TWI891931B - Grinding method and grinding device for workpiece - Google Patents

Abstract

[Topic] To provide a workpiece grinding method that can suppress the occurrence of machining defects. [Solution] A method for grinding a workpiece comprises grinding the workpiece using a grinding device, the grinding device comprising: a holding table for holding the workpiece with a holding surface; and a grinding unit for grinding the workpiece held by the holding table with a grinding wheel having a plurality of grinding stones arranged in a ring, the method for grinding the workpiece comprising the following steps: a groove forming step, in which the grinding stones are brought into contact with the workpiece without rotating the holding table and the grinding wheel is rotated, thereby grinding the workpiece to form an arc-shaped groove in the workpiece having a depth that does not reach the thickness of the finished product; and a grinding step, in which the grinding stones are brought into contact with the surface of the workpiece on which the groove is formed, while the holding table and the grinding wheel are rotated, and the workpiece is ground until the thickness of the workpiece reaches the thickness of the finished product.

Description

Grinding method and grinding device for workpiece

The present invention relates to a method for grinding a workpiece and a grinding device for grinding the workpiece.

The device chip manufacturing process uses a wafer with devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) formed in areas defined by a plurality of intersecting predetermined dicing lines (slicing streets). By dicing this wafer along the predetermined dicing lines, multiple device chips, each containing a device, are produced. Device chips are used in various electronic devices, such as mobile phones and personal computers.

In recent years, with the miniaturization of electronic devices, there has been an increasing demand for thinner device chips. Therefore, a method has been used to thin wafers by grinding them before they are separated. Wafer grinding uses a grinding device equipped with a holding table and a grinding unit. The holding table holds the wafer, while the grinding unit grinds the wafer.

The grinding unit of the grinding device is equipped with a grinding wheel having a plurality of grinding stones arranged in a ring. The grinding stones are formed by fixing abrasive grains such as diamonds with a binder. With the wafer held by a holding table, the holding table and grinding wheel are rotated while the grinding stones contact the wafer to grind the wafer (see Patent Document 1).

Prior Art Literature Patent Literature

Patent Document 1: Japanese Patent Application Publication No. 2009-90389

During grinding, the workpiece is machined by bringing abrasive grains protruding from the binder of the grinding stone into contact with the workpiece. Therefore, it is desirable to maintain a moderate protrusion of the abrasive grains from the binder during grinding.

When a grinding stone impacts the workpiece, abrasive grains gradually break away from the bond. However, if grinding continues even after the abrasive grains have fallen away, a phenomenon known as self-edging occurs: the bond and workpiece come into contact and wear away, exposing new abrasive grains from the bond. This self-edging maintains the abrasive grains protruding from the bond, preventing a reduction in the grinding performance of the grinding stone.

However, the abrasive grains sometimes fall off earlier depending on the workpiece material or the condition of the surface being ground. For example, if a thin film, such as an oxide film, forms on the surface being ground, the abrasive grains become trapped in the film, making them more likely to fall off. In such cases, the period from abrasive grain falloff until the self-sharpening of the edge—in other words, the period during which the workpiece is ground with the grinding stone's reduced grinding performance—is prolonged, making it more likely that defects will occur in the workpiece.

The present invention was made in view of the above-mentioned problems, and its object is to provide a method and a grinding device for grinding a workpiece that can suppress the occurrence of machining defects.

According to one aspect of the present invention, a method for grinding a workpiece can be provided, wherein the method uses a grinding device to grind the workpiece, wherein the grinding device comprises: a holding table for holding the workpiece with a holding surface; and a grinding unit for grinding the workpiece held by the holding table with a grinding wheel having a plurality of grinding stones arranged in a ring shape. The method for grinding the workpiece comprises the following steps: a groove forming step, wherein the groove is formed without the holding table; The work table rotates, and while the grinding wheel is rotating, the grinding stone is brought into contact with the workpiece to grind the workpiece, thereby forming an arc-shaped groove in the workpiece that has a depth that does not reach the thickness of the finished product. Furthermore, the grinding step includes, while the holding table and the grinding wheel are rotating, bringing the grinding stone into contact with the surface of the workpiece where the groove is formed, and grinding the workpiece until the thickness of the workpiece reaches the thickness of the finished product.

Furthermore, preferably, in the groove forming step, the angle of the holding table in the rotational direction is set to a predetermined angle. Furthermore, preferably, in the groove forming step, the workpiece is ground at different angles in the rotational direction of the holding table, thereby forming a plurality of grooves in the workpiece.

According to another aspect of the present invention, a grinding device is provided, comprising: a holding table for holding a workpiece with a holding surface; a grinding unit for grinding the workpiece held by the holding table with a grinding wheel having a plurality of grinding stones arranged in a ring; a grinding feed unit for moving the holding table and the grinding unit relative to each other in a direction perpendicular to the holding surface; and a control unit for controlling the holding table, the grinding unit, and the grinding feed unit, wherein the control unit is capable of switching the first The first mode and the second mode are described. In the first mode, the grinding wheel is rotated while the holding table is not rotated, and the grinding stone is brought into contact with the workpiece by the grinding feed unit, thereby forming a groove in the workpiece that does not reach the thickness of the finished product. In the second mode, the grinding wheel is rotated while the holding table and the grinding wheel are rotated, and the grinding stone is brought into contact with the surface of the workpiece where the groove is formed, thereby grinding the workpiece until the thickness of the workpiece reaches the thickness of the finished product.

Furthermore, it is preferred that the control unit can control the angle of the holding table in the rotation direction.

In one aspect of the workpiece grinding method and apparatus of the present invention, after forming an arcuate groove in the workpiece that does not reach the finished product thickness, a grinding stone is brought into contact with the grooved surface of the workpiece and the workpiece is ground until its thickness reaches the finished product thickness. As the workpiece is ground and thinned, the grinding stone impacts the groove, promoting self-sharpening. As a result, the grinding stone's grinding performance is maintained, preventing defects from occurring.

2: Grinding device

4,46:Abutment

4a: Opening

6: Transport unit (transport mechanism)

8a, 8b: Cassette mounting area

10a, 10b: Film cassette

11: Workpiece

11a: Front (Side 1)

11b: Back (Side 2)

11c: Groove

11d: Grinding marks (saw marks)

12: Alignment mechanism (calibration mechanism)

14: Transport unit (transport mechanism, loading arm)

16: Turntable

18: Maintaining the workbench (work clamp)

18a: Maintaining the surface

20: Rotational drive source

22a, 22b: Support structure

24a, 24b: Grinding feed unit (moving unit, moving mechanism)

26: Guide Rail

28:Mobile board

30: Ball screw

32: Pulse Motor

34a, 34b: Grinding unit

36: Shell

38: Main axis

40: Rotational drive source

42: Mounting seat

44a, 44b: Grinding wheel

48: Grinding Stone

50:Thickness gauge

52a, 52b: Altimeter (altimeter)

54: Transport unit (transport mechanism, unloading arm)

56: Washing unit (washing mechanism)

58: Control unit (control part)

α:arrow

A:Transportation location

B: 1st grinding position (rough grinding position)

C: Second grinding position (finishing grinding position)

X, Y, Z: Direction

Figure 1 is a perspective view of the grinding device.

Figure 2 is a front view of the grinding device.

Figure 3(A) is a front view of the grinding device during the groove forming step, and Figure 3(B) is a plan view of the holding table and grinding wheel during the groove forming step.

Figure 4(A) is a plan view of a workpiece with a groove formed therein, and Figure 4(B) is a plan view of a workpiece with multiple grooves formed therein.

Figure 5(A) is a front view of the grinding device during the grinding step, and Figure 5(B) is a plan view of the holding table and grinding wheel during the grinding step.

Figure 6 is an enlarged cross-sectional view showing a portion of a workpiece being ground by a grinding stone.

Figure 7 is a plan view of the workpiece after grinding.

Form used to implement the invention

The following describes an embodiment of one aspect of the present invention with reference to the accompanying drawings. First, an example configuration of a grinding device that can be used in the workpiece processing method of this embodiment will be described. FIG1 is a perspective view of a grinding device 2. Furthermore, in FIG1 , the X-axis direction (left-right direction, first horizontal direction) and the Y-axis direction (front-back direction, second horizontal direction) are perpendicular to each other. Furthermore, the Z-axis direction (vertical direction, up-down direction, height direction) is perpendicular to the X-axis and Y-axis directions.

The grinding device 2 includes a base 4 that supports and houses the various components that make up the grinding device 2. A rectangular opening 4a is provided on the top surface of the front end of the base 4. A transport unit (transport mechanism) 6 is located within the opening 4a. This transport unit (transport mechanism) 6 transports the workpiece 11 to be processed by the grinding device 2.

Cassette mounting areas 8a and 8b are provided on both sides of the transport unit 6. Cassettes 10a and 10b for accommodating workpieces 11 are mounted on the cassette mounting areas 8a and 8b, respectively. Cassette 10a can accommodate a plurality of workpieces 11 predetermined for processing by the grinding device 2 (pre-processed workpieces 11). Cassette 10b, on the other hand, can accommodate a plurality of workpieces 11 already processed by the grinding device 2 (post-processed workpieces 11).

For example, the workpiece 11 is a disk-shaped silicon wafer having a front surface (first surface) 11a and a back surface (second surface) 11b that are substantially parallel to each other. The workpiece 11 is divided into a plurality of rectangular regions by a plurality of predetermined dividing lines (slicing streets) arranged in a grid pattern. Furthermore, devices such as ICs and LSIs are formed on the front surface 11a of the regions defined by the predetermined dividing lines.

By dividing the workpiece 11 along predetermined dividing lines, multiple device wafers, each containing a device, can be produced. Furthermore, by grinding and thinning the workpiece 11 using the grinding device 2 before dividing, thinned device wafers can be obtained.

However, there are no restrictions on the type, material, size, shape, or structure of the workpiece 11. For example, the workpiece 11 may be a substrate made of semiconductors other than silicon (such as gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), or silicon carbide (SiC)), glass, ceramics, resin, or metal. Furthermore, there are no restrictions on the type, number, shape, structure, size, or placement of devices formed on the workpiece 11, and the workpiece 11 may not even have devices formed on it.

An alignment mechanism (calibration mechanism) 12 is located diagonally behind the opening 4a. The workpiece 11 contained in the cassette 10a is transported to the alignment mechanism 12 by the transport unit 6. The alignment mechanism 12 then aligns the workpiece 11 at a predetermined position.

Adjacent to the alignment mechanism 12 is a transport unit (transport mechanism, loading arm) 14 that transports the workpiece 11. The transport unit 14 includes a suction pad that attracts and holds the top surface of the workpiece 11. The transport unit 14 then rotates the suction pad while holding the workpiece 11, aligned by the alignment mechanism 12, to transport the workpiece 11 rearward.

A disc-shaped turntable 16 is installed behind the conveyor unit 14. A rotational drive source (not shown), such as a servo motor, is connected to the turntable 16, and the rotational drive source rotates the turntable 16 about a rotation axis that is generally parallel to the Z-axis.

A plurality of holding tables (work clamps) 18 are mounted on the turntable 16 to hold the workpiece 11. Figure 1 shows an example in which three holding tables 18 are arranged at approximately equal intervals along the circumference of the turntable 16. The turntable 16 rotates counterclockwise (indicated by arrow α) when viewed from above, positioning each holding table 18 in the order of transport position A, first grinding position (rough grinding position) B, second grinding position (finish grinding position) C, and transport position A.

Each holding table 18 is connected to a rotational drive source 20 (see Figure 2) for rotating the holding table 18. For example, the rotational drive source 20 may be a servo motor, and rotates the holding table 18 about a rotation axis generally parallel to the Z-axis. Furthermore, the rotational drive source 20 includes a detector (encoder) for detecting the rotation angle of the output shaft of the rotational drive source 20 (the rotation angle of the holding table 18).

A columnar support structure 22a is located behind the first grinding position B, and a columnar support structure 22b is located behind the second grinding position C. A grinding feed unit (moving unit, moving mechanism) 24a is located in front of the support structure 22a, and a grinding feed unit (moving unit, moving mechanism) 24b is located in front of the support structure 22b.

Each grinding feed unit 24a, 24b includes a pair of guide rails 26 arranged roughly parallel to the Z-axis. A plate-shaped moving plate 28 is mounted on the guide rails 26 so as to slide along the guide rails 26. A nut (not shown) is provided on the rear surface (back side) of the moving plate 28. A ball screw 30 arranged roughly parallel to the guide rails 26 is screwed into the nut. A pulse motor 32 is connected to the end of the ball screw 30. When the pulse motor 32 rotates the ball screw 30, the moving plate 28 moves along the Z-axis.

A grinding unit 34a, which performs rough grinding of the workpiece 11, is fixed to the front surface (front side) of the movable plate 28 of the grinding feed unit 24a. Meanwhile, a grinding unit 34b, which performs fine grinding of the workpiece 11, is fixed to the front surface (front side) of the movable plate 28 of the grinding feed unit 24b. The grinding feed units 24a and 24b raise and lower the grinding units 34a and 34b, thereby moving the holding table 18 relative to the grinding units 34a and 34b in a direction perpendicular to the holding surface 18a of the holding table 18 (see Figure 2).

Grinding units 34a and 34b each have a hollow cylindrical housing 36. Housing 36 houses a cylindrical spindle 38 (see Figure 2) arranged along the Z-axis. The front end (lower end) of spindle 38 protrudes from housing 36. A rotational drive source 40 is connected to the base end (upper end) of spindle 38. For example, rotational drive source 40 can be a servo motor, which rotates spindle 38 about an axis generally parallel to the Z-axis.

Figure 2 is a front view of the grinding device 2. Figure 2 shows the holding table 18 and the grinding unit 34a positioned at the first grinding position B.

The top surface of the holding table 18 forms a holding surface 18a for holding the workpiece 11. The holding surface 18a is a flat surface roughly parallel to the X- and Y-axes, and is formed, for example, into a circular shape corresponding to the shape of the workpiece 11. Furthermore, the holding surface 18a is connected to a suction source (not shown), such as an ejector, via a flow path (not shown) and a valve (not shown) formed within the holding table 18. With the workpiece 11 positioned on the holding surface 18a, negative pressure from the suction source is applied to the holding surface 18a, allowing the holding table 18 to suction and hold the workpiece 11.

A disc-shaped mounting base 42, made of metal or the like, is fixed to the lower end of the main shaft 38 of the grinding unit 34a. A grinding wheel 44a for rough grinding is mounted on the lower surface of the mounting base 42. The grinding wheel 44a rotates about an axis generally parallel to the Z-axis direction, driven by power transmitted from a rotational drive source 40 (see Figure 1) through the main shaft 38 and the mounting base 42.

The grinding wheel 44a includes an annular base 46 made of a metal such as aluminum or stainless steel and having a diameter approximately the same as that of the mounting base 42. On the underside of the base 46, a plurality of rectangular grinding stones 48 are arranged in a ring along the circumference of the base 46. For example, the grinding stones 48 can be formed by fixing abrasive grains such as diamond or cBN (cubic boron nitride) with a bonding material such as a metal bond, a resin bond, or a vitrified bond. However, there are no restrictions on the material, shape, structure, size, etc. of the grinding stones 48, and the number of grinding stones 48 included in the grinding wheel 44a can be arbitrarily set.

The grinding unit 34b shown in Figure 1 is constructed similarly to the grinding unit 34a. Furthermore, a grinding wheel 44b for fine grinding is mounted on the lower surface of the mounting base 42 of the grinding unit 34b. The construction of the grinding wheel 44b is similar to that of the grinding wheel 44a. However, the average particle size of the abrasive grains in the grinding stone 48 of the grinding wheel 44b is smaller than that of the grinding stone 48 of the grinding wheel 44a.

The grinding unit 34a uses a grinding wheel 44a to grind the workpiece 11 held by the holding table 18 positioned at the first grinding position B. This rough grinding is performed on the workpiece 11. The grinding unit 34b uses a grinding wheel 44b to grind the workpiece 11 held by the holding table 18 positioned at the second grinding position C. This fine grinding is performed on the workpiece 11.

Furthermore, grinding fluid supply passages (not shown) for supplying a liquid (grinding fluid) such as pure water are provided inside or near each of the grinding units 34a and 34b. During the grinding process, the grinding fluid is supplied to the workpiece 11 and the grinding stone 48.

Thickness measuring devices 50 are installed near the holding table 18 positioned at the first grinding position B and near the holding table 18 positioned at the second grinding position C. Each thickness measuring device 50 measures the thickness of the workpiece 11 held by the holding table 18. The thickness measuring device 50 includes a height measuring device (height gauge) 52a for measuring the height of the top surface of the workpiece 11 held by the holding table 18, and a height measuring device (height gauge) 52b for measuring the height of the top surface (holding surface 18a) of the holding table 18. The thickness measuring device 50 calculates the thickness of the workpiece 11 based on the difference between the values measured by the height measuring devices 52a and 52b.

Adjacent to the transport unit 14 in the X-axis direction is a transport unit (transport mechanism, unloading arm) 54 for transporting the workpiece 11. The transport unit 54 includes a suction pad that attracts and holds the top surface of the workpiece 11. The transport unit 54 uses the suction pad to hold the workpiece 11 held by the holding table 18 at transport position A and rotates the suction pad to transport the workpiece 11 forward.

A cleaning unit (cleaning mechanism) 56 is located in front of the transport unit 54. The cleaning unit 56 cleans the workpiece 11 transported by the transport unit 54. The workpiece 11 cleaned by the cleaning unit 56 is then transported by the transport unit 6 and placed in the cassette 10b.

The grinding apparatus 2 also includes a control unit (control section) 58 connected to each component of the grinding apparatus 2 (such as the conveying unit 6, the positioning mechanism 12, the conveying unit 14, the turntable 16, the holding table 18, the rotary drive source 20, the grinding feed units 24a and 24b, the grinding units 34a and 34b, the thickness gauge 50, the conveying unit 54, and the cleaning unit 56). The control unit 58 controls the operation of the components of the grinding apparatus 2.

For example, the control unit 58 can be configured as a computer and include a processing unit and a memory unit. The processing unit performs the calculations and other processing required for the operation of the grinding device 2, while the memory unit stores various information (data, programs, etc.) used in the processing performed by the processing unit. The processing unit includes a processor such as a CPU (Central Processing Unit). The memory unit includes various memories that function as main memory devices, auxiliary memory devices, etc. The control unit 58 generates signals (control signals) for controlling the components of the grinding device 2 by executing the programs stored in the memory unit.

Next, a specific example of a workpiece grinding method using the grinding device 2 to grind the workpiece 11 will be described. As an example, the following description focuses on a case where the back surface 11b of the workpiece 11 is ground to thin the workpiece 11 until the thickness reaches a predetermined thickness (finished product thickness).

First, the workpiece 11 to be ground by the grinding device 2 is placed in the magazine 10a and set on the magazine setting area 8a. The transport unit 6 then removes the workpiece 11 from the magazine 10a and transports it to the alignment mechanism 12, where the alignment mechanism 12 aligns the workpiece 11. The transport unit 14 then transports the workpiece 11 from the alignment mechanism 12 to the holding table 18, which is positioned at the transport position A.

For example, as shown in Figure 2, the workpiece 11 is placed on the holding table 18 with its front side 11a facing the holding surface 18a and its back side 11b exposed upward. In this position, applying negative pressure from a suction source to the holding surface 18a allows the workpiece 11 to be held by the holding table 18. Furthermore, if a device is formed on the front side 11a of the workpiece 11, protective tape can be attached to the front side 11a of the workpiece 11 to protect the device. In this case, the workpiece 11 is held by the holding table 18 through the protective tape.

Next, the turntable 16 is rotated to position the holding table 18 holding the workpiece 11 at the first grinding position B. The grinding unit 34a then grinds the workpiece 11 held by the holding table 18.

In this embodiment, the workpiece 11 is first ground by the grinding unit 34a to form an arc-shaped groove in the workpiece 11 (groove forming step). Figure 3(A) is a front view of the grinding device 2 showing the groove forming step.

In the groove forming step, the rotational angle of the holding table 18 is first set to a predetermined angle (e.g., an initial angle of 0°) by the rotational drive source 20. Then, without rotating the holding table 18, the rotational drive source 40 (see Figure 1) rotates the grinding wheel 44a at a predetermined number of revolutions. At this point, the grinding stone 48 of the grinding wheel 44a rotates until it overlaps the center of the workpiece 11. The grinding feed unit 24a then lowers the grinding wheel 44a at a predetermined speed (grinding feed), bringing the rotating grinding stone 48 into contact with the back surface 11b (grinded surface) of the workpiece 11.

As the grinding wheel 44a is lowered while the grinding stone 48 contacts the back surface 11b of the workpiece 11, the back surface 11b of the workpiece 11 is ground by the grinding stone 48. Furthermore, the lowering speed of the grinding wheel 44a is adjusted to press the grinding stone 48 against the back surface 11b of the workpiece 11 with an appropriate force.

Figure 3(B) is a plan view of the holding table 18 and grinding wheel 44a during the groove forming step. If the grinding wheel 44a is rotated to grind the workpiece 11 without rotating the holding table 18, the workpiece 11 is ground along the path of the rotating grinding stone 48. As a result, an arc-shaped groove 11c having the same width as the grinding stone 48 is formed on the back surface 11b of the workpiece 11.

Figure 4(A) shows a plan view of a workpiece 11 having a groove 11c formed therein. The groove 11c is formed in an arc shape, extending from one end of the workpiece 11 through the center to the other end. When the amount of workpiece 11 removed (the depth of the groove 11c) reaches a predetermined value, grinding of the workpiece 11 by the grinding wheel 44a is stopped. Furthermore, the groove 11c is formed to a depth that does not reach the final thickness (finished product thickness) of the workpiece 11 after grinding in the grinding step described below. For example, the depth of the groove 11c can be set so that the difference between the final thickness of the workpiece 11 and the thickness of the groove 11c is at least 20 μm.

During the groove forming step, multiple grooves 11c may be formed in the workpiece 11. In this case, after forming the first groove 11c, the rotary drive source 20 rotates the holding table 18 by a predetermined angle, thereby changing the angle of rotation of the holding table 18. The workpiece 11 is then ground with the grinding stone 48 to form a second arc-shaped groove 11c on the back surface 11b of the workpiece 11. The third and subsequent grooves 11c are then formed in the same manner.

Figure 4(B) is a plan view of a workpiece 11 having multiple grooves 11c formed thereon. For example, after forming the first groove 11c, if the step of rotating the holding table 18 90° and grinding the workpiece 11 with the grinding stone 48 is repeated three times, four arc-shaped grooves 11c will be formed on the back surface 11b of the workpiece 11, as shown in Figure 4(B). In this way, by grinding the workpiece 11 at different angles in the rotational direction of the holding table 18, multiple grooves 11c can be formed on the workpiece 11.

Next, the workpiece 11 is ground until the thickness of the workpiece 11 reaches the finished product thickness (grinding step). Figure 5(A) is a front view of the grinding device 2 showing the grinding step.

During the grinding step, the holding table 18 is rotated at a predetermined rotational speed by the rotary drive source 20 (see Figure 2 ), and the grinding wheel 44a is rotated at a predetermined rotational speed by the rotary drive source 40 (see Figure 1 ). The grinding stone 48 of the grinding wheel 44a rotates until it overlaps the center of the workpiece 11 . The grinding feed unit 24a then lowers the grinding wheel 44a at a predetermined speed (grinding feed), bringing the rotating grinding stone 48 into contact with the surface of the workpiece 11 where the groove 11c is formed (the back surface 11b).

As the grinding wheel 44a is lowered while the grinding stone 48 contacts the back side 11b of the workpiece 11, the back side 11b of the workpiece 11 is ground by the grinding stone 48. Furthermore, the lowering speed of the grinding wheel 44a is adjusted so that the grinding stone 48 is pressed against the back side 11b of the workpiece 11 with an appropriate force.

Figure 5(B) is a plan view of the holding table 18 and grinding wheel 44a during the grinding step. When the holding table 18 and grinding wheel 44a rotate to grind the workpiece 11, the entire back surface 11b of the workpiece 11 is ground, thinning the workpiece 11.

Figure 6 is an enlarged cross-sectional view of a portion of the workpiece 11 being ground by the grinding stones 48. During grinding of the workpiece 11, the multiple grinding stones 48 contact the workpiece 11 from its outer periphery toward its center. Furthermore, as the rotating grinding stones 48 pass through the grooves 11c, the lower surfaces of the grinding stones 48 collide with the inner walls of the grooves 11c, facilitating wear of the bonding material of the grinding stones 48. This promotes the spontaneous generation of abrasive grains embedded within the bonding material, thereby suppressing any degradation of the grinding performance of the grinding stones 48.

In particular, if a thin film, such as an oxide film, forms on the back surface 11b of the workpiece 11, the grinding stone 48 can be caught in the film and easily fall off the bonding material. However, as described above, the groove 11c promotes the self-sharpening of the grinding stone 48, allowing the grinding performance of the grinding stone 48 to be quickly restored.

When the workpiece 11 reaches a predetermined thickness (the finished product thickness), the grinding wheel 44a stops grinding the workpiece 11. This completes the rough grinding of the workpiece 11. Figure 7 is a plan view of the workpiece 11 after grinding. Grinding marks (saw marks) 11d remain on the back surface 11b of the workpiece 11 after grinding, extending radially from the center toward the periphery. These grinding marks 11d are formed in a curved pattern along the trajectory of the rotating grinding stone 48.

Furthermore, while the grinding wheel 44a is grinding the workpiece 11, the thickness of the workpiece 11 can be measured using a thickness gauge 50 (see FIG. 1 ). The timing for stopping the grinding of the workpiece 11 by the grinding unit 34a can then be controlled based on the thickness of the workpiece 11 measured by the thickness gauge 50.

Next, the turntable 16 is rotated to position the holding table 18 holding the workpiece 11 at the second grinding position C. The grinding unit 34b then grinds the workpiece 11 held by the holding table 18 at the second grinding position C. This allows for finish grinding of the workpiece 11 and removes the grinding marks 11d (see Figure 7) formed on the back surface 11b of the workpiece 11.

The movements of the holding table 18 and grinding unit 34b during fine grinding are the same as those during rough grinding. Furthermore, while the workpiece 11 is being ground by the grinding wheel 44b, the thickness of the workpiece 11 can be measured using the thickness gauge 50.

Furthermore, the aforementioned groove forming and grinding steps can also be performed during finish grinding. Specifically, with the holding table 18 not rotating and the grinding wheel 44b rotating, the grinding stone 48 is first brought into contact with the workpiece 11, forming a groove 11c on the back surface 11b of the workpiece 11 (see Figures 3(A) and 3(B)). Subsequently, with the holding table 18 and grinding wheel 44b rotating, the grinding stone 48 is brought into contact with the workpiece 11, grinding the entire back surface 11b of the workpiece 11 (see Figures 5(A) and 5(B)). This facilitates the self-sharpening of the grinding stone 48 during finish grinding of the workpiece 11.

Next, the turntable 16 is rotated to position the holding table 18 holding the workpiece 11 at the transfer position A. The processed workpiece 11 is then transferred from the holding table 18 positioned at the transfer position A.

The workpiece 11 held by the holding table 18 at the transfer position A is transferred from the holding table 18 to the cleaning unit 56 by the transfer unit 54 for cleaning. After cleaning by the cleaning unit 56, the workpiece 11 is then transferred by the transfer unit 6 to the cassette 10b.

As described above, the workpiece grinding method of this embodiment includes: a groove forming step of forming an arcuate groove 11c in the workpiece 11, the groove 11c not reaching the finished thickness; and a grinding step of bringing the grinding stone 48 into contact with the surface of the workpiece 11 where the groove 11c is formed, and grinding the workpiece 11 until the thickness of the workpiece 11 reaches the finished thickness. As the workpiece 11 is ground and thinned, the grinding stone 48 impacts the groove 11c, promoting self-sharpening. As a result, the grinding performance of the grinding stone 48 is maintained, suppressing the occurrence of machining defects.

Furthermore, the operation of the grinding device 2 during the aforementioned groove forming and grinding steps can be controlled by the control unit 58. Specifically, during the groove forming step, the control unit 58 outputs a control signal to the rotation drive source 20 (see FIG. 2 , etc.) to set the rotation angle of the holding table 18 to a predetermined angle, and then maintains the holding table 18 in a stopped state (non-rotating state). Furthermore, the control unit 58 outputs a control signal to the rotation drive source 40 of the grinding unit 34a to rotate the grinding wheel 44a at a predetermined number of revolutions.

The control unit 58 then outputs a control signal to the pulse motor 32 of the grinding feed unit 24a, rotating the ball screw 30 at a predetermined speed. This causes the grinding unit 34a to descend at a predetermined speed, bringing the grinding stone 48 into contact with the workpiece 11 and forming a groove 11c in the workpiece 11. In other words, the control unit 58 outputs a control signal to the components of the grinding device 2, causing the grinding device 2 to operate in the mode (first mode) for performing the groove forming step.

Meanwhile, during the grinding step, the control unit 58 outputs a control signal to the rotation drive source 20 (see FIG. 2 , etc.), causing the holding table 18 to rotate at a predetermined rotational speed. Furthermore, the control unit 58 outputs a control signal to the rotation drive source 40 of the grinding unit 34a, causing the grinding wheel 44a to rotate at a predetermined rotational speed.

The control unit 58 then outputs a control signal to the pulse motor 32 of the grinding feed unit 24a, rotating the ball screw 30 at a predetermined speed. This causes the grinding unit 34a to descend at a predetermined speed, bringing the grinding stone 48 into contact with the workpiece 11 and grinding the entire back surface 11b of the workpiece 11. In other words, the control unit 58 outputs control signals to the components of the grinding device 2, causing the grinding device 2 to operate in the mode (second mode) for performing the grinding step.

As described above, after positioning the holding table 18 holding the workpiece 11 at the first grinding position B, the control unit 58 can appropriately switch between the first mode and the second mode to perform the groove forming step and the grinding step. Furthermore, the operation of the control unit 58 is similar when the grinding unit 34b is used to perform the groove forming step and the grinding step.

When forming multiple grooves 11c during the groove forming step (see Figure 4(B)), the control unit 58 outputs a control signal to the rotary drive source 20 (see Figure 2), causing the holding table 18 to stop at predetermined angle intervals (e.g., 90° intervals). The grinding unit 34a then grinds the workpiece 11 while the holding table 18 is held at different angles, forming the grooves 11c.

Furthermore, the control unit 58 controls the angle at which the table 18 is held based on signals input from an encoder included in the rotary drive source 20. Specifically, the encoder detects the rotation angle of the output shaft of the rotary drive source 20 and outputs this information to the control unit 58. Based on the encoder's detection results, the control unit 58 calculates the amount of rotation of the output shaft of the rotary drive source 20 required to stop the table 18 at the desired angle and rotates the output shaft of the rotary drive source 20 by that amount.

In addition, the structures and methods of the above-mentioned embodiments may be appropriately modified and implemented without departing from the purpose of the present invention.

2: Grinding device

11: Workpiece

11a: Front (Side 1)

11b: Back (Side 2)

11c: Groove

18: Maintaining the workbench (work clamp)

18a: Maintaining the surface

20: Rotational drive source

34a: Grinding unit

38: Main axis

42: Mounting seat

44a: Grinding wheel

46:Abutment

48: Grinding Stone

Claims (5)

A method for grinding a workpiece comprises grinding the workpiece using a grinding device, the grinding device comprising: a holding table for holding the workpiece with a holding surface; and a grinding unit for grinding the workpiece held by the holding table using a grinding wheel having a plurality of grinding stones arranged in a ring. The method for grinding the workpiece is characterized by comprising the following steps: a groove forming step, wherein, while the holding table is not rotated and the grinding wheel is rotated, the grinding stones are brought into contact with the workpiece to grind the workpiece, thereby forming an arc-shaped groove in the workpiece having a depth that does not reach the thickness of the finished product; and The grinding step involves rotating the holding table and the grinding wheel, bringing the grinding stone into contact with the surface of the workpiece where the groove is formed, and grinding the workpiece until the thickness of the workpiece reaches the thickness of the finished product. A method for grinding a workpiece as claimed in claim 1, wherein in the groove forming step, the angle in the rotation direction of the holding table is set to a predetermined angle. A method for grinding a workpiece as claimed in claim 1 or 2, wherein in the groove forming step, the workpiece is ground separately at different angles in the rotation direction of the holding table, thereby forming a plurality of grooves in the workpiece. A grinding device comprises: a holding table for holding a workpiece with a holding surface; a grinding unit for grinding the workpiece held by the holding table using a grinding wheel having a plurality of grinding stones arranged in a ring; a grinding feed unit for moving the holding table and the grinding unit relative to each other in a direction perpendicular to the holding surface; and a control unit for controlling the holding table, the grinding unit, and the grinding feed unit. The grinding device is characterized in that the control unit can switch between a first mode and a second mode. In the first mode, the grinding wheel is rotated while the holding table is not rotated, and the grinding feed unit brings the grinding stone into contact with the workpiece, thereby forming a groove in the workpiece that does not reach the thickness of the finished product. In the second mode, the grinding wheel is rotated while the holding table and the grinding wheel are rotated, and the grinding feed unit brings the grinding stone into contact with the surface of the workpiece where the groove is formed, thereby grinding the workpiece until the thickness reaches the finished product thickness. A grinding device as claimed in claim 4, wherein the control unit can control the angle in the rotation direction of the holding worktable.