JP7736482B2 - Grinding wheels - Google Patents

Description

The present invention relates to a grinding wheel used to grind workpieces.

The device chip manufacturing process uses a wafer on which devices are formed in multiple areas defined by multiple intersecting streets (planned division lines). By dividing this wafer along the streets, multiple device chips, each equipped with a device, are obtained. The device chips are incorporated into various electronic devices such as mobile phones and personal computers.

In recent years, with the miniaturization of electronic devices, there has been a demand for thinner device chips. To address this, a process is sometimes carried out in which wafers before being divided are ground using a grinding device to thin them. The grinding device is equipped with a chuck table that includes a holding surface for holding the workpiece, and a grinding unit that grinds the workpiece. A grinding wheel containing multiple grinding stones (grinding wheels) is attached to the grinding unit (see Patent Document 1).

When using a grinding device to grind a workpiece such as a wafer, the relative positions of the chuck table and grinding unit are adjusted so that the center of the workpiece held by the chuck table is aligned with the trajectory of the grinding wheel. Then, while the chuck table and grinding wheel are both rotated, the grinding wheel is lowered in the processing feed direction (vertical direction) perpendicular to the holding surface, causing the bottom surface of the grinding wheel to come into contact with the top surface of the workpiece, grinding it. This type of grinding method is called in-feed grinding.

On the other hand, a grinding method known as creep feed grinding is sometimes used to grind workpieces. In creep feed grinding, the grinding wheel is positioned outside the workpiece, and the relative positions of the chuck table and grinding unit are adjusted so that the bottom surface of the grinding wheel is positioned below the top surface of the workpiece. Then, while rotating the grinding wheel, the chuck table is moved along the processing feed direction (horizontal direction) parallel to the holding surface. As a result, the top surface of the workpiece is scraped away from the side surface of the workpiece by the grinding wheel, thinning the workpiece (see Patent Document 2).

Japanese Patent Application Laid-Open No. 2000-288881 Japanese Patent Application Laid-Open No. 2015-231647

Grinding wheels are manufactured by fixing multiple grinding wheels to an annular base with adhesive. When grinding a workpiece with the grinding wheel, the grinding wheels rotate at high speed and come into contact with the workpiece, placing a large load (processing load) on the grinding wheels. If the adhesive bonding the base and grinding wheels together has low toughness, the adhesive may break under the processing load while grinding the workpiece, resulting in insufficient fixing strength for the grinding wheels. As a result, the grinding wheels are more likely to fall off the base or break.

If the grinding wheel falls off or breaks, it could result in poor machining of the workpiece. Furthermore, grinding of the workpiece must be interrupted to replace the grinding wheel, which not only reduces the operating efficiency of the grinding equipment but also requires time and effort for the replacement work.

The present invention was made in consideration of these problems, and aims to provide a grinding wheel that can prevent the grinding stone from falling off or breaking.

According to one aspect of the present invention, there is provided a grinding wheel comprising an annular base and a grinding wheel fixed to the base, the grinding wheel being fixed in a groove provided in the base with an adhesive, the adhesive containing a reinforcing material that improves the toughness of the adhesive , the adhesive including an epoxy resin, the reinforcing material being silicone rubber particles, and the content of the silicone rubber particles in the adhesive being 2.5 wt % or more and 10 wt % or less .

Preferably , the content of the silicone rubber particles in the adhesive is 5 wt % or less .

Preferably, the grindstone is arranged so that its tip end is positioned radially outward of the base end.

In a grinding wheel according to one aspect of the present invention, the grinding stone is fixed to the base by an adhesive containing a reinforcing material. This improves the toughness of the adhesive and reduces the likelihood of the grinding stone falling off or breaking when grinding a workpiece with the grinding wheel.

FIG. FIG. 2 is a perspective view showing a first grinding wheel. FIG. 3A is a cross-sectional view showing the outer periphery of the first grinding wheel, and FIG. 3B is a cross-sectional view showing a part of the adhesive. FIG. 2 is a perspective view showing a chuck table and a grinding unit. FIG. 5A is a side view showing the chuck table and the grinding unit in the preparation step, and FIG. 5B is a side view showing the chuck table and the grinding unit in the grinding step. FIG. 2 is a perspective view showing a second grinding wheel. FIG. 7A is a cross-sectional view showing an example of the configuration of the outer periphery of the second grinding wheel, and FIG. 7B is a cross-sectional view showing another example of the configuration of the outer periphery of the second grinding wheel. FIG. 8(A) is a schematic diagram showing a method for measuring the strength of an adhesive, and FIG. 8(B) is a perspective view showing a grindstone for evaluation. FIG. 9A is a graph showing the relationship between the content of silicone rubber particles and adhesive strength, and FIG. 9B is a graph showing the relationship between the content of acrylic particles and adhesive strength.

An embodiment of the present invention will now be described with reference to the accompanying drawings. First, an example configuration of a grinding device capable of grinding a workpiece using a grinding wheel according to this embodiment will be described. Figure 1 is a perspective view showing a grinding device 2. Note that in Figure 1, the X-axis direction (processing feed direction, front-to-back direction, first horizontal direction) and the Y-axis direction (left-to-right direction, second horizontal direction) are mutually perpendicular. Furthermore, the Z-axis direction (vertical direction, up-down direction, height direction) is a direction perpendicular to the X-axis and Y-axis directions.

The grinding device 2 includes a base 4 that supports or houses each of the components that make up the grinding device 2. A rectangular opening 4a is formed on the top surface of the base 4, with its longitudinal direction aligned with the X-axis direction. Furthermore, a rectangular parallelepiped support structure 6 that protrudes upward from the top surface of the base 4 is provided at the rear end of the base 4 along the Z-axis direction.

A first movement mechanism (first movement unit) 8 is provided inside the opening 4a. For example, the first movement mechanism 8 is a ball screw-type movement mechanism that includes a pair of guide rails (not shown) arranged along the X-axis direction and a flat movement table (not shown) slidably mounted on the pair of guide rails. A nut portion is provided on the rear (lower) side of the movement table, and a ball screw (not shown) arranged between the pair of guide rails along the X-axis direction is threadedly engaged with this nut portion. A pulse motor (not shown) is also connected to the end of the ball screw. When the ball screw is rotated by the pulse motor, the movement table moves in the X-axis direction along the guide rails.

A chuck table (holding table) 10 that holds the workpiece 11 is provided on the surface (top) side of the moving table of the first moving mechanism 8. The first moving mechanism 8 also has a table cover 8a that surrounds the chuck table 10. Furthermore, accordion-shaped dust-proof and drip-proof covers 12 that are extendable and contractible along the X-axis direction are provided in front and behind the table cover 8a. The table cover 8a and dust-proof and drip-proof covers 12 cover the components of the first moving mechanism 8 (guide rails, moving table, ball screw, pulse motor, etc.) that are located inside the opening 4a.

The upper surface of the chuck table 10 is a flat surface roughly parallel to the horizontal plane (XY plane) and constitutes a holding surface 10a that holds the workpiece 11. The holding surface 10a is connected to a suction source (not shown) such as an ejector via a flow path (not shown) and a valve (not shown) formed inside the chuck table 10. Note that while Figure 1 shows an example in which the holding surface 10a is circular to accommodate a disk-shaped workpiece 11, the shape of the holding surface 10a can be modified as appropriate depending on the shape of the workpiece 11.

The chuck table 10 is moved along the X-axis direction together with the table cover 8a by the first movement mechanism 8. The chuck table 10 is also connected to a rotational drive source (not shown), such as a motor, that rotates the chuck table 10 around a rotation axis that is generally perpendicular to the holding surface 10a.

A second movement mechanism (second movement unit) 14 is provided on the front side of the support structure 6. The second movement mechanism 14 has a pair of guide rails 16 arranged along the Z-axis direction. A flat movement table 18 is slidably mounted on the pair of guide rails 16. A nut portion (not shown) is provided on the rear side (back side) of the movement table 18. A ball screw 20, which is arranged between the pair of guide rails 16 along the Z-axis direction, is threadedly engaged with this nut portion. A pulse motor 22 is also connected to the end of the ball screw 20. When the ball screw 20 is rotated by the pulse motor 22, the movement table 18 moves in the Z-axis direction along the pair of guide rails 16.

A support member 24 is fixed to the moving table 18, protruding forward from the front surface (surface) of the moving table 18. The support member 24 supports a grinding unit 26 that grinds the workpiece 11. The second moving mechanism 14 controls the movement (lifting and lowering) of the grinding unit 26 in the Z-axis direction.

The grinding unit 26 includes a hollow, cylindrical housing 28 supported by the support member 24. The housing 28 accommodates a cylindrical spindle 30 arranged along the Z-axis direction. The tip (lower end) of the spindle 30 protrudes downward from the underside of the housing 28. A rotational drive source (not shown), such as a motor, is connected to the base (upper end) of the spindle.

A disk-shaped wheel mount 32 made of metal or the like is fixed to the tip of the spindle 30. A grinding wheel 34 for grinding the workpiece 11 is attached to the underside of the wheel mount 32. The grinding wheel 34 rotates around a rotation axis that is approximately perpendicular to the holding surface 10a of the chuck table 10 by power transmitted from the rotational drive source via the spindle 30 and wheel mount 32.

A control unit (control unit, control device) 36 that controls the grinding device 2 is provided inside or outside the grinding device 2. The control unit 36 is connected to each component of the grinding device 2 (first movement mechanism 8, chuck table 10, second movement mechanism 14, grinding unit 26, etc.) and generates control signals to control the operation of each component.

For example, the control unit 36 is configured by a computer and includes an arithmetic unit that performs calculations necessary to control the grinding device 2, and a storage unit that stores various information (data, programs, etc.) used to control the grinding device 2. The arithmetic unit includes a processor such as a CPU (Central Processing Unit). The storage unit includes memory such as a ROM (Read Only Memory) and RAM (Random Access Memory).

The grinding device 2 described above grinds the workpiece 11. For example, the workpiece 11 is a disk-shaped wafer made of a semiconductor material such as silicon, and has a front surface 11a and a back surface 11b that are generally parallel to each other. The workpiece 11 is divided into multiple rectangular regions by multiple streets (planned division lines) arranged in a grid pattern so that they intersect with each other. Furthermore, devices (not shown), such as ICs (Integrated Circuits), LSIs (Large Scale Integration), and LEDs (Light Emitting Diodes), are formed on the front surface 11a of each of the multiple regions divided by the streets.

By dividing the workpiece 11 along the streets using cutting, laser processing, or the like, multiple device chips, each equipped with a device, are manufactured. Furthermore, if the back surface 11b of the workpiece 11 is ground using a grinding device 2 to thin the workpiece 11 before dividing it, a thinned device chip can be obtained.

There are no restrictions on the material, shape, structure, size, etc. of the workpiece 11. For example, the workpiece 11 may be a wafer (substrate) made of semiconductors other than silicon (GaAs, InP, GaN, SiC, etc.), sapphire, glass, ceramics, resin, metal, etc. Furthermore, there are no restrictions on the type, number, shape, structure, size, arrangement, etc. of devices formed on the workpiece 11, and the workpiece 11 does not necessarily have to have any devices formed on it. Furthermore, the workpiece 11 may be a package substrate such as a CSP (Chip Size Package) substrate or a QFN (Quad Flat Non-leaded package) substrate.

Figure 2 is a perspective view showing the grinding wheel (first grinding wheel) 34 attached to the grinding unit 26. The grinding wheel 34 includes an annular base 40 and a plurality of grinding wheels (grinding wheels) 42 fixed to the base 40.

The base 40 is made of metal (stainless steel, aluminum, etc.), resin, etc., and has a first surface (fixed end surface) 40a and a second surface (free end surface) 40b that are generally parallel to each other, and an outer peripheral surface (side surface) 40c connected to the first surface 40a and the second surface 40b. The diameter of the base 40 is generally the same as the diameter of the wheel mount 32 (see Figure 1) and larger than the diameter of the workpiece 11 (see Figure 1).

An opening 40d is provided in the center of the base 40, penetrating the base 40 in the thickness direction from the first surface 40a to the second surface 40b. The opening 40d is formed in a truncated cone shape, with its diameter gradually increasing from the first surface 40a to the second surface 40b.

A circular groove (recess) 40e is formed along the outer peripheral surface 40c of the base 40 on the second surface 40b side of the outer periphery of the base 40. A plurality of grinding stones 42 are fixed to the groove 40e. The grinding stones 42 are formed, for example, in a rectangular parallelepiped shape, and are arranged at approximately equal intervals along the circumferential direction of the base 40.

The grinding wheel 42 contains abrasive grains made of diamond, cBN (cubic boron nitride), or the like, and a binder (bond material) that secures the abrasive grains. Bonds that can be used include metal bonds, resin bonds, and vitrified bonds. However, there are no restrictions on the material, shape, structure, size, etc. of the grinding wheel 42, and these are set appropriately depending on the material of the workpiece 11 (see Figure 1) and the processing conditions. There is also no limit on the number of grinding wheels 42 that can be fixed to the base 40.

Note that while Figure 2 shows an example in which one groove 40e is formed in a ring shape, multiple rectangular parallelepiped grooves may be arranged in a ring shape along the circumferential direction of the base 40 on the second surface 40b side of the base 40. In this case, one or more grinding stones 42 are fixed to each of the multiple grooves.

The base 40 also has multiple grinding fluid supply paths 40f formed from the first surface 40a to the second surface 40b. The multiple grinding fluid supply paths 40f are arranged at approximately equal intervals along the circumferential direction of the base 40. One end of each grinding fluid supply path 40f opens on the first surface 40a side, and the other end of each grinding fluid supply path 40f opens in the area between the opening 40d and the groove 40e on the second surface 40b side. There are no restrictions on the number or shape of the grinding fluid supply paths 40f.

Figure 3(A) is a cross-sectional view showing the outer periphery of the grinding wheel 34. Note that Figure 3(A) only shows the cross section of the grinding wheel 34. The groove 40e includes side walls (inner walls) 40g and 40h that face each other inside the groove 40e, and a bottom surface 40i connected to the side walls 40g and 40h.

The grinding wheel 42 is fixed in the groove 40e via adhesive 44. Specifically, first, the adhesive 44 is applied to the side walls 40g, 40h and bottom surface 40i of the groove 40e. Next, the base end of the grinding wheel 42 is inserted into the groove 40e and comes into contact with the adhesive 44. When the adhesive 44 is cured in this state, the base 40 and the grinding wheel 42 are bonded via the adhesive 44. As a result, the tip of the grinding wheel 42 protrudes from the second surface 40b of the base 40, and the base end of the grinding wheel 42 is fixed inside the groove 40e. There are no restrictions on the material of the adhesive 44, as long as it can fix the grinding wheel 42 to the base 40. Furthermore, the adhesive 44 may be a one-component or two-component type.

Figure 3(B) is a cross-sectional view showing a portion of the adhesive 44. In this embodiment, the adhesive 44 contains a reinforcing material (modifier) 48 that improves the toughness of the adhesive 44. That is, the adhesive 44 includes a main material (base material) 46 made of a resin or the like, and granular reinforcing material 48 dispersed in the main material 46. There are no limitations on the method for dispersing the reinforcing material 48 in the main material 46. For example, a rotation-revolution type agitator (planetary type agitator) can be used to agitate and degas the liquid main material 46 and reinforcing material 48.

The main material 46 can be a thermosetting resin such as epoxy resin, phenol resin, melamine resin, cyanate resin, or urea resin. The hardening of the main material 46 can be accelerated by adding a hardener to the main material 46. For example, if the main material 46 is an epoxy resin, hardeners that can be used include phenol resin, acid anhydrides, amines, polyaminoamides, isocyanates, mercaptans, dicyandiamide, and Lewis acid complex compounds.

The reinforcing material 48 is an additive that improves the toughness of the main material 46 in a cured state. The reinforcing material 48 can be an elastomer (thermosetting elastomer or thermoplastic elastomer), engineering plastic, or the like.

Examples of elastomers include silicone rubber particles and acrylic particles. However, there are no restrictions on the elastomer material, and various types of elastomers, such as olefin-based, ester-based, and amide-based elastomers, can be used. Examples of engineering plastics include polycarbonate, polyamide, polyacetal, polybutylene terephthalate, polyphenylene sulfide, polyimide, and polyether ether ketone.

For example, consider a case where the main material 46 is epoxy resin and the reinforcing material 48 is silicone rubber particles. When the epoxy resin hardens, it shrinks, generating internal stress and making the epoxy resin brittle. However, if silicone rubber particles are dispersed in the epoxy resin, voids (cavitation) form in the silicone rubber particles when the epoxy resin shrinks, making the epoxy resin more susceptible to plastic deformation. This improves the toughness of the epoxy resin, making it less likely to break even when external force is applied.

The content of reinforcing material 48 in adhesive 44 is adjusted to improve the toughness of adhesive 44. For example, if the main material 46 is epoxy resin and the reinforcing material 48 is silicone rubber particles, the content of reinforcing material 48 is adjusted to 2.5 wt% or more and 10 wt% or less. Also, if the main material 46 is epoxy resin and the reinforcing material 48 is acrylic particles, the content of reinforcing material 48 is adjusted to 2.5 wt% or more and 5 wt% or less. Note that the above content corresponds to the ratio of the mass of reinforcing material 48 to the total mass of adhesive 44 including reinforcing material 48 (the sum of the mass of main material 46 and the mass of reinforcing material 48).

Furthermore, there are no restrictions on the size of the reinforcing material 48, as long as the reinforcing material 48 can be dispersed in the main material 46. For example, silicone rubber particles, acrylic particles, polycarbonate particles, etc., with an average particle size of 1 μm or more and 500 μm or less can be used.

Figure 4 is a perspective view showing the chuck table 10 and grinding unit 26. With the first surface 40a of the base 40 in contact with the underside of the wheel mount 32, the wheel mount 32 and grinding wheel 34 are fixed with fasteners such as bolts, thereby attaching the grinding wheel 34 to the wheel mount 32. The workpiece 11 is then held by the chuck table 10, and the grinding wheel 42 is brought into contact with the workpiece 11 while the chuck table 10 and grinding wheel 34 are rotated, thereby grinding the workpiece 11.

When the grinding wheel 42 comes into contact with the workpiece 11, pressure is applied from the workpiece 11 to the grinding wheel 42, placing a load (processing load) on the grinding wheel 42. If the adhesive 44 (see Figure 3(A)) has low toughness, the adhesive 44 may be damaged by the processing load while grinding the workpiece 11, resulting in insufficient fixing strength for the grinding wheel 42. As a result, the grinding wheel 42 is more likely to fall off the base 40 or become damaged.

However, in this embodiment, the adhesive 44 contains a reinforcing material 48 that improves the toughness of the adhesive 44 (see Figure 3(B)). This makes the adhesive 44 less likely to break during processing of the workpiece 11, and reduces the risk of the grinding wheel 42 falling off or being damaged.

Next, we will explain a specific example of a method for processing (grinding) the workpiece 11 using the grinding device 2. As an example, we will explain creep feed grinding, in which the workpiece 11 is processed by moving the chuck table 10 and the grinding wheel 34 relatively in a direction parallel to the holding surface 10a.

First, as shown in FIG. 4, the workpiece 11 is held by the chuck table 10 (holding step). For example, the workpiece 11 is placed on the chuck table 10 so that the front surface 11a faces the holding surface 10a and the back surface 11b is exposed upward. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 10a, the workpiece 11 is suction-held by the chuck table 10.

In addition, devices formed on the surface 11a of the workpiece 11 may be protected by applying a protective tape made of resin or the like to the surface 11a of the workpiece 11. In this case, the workpiece 11 is held by the chuck table 10 via the protective tape.

Next, the positional relationship between the chuck table 10 and the grinding unit 26 is adjusted (preparation step). Figure 5(A) is a side view showing the chuck table 10 and grinding unit 26 in the preparation step.

In the preparation step, the positional relationship between the chuck table 10 and the grinding unit 26 is adjusted so that the workpiece 11 held by the chuck table 10 and the grinding wheel 42 are spaced apart in the processing feed direction (X-axis direction) generally parallel to the holding surface 10a, and the lower surface of the grinding wheel 42 is positioned a predetermined distance below the upper surface (rear surface 11b) of the workpiece 11.

Specifically, first, the position of the chuck table 10 in the X-axis direction is adjusted by the first movement mechanism 8 (see FIG. 1) so that the workpiece 11 is positioned in front of the grinding wheel 34 (to the left of the page in FIG. 5A) without overlapping with the grinding wheel 34. The position of the grinding unit 26 in the Z-axis direction is also adjusted by the second movement mechanism 14 (see FIG. 1) so that the bottom surface of the grinding wheel 42 is positioned lower than the top surface of the workpiece 11. The difference ΔH in height (position in the Z-axis direction) between the top surface of the workpiece 11 and the bottom surface of the grinding wheel 42 at this time corresponds to the target value for the amount of workpiece 11 ground (the difference in thickness of the workpiece 11 before and after grinding) in the grinding step described below.

Next, while rotating the grinding wheel 34, the chuck table 10 and the grinding unit 26 are moved relative to each other in the processing feed direction (X-axis direction), and the workpiece 11 is ground from one end to the other end by the grinding wheel 42 (grinding step). Figure 5(B) is a side view showing the chuck table 10 and grinding unit 26 during the grinding step.

In the grinding step, the workpiece 11 is ground by creep feed grinding. Specifically, the spindle 30 is first rotated to rotate the grinding wheel 34 around a rotation axis that is approximately perpendicular to the holding surface 10a of the chuck table 10. The rotation speed of the grinding wheel 34 is set to, for example, between 1000 rpm and 3000 rpm.

Then, with the grinding wheel 34 rotating and the chuck table 10 not rotating, the chuck table 10 is moved along the X-axis direction at a predetermined speed by the first movement mechanism 8 (see Figure 1). As a result, the chuck table 10 and the grinding wheel 34 move relatively toward each other along the processing feed direction at a predetermined processing feed speed. The movement speed of the chuck table 10 (processing feed speed) is set, for example, to a range of 1 mm/s to 20 mm/s.

When the chuck table 10 moves and one end of the workpiece 11 (the front end in the direction of movement of the workpiece 11, the right end on the paper in Figure 5(B)) reaches the trajectory of the grinding wheel 42, that end is ground away by the grinding wheel 42. The chuck table 10 then moves along the X-axis direction until the other end of the workpiece 11 (the rear end in the direction of movement of the workpiece 11, the left end on the paper in Figure 5(B)) is positioned so that it overlaps with the trajectory of the grinding wheel 42. As a result, the workpiece 11 is ground from one end to the other by the grinding wheel 42, and the entire workpiece 11 is thinned.

When the workpiece 11 is ground by the grinding wheel 42, a liquid (grinding fluid) such as pure water is supplied to the workpiece 11 and the grinding wheel 42. For example, the grinding fluid is supplied to the workpiece 11 and the grinding wheel 42 via a grinding fluid supply path (not shown) provided inside the grinding unit 26 and a grinding fluid supply path 40f (see Figure 2) provided on the grinding wheel 34. This cools the workpiece 11 and the grinding wheel 42 and washes away debris (grinding debris) generated during the grinding process. There are no limitations on the method of supplying the grinding fluid; for example, the grinding fluid may be supplied from a nozzle provided on the outside of the grinding wheel 34.

Then, grinding of the workpiece 11 is repeated until the thickness of the workpiece 11 reaches the final target thickness (finishing thickness). The number of creep feed grinding operations (the number of times the preparation step and grinding step are performed) can be set appropriately depending on the material of the workpiece 11, the amount of grinding, etc.

In creep feed grinding, the side of the grinding wheel 42 collides with the workpiece 11, placing a large load on the grinding wheel 42 in the lateral direction (XY plane direction), making it prone to falling off or breakage. However, in this embodiment, the grinding wheel 42 is fixed to the base 40 by an adhesive 44 (see Figure 3 (B)) containing a reinforcing material 48 that improves the toughness of the adhesive 44. This makes it less likely for the grinding wheel 42 to fall off or break even when creep feed grinding is performed.

The specific structure of the grinding wheel attached to the grinding unit 26 can be modified as needed. Figure 6 is a perspective view showing a grinding wheel (second grinding wheel) 34A, which corresponds to a modified version of the grinding wheel 34. The grinding wheel 34A includes an annular base 50 and multiple grinding wheels (grinding wheels) 52 fixed to the base 50.

The base 50 is made of metal (stainless steel, aluminum, etc.), resin, etc., and has a first surface (fixed end surface) 50a and a second surface (free end surface) 50b that are generally parallel to each other, and an outer peripheral surface (side surface) 50c connected to the first surface 50a and the second surface 50b. The diameter of the base 50 is generally the same as the diameter of the wheel mount 32 (see Figure 1) and larger than the diameter of the workpiece 11 (see Figure 1).

An opening 50d is provided in the center of the base 50, penetrating the base 50 in the thickness direction from the first surface 50a to the second surface 50b. The opening 50d is formed in a truncated cone shape, with its diameter gradually increasing from the first surface 50a to the second surface 50b.

A circular groove (recess) 50e is formed along the outer peripheral surface 50c of the base 50 on the second surface 50b side of the outer periphery. A plurality of grinding stones 52 are fixed to the groove 50e. The grinding stones 52 are formed, for example, in a rectangular parallelepiped shape and are arranged at approximately equal intervals along the circumferential direction of the base 50. Examples of materials for the grinding stones 52 are the same as those for the grinding stone 42 (see Figure 2, etc.).

The base 50 also has multiple grinding fluid supply channels 50f formed therein, penetrating the base 50 in the thickness direction. The multiple grinding fluid supply channels 50f are arranged at approximately equal intervals along the circumferential direction of the base 50. One end of each grinding fluid supply channel 50f opens on the first surface 50a side, and the other end of each grinding fluid supply channel 50f opens in the region between the opening 50d and the groove 50e on the second surface 50b side. There are no restrictions on the number or shape of the grinding fluid supply channels 40f.

Figure 7(A) is a cross-sectional view showing an example of the configuration of the outer periphery of grinding wheel 34A. Note that Figure 7(A) only shows the cross section of grinding wheel 34A. Groove 50e includes a pair of side walls 50g, 50h connected to each other at their lower ends. Side walls 50g, 50h are formed so as to be inclined with respect to the thickness direction of base 50. Grindstone 52 is bonded to base 50 via adhesive 44 applied to side walls 50g, 50h of groove 40e. As a result, the tip (one end) of grindstone 52 protrudes from second surface 50b of base 50, and the base (other end) of grindstone 52 is fixed inside groove 50e.

The grindstone 52 is fixed in the groove 40e so that its height direction is inclined relative to the thickness direction of the base 50. Specifically, the grindstone 52 is positioned so that its tip is positioned radially outward of the base 50 relative to its base end. The tip of the grindstone 52 is also shaped into a flat surface so that it is generally parallel to the first surface 50a and second surface 50b of the base 50.

When creep feed grinding (see Figures 5(A) and 5(B)) of the workpiece 11 is performed using the grinding wheel 34A, the sharp tip of the grindstone 52 comes into contact with the workpiece 11. This makes it easier to remove the workpiece 11, improving the efficiency of grinding the workpiece 11.

There are no restrictions on the shape of the groove 50e. Figure 7(B) is a cross-sectional view showing another example of the configuration of the outer periphery of the grinding wheel 34A. As shown in Figure 7(B), the groove 50e may include side walls (inner walls) 50i, 50j that face each other inside the groove 50e, and a bottom surface 50k connected to the side walls 50i, 50j. In this case, the grinding wheel 52 is fixed to the base 50 via adhesive 44 applied to the side walls 50i, 50j and bottom surface 50k of the groove 50e.

When the grinding wheel 52 is fixed in the groove 50e shown in Figure 7(B), both side surfaces of the grinding wheel 52 located on the outer peripheral surface 50c side and the center side of the base 50 are supported by the side walls 50i, 50j via the adhesive 44. This more effectively prevents the grinding wheel 52 from falling off or being damaged during grinding of the workpiece 11.

As described above, in the grinding wheel 34 according to this embodiment, the grinding stone 42 is fixed to the base 40 by the adhesive 44 containing the reinforcing material 48. This improves the toughness of the adhesive 44, reducing the likelihood of the grinding stone 42 falling off or breaking when the grinding wheel 34 is used to grind the workpiece 11.

The structures, methods, etc., described in the above embodiments can be modified as appropriate without departing from the scope of the present invention.

Example 1
Next, the results of evaluating the strength of the adhesive that bonds the grinding wheel base and the grinding stone will be described. Fig. 8(A) is a perspective view showing a method for measuring the adhesive strength. In this evaluation, a grinding stone (grinding stone) 60 was fixed to a support (base) 64 with adhesive 62, and force was applied to the grinding stone 60 to measure the strength of the adhesive 62.

First, a rectangular parallelepiped grinding wheel 60 was formed by fixing abrasive grains (diamond) with a bonding material (copper-tin bond). Figure 8(B) is a perspective view showing the evaluation grinding wheel 60. The dimensions of the grinding wheel 60 were length L = 19 mm, width W = 9.5 mm, and height H = 3 mm.

Next, adhesive 62 was applied to the side surface 60a of the grinding wheel 60, and the grinding wheel 60 and support base 64 were bonded via the adhesive 62. Similar to adhesive 44 (see Figure 3(B)), adhesive 62 was created by dispersing a reinforcing material in a main material. In this example, epoxy resin was used as the main material, and dicyandiamide and imidazole were used as hardeners. Silicone rubber particles (average particle size 13 μm) were used as the reinforcing material. For ease of explanation, the thickness of adhesive 62 is exaggerated in Figure 8(A).

Next, a cylindrical indenter 66 (3 mm diameter) was lowered and pressed against the upper surface 60b of the grinding wheel 60, applying an external force to the grinding wheel 60. The indenter 66 was lowered at a speed of 0.5 mm/min. The indenter 66 was then lowered until the adhesive 62 was broken and the grinding wheel 60 was separated from the support base 64. The load applied to the indenter 66 during the descent was measured and the maximum load value was recorded. This maximum load value corresponds to the adhesive strength [N] between the grinding wheel 60 and the support base 64. A Shimadzu testing machine (model number: AG-50kNG) was used to measure the load.

The above measurements were performed twice for each of seven types of adhesive 62 with different silicone rubber particle content (14 times in total), and the average adhesive strength was calculated for each silicone rubber particle content. The silicone rubber particle content of the seven types of adhesive 62 was adjusted to 0 wt%, 2.5 wt%, 5 wt%, 7.5 wt%, 10 wt%, 12.5 wt%, and 15 wt%, respectively.

Figure 9(A) is a graph showing the relationship between silicone rubber particle content and adhesive strength (average value). As shown in Figure 9(A), when the silicone rubber particle content in adhesive 62 was 2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt%, adhesive strength was improved compared to when adhesive 62 contained no silicone rubber particles (0 wt%). From these results, it can be said that when using epoxy resin as the main material and silicone rubber particles as the reinforcing material, it is preferable to set the silicone rubber particle content in adhesive 62 to between 2.5 wt% and 10 wt%.

When the bonded surfaces were observed after the grinding wheel 60 and support base 64 were separated, adhesive 62 was found to remain on both the grinding wheel 60 and support base 64. Therefore, the adhesive strength shown in Figure 9 (A) indicates the strength (toughness) of the adhesive 62 containing silicone rubber particles.

Example 2
Next, the evaluation results when acrylic particles (average particle size 150 μm) were used as the reinforcing material will be described. The material of the adhesive 62 used in this example was the same as in Example 1, except for the reinforcing material. The same measurements as in Example 1 were performed twice for each of five types of adhesive 62 with different acrylic particle contents (10 times in total), and the average adhesive strength was calculated for each acrylic particle content. The acrylic particle contents of the five types of adhesive 62 were adjusted to 0 wt%, 2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt%, respectively.

Figure 9(B) is a graph showing the relationship between the acrylic particle content and adhesive strength (average value). As shown in Figure 9(B), when the acrylic particle content in adhesive 62 is 2.5 wt% or 5 wt%, the adhesive strength is improved compared to when adhesive 62 does not contain acrylic particles (0 wt%). From these results, it can be said that when using epoxy resin as the main material and acrylic particles as the reinforcing material, it is preferable to set the acrylic particle content in adhesive 62 to 2.5 wt% or more and 5 wt% or less.

When the bonded surfaces were observed after the grinding wheel 60 and support base 64 were separated, adhesive 62 was found to remain on both the grinding wheel 60 and support base 64. Therefore, the adhesive strength shown in Figure 9 (B) indicates the strength (toughness) of the adhesive 62 containing acrylic particles.

The above results confirm that the toughness of adhesive 62 can be improved by adding an appropriate amount of reinforcing material to adhesive 62.

11 Workpiece 11a Front surface 11b Back surface 2 Grinding device 4 Base 4a Opening 6 Support structure 8 First moving mechanism (first moving unit)
8a Table cover 10 Chuck table (holding table)
10a Holding surface 12 Dustproof/waterproof cover 14 Second moving mechanism (second moving unit)
16 Guide rail 18 Moving table 20 Ball screw 22 Pulse motor 24 Support member 26 Grinding unit 28 Housing 30 Spindle 32 Wheel mount 34 Grinding wheel (first grinding wheel)
34A Grinding wheel (second grinding wheel)
36 Control unit (control unit, control device)
40 Base 40a First surface (fixed end surface)
40b Second surface (free end surface)
40c Outer surface (side surface)
40d: opening 40e: groove (recess)
40f: Grinding fluid supply path 40g, 40h: Side wall (inner wall)
40i Bottom 42 Grinding wheel (grinding wheel)
44 Adhesive 46 Main material (base material)
48 Reinforcing material (modifier)
50 Base 50a First surface (fixed end surface)
50b 2nd surface (free end surface)
50c Outer surface (side surface)
50d: opening 50e: groove (recess)
50f: grinding fluid supply path 50g, 50h: side wall 50i, 50j: side wall (inner wall)
50k bottom 52 grinding wheel (grinding wheel)
60 Grinding wheel (grinding wheel)
60a Side surface 60b Top surface 62 Adhesive 64 Support base (base)
66 Indenter

Claims (3)

A grinding wheel comprising an annular base and a grinding stone fixed to the base,
The grindstone is fixed in a groove provided in the base with an adhesive,
the adhesive contains a reinforcing material that improves the toughness of the adhesive;
The adhesive comprises an epoxy resin;
the reinforcing material is silicone rubber particles;
The content of the silicone rubber particles in the adhesive is 2.5 wt % or more and 10 wt % or less. 2. The grinding wheel according to claim 1, wherein the content of the silicone rubber particles in the adhesive is 5 wt % or less. 3. The grinding wheel according to claim 1, wherein the grindstone is disposed so that a tip end thereof is positioned radially outward of the base end thereof.