primarily composed of silicon dioxide (SiO2), a sintering aid oxide, and zinc oxide (ZnO). The zinc oxide (ZnO) content is 11 wt% to 15 wt% by weight of the binder. A binder containing zinc oxide (ZnO) at a weight ratio of 11 wt% to 15 wt% has sufficient water resistance, can be sintered at a relatively low temperature, has strength sufficient to withstand grinding, and is not so hard as to prevent the progression of self-sharpening.

[0015] Therefore, according to one aspect of the present invention, a vitrified bond grinding wheel is provided which can be manufactured at a low sintering temperature and has water resistance and strength at or above a certain level. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a perspective view schematically showing the structure of a grinding wheel. [Figure 2] FIG. 2 is a side view schematically showing a workpiece to be ground by the grinding device. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a perspective view showing a typical structure of a grinding wheel 2 on which a vitrified bond grinding wheel 6 according to this embodiment is mounted.

[0018] As shown in Fig. 1, the grinding wheel 2 has a disk-shaped (annular) wheel base 4 made of stainless steel, aluminum, or the like. The wheel base 4 has a first surface 4a and a second surface 4b that are parallel to each other, and a circular opening 4c is formed in the center thereof, penetrating the wheel base 4 from the first surface 4a to the second surface 4b. A plurality of vitrified bond grinding wheels 6 according to this embodiment are arranged in an annular pattern on the second surface 4b of the wheel base 4.

[0019] The grinding wheel 2 is incorporated into a grinding unit of a grinding device for use. Fig. 2 is a side view schematically showing a workpiece 1 to be ground by a grinding device 8. The workpiece 1 is typically a semiconductor wafer, a resin substrate, a ceramic substrate, or the like, but is not limited to these.

[0020] The grinding device 8 includes a chuck table 10 that can hold the workpiece 1 by suction, and a grinding unit 12 that grinds the workpiece 1 held on the chuck table 10. The chuck table 10 is connected to a suction source (not shown), and the negative pressure generated by the suction source is applied to the workpiece 1 placed on the upper surface to hold the workpiece 1 by suction. The chuck table 10 can also be rotated around a rotation axis that is approximately perpendicular to the upper surface by a rotary drive source (not shown).

[0021] The grinding unit 12 includes a spindle 14 extending in a direction generally perpendicular to the upper surface of the chuck table 10, a rotary drive source 16 such as a motor connected to the upper end of the spindle 14 and rotating the spindle 14, and a wheel mount 18 connected to the lower end of the spindle 14. The grinding wheel 2 is fixed to the wheel mount 18 with the first surface 4a of the wheel base 4 in contact with the lower surface of the wheel mount 18. Then, the second surface 4b of the wheel base 4, on which the vitrified bond grinding wheel 6 is mounted, faces the upper surface of the chuck table 10.

[0022] The chuck table 10, which holds the workpiece 1 by suction, is rotated around a rotation axis perpendicular to its upper surface, and the rotary drive source 16 is operated to rotate the spindle 14, moving the vitrified bond grinding wheel 6 on a circular orbit and lowering the grinding unit 12. The vitrified bond grinding wheel 6 then comes into contact with the workpiece 1, grinding the workpiece 1. The grinding unit 12 is then lowered until the workpiece 1 reaches a predetermined thickness, completing the grinding of the workpiece 1.

[0023] When the workpiece 1 is ground with the vitrified bond grinding wheel 6, grinding chips and heat are generated from the workpiece 1 and the vitrified bond grinding wheel 6. Therefore, while the workpiece 1 is being ground, grinding water such as pure water is supplied from a grinding water supply nozzle (not shown) to the upper surface of the workpiece 1 and the grinding wheel 2, and the grinding chips and heat are removed by the grinding water. For these reasons, the vitrified bond grinding wheel 6 needs to have a certain level of water resistance or higher.

[0024] The vitrified bond grinding wheel 6 according to this embodiment has a binder and numerous abrasive grains dispersed and fixed in the binder. The abrasive grains are formed of, for example, diamond, CBN (Cubic Boron Nitride), etc. The material, average particle size, content of the abrasive grains in the binder, etc. can be appropriately selected according to the specifications of the vitrified bond grinding wheel 6.

[0025] When the vitrified bond grinding wheel 6 is brought into contact with the workpiece 1, the workpiece 1 is ground by the abrasive grains, which are gradually worn away. At the same time, the bonding material is gradually worn away, and new abrasive grains are successively exposed. As a result, the grinding ability of the vitrified bond grinding wheel 6 is maintained at a constant level. This effect is called self-sharpening.

[0026] However, if the bond is too hard, wear will be difficult to occur, self-sharpening will not proceed properly, and the grinding ability of the vitrified bond grinding wheel 6 will decrease. On the other hand, if the strength of the bond is too low, the workpiece 1 will not be ground properly. Therefore, the bond needs to have appropriate hardness and strength.

[0027] When manufacturing a vitrified bond grinding wheel 6, abrasive grains are mixed into the raw material for the bond, which is then molded and sintered at high temperatures. The temperature suitable for sintering varies depending on the composition of the raw material for the bond. If the sintering temperature of the bond is too high, the abrasive grains will carbonize and deteriorate during sintering, so it is preferable that the bond can be sintered at a low temperature.

[0028] The binder of the vitrified bond grinding wheel 6 contains a matrix whose main component is silicon dioxide (SiO2). The binder may further contain B2O3 or Al2O3 as matrix materials that form a glassy substance. However, the sintering temperature for a binder composed solely of a matrix whose main components are SiO2, Al2O3, and B2O3 is high, at approximately 1200°C to 1300°C. Sintering the vitrified bond grinding wheel 6 at this temperature will cause the abrasive grains dispersed in the binder to deteriorate.

[0029] Therefore, sintering aid oxides are mixed into the raw materials of the binder to lower the sintering temperature. The sintering aid oxides include, for example, one or more of sodium oxide (Na2O), calcium oxide (CaO), potassium oxide (KO), and barium oxide (BaO). The content of the sintering aid oxides is preferably 20 wt% or more and 29 wt% or less of the binder by weight. When the sintering aid oxides are added to the binder, the sintering temperature is lowered, and the abrasive grains are less likely to deteriorate during sintering.

[0030] However, a vitrified bond grinding wheel 6 made of a binder containing such sintering aid oxides tends to have low mechanical strength and low water resistance. When grinding the workpiece 1, a large force is applied to the vitrified bond grinding wheel attached to the grinding wheel 2. Furthermore, a grinding fluid containing water is applied to the workpiece 1 during grinding. Therefore, when grinding is performed with a vitrified bond grinding wheel 6 that has low mechanical strength and water resistance, the vitrified bond grinding wheel 6 is prone to damage, which becomes a problem.

[0031] Therefore, in the vitrified bond grinding wheel 6 according to this embodiment, zinc oxide (ZnO), which is hardly soluble in water, is preferably mixed into the binder at a predetermined content. In particular, the zinc oxide content is preferably 11 wt% or more and 15 wt% or less by weight of the binder. below In this case, the sintering temperature can be kept relatively low, and the vitrified bond grinding wheel 6 has water resistance and mechanical strength at or above a predetermined level.

[0032] Therefore, the vitrified bond grinding wheel 6 according to this embodiment has a low sintering temperature and is moderately worn during grinding, while maintaining sufficient mechanical strength and water resistance, making it suitable for grinding.

[0033] Furthermore, the binder may contain a predetermined amount of zirconium dioxide (ZrO2) mixed in with zinc oxide (ZnO). In particular, if the content of zirconium dioxide (ZrO2) is 3 wt% or more and 5 wt% or less by weight of the binder, the water resistance and mechanical strength of the binder will be improved. [Example]

[0034] In this example, a vitrified bond grinding wheel 6 was produced having a base material mainly composed of silicon dioxide (SiO2), a sintering aid oxide, and a binder containing zinc oxide (ZnO), and its water resistance, mechanical strength, and sintering temperature during production were evaluated. In this example, a plurality of vitrified bond grinding wheels 6 with different blending ratios of the binder components were produced, and these values ​​were evaluated for each of them.

[0035] Here, the zinc oxide (ZnO) content in the binder was set to 11 wt% or more and 15 wt% or less by weight of the binder. For comparison, a vitrified bond grinding wheel 6 was also produced in which the zinc oxide (ZnO) content in the binder did not satisfy this range, and water resistance, etc. were similarly evaluated.

[0036] Predetermined amounts of a base material mainly composed of silicon dioxide (SiO2), a sintering aid oxide, and zinc oxide (ZnO) were prepared as materials for the vitrified bond grinding wheel 6. The materials were then mixed using a predetermined method, the mixed material was placed in a mold, molded, and sintered at the required temperature to produce the vitrified bond grinding wheel 6.

[0037] The names of each vitrified bond grinding wheel 6 and the weight ratio (wt%) of each material contained in the binder are shown in Table 1 below. Here, the names of those in which the zinc oxide (ZnO) content in the binder satisfies the range of 11 wt% to 15 wt% by weight of the binder are referred to as "Examples," while those that do not are referred to as "Comparative Examples." Note that Table 1 omits some of the constituent materials of the binder of the vitrified bond grinding wheel 6 and their weight ratios. Therefore, the total weight ratios of the base material, additive oxides, and sintering aid oxides listed in the table do not necessarily add up to 100 wt%. [Table 1]

[0038] Next, a flexural strength test was conducted to evaluate the mechanical strength of each of the prepared vitrified bonded grinding wheels 6. A hardness strength measuring device "AGI-1kN" manufactured by Shimadzu Corporation was used for the flexural strength test. The prepared vitrified bonded grinding wheels 6 were pressed at a pressure rate of 1 mm / min and a load capacity set to 0 N to 1 kN, and the pressure value at which fracture occurred was recorded as the flexural strength. The relative flexural strength of each vitrified bonded grinding wheel 6 was then calculated, with the flexural strength of the vitrified bonded grinding wheel according to Comparative Example 1 being set at 100. The relative flexural strength values ​​of each vitrified bonded grinding wheel 6 are shown in Table 2 below.

[0039] Furthermore, a water resistance evaluation test was conducted on each of the manufactured vitrified bond grinding wheels 6. In the water resistance evaluation test, each vitrified bond grinding wheel 6 was immersed in hot water for 5 hours, and the weight was measured before and after immersion. Note that hot water was used in this test in order to make the test environment similar to the environment during grinding, taking into consideration that the vitrified bond grinding wheel is heated by the heat generated during grinding.

[0040] First, the weight of each vitrified bond grinding wheel 6 was measured before immersion in hot water. Next, after immersion in hot water for 5 hours, the vitrified bond grinding wheel 6 was dried and then re-measured. The weight of each vitrified bond grinding wheel 6 before immersion was divided by the weight after immersion to calculate the solubility. Then, the relative value of the solubility of each vitrified bond grinding wheel according to the Examples was calculated, assuming the solubility value of the vitrified bond grinding wheel 6 according to Comparative Example 1 to be 100.

[0041] The smaller this relative value of solubility, the lower the solubility in grinding water and the higher the water resistance. In other words, the smaller the weight change of the vitrified bond grinding wheel 6 and the higher the water resistance, the lower this relative value becomes. Table 2 below shows the relative values ​​of solubility of each vitrified bond grinding wheel 6 according to the examples. Table 2 also lists the temperature required to sinter each vitrified bond grinding wheel 6 as the sintering temperature. [Table 2]

[0042] The sintering temperature of the vitrified bond grinding wheel 6 is preferably 780°C or lower. If the sintering temperature exceeds this temperature, the abrasive grains, such as diamond and SiC, dispersed in the binder material, and the filler, etc., will be altered. The vitrified bond grinding wheels 6 according to Comparative Examples 3, 4, 5, 6, and 7 require a sintering temperature of 800°C or higher, which is thought to cause the abrasive grains, etc., to be altered and prevent the expected grinding ability from being achieved.

[0043] Furthermore, the mechanical strength that a vitrified bond grinding wheel 6 must have when processing a workpiece 1 is a relative value of the above-mentioned flexural strength of more than about 95. A vitrified bond grinding wheel 6 with a flexural strength lower than this will break as it deteriorates through repeated grinding processes. The vitrified bond grinding wheels 6 according to Comparative Examples 2 and 6 have relative values ​​of flexural strength lower than this, and are therefore evaluated as not having the necessary mechanical strength.

[0044] Furthermore, the water resistance that a vitrified bond grinding wheel 6 must have when processing a workpiece 1 is below about 55 in the relative value of water resistance described above. If the relative value of water resistance is higher than this, the binder will gradually dissolve in the supplied grinding water, and the vitrified bond grinding wheel 6 will deteriorate and become unable to perform appropriate grinding before the expected usage period of one month has elapsed. The vitrified bond grinding wheels 6 according to Comparative Examples 1, 2, and 7 have relative values ​​of water resistance that exceed this value, and are therefore evaluated as not having the necessary water resistance.

[0045] Furthermore, the vitrified bond grinding wheels 6 according to Examples 1 to 8 are all evaluated as having sufficient mechanical strength and water resistance, with sintering temperatures below 780°C, allowing the abrasive grains and other components to fully function. Therefore, it was confirmed that when the zinc oxide (ZnO) content in the binder is 11 wt% or more and 15 wt% or less by weight of the binder, it is possible to manufacture the vitrified bond grinding wheels 6 at a low sintering temperature, and that the vitrified bond grinding wheels 6 have water resistance and strength above a certain level.

[0046] Furthermore, as can be seen from the relative value of the flexural strength of the vitrified bonded grinding wheel 6 according to Comparative Example 6, if the ZnO content is excessive and the sintering aid oxide content is too low, the strength of the vitrified bonded grinding wheel 6 decreases. On the other hand, as can be seen from the performance evaluation of the vitrified bonded grinding wheel 6 according to Comparative Example 7, if the sintering aid oxide content is too high, the water resistance of the vitrified bonded grinding wheel 6 becomes relatively low. Therefore, the sintering aid oxide content is preferably 20 wt% or more and 29 wt% or less by weight of the binder.

[0047] Furthermore, as can be seen from the sintering temperature of the vitrified bond grinding wheel 6 according to Comparative Example 5, even if the content of the sintering aid oxide satisfies this range, if the content of ZnO is less than the required amount, the sintering temperature becomes higher. Therefore, it is essential that the binder contains ZnO in the above range.

[0048] Furthermore, as can be seen from the performance evaluation of the vitrified bond grinding wheel 6 according to Comparative Example 2, this example shows that the water resistance of a vitrified bond grinding wheel 6 containing LiO as a binder material is relatively low. Furthermore, as can be seen from the performance of the vitrified bond grinding wheel 6 according to Comparative Example 4, the sintering temperature of a binder containing MgO is difficult to lower. Therefore, it is preferable that the binder of the vitrified bond grinding wheel 6 does not contain LiO or MgO.

[0049] Furthermore, from the results of the performance evaluation of each vitrified bond grinding wheel 6 in this example, it is understood that it is preferable that the bond contains a certain amount of zirconium dioxide (ZrO2) in addition to ZnO. In other words, it is preferable for the vitrified bond grinding wheel 6 to contain zirconium dioxide (ZrO2) in the bond at a content of 3 wt% to 5 wt% by weight of the bond.

[0050] The present invention is not limited to the above-described embodiments, and various modifications can be made to the structures, methods, etc. described in the above-described embodiments without departing from the scope of the present invention. [Explanation of symbols]

[0051] 1 Workpiece 2 grinding wheels 4 Wheel base 4a 1st page 4b 2nd side 4c opening 6 Vitrified bond grinding wheels 8 Grinding equipment 10 Chuck table 12 Grinding unit 14 Spindle 16 Rotational drive source 18 Wheel mount

Claims

1. A vitrified bond grinding wheel having abrasive grains and a bonding material for fixing the abrasive grains, The binder is silicon dioxide (SiO ２ The sintering aid oxide and zinc oxide (ZnO) are included in the base material, the base material being mainly composed of zinc oxide (ZnO), and the sintering aid oxide and zinc oxide (ZnO) are included in the base material. The content of the zinc oxide (ZnO) is 11 wt % or more and 15 wt % or less by weight of the binder, A vitrified bond grinding wheel characterized in that the binder contains zirconium dioxide (ZrO 2 ) in an amount of 3 wt % or more and 5 wt % or less by weight of the binder.

2. 2. The vitrified bond grinding wheel according to claim 1, wherein the content of said sintering aid oxide is 20 wt % or more and 29 wt % or less in terms of weight ratio to said binder.

3. The sintering aid oxide is sodium oxide (Na ２ O), calcium oxide (CaO), potassium oxide (K ２ 3. The vitrified bond grinding wheel according to claim 1, further comprising one or more of the following: fluorine-containing silica (SiO), fluorine-containing silica (SiO), and barium oxide (BaO).

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